Nonperturbative QCD Coupling and its $$\\beta$$-function from Light-Front Holography

DOE PAGES

Brodskey, Stanley J.; de Teramond, Guy; Deur, Alexandre P.

2010-05-28

The light-front holographic mapping of classical gravity in AdS space, modified by a positive-sign dilaton background, leads to a non-perturbative effective couplingmore » $$\\alpha_s^{AdS}(Q^2)$$. It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale $$ \\sim 1$$ GeV. The resulting $$\\beta$$-function appears to capture the essential characteristics of the full $$\\beta$$-function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on $$\\alpha_s^{AdS}(Q^2)$$.« less

Advances in Light-Front QCD: Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.

A remarkable feature of QCD is that the mass scalemore » $k$ which controls color confinement and light-quark hadron mass scales does not appear explicitly in the QCD Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ 4ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the $$q\\bar{q}$$ invariant mass. The same result, including spin terms, is obtained using light-front holography$-$the duality between the front form and AdS 5, the space of isometries of the conformal group$-$if one modifies the action of AdS 5 by the dilaton e $κ^2z^2$ in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κκ underlying confinement and hadron masses can be connected to the parameter Λ $$\\overline{MS}$$ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s (Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q 0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the principle of maximal conformality for setting the renormalization scales, can greatly improve the precision of perturbative QCD predictions for collider phenomenology. The absence of vacuum excitations of the causal, frame-independent front-form vacuum has important consequences for the cosmological constant. In conclusion, I also discuss evidence that the antishadowing of nuclear structure functions is non-universal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with sum rules for nuclear parton distribution functions.« less

Advances in Light-Front QCD: Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra

DOE PAGES

Brodsky, Stanley J.

2017-04-19

A remarkable feature of QCD is that the mass scalemore » $k$ which controls color confinement and light-quark hadron mass scales does not appear explicitly in the QCD Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ 4ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the $$q\\bar{q}$$ invariant mass. The same result, including spin terms, is obtained using light-front holography$-$the duality between the front form and AdS 5, the space of isometries of the conformal group$-$if one modifies the action of AdS 5 by the dilaton e $κ^2z^2$ in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κκ underlying confinement and hadron masses can be connected to the parameter Λ $$\\overline{MS}$$ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s (Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q 0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the principle of maximal conformality for setting the renormalization scales, can greatly improve the precision of perturbative QCD predictions for collider phenomenology. The absence of vacuum excitations of the causal, frame-independent front-form vacuum has important consequences for the cosmological constant. In conclusion, I also discuss evidence that the antishadowing of nuclear structure functions is non-universal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with sum rules for nuclear parton distribution functions.« less

Lattice analysis for the energy scale of QCD phenomena.

PubMed

Yamamoto, Arata; Suganuma, Hideo

2008-12-12

We formulate a new framework in lattice QCD to study the relevant energy scale of QCD phenomena. By considering the Fourier transformation of link variable, we can investigate the intrinsic energy scale of a physical quantity nonperturbatively. This framework is broadly available for all lattice QCD calculations. We apply this framework for the quark-antiquark potential and meson masses in quenched lattice QCD. The gluonic energy scale relevant for the confinement is found to be less than 1 GeV in the Landau or Coulomb gauge.

Color Confinement, Hadron Dynamics, and Hadron Spectroscopy from Light-Front Holography and Superconformal Algebra

DOE PAGES

Brodsky, Stanley J.

2018-01-01

Tmore » he QCD light-front Hamiltonian equation H L F Ψ = M 2 Ψ derived from quantization at fixed LF time τ = t     +     z / c provides a causal, frame-independent method for computing hadron spectroscopy as well as dynamical observables such as structure functions, transverse momentum distributions, and distribution amplitudes. he QCD Lagrangian with zero quark mass has no explicit mass scale. de Alfaro, Fubini, and Furlan (dAFF) have made an important observation that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the dAFF procedure to the QCD light-front Hamiltonian, it leads to a color-confining potential κ 4 ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the q q ¯ invariant mass squared. he same result, including spin terms, is obtained using light-front holography, the duality between light-front dynamics and A d S 5 , if one modifies the A d S 5 action by the dilaton e κ 2 z 2 in the fifth dimension z . When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions provide a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons and a universal Regge slope. he pion q q ¯ eigenstate has zero mass at m q = 0 . he superconformal relations also can be extended to heavy-light quark mesons and baryons. his approach also leads to insights into the physics underlying hadronization at the amplitude level. I will also discuss the remarkable features of the Poincaré invariant, causal vacuum defined by light-front quantization and its impact on the interpretation of the cosmological constant. AdS/QCD also predicts the analytic form of the nonperturbative running coupling α s ( Q 2 ) ∝ e - Q 2 / 4 κ 2 . he mass scale κ underlying hadron masses can be connected to the parameter Λ M S ¯ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. he result is an effective coupling α s ( Q 2 ) defined at all momenta. One obtains empirically viable predictions for spacelike and timelike hadronic form factors, structure functions, distribution amplitudes, and transverse momentum distributions. Finally, I address the interesting question of whether the momentum sum rule is valid for nuclear structure functions.« less

Color Confinement, Hadron Dynamics, and Hadron Spectroscopy from Light-Front Holography and Superconformal Algebra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.

Tmore » he QCD light-front Hamiltonian equation H L F Ψ = M 2 Ψ derived from quantization at fixed LF time τ = t     +     z / c provides a causal, frame-independent method for computing hadron spectroscopy as well as dynamical observables such as structure functions, transverse momentum distributions, and distribution amplitudes. he QCD Lagrangian with zero quark mass has no explicit mass scale. de Alfaro, Fubini, and Furlan (dAFF) have made an important observation that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the dAFF procedure to the QCD light-front Hamiltonian, it leads to a color-confining potential κ 4 ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the q q ¯ invariant mass squared. he same result, including spin terms, is obtained using light-front holography, the duality between light-front dynamics and A d S 5 , if one modifies the A d S 5 action by the dilaton e κ 2 z 2 in the fifth dimension z . When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions provide a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons and a universal Regge slope. he pion q q ¯ eigenstate has zero mass at m q = 0 . he superconformal relations also can be extended to heavy-light quark mesons and baryons. his approach also leads to insights into the physics underlying hadronization at the amplitude level. I will also discuss the remarkable features of the Poincaré invariant, causal vacuum defined by light-front quantization and its impact on the interpretation of the cosmological constant. AdS/QCD also predicts the analytic form of the nonperturbative running coupling α s ( Q 2 ) ∝ e - Q 2 / 4 κ 2 . he mass scale κ underlying hadron masses can be connected to the parameter Λ M S ¯ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. he result is an effective coupling α s ( Q 2 ) defined at all momenta. One obtains empirically viable predictions for spacelike and timelike hadronic form factors, structure functions, distribution amplitudes, and transverse momentum distributions. Finally, I address the interesting question of whether the momentum sum rule is valid for nuclear structure functions.« less

Born-Oppenheimer approximation in an effective field theory language

NASA Astrophysics Data System (ADS)

Brambilla, Nora; Krein, Gastão; Tarrús Castellà, Jaume; Vairo, Antonio

2018-01-01

The Born-Oppenheimer approximation is the standard tool for the study of molecular systems. It is founded on the observation that the energy scale of the electron dynamics in a molecule is larger than that of the nuclei. A very similar physical picture can be used to describe QCD states containing heavy quarks as well as light-quarks or gluonic excitations. In this work, we derive the Born-Oppenheimer approximation for QED molecular systems in an effective field theory framework by sequentially integrating out degrees of freedom living at energies above the typical energy scale where the dynamics of the heavy degrees of freedom occurs. In particular, we compute the matching coefficients of the effective field theory for the case of the H2+ diatomic molecule that are relevant to compute its spectrum up to O (m α5). Ultrasoft photon loops contribute at this order, being ultimately responsible for the molecular Lamb shift. In the effective field theory the scaling of all the operators is homogeneous, which facilitates the determination of all the relevant contributions, an observation that may become useful for high-precision calculations. Using the above case as a guidance, we construct under some conditions an effective field theory for QCD states formed by a color-octet heavy quark-antiquark pair bound with a color-octet light-quark pair or excited gluonic state, highlighting the similarities and differences between the QED and QCD systems. Assuming that the multipole expansion is applicable, we construct the heavy-quark potential up to next-to-leading order in the multipole expansion in terms of nonperturbative matching coefficients to be obtained from lattice QCD.

Next-to-Next-to-Leading-Order QCD Corrections to the Transverse Momentum Distribution of Weak Gauge Bosons

NASA Astrophysics Data System (ADS)

Gehrmann-De Ridder, A.; Gehrmann, T.; Glover, E. W. N.; Huss, A.; Walker, D. M.

2018-03-01

The transverse momentum spectra of weak gauge bosons and their ratios probe the underlying dynamics and are crucial in testing our understanding of the standard model. They are an essential ingredient in precision measurements, such as the W boson mass extraction. To fully exploit the potential of the LHC data, we compute the second-order [next-to-next-to-leading-order (NNLO)] QCD corrections to the inclusive-pTW spectrum as well as to the ratios of spectra for W-/W+ and Z /W . We find that the inclusion of NNLO QCD corrections considerably improves the theoretical description of the experimental CMS data and results in a substantial reduction of the residual scale uncertainties.

Strong running coupling at τ and Z(0) mass scales from lattice QCD.

PubMed

Blossier, B; Boucaud, Ph; Brinet, M; De Soto, F; Du, X; Morenas, V; Pène, O; Petrov, K; Rodríguez-Quintero, J

2012-06-29

This Letter reports on the first computation, from data obtained in lattice QCD with u, d, s, and c quarks in the sea, of the running strong coupling via the ghost-gluon coupling renormalized in the momentum-subtraction Taylor scheme. We provide readers with estimates of α(MS[over ¯])(m(τ)(2)) and α(MS[over ¯])(m(Z)(2)) in very good agreement with experimental results. Including a dynamical c quark makes the needed running of α(MS[over ¯]) safer.

Lattice QCD with two dynamical flavors of domain wall fermions

NASA Astrophysics Data System (ADS)

Aoki, Y.; Blum, T.; Christ, N.; Dawson, C.; Hashimoto, K.; Izubuchi, T.; Laiho, J. W.; Levkova, L.; Lin, M.; Mawhinney, R.; Noaki, J.; Ohta, S.; Orginos, K.; Soni, A.

2005-12-01

We present results from the first large-scale study of two-flavor QCD using domain wall fermions (DWF), a chirally symmetric fermion formulation which has been proven to be very effective in the quenched approximation. We work on lattices of size 163×32, with a lattice cutoff of a-1≈1.7GeV and dynamical (or sea) quark masses in the range mstrange/2≲msea≲mstrange. After discussing the algorithmic and implementation issues involved in simulating dynamical DWF, we report on the low-lying hadron spectrum, decay constants, static quark potential, and the important kaon weak matrix element describing indirect CP violation in the standard model, BK. In the latter case we include the effect of nondegenerate quark masses (ms≠mu=md), finding BKM Smacr (2GeV)=0.495(18).

Light-front holography and superconformal quantum mechanics: A new approach to hadron structure and color confinement

NASA Astrophysics Data System (ADS)

Brodsky, Stanley J.; Deur, Alexandre; de Téramond, Guy F.; Dosch, Hans Günter

2015-11-01

A primary question in hadron physics is how the mass scale for hadrons consisting of light quarks, such as the proton, emerges from the QCD Lagrangian even in the limit of zero quark mass. If one requires the effective action which underlies the QCD Lagrangian to remain conformally invariant and extends the formalism of de Alfaro, Fubini and Furlan to light-front Hamiltonian theory, then a unique, color-confining potential with a mass parameter κ emerges. The actual value of the parameter κ is not set by the model - only ratios of hadron masses and other hadronic mass scales are predicted. The result is a nonperturbative, relativistic light-front quantum mechanical wave equation, the Light-Front Schrödinger Equation which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the identical slope in the radial quantum number n and orbital angular momentum L. The same light-front equations for mesons with spin J also can be derived from the holographic mapping to QCD (3+1) at fixed light-front time from the soft-wall model modification of AdS5 space with a specific dilaton profile. Light-front holography thus provides a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. One can also extend the analysis to baryons using superconformal algebra - 2 × 2 supersymmetric representations of the conformal group. The resulting fermionic LF bound-state equations predict striking similarities between the meson and baryon spectra. In fact, the holographic QCD light-front Hamiltonians for the states on the meson and baryon trajectories are identical if one shifts the internal angular momenta of the meson (LM) and baryon (LB) by one unit: LM = LB + 1. We also show how the mass scale κ underlying confinement and the masses of light-quark hadrons determines the scale ΛMS¯ controlling the evolution of the perturbative QCD coupling. The relation between scales is obtained by matching the nonperturbative dynamics, as described by an effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime. The data for the effective coupling defined from the Bjorken sum rule αg1(Q2) are remarkably consistent with the Gaussian form predicted by LF holographic QCD. The result is an effective coupling defined at all momenta. The predicted value ΛMS¯(NF=3)=0.440mρ=0.341±0.024GeV is in agreement with the world average 0.339±0.010GeV. We thus can connect ΛMS¯ to hadron masses. The analysis applies to any renormalization scheme.

The generalized scheme-independent Crewther relation in QCD

NASA Astrophysics Data System (ADS)

Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang; Brodsky, Stanley J.

2017-07-01

The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton-nucleon scattering times the Adler function, defined from the cross section for electron-positron annihilation into hadrons, has no pQCD radiative corrections. The ;Generalized Crewther Relation; relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (Dns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (CBjp) at leading twist. A scheme-dependent ΔCSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both Dns and the inverse coefficient CBjp-1 have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, αˆd (Q) =∑i≥1 αˆg1 i (Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Similar scale-fixed commensurate scale relations also connect other physical observables at their physical momentum scales, thus providing convention-independent, fundamental precision tests of QCD.

Novel QCD Phenomenology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins

2011-08-12

I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion ratio seen in high centrality heavy ion collisions. Initial-state and final-state interactions of the struck quark, the soft-gluon rescattering associated with its Wilson line, lead to Bjorken-scaling single-spinmore » asymmetries, diffractive deep inelastic scattering, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as nuclear shadowing and antishadowing. The Gribov-Glauber theory predicts that antishadowing of nuclear structure functions is not universal, but instead depends on the flavor quantum numbers of each quark and antiquark, thus explaining the anomalous nuclear dependence measured in deep-inelastic neutrino scattering. Since shadowing and antishadowing arise from the physics of leading-twist diffractive deep inelastic scattering, one cannot attribute such phenomena to the structure of the nucleus itself. It is thus important to distinguish 'static' structure functions, the probability distributions computed from the square of the target light-front wavefunctions, versus 'dynamical' structure functions which include the effects of the final-state rescattering of the struck quark. The importance of the J = 0 photon-quark QCD contact interaction in deeply virtual Compton scattering is also emphasized. The scheme-independent BLM method for setting the renormalization scale is discussed. Eliminating the renormalization scale ambiguity greatly improves the precision of QCD predictions and increases the sensitivity of searches for new physics at the LHC. Other novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates.« less

One-loop QCD thermodynamics in a strong homogeneous and static magnetic field

NASA Astrophysics Data System (ADS)

Rath, Shubhalaxmi; Patra, Binoy Krishna

2017-12-01

We have studied how the equation of state of thermal QCD with two light flavors is modified in a strong magnetic field. We calculate the thermodynamic observables of hot QCD matter up to one-loop, where the magnetic field affects mainly the quark contribution and the gluon part is largely unaffected except for the softening of the screening mass. We have first calculated the pressure of a thermal QCD medium in a strong magnetic field, where the pressure at fixed temperature increases with the magnetic field faster than the increase with the temperature at constant magnetic field. This can be understood from the dominant scale of thermal medium in the strong magnetic field, being the magnetic field, in the same way that the temperature dominates in a thermal medium in the absence of magnetic field. Thus although the presence of a strong magnetic field makes the pressure of hot QCD medium larger, the dependence of pressure on the temperature becomes less steep. Consistent with the above observations, the entropy density is found to decrease with the temperature in the presence of a strong magnetic field which is again consistent with the fact that the strong magnetic field restricts the dynamics of quarks to two dimensions, hence the phase space becomes squeezed resulting in the reduction of number of microstates. Moreover the energy density is seen to decrease and the speed of sound of thermal QCD medium increases in the presence of a strong magnetic field. These findings could have phenomenological implications in heavy ion collisions because the expansion dynamics of the medium produced in non-central ultra-relativistic heavy ion collisions is effectively controlled by both the energy density and the speed of sound.

The generalized scheme-independent Crewther relation in QCD

DOE PAGES

Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang; ...

2017-05-10

The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton–nucleon scattering times the Adler function, defined from the cross section for electron–positron annihilation into hadrons, has no pQCD radiative corrections. The “Generalized Crewther Relation” relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (D ns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (C Bjp) at leading twist. A scheme-dependent Δ CSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both D ns and the inverse coefficient Cmore » $$-1\\atop{Bjp}$$ have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, $$\\hat{α}$$ d(Q)=Σ i≥1$$\\hat{α}^i\\atop{g1}$$(Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Lastly, similar scale-fixed commensurate scale relations also connect other physical observables at their physical momentum scales, thus providing convention-independent, fundamental precision tests of QCD.« less

The generalized scheme-independent Crewther relation in QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang

The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton–nucleon scattering times the Adler function, defined from the cross section for electron–positron annihilation into hadrons, has no pQCD radiative corrections. The “Generalized Crewther Relation” relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (D ns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (C Bjp) at leading twist. A scheme-dependent Δ CSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both D ns and the inverse coefficient Cmore » $$-1\\atop{Bjp}$$ have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, $$\\hat{α}$$ d(Q)=Σ i≥1$$\\hat{α}^i\\atop{g1}$$(Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Lastly, similar scale-fixed commensurate scale relations also connect other physical observables at their physical momentum scales, thus providing convention-independent, fundamental precision tests of QCD.« less

Renormalization scheme dependence of high-order perturbative QCD predictions

NASA Astrophysics Data System (ADS)

Ma, Yang; Wu, Xing-Gang

2018-02-01

Conventionally, one adopts typical momentum flow of a physical observable as the renormalization scale for its perturbative QCD (pQCD) approximant. This simple treatment leads to renormalization scheme-and-scale ambiguities due to the renormalization scheme and scale dependence of the strong coupling and the perturbative coefficients do not exactly cancel at any fixed order. It is believed that those ambiguities will be softened by including more higher-order terms. In the paper, to show how the renormalization scheme dependence changes when more loop terms have been included, we discuss the sensitivity of pQCD prediction on the scheme parameters by using the scheme-dependent {βm ≥2}-terms. We adopt two four-loop examples, e+e-→hadrons and τ decays into hadrons, for detailed analysis. Our results show that under the conventional scale setting, by including more-and-more loop terms, the scheme dependence of the pQCD prediction cannot be reduced as efficiently as that of the scale dependence. Thus a proper scale-setting approach should be important to reduce the scheme dependence. We observe that the principle of minimum sensitivity could be such a scale-setting approach, which provides a practical way to achieve optimal scheme and scale by requiring the pQCD approximate be independent to the "unphysical" theoretical conventions.

New Perspectives for Hadron Phenomenology:The Effects of Final-State Interactions and Near-Conformal Effective QCD Couplings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, S

2003-10-24

The effective QCD charge extracted from {tau} decay is remarkably constant at small momenta, implying the near-conformal behavior of hadronic interactions at small momentum transfer. The correspondence of large-N{sub c} supergravity theory in higher-dimensional anti-de Sitter spaces with gauge theory in physical space-time also has interesting implications for hadron phenomenology in the conformal limit, such as constituent counting rules for hard exclusive processes. The utility of light-front quantization and lightfront Fock wavefunctions for analyzing such phenomena and representing the dynamics of QCD bound states is reviewed. I also discuss the novel effects of initial- and final-state interactions in hard QCDmore » inclusive processes, including Bjorken-scaling single-spin asymmetries and the leading-twist diffractive and shadowing contributions to deep inelastic lepton-proton scattering.« less

On the interface between perturbative and nonperturbative QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deur, Alexandre; Brodsky, Stanley J.; de Teramond, Guy F.

2016-04-04

The QCD running couplingmore » $$\\alpha_s(Q^2)$$ sets the strength of the interactions of quarks and gluons as a function of the momentum transfer $Q$. The $Q^2$ dependence of the coupling is required to describe hadronic interactions at both large and short distances. In this article we adopt the light-front holographic approach to strongly-coupled QCD, a formalism which incorporates confinement, predicts the spectroscopy of hadrons composed of light quarks, and describes the low-$Q^2$ analytic behavior of the strong coupling $$\\alpha_s(Q^2)$$. The high-$Q^2$ dependence of the coupling $$\\alpha_s(Q^2)$$ is specified by perturbative QCD and its renormalization group equation. The matching of the high and low $Q^2$ regimes of $$\\alpha_s(Q^2)$$ then determines the scale $$Q_0$$ which sets the interface between perturbative and nonperturbative hadron dynamics. The value of $$Q_0$$ can be used to set the factorization scale for DGLAP evolution of hadronic structure functions and the ERBL evolution of distribution amplitudes. We discuss the scheme-dependence of the value of $$Q_0$$ and the infrared fixed-point of the QCD coupling. Our analysis is carried out for the $$\\bar{MS}$$, $$g_1$$, $MOM$ and $V$ renormalization schemes. Our results show that the discrepancies on the value of $$\\alpha_s$$ at large distance seen in the literature can be explained by different choices of renormalization schemes. Lastly, we also provide the formulae to compute $$\\alpha_s(Q^2)$$ over the entire range of space-like momentum transfer for the different renormalization schemes discussed in this article.« less

Better than $l/Mflops sustained: a scalable PC-based parallel computer for lattice QCD

NASA Astrophysics Data System (ADS)

Fodor, Zoltán; Katz, Sándor D.; Papp, Gábor

2003-05-01

We study the feasibility of a PC-based parallel computer for medium to large scale lattice QCD simulations. The Eötvös Univ., Inst. Theor. Phys. cluster consists of 137 Intel P4-1.7GHz nodes with 512 MB RDRAM. The 32-bit, single precision sustained performance for dynamical QCD without communication is 1510 Mflops/node with Wilson and 970 Mflops/node with staggered fermions. This gives a total performance of 208 Gflops for Wilson and 133 Gflops for staggered QCD, respectively (for 64-bit applications the performance is approximately halved). The novel feature of our system is its communication architecture. In order to have a scalable, cost-effective machine we use Gigabit Ethernet cards for nearest-neighbor communications in a two-dimensional mesh. This type of communication is cost effective (only 30% of the hardware costs is spent on the communication). According to our benchmark measurements this type of communication results in around 40% communication time fraction for lattices upto 48 3·96 in full QCD simulations. The price/sustained-performance ratio for full QCD is better than l/Mflops for Wilson (and around 1.5/Mflops for staggered) quarks for practically any lattice size, which can fit in our parallel computer. The communication software is freely available upon request for non-profit organizations.

Opening up the QCD axion window

NASA Astrophysics Data System (ADS)

Agrawal, Prateek; Marques-Tavares, Gustavo; Xue, Wei

2018-03-01

We present a new mechanism to deplete the energy density of the QCD axion, making decay constants as high as f a ≃ 1017 GeV viable for generic initial conditions. In our setup, the axion couples to a massless dark photon with a coupling that is moderately stronger than the axion coupling to gluons. Dark photons are produced copiously through a tachyonic instability when the axion field starts oscillating, and an exponential suppression of the axion density can be achieved. For a large part of the parameter space this dark radiation component of the universe can be observable in upcoming CMB experiments. Such dynamical depletion of the axion density ameliorates the isocurvature bound on the scale of inflation. The depletion also amplifies the power spectrum at scales that enter the horizon before particle production begins, potentially leading to axion miniclusters.

Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra and other Advances in Light-Front QCD

DOE PAGES

Brodsky, Stanley J.

2018-03-06

Here, light-front holography, together with superconformal algebra, have provided new insights into the physics of color confinement and the spectroscopy and dynamics of hadrons. As shown by de Alfaro, Fubini and Furlan, a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the procedure of de Alfaro et al. to the frame-independent light-front Hamiltonian, it leads uniquely to a confining qq¯ potential κ 4ζ 2, where ζ 2 is the light-frontmore » radial variable related in momentum space to the qq¯ invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS 5, the space of isometries of the conformal group—if one modifies the action of AdS 5 by the dilaton e κ2 z2 in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions lead to a a unified Regge spectroscopy of meson, baryon, and tetraquarks, including supersymmetric relations between their masses and their wavefunctions. One also predicts hadronic light-front wavefunctions and observables such as structure functions, transverse momentum distributions, and the distribution amplitudes. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ MS¯ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s(Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. I also discuss a number of applications of light-front phenomenology.« less

Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra and other Advances in Light-Front QCD

NASA Astrophysics Data System (ADS)

Brodsky, Stanley J.

2018-05-01

Light-front holography, together with superconformal algebra, have provided new insights into the physics of color confinement and the spectroscopy and dynamics of hadrons. As shown by de Alfaro, Fubini and Furlan, a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the procedure of de Alfaro et al. to the frame-independent light-front Hamiltonian, it leads uniquely to a confining q \\bar{q} potential κ ^4 ζ ^2, where ζ ^2 is the light-front radial variable related in momentum space to the q \\bar{q} invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS_5, the space of isometries of the conformal group—if one modifies the action of AdS_5 by the dilaton e^{κ ^2 z^2} in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions lead to a a unified Regge spectroscopy of meson, baryon, and tetraquarks, including supersymmetric relations between their masses and their wavefunctions. One also predicts hadronic light-front wavefunctions and observables such as structure functions, transverse momentum distributions, and the distribution amplitudes. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ_{\\overline{MS}} in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α _s(Q^2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q_0 which sets the interface between perturbative and nonperturbative hadron dynamics. I also discuss a number of applications of light-front phenomenology.

Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra and other Advances in Light-Front QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.

Here, light-front holography, together with superconformal algebra, have provided new insights into the physics of color confinement and the spectroscopy and dynamics of hadrons. As shown by de Alfaro, Fubini and Furlan, a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the procedure of de Alfaro et al. to the frame-independent light-front Hamiltonian, it leads uniquely to a confining qq¯ potential κ 4ζ 2, where ζ 2 is the light-frontmore » radial variable related in momentum space to the qq¯ invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS 5, the space of isometries of the conformal group—if one modifies the action of AdS 5 by the dilaton e κ2 z2 in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions lead to a a unified Regge spectroscopy of meson, baryon, and tetraquarks, including supersymmetric relations between their masses and their wavefunctions. One also predicts hadronic light-front wavefunctions and observables such as structure functions, transverse momentum distributions, and the distribution amplitudes. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ MS¯ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s(Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. I also discuss a number of applications of light-front phenomenology.« less

High-scale axions without isocurvature from inflationary dynamics

DOE PAGES

Kearney, John; Orlofsky, Nicholas; Pierce, Aaron

2016-05-31

Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation H I. If the scale of Peccei-Quinn (PQ) breaking f a is greater than H I/2π, CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation f I require either late-time dilution of the axion abundance or highlymore » super-Planckian f I that somehow does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow f a close to the Planck scale. Lastly, avoiding disruption of inflationary dynamics provides important limits on the parameter space.« less

Cosmological perturbations of axion with a dynamical decay constant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Takeshi; INFN, Sezione di Trieste,Via Bonomea 265, 34136 Trieste; Takahashi, Fuminobu

2016-08-25

A QCD axion with a time-dependent decay constant has been known to be able to accommodate high-scale inflation without producing topological defects or too large isocurvature perturbations on CMB scales. We point out that a dynamical decay constant also has the effect of enhancing the small-scale axion isocurvature perturbations. The enhanced axion perturbations can even exceed the periodicity of the axion potential, and thus lead to the formation of axionic domain walls. Unlike the well-studied axionic walls, the walls produced from the enhanced perturbations are not bounded by cosmic strings, and thus would overclose the universe independently of the numbermore » of degenerate vacua along the axion potential.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anand, Sampurn; Mohanty, Subhendra; Dey, Ujjal Kumar, E-mail: sampurn@prl.res.in, E-mail: ujjal@cts.iitkgp.ernet.in, E-mail: mohanty@prl.res.in

Cosmological phase transitions can be a source of Stochastic Gravitational Wave (SGW) background. Apart from the dynamics of the phase transition, the characteristic frequency and the fractional energy density Ω{sub gw} of the SGW depends upon the temperature of the transition. In this article, we compute the SGW spectrum in the light of QCD equation of state provided by the lattice results. We find that the inclusion of trace anomaly from lattice QCD, enhances the SGW signal generated during QCD phase transition by ∼ 50% and the peak frequency of the QCD era SGW are shifted higher by ∼ 25%more » as compared to the earlier estimates without trace anomaly. This result is extremely significant for testing the phase transition dynamics near QCD epoch.« less

Pion distribution amplitude from lattice QCD.

PubMed

Cloët, I C; Chang, L; Roberts, C D; Schmidt, S M; Tandy, P C

2013-08-30

A method is explained through which a pointwise accurate approximation to the pion's valence-quark distribution amplitude (PDA) may be obtained from a limited number of moments. In connection with the single nontrivial moment accessible in contemporary simulations of lattice-regularized QCD, the method yields a PDA that is a broad concave function whose pointwise form agrees with that predicted by Dyson-Schwinger equation analyses of the pion. Under leading-order evolution, the PDA remains broad to energy scales in excess of 100 GeV, a feature which signals persistence of the influence of dynamical chiral symmetry breaking. Consequently, the asymptotic distribution φπ(asy)(x) is a poor approximation to the pion's PDA at all such scales that are either currently accessible or foreseeable in experiments on pion elastic and transition form factors. Thus, related expectations based on φ φπ(asy)(x) should be revised.

Scale dependencies of proton spin constituents with a nonperturbative αs

NASA Astrophysics Data System (ADS)

Jia, Shaoyang; Huang, Feng

2012-11-01

By introducing the contribution from dynamically generated gluon mass, we present a brand new parametrized form of QCD beta function to get an inferred limited running behavior of QCD coupling constant αs. This parametrized form is regarded as an essential factor to determine the scale dependencies of the proton spin constituents at the very low scale. In order to compare with experimental results directly, we work within the gauge-invariant framework to decompose the proton spin. Utilizing the updated next-to-next-leading-order evolution equations for angular momentum observables within a modified minimal subtraction scheme, we indicate that gluon contribution to proton spin cannot be ignored. Specifically, by assuming asymptotic limits of the total quark/gluon angular momentum valid, respectively, the scale dependencies of quark angular momentum Jq and gluon angular momentum Jg down to Q2˜1GeV2 are presented, which are comparable with the preliminary analysis of deeply virtual Compton scattering experiments by HERMES and JLab. After solving scale dependencies of quark spin ΔΣq, orbital angular momenta of quarks Lq are given by subtraction, presenting a holistic picture of proton spin partition within up and down quarks at a low scale.

Conformal Aspects of QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, S

2003-11-19

Theoretical and phenomenological evidence is now accumulating that the QCD coupling becomes constant at small virtuality; i.e., {alpha}{sub s}(Q{sup 2}) develops an infrared fixed point in contradiction to the usual assumption of singular growth in the infrared. For example, the hadronic decays of the {tau} lepton can be used to determine the effective charge {alpha}{sub {tau}}(m{sub {tau}{prime}}{sup 2}) for a hypothetical {tau}-lepton with mass in the range 0 < m{sub {tau}{prime}} < m{sub {tau}}. The {tau} decay data at low mass scales indicates that the effective charge freezes at a value of s = m{sub {tau}{prime}}{sup 2} of order 1more » GeV{sup 2} with a magnitude {alpha}{sub {tau}} {approx} 0.9 {+-} 0.1. The near-constant behavior of effective couplings suggests that QCD can be approximated as a conformal theory even at relatively small momentum transfer and why there are no significant running coupling corrections to quark counting rules for exclusive processes. The AdS/CFT correspondence of large N{sub c} supergravity theory in higher-dimensional anti-de Sitter space with supersymmetric QCD in 4-dimensional space-time also has interesting implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for exclusive processes and light-front wavefunctions. The utility of light-front quantization and light-front Fock wavefunctions for analyzing nonperturbative QCD and representing the dynamics of QCD bound states is also discussed.« less

Setting the renormalization scale in pQCD: Comparisons of the principle of maximum conformality with the sequential extended Brodsky-Lepage-Mackenzie approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Hong -Hao; Wu, Xing -Gang; Ma, Yang

A key problem in making precise perturbative QCD (pQCD) predictions is how to set the renormalization scale of the running coupling unambiguously at each finite order. The elimination of the uncertainty in setting the renormalization scale in pQCD will greatly increase the precision of collider tests of the Standard Model and the sensitivity to new phenomena. Renormalization group invariance requires that predictions for observables must also be independent on the choice of the renormalization scheme. The well-known Brodsky-Lepage-Mackenzie (BLM) approach cannot be easily extended beyond next-to-next-to-leading order of pQCD. Several suggestions have been proposed to extend the BLM approach tomore » all orders. In this paper we discuss two distinct methods. One is based on the “Principle of Maximum Conformality” (PMC), which provides a systematic all-orders method to eliminate the scale and scheme ambiguities of pQCD. The PMC extends the BLM procedure to all orders using renormalization group methods; as an outcome, it significantly improves the pQCD convergence by eliminating renormalon divergences. An alternative method is the “sequential extended BLM” (seBLM) approach, which has been primarily designed to improve the convergence of pQCD series. The seBLM, as originally proposed, introduces auxiliary fields and follows the pattern of the β0-expansion to fix the renormalization scale. However, the seBLM requires a recomputation of pQCD amplitudes including the auxiliary fields; due to the limited availability of calculations using these auxiliary fields, the seBLM has only been applied to a few processes at low orders. In order to avoid the complications of adding extra fields, we propose a modified version of seBLM which allows us to apply this method to higher orders. As a result, we then perform detailed numerical comparisons of the two alternative scale-setting approaches by investigating their predictions for the annihilation cross section ratio R e+e– at four-loop order in pQCD.« less

Dynamical clockwork axions

NASA Astrophysics Data System (ADS)

Coy, Rupert; Frigerio, Michele; Ibe, Masahiro

2017-10-01

The clockwork mechanism is a novel method for generating a large separation between the dynamical scale and interaction scale of a theory. We demonstrate how the mechanism can arise from a sequence of strongly-coupled sectors. This framework avoids elementary scalar fields as well as ad hoc continuous global symmetries, both of which are subject to serious stability issues. The clockwork factor, q, is determined by the consistency of the strong dynamics. The preserved global U(1) of the clockwork appears as an accidental symmetry, resulting from discrete or U(1) gauge symmetries, and it is spontaneously broken by the chiral condensates. We apply such a dynamical clockwork to construct models with an effectively invisible QCD axion from TeV-scale strong dynamics. The axion couplings are determined by the localisation of the Standard Model interactions along the clockwork sequence. The TeV spectrum includes either coloured hadrons or vector-like quarks. Dark matter can be accounted for by the axion or the lightest neutral baryons, which are accidentally stable.

Hadronic and nuclear interactions in QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

Despite the evidence that QCD - or something close to it - gives a correct description of the structure of hadrons and their interactions, it seems paradoxical that the theory has thus far had very little impact in nuclear physics. One reason for this is that the application of QCD to distances larger than 1 fm involves coherent, non-perturbative dynamics which is beyond present calculational techniques. For example, in QCD the nuclear force can evidently be ascribed to quark interchange and gluon exchange processes. These, however, are as complicated to analyze from a fundamental point of view as is themore » analogous covalent bond in molecular physics. Since a detailed description of quark-quark interactions and the structure of hadronic wavefunctions is not yet well-understood in QCD, it is evident that a quantitative first-principle description of the nuclear force will require a great deal of theoretical effort. Another reason for the limited impact of QCD in nuclear physics has been the conventional assumption that nuclear interactions can for the most part be analyzed in terms of an effective meson-nucleon field theory or potential model in isolation from the details of short distance quark and gluon structure of hadrons. These lectures, argue that this view is untenable: in fact, there is no correspondence principle which yields traditional nuclear physics as a rigorous large-distance or non-relativistic limit of QCD dynamics. On the other hand, the distinctions between standard nuclear physics dynamics and QCD at nuclear dimensions are extremely interesting and illuminating for both particle and nuclear physics.« less

Instanton dominance over αs at low momenta from lattice QCD simulations at Nf = 0, Nf = 2 + 1 and Nf = 2 + 1 + 1

NASA Astrophysics Data System (ADS)

Athenodorou, Andreas; Boucaud, Philippe; de Soto, Feliciano; Rodríguez-Quintero, José; Zafeiropoulos, Savvas

2018-03-01

We report on an instanton-based analysis of the gluon Green functions in the Landau gauge for low momenta; in particular we use lattice results for αs in the symmetric momentum subtraction scheme (MOM) for large-volume lattice simulations. We have exploited quenched gauge field configurations, Nf = 0, with both Wilson and tree-level Symanzik improved actions, and unquenched ones with Nf = 2 + 1 and Nf = 2 + 1 + 1 dynamical flavors (domain wall and twisted-mass fermions, respectively). We show that the dominance of instanton correlations on the low-momenta gluon Green functions can be applied to the determination of phenomenological parameters of the instanton liquid and, eventually, to a determination of the lattice spacing. We furthermore apply the Gradient Flow to remove short-distance fluctuations. The Gradient Flow gets rid of the QCD scale, ΛQCD, and reveals that the instanton prediction extents to large momenta. For those gauge field configurations free of quantum fluctuations, the direct study of topological charge density shows the appearance of large-scale lumps that can be identified as instantons, giving access to a direct study of the instanton density and size distribution that is compatible with those extracted from the analysis of the Green functions.

The International Conference on Vector and Parallel Computing (2nd)

DTIC Science & Technology

1989-01-17

Computation of the SVD of Bidiagonal Matrices" ...................................... 11 " Lattice QCD -As a Large Scale Scientific Computation...vectorizcd for the IBM 3090 Vector Facility. In addition, elapsed times " Lattice QCD -As a Large Scale Scientific have been reduced by using 3090...benchmarked Lattice QCD on a large number ofcompu- come from the wavefront solver routine. This was exten- ters: CrayX-MP and Cray 2 (vector

Dyonic Flux Tube Structure of Nonperturbative QCD Vacuum

NASA Astrophysics Data System (ADS)

Chandola, H. C.; Pandey, H. C.

We study the flux tube structure of the nonperturbative QCD vacuum in terms of its dyonic excitations by using an infrared effective Lagrangian and show that the dyonic condensation of QCD vacuum has a close connection with the process of color confinement. Using the fiber bundle formulation of QCD, the magnetic symmetry condition is presented in a gauge covariant form and the gauge potential has been constructed in terms of the magnetic vectors on global sections. The dynamical breaking of the magnetic symmetry has been shown to lead the dyonic condensation of QCD vacuum in the infrared energy sector. Deriving the asymptotic solutions of the field equations in the dynamically broken phase, the dyonic flux tube structure of QCD vacuum is explored which has been shown to lead the confinement parameters in terms of the vector and scalar mass modes of the condensed vacuum. Evaluating the charge quantum numbers and energy associated with the dyonic flux tube solutions, the effect of electric excitation of monopole is analyzed using the Regge slope parameter (as an input parameter) and an enhancement in the dyonic pair correlations and the confining properties of QCD vacuum in its dyonically condensed mode has been demonstrated.

Complex Langevin dynamics and zeroes of the fermion determinant

NASA Astrophysics Data System (ADS)

Aarts, Gert; Seiler, Erhard; Sexty, Dénes; Stamatescu, Ion-Olimpiu

2017-05-01

QCD at nonzero baryon chemical potential suffers from the sign problem, due to the complex quark determinant. Complex Langevin dynamics can provide a solution, provided certain conditions are met. One of these conditions, holomorphicity of the Langevin drift, is absent in QCD since zeroes of the determinant result in a meromorphic drift. We first derive how poles in the drift affect the formal justification of the approach and then explore the various possibilities in simple models. The lessons from these are subsequently applied to both heavy dense QCD and full QCD, and we find that the results obtained show a consistent picture. We conclude that with careful monitoring, the method can be justified a posteriori, even in the presence of meromorphicity.

Light-front holographic QCD and emerging confinement

DOE PAGES

Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter; ...

2015-05-21

In this study we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. Themore » light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q 2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q 2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.« less

A case-control study of the difficulties in daily functioning experienced by children with depressive disorder.

PubMed

Usami, Masahide; Iwadare, Yoshitaka; Watanabe, Kyota; Ushijima, Hirokage; Kodaira, Masaki; Okada, Takashi; Sasayama, Daimei; Sugiyama, Nobuhiro; Saito, Kazuhiko

2015-07-01

The parent-assessed children-with-difficulties questionnaire (Questionnaire-Children with Difficulties; QCD) is designed to evaluate a child׳s difficulties in functioning during specific periods of the day. This study aimed to use the QCD to evaluate the difficulties in daily functioning experienced by children with depressive disorders. A case-control design was used. The cases comprised 90 junior high school students with depressive disorder, whereas a community sample of 363 junior high school students was enrolled as controls. Behaviors were assessed using the QCD, Depression Self-Rating Scale (DSRS), Tokyo Autistic Behavior Scale (TABS), attention deficit hyperactivity disorder-rating scale (ADHD-RS), and Oppositional Defiant Behavior Inventory (ODBI). We then analyzed the effects of sex and diagnosis on the QCD scores as well as the correlation coefficients between the QCD and the other questionnaires. We included 90 cases (33 boys, 57 girls) with depressive disorders and 363 controls (180 boys, 183 girls). The QCD scores for the children with depressive disorders were significantly lower compared with those from the community sample (P<0.001). The morning, school-time, and night subscores of the QCD were lower for the children with both depressive disorders and truancy problems than for those with depressive disorders alone (P<0.001). Significant correlations were observed between the following: the night QCD subscore and the DSRS scores among boys, the morning QCD subscore and ADHD-RS inattention scores for all groups, and the evening QCD subscore and the TABS score. Parents reported that children with depressive disorders experienced greater difficulties in completing basic daily activities compared with community controls. These difficulties were dependent on sex, symptoms, and the time of day. The use of QCD to assess children with depressive disorders enables clinicians to clarify the time periods at which the children face difficulties. Copyright © 2015 Elsevier B.V. All rights reserved.

The Conformal Template and New Perspectives for Quantum Chromodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; /SLAC

2007-03-06

Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, themore » fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. One can also use conformal symmetry as a template for perturbative QCD predictions where the effects of the nonzero beta function can be systematically included in the scale of the QCD coupling. This leads to fixing of the renormalization scale and commensurate scale relations which relate observables without scale or scheme ambiguity. The results are consistent with the renormalization group and the analytic connection of QCD to Abelian theory at N{sub C} {yields} 0. I also discuss a number of novel phenomenological features of QCD. Initial- and .nal-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, di.ractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, nonperturbative antisymmetric sea quark distributions, anomalous heavy quark e.ects, and the unexpected effects of direct higher-twist processes.« less

Longitudinal conductivity in strong magnetic field in perturbative QCD: Complete leading order

NASA Astrophysics Data System (ADS)

Hattori, Koichi; Li, Shiyong; Satow, Daisuke; Yee, Ho-Ung

2017-04-01

We compute the longitudinal electrical conductivity in the presence of a strong background magnetic field in complete leading order of perturbative QCD, based on the assumed hierarchy of scales αse B ≪(mq2,T2)≪e B . We formulate an effective kinetic theory of lowest Landau level quarks with the leading order QCD collision term arising from 1-to-2 processes that become possible due to 1 +1 dimensional Landau level kinematics. In the small mq/T ≪1 regime, the longitudinal conductivity behaves as σz z˜e2(e B )T /(αsmq2log (T /mq)) , where the quark mass dependence can be understood from the chiral anomaly with the axial charge relaxation provided by a finite quark mass mq. We also present parametric estimates for the longitudinal and transverse "color conductivities" in the presence of the strong magnetic field, by computing dominant damping rates for quarks and gluons that are responsible for color charge transportation. We observe that the longitudinal color conductivity is enhanced by the strong magnetic field, which implies that the sphaleron transition rate in perturbative QCD is suppressed by the strong magnetic field due to the enhanced Lenz's law in color field dynamics.

Renormalization group invariance and optimal QCD renormalization scale-setting: a key issues review.

PubMed

Wu, Xing-Gang; Ma, Yang; Wang, Sheng-Quan; Fu, Hai-Bing; Ma, Hong-Hao; Brodsky, Stanley J; Mojaza, Matin

2015-12-01

A valid prediction for a physical observable from quantum field theory should be independent of the choice of renormalization scheme--this is the primary requirement of renormalization group invariance (RGI). Satisfying scheme invariance is a challenging problem for perturbative QCD (pQCD), since a truncated perturbation series does not automatically satisfy the requirements of the renormalization group. In a previous review, we provided a general introduction to the various scale setting approaches suggested in the literature. As a step forward, in the present review, we present a discussion in depth of two well-established scale-setting methods based on RGI. One is the 'principle of maximum conformality' (PMC) in which the terms associated with the β-function are absorbed into the scale of the running coupling at each perturbative order; its predictions are scheme and scale independent at every finite order. The other approach is the 'principle of minimum sensitivity' (PMS), which is based on local RGI; the PMS approach determines the optimal renormalization scale by requiring the slope of the approximant of an observable to vanish. In this paper, we present a detailed comparison of the PMC and PMS procedures by analyzing two physical observables R(e+e-) and [Formula: see text] up to four-loop order in pQCD. At the four-loop level, the PMC and PMS predictions for both observables agree within small errors with those of conventional scale setting assuming a physically-motivated scale, and each prediction shows small scale dependences. However, the convergence of the pQCD series at high orders, behaves quite differently: the PMC displays the best pQCD convergence since it eliminates divergent renormalon terms; in contrast, the convergence of the PMS prediction is questionable, often even worse than the conventional prediction based on an arbitrary guess for the renormalization scale. PMC predictions also have the property that any residual dependence on the choice of initial scale is highly suppressed even for low-order predictions. Thus the PMC, based on the standard RGI, has a rigorous foundation; it eliminates an unnecessary systematic error for high precision pQCD predictions and can be widely applied to virtually all high-energy hadronic processes, including multi-scale problems.

Renormalization group invariance and optimal QCD renormalization scale-setting: a key issues review

NASA Astrophysics Data System (ADS)

Wu, Xing-Gang; Ma, Yang; Wang, Sheng-Quan; Fu, Hai-Bing; Ma, Hong-Hao; Brodsky, Stanley J.; Mojaza, Matin

2015-12-01

A valid prediction for a physical observable from quantum field theory should be independent of the choice of renormalization scheme—this is the primary requirement of renormalization group invariance (RGI). Satisfying scheme invariance is a challenging problem for perturbative QCD (pQCD), since a truncated perturbation series does not automatically satisfy the requirements of the renormalization group. In a previous review, we provided a general introduction to the various scale setting approaches suggested in the literature. As a step forward, in the present review, we present a discussion in depth of two well-established scale-setting methods based on RGI. One is the ‘principle of maximum conformality’ (PMC) in which the terms associated with the β-function are absorbed into the scale of the running coupling at each perturbative order; its predictions are scheme and scale independent at every finite order. The other approach is the ‘principle of minimum sensitivity’ (PMS), which is based on local RGI; the PMS approach determines the optimal renormalization scale by requiring the slope of the approximant of an observable to vanish. In this paper, we present a detailed comparison of the PMC and PMS procedures by analyzing two physical observables R e+e- and Γ(H\\to b\\bar{b}) up to four-loop order in pQCD. At the four-loop level, the PMC and PMS predictions for both observables agree within small errors with those of conventional scale setting assuming a physically-motivated scale, and each prediction shows small scale dependences. However, the convergence of the pQCD series at high orders, behaves quite differently: the PMC displays the best pQCD convergence since it eliminates divergent renormalon terms; in contrast, the convergence of the PMS prediction is questionable, often even worse than the conventional prediction based on an arbitrary guess for the renormalization scale. PMC predictions also have the property that any residual dependence on the choice of initial scale is highly suppressed even for low-order predictions. Thus the PMC, based on the standard RGI, has a rigorous foundation; it eliminates an unnecessary systematic error for high precision pQCD predictions and can be widely applied to virtually all high-energy hadronic processes, including multi-scale problems.

Gravitation waves from QCD and electroweak phase transitions

NASA Astrophysics Data System (ADS)

Chen, Yidian; Huang, Mei; Yan, Qi-Shu

2018-05-01

We investigate the gravitation waves produced from QCD and electroweak phase transitions in the early universe by using a 5-dimension holographic QCD model and a holographic technicolor model. The dynamical holographic QCD model is to describe the pure gluon system, where a first order confinement-deconfinement phase transition can happen at the critical temperature around 250 MeV. The minimal holographic technicolor model is introduced to model the strong dynamics of electroweak, it can give a first order electroweak phase transition at the critical temperature around 100-360 GeV. We find that for both GW signals produced from QCD and EW phase transitions, in the peak frequency region, the dominant contribution comes from the sound waves, while away from the peak frequency region the contribution from the bubble collision is dominant. The peak frequency of gravitation wave determined by the QCD phase transition is located around 10-7 Hz which is within the detectability of FAST and SKA, and the peak frequency of gravitational wave predicted by EW phase transition is located at 0.002 - 0.007 Hz, which might be detectable by BBO, DECIGO, LISA and ELISA.

A systematic study of the strong interaction with P-barANDA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messchendorp, J. G.

2011-10-21

The theory of Quantum Chromo Dynamics (QCD) reproduces the strong interaction at distances much shorter than the size of the nucleon. At larger distance scales, the generation of hadron masses and confinement cannot yet be derived from first principles on basis of QCD. The PANDA experiment at FAIR will address the origin of these phenomena in controlled environments. Beams of antiprotons together with a multi-purpose and compact detection system will provide unique tools to perform studies of the strong interaction. This will be achieved via precision spectroscopy of charmonium and open-charm states, an extensive search for exotic objects such asmore » glueballs and hybrids, in-medium and hypernuclei spectroscopy, and more. An overview is given of the physics program of the P-barANDA collaboration.« less

Application of the principle of maximum conformality to the hadroproduction of the Higgs boson at the LHC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Sheng-Quan; Wu, Xing-Gang; Brodsky, Stanley J.

We present improved perturbative QCD (pQCD) predictions for Higgs boson hadroproduction at the LHC by applying the principle of maximum conformality (PMC), a procedure which resums the pQCD series using the renormalization group (RG), thereby eliminating the dependence of the predictions on the choice of the renormalization scheme while minimizing sensitivity to the initial choice of the renormalization scale. In previous pQCD predictions for Higgs boson hadroproduction, it has been conventional to assume that the renormalization scale μ r of the QCD coupling α s ( μ r ) is the Higgs mass and then to vary this choice overmore » the range 1 / 2 m H < μ r < 2 m H in order to estimate the theory uncertainty. However, this error estimate is only sensitive to the nonconformal β terms in the pQCD series, and thus it fails to correctly estimate the theory uncertainty in cases where a pQCD series has large higher-order contributions, as is the case for Higgs boson hadroproduction. Furthermore, this ad hoc choice of scale and range gives pQCD predictions which depend on the renormalization scheme being used, in contradiction to basic RG principles. In contrast, after applying the PMC, we obtain next-to-next-to-leading-order RG resummed pQCD predictions for Higgs boson hadroproduction which are renormalization-scheme independent and have minimal sensitivity to the choice of the initial renormalization scale. Taking m H = 125 GeV , the PMC predictions for the p p → H X Higgs inclusive hadroproduction cross sections for various LHC center-of-mass energies are σ Incl | 7 TeV = 21.2 1 + 1.36 - 1.32 pb , σ Incl | 8 TeV = 27.3 7 + 1.65 - 1.59 pb , and σ Incl | 13 TeV = 65.7 2 + 3.46 - 3.0 pb . We also predict the fiducial cross section σ fid ( p p → H → γ γ ) : σ fid | 7 TeV = 30.1 + 2.3 - 2.2 fb , σ fid | 8 TeV = 38.3 + 2.9 - 2.8 fb , and σ fid | 13 TeV = 85.8 + 5.7 - 5.3 fb . The error limits in these predictions include the small residual high-order renormalization-scale dependence plus the uncertainty from the factorization scale. The PMC predictions show better agreement with the ATLAS measurements than the LHC Higgs Cross Section Working Group predictions which are based on conventional renormalization-scale setting.« less

Two-gluon and trigluon glueballs from dynamical holography QCD

NASA Astrophysics Data System (ADS)

Chen, Yi-dian; Huang, Mei

2016-12-01

We study the scalar, vector and tensor two-gluon and trigluon glueball spectra in the framework of the 5-dimension dynamical holographic QCD model, where the metric structure is deformed self-consistently by the dilaton field. For comparison, the glueball spectra are also calculated in the hard-wall and soft-wall holographic QCD models. In order to distinguish glueballs with even and odd parities, we introduce a positive and negative coupling between the dilaton field and glueballs, and for higher spin glueballs, we introduce a deformed 5-dimension mass. With this set-up, there is only one free parameter from the quadratic dilaton profile in the dynamical holographic QCD model, which is fixed by the scalar glueball spectra. It is found that the two-gluon glueball spectra produced in the dynamical holographic QCD model are in good agreement with lattice data. Among six trigluon glueballs, the produced masses for 1±- and 2-- are in good agreement with lattice data, and the produced masses for 0--, 0+- and 2+- are around 1.5 GeV lighter than lattice results. This result might indicate that the three trigluon glueballs of 0--, 0+- and 2+- are dominated by the three-gluon condensate contribution. Supported by the NSFC (11175251, 11621131001), DFG and NSFC (CRC 110), CAS Key Project KJCX2-EW-N01, K.C.Wong Education Foundation, and Youth Innovation Promotion Association of CAS

Study of QCD-dynamics in η and η' production and decays

NASA Astrophysics Data System (ADS)

Beck, Reinhard; Wiedner, Ulrich

2017-01-01

One aim of this project lies in studying QCD dynamics using photoproduction of η and η' mesons with the CBELSA/TAPS experiment at the accelerator facility ELSA. Hadronic decay modes of η and η' are analyzed that allow the study of symmetry breaking effects in QCD. Furthermore, excited η-states produced with a photon beam are studied within the scope of this project. Of special interest is hereby the nature of the η(1405). The high data samples for η- and η'-photoproduction off the proton allow in addition the determination of polarization observables.

Instanton dominance over $$a_s$$ at low momenta from lattice QCD simulations at $$N_f=0$$, $$N_f=2+1$$ and $$N_f=2+1+1$$

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athenodorou, Andreas; Boucaud, Philippe; de Soto, Feliciano

We report on an instanton-based analysis of the gluon Green functions in the Landau gauge for low momenta; in particular we use lattice results for αs in the symmetric momentum subtraction scheme (MOM) for large-volume lattice simulations. We have exploited quenched gauge field configurations, Nf = 0, with both Wilson and tree-level Symanzik improved actions, and unquenched ones with Nf = 2 + 1 and Nf = 2 + 1 + 1 dynamical flavors (domain wall and twisted-mass fermions, respectively).We show that the dominance of instanton correlations on the low-momenta gluon Green functions can be applied to the determination ofmore » phenomenological parameters of the instanton liquid and, eventually, to a determination of the lattice spacing.We furthermore apply the Gradient Flow to remove short-distance fluctuations. The Gradient Flow gets rid of the QCD scale, ΛQCD, and reveals that the instanton prediction extents to large momenta. For those gauge field configurations free of quantum fluctuations, the direct study of topological charge density shows the appearance of large-scale lumps that can be identified as instantons, giving access to a direct study of the instanton density and size distribution that is compatible with those extracted from the analysis of the Green functions.« less

Implications of the principle of maximum conformality for the QCD strong coupling

DOE PAGES

Deur, Alexandre; Shen, Jian -Ming; Wu, Xing -Gang; ...

2017-08-14

The Principle of Maximum Conformality (PMC) provides scale-fixed perturbative QCD predictions which are independent of the choice of the renormalization scheme, as well as the choice of the initial renormalization scale. In this article, we will test the PMC by comparing its predictions for the strong couplingmore » $$\\alpha^s_{g_1}(Q)$$, defined from the Bjorken sum rule, with predictions using conventional pQCD scale-setting. The two results are found to be compatible with each other and with the available experimental data. However, the PMC provides a significantly more precise determination, although its domain of applicability ($$Q \\gtrsim 1.5$$ GeV) does not extend to as small values of momentum transfer as that of a conventional pQCD analysis ($$Q \\gtrsim 1$$ GeV). In conclusion, we suggest that the PMC range of applicability could be improved by a modified intermediate scheme choice or using a single effective PMC scale.« less

Degeneracy relations in QCD and the equivalence of two systematic all-orders methods for setting the renormalization scale

DOE PAGES

Bi, Huan -Yu; Wu, Xing -Gang; Ma, Yang; ...

2015-06-26

The Principle of Maximum Conformality (PMC) eliminates QCD renormalization scale-setting uncertainties using fundamental renormalization group methods. The resulting scale-fixed pQCD predictions are independent of the choice of renormalization scheme and show rapid convergence. The coefficients of the scale-fixed couplings are identical to the corresponding conformal series with zero β-function. Two all-orders methods for systematically implementing the PMC-scale setting procedure for existing high order calculations are discussed in this article. One implementation is based on the PMC-BLM correspondence (PMC-I); the other, more recent, method (PMC-II) uses the R δ-scheme, a systematic generalization of the minimal subtraction renormalization scheme. Both approaches satisfymore » all of the principles of the renormalization group and lead to scale-fixed and scheme-independent predictions at each finite order. In this work, we show that PMC-I and PMC-II scale-setting methods are in practice equivalent to each other. We illustrate this equivalence for the four-loop calculations of the annihilation ratio R e+e– and the Higgs partial width I'(H→bb¯). Both methods lead to the same resummed (‘conformal’) series up to all orders. The small scale differences between the two approaches are reduced as additional renormalization group {β i}-terms in the pQCD expansion are taken into account. In addition, we show that special degeneracy relations, which underly the equivalence of the two PMC approaches and the resulting conformal features of the pQCD series, are in fact general properties of non-Abelian gauge theory.« less

Modeling the small dark energy scale with a quintessential pseudoscalar boson

NASA Astrophysics Data System (ADS)

Kim, Jihn E.

2014-03-01

Democracy among the same type of particles is a useful paradigm in studying masses and interactions of particles with supersymmetry (SUSY) or without SUSY. This simple idea predicts the presence of massless particles. We attempt to use one of these massless pseudoscalar particles to generate the cosmological dark energy (DE) potential. To achieve the extremely shallow potential of DE, we require the pseudoscalar boson not couple to quantum chromodynamics (QCD) anomaly. Thus, we consider two pseudoscalars, one coupling to the QCD anomaly ( i.e., the QCD axion) and the other not coupling to the QCD anomaly. To obtain these two pseudoscalars, we introduce two approximate global U(1) symmetries to realize them as the pseudo-Goldstone bosons of the spontaneously broken U(1) symmetries. These global symmetries are dictated by a gravity-respecting discrete symmetry. Specifically, we consider an S 2( L) × S 2( R) × Z 10 R example and attempt to obtain the DE scale in terms of two observed fundamental mass scales, the grand unification scale M G and the electroweak scale υ ew.

A study of energy-energy correlations and measurement of {alpha}{sub s} at the Z{sup 0} resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-12-31

We present the energy-energy correlation (EEC) distribution and its asymmetry (AEEC) in hadronic decays of {Zeta}{sup 0} bosons measured by the SLD at SLAC. The data are found to be in good agreement with the predictions of perturbative QCD and fragmentation Monte Carlo models of hadron production. After correction for hadronization effects the data are compared with {Omicron}({alpha}{sub s}{sup 2}) perturbative QCD calculations from various authors. Fits to the central region of the EEC yield substantially different values of the QCD scale {lambda}{sub {ovr MS}} for each of the QCD calculations. There is also a sizeable dependence of the fittedmore » {lambda}{sub {ovr MS}} value on the QCD renormalization scale factor, f. Our preliminary results are {alpha}{sub s}(M {sub Z}) = 0.121 {plus_minus} 0.002(stat.) {plus_minus} 0.004(exp.sys.) {sub {minus}0.009}{sup +0.016} (theor.) for EEC and {alpha}{sub s}(M{sub Z}) = 0.108 {plus_minus} 0.003(stat.) {plus_minus} 0.005(exp.sys.){sub {minus}0.003}{sup +0.008}(theor.) for AEEC. The largest contribution to the error arises from the theoretical uncertainty in choosing the QCD renormalization scale.« less

Light-Front Hamiltonian Approach to the Bound-State Problem in Quantum Electrodynamics

NASA Astrophysics Data System (ADS)

Jones, Billy D.

1997-10-01

Why is the study of the Lamb shift in hydrogen, which at the level of detail found in this paper was largely completed by Bethe in 1947, of any real interest today? While completing such a calculation using new techniques may be very interesting for formal and academic reasons, our primary motivation is to lay groundwork for precision bound-state calculations in QCD. The Lamb shift provides an excellent pedagogical tool for illustrating light-front Hamiltonian techniques, which are not widely known; but more importantly it presents three of the central dynamical and computational problems that we must face to make these techniques useful for solving QCD: How does a constituent picture emerge in a gauge field theory? How do bound-state energy scales emerge non-perturbatively? How does rotational symmetry emerge in a non-perturbative light-front calculation?

Quantum Chromodynamics and Color Confinement (confinement 2000) - Proceedings of the International Symposium

NASA Astrophysics Data System (ADS)

Suganuma, H.; Fukushima, M.; Toki, H.

The Table of Contents for the book is as follows: * Preface * Opening Address * Monopole Condensation and Quark Confinement * Dual QCD, Effective String Theory, and Regge Trajectories * Abelian Dominance and Monopole Condensation * Non-Abelian Stokes Theorem and Quark Confinement in QCD * Infrared Region of QCD and Confining Configurations * BRS Quartet Mechanism for Color Confinement * Color Confinement and Quartet Mechanism * Numerical Tests of the Kugo-Ojima Color Confinement Criterion * Monopoles and Confinement in Lattice QCD * SU(2) Lattice Gauge Theory at T > 0 in a Finite Box with Fixed Holonomy * Confining and Dirac Strings in Gluodynamics * Cooling, Monopoles, and Vortices in SU(2) Lattice Gauge Theory * Quark Confinement Physics from Lattice QCD * An (Almost) Perfect Lattice Action for SU(2) and SU(3) Gluodynamics * Vortices and Confinement in Lattice QCD * P-Vortices, Nexuses and Effects of Gribov Copies in the Center Gauges * Laplacian Center Vortices * Center Vortices at Strong Couplings and All Couplings * Simulations in SO(3) × Z(2) Lattice Gauge Theory * Exciting a Vortex - the Cost of Confinement * Instantons in QCD * Deformation of Instanton in External Color Fields * Field Strength Correlators in the Instanton Liquid * Instanton and Meron Physics in Lattice QCD * The Dual Ginzburg-Landau Theory for Confinement and the Role of Instantons * Lattice QCD for Quarks, Gluons and Hadrons * Hadronic Spectral Functions in QCD * Universality and Chaos in Quantum Field Theories * Lattice QCD Study of Three Quark Potential * Probing the QCD Vacuum with Flavour Singlet Objects : η' on the Lattice * Lattice Studies of Quarks and Gluons * Quarks and Hadrons in QCD * Supersymmetric Nonlinear Sigma Models * Chiral Transition and Baryon-number Susceptibility * Light Quark Masses in QCD * Chiral Symmetry of Baryons and Baryon Resonances * Confinement and Bound States in QCD * Parallel Session * Off-diagonal Gluon Mass Generation and Strong Randomness of Off-diagonal Gluon Phase in the Maximally Abelian Gauge * On the Colour Confinement and the Minimal Surface * Glueball Mass and String Tension of SU(2) Gluodynamics from Abelian Monopoles and Strings * Application of the Non-Perturbative Renormalization Group to the Nambu-Jona-Lasinio Model at Finite Temperature and Density * Confining Flux-Tube and Hadrons in QCD * Gauge Symmetry Breakdown due to Dynamical Higgs Scalar * Spatial Structure of Quark Cooper Pairs * New Approach to Axial Coupling Constants in the QCD Sum Rule and Instanton Effects * String Breaking on a Lattice * Bethe-Salpeter Approach for Mesons within the Dual Ginzburg-Landau Theory * Gauge Dependence and Matching Procedure of a Nonrelativistic QCD Boundstate Formalism * A Mathematical Approach to the SU(2)-Quark Confinement * Simulations of Odd Flavors QCD by Hybrid Monte Carlo * Non-Perturbative Renormalization Group Analysis of Dynamical Chiral Symmetry Breaking with Beyond Ladder Contributions * Charmonium Physics in Finite Temperature Lattice QCD * From Meson-Nucleon Scattering to Vector Mesons in Nuclear Matter * Symposium Program * List of Participants

Power counting to better jet observables

NASA Astrophysics Data System (ADS)

Larkoski, Andrew J.; Moult, Ian; Neill, Duff

2014-12-01

Optimized jet substructure observables for identifying boosted topologies will play an essential role in maximizing the physics reach of the Large Hadron Collider. Ideally, the design of discriminating variables would be informed by analytic calculations in perturbative QCD. Unfortunately, explicit calculations are often not feasible due to the complexity of the observables used for discrimination, and so many validation studies rely heavily, and solely, on Monte Carlo. In this paper we show how methods based on the parametric power counting of the dynamics of QCD, familiar from effective theory analyses, can be used to design, understand, and make robust predictions for the behavior of jet substructure variables. As a concrete example, we apply power counting for discriminating boosted Z bosons from massive QCD jets using observables formed from the n-point energy correlation functions. We show that power counting alone gives a definite prediction for the observable that optimally separates the background-rich from the signal-rich regions of phase space. Power counting can also be used to understand effects of phase space cuts and the effect of contamination from pile-up, which we discuss. As these arguments rely only on the parametric scaling of QCD, the predictions from power counting must be reproduced by any Monte Carlo, which we verify using Pythia 8 and Herwig++. We also use the example of quark versus gluon discrimination to demonstrate the limits of the power counting technique.

Leptonic-decay-constant ratio f(K+)/f(π+) from lattice QCD with physical light quarks.

PubMed

Bazavov, A; Bernard, C; DeTar, C; Foley, J; Freeman, W; Gottlieb, Steven; Heller, U M; Hetrick, J E; Kim, J; Laiho, J; Levkova, L; Lightman, M; Osborn, J; Qiu, S; Sugar, R L; Toussaint, D; Van de Water, R S; Zhou, R

2013-04-26

A calculation of the ratio of leptonic decay constants f(K+)/f(π+) makes possible a precise determination of the ratio of Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |V(us)|/|V(ud)| in the standard model, and places a stringent constraint on the scale of new physics that would lead to deviations from unitarity in the first row of the CKM matrix. We compute f(K+)/f(π+) numerically in unquenched lattice QCD using gauge-field ensembles recently generated that include four flavors of dynamical quarks: up, down, strange, and charm. We analyze data at four lattice spacings a ≈ 0.06, 0.09, 0.12, and 0.15 fm with simulated pion masses down to the physical value 135 MeV. We obtain f(K+)/f(π+) = 1.1947(26)(37), where the errors are statistical and total systematic, respectively. This is our first physics result from our N(f) = 2+1+1 ensembles, and the first calculation of f(K+)/f(π+) from lattice-QCD simulations at the physical point. Our result is the most precise lattice-QCD determination of f(K+)/f(π+), with an error comparable to the current world average. When combined with experimental measurements of the leptonic branching fractions, it leads to a precise determination of |V(us)|/|V(ud)| = 0.2309(9)(4) where the errors are theoretical and experimental, respectively.

Nucleon-nucleon scattering from fully dynamical lattice QCD.

PubMed

Beane, S R; Bedaque, P F; Orginos, K; Savage, M J

2006-07-07

We present results of the first fully dynamical lattice QCD determination of nucleon-nucleon scattering lengths in the 1S0 channel and 3S1 - 3D1 coupled channels. The calculations are performed with domain-wall valence quarks on the MILC staggered configurations with a lattice spacing of b = 0.125 fm in the isospin-symmetric limit, and in the absence of electromagnetic interactions.

Continuous Advances in QCD 2008

NASA Astrophysics Data System (ADS)

Peloso, Marco M.

2008-12-01

1. High-order calculations in QCD and in general gauge theories. NLO evolution of color dipoles / I. Balitsky. Recent perturbative results on heavy quark decays / J. H. Piclum, M. Dowling, A. Pak. Leading and non-leading singularities in gauge theory hard scattering / G. Sterman. The space-cone gauge, Lorentz invariance and on-shell recursion for one-loop Yang-Mills amplitudes / D. Vaman, Y.-P. Yao -- 2. Heavy flavor physics. Exotic cc¯ mesons / E. Braaten. Search for new physics in B[symbol]-mixing / A. J. Lenz. Implications of D[symbol]-D[symbol] mixing for new physics / A. A. Petrov. Precise determinations of the charm quark mass / M. Steinhauser -- 3. Quark-gluon dynamics at high density and/or high temperature. Crystalline condensate in the chiral Gross-Neveu model / G. V. Dunne, G. Basar. The strong coupling constant at low and high energies / J. H. Kühn. Quarkyonic matter and the phase diagram of QCD / L. McLerran. Statistical QCD with non-positive measure / J. C. Osborn, K. Splittorff, J. J. M. Verbaarschot. From equilibrium to transport properties of strongly correlated fermi liquids / T. Schäfer. Lessons from random matrix theory for QCD at finite density / K. Splittorff, J. J. M. Verbaarschot -- 4. Methods and models of holographic correspondence. Soft-wall dynamics in AdS/QCD / B. Batell. Holographic QCD / N. Evans, E. Threlfall. QCD glueball sum rules and vacuum topology / H. Forkel. The pion form factor in AdS/QCD / H. J. Kwee, R. F. Lebed. The fast life of holographic mesons / R. C. Myers, A. Sinha. Properties of Baryons from D-branes and instantons / S. Sugimoto. The master space of N = 1 quiver gauge theories: counting BPS operators / A. Zaffaroni. Topological field congurations. Skyrmions in theories with massless adjoint quarks / R. Auzzi. Domain walls, localization and confinement: what binds strings inside walls / S. Bolognesi. Static interactions of non-abelian vortices / M. Eto. Vortices which do not abelianize dynamically: semi-classical origin of non-abelian monopoles / K. Konishi. A generalized construction for lumps and non-abelian vortices / W. Vinci -- 6. Dynamics in supersymmetric theories. Cusp anomalous dimension in planar maximally supersymmetric Yang-Mills theory / B. Basso. SO(2M) and USp(2M) (hyper)Kähler quotients and lumps / S. B. Gudnason -- 7. Other developments. Gluinos condensing at the CCNI: 4096 CPUs weigh in / J. Giedt ... [et al.]. Baryon Regge trajectories and the 1/N[symbol] expansion / J. L. Goity, N. Matagne. Infrared behavior of the fermion propagator in unquenched QED[symbol] with finite threshold effects / Y. Hoshino. Gauge fields in accelerated frames / F. Lenz. QCD at complex coupling, large order in perturbation theory and the gluon condensate / Y. Meurice. 511 KeV line and other diffuse emissions as a trace of the dark matter / A. R. Zhitnitsky -- 8. Glimpses of the conference.

A systematic approach to sketch Bethe-Salpeter equation

NASA Astrophysics Data System (ADS)

Qin, Si-xue

2016-03-01

To study meson properties, one needs to solve the gap equation for the quark propagator and the Bethe-Salpeter (BS) equation for the meson wavefunction, self-consistently. The gluon propagator, the quark-gluon vertex, and the quark-anti-quark scattering kernel are key pieces to solve those equations. Predicted by lattice-QCD and Dyson-Schwinger analyses of QCD's gauge sector, gluons are non-perturbatively massive. In the matter sector, the modeled gluon propagator which can produce a veracious description of meson properties needs to possess a mass scale, accordingly. Solving the well-known longitudinal Ward-Green-Takahashi identities (WGTIs) and the less-known transverse counterparts together, one obtains a nontrivial solution which can shed light on the structure of the quark-gluon vertex. It is highlighted that the phenomenologically proposed anomalous chromomagnetic moment (ACM) vertex originates from the QCD Lagrangian symmetries and its strength is proportional to the magnitude of dynamical chiral symmetry breaking (DCSB). The color-singlet vector and axial-vector WGTIs can relate the BS kernel and the dressed quark-gluon vertex to each other. Using the relation, one can truncate the gap equation and the BS equation, systematically, without violating crucial symmetries, e.g., gauge symmetry and chiral symmetry.

Basic Facts about the Pion

NASA Astrophysics Data System (ADS)

Roberts, Craig

2015-04-01

With discovery of the Higgs boson, the Standard Model of Particle Physics became complete. Its formulation and verification are a remarkable story. However, the most important chapter is the least understood. Quantum Chromodynamics (QCD) is that part of the Standard Model which is supposed to describe all of nuclear physics and yet, almost fifty years after the discovery of quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: pions, neutrons, protons. QCD is characterised by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB), whose implications are truly extraordinary. This presentation will reveal how DCSB, not the Higgs boson, generates more than 98% of the visible mass in the Universe, explain why confinement guarantees that condensates, those quantities that were commonly viewed as constant mass-scales that fill all spacetime, are instead wholly contained within hadrons; and, with particular focus on the pion, elucidate a range of observable consequences of these phenomena whose measurement is the focus of a vast international experimental programme. This research was supported by U.S. Department of Energy, Office of Science, Office of Nuclear Physics, Contract No. DE-AC02-06CH11357.

Determination of $${{\\rm{\\Lambda }}}_{\\overline{{\\rm{MS}}}}$$ at five loops from holographic QCD

DOE PAGES

Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

2017-08-25

Here, the recent determination of themore » $$\\beta$$--function of the QCD running coupling $$\\alpha_{\\overline{MS}}(Q^2)$$ to five-loops, provides a verification of the convergence of a novel method for determining the fundamental QCD parameter $$\\Lambda_s$$ based on the Light-Front Holographic approach to nonperturbative QCD. The new 5-loop analysis, together with improvements in determining the holographic QCD nonperturbative scale parameter $$\\kappa$$ from hadronic spectroscopy, leads to an improved precision of the value of $$\\Lambda_s$$ in the $${\\overline{MS}}$$ scheme close to a factor of two; we find $$\\Lambda^{(3)}_{\\overline{MS}}=0.339\\pm0.019$$ GeV for $$n_{f}=3$$, in excellent agreement with the world average, $$\\Lambda_{\\overline{MS}}^{(3)}=0.332\\pm0.017$$ GeV. Lastly, we also discuss the constraints imposed on the scale dependence of the strong coupling in the nonperturbative domain by superconformal quantum mechanics and its holographic embedding in anti-de Sitter space.« less

A study of jet production rates and a test of QCD on the Z 0 resonance

NASA Astrophysics Data System (ADS)

Akrawy, M. Z.; Alexander, G.; Allison, J.; Allport, P. P.; Anderson, K. J.; Armitage, J. C.; Arnison, G. T. J.; Ashton, P.; Azuelos, G.; Baines, J. T. M.; Ball, A. H.; Banks, J.; Barker, G. J.; Barlow, R. J.; Batley, J. R.; Bavaria, G.; Beard, C.; Beck, F.; Bell, K. W.; Bella, G.; Bethke, S.; Biebel, O.; Bloodworth, I. J.; Bock, P.; Boerner, H.; Breuker, H.; Brown, R. M.; Brun, R.; Buijs, A.; Burckhart, H. J.; Capiluppi, P.; Carnegie, R. K.; Carter, A. A.; Carter, J. R.; Chang, C. Y.; Charlton, D. G.; Chrin, J. T. M.; Cohen, I.; Conboy, J. E.; Couch, M.; Coupland, M.; Cuffiani, M.; Dado, S.; Dallavalle, G. M.; Davies, O. W.; Deninno, M. M.; Dieckmann, A.; Dittmar, M.; Dixit, M. S.; Duchesneau, D.; Duchovni, E.; Duerdoth, I. P.; Dumas, D.; El Mamouni, H.; Elcombe, P. A.; Estabrooks, P. G.; Fabbri, F.; Farthouat, P.; Fischer, H. M.; Fong, D. G.; French, M. T.; Fukunaga, C.; Gandois, B.; Ganel, O.; Gary, J. W.; Geddes, N. I.; Gee, C. N. P.; Geich-Gimbel, C.; Gensler, S. W.; Gentit, F. X.; Giacomelli, G.; Gibson, W. R.; Gillies, J. D.; Goldberg, J.; Goodrick, M. J.; Gorn, W.; Granite, D.; Gross, E.; Grosse-Wiesmann, P.; Grunhaus, J.; Hagedorn, H.; Hagemann, J.; Hansroul, M.; Hargrove, C. K.; Hart, J.; Hattersley, P. M.; Hatzifotiadou, D.; Hauschild, M.; Hawkes, C. M.; Heflin, E.; Heintze, J.; Hemingway, R. J.; Heuer, R. D.; Hill, J. C.; Hillier, S. J.; Hinde, P. S.; Ho, C.; Hobbs, J. D.; Hobson, P. R.; Hochman, D.; Holl, B.; Homer, R. J.; Hou, S. R.; Howarth, C. P.; Hughes-Jones, R. E.; Igo-Kemenes, P.; Imori, M.; Imrie, D. C.; Jawahery, A.; Jeffreys, P. W.; Jeremie, H.; Jimack, M.; Jin, E.; Jobes, M.; Jones, R. W. L.; Jovanovic, P.; Karlen, D.; Kawagoe, K.; Kawamoto, T.; Kellogg, R. G.; Kennedy, B. W.; Kleinwort, C.; Klem, D. E.; Knop, G.; Kobayashi, T.; Köpke, L.; Kokott, T. P.; Koshiba, M.; Kowalewski, R.; Kreutzmann, H.; Von Krogh, J.; Kroll, J.; Kyberd, P.; Lafferty, G. D.; Lamarche, F.; Larson, W. J.; Lasota, M. M. B.; Layter, J. G.; Le Du, P.; Leblanc, P.; Lellouch, D.; Lennert, P.; Lessard, L.; Levinson, L.; Lloyd, S. L.; Loebinger, F. K.; Lorah, J. M.; Lorazo, B.; Losty, M. J.; Ludwig, J.; Lupu, N.; Ma, J.; Macbeth, A. A.; Mannelli, M.; Marcellini, S.; Maringer, G.; Martin, J. P.; Mashimo, T.; Mättig, P.; Maur, U.; McMahon, T. J.; McPherson, A. C.; Meijers, F.; Menszner, D.; Merritt, F. S.; Mes, H.; Michelini, A.; Middleton, R. P.; Mikenberg, G.; Miller, D. J.; Milstene, C.; Minowa, M.; Mohr, W.; Montanari, A.; Mori, T.; Moss, M. W.; Muller, A.; Murphy, P. G.; Murray, W. J.; Nellen, B.; Nguyen, H. H.; Nozaki, M.; O'Dowd, A. J. P.; O'Neale, S. W.; O'Neill, B.; Oakham, F. G.; Odorici, F.; Ogg, M.; Oh, H.; Oreglia, M. J.; Orito, S.; Patrick, G. N.; Pawley, S. J.; Perez, A.; Pilcher, J. E.; Pinfold, J. L.; Plane, D. E.; Poli, B.; Possoz, A.; Pouladdej, A.; Pritchard, T. W.; Quast, G.; Raab, J.; Redmond, M. W.; Rees, D. L.; Regimbald, M.; Riles, K.; Roach, C. M.; Roehner, F.; Rollnik, A.; Roney, J. M.; Rossi, A. M.; Routenburg, P.; Runge, K.; Runolfsson, O.; Sanghera, S.; Sansum, R. A.; Sasaki, M.; Saunders, B. J.; Schaile, A. D.; Schaile, O.; Schappert, W.; Scharff-Hansen, P.; von der Schmitt, H.; Schreiber, S.; Schwarz, J.; Shapira, A.; Shen, B. C.; Sherwood, P.; Simon, A.; Siroli, G. P.; Skuja, A.; Smith, A. M.; Smith, T. J.; Snow, G. A.; Spreadbury, E. J.; Springer, R. W.; Sproston, M.; Stephens, K.; Stier, H. E.; Ströhmer, R.; Strom, D.; Takeda, H.; Takeshita, T.; Tsukamoto, T.; Turner, M. F.; Tysarczyk, G.; van den Plas, D.; Vandalen, G. J.; Virtue, C. J.; Wagner, A.; Wahl, C.; Wang, H.; Ward, C. P.; Ward, D. R.; Waterhouse, J.; Watkins, P. M.; Watson, A. T.; Watson, N. K.; Weber, M.; Weisz, S.; Wermes, N.; Weymann, M.; Wilson, G. W.; Wilson, J. A.; Wingerter, I.; Winterer, V.-H.; Wood, N. C.; Wotton, S.; Wuensch, B.; Wyatt, T. R.; Yaari, R.; Yamashita, H.; Yang, Y.; Yekutieli, G.; Zeuner, W.; Zorn, G. T.; Zylberajch, S.; OPAL Collaboration

1990-02-01

Relative production rates of multijet hadronic final states of Z 0 boson decays, observed in e +e - annihilation around 91 GeV centre of mass energy, are presented. The data can be well described by analytic O( αs2) QCD calculations and by QCD shower model calaculations with parameters as determined at lower energies. A first judgement of Λ overlineMS and of the renormalization scale μ2 in O( αs2) QCD results in values similar to those obtained in the continuum of e +e - annihilations. Significant scaling violations are observed when the 3-jet fractions are compared to the corresponding results from smaller centre of mass energies. They can be interpreted as being entirely due tot the energy dependence of αs, as proposed by the nonabelian nature of QCD, The possibility of an energy independent coupling constant can be excluded with a significance of 5.7 standard deviations.

Superconformal Algebraic Approach to Hadron Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

de Teramond, Guy F.; Brodsky, Stanley J.; Deur, Alexandre

2017-03-01

Fundamental aspects of nonperturbative QCD dynamics which are not obvious from its classical Lagrangian, such as the emergence of a mass scale and confinement, the existence of a zero mass bound state, the appearance of universal Regge trajectories and the breaking of chiral symmetry are incorporated from the onset in an effective theory based on superconformal quantum mechanics and its embedding in a higher dimensional gravitational theory. In addition, superconformal quantum mechanics gives remarkable connections between the light meson and nucleon spectra. This new approach to hadron physics is also suitable to describe nonperturbative QCD observables based on structure functions,more » such as GPDs, which are not amenable to a first-principle computation. The formalism is also successful in the description of form factors, the nonperturbative behavior of the strong coupling and diffractive processes. We also discuss in this article how the framework can be extended rather successfully to the heavy-light hadron sector.« less

On microscopic structure of the QCD vacuum

NASA Astrophysics Data System (ADS)

Pak, D. G.; Lee, Bum-Hoon; Kim, Youngman; Tsukioka, Takuya; Zhang, P. M.

2018-05-01

We propose a new class of regular stationary axially symmetric solutions in a pure QCD which correspond to monopole-antimonopole pairs at macroscopic scale. The solutions represent vacuum field configurations which are locally stable against quantum gluon fluctuations in any small space-time vicinity. This implies that the monopole-antimonopole pair can serve as a structural element in microscopic description of QCD vacuum formation.

Equivalence of the AdS-metric and the QCD running coupling

NASA Astrophysics Data System (ADS)

Pirner, H. J.; Galow, B.

2009-08-01

We use the functional form of the QCD running coupling to modify the conformal metric in AdS/CFT mapping the fifth-dimensional z-coordinate to the energy scale in the four-dimensional QCD. The resulting type-0 string theory in five dimensions is solved with the Nambu-Goto action giving good agreement with the Coulombic and confinement QQbar potential.

Quantum Yang-Mills Dark Energy

NASA Astrophysics Data System (ADS)

Pasechnik, Roman

2016-02-01

In this short review, I discuss basic qualitative characteristics of quantum non-Abelian gauge dynamics in the non-stationary background of the expanding Universe in the framework of the standard Einstein--Yang--Mills formulation. A brief outlook of existing studies of cosmological Yang--Mills fields and their properties will be given. Quantum effects have a profound impact on the gauge field-driven cosmological evolution. In particular, a dynamical formation of the spatially-homogeneous and isotropic gauge field condensate may be responsible for both early and late-time acceleration, as well as for dynamical compensation of non-perturbative quantum vacua contributions to the ground state of the Universe. The main properties of such a condensate in the effective QCD theory at the flat Friedmann--Lema\\'itre--Robertson--Walker (FLRW) background will be discussed within and beyond perturbation theory. Finally, a phenomenologically consistent dark energy can be induced dynamically as a remnant of the QCD vacua compensation arising from leading-order graviton-mediated corrections to the QCD ground state.

Importance of proper renormalization scale-setting for QCD testing at colliders

DOE PAGES

Wu, Xing -Gang; Wang, Sheng -Quan; Brodsky, Stanley J.

2015-12-22

A primary problem affecting perturbative quantum chromodynamic (pQCD) analyses is the lack of a method for setting the QCD running-coupling renormalization scale such that maximally precise fixed-order predictions for physical observables are obtained. The Principle of Maximum Conformality (PMC) eliminates the ambiguities associated with the conventional renormalization scale-setting procedure, yielding predictions that are independent of the choice of renormalization scheme. The QCD coupling scales and the effective number of quark flavors are set order-by-order in the pQCD series. The PMC has a solid theoretical foundation, satisfying the standard renormalization group invariance condition and all of the self-consistency conditions derived frommore » the renormalization group. The PMC scales at each order are obtained by shifting the arguments of the strong force coupling constant αs to eliminate all non-conformal {βi} terms in the pQCD series. The {βi} terms are determined from renormalization group equations without ambiguity. The correct behavior of the running coupling at each order and at each phase-space point can then be obtained. The PMC reduces in the N C → 0 Abelian limit to the Gell-Mann-Low method. In this brief report, we summarize the results of our recent application of the PMC to a number of collider processes, emphasizing the generality and applicability of this approach. A discussion of hadronic Z decays shows that, by applying the PMC, one can achieve accurate predictions for the total and separate decay widths at each order without scale ambiguities. We also show that, if one employs the PMC to determine the top-quark pair forward-backward asymmetry at the next-to-next-to-leading order level, one obtains a comprehensive, self-consistent pQCD explanation for the Tevatron measurements of the asymmetry. This accounts for the “increasing-decreasing” behavior observed by the D0 collaboration for increasing tt¯ invariant mass. At lower energies, the angular distributions of heavy quarks can be used to obtain a direct determination of the heavy quark potential. A discussion of the angular distributions of massive quarks and leptons is also presented, including the fermionic component of the two-loop corrections to the electromagnetic form factors. Furthermore, these results demonstrate that the application of the PMC systematically eliminates a major theoretical uncertainty for pQCD predictions, thus increasing collider sensitivity to possible new physics beyond the Standard Model.« less

Parallel Processing and Scientific Applications

DTIC Science & Technology

1992-11-30

Lattice QCD Calculations on the Connection Machine), SIAM News 24, 1 (May 1991) 5. C. F. Baillie and D. A. Johnston, Crumpling Dynamically Triangulated...hypercubic lattice ; in the second, the surface is randomly triangulated once at the beginning of the simulation; and in the third the random...Sharpe, QCD with Dynamical Wilson Fermions 1I, Phys. Rev. D44, 3272 (1991), 8. R. Gupta and C. F. Baillie, Critical Behavior of the 2D XY Model, Phys

Job Management and Task Bundling

NASA Astrophysics Data System (ADS)

Berkowitz, Evan; Jansen, Gustav R.; McElvain, Kenneth; Walker-Loud, André

2018-03-01

High Performance Computing is often performed on scarce and shared computing resources. To ensure computers are used to their full capacity, administrators often incentivize large workloads that are not possible on smaller systems. Measurements in Lattice QCD frequently do not scale to machine-size workloads. By bundling tasks together we can create large jobs suitable for gigantic partitions. We discuss METAQ and mpi_jm, software developed to dynamically group computational tasks together, that can intelligently backfill to consume idle time without substantial changes to users' current workflows or executables.

Charmed tetraquarks Tcc and Tcs from dynamical lattice QCD simulations

NASA Astrophysics Data System (ADS)

Ikeda, Yoichi; Charron, Bruno; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

2014-02-01

Charmed tetraquarks Tcc=(ccubardbar) and Tcs=(csubardbar) are studied through the S-wave meson-meson interactions, D-D, Kbar-D, D-D* and Kbar-D*, on the basis of the (2+1)-flavor lattice QCD simulations with the pion mass mπ≃410, 570 and 700 MeV. For the charm quark, the relativistic heavy quark action is employed to treat its dynamics on the lattice. Using the HAL QCD method, we extract the S-wave potentials in lattice QCD simulations, from which the meson-meson scattering phase shifts are calculated. The phase shifts in the isospin triplet (I=1) channels indicate repulsive interactions, while those in the I=0 channels suggest attraction, growing as mπ decreases. This is particularly prominent in the Tcc (JP=1+,I=0) channel, though neither bound state nor resonance are found in the range mπ=410-700 MeV. We make a qualitative comparison of our results with the phenomenological diquark picture.

Resonant conversions of QCD axions into hidden axions and suppressed isocurvature perturbations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitajima, Naoya; Takahashi, Fuminobu, E-mail: kitajima@tuhep.phys.tohoku.ac.jp, E-mail: fumi@tuhep.phys.tohoku.ac.jp

2015-01-01

We study in detail MSW-like resonant conversions of QCD axions into hidden axions, including cases where the adiabaticity condition is only marginally satisfied, and where anharmonic effects are non-negligible. When the resonant conversion is efficient, the QCD axion abundance is suppressed by the hidden and QCD axion mass ratio. We find that, when the resonant conversion is incomplete due to a weak violation of the adiabaticity, the CDM isocurvature perturbations can be significantly suppressed, while non-Gaussianity of the isocurvature perturbations generically remain unsuppressed. The isocurvature bounds on the inflation scale can therefore be relaxed by the partial resonant conversion ofmore » the QCD axions into hidden axions.« less

Scheme Variations of the QCD Coupling and Hadronic τ Decays

NASA Astrophysics Data System (ADS)

Boito, Diogo; Jamin, Matthias; Miravitllas, Ramon

2016-10-01

The quantum chromodynamics (QCD) coupling αs is not a physical observable of the theory, since it depends on conventions related to the renormalization procedure. We introduce a definition of the QCD coupling, denoted by α^s, whose running is explicitly renormalization scheme invariant. The scheme dependence of the new coupling α^s is parametrized by a single parameter C , related to transformations of the QCD scale Λ . It is demonstrated that appropriate choices of C can lead to substantial improvements in the perturbative prediction of physical observables. As phenomenological applications, we study e+e- scattering and decays of the τ lepton into hadrons, both being governed by the QCD Adler function.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deur, Alexandre; Shen, Jian -Ming; Wu, Xing -Gang

The Principle of Maximum Conformality (PMC) provides scale-fixed perturbative QCD predictions which are independent of the choice of the renormalization scheme, as well as the choice of the initial renormalization scale. In this article, we will test the PMC by comparing its predictions for the strong couplingmore » $$\\alpha^s_{g_1}(Q)$$, defined from the Bjorken sum rule, with predictions using conventional pQCD scale-setting. The two results are found to be compatible with each other and with the available experimental data. However, the PMC provides a significantly more precise determination, although its domain of applicability ($$Q \\gtrsim 1.5$$ GeV) does not extend to as small values of momentum transfer as that of a conventional pQCD analysis ($$Q \\gtrsim 1$$ GeV). In conclusion, we suggest that the PMC range of applicability could be improved by a modified intermediate scheme choice or using a single effective PMC scale.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

Here, the recent determination of themore » $$\\beta$$--function of the QCD running coupling $$\\alpha_{\\overline{MS}}(Q^2)$$ to five-loops, provides a verification of the convergence of a novel method for determining the fundamental QCD parameter $$\\Lambda_s$$ based on the Light-Front Holographic approach to nonperturbative QCD. The new 5-loop analysis, together with improvements in determining the holographic QCD nonperturbative scale parameter $$\\kappa$$ from hadronic spectroscopy, leads to an improved precision of the value of $$\\Lambda_s$$ in the $${\\overline{MS}}$$ scheme close to a factor of two; we find $$\\Lambda^{(3)}_{\\overline{MS}}=0.339\\pm0.019$$ GeV for $$n_{f}=3$$, in excellent agreement with the world average, $$\\Lambda_{\\overline{MS}}^{(3)}=0.332\\pm0.017$$ GeV. Lastly, we also discuss the constraints imposed on the scale dependence of the strong coupling in the nonperturbative domain by superconformal quantum mechanics and its holographic embedding in anti-de Sitter space.« less

QCDOC: A 10-teraflops scale computer for lattice QCD

NASA Astrophysics Data System (ADS)

Chen, D.; Christ, N. H.; Cristian, C.; Dong, Z.; Gara, A.; Garg, K.; Joo, B.; Kim, C.; Levkova, L.; Liao, X.; Mawhinney, R. D.; Ohta, S.; Wettig, T.

2001-03-01

The architecture of a new class of computers, optimized for lattice QCD calculations, is described. An individual node is based on a single integrated circuit containing a PowerPC 32-bit integer processor with a 1 Gflops 64-bit IEEE floating point unit, 4 Mbyte of memory, 8 Gbit/sec nearest-neighbor communications and additional control and diagnostic circuitry. The machine's name, QCDOC, derives from "QCD On a Chip".

Scheme variations of the QCD coupling

NASA Astrophysics Data System (ADS)

Boito, Diogo; Jamin, Matthias; Miravitllas, Ramon

2017-03-01

The Quantum Chromodynamics (QCD) coupling αs is a central parameter in the Standard Model of particle physics. However, it depends on theoretical conventions related to renormalisation and hence is not an observable quantity. In order to capture this dependence in a transparent way, a novel definition of the QCD coupling, denoted by â, is introduced, whose running is explicitly renormalisation scheme invariant. The remaining renormalisation scheme dependence is related to transformations of the QCD scale Λ, and can be parametrised by a single parameter C. Hence, we call â the C-scheme coupling. The dependence on C can be exploited to study and improve perturbative predictions of physical observables. This is demonstrated for the QCD Adler function and hadronic decays of the τ lepton.

Multiscale Monte Carlo equilibration: Two-color QCD with two fermion flavors

DOE PAGES

Detmold, William; Endres, Michael G.

2016-12-02

In this study, we demonstrate the applicability of a recently proposed multiscale thermalization algorithm to two-color quantum chromodynamics (QCD) with two mass-degenerate fermion flavors. The algorithm involves refining an ensemble of gauge configurations that had been generated using a renormalization group (RG) matched coarse action, thereby producing a fine ensemble that is close to the thermalized distribution of a target fine action; the refined ensemble is subsequently rethermalized using conventional algorithms. Although the generalization of this algorithm from pure Yang-Mills theory to QCD with dynamical fermions is straightforward, we find that in the latter case, the method is susceptible tomore » numerical instabilities during the initial stages of rethermalization when using the hybrid Monte Carlo algorithm. We find that these instabilities arise from large fermion forces in the evolution, which are attributed to an accumulation of spurious near-zero modes of the Dirac operator. We propose a simple strategy for curing this problem, and demonstrate that rapid thermalization--as probed by a variety of gluonic and fermionic operators--is possible with the use of this solution. Also, we study the sensitivity of rethermalization rates to the RG matching of the coarse and fine actions, and identify effective matching conditions based on a variety of measured scales.« less

Neutrinoless double beta decay and QCD running at low energy scales

NASA Astrophysics Data System (ADS)

González, M.; Hirsch, M.; Kovalenko, S. G.

2018-06-01

There is a common belief that the main uncertainties in the theoretical analysis of neutrinoless double beta (0 ν β β ) decay originate from the nuclear matrix elements. Here, we uncover another previously overlooked source of potentially large uncertainties stemming from nonperturbative QCD effects. Recently perturbative QCD corrections have been calculated for all dimension 6 and 9 effective operators describing 0 ν β β -decay and their importance for a reliable treatment of 0 ν β β -decay has been demonstrated. However, these perturbative results are valid at energy scales above ˜1 GeV , while the typical 0 ν β β scale is about ˜100 MeV . In view of this fact we examine the possibility of extrapolating the perturbative results towards sub-GeV nonperturbative scales on the basis of the QCD coupling constant "freezing" behavior using background perturbation theory. Our analysis suggests that such an infrared extrapolation does modify the perturbative results for both short-range and long-range mechanisms of 0 ν β β -decay in general only moderately. We also discuss that the tensor⊗tensor effective operator cannot appear alone in the low energy limit of any renormalizable high-scale model and then demonstrate that all five linearly independent combinations of the scalar and tensor operators, which can appear in renormalizable models, are infrared stable.

PREFACE: Focus section on Hadronic Physics

NASA Astrophysics Data System (ADS)

Roberts, Craig; Swanson, Eric

2007-07-01

Hadronic physics is the study of strongly interacting matter and its underlying theory, Quantum Chromodynamics (QCD). The field had its beginnings after World War Two, when hadrons were discovered in ever increasing numbers. Today, it encompasses topics like the quark-gluon structure of hadrons at varying scales, the quark-gluon plasma and hadronic matter at extreme temperature and density; it also underpins nuclear physics and has significant impact on particle physics, astrophysics, and cosmology. Among the goals of hadronic physics are to determine the parameters of QCD, understand the origin and characteristics of confinement, understand the dynamics and consequences of dynamical chiral symmetry breaking, explore the role of quarks and gluons in nuclei and in matter under extreme conditions and understand the quark and gluon structure of hadrons. In general, the process is one of discerning the relevant degrees of freedom and relating these to the fundamental fields of QCD. The emphasis is on understanding QCD, rather than testing it. The papers gathered in this special focus section of Journal of Physics G: Nuclear and Particle Physics attempt to cover this broad range of subjects. Alkofer and Greensite examine the issue of quark and gluon confinement with the focus on models of the QCD vacuum, lattice gauge theory investigations, and the relationship to the AdS/CFT correspondence postulate. Arrington et al. review nucleon form factors and their role in determining quark orbital momentum, the strangeness content of the nucleon, meson cloud effects, and the transition from nonperturbative to perturbative QCD dynamics. The physics associated with hadronic matter at high temperature and density and at low Bjorken-x at the Relativistic Heavy Ion Collider (RHIC), the SPS at CERN, and at the future LHC is summarized by d'Enterria. The article of Lee and Smith examines experiment and theory associated with electromagnetic meson production from nucleons and illustrates how the structure of the nucleon is revealed. Reimer reviews how the Drell--Yan process can be used to explore the sea quark structure of nucleons, thereby probing such phenomena as flavour asymmetry in the nucleon and nuclear medium modification of nucleon properties. The exploitation of the B factories has led to a resurgence of interest in heavy quark spectroscopy. Concurrently, interest in light quark spectroscopy and gluonic excitations remains high, with several new experimental efforts in the planning or building stages. The current status of all of this is reviewed by Rosner. Finally, Vogelsang summarizes the status of polarized deep inelastic lepton-nucleon scattering experiments at RHIC and their impact on the theoretical understanding of nucleon helicity structure, gluon polarization in the nucleus, and transverse spin asymmetries. Of course, hadronic physics is a much broader subject than can be conveyed in this special focus section; advances in effective field theory, lattice gauge theory, generalised parton distributions and many other subfields are not covered here. Nevertheless, we hope that this focus section will help the reader appreciate the vitality, breadth of endeavour, and the phenomenological richness of hadronic physics.

QCD and Light-Front Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.

2011-01-10

AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equalmore » light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.« less

Form factors and differential branching ratio of B →K μ+μ- in AdS/QCD

NASA Astrophysics Data System (ADS)

Momeni, S.; Khosravi, R.

2018-03-01

The holographic distribution amplitudes (DAs) for the K pseudoscalar meson are derived. For this aim, the light-front wave function (LFWF) of the K meson is extracted within the framework of the anti-de Sitter/quantum chromodynamics (AdS/QCD) correspondence. We consider a momentum-dependent (dynamical) helicity wave function that contains the dynamical spin effects. We use the LFWF to predict the radius and the electromagnetic form factor of the kaon and compare them with the experimental values. Then, the holographic twist-2 DA of K meson ϕK(α ,μ ) is investigated and compared with the result of the light-cone sum rules (LCSR). The transition form factors of the semileptonic B →K ℓ+ℓ- decays are derived from the holographic DAs of the kaon. With the help of these form factors, the differential branching ratio of the B →K μ+μ- on q2 is plotted. A comparison is made between our prediction in AdS/QCD and the results obtained from two models including the LCSR and the lattice QCD as well as the experimental values.

Scale-setting, flavor dependence, and chiral symmetry restoration

DOE PAGES

Binosi, D; Roberts, Craig D.; Rodriguez-Quintero, J.

2017-06-13

Here, we determine the flavor dependence of the renormalization-group-invariant running interaction through judicious use of both unquenched Dyson-Schwinger equation and lattice results for QCD’s gauge-sector two-point functions. An important step is the introduction of a physical scale setting procedure that enables a realistic expression of the effect of different numbers of active quark flavours on the interaction. Using this running interaction in concert with a well constrained class of dressed–gluon-quark vertices, we estimate the critical number of active lighter-quarks above which dynamical chiral symmetry breaking becomes impossible: n cr f ≈ 9; and hence in whose neighborhood QCD is plausiblymore » a conformal theory.« less

Fundamental dynamics: Past, present and the future — like CP violation and EDMs

NASA Astrophysics Data System (ADS)

Bigi, Ikaros I.

2015-04-01

Working with Kolya Uraltsev was a real 'marvel' for me in general, but in particular about CP and T violation, QCD and its impact on transitions in heavy flavor hadrons and EDMs. The goal was — and still is — to define fundamental parameters for dynamics, how to measure them and compare SM forces with New Dynamics using the best tools including our brains. The correlations of them with accurate data were crucial for Kolya. Here is a review of CP asymmetries in B, D and τ decays, the impact of perturbative and non-perturbative QCD, about EDMs till 2013 — and for the future.

Towards understanding Regge trajectories in holographic QCD

NASA Astrophysics Data System (ADS)

Catà, Oscar

2007-05-01

We reassess a work done by Migdal on the spectrum of low-energy vector mesons in QCD in the light of the anti-de Sitter (AdS)-QCD correspondence. Recently, a tantalizing parallelism was suggested between Migdal’s work and a family of holographic duals of QCD. Despite the intriguing similarities, both approaches face a major drawback: the spectrum is in conflict with well-tested Regge scaling. However, it has recently been shown that holographic duals can be modified to accommodate Regge behavior. Therefore, it is interesting to understand whether Regge behavior can also be achieved in Migdal’s approach. In this paper we investigate this issue. We find that Migdal’s approach, which is based on a modified Padé approximant, is closely related to the issue of quark-hadron duality breakdown in QCD.

Identifying QCD Transition Using Deep Learning

NASA Astrophysics Data System (ADS)

Zhou, Kai; Pang, Long-gang; Su, Nan; Petersen, Hannah; Stoecker, Horst; Wang, Xin-Nian

2018-02-01

In this proceeding we review our recent work using supervised learning with a deep convolutional neural network (CNN) to identify the QCD equation of state (EoS) employed in hydrodynamic modeling of heavy-ion collisions given only final-state particle spectra ρ(pT, V). We showed that there is a traceable encoder of the dynamical information from phase structure (EoS) that survives the evolution and exists in the final snapshot, which enables the trained CNN to act as an effective "EoS-meter" in detecting the nature of the QCD transition.

Chiral magnetic effect in lattice QCD with a chiral chemical potential.

PubMed

Yamamoto, Arata

2011-07-15

We perform a first lattice QCD simulation including a two-flavor dynamical fermion with a chiral chemical potential. Because the chiral chemical potential gives rise to no sign problem, we can exactly analyze a chirally imbalanced QCD matter by Monte Carlo simulation. By applying an external magnetic field to this system, we obtain a finite induced current along the magnetic field, which corresponds to the chiral magnetic effect. The obtained induced current is proportional to the magnetic field and to the chiral chemical potential, which is consistent with an analytical prediction.

Nuclear Physics and Lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beane, Silas

2003-11-01

Impressive progress is currently being made in computing properties and interac- tions of the low-lying hadrons using lattice QCD. However, cost limitations will, for the foreseeable future, necessitate the use of quark masses, Mq, that are signif- icantly larger than those of nature, lattice spacings, a, that are not significantly smaller than the physical scale of interest, and lattice sizes, L, that are not sig- nificantly larger than the physical scale of interest. Extrapolations in the quark masses, lattice spacing and lattice volume are therefore required. The hierarchy of mass scales is: L 1 j Mq j â ºC jmore » a 1 . The appropriate EFT for incorporating the light quark masses, the finite lattice spacing and the lattice size into hadronic observables is C-PT, which provides systematic expansions in the small parame- ters e m L, 1/ Lâ ºC, p/â ºC, Mq/â ºC and aâ ºC . The lattice introduces other unphysical scales as well. Lattice QCD quarks will increasingly be artificially separated« less

Critical end point in the presence of a chiral chemical potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Z. -F.; Cloët, I. C.; Lu, Y.

A class of Polyakov-loop-modified Nambu-Jona-Lasinio models has been used to support a conjecture that numerical simulations of lattice-regularized QCD defined with a chiral chemical potential can provide information about the existence and location of a critical end point in the QCD phase diagram drawn in the plane spanned by baryon chemical potential and temperature. That conjecture is challenged by conflicts between the model results and analyses of the same problem using simulations of lattice-regularized QCD (lQCD) and well-constrained Dyson-Schwinger equation (DSE) studies. We find the conflict is resolved in favor of the lQCD and DSE predictions when both a physicallymore » motivated regularization is employed to suppress the contribution of high-momentum quark modes in the definition of the effective potential connected with the Polyakov-loop-modified Nambu-Jona-Lasinio models and the four-fermion coupling in those models does not react strongly to changes in the mean field that is assumed to mock-up Polyakov-loop dynamics. With the lQCD and DSE predictions thus confirmed, it seems unlikely that simulations of lQCD with mu(5) > 0 can shed any light on a critical end point in the regular QCD phase diagram.« less

Topology (and axion's properties) from lattice QCD with a dynamical charm

NASA Astrophysics Data System (ADS)

Burger, Florian; Ilgenfritz, Ernst-Michael; Lombardo, Maria Paola; Müller-Preussker, Michael; Trunin, Anton

2017-11-01

We present results on QCD with four dynamical flavors in the temperature range 0.9 ≲ T /Tc ≲ 2. We have performed lattice simulations with Wilson fermions at maximal twist and measured the topological charge with gluonic and fermionic methods. The topological charge distribution is studied by means of its cumulants, which encode relevant properties of the QCD axion, a plausible Dark Matter candidate. The topological susceptibility measured with the fermionic method exhibits a power-law decay for T /Tc ≳ 2, with an exponent close to the one predicted by the Dilute Instanton Gas Approximation (DIGA). Close to Tc the temperature dependent effective exponent approaches the DIGA result from above, in agreement with recent analytic calculations. These results constrain the axion window, once an assumption on the fraction of axions contributing to Dark Matter is made.

Lee-Yang zero analysis for the study of QCD phase structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ejiri, Shinji

2006-03-01

We comment on the Lee-Yang zero analysis for the study of the phase structure of QCD at high temperature and baryon number density by Monte-Carlo simulations. We find that the sign problem for nonzero density QCD induces a serious problem in the finite volume scaling analysis of the Lee-Yang zeros for the investigation of the order of the phase transition. If the sign problem occurs at large volume, the Lee-Yang zeros will always approach the real axis of the complex parameter plane in the thermodynamic limit. This implies that a scaling behavior which would suggest a crossover transition will notmore » be obtained. To clarify this problem, we discuss the Lee-Yang zero analysis for SU(3) pure gauge theory as a simple example without the sign problem, and then consider the case of nonzero density QCD. It is suggested that the distribution of the Lee-Yang zeros in the complex parameter space obtained by each simulation could be more important information for the investigation of the critical endpoint in the (T,{mu}{sub q}) plane than the finite volume scaling behavior.« less

Strong Coupling Gauge Theories in LHC ERA

NASA Astrophysics Data System (ADS)

Fukaya, H.; Harada, M.; Tanabashi, M.; Yamawaki, K.

2011-01-01

AdS/QCD, light-front holography, and the nonperturbative running coupling / Stanley J. Brodsky, Guy de Teramond and Alexandre Deur -- New results on non-abelian vortices - Further insights into monopole, vortex and confinement / K. Konishi -- Study on exotic hadrons at B-factories / Toru Iijima -- Cold compressed baryonic matter with hidden local symmetry and holography / Mannque Rho -- Aspects of baryons in holographic QCD / T. Sakai -- Nuclear force from string theory / K. Hashimoto -- Integrating out holographic QCD back to hidden local symmetry / Masayasu Harada, Shinya Matsuzaki and Koichi Yamawaki -- Holographic heavy quarks and the giant Polyakov loop / Gianluca Grignani, Joanna Karczmarek and Gordon W. Semenoff -- Effect of vector-axial-vector mixing to dilepton spectrum in hot and/or dense matter / Masayasu Harada and Chihiro Sasaki -- Infrared behavior of ghost and gluon propagators compatible with color confinement in Yang-Mills theory with the Gribov horizon / Kei-Ichi Kondo -- Chiral symmetry breaking on the lattice / Hidenori Fukaya [for JLQCD and TWQCD collaborations] -- Gauge-Higgs unification: Stable Higgs bosons as cold dark matter / Yutaka Hosotani -- The limits of custodial symmetry / R. Sekhar Chivukula ... [et al.] -- Higgs searches at the tevatron / Kazuhiro Yamamoto [for the CDF and D[symbol] collaborations] -- The top triangle moose / R. S. Chivukula ... [et al.] -- Conformal phase transition in QCD like theories and beyond / V. A. Miransky -- Gauge-Higgs unification at LHC / Nobuhito Maru and Nobuchika Okada -- W[symbol]W[symbol] scattering in Higgsless models: Identifying better effective theories / Alexander S. Belyaev ... [et al.] -- Holographic estimate of Muon g - 2 / Deog Ki Hong -- Gauge-Higgs dark matter / T. Yamashita -- Topological and curvature effects in a multi-fermion interaction model / T. Inagaki and M. Hayashi -- A model of soft mass generation / J. Hosek -- TeV physics and conformality / Thomas Appelquist -- Conformal Higgs, or techni-dilaton - composite Higgs near conformality / Koichi Yamawaki -- Phase diagram of strongly interacting theories / Francesco Sannino -- Resizing conformal windows / O. Antipin and K. Tuominen -- Nearly conformal gauge theories on the lattice / Zoltan Fodor ... [et al.] -- Going beyond QCD in lattice gauge theory / G. T. Fleming -- Phases of QCD from small to large N[symbol]: (some) lattice results / A. Deuzeman, E. Pallante and M. P. Lombardo -- Lattice gauge theory and (quasi)-conformal technicolor / D. K. Sinclair and J. B. Kogut -- Study of the running coupling constant in 10-flavor QCD with the Schrodinger functional method / N. Yamada ... [et al.] -- Study of the running coupling in twisted Polyakov scheme / T. Aoyama ... [et al.].Running coupling in strong gauge theories via the lattice / Zoltan Fodor ... [et al.] -- Higgsinoless supersymmetry and hidden gravity / Michael L. Graesser, Ryuichiro Kitano and Masafumi Kurachi -- The latest status of LHC and the EWSB physics / S. Asai -- Continuum superpartners from supersymmetric unparticles / Hsin-Chia Cheng -- Review of minimal flavor constraints for technicolor / Hidenori S. Fukano and Francesco Sannino -- Standard model and high energy Lorentz violation / Damiano Anselmi -- Dynamical electroweak symmetry breaking and fourth family / Michio Hashimoto -- Holmorphic supersymmetric Nambu-Jona-Lasino model and dynamical electroweak symmetry breaking / Dong-Won Jung, Otto C. W. Kong and Jae Sik Lee -- Ratchet model of Baryogenesis / Tatsu Takeuchi, Azusa Minamizaki and Akio Sugamoto -- Classical solutions of field equations in Einstein Gauss-Bonnet gravity / P. Suranyi, C. Vaz and L. C. R. Wijewardhana -- Black holes constitute all dark matter / Paul H. Frampton -- Electroweak precision test and Z [symbol] in the three site Higgsless model / Tomohiro Abe -- Chiral symmetry and BRST symmetry breaking, quaternion reality and the lattice simulation / Sadataka Furui -- Holographic techni-dilaton, or conformal Higgs / Kazumoto Haba, Shinya Matsuzaki and Koichi Yamawaki -- Phase structure of topologically massive gauge theory with fermion / Yuichi Hoshino -- New regularization in extra dimensional model and renormalization group flow of the cosmological constant / Shoichi Ichinose -- Spectral analysis of dense two-color QCD / T. Kanazawa, T. Wettig and N. Yamamoto -- NJL model with dimensional regularization at finite temperature / T. Fujihara ... [et al.] -- A new method of evaluating the dynamical chiral symmetry breaking scale and the chiral restoration temperature in general gauge theories by using the non-perturbative renormalization group analyses with general 4-Fermi effective interaction space / Ken-Ichi Aoki, Daisuke Sato and Kazuhiro Miyashita -- The effective chiral Lagrangian with vector mesons and hadronic [symbol] decays / D. Kimura ... [et al.] -- Spontaneous SUSY breaking with anomalous U(1) symmetry in metastable vacua and moduli stabilization / Hiroyuki Nishino -- A new description of the lattice Yang-Mills theory and non-abelian magnetic monopole dominance in the string tension / Akihiro Shibata -- Thermodynamics with unbroken center symmetry in two-flavor QCD / S. Takemoto, M. Harada and C. Sasaki -- Masses of vector bosons in two-color QCD based on the hidden local symmetry / T. Yamaoka, M. Harada and C. Nonaka -- Walking dynamics from string duals / Maurizio Piai -- The quark mass dependence of the nucleon mass in AdS/QCD / Hyo Chul Ahn -- Structure of thermal quasi-fermion in QED/QCD from the Dyson-Schwinger equation / Hisao Nakkagawa -- Critical behaviors of sigma-mode and pion in holographic superconductors / Cheonsoo Park.

QCD and Asymptotic Freedom:. Perspectives and Prospects

NASA Astrophysics Data System (ADS)

Wilczek, Frank

QCD is now a mature theory, and it is possible to begin to view its place in the conceptual universe of physics with an appropriate perspective. There is a certain irony in the achievements of QCD. For the problems which initially drove its development — specifically, the desire to understand in detail the force that holds atomic nuclei together, and later the desire to calculate the spectrum of hadrons and their interactions — only limited insight has been achieved. However, I shall argue that QCD is actually more special and important a theory than one had any right to anticipate. In many ways, the importance of the solution transcends that of the original motivating problems. After elaborating on these quasiphilosophical remarks, I discuss two current frontiers of physics that illustrate the continuing vitality of the ideas. The recent wealth of beautiful precision experiments measuring the parameters of the standard model have made it possible to consider the unification of couplings in unprecedented quantitative detail. One central result emerging from these developments is a tantalizing hint of virtual supersymmetry. The possibility of phase transitions in matter at temperatures of order ~102 MeV, governed by QCD dynamics, is of interest from several points of view. Besides having a certain intrinsic grandeur, the question “Does the nature of matter change qualitatively, as it is radically heated?” is important for cosmology, relevant to planned high-energy heavy-ion collision experiments, and provides a promising arena for numerical simulations of QCD. Recent numerical work seems to be consistent with expectations suggested by renormalization group analysis of the potential universality classes of the QCD chiral phase transition; specifically, that the transition is second-order for two species of massless quarks but first order otherwise. There is an interesting possibility of long-range correlations in heavy ion collisions due to the creation of large regions of the misaligned chiral condensate. Finally, at the end, there is a brief discussion on the relation between scaling violations and running of the coupling. Some statements made later in the conference seemed to indicate that the relationship between these concepts is commonly misunderstood, so I’m smuggling this bit in even though it wasn’t part of the original talk.

Axial current generation by P-odd domains in QCD matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iatrakis, Ioannis; Yin, Yi; Lin, Shu

2015-06-23

The dynamics of topological domains which break parity (P) and charge-parity (CP) symmetry of QCD are studied. We derive in a general setting that those local domains will generate an axial current and quantify the strength of the induced axial current. Thus, our findings are verified in a top-down holographic model. The relation between the real time dynamics of those local domains and the chiral magnetic field is also elucidated. We finally argue that such an induced axial current would be phenomenologically important in a heavy-ion collisions experiment.

Bottomonium above deconfinement in lattice nonrelativistic QCD.

PubMed

Aarts, G; Kim, S; Lombardo, M P; Oktay, M B; Ryan, S M; Sinclair, D K; Skullerud, J-I

2011-02-11

We study the temperature dependence of bottomonium for temperatures in the range 0.4T(c) < T < 2.1T(c), using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simulations for Nf = 2 light flavors on a highly anisotropic lattice. We find that the Υ is insensitive to the temperature in this range, while the χb propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behavior consistent with nearly free dynamics at T ≃ 2T(c).

Highly excited and exotic meson spectrum from dynamical lattice QCD.

PubMed

Dudek, Jozef J; Edwards, Robert G; Peardon, Michael J; Richards, David G; Thomas, Christopher E

2009-12-31

Using a new quark-field construction algorithm and a large variational basis of operators, we extract a highly excited isovector meson spectrum on dynamical anisotropic lattices. We show how carefully constructed operators can be used to reliably identify the continuum spin of extracted states, overcoming the reduced cubic symmetry of the lattice. Using this method we extract, with confidence, excited states, states with exotic quantum numbers (0+-, 1-+, and 2+-), and states of high spin, including, for the first time in lattice QCD, spin-four states.

The gluon density of the proton at low x from a QCD analysis of F2

NASA Astrophysics Data System (ADS)

Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Baehr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Brasse, F.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Colombo, M.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Delcourt, B.; Del Buono, L.; De Roeck, A.; De Wolf, E. A.; Di Nezza, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Ehrlichmann, H.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gebauer, M.; Gellrich, A.; Genzel, H.; Gerhards, R.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Gonzalez-Pineiro, B.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Hampel, M.; Hanlon, E. M.; Hapke, M.; Haynes, W. J.; Heatherington, J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hildesheim, W.; Hill, P.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Horisberger, R.; Hudgson, V. L.; Huet, Ph.; Hütte, M.; Hufnagel, H.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kant, D.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Krüner-Marquis, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Lanius, P.; Laporte, J.-F.; Lebedev, A.; Leverenz, C.; Levonian, S.; Ley, Ch.; Lindner, A.; Lindström, G.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lohmander, H.; Lomas, J.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Migliori, A.; Mikocki, S.; Milstead, D.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Ozerov, D.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Peppel, E.; Perez, E.; Phillips, J. P.; Pichler, Ch.; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Prosi, R.; Rabbertz, K.; Rädel, G.; Raupach, F.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Rick, H.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Rylko, R.; Sahlmann, N.; Sanchez, E.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Schwind, A.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Starosta, R.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stiewe, J.; Stösslein, U.; Stolze, K.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Truöl, P.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Van Esch, P.; Van Mechelen, P.; Vartapetian, A.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walker, I. W.; Walther, A.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wright, A. E.; Wünsch, E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zimmer, M.; Zimmermann, W.; Zomer, F.; Zuber, K.; H1 Collaboration

1995-02-01

We present a QCD analysis of the proton structure function F2 measured by the H1 experiment at HERA, combined with data from previous fixed target experiments. The gluon density is extracted from the scaling violations of F2 in the range 2 · 10 -4 < x < 3 · 10 -2 and compared with an approximate solution of the QCD evolution equations. The gluon density is found to rise steeply with decreasing x.

Two loop renormalization of the magnetic coupling in hot QCD

NASA Astrophysics Data System (ADS)

Giovannangeli, P.

2004-04-01

Well above the critical temperature hot QCD is described by 3d electrostatic QCD with gauge coupling gE and Debye mass mE. We integrate out the Debye scales to two loop accuracy and find for the gauge coupling in the resulting magnetostatic action gM2=gE21-{1}/{48}{gE2N}/{πmE}-{17}/{4608}{gE2N}/{πmE}2+O{gE2N}/{πmE}3.

Fragmentation functions at next-to-next-to-leading order accuracy

DOE PAGES

Anderle, Daniele P.; Stratmann, Marco; Ringer, Felix

2015-12-01

We present a first analysis of parton-to-pion fragmentation functions at next-to-next-to-leading order accuracy in QCD based on single-inclusive pion production in electron-positron annihilation. Special emphasis is put on the technical details necessary to perform the QCD scale evolution and cross section calculation in Mellin moment space. Lastly, we demonstrate how the description of the data and the theoretical uncertainties are improved when next-to-next-to-leading order QCD corrections are included.

QCD compositeness as revealed in exclusive vector boson reactions through double-photon annihilation: e +e - →γγ* → γV 0 and e +e - γ*γ* V$$0\\atop{a}$$V$$0\\atop{b}$$

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

We study the exclusive double-photon annihilation processes, e +e - →γγ* → γV 0 and e +e - γ*γ* Vmore » $$0\\atop{a}$$V$$0\\atop{b}$$, where the V$$0\\atop{i}$$ is a neutral vector meson produced in the forward kinematical region: s>> -t and -t >> Λ$$2\\atop{QCD}$$. We show how the differential cross sections $$dσ\\atop{dt}$$, as predicted by QCD, have additional falloff in the momentum transfer squared t due to the QCD compositeness of the hadrons, consistent with the leading-twist fixed-θ CM scaling laws, both in terms of conventional Feynman diagrams and by using the AdS/QCD holographic model to obtain the results more transparently. However, even though they are exclusive channels and not associated with the conventional electron–positron annihilation process e +e -→γ*→ $$q\\bar{q}$$, these total cross sections σ(e +e -→γV 0)and σ(e +e -→V$$0\\atop{a}$$V$$0\\atop{b}$$), integrated over the dominant forward-and backward-θ CM angular domains, scale as 1/s, and thus contribute to the leading-twist scaling behavior of the ratio R e+e-. We generalize these results to exclusive double-electroweak vector-boson annihilation processes accompanied by the forward production of hadrons, such as e +e -→Z 0V 0and e +e -→W -ρ +. These results can also be applied to the exclusive production of exotic hadrons such as tetraquarks, where the cross-section scaling behavior can reveal their multiquark nature.« less

QCD compositeness as revealed in exclusive vector boson reactions through double-photon annihilation: e +e - →γγ* → γV 0 and e +e - γ*γ* V$$0\\atop{a}$$V$$0\\atop{b}$$

DOE PAGES

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

2017-01-01

We study the exclusive double-photon annihilation processes, e +e - →γγ* → γV 0 and e +e - γ*γ* Vmore » $$0\\atop{a}$$V$$0\\atop{b}$$, where the V$$0\\atop{i}$$ is a neutral vector meson produced in the forward kinematical region: s>> -t and -t >> Λ$$2\\atop{QCD}$$. We show how the differential cross sections $$dσ\\atop{dt}$$, as predicted by QCD, have additional falloff in the momentum transfer squared t due to the QCD compositeness of the hadrons, consistent with the leading-twist fixed-θ CM scaling laws, both in terms of conventional Feynman diagrams and by using the AdS/QCD holographic model to obtain the results more transparently. However, even though they are exclusive channels and not associated with the conventional electron–positron annihilation process e +e -→γ*→ $$q\\bar{q}$$, these total cross sections σ(e +e -→γV 0)and σ(e +e -→V$$0\\atop{a}$$V$$0\\atop{b}$$), integrated over the dominant forward-and backward-θ CM angular domains, scale as 1/s, and thus contribute to the leading-twist scaling behavior of the ratio R e+e-. We generalize these results to exclusive double-electroweak vector-boson annihilation processes accompanied by the forward production of hadrons, such as e +e -→Z 0V 0and e +e -→W -ρ +. These results can also be applied to the exclusive production of exotic hadrons such as tetraquarks, where the cross-section scaling behavior can reveal their multiquark nature.« less

Total γ ⋆ }γ {⋆ cross section and the QCD dipole picture

NASA Astrophysics Data System (ADS)

Bialas, A.; Czyz, W.; Florkowski, W.

1998-05-01

In the framework of the dipole picture of the BFKL pomeron we discuss two possibilities of calculating the total γ^{star}γ^{star} cross section of the virtual photons. It is shown that the dipole model reproduces the results obtained earlier from k_T-factorization up to the selection of the scale determining the length of the QCD cascade. The choice of scale turns out to be important for the numerical outcome of the calculations.

Higgs boson couplings to bottom quarks: two-loop supersymmetry-QCD corrections.

PubMed

Noth, David; Spira, Michael

2008-10-31

We present two-loop supersymmetry (SUSY) QCD corrections to the effective bottom Yukawa couplings within the minimal supersymmetric extension of the standard model (MSSM). The effective Yukawa couplings include the resummation of the nondecoupling corrections Deltam_{b} for large values of tanbeta. We have derived the two-loop SUSY-QCD corrections to the leading SUSY-QCD and top-quark-induced SUSY-electroweak contributions to Deltam_{b}. The scale dependence of the resummed Yukawa couplings is reduced from O(10%) to the percent level. These results reduce the theoretical uncertainties of the MSSM Higgs branching ratios to the accuracy which can be achieved at a future linear e;{+}e;{-} collider.

Quark–gluon plasma phenomenology from anisotropic lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skullerud, Jon-Ivar; Kelly, Aoife; Aarts, Gert

The FASTSUM collaboration has been carrying out simulations of N{sub f} = 2 + 1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.

QCD and Multiparticle Production - Proceedings of the XXIX International Symposium on Multiparticle Dynamics

NASA Astrophysics Data System (ADS)

Sarcevic, Ina; Tan, Chung-I.

2000-07-01

The Table of Contents for the full book PDF is as follows: * Preface * Monday morning session: Hadronic Final States - Conveners: E. de Wolf and J. W. Gary * Session Chairman: J. W. Gary * Inclusive Jets at the Tevatron * Forward Jets, Dijets, and Subjets at the Tevatron * Inclusive Hadron Production and Dijets at HERA * Recent Opal Results on Photon Structure and Interactions * Review of Two-Photon Physics at LEP * Session Chairman: E. de Wolf * An Intriguing Area-Law-Based Hadron Production Scheme in e+e- Annihilation and Its Possible Extensions * Hyperfine Splitting in Hadron Production at High Energies * Event Selection Effects on Multiplicities in Quark and Gluon Jets * Quark and Gluon Jet Properties at LEP * Rapidity Gaps in Quark and Gluon Jets -- A Perturbative Approach * Monday afternoon session: Diffractive and Small-x - Conveners: M. Derrick and A. White * Session Chairman: A. White * Structure Functions: Low x, High y, Low Q2 * The Next-to-Leading Dynamics of the BFKL Pomeron * Renormalization Group Improved BFKL Equation * Session Chairman: G. Briskin * New Experimental Results on Diffraction at HERA * Diffractive Parton Distributions in Light-Cone QCD * The Logarithmic Derivative of the F2 Structure Function and Saturation * Spin Dependence of Diffractive DIS * Monday evening session * Session Chairman: M. Braun * Tests of QCD with Particle Production at HERA: Review and Outlook * Double Parton Scattering and Hadron Structure in Transverse Space * The High Density Parton Dynamics from Eikonal and Dipole Pictures * Hints of Higher Twist Effects in the Slope of the Proton Structure Function * Tuesday morning session: Correlations and Fluctuations - Conveners: R. Hwa and M. Tannenbaum * Session Chairman: A. Giovannini -- Fluctuations and Correlations * Bose-Einstein Results from L3 * Short-Range and Long-Range Correlations in DIS at HERA * Coior Mutation Model, Intermittency, and Erraticity * QCD Queuing and Hadron Multiplicity * Soft and Semi-hard Components in Multiplicity Distributions in the TeV Region * Qualitative Difference Between Particle Production Dynamics in Soft and Hard Processes * Session Chairman: M. Tannenbaum -- Bose-Einstein Correlations * Questions in Bose-Einstein Correlations * The Source Size Dependence on the mhadron Applying Fermi and Bose Statistics and I-Spin Invariance * Signal of Partial UA(1) Symmetry Restoration from Two-Pion Bose-Einstein Correlations * Multiparticle Bose-Einstein Correlations in Heavy-Ion Collisions * Tuesday afternoon session: Heavy Ion Collisions - Conveners: B. Müller and J. Statchel * Session Chairman: J. Stachel * Probing Baryon Freeze-out Density at the AGS with Proton Correlations * Centrality Dependence of Hadronic Observables at CERN SPS * Study of Transverse Momentum Spectra in pp Collisions with a Statistical Model of Hadronisation * Session Chairman: B. Brower * Production of Light (Anti-)Nuclei with E864 at the AGS * QCD Critical Point in Heavy-Ion Collision Experiments * Tuesday evening session * Session Chairman: H. M. Fried * Oscillating Hq, Event Shapes, and QCD * Critical Behavior of Quark-Hadron Phase Transition * Shadowing of Gluons at RHIC and LHC * Parton Distributions in Nuclei at Small x * Wednesday morning session: Diffraction and Small x - Conveners: M. Derrick and A. White * Session Chairman: C. Pajares * High-Energy Effective Action from Scattering of Shock Waves in QCD * The Triangle Anomaly in the Triple-Regge Limit * CDF Results on Hard Diffraction and Rapidity Gap Physics * DØ Results on Hard Diffraction * Interjet Rapidity Gaps in Perturbative QCD * Pomeron: Beyond the Standard Approach * Factorization and Diffractive Production at Collider Energies * Thursday morning session: Heavy Ion Collisions - Conveners: B. Müller and J. B. Stachel * Session Chairman: N. Schmitz * Summary of J/ψ Suppression Data and Preliminary Results on Multiplicity Distributions in PB-PB Collisions from the NA50 Experiment * Duality and Chiral Restoration from Dilepton Production in Relativistic Heavy-Ion Collisions * Session Chairman: I. Sarcevic * Transport-Theoretical Analysis of Reaction Dynamics, Particle Production and Freeze-out at RHIC * Inclusive Particle Spectra and Exotic Particle Searches Using STAR * The First Fermi in a High Energy Nuclear Collision * Probing the Space-Time Evolution of Heavy Ion Collisions with Bremsstrahlung * Thursday afternoon session: Hadronic Final States - Conveners: E. de Wolf and J. Gary * Session Chairman: F. Verbeure * QCD with SLD * QCD at LEP II * Multidimensional Analysis of the Bose-Einstein Correlations at DELPHI * Study of Color Singlet with Gluonic Subsinglet by Color Effective Hamiltonian * Correlations and Fluctuations - Conveners: R. Hwa and M. Tannenbaum * Session Chairman: R. C. Hwa -- Fluctuations in Heavy-Ion Collisions * Scale-Local Statistical Measures and the Multiparticle Final State * Centrality and ET Fluctuations from p + Be to Au + Au at AGS Energies * Order Parameter of Single Event * Multiplicities, Transverse Momenta and Their Correlations from Percolating Colour Strings * Probing the QCD Critical Point in Nuclear Collisions * Event-by-Event Fluctuations in Pb + Pb Collisions at the CERN SPS * Friday morning session: High Energy Collisions and Cosmic-Ray/Astrophysics - Conveners: F. Halzen and T. Stanev * Session Chairman: U. Sukhatme * Rethinking the Eikonal Approximation * QCD and Total Cross-Sections * The Role of Multiple Parton Collisions in Hadron Collisions * Effective Cross Sections and Spatial Structure of the Hadrons * Looking for the Odderon * QCD in Embedded Coordinates * Session Chairman: F. Bopp * Extensive Air Sbowers and Hadronic Interaction Models * Penetration of the Earth by Ultrahigh Energy Neutrinos and the Parton Distributions Inside the Nucleon * Comparison of Prompt Muon Observations to Charm Expectations * Friday afternoon session: Recent Developments - Conveners: R. Brower and I. Sarcevic * Session Chairman: G. Guralnik * The Relation Between Gauge Theories and Gravity * From Black Holes to Pomeron: Tensor Glueball and Pomeron Intercept at Strong Coupling * Summary Talks * Summary of Results of the Ultrarelativistic Heavy Ion Fixed Target Program * Review of Theory Talks * Summary of Experimental Talks * List of Participants

Hadron interactions and exotic hadrons from lattice QCD

NASA Astrophysics Data System (ADS)

Ikeda, Yoichi

2014-09-01

One of the interesting subjects in hadron physics is to look for the multiquark configurations. One of candidates is the H-dibaryon (udsuds), and the possibility of the bound H-dibaryon has been recently studied from lattice QCD. We also extend the HAL QCD method to define potentials on the lattice between baryons to meson-meson systems including charm quarks to search for the bound tetraquark Tcc (ud c c) and Tcs (ud c s). In the presentation, after reviewing the HAL QCD method, we report the results on the H-dibaryon, the tetraquark Tcc (ud c c) and Tcs (ud c s), where we have employed the relativistic heavy quark action to treat the charm quark dynamics with pion masses, mπ = 410, 570, 700 MeV.

Scattering processes and resonances from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briceno, Raul A.; Dudek, Jozef J.; Young, Ross D.

The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lightermore » hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This paper reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. Finally, the challenges which currently limit the field are discussed along with the steps being taken to resolve them.« less

Scattering processes and resonances from lattice QCD

NASA Astrophysics Data System (ADS)

Briceño, Raúl A.; Dudek, Jozef J.; Young, Ross D.

2018-04-01

The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This article reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.

Scattering processes and resonances from lattice QCD

DOE PAGES

Briceno, Raul A.; Dudek, Jozef J.; Young, Ross D.

2018-04-18

The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lightermore » hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This paper reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. Finally, the challenges which currently limit the field are discussed along with the steps being taken to resolve them.« less

Concerns Expressed by Parents of Children with Pervasive Developmental Disorders for Different Time Periods of the Day: A Case–Control Study

PubMed Central

Sasaki, Yoshinori; Usami, Masahide; Sasayama, Daimei; Okada, Takashi; Iwadare, Yoshitaka; Watanabe, Kyota; Ushijima, Hirokage; Tanaka, Tetsuya; Harada, Maiko; Tanaka, Hiromi; Kodaira, Masaki; Sugiyama, Nobuhiro; Sawa, Tetsuji; Saito, Kazuhiko

2015-01-01

Background/Aim The Questionnaire: Children with Difficulties (QCD) is a parent-assessed questionnaire designed to evaluate child’s difficulties in functioning during specific periods of the day. This study aimed to evaluate difficulties in daily functioning of children and adolescents with pervasive developmental disorder (PDD) using the QCD. Results were compared with those for a community sample. Methods A case–control design was used. The cases comprised elementary school students (182 males, 51 females) and junior high school students (100 males, 39 females) with PDD, whereas a community sample of elementary school students (568 males, 579 females) and junior high school students (180 males, 183 females) was enrolled as controls. Their behavior was assessed using the QCD, the Tokyo Autistic Behavior Scale (TABS), the ADHD-rating scale (ADHD-RS), and the Oppositional Defiant Behavior Inventory (ODBI) for elementary and junior high school students, respectively. Effects of gender and diagnosis on the QCD scores were analyzed. Correlation coefficients between QCD and TABS, ADHD-RS, and ODBI scores were analyzed. Results The QCD scores for the children with PDD were significantly lower compared with those from the community sample (P < 0.001). Significantly strong correlations were observed in more areas of the ADHD-RS and ODBI scores compared with the TABS scores. Conclusions Children with PDD experienced greater difficulties in completing basic daily activities; moreover, their QCD scores revealed stronger associations with their ADHD-RS and ODBI scores in comparison with their TABS scores. The difficulties of PDD, ADHD and OBDI symptoms combined in children makes it necessary to assess all diagnoses before any therapy for PDD is initiated in order to be able to evaluate its results properly. PMID:25898260

Higgs boson gluon-fusion production in QCD at three loops.

PubMed

Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Herzog, Franz; Mistlberger, Bernhard

2015-05-29

We present the cross section for the production of a Higgs boson at hadron colliders at next-to-next-to-next-to-leading order (N^{3}LO) in perturbative QCD. The calculation is based on a method to perform a series expansion of the partonic cross section around the threshold limit to an arbitrary order. We perform this expansion to sufficiently high order to obtain the value of the hadronic cross at N^{3}LO in the large top-mass limit. For renormalization and factorization scales equal to half the Higgs boson mass, the N^{3}LO corrections are of the order of +2.2%. The total scale variation at N^{3}LO is 3%, reducing the uncertainty due to missing higher order QCD corrections by a factor of 3.

Baryogenesis from strong CP violation and the QCD axion.

PubMed

Servant, Géraldine

2014-10-24

We show that strong CP violation from the QCD axion can be responsible for the matter antimatter asymmetry of the Universe in the context of cold electroweak baryogenesis if the electroweak phase transition is delayed below the GeV scale. This can occur naturally if the Higgs couples to a O(100)  GeV dilaton, as expected in some models where the Higgs is a pseudo-Nambu-Goldstone boson of a new strongly interacting sector at the TeV scale. The existence of such a second scalar resonance with a mass and properties similar to the Higgs boson will soon be tested at the LHC. In this context, the QCD axion would not only solve the strong CP problem, but also the matter antimatter asymmetry and dark matter.

Flavor-singlet spectrum in multi-flavor QCD

NASA Astrophysics Data System (ADS)

Aoki, Yasumichi; Aoyama, Tatsumi; Bennett, Ed; Kurachi, Masafumi; Maskawa, Toshihide; Miura, Kohtaroh; Nagai, Kei-ichi; Ohki, Hiroshi; Rinaldi, Enrico; Shibata, Akihiro; Yamawaki, Koichi; Yamazaki, Takeshi

2018-03-01

Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.

Flavor-singlet spectrum in multi-flavor QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, Yasamichi; Rinaldi, Enrico

2017-06-18

Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixedmore » number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.« less

Collective Perspective on Advances in Dyson—Schwinger Equation QCD

NASA Astrophysics Data System (ADS)

Adnan, Bashir; Chang, Lei; Ian, C. Cloët; Bruno, El-Bennich; Liu, Yu-Xin; Craig, D. Roberts; Peter, C. Tandy

2012-07-01

We survey contemporary studies of hadrons and strongly interacting quarks using QCD's Dyson—Schwinger equations, addressing the following aspects: confinement and dynamical chiral symmetry breaking; the hadron spectrum; hadron elastic and transition form factors, from small- to large-Q2; parton distribution functions; the physics of hadrons containing one or more heavy quarks; and properties of the quark gluon plasma.

QCD in heavy quark production and decay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiss, J.

1997-06-01

The author discusses how QCD is used to understand the physics of heavy quark production and decay dynamics. His discussion of production dynamics primarily concentrates on charm photoproduction data which are compared to perturbative QCD calculations which incorporate fragmentation effects. He begins his discussion of heavy quark decay by reviewing data on charm and beauty lifetimes. Present data on fully leptonic and semileptonic charm decay are then reviewed. Measurements of the hadronic weak current form factors are compared to the nonperturbative QCD-based predictions of Lattice Gauge Theories. He next discusses polarization phenomena present in charmed baryon decay. Heavy Quark Effectivemore » Theory predicts that the daughter baryon will recoil from the charmed parent with nearly 100% left-handed polarization, which is in excellent agreement with present data. He concludes by discussing nonleptonic charm decay which is traditionally analyzed in a factorization framework applicable to two-body and quasi-two-body nonleptonic decays. This discussion emphasizes the important role of final state interactions in influencing both the observed decay width of various two-body final states as well as modifying the interference between interfering resonance channels which contribute to specific multibody decays. 50 refs., 77 figs.« less

Anomalous leptonic U(1) symmetry: Syndetic origin of the QCD axion, weak-scale dark matter, and radiative neutrino mass

NASA Astrophysics Data System (ADS)

Ma, Ernest; Restrepo, Diego; Zapata, Óscar

2018-01-01

The well-known leptonic U(1) symmetry of the Standard Model (SM) of quarks and leptons is extended to include a number of new fermions and scalars. The resulting theory has an invisible QCD axion (thereby solving the strong CP problem), a candidate for weak-scale dark matter (DM), as well as radiative neutrino masses. A possible key connection is a color-triplet scalar, which may be produced and detected at the Large Hadron Collider.

PREFACE: Focus section on Hadronic Physics Focus section on Hadronic Physics

NASA Astrophysics Data System (ADS)

Roberts, Craig; Swanson, Eric

2007-07-01

Hadronic physics is the study of strongly interacting matter and its underlying theory, Quantum Chromodynamics (QCD). The field had its beginnings after World War Two, when hadrons were discovered in ever increasing numbers. Today, it encompasses topics like the quark-gluon structure of hadrons at varying scales, the quark-gluon plasma and hadronic matter at extreme temperature and density; it also underpins nuclear physics and has significant impact on particle physics, astrophysics, and cosmology. Among the goals of hadronic physics are to determine the parameters of QCD, understand the origin and characteristics of confinement, understand the dynamics and consequences of dynamical chiral symmetry breaking, explore the role of quarks and gluons in nuclei and in matter under extreme conditions and understand the quark and gluon structure of hadrons. In general, the process is one of discerning the relevant degrees of freedom and relating these to the fundamental fields of QCD. The emphasis is on understanding QCD, rather than testing it. The papers gathered in this special focus section of Journal of Physics G: Nuclear and Particle Physics attempt to cover this broad range of subjects. Alkofer and Greensite examine the issue of quark and gluon confinement with the focus on models of the QCD vacuum, lattice gauge theory investigations, and the relationship to the AdS/CFT correspondence postulate. Arrington et al. review nucleon form factors and their role in determining quark orbital momentum, the strangeness content of the nucleon, meson cloud effects, and the transition from nonperturbative to perturbative QCD dynamics. The physics associated with hadronic matter at high temperature and density and at low Bjorken-x at the Relativistic Heavy Ion Collider (RHIC), the SPS at CERN, and at the future LHC is summarized by d'Enterria. The article of Lee and Smith examines experiment and theory associated with electromagnetic meson production from nucleons and illustrates how the structure of the nucleon is revealed. Reimer reviews how the Drell--Yan process can be used to explore the sea quark structure of nucleons, thereby probing such phenomena as flavour asymmetry in the nucleon and nuclear medium modification of nucleon properties. The exploitation of the B factories has led to a resurgence of interest in heavy quark spectroscopy. Concurrently, interest in light quark spectroscopy and gluonic excitations remains high, with several new experimental efforts in the planning or building stages. The current status of all of this is reviewed by Rosner. Finally, Vogelsang summarizes the status of polarized deep inelastic lepton-nucleon scattering experiments at RHIC and their impact on the theoretical understanding of nucleon helicity structure, gluon polarization in the nucleus, and transverse spin asymmetries. Of course, hadronic physics is a much broader subject than can be conveyed in this special focus section; advances in effective field theory, lattice gauge theory, generalised parton distributions and many other subfields are not covered here. Nevertheless, we hope that this focus section will help the reader appreciate the vitality, breadth of endeavour, and the phenomenological richness of hadronic physics.

Multiscale solvers and systematic upscaling in computational physics

NASA Astrophysics Data System (ADS)

Brandt, A.

2005-07-01

Multiscale algorithms can overcome the scale-born bottlenecks that plague most computations in physics. These algorithms employ separate processing at each scale of the physical space, combined with interscale iterative interactions, in ways which use finer scales very sparingly. Having been developed first and well known as multigrid solvers for partial differential equations, highly efficient multiscale techniques have more recently been developed for many other types of computational tasks, including: inverse PDE problems; highly indefinite (e.g., standing wave) equations; Dirac equations in disordered gauge fields; fast computation and updating of large determinants (as needed in QCD); fast integral transforms; integral equations; astrophysics; molecular dynamics of macromolecules and fluids; many-atom electronic structures; global and discrete-state optimization; practical graph problems; image segmentation and recognition; tomography (medical imaging); fast Monte-Carlo sampling in statistical physics; and general, systematic methods of upscaling (accurate numerical derivation of large-scale equations from microscopic laws).

Peccei-Quinn relaxion

NASA Astrophysics Data System (ADS)

Jeong, Kwang Sik; Shin, Chang Sub

2018-01-01

The relaxation mechanism, which solves the electroweak hierarchy problem without relying on TeV scale new physics, crucially depends on how a Higgs-dependent back-reaction potential is generated. In this paper, we suggest a new scenario in which the scalar potential induced by the QCD anomaly is responsible both for the relaxation mechanism and the Peccei-Quinn mechanism to solve the strong CP problem. The key idea is to introduce the relaxion and the QCD axion whose cosmic evolutions become quite different depending on an inflaton-dependent scalar potential. Our scheme raises the cutoff scale of the Higgs mass up to 107 GeV, and allows reheating temperature higher than the electroweak scale as would be required for viable cosmology. In addition, the QCD axion can account for the observed dark matter of the universe as produced by the conventional misalignment mechanism. We also consider the possibility that the couplings of the Standard Model depend on the inflaton and become stronger during inflation. In this case, the relaxation can be implemented with a sub-Planckian field excursion of the relaxion for a cutoff scale below 10 TeV.

Going Beyond QCD in Lattice Gauge Theory

NASA Astrophysics Data System (ADS)

Fleming, G. T.

2011-01-01

Strongly coupled gauge theories (SCGT's) have been studied theoretically for many decades using numerous techniques. The obvious motivation for these efforts stemmed from a desire to understand the source of the strong nuclear force: Quantum Chromo-dynamics (QCD). Guided by experimental results, theorists generally consider QCD to be a well-understood SCGT. Unfortunately, it is not clear how to extend the lessons learned from QCD to other SCGT's. Particularly urgent motivators for new studies of other SCGT's are the ongoing searches for physics beyond the standard model (BSM) at the Large Hadron Collider (LHC) and the Tevatron. Lattice gauge theory (LGT) is a technique for systematically-improvable calculations in many SCGT's. It has become the standard for non-perturbative calculations in QCD and it is widely believed that it may be useful for study of other SCGT's in the realm of BSM physics. We will discuss the prospects and potential pitfalls for these LGT studies, focusing primarily on the flavor dependence of SU(3) gauge theory.

Testing Quantum Chromodynamics with Antiprotons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, S.

2004-10-21

The antiproton storage ring HESR to be constructed at GSI will open up a new range of perturbative and nonperturbative tests of QCD in exclusive and inclusive reactions. I discuss 21 tests of QCD using antiproton beams which can illuminate novel features of QCD. The proposed experiments include the formation of exotic hadrons, measurements of timelike generalized parton distributions, the production of charm at threshold, transversity measurements in Drell-Yan reactions, and searches for single-spin asymmetries. The interactions of antiprotons in nuclear targets will allow tests of exotic nuclear phenomena such as color transparency, hidden color, reduced nuclear amplitudes, and themore » non-universality of nuclear antishadowing. The central tool used in these lectures are light-front Fock state wavefunctions which encode the bound-state properties of hadrons in terms of their quark and gluon degrees of freedom at the amplitude level. The freedom to choose the light-like quantization four-vector provides an explicitly covariant formulation of light-front quantization and can be used to determine the analytic structure of light-front wave functions. QCD becomes scale free and conformally symmetric in the analytic limit of zero quark mass and zero {beta} function. This ''conformal correspondence principle'' determines the form of the expansion polynomials for distribution amplitudes and the behavior of non-perturbative wavefunctions which control hard exclusive processes at leading twist. The conformal template also can be used to derive commensurate scale relations which connect observables in QCD without scale or scheme ambiguity. The AdS/CFT correspondence of large N{sub C} supergravity theory in higher-dimensional anti-de Sitter space with supersymmetric QCD in 4-dimensional space-time has important implications for hadron phenomenology in the conformal limit, including the nonperturbative derivation of counting rules for exclusive processes and the behavior of structure functions at large x{sub bj}. String/gauge duality also predicts the QCD power-law fall-off of light-front Fock-state hadronic wavefunctions with arbitrary orbital angular momentum at high momentum transfer. I also review recent work which shows that the diffractive component of deep inelastic scattering, single spin asymmetries, as well as nuclear shadowing and antishadowing, cannot be computed from the LFWFs of hadrons in isolation.« less

QCD for Postgraduates (3/5)

ScienceCinema

Zanderighi, Giulia

2018-04-27

Modern QCD - Lecture 3 We will introduce processes with initial-state hadrons and discuss parton distributions, sum rules, as well as the need for a factorization scale once radiative corrections are taken into account. We will then discuss the DGLAP equation, the evolution of parton densities, as well as ways in which parton densities are extracted from data.

Inducing the Einstein action in QCD-like theories

NASA Astrophysics Data System (ADS)

Donoghue, John F.; Menezes, Gabriel

2018-03-01

We evaluate the induced value of Newton's constant which would arise in QCD. The ingredients are modern lattice results, perturbation theory and the operator product expansion. The resulting shift in the Planck mass is positive. A scaled-up version of such a theory may be part of a quantum field theory treatment of gravity.

Lepton-rich cold QCD matter in protoneutron stars

NASA Astrophysics Data System (ADS)

Jiménez, J. C.; Fraga, E. S.

2018-05-01

We investigate protoneutron star matter using the state-of-the-art perturbative equation of state for cold and dense QCD in the presence of a fixed lepton fraction in which both electrons and neutrinos are included. Besides computing the modifications in the equation of state due to the presence of trapped neutrinos, we show that stable strange quark matter has a more restricted parameter space. We also study the possibility of nucleation of unpaired quark matter in the core of protoneutron stars by matching the lepton-rich QCD pressure onto a hadronic equation of state, namely TM1 with trapped neutrinos. Using the inherent dependence of perturbative QCD on the renormalization scale parameter, we provide a measure of the uncertainty in the observables we compute.

Gluons and the Quark Sea at High Energies: Distributions, Polarization, Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boer, Daniel; /Groningen U.; Diehl, Markus

2012-06-07

This report on the science case for an Electron-Ion Collider (EIC) is the result of a ten-week program at the Institute for Nuclear Theory (INT) in Seattle (from September 13-November 19, 2010), motivated by the need to develop a strong case for the continued study of the QCD description of hadron structure in the coming decades. Hadron structure in the valence quark region will be studied extensively with the Jefferson Lab 12 GeV science program, the subject of an INT program the previous year. The focus of the INT program was on understanding the role of gluons and sea quarks,more » the important dynamical degrees of freedom describing hadron structure at high energies. Experimentally, the most direct and precise way to access the dynamical structure of hadrons and nuclei at high energies is with a high luminosity lepton probe in collider mode. An EIC with optimized detectors offers enormous potential as the next generation accelerator to address many of the most important, open questions about the fundamental structure of matter. The goal of the INT program, as captured in the writeups in this report, was to articulate these questions and to identify golden experiments that have the greatest potential to provide definitive answers to these questions. At resolution scales where quarks and gluons become manifest as degrees of freedom, the structure of the nucleon and of nuclei is intimately connected with unique features of QCD dynamics, such as confinement and the self-coupling of gluons. Information on hadron sub-structure in DIS is obtained in the form of 'snapshots' by the 'lepton microscope' of the dynamical many-body hadron system, over different momentum resolutions and energy scales. These femtoscopic snapshots, at the simplest level, provide distribution functions which are extracted over the largest accessible kinematic range to assemble fundamental dynamical insight into hadron and nuclear sub-structure. For the proton, the EIC would be the brightest femtoscope scale lepton-collider ever, exceeding the intensity of the HERA collider a thousand fold. HERA, with its center-of-mass (CM) energy of 320 GeV, was built to search for quark substructure. An EIC, with its scientific focus on studying QCD in the regime where the sea quarks and gluons dominate, would have a lower CM energy. In a staged EIC design, the CM energy will range from 50-70 GeV in stage I to approximately twice that for the full design. In addition to being the first lepton collider exploring the structure of polarized protons, an EIC will also be the first electron-nucleus collider, probing the gluon and sea quark structure of nuclei for the first time. Following the same structure as the scientific discussions at the INT, this report is organized around the following four major themes: (1) The spin and flavor structure of the proton; (2) Three dimensional structure of nucleons and nuclei in momentum and configuration space; (3) QCD matter in nuclei; and (4) Electroweak physics and the search for physics beyond the Standard Model. In this executive summary, we will briefly outline the outstanding physics questions in these areas and the suite of measurements that are available with an EIC to address these. The status of accelerator and detector designs is addressed at the end of the summary. Tables of golden measurements for each of the key science areas outlined are presented on page 12. In addition, each chapter in the report contains a comprehensive overview of the science topic addressed. Interested readers are encouraged to read these and the individual contributions for more details on the present status of EIC science.« less

Determination of the chiral condensate from (2+1)-flavor lattice QCD.

PubMed

Fukaya, H; Aoki, S; Hashimoto, S; Kaneko, T; Noaki, J; Onogi, T; Yamada, N

2010-03-26

We perform a precise calculation of the chiral condensate in QCD using lattice QCD with 2+1 flavors of dynamical overlap quarks. Up and down quark masses cover a range between 3 and 100 MeV on a 16{3}x48 lattice at a lattice spacing approximately 0.11 fm. At the lightest sea quark mass, the finite volume system on the lattice is in the regime. By matching the low-lying eigenvalue spectrum of the Dirac operator with the prediction of chiral perturbation theory at the next-to-leading order, we determine the chiral condensate in (2+1)-flavor QCD with strange quark mass fixed at its physical value as Sigma;{MS[over ]}(2 GeV)=[242(04)(+19/-18) MeV]{3} where the errors are statistical and systematic, respectively.

Quark–hadron phase structure, thermodynamics, and magnetization of QCD matter

NASA Astrophysics Data System (ADS)

Nasser Tawfik, Abdel; Magied Diab, Abdel; Hussein, M. T.

2018-05-01

The SU(3) Polyakov linear-sigma model (PLSM) is systematically implemented to characterize the quark-hadron phase structure and to determine various thermodynamic quantities and the magnetization of quantum chromodynamic (QCD) matter. Using mean-field approximation, the dependence of the chiral order parameter on a finite magnetic field is also calculated. Under a wide range of temperatures and magnetic field strengths, various thermodynamic quantities including trace anomaly, speed of sound squared, entropy density, and specific heat are presented, and some magnetic properties are described as well. Where available these results are compared to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous finding that the transition temperature is reduced with the increase in the magnetic field strength, i.e. QCD matter is characterized by an inverse magnetic catalysis. Furthermore, the temperature dependence of the magnetization showing that QCD matter has paramagnetic properties slightly below and far above the pseudo-critical temperature is confirmed as well. The excellent agreement with recent lattice calculations proves that our QCD-like approach (PLSM) seems to possess the correct degrees of freedom in both the hadronic and partonic phases and describes well the dynamics deriving confined hadrons to deconfined quark-gluon plasma.

Mass-improvement of the vector current in three-flavor QCD

NASA Astrophysics Data System (ADS)

Fritzsch, P.

2018-06-01

We determine two improvement coefficients which are relevant to cancel mass-dependent cutoff effects in correlation functions with operator insertions of the non-singlet local QCD vector current. This determination is based on degenerate three-flavor QCD simulations of non-perturbatively O( a) improved Wilson fermions with tree-level improved gauge action. Employing a very robust strategy that has been pioneered in the quenched approximation leads to an accurate estimate of a counterterm cancelling dynamical quark cutoff effects linear in the trace of the quark mass matrix. To our knowledge this is the first time that such an effect has been determined systematically with large significance.

Instanton liquid properties from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athenodorou, A.; Boucaud, Philippe; De Soto, F.

Here, we examined the instanton contribution to the QCD configurations generated from lattice QCD for N F = 0, N F = 2 + 1 and N F = 2 + 1 + 1 dynamical quark flavors from two different and complementary approaches. First via the use of Gradient flow, we computed instanton liquid properties using an algorithm to localize instantons in the gauge field configurations and studied their evolution with flow time. Then, the analysis of the running at low momenta of gluon Green's functions serves as an independent confirmation of the instanton density which can also be derivedmore » without the use of the Gradient flow.« less

Instanton liquid properties from lattice QCD

DOE PAGES

Athenodorou, A.; Boucaud, Philippe; De Soto, F.; ...

2018-02-22

Here, we examined the instanton contribution to the QCD configurations generated from lattice QCD for N F = 0, N F = 2 + 1 and N F = 2 + 1 + 1 dynamical quark flavors from two different and complementary approaches. First via the use of Gradient flow, we computed instanton liquid properties using an algorithm to localize instantons in the gauge field configurations and studied their evolution with flow time. Then, the analysis of the running at low momenta of gluon Green's functions serves as an independent confirmation of the instanton density which can also be derivedmore » without the use of the Gradient flow.« less

Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point

NASA Astrophysics Data System (ADS)

Chakraborty, B.; Davies, C. T. H.; Detar, C.; El-Khadra, A. X.; Gámiz, E.; Gottlieb, Steven; Hatton, D.; Koponen, J.; Kronfeld, A. S.; Laiho, J.; Lepage, G. P.; Liu, Yuzhi; MacKenzie, P. B.; McNeile, C.; Neil, E. T.; Simone, J. N.; Sugar, R.; Toussaint, D.; van de Water, R. S.; Vaquero, A.; Fermilab Lattice, Hpqcd,; Milc Collaborations

2018-04-01

All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction to aμHVP for the first time with physical values of mu and md and dynamical u , d , s , and c quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of δ aμHVP ,mu≠md=+1.5 (7 )% , in agreement with estimates from phenomenology.

Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, B.; Davies, C. T. H.; DeTar, C.

All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon’s anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction tomore » $${a}_{{\\mu}}^{\\mathrm{HVP}}$$ for the first time with physical values of $${m}_{u}$$ and $${m}_{d}$$ and dynamical $u$, $d$, $s$, and $c$ quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of $${\\delta}{a}_{{\\mu}}^{\\mathrm{HVP},{m}_{u}{\

Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point

DOE PAGES

Chakraborty, B.; Davies, C. T. H.; DeTar, C.; ...

2018-04-12

All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon’s anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction tomore » $${a}_{{\\mu}}^{\\mathrm{HVP}}$$ for the first time with physical values of $${m}_{u}$$ and $${m}_{d}$$ and dynamical $u$, $d$, $s$, and $c$ quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of $${\\delta}{a}_{{\\mu}}^{\\mathrm{HVP},{m}_{u}{\

Conformal Symmetry as a Template for QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, S

2004-08-04

Conformal symmetry is broken in physical QCD; nevertheless, one can use conformal symmetry as a template, systematically correcting for its nonzero {beta} function as well as higher-twist effects. For example, commensurate scale relations which relate QCD observables to each other, such as the generalized Crewther relation, have no renormalization scale or scheme ambiguity and retain a convergent perturbative structure which reflects the underlying conformal symmetry of the classical theory. The ''conformal correspondence principle'' also dictates the form of the expansion basis for hadronic distribution amplitudes. The AdS/CFT correspondence connecting superstring theory to superconformal gauge theory has important implications for hadronmore » phenomenology in the conformal limit, including an all-orders demonstration of counting rules for hard exclusive processes as well as determining essential aspects of hadronic light-front wavefunctions. Theoretical and phenomenological evidence is now accumulating that QCD couplings based on physical observables such as {tau} decay become constant at small virtuality; i.e., effective charges develop an infrared fixed point in contradiction to the usual assumption of singular growth in the infrared. The near-constant behavior of effective couplings also suggests that QCD can be approximated as a conformal theory even at relatively small momentum transfer. The importance of using an analytic effective charge such as the pinch scheme for unifying the electroweak and strong couplings and forces is also emphasized.« less

Running of the charm-quark mass from HERA deep-inelastic scattering data

DOE PAGES

Gizhko, A.; Geiser, A.; Moch, S.; ...

2017-11-07

Combined HERA data on charm production in deep-inelastic scattering have previously been used to determine the charm-quark running mass m c(m c) in the MS¯ renormalisation scheme. Here, the same data are used as a function of the photon virtuality Q 2 to evaluate the charm-quark running mass at different scales to one-loop order, in the context of a next-to-leading order QCD analysis. Lastly, the scale dependence of the mass is found to be consistent with QCD expectations.

Running of the charm-quark mass from HERA deep-inelastic scattering data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gizhko, A.; Geiser, A.; Moch, S.

Combined HERA data on charm production in deep-inelastic scattering have previously been used to determine the charm-quark running mass m c(m c) in the MS¯ renormalisation scheme. Here, the same data are used as a function of the photon virtuality Q 2 to evaluate the charm-quark running mass at different scales to one-loop order, in the context of a next-to-leading order QCD analysis. Lastly, the scale dependence of the mass is found to be consistent with QCD expectations.

QCD Physics with the CMS Experiment

NASA Astrophysics Data System (ADS)

Cerci, S.

2017-12-01

Jets which are the signatures of quarks and gluons in the detector can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. Jets are abundantly produced at the LHC's high energy scales. Measurements of inclusive jets, dijets and multijets can be used to test perturbative QCD predictions and to constrain parton distribution functions (PDF), as well as to measure the strong coupling constant αS . The measurements use the samples of proton-proton collisions collected with the CMS detector at the LHC at various center-of-mass energies of 7, 8 and 13 TeV.

Next-to-leading-order QCD corrections to Higgs boson production plus three jets in gluon fusion.

PubMed

Cullen, G; van Deurzen, H; Greiner, N; Luisoni, G; Mastrolia, P; Mirabella, E; Ossola, G; Peraro, T; Tramontano, F

2013-09-27

We report on the calculation of the cross section for Higgs boson production in association with three jets via gluon fusion, at next-to-leading-order (NLO) accuracy in QCD, in the infinite top-mass approximation. After including the complete NLO QCD corrections, we observe a strong reduction in the scale dependence of the result, and an increased steepness in the transverse momentum distributions of both the Higgs boson and the leading jets. The results are obtained with the combined use of GOSAM, SHERPA, and the MADDIPOLE-MADEVENT framework.

A study of energy-energy correlations and measurement of [alpha][sub s] at the Z[sup 0] resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-01-01

We present the energy-energy correlation (EEC) distribution and its asymmetry (AEEC) in hadronic decays of [Zeta][sup 0] bosons measured by the SLD at SLAC. The data are found to be in good agreement with the predictions of perturbative QCD and fragmentation Monte Carlo models of hadron production. After correction for hadronization effects the data are compared with [Omicron]([alpha][sub s][sup 2]) perturbative QCD calculations from various authors. Fits to the central region of the EEC yield substantially different values of the QCD scale [lambda][sub [ovr MS

A Semiclassical Derivation of the QCD Coupling

NASA Technical Reports Server (NTRS)

Batchelor, David

2009-01-01

The measured value of the QCD coupling alpha(sub s) at the energy M(sub Zo), the variation of alpha(sub s) as a function of energy in QCD, and classical relativistic dynamics are used to investigate virtual pairs of quarks and antiquarks in vacuum fluctuations. For virtual pairs of bottom quarks and antiquarks, the pair lifetime in the classical model agrees with the lifetime from quantum mechanics to good approximation, and the action integral in the classical model agrees as well with the action that follows from the Uncertainty Principle. This suggests that the particles might have small de Broglie wavelengths and behave with well-localized pointlike dynamics. It also permits alpha(sub s) at the mass energy twice the bottom quark mass to be expressed as a simple fraction: 3/16. This is accurate to approximately 10%. The model in this paper predicts the measured value of alpha(sub s)(M(sub Zo)) to be 0.121, which is in agreement with recent measurements within statistical uncertainties.

Cosmological abundance of the QCD axion coupled to hidden photons

NASA Astrophysics Data System (ADS)

Kitajima, Naoya; Sekiguchi, Toyokazu; Takahashi, Fuminobu

2018-06-01

We study the cosmological evolution of the QCD axion coupled to hidden photons. For a moderately strong coupling, the motion of the axion field leads to an explosive production of hidden photons by tachyonic instability. We use lattice simulations to evaluate the cosmological abundance of the QCD axion. In doing so, we incorporate the backreaction of the produced hidden photons on the axion dynamics, which becomes significant in the non-linear regime. We find that the axion abundance is suppressed by at most O (102) for the decay constant fa =1016GeV, compared to the case without the coupling. For a sufficiently large coupling, the motion of the QCD axion becomes strongly damped, and as a result, the axion abundance is enhanced. Our results show that the cosmological upper bound on the axion decay constant can be relaxed by a few hundred for a certain range of the coupling to hidden photons.

ATLAS measurement of Electroweak Vector Boson production

NASA Astrophysics Data System (ADS)

Vittori, C.; Atlas Collaboration

2017-01-01

The measurements of the Drell-Yan production of W and Z /γ* bosons at the LHC provide a benchmark of our understanding of the perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration has performed new high precision measurements of the double differential cross-sections as a function of the dilepton mass and rapidity. The measurements are compared to state of calculations at NNLO in QCD and constrain the photon content of the proton. The angular distributions of the Drell-Yan lepton pairs around the Z-boson mass peak probe the underlying QCD dynamics of the Z-boson production mechanisms. The complete set of angular coefficients describing these distributions is presented and compared to theoretical predictions highlighting different approaches of the QCD and EW modelling. First precise inclusive measurements of W and Z production at 13 TeV are presented. W / Z and W+ /W- ratios profit from a cancellation of experimental uncertainties.

Inverse magnetic catalysis from improved holographic QCD in the Veneziano limit

NASA Astrophysics Data System (ADS)

Gürsoy, Umut; Iatrakis, Ioannis; Järvinen, Matti; Nijs, Govert

2017-03-01

We study the dependence of the chiral condensate on external magnetic field in the context of holographic QCD at large number of flavors. We consider a holographic QCD model where the flavor degrees of freedom fully backreact on the color dynamics. Perturbative QCD calculations have shown that B acts constructively on the chiral condensate, a phenomenon called "magnetic catalysis". In contrast, recent lattice calculations show that, depending on the number of flavors and temperature, the magnetic field may also act destructively, which is called "inverse magnetic catalysis". Here we show that the holographic theory is capable of both behaviors depending on the choice of parameters. For reasonable choice of the potentials entering the model we find qualitative agreement with the lattice expectations. Our results provide insight for the physical reasons behind the inverse magnetic catalysis. In particular, we argue that the backreaction of the flavors to the background geometry decatalyzes the condensate.

The asymptotic form of non-global logarithms, black disc saturation, and gluonic deserts

NASA Astrophysics Data System (ADS)

Neill, Duff

2017-01-01

We develop an asymptotic perturbation theory for the large logarithmic behavior of the non-linear integro-differential equation describing the soft correlations of QCD jet measurements, the Banfi-Marchesini-Smye (BMS) equation. This equation captures the late-time evolution of radiating color dipoles after a hard collision. This allows us to prove that at large values of the control variable (the non-global logarithm, a function of the infra-red energy scales associated with distinct hard jets in an event), the distribution has a gaussian tail. We compute the decay width analytically, giving a closed form expression, and find it to be jet geometry independent, up to the number of legs of the dipole in the active jet. Enabling the asymptotic expansion is the correct perturbative seed, where we perturb around an anzats encoding formally no real emissions, an intuition motivated by the buffer region found in jet dynamics. This must be supplemented with the correct application of the BFKL approximation to the BMS equation in collinear limits. Comparing to the asymptotics of the conformally related evolution equation encountered in small-x physics, the Balitisky-Kovchegov (BK) equation, we find that the asymptotic form of the non-global logarithms directly maps to the black-disc unitarity limit of the BK equation, despite the contrasting physical pictures. Indeed, we recover the equations of saturation physics in the final state dynamics of QCD.

Probing superfast quarks in nuclei through dijet production at the LHC

DOE PAGES

Freese, Adam J.; Sargsian, Misak M.; Strikman, Mark I.

2015-11-12

We investigate dijet production from proton-nucleus collisions at the Large Hadron Collider (LHC) as a means for observing superfast quarks in nuclei with Bjorken x>1 . Kinematically, superfast quarks can be identified through directly measurable jet kinematics. Dynamically, their description requires understanding several elusive properties of nuclear QCD, such as nuclear forces at very short distances, as well as medium modification of parton distributions in nuclei. In the present work, we develop a model for nuclear parton distributions at large x in which the nuclear dynamics at short distance scales are described by two- and three-nucleon short range correlations (SRCs).more » Nuclear modifications are accounted for using the color screening model, and an improved description of the EMC effect is reached by using a structure function parametrization that includes higher-twist contributions. We apply QCD evolution at the leading order to obtain nuclear parton distributions in the kinematic regime of the LHC, and based on the obtained distributions calculate the cross section for dijet production. We find that the rates of the dijet production in pA collisions at kinematics accessible by ATLAS and CMS are sufficient not only to observe superfast quarks but also to get information about the practically unexplored three-nucleon SRCs in nuclei. Additionally, the LHC can extend our knowledge of the EMC effect to large Q 2 where higher-twist effects are negligible.« less

Probing superfast quarks in nuclei through dijet production at the LHC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freese, Adam J.; Sargsian, Misak M.; Strikman, Mark I.

2015-11-01

We investigate dijet production from proton-nucleus collisions at the Large Hadron Collider (LHC) as a means for observing superfast quarks in nuclei with Bjorken x>1 . Kinematically, superfast quarks can be identified through directly measurable jet kinematics. Dynamically, their description requires understanding several elusive properties of nuclear QCD, such as nuclear forces at very short distances, as well as medium modification of parton distributions in nuclei. In the present work, we develop a model for nuclear parton distributions at large x in which the nuclear dynamics at short distance scales are described by two- and three-nucleon short range correlations (SRCs).more » Nuclear modifications are accounted for using the color screening model, and an improved description of the EMC effect is reached by using a structure function parametrization that includes higher-twist contributions. We apply QCD evolution at the leading order to obtain nuclear parton distributions in the kinematic regime of the LHC, and based on the obtained distributions calculate the cross section for dijet production. We find that the rates of the dijet production in pA collisions at kinematics accessible by ATLAS and CMS are sufficient not only to observe superfast quarks but also to get information about the practically unexplored three-nucleon SRCs in nuclei. Additionally, the LHC can extend our knowledge of the EMC effect to large Q2 where higher-twist effects are negligible.« less

Stable Pentaquarks from Strange Chiral Multiplets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silas Beane

2004-12-01

The assumption of strong diquark correlations in the QCD spectrum suggests flavor multiplets of hadrons that are degenerate in the chiral limit. Generally it would be unnatural for there to be degeneracy in the hadron spectrum that is not protected by a QCD symmetry. Here we show--for pentaquarks constructed from diquarks--that these degeneracies can be naturally protected by the full chiral symmetry of QCD. The resulting chiral multiplet structure recovers the ideally-mixed pentaquark mass spectrum of the diquark model, and interestingly, requires that the axial couplings of the pentaquarks to states outside the degenerate multiplets vanish in the chiral limit.more » This result suggests that if these hadrons exist, they are stable in the chiral limit and therefore have widths that scale as the fourth power of the kaon mass over the chiral symmetry breaking scale. Natural-size widths are of order a few MeV.« less

Hybrid baryons in QCD

DOE PAGES

Dudek, Jozef J.; Edwards, Robert G.

2012-03-21

In this study, we present the first comprehensive study of hybrid baryons using lattice QCD methods. Using a large basis of composite QCD interpolating fields we extract an extensive spectrum of baryon states and isolate those of hybrid character using their relatively large overlap onto operators which sample gluonic excitations. We consider the spectrum of Nucleon and Delta states at several quark masses finding a set of positive parity hybrid baryons with quantum numbersmore » $$N_{1/2^+},\\,N_{1/2^+},\\,N_{3/2^+},\\, N_{3/2^+},\\,N_{5/2^+},\\,$$ and $$\\Delta_{1/2^+},\\, \\Delta_{3/2^+}$$ at an energy scale above the first band of `conventional' excited positive parity baryons. This pattern of states is compatible with a color octet gluonic excitation having $$J^{P}=1^{+}$$ as previously reported in the hybrid meson sector and with a comparable energy scale for the excitation, suggesting a common bound-state construction for hybrid mesons and baryons.« less

QCD corrections to ZZ production in gluon fusion at the LHC

DOE PAGES

Caola, Fabrizio; Melnikov, Kirill; Rontsch, Raoul; ...

2015-11-23

We compute the next-to-leading-order QCD corrections to the production of two Z-bosons in the annihilation of two gluons at the LHC. Being enhanced by a large gluon flux, these corrections provide a distinct and, potentially, the dominant part of the N 3LO QCD contributions to Z-pair production in proton collisions. The gg → ZZ annihilation is a loop-induced process that receives the dominant contribution from loops of five light quarks, that are included in our computation in the massless approximation. We find that QCD corrections increase the gg → ZZ production cross section by O(50%–100%) depending on the values ofmore » the renormalization and factorization scales used in the leading-order computation and the collider energy. Furthermore, the large corrections to the gg → ZZ channel increase the pp → ZZ cross section by about 6% to 8%, exceeding the estimated theoretical uncertainty of the recent next-to-next-to-leading-order QCD calculation.« less

Inclusive jet cross section and strong coupling constant measurements at CMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cerci, Salim, E-mail: Salim.Cerci@cern.ch

2016-03-25

The probes which are abundantly produced in high energetic proton-proton (pp) collisions at the LHC are called jets. Events with jets can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. The inclusive jet cross section in pp collision is the fundamental quantity which can be measured and predicted within the framework of perturbative QCD (pQCD). The strong coupling constant α{sub S} which can be determined empirically in the limit of massless quarks, is the single parameter in QCD. The jet measurements can also be used to determine strong coupling constant α{sub S} and parton density functions (PDFs).more » The recent jet measurements which are performed with the data collected by the CMS detector at different center-of-mass energies and down to very low transverse momentum p{sub T} are presented. The measurements are compared to Monte Carlo predictions and perturbative calculations up to next-to-next-to leading order. Finally, the precision jet measurements give further insight into the QCD dynamics.« less

Phases of QCD3 from non-SUSY Seiberg duality and brane dynamics

NASA Astrophysics Data System (ADS)

Armoni, Adi; Niarchos, Vasilis

2018-05-01

We consider a nonsupersymmetric USp Yang-Mills Chern-Simons gauge theory coupled to fundamental flavors. The theory is realised in type-IIB string theory via an embedding in a Hanany-Witten brane configuration which includes an orientifold and antibranes. We argue that the theory admits a magnetic Seiberg dual. Using the magnetic dual we identify dynamics in field theory and brane physics that correspond to various phases, obtaining a better understanding of three-dimensional bosonization and dynamical breaking of flavor symmetry in USp QCD3 theory. In field theory both phases correspond to magnetic "squark" condensation. In string theory, they correspond to open string tachyon condensation and brane reconnection. We also discuss other phases where the magnetic `squark' is massive. Finally, we briefly comment on the case of unitary gauge groups.

Phenomenology of strongly coupled chiral gauge theories

DOE PAGES

Bai, Yang; Berger, Joshua; Osborne, James; ...

2016-11-25

A sector with QCD-like strong dynamics is common in models of non-standard physics. Such a model could be accessible in LHC searches if both confinement and big-quarks charged under the confining group are at the TeV scale. Big-quark masses at this scale can be explained if the new fermions are chiral under a new U(1)' gauge symmetry such that their bare masses are related to the U(1)'-breaking and new confinement scales. Here we present a study of a minimal GUT-motivated and gauge anomaly-free model with implications for the LHC Run 2 searches. We find that the first signatures of suchmore » models could appear as two gauge boson resonances. The chiral nature of the model could be confirmed by observation of a Z'γ resonance, where the Z' naturally has a large leptonic branching ratio because of its kinetic mixing with the hypercharge gauge boson.« less

Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point.

PubMed

Chakraborty, B; Davies, C T H; DeTar, C; El-Khadra, A X; Gámiz, E; Gottlieb, Steven; Hatton, D; Koponen, J; Kronfeld, A S; Laiho, J; Lepage, G P; Liu, Yuzhi; Mackenzie, P B; McNeile, C; Neil, E T; Simone, J N; Sugar, R; Toussaint, D; Van de Water, R S; Vaquero, A

2018-04-13

All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction to a_{μ}^{HVP} for the first time with physical values of m_{u} and m_{d} and dynamical u, d, s, and c quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of δa_{μ}^{HVP,m_{u}≠m_{d}}=+1.5(7)%, in agreement with estimates from phenomenology.

Precision probes of QCD at high energies

NASA Astrophysics Data System (ADS)

Alioli, Simone; Farina, Marco; Pappadopulo, Duccio; Ruderman, Joshua T.

2017-07-01

New physics, that is too heavy to be produced directly, can leave measurable imprints on the tails of kinematic distributions at the LHC. We use energetic QCD processes to perform novel measurements of the Standard Model (SM) Effective Field Theory. We show that the dijet invariant mass spectrum, and the inclusive jet transverse momentum spectrum, are sensitive to a dimension 6 operator that modifies the gluon propagator at high energies. The dominant effect is constructive or destructive interference with SM jet production. We compare differential next-to-leading order predictions from POWHEG to public 7 TeV jet data, including scale, PDF, and experimental uncertainties and their respective correlations. We constrain a New Physics (NP) scale of 3.5 TeV with current data. We project the reach of future 13 and 100 TeV measurements, which we estimate to be sensitive to NP scales of 8 and 60 TeV, respectively. As an application, we apply our bounds to constrain heavy vector octet colorons that couple to the QCD current. We project that effective operators will surpass bump hunts, in terms of coloron mass reach, even for sequential couplings.

Kenneth Wilson and Lattice QCD

NASA Astrophysics Data System (ADS)

Ukawa, Akira

2015-09-01

We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward better understanding of physics, better algorithms, and more powerful supercomputers have produced major breakthroughs in our understanding of the strong interactions. We review the salient results of this effort in understanding the hadron spectrum, the Cabibbo-Kobayashi-Maskawa matrix elements and CP violation, and quark-gluon plasma at high temperatures. We conclude with a brief summary and a future perspective.

High-Energy QCD Asymptotics of Photon-Photon Collisions

NASA Astrophysics Data System (ADS)

Brodsky, S. J.; Fadin, V. S.; Kim, V. T.; Lipatov, L. N.; Pivovarov, G. B.

2002-07-01

The high-energy behaviour of the total cross section for highly virtual photons, as predicted by the BFKL equation at next-to-leading order (NLO) in QCD, is discussed. The NLO BFKL predictions, improved by the BLM optimal scale setting, are in good agreement with recent OPAL and L3 data at CERN LEP2. NLO BFKL predictions for future linear colliders are presented.

Standard model group: Survival of the fittest

NASA Astrophysics Data System (ADS)

Nielsen, H. B.; Brene, N.

1983-09-01

The essential content of this paper is related to random dynamics. We speculate that the world seen through a sub-Planck-scale microscope has a lattice structure and that the dynamics on this lattice is almost completely random, except for the requirement that the random (plaquette) action is invariant under some "world (gauge) group". We see that the randomness may lead to spontaneous symmetry breakdown in the vacuum (spontaneous collapse) without explicit appeal to any scalar field associated with the usual Higgs mechanism. We further argue that the subgroup which survives as the end product of a possible chain of collapses is likely to have certain properties; the most important is that it has a topologically connected center. The standard group, i.e. the group of the gauge theory which combines the Salam-Weinberg model with QCD, has this property.

Time-reversal breaking in QCD4, walls, and dualities in 2 + 1 dimensions

NASA Astrophysics Data System (ADS)

Gaiotto, Davide; Komargodski, Zohar; Seiberg, Nathan

2018-01-01

We study SU( N ) Quantum Chromodynamics (QCD) in 3+1 dimensions with N f degenerate fundamental quarks with mass m and a θ-parameter. For generic m and θ the theory has a single gapped vacuum. However, as θ is varied through θ = π for large m there is a first order transition. For N f = 1 the first order transition line ends at a point with a massless η' particle (for all N ) and for N f > 1 the first order transition ends at m = 0, where, depending on the value of N f , the IR theory has free Nambu-Goldstone bosons, an interacting conformal field theory, or a free gauge theory. Even when the 4 d bulk is smooth, domain walls and interfaces can have interesting phase transitions separating different 3 d phases. These turn out to be the phases of the recently studied 3 d Chern-Simons matter theories, thus relating the dynamics of QCD4 and QCD3, and, in particular, making contact with the recently discussed dualities in 2+1 dimensions. For example, when the massless 4 d theory has an SU( N f ) sigma model, the domain wall theory at low (nonzero) mass supports a 3 d massless CP^{N_f-1} nonlinear σ-model with a Wess-Zumino term, in agreement with the conjectured dynamics in 2+1 dimensions.

Axial, scalar, and tensor charges of the nucleon from 2 + 1 + 1 -flavor lattice QCD

DOE PAGES

Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Cohen, Saul D.; ...

2016-09-19

Here, we present results for the isovector axial, scalar, and tensor charges g u–d A, g u–d S, and g u–d T of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear β-decays, and the flavor-diagonal tensor charges g u T, g d T, and g s T are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations weremore » done using nine ensembles of gauge configurations generated by the MILC Collaboration using the highly improved staggered quarks action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings a ≈ 0.06,0.09, and 0.12 fm and light-quark masses corresponding to the pion masses M π ≈ 135, 225, and 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, lattice volume, and light-quark masses for the connected contributions. Our final estimates, in the ¯MS scheme at 2 GeV, of the isovector charges are g u–d A = 1.195(33)(20), g u–d S = 0.97(12)(6), and g u–d T = 0.987(51)(20). The first error includes statistical and all systematic uncertainties except that due to the extrapolation Ansatz, which is given by the second error estimate. Combining our estimate for gu–dS with the difference of light quarks masses (m d–m u) QCD = 2.67(35) MeV given by the Flavor Lattice Average Group, we obtain (M N – M P) QCD = 2.59(49) MeV. Estimates of the connected part of the flavor-diagonal tensor charges of the proton are g u T = 0.792(42) and g d T = –0.194(14). Combining our new estimates with precision low-energy experiments, we present updated constraints on novel scalar and tensor interactions, ε S,T, at the TeV scale.« less

Nucleon PDFs and TMDs from Continuum QCD

NASA Astrophysics Data System (ADS)

Bednar, Kyle; Cloet, Ian; Tandy, Peter

2017-09-01

The parton structure of the nucleon is investigated in an approach based upon QCD's Dyson-Schwinger equations. The method accommodates a variety of QCD's dynamical outcomes including: the running mass of quark propagators and formation of non-pointlike di-quark correlations. All needed elements, including the nucleon wave function solution from a Poincaré covariant Faddeev equation, are encoded in spectral-type representations in the Nakanishi style to facilitate Feynman integral procedures and allow insight into key underlying mechanisms. Results will be presented for spin-independent PDFs and TMDs arising from a truncation to allow only scalar di-quark correlations. The influence of axial-vector di-quark correlations may be discussed if results are available. Supported by NSF Grant No. PHY-1516138.

openQ*D simulation code for QCD+QED

NASA Astrophysics Data System (ADS)

Campos, Isabel; Fritzsch, Patrick; Hansen, Martin; Krstić Marinković, Marina; Patella, Agostino; Ramos, Alberto; Tantalo, Nazario

2018-03-01

The openQ*D code for the simulation of QCD+QED with C* boundary conditions is presented. This code is based on openQCD-1.6, from which it inherits the core features that ensure its efficiency: the locally-deflated SAP-preconditioned GCR solver, the twisted-mass frequency splitting of the fermion action, the multilevel integrator, the 4th order OMF integrator, the SSE/AVX intrinsics, etc. The photon field is treated as fully dynamical and C* boundary conditions can be chosen in the spatial directions. We discuss the main features of openQ*D, and we show basic test results and performance analysis. An alpha version of this code is publicly available and can be downloaded from http://rcstar.web.cern.ch/.

Towards Lattice QCD Baryon Forces at the Physical Point: First Results

NASA Astrophysics Data System (ADS)

Doi, Takumi; Aoki, Sinya; Gongyo, Shinya; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Miyamoto, Takaya; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

Lattice QCD calculations of baryon forces are performed for the first time with (almost) physical quark masses. Nf = 2 + 1 dynamical clover fermion gauge configurations are generated at the lattice spacing of a ≃ 0.085 fm on a (96a)4 ≃ (8.2 fm)4 lattice with quark masses corresponding to (mπ,mK) ≃ (146,525) MeV. Baryon forces are calculated using the time-dependent HAL QCD method. In this report, we study ΞΞ and NN systems both in 1S0 and 3S1-3D1 channels, and the results for the central and tensor forces as well as phase shifts in the ΞΞ (1S0) channel are presented.

Exclusive processes and the fundamental structure of hadrons

DOE PAGES

Brodsky, Stanley J.

2015-01-20

I review the historical development of QCD predictions for exclusive hadronic processes, beginning with constituent counting rules and the quark interchange mechanism, phenomena which gave early validation for the quark structure of hadrons. The subsequent development of pQCD factorization theorems for hard exclusive amplitudes and the development of evolution equations for the hadron distribution amplitudes provided a rigorous framework for calculating hadronic form factors and hard scattering exclusive scattering processes at high momentum transfer. I also give a brief introduction to the field of "light-front holography" and the insights it brings to quark confinement, the behavior of the QCD couplingmore » in the nonperturbative domain, as well as hadron spectroscopy and the dynamics of exclusive processes.« less

Exclusive processes and the fundamental structure of hadrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.

I review the historical development of QCD predictions for exclusive hadronic processes, beginning with constituent counting rules and the quark interchange mechanism, phenomena which gave early validation for the quark structure of hadrons. The subsequent development of pQCD factorization theorems for hard exclusive amplitudes and the development of evolution equations for the hadron distribution amplitudes provided a rigorous framework for calculating hadronic form factors and hard scattering exclusive scattering processes at high momentum transfer. I also give a brief introduction to the field of "light-front holography" and the insights it brings to quark confinement, the behavior of the QCD couplingmore » in the nonperturbative domain, as well as hadron spectroscopy and the dynamics of exclusive processes.« less

Simulations of QCD and QED with C* boundary conditions

NASA Astrophysics Data System (ADS)

Hansen, Martin; Lucini, Biagio; Patella, Agostino; Tantalo, Nazario

2018-03-01

We present exploratory results from dynamical simulations of QCD in isolation, as well as QCD coupled to QED, with C* boundary conditions. In finite volume, the use of C* boundary conditions allows for a gauge invariant and local formulation of QED without zero modes. In particular we show that the simulations reproduce known results and that masses of charged mesons can be extracted in a completely gauge invariant way. For the simulations we use a modified version of the HiRep code. The primary features of the simulation code are presented and we discuss some details regarding the implementation of C* boundary conditions and the simulated lattice action. Preprint: CP3-Origins-2017-046 DNRF90, CERN-TH-2017-214

Nucleon axial charge in (2+1)-flavor dynamical-lattice QCD with domain-wall fermions.

PubMed

Yamazaki, T; Aoki, Y; Blum, T; Lin, H W; Lin, M F; Ohta, S; Sasaki, S; Tweedie, R J; Zanotti, J M

2008-05-02

We present results for the nucleon axial charge g{A} at a fixed lattice spacing of 1/a=1.73(3) GeV using 2+1 flavors of domain wall fermions on size 16;{3} x 32 and 24;{3} x 64 lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The length of the Monte Carlo trajectory at the lightest m_{pi} is 7360 units, including 900 for thermalization. We find finite volume effects are larger than the pion mass dependence at m{pi}=330 MeV. We also find a scaling with the single variable m{pi}L which can also be seen in previous two-flavor domain wall and Wilson fermion calculations. Using this scaling to eliminate the finite-volume effect, we obtain g{A}=1.20(6)(4) at the physical pion mass, m_{pi}=135 MeV, where the first and second errors are statistical and systematic. The observed finite-volume scaling also appears in similar quenched simulations, but disappear when V>or=(2.4 fm);{3}. We argue this is a dynamical quark effect.

Bs and Ds decay constants in three-flavor lattice QCD.

PubMed

Wingate, Matthew; Davies, Christine T H; Gray, Alan; Lepage, G Peter; Shigemitsu, Junko

2004-04-23

Capitalizing on recent advances in lattice QCD, we present a calculation of the leptonic decay constants f(B(s)) and f(D(s)) that includes effects of one strange sea quark and two light sea quarks via an improved staggered action. By shedding the quenched approximation and the associated lattice scale uncertainty, lattice QCD greatly increases its predictive power. Nonrelativistic QCD is used to simulate heavy quarks with masses between 1.5m(c) and m(b). We arrive at the following results: f(B(s))=260+/-7+/-26+/-8+/-5 and f(D(s))=290+/-20+/-29+/-29+/-6 MeV. The first quoted error is the statistical uncertainty, and the rest estimate the sizes of higher order terms neglected in this calculation. All of these uncertainties are systematically improvable by including another order in the weak coupling expansion, the nonrelativistic expansion, or the Symanzik improvement program.

Physics of the 1 Teraflop RIKEN-BNL-Columbia QCD project. Proceedings of RIKEN BNL Research Center workshop: Volume 13

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1998-10-16

A workshop was held at the RIKEN-BNL Research Center on October 16, 1998, as part of the first anniversary celebration for the center. This meeting brought together the physicists from RIKEN-BNL, BNL and Columbia who are using the QCDSP (Quantum Chromodynamics on Digital Signal Processors) computer at the RIKEN-BNL Research Center for studies of QCD. Many of the talks in the workshop were devoted to domain wall fermions, a discretization of the continuum description of fermions which preserves the global symmetries of the continuum, even at finite lattice spacing. This formulation has been the subject of analytic investigation for somemore » time and has reached the stage where large-scale simulations in QCD seem very promising. With the computational power available from the QCDSP computers, scientists are looking forward to an exciting time for numerical simulations of QCD.« less

Factorization and resummation of Higgs boson differential distributions in soft-collinear effective theory

NASA Astrophysics Data System (ADS)

Mantry, Sonny; Petriello, Frank

2010-05-01

We derive a factorization theorem for the Higgs boson transverse momentum (pT) and rapidity (Y) distributions at hadron colliders, using the soft-collinear effective theory (SCET), for mh≫pT≫ΛQCD, where mh denotes the Higgs mass. In addition to the factorization of the various scales involved, the perturbative physics at the pT scale is further factorized into two collinear impact-parameter beam functions (IBFs) and an inverse soft function (ISF). These newly defined functions are of a universal nature for the study of differential distributions at hadron colliders. The additional factorization of the pT-scale physics simplifies the implementation of higher order radiative corrections in αs(pT). We derive formulas for factorization in both momentum and impact parameter space and discuss the relationship between them. Large logarithms of the relevant scales in the problem are summed using the renormalization group equations of the effective theories. Power corrections to the factorization theorem in pT/mh and ΛQCD/pT can be systematically derived. We perform multiple consistency checks on our factorization theorem including a comparison with known fixed-order QCD results. We compare the SCET factorization theorem with the Collins-Soper-Sterman approach to low-pT resummation.

Fluctuations in the quark-meson model for QCD with isospin chemical potential

NASA Astrophysics Data System (ADS)

Kamikado, Kazuhiko; Strodthoff, Nils; von Smekal, Lorenz; Wambach, Jochen

2013-01-01

We study the two-flavor quark-meson (QM) model with the functional renormalization group (FRG) to describe the effects of collective mesonic fluctuations on the phase diagram of QCD at finite baryon and isospin chemical potentials, μB and μI. With only isospin chemical potential there is a precise equivalence between the competing dynamics of chiral versus pion condensation and that of collective mesonic and baryonic fluctuations in the quark-meson-diquark model for two-color QCD at finite baryon chemical potential. Here, finite μB = 3 μ introduces an additional dimension to the phase diagram as compared to two-color QCD, however. At zero temperature, the (μI, μ) plane of this phase diagram is strongly constrained by the "Silver Blaze problem." In particular, the onset of pion condensation must occur at μI =mπ / 2, independent of μ as long as μ +μI stays below the constituent quark mass of the QM model or the liquid-gas transition line of nuclear matter in QCD. In order to maintain this relation beyond mean field it is crucial to compute the pion mass from its timelike correlator with the FRG in a consistent way.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, Nadine; Prestel, S.; Ritzmann, M.

We present the first public implementation of antenna-based QCD initial- and final-state showers. The shower kernels are 2→3 antenna functions, which capture not only the collinear dynamics but also the leading soft (coherent) singularities of QCD matrix elements. We define the evolution measure to be inversely proportional to the leading poles, hence gluon emissions are evolved in a p ⊥ measure inversely proportional to the eikonal, while processes that only contain a single pole (e.g., g → qq¯) are evolved in virtuality. Non-ordered emissions are allowed, suppressed by an additional power of 1/Q 2. Recoils and kinematics are governed bymore » exact on-shell 2 → 3 phase-space factorisations. This first implementation is limited to massless QCD partons and colourless resonances. Tree-level matrix-element corrections are included for QCD up to O(α 4 s) (4 jets), and for Drell–Yan and Higgs production up to O(α 3 s) (V / H + 3 jets). Finally, the resulting algorithm has been made publicly available in Vincia 2.0.« less

Heavy flavor puzzle at LHC: a serendipitous interplay of jet suppression and fragmentation.

PubMed

Djordjevic, Magdalena

2014-01-31

Both charged hadrons and D mesons are considered to be excellent probes of QCD matter created in ultrarelativistic heavy ion collisions. Surprisingly, recent experimental observations at LHC show the same jet suppression for these two probes, which--contrary to pQCD expectations--may suggest similar energy losses for light quarks and gluons in the QCD medium. We here use our recently developed energy loss formalism in a finite-size dynamical QCD medium to analyze this phenomenon that we denote as the "heavy flavor puzzle at LHC." We show that this puzzle is a consequence of an unusual combination of the suppression and fragmentation patterns and, in fact, does not require invoking the same energy loss for light partons. Furthermore, we show that this combination leads to a simple relationship between the suppressions of charged hadrons and D mesons and the corresponding bare quark suppressions. Consequently, a coincidental matching of jet suppression and fragmentation allows considerably simplifying the interpretation of the corresponding experimental data.

Initial-state colour dipole emission associated with QCD Pomeron exchange

NASA Astrophysics Data System (ADS)

Bialas, A.; Peschanski, R.

1995-02-01

The initial-state radiation of soft colour dipoles produced together with a single QCD Pomeron exchange (BFKL) in onium-onium scattering is calculated in the framework of Mueller's approach. The resulting dipole production grows with increasing energy and reveals an unexpected feature of a power-law tail at appreciably large transverse distances from the collision axis, this phenomenon being related to the scale-invariant structure of dipole-dipole correlations.

Extra dimension searches at hadron colliders to next-to-leading order-QCD

NASA Astrophysics Data System (ADS)

Kumar, M. C.; Mathews, Prakash; Ravindran, V.

2007-11-01

The quantitative impact of NLO-QCD corrections for searches of large and warped extra dimensions at hadron colliders are investigated for the Drell-Yan process. The K-factor for various observables at hadron colliders are presented. Factorisation, renormalisation scale dependence and uncertainties due to various parton distribution functions are studied. Uncertainties arising from the error on experimental data are estimated using the MRST parton distribution functions.

Top-pair production at the LHC through NNLO QCD and NLO EW

NASA Astrophysics Data System (ADS)

Czakon, Michał; Heymes, David; Mitov, Alexander; Pagani, Davide; Tsinikos, Ioannis; Zaro, Marco

2017-10-01

In this work we present for the first time predictions for top-quark pair differential distributions at the LHC at NNLO QCD accuracy and including EW corrections. For the latter we include not only contributions of O({α}_s^2α ) , but also those of order O({α}_s{α}^2) and O({α}^3) . Besides providing phenomenological predictions for all main differential distributions with stable top quarks, we also study the following issues. 1) The effect of the photon PDF on top-pair spectra: we find it to be strongly dependent on the PDF set used — especially for the top p T distribution. 2) The difference between the additive and multiplicative approaches for combining QCD and EW corrections: with our scale choice, we find relatively small differences between the central predictions, but reduced scale dependence within the multiplicative approach. 3) The potential effect from the radiation of heavy bosons on inclusive top-pair spectra: we find it to be, typically, negligible.

Determination of the QCD Λ Parameter and the Accuracy of Perturbation Theory at High Energies.

PubMed

Dalla Brida, Mattia; Fritzsch, Patrick; Korzec, Tomasz; Ramos, Alberto; Sint, Stefan; Sommer, Rainer

2016-10-28

We discuss the determination of the strong coupling α_{MS[over ¯]}(m_{Z}) or, equivalently, the QCD Λ parameter. Its determination requires the use of perturbation theory in α_{s}(μ) in some scheme s and at some energy scale μ. The higher the scale μ, the more accurate perturbation theory becomes, owing to asymptotic freedom. As one step in our computation of the Λ parameter in three-flavor QCD, we perform lattice computations in a scheme that allows us to nonperturbatively reach very high energies, corresponding to α_{s}=0.1 and below. We find that (continuum) perturbation theory is very accurate there, yielding a 3% error in the Λ parameter, while data around α_{s}≈0.2 are clearly insufficient to quote such a precision. It is important to realize that these findings are expected to be generic, as our scheme has advantageous properties regarding the applicability of perturbation theory.

Spectroscopy of triply charmed baryons from lattice QCD

DOE PAGES

Padmanath, M.; Edwards, Robert G.; Mathur, Nilmani; ...

2014-10-14

The spectrum of excitations of triply-charmed baryons is computed using lattice QCD including dynamical light quark fields. The spectrum obtained has baryonic states with well-defined total spin up to 7/2 and the low-lying states closely resemble the expectation from models with an SU(6) x O(3) symmetry. As a result, energy splittings between extracted states, including those due to spin-orbit coupling in the heavy quark limit are computed and compared against data at other quark masses.

Nucleon structure from 2+1-flavor domain-wall QCD

NASA Astrophysics Data System (ADS)

Ohta, Shigemi

2018-03-01

Nucleon-structure calculations of isovector vector-and axialvector-current form factors, transversity and scalar charge, and quark momentum and helicity fractions are reported from two recent 2+1-flavor dynamical domain-wall fermions lattice-QCD ensembles generated jointly by the RIKEN-BNL-Columbia and UKQCD Collaborations with Iwasaki × dislocation-suppressing-determinatn-ratio gauge action at inverse lattice spacing of 1.378(7) GeV and pion mass values of 249.4(3) and 172.3(3) MeV.

Unified models of the QCD axion and supersymmetry breaking

NASA Astrophysics Data System (ADS)

Harigaya, Keisuke; Leedom, Jacob M.

2017-08-01

Similarities between the gauge meditation of supersymmetry breaking and the QCD axion model suggest that they originate from the same dynamics. We present a class of models where supersymmetry and the Peccei-Quinn symmetry are simultaneously broken. The messengers that mediate the effects of these symmetry breakings to the Standard Model are identical. Since the axion resides in the supersymmetry breaking sector, the saxion and the axino are heavy. We show constraints on the axion decay constant and the gravitino mass.

Precision probes of QCD at high energies

DOE PAGES

Alioli, Simone; Farina, Marco; Pappadopulo, Duccio; ...

2017-07-20

New physics, that is too heavy to be produced directly, can leave measurable imprints on the tails of kinematic distributions at the LHC.We use energetic QCD processes to perform novel measurements of the Standard Model (SM) Effective Field Theory. We show that the dijet invariant mass spectrum, and the inclusive jet transverse momentum spectrum, are sensitive to a dimension 6 operator that modifies the gluon propagator at high energies. The dominant effect is constructive or destructive interference with SM jet production. Here, we compare differential next-to-leading order predictions from POWHEG to public 7TeV jet data, including scale, PDF, and experimentalmore » uncertainties and their respective correlations. Furthermore, we constrain a New Physics (NP) scale of 3.5TeV with current data. We project the reach of future 13 and 100TeV measurements, which we estimate to be sensitive to NP scales of 8 and 60TeV, respectively. As an application, we apply our bounds to constrain heavy vector octet colorons that couple to the QCD current. We conclude that effective operators will surpass bump hunts, in terms of coloron mass reach, even for sequential couplings.« less

Investigating the topological structure of quenched lattice QCD with overlap fermions using a multi-probing approximation

NASA Astrophysics Data System (ADS)

Zou, You-Hao; Zhang, Jian-Bo; Xiong, Guang-Yi; Chen, Ying; Liu, Chuan; Liu, Yu-Bin; Ma, Jian-Ping

2017-10-01

The topological charge density and topological susceptibility are determined by a multi-probing approximation using overlap fermions in quenched SU(3) gauge theory. Then we investigate the topological structure of the quenched QCD vacuum, and compare it with results from the all-scale topological density. The results are consistent. Random permuted topological charge density is used to check whether these structures represent underlying ordered properties. The pseudoscalar glueball mass is extracted from the two-point correlation function of the topological charge density. We study 3 ensembles of different lattice spacing a with the same lattice volume 163×32. The results are compatible with the results of all-scale topological charge density, and the topological structures revealed by multi-probing are much closer to all-scale topological charge density than those from eigenmode expansion. Supported by National Natural Science Foundation of China (NSFC) (11335001, 11275169, 11075167), It is also supported in part by the DFG and the NSFC (11261130311) through funds provided to the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD". This work was also funded in part by National Basic Research Program of China (973 Program) (2015CB856700)

The asymptotic form of non-global logarithms, black disc saturation, and gluonic deserts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neill, Duff

Here, we develop an asymptotic perturbation theory for the large logarithmic behavior of the non-linear integro-differential equation describing the soft correlations of QCD jet measurements, the Banfi-Marchesini-Smye (BMS) equation. Furthermore, this equation captures the late-time evolution of radiating color dipoles after a hard collision. This allows us to prove that at large values of the control variable (the non-global logarithm, a function of the infra-red energy scales associated with distinct hard jets in an event), the distribution has a gaussian tail. We also compute the decay width analytically, giving a closed form expression, and find it to be jet geometrymore » independent, up to the number of legs of the dipole in the active jet. By enabling the asymptotic expansion we find that the perturbative seed is correct; we perturb around an anzats encoding formally no real emissions, an intuition motivated by the buffer region found in jet dynamics. This must be supplemented with the correct application of the BFKL approximation to the BMS equation in collinear limits. Comparing to the asymptotics of the conformally related evolution equation encountered in small-x physics, the Balitisky-Kovchegov (BK) equation, we find that the asymptotic form of the non-global logarithms directly maps to the black-disc unitarity limit of the BK equation, despite the contrasting physical pictures. Indeed, we recover the equations of saturation physics in the final state dynamics of QCD.« less

The asymptotic form of non-global logarithms, black disc saturation, and gluonic deserts

DOE PAGES

Neill, Duff

2017-01-25

Here, we develop an asymptotic perturbation theory for the large logarithmic behavior of the non-linear integro-differential equation describing the soft correlations of QCD jet measurements, the Banfi-Marchesini-Smye (BMS) equation. Furthermore, this equation captures the late-time evolution of radiating color dipoles after a hard collision. This allows us to prove that at large values of the control variable (the non-global logarithm, a function of the infra-red energy scales associated with distinct hard jets in an event), the distribution has a gaussian tail. We also compute the decay width analytically, giving a closed form expression, and find it to be jet geometrymore » independent, up to the number of legs of the dipole in the active jet. By enabling the asymptotic expansion we find that the perturbative seed is correct; we perturb around an anzats encoding formally no real emissions, an intuition motivated by the buffer region found in jet dynamics. This must be supplemented with the correct application of the BFKL approximation to the BMS equation in collinear limits. Comparing to the asymptotics of the conformally related evolution equation encountered in small-x physics, the Balitisky-Kovchegov (BK) equation, we find that the asymptotic form of the non-global logarithms directly maps to the black-disc unitarity limit of the BK equation, despite the contrasting physical pictures. Indeed, we recover the equations of saturation physics in the final state dynamics of QCD.« less

Longitudinal-Transverse Separation of Deep-Inelastic Scattering at Low Q² on Nucleons and Nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tvaskis, Vladas

2004-12-06

Since the early experiments at SLAC, which discovered the nucleon substructure and led to the development of the quark parton model, deep inelastic scattering (DIS) has been the most powerful tool to investigate the partonic substructure of the nucleon. After about 30 years of experiments with electron and muon beams the nucleon structure function F 2(x,Q 2) is known with high precision over about four orders of magnitude in x and Q 2. In the region of Q 2 > 1 (GeV/c) 2 the results of the DIS measurements are interpreted in terms of partons (quarks and gluons). The theoreticalmore » framework is provided in this case by perturbative Quantum Chromo Dynamics (pQCD), which includes scaling violations, as described by the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) equations. The description starts to fail when Q 2 becomes of the order of 1 (GeV/c) 2, where non-perturbative effects (higher-twist effects), which are still not fully understood, become important (non-pQCD). The sensitivity for order-n twist effects increases with decreasing Q 2, since they include a factor 1/(Q 2n) (n ≥ 1).« less

Semi-Classical Models for Virtual Antiparticle Pairs

NASA Technical Reports Server (NTRS)

Batchelor, David; Zukor, Dorothy (Technical Monitor)

2001-01-01

Virtual particle-antiparticle pairs of massive elementary particle& are predicted in Quantum Field Theory (QFT) to appear from the vacuum and annihilate each other again within their Heisenberg lifetimes h/4mc(exp 2). In this work, semiclassical models of this process - for the cases of massive leptons, quarks, and the massive weak bosons W and Z - are constructed. It is shown that the dynamical lifetime of the particle- antiparticle system in each case equals the Heisenberg lifetime to good approximation, and obeys appropriate quantization conditions on the field fluctuation action. In other words, the dynamical lifetime of the semiclassical model agrees with QED and QCD to good approximation. But the formula for the dynamical lifetime in each model includes the force strength coupling constant (e in the lepton case, alpha(sup s) (q(exp 2)) in the quark cases), while the Heisenberg lifetime formula does not. Observing the agreement of the Heisenberg and dynamical lifetimes, we may derive the QED and QCD coupling constants in terms of h, c, and numerical factors only.

The renormalization scale-setting problem in QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Xing-Gang; Brodsky, Stanley J.; Mojaza, Matin

2013-09-01

A key problem in making precise perturbative QCD predictions is to set the proper renormalization scale of the running coupling. The conventional scale-setting procedure assigns an arbitrary range and an arbitrary systematic error to fixed-order pQCD predictions. In fact, this ad hoc procedure gives results which depend on the choice of the renormalization scheme, and it is in conflict with the standard scale-setting procedure used in QED. Predictions for physical results should be independent of the choice of the scheme or other theoretical conventions. We review current ideas and points of view on how to deal with the renormalization scalemore » ambiguity and show how to obtain renormalization scheme- and scale-independent estimates. We begin by introducing the renormalization group (RG) equation and an extended version, which expresses the invariance of physical observables under both the renormalization scheme and scale-parameter transformations. The RG equation provides a convenient way for estimating the scheme- and scale-dependence of a physical process. We then discuss self-consistency requirements of the RG equations, such as reflexivity, symmetry, and transitivity, which must be satisfied by a scale-setting method. Four typical scale setting methods suggested in the literature, i.e., the Fastest Apparent Convergence (FAC) criterion, the Principle of Minimum Sensitivity (PMS), the Brodsky–Lepage–Mackenzie method (BLM), and the Principle of Maximum Conformality (PMC), are introduced. Basic properties and their applications are discussed. We pay particular attention to the PMC, which satisfies all of the requirements of RG invariance. Using the PMC, all non-conformal terms associated with the β-function in the perturbative series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC provides the principle underlying the BLM method, since it gives the general rule for extending BLM up to any perturbative order; in fact, they are equivalent to each other through the PMC–BLM correspondence principle. Thus, all the features previously observed in the BLM literature are also adaptable to the PMC. The PMC scales and the resulting finite-order PMC predictions are to high accuracy independent of the choice of the initial renormalization scale, and thus consistent with RG invariance. The PMC is also consistent with the renormalization scale-setting procedure for QED in the zero-color limit. The use of the PMC thus eliminates a serious systematic scale error in perturbative QCD predictions, greatly improving the precision of empirical tests of the Standard Model and their sensitivity to new physics.« less

QCD phase-transition and chemical freezeout in nonzero magnetic field at NICA

NASA Astrophysics Data System (ADS)

Tawfik, Abdel Nasser

2017-01-01

Because of relativistic off-center motion of the charged spectators and the local momentum-imbalance experienced by the participants, a huge magnetic field is likely generated in high-energy collisions. The influence of such short-lived magnetic field on the QCD phase-transition(s) is analysed. From Polyakov linear-sigma model, we study the chiral phase-transition and the magnetic response and susceptibility in dependence on temperature, density and magnetic field strength. The systematic measurements of the phase-transition characterizing signals, such as the fluctuations, the dynamical correlations and the in-medium modifications of rho-meson, for instance, in different interacting systems and collision centralities are conjectured to reveal an almost complete description for the QCD phase-structure and the chemical freezeout. We limit the discussion to NICA energies.

Lattice QCD static potentials of the meson-meson and tetraquark systems computed with both quenched and full QCD

NASA Astrophysics Data System (ADS)

Bicudo, P.; Cardoso, M.; Oliveira, O.; Silva, P. J.

2017-10-01

We revisit the static potential for the Q Q Q ¯Q ¯ system using SU(3) lattice simulations, studying both the color singlets' ground state and first excited state. We consider geometries where the two static quarks and the two antiquarks are at the corners of rectangles of different sizes. We analyze the transition between a tetraquark system and a two-meson system with a two by two correlator matrix. We compare the potentials computed with quenched QCD and with dynamical quarks. We also compare our simulations with the results of previous studies and analyze quantitatively fits of our results with Ansätze inspired in the string flip-flop model and in its possible color excitations.

Structure of the Roper resonance from lattice QCD constraints

NASA Astrophysics Data System (ADS)

Wu, Jia-jun; Leinweber, Derek B.; Liu, Zhan-wei; Thomas, Anthony W.

2018-05-01

Two different effective field theory descriptions of the pion-nucleon scattering data are constructed to describe the region of the Roper resonance. In one, the resonance is the result of strong rescattering between coupled meson-baryon channels, while in the other the resonance has a large bare-baryon (or quark-model-like) component. The predictions of these two scenarios are compared with the latest lattice QCD simulation results in this channel. We find that the second scenario is not consistent with lattice QCD results, whereas the first agrees with those constraints. In that preferred scenario, the mass of the quark-model-like state is approximately 2 GeV, with the infinite-volume Roper resonance best described as a resonance generated dynamically through strongly coupled meson-baryon channels.

Approximate degeneracy of J =1 spatial correlators in high temperature QCD

NASA Astrophysics Data System (ADS)

Rohrhofer, C.; Aoki, Y.; Cossu, G.; Fukaya, H.; Glozman, L. Ya.; Hashimoto, S.; Lang, C. B.; Prelovsek, S.

2017-11-01

We study spatial isovector meson correlators in Nf=2 QCD with dynamical domain-wall fermions on 3 23×8 lattices at temperatures T =220 - 380 MeV . We measure the correlators of spin-one (J =1 ) operators including vector, axial-vector, tensor and axial-tensor. Restoration of chiral U (1 )A and S U (2 )L×S U (2 )R symmetries of QCD implies degeneracies in vector-axial-vector (S U (2 )L×S U (2 )R) and tensor-axial-tensor (U (1 )A) pairs, which are indeed observed at temperatures above Tc. Moreover, we observe an approximate degeneracy of all J =1 correlators with increasing temperature. This approximate degeneracy suggests emergent S U (2 )CS and S U (4 ) symmetries at high temperatures, that mix left- and right-handed quarks.

Renormalizable Quantum Field Theories in the Large -n Limit

NASA Astrophysics Data System (ADS)

Guruswamy, Sathya

1995-01-01

In this thesis, we study two examples of renormalizable quantum field theories in the large-N limit. Chapter one is a general introduction describing physical motivations for studying such theories. In chapter two, we describe the large-N method in field theory and discuss the pioneering work of 't Hooft in large-N two-dimensional Quantum Chromodynamics (QCD). In chapter three we study a spherically symmetric approximation to four-dimensional QCD ('spherical QCD'). We recast spherical QCD into a bilocal (constrained) theory of hadrons which in the large-N limit is equivalent to large-N spherical QCD for all energy scales. The linear approximation to this theory gives an eigenvalue equation which is the analogue of the well-known 't Hooft's integral equation in two dimensions. This eigenvalue equation is a scale invariant one and therefore leads to divergences in the theory. We give a non-perturbative renormalization prescription to cure this and obtain a beta function which shows that large-N spherical QCD is asymptotically free. In chapter four, we review the essentials of conformal field theories in two and higher dimensions, particularly in the context of critical phenomena. In chapter five, we study the O(N) non-linear sigma model on three-dimensional curved spaces in the large-N limit and show that there is a non-trivial ultraviolet stable critical point at which it becomes conformally invariant. We study this model at this critical point on examples of spaces of constant curvature and compute the mass gap in the theory, the free energy density (which turns out to be a universal function of the information contained in the geometry of the manifold) and the two-point correlation functions. The results we get give an indication that this model is an example of a three-dimensional analogue of a rational conformal field theory. A conclusion with a brief summary and remarks follows at the end.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.

Light-Front Quantization – Dirac’s “Front Form” – provides a physical, frame-independent formalism for hadron dynamics and structure. Observables such as structure functions, transverse momentum distributions, and distribution amplitudes are defined from the hadronic LFWFs. One obtains new insights into the hadronic mass scale, the hadronic spectrum, and the functional form of the QCD running coupling in the nonperturbative domain using light-front holography. In addition, superconformal algebra leads to remarkable supersymmetric relations between mesons and baryons. I also discuss evidence that the antishadowing of nuclear structure functions is nonuniversal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatiblemore » with the momentum and other sum rules for the nuclear parton distribution functions.« less

Next-to-leading order QCD predictions for top-quark pair production with up to three jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Höche, S.; Maierhöfer, P.; Moretti, N.

2017-03-07

Here, we present theoretical predictions for the production of top-quark pairs with up to three jets at the next-to leading order in perturbative QCD. The relevant calculations are performed with Sherpa and OpenLoops. In order to address the issue of scale choices and related uncertainties in the presence of multiple scales, we compare results obtained with the standard scale HT/2HT/2 at fixed order and the MiNLO procedure. By analyzing various cross sections and distributions for tmore » $$\\bar{t}$$+0,1,2,3 jets at the 13 TeV LHC we found a remarkable overall agreement between fixed-order and MiNLO results. The differences are typically below the respective factor-two scale variations, suggesting that for all considered jet multiplicities missing higher-order effects should not exceed the ten percent level.« less

The large-N Yang-Mills S matrix is ultraviolet finite, but the large-N QCD S matrix is only renormalizable

NASA Astrophysics Data System (ADS)

Bochicchio, Marco

2017-03-01

Yang-Mills (YM) theory and QCD are known to be renormalizable, but not ultraviolet (UV) finite, order by order, in perturbation theory. It is a fundamental question whether YM theory or QCD is UV finite, or only renormalizable, order by order, in the large-N 't Hooft or Veneziano expansions. We demonstrate that the renormalization group (RG) and asymptotic freedom imply that in 't Hooft large-N expansion the S matrix in YM theory is UV finite, while in both 't Hooft and Veneziano large-N expansions, the S matrix in confining massless QCD is renormalizable but not UV finite. By the same argument, the large-N N =1 supersymmetry (SUSY) YM S matrix is UV finite as well. Besides, we demonstrate that, in both 't Hooft and Veneziano large-N expansions, the correlators of local gauge-invariant operators, as opposed to the S matrix, are renormalizable but, in general, not UV finite, either in YM theory and N =1 SUSY YM theory or a fortiori in massless QCD. Moreover, we compute explicitly the counterterms that arise from renormalizing the 't Hooft and Veneziano expansions by deriving in confining massless QCD-like theories a low-energy theorem of the Novikov-Shifman-Vainshtein-Zakharov type that relates the log derivative with respect to the gauge coupling of a k -point correlator, or the log derivative with respect to the RG-invariant scale, to a (k +1 )-point correlator with the insertion of Tr F2 at zero momentum. Finally, we argue that similar results hold in the large-N limit of a vast class of confining massive QCD-like theories, provided a renormalization scheme exists—as, for example, MS ¯ —in which the beta function is not dependent on the masses. Specifically, in both 't Hooft and Veneziano large-N expansions, the S matrix in confining massive QCD and massive N =1 SUSY QCD is renormalizable but not UV finite.

Factorization and resummation of Higgs boson differential distributions in soft-collinear effective theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mantry, Sonny; Petriello, Frank

We derive a factorization theorem for the Higgs boson transverse momentum (p{sub T}) and rapidity (Y) distributions at hadron colliders, using the soft-collinear effective theory (SCET), for m{sub h}>>p{sub T}>>{Lambda}{sub QCD}, where m{sub h} denotes the Higgs mass. In addition to the factorization of the various scales involved, the perturbative physics at the p{sub T} scale is further factorized into two collinear impact-parameter beam functions (IBFs) and an inverse soft function (ISF). These newly defined functions are of a universal nature for the study of differential distributions at hadron colliders. The additional factorization of the p{sub T}-scale physics simplifies themore » implementation of higher order radiative corrections in {alpha}{sub s}(p{sub T}). We derive formulas for factorization in both momentum and impact parameter space and discuss the relationship between them. Large logarithms of the relevant scales in the problem are summed using the renormalization group equations of the effective theories. Power corrections to the factorization theorem in p{sub T}/m{sub h} and {Lambda}{sub QCD}/p{sub T} can be systematically derived. We perform multiple consistency checks on our factorization theorem including a comparison with known fixed-order QCD results. We compare the SCET factorization theorem with the Collins-Soper-Sterman approach to low-p{sub T} resummation.« less

First Monte Carlo Global Analysis of Nucleon Transversity with Lattice QCD Constraints

DOE PAGES

Lin, Huey-Wen; Melnitchouk, Wally; Prokudin, Alexei; ...

2018-04-11

We report on the first global QCD analysis of the quark transversity distributions in the nucleon from semi-inclusive deep-inelastic scattering (SIDIS), using a new Monte Carlo method based on nested sampling and constraints on the isovector tensor chargemore » $$g_T$$ from lattice QCD. A simultaneous fit to the available SIDIS Collins asymmetry data is compatible with $$g_T$$ values extracted from a comprehensive reanalysis of existing lattice simulations, in contrast to previous analyses, which found significantly smaller $$g_T$$ values. The contributions to the nucleon tensor charge from $u$ and $d$ quarks are found to be $$\\delta u = 0.3(2)$$ and $$\\delta d = -0.7(2)$$ at a scale $Q^2 = 2$ GeV$^2$.« less

First Monte Carlo Global Analysis of Nucleon Transversity with Lattice QCD Constraints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Huey-Wen; Melnitchouk, Wally; Prokudin, Alexei

We report on the first global QCD analysis of the quark transversity distributions in the nucleon from semi-inclusive deep-inelastic scattering (SIDIS), using a new Monte Carlo method based on nested sampling and constraints on the isovector tensor chargemore » $$g_T$$ from lattice QCD. A simultaneous fit to the available SIDIS Collins asymmetry data is compatible with $$g_T$$ values extracted from a comprehensive reanalysis of existing lattice simulations, in contrast to previous analyses, which found significantly smaller $$g_T$$ values. The contributions to the nucleon tensor charge from $u$ and $d$ quarks are found to be $$\\delta u = 0.3(2)$$ and $$\\delta d = -0.7(2)$$ at a scale $Q^2 = 2$ GeV$^2$.« less

First Monte Carlo Global Analysis of Nucleon Transversity with Lattice QCD Constraints.

PubMed

Lin, H-W; Melnitchouk, W; Prokudin, A; Sato, N; Shows, H

2018-04-13

We report on the first global QCD analysis of the quark transversity distributions in the nucleon from semi-inclusive deep-inelastic scattering (SIDIS), using a new Monte Carlo method based on nested sampling and constraints on the isovector tensor charge g_{T} from lattice QCD. A simultaneous fit to the available SIDIS Collins asymmetry data is compatible with g_{T} values extracted from a comprehensive reanalysis of existing lattice simulations, in contrast to previous analyses, which found significantly smaller g_{T} values. The contributions to the nucleon tensor charge from u and d quarks are found to be δu=0.3(2) and δd=-0.7(2) at a scale Q^{2}=2  GeV^{2}.

First Monte Carlo Global Analysis of Nucleon Transversity with Lattice QCD Constraints

NASA Astrophysics Data System (ADS)

Lin, H.-W.; Melnitchouk, W.; Prokudin, A.; Sato, N.; Shows, H.; Jefferson Lab Angular Momentum JAM Collaboration

2018-04-01

We report on the first global QCD analysis of the quark transversity distributions in the nucleon from semi-inclusive deep-inelastic scattering (SIDIS), using a new Monte Carlo method based on nested sampling and constraints on the isovector tensor charge gT from lattice QCD. A simultaneous fit to the available SIDIS Collins asymmetry data is compatible with gT values extracted from a comprehensive reanalysis of existing lattice simulations, in contrast to previous analyses, which found significantly smaller gT values. The contributions to the nucleon tensor charge from u and d quarks are found to be δ u =0.3 (2 ) and δ d =-0.7 (2 ) at a scale Q2=2 GeV2.

High-precision QCD at hadron colliders:electroweak gauge boson rapidity distributions at NNLO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anastasiou, C.

2004-01-05

We compute the rapidity distributions of W and Z bosons produced at the Tevatron and the LHC through next-to-next-to leading order in QCD. Our results demonstrate remarkable stability with respect to variations of the factorization and renormalization scales for all values of rapidity accessible in current and future experiments. These processes are therefore ''gold-plated'': current theoretical knowledge yields QCD predictions accurate to better than one percent. These results strengthen the proposal to use $W$ and $Z$ production to determine parton-parton luminosities and constrain parton distribution functions at the LHC. For example, LHC data should easily be able to distinguish themore » central parton distribution fit obtained by MRST from that obtained by Alekhin.« less

Next-to-leading order QCD corrections to W{sup +}W{sup +}jj and W{sup -}W{sup -}jj production via weak-boson fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaeger, B.; Oleari, C.; Zeppenfeld, D.

2009-08-01

We present a next-to-leading order QCD calculation for e{sup +}{nu}{sub e}{mu}{sup +}{nu}{sub {mu}}jj and e{sup -}{nu}{sub e}{mu}{sup -}{nu}{sub {mu}}jj production via weak-boson fusion at a hadron collider in the form of a fully flexible parton-level Monte Carlo program, which allows for the calculation of experimentally accessible observables within realistic selection cuts. The QCD corrections to the integrated cross sections are found to be modest, while the shapes of some kinematical distributions change appreciably compared to leading order. The residual scale uncertainties of the next-to-leading order results are at the few-percent level.

Shear viscosity of the quark-gluon plasma in a weak magnetic field in perturbative QCD: Leading log

NASA Astrophysics Data System (ADS)

Li, Shiyong; Yee, Ho-Ung

2018-03-01

We compute the shear viscosity of two-flavor QCD plasma in an external magnetic field in perturbative QCD at leading log order, assuming that the magnetic field is weak or soft: e B ˜g4log (1 /g )T2. We work in the assumption that the magnetic field is homogeneous and static, and the electrodynamics is nondynamical in a formal limit e →0 while e B is kept fixed. We show that the shear viscosity takes a form η =η ¯(B ¯)T3/(g4log (1 /g )) with a dimensionless function η ¯(B ¯) in terms of a dimensionless variable B ¯=(e B )/(g4log (1 /g )T2). The variable B ¯ corresponds to the relative strength of the effect of cyclotron motions compared to the QCD collisions: B ¯˜lmfp/lcyclo. We provide a full numerical result for the scaled shear viscosity η ¯(B ¯).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caola, Fabrizio; Melnikov, Kirill; Rontsch, Raoul

We compute the next-to-leading-order QCD corrections to the production of two Z-bosons in the annihilation of two gluons at the LHC. Being enhanced by a large gluon flux, these corrections provide a distinct and, potentially, the dominant part of the N 3LO QCD contributions to Z-pair production in proton collisions. The gg → ZZ annihilation is a loop-induced process that receives the dominant contribution from loops of five light quarks, that are included in our computation in the massless approximation. We find that QCD corrections increase the gg → ZZ production cross section by O(50%–100%) depending on the values ofmore » the renormalization and factorization scales used in the leading-order computation and the collider energy. Furthermore, the large corrections to the gg → ZZ channel increase the pp → ZZ cross section by about 6% to 8%, exceeding the estimated theoretical uncertainty of the recent next-to-next-to-leading-order QCD calculation.« less

Symmetries and mass splittings QCD 2 coupled to adjoint fermions

NASA Astrophysics Data System (ADS)

Boorstein, Joshua; Kutasov, David

1994-06-01

Two-dimensional QCD coupled to fermions in the adjoint representation of the gauge group SU( N), a useful toy model of QCD strings, is supersymmetric for a certain ratio of quark mass and gauge coupling constant. Here we study the theory in the vicinity of the supersymmetric point; in particular we exhibit the algebraic structure of the model and show that the mass splittings as one moves away from the supersymmetric point obey a universal relation of the form Mi2(B)- Mi2(F) = Miδm + O( δm3). We discuss the connection of this relation to string and quark model expectations and verify it numerically for large N. At least for low lying states the O( δm3) corrections are extremely small. We also discuss a natural generalization of QCD 2 with an infinite number of couplings, which preserves SUSY. This leads to a Landau-Ginzburg description of the theory, and may be useful for defining a scaling limit in which smooth worldsheets appear.

Weak vector boson production with many jets at the LHC √{s }=13 TeV

NASA Astrophysics Data System (ADS)

Anger, F. R.; Febres Cordero, F.; Höche, S.; Maître, D.

2018-05-01

Signatures with an electroweak vector boson and many jets play a crucial role at the Large Hadron Collider, both in the measurement of Standard-Model parameters and in searches for new physics. Precise predictions for these multiscale processes are therefore indispensable. We present next-to-leading order QCD predictions for W±/Z +jets at √{s }=13 TeV , including up to five/four jets in the final state. All production channels are included, and leptonic decays of the vector bosons are considered at the amplitude level. We assess theoretical uncertainties arising from renormalization- and factorization-scale dependence by considering fixed-order dynamical scales based on the HT variable as well as on the MiNLO procedure. We also explore uncertainties associated with different choices of parton-distribution functions. We provide event samples that can be explored through publicly available n -tuple sets, generated with BlackHat in combination with Sherpa.

The infrared behaviour of QCD Green's functions. Confinement, dynamical symmetry breaking, and hadrons as relativistic bound states

NASA Astrophysics Data System (ADS)

Alkofer, Reinhard; von Smekal, Lorenz

2001-11-01

Recent studies of QCD Green's functions and their applications in hadronic physics are reviewed. We discuss the definition of the generating functional in gauge theories, in particular, the rôle of redundant degrees of freedom, possibilities of a complete gauge fixing versus gauge fixing in presence of Gribov copies, BRS invariance and positivity. The apparent contradiction between positivity and colour antiscreening in combination with BRS invariance in QCD is considered. Evidence for the violation of positivity by quarks and transverse gluons in the covariant gauge is collected, and it is argued that this is one manifestation of confinement. We summarise the derivation of the Dyson-Schwinger equations (DSEs) of QED and QCD. For the latter, the implications of BRS invariance on the Green's functions are explored. The possible influence of instantons on DSEs is discussed in a two-dimensional model. In QED in (2+1) and (3+1) dimensions, the solutions for Green's functions provide tests of truncation schemes which can under certain circumstances be extended to the DSEs of QCD. We discuss some limitations of such extensions and assess the validity of assumptions for QCD as motivated from studies in QED. Truncation schemes for DSEs are discussed in axial and related gauges, as well as in the Landau gauge. Furthermore, we review the available results from a systematic non-perturbative expansion scheme established for Landau gauge QCD. Comparisons to related lattice results, where available, are presented. The applications of QCD Green's functions to hadron physics are summarised. Properties of ground state mesons are discussed on the basis of the ladder Bethe-Salpeter equation for quarks and antiquarks. The Goldstone nature of pseudoscalar mesons and a mechanism for diquark confinement beyond the ladder approximation are reviewed. We discuss some properties of ground state baryons based on their description as Bethe-Salpeter/Faddeev bound states of quark-diquark correlations in the quantum field theory of confined quarks and gluons.

Measurement of the structure functions F 2 and xF 3 and comparison with QCD predictions including kinematical and dynamical higher twist effects

NASA Astrophysics Data System (ADS)

Varvell, K.; Cooper-Sarkar, A. M.; Parker, M. A.; Sansum, R. A.; Aderholz, M.; Armenise, N.; Baton, J. P.; Bullock, F. W.; Berggren, M.; Bertrand, D.; Brisson, V.; Burkot, W.; Calcchio, M.; Claytoh, E. F.; Coghen, T.; Erriquez, O.; Fitch, P. J.; Gerbier, G.; Guy, J.; Hulth, P. O.; Iaselli, G.; Jones, G. T.; Kasper, P.; Klein, H.; Kochowski, C.; Marage, P.; Mermikides, M.; Middleton, R. P.; Morrison, D. R. O.; Mobayyen, M. M.; Natali, S.; Neveu, M.; Nuzzo, S.; O'Neale, S. W.; Petiau, P.; Petrides, A.; Ruggieri, F.; Sacton, J.; Simopoulou, E.; Vallee, C.; Vayaki, A.; Venus, W. A.; Wachsmuth, H.; Wells, J.; Wittek, W.

1987-03-01

The isoscalar nucleon structure functions F 2( x, Q 2) and xF 3( x, Q 2) are measured in the range 0< Q 2<64 GeV2, 1.7< W 2<250 GeV2, x<0.7 using ν andbar v interactions on neon in BEBC. The data are used to evaluate possible higher twist contributions and to determine their impact on the evaluation of the QCD parameter Λ. In contrast to previous analyses reaching to such low W 2 values, it is found that a lowΛ _{overline {MS} } value in the neighbourhood of 100 MeV describes the data adequately and that the contribution of dynamical higher twist effects is small and negative.

VINCIA for hadron colliders

DOE PAGES

Fischer, Nadine; Prestel, S.; Ritzmann, M.; ...

2016-10-28

We present the first public implementation of antenna-based QCD initial- and final-state showers. The shower kernels are 2→3 antenna functions, which capture not only the collinear dynamics but also the leading soft (coherent) singularities of QCD matrix elements. We define the evolution measure to be inversely proportional to the leading poles, hence gluon emissions are evolved in a p ⊥ measure inversely proportional to the eikonal, while processes that only contain a single pole (e.g., g → qq¯) are evolved in virtuality. Non-ordered emissions are allowed, suppressed by an additional power of 1/Q 2. Recoils and kinematics are governed bymore » exact on-shell 2 → 3 phase-space factorisations. This first implementation is limited to massless QCD partons and colourless resonances. Tree-level matrix-element corrections are included for QCD up to O(α 4 s) (4 jets), and for Drell–Yan and Higgs production up to O(α 3 s) (V / H + 3 jets). Finally, the resulting algorithm has been made publicly available in Vincia 2.0.« less

QCD nature of dark energy at finite temperature: Cosmological implications

NASA Astrophysics Data System (ADS)

Azizi, K.; Katırcı, N.

2016-05-01

The Veneziano ghost field has been proposed as an alternative source of dark energy, whose energy density is consistent with the cosmological observations. In this model, the energy density of the QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from late time to early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras. It is found that this model safely defines the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The EoS parameter of dark energy is dynamical and evolves from -1/3 in the presence of radiation to -1 at late time. The finite temperature ghost dark energy predictions on the Hubble parameter well fit to those of Λ CDM and observations at late time.

Topology in the SU(Nf) chiral symmetry restored phase of unquenched QCD and axion cosmology

NASA Astrophysics Data System (ADS)

Azcoiti, Vicente

2018-03-01

The axion is one of the more interesting candidates to make the dark matter of the universe, and the axion potential plays a fundamental role in the determination of the dynamics of the axion field. Moreover, the way in which the U(1)A anomaly manifests itself in the chiral symmetry restored phase of QCD at high temperature could be tested when probing the QCD phase transition in relativistic heavy ion collisions. With these motivations, we investigate the physical consequences of the survival of the effects of the U(1)A anomaly in the chiral symmetric phase of QCD, and show that the free energy density is a singular function of the quark mass m, in the chiral limit, and that the σ and π susceptibilities diverge in this limit at any T ≥ Tc. We also show that the difference between the π and t;δ susceptibilities diverges in the chiral limit at any T ≥ Tc, a result that can be contrasted with the existing lattice calculations; and discuss on the generalization of these results to the Nf ≥ 3 model.

Towards a unified description of total and diffractive structure functions at DESY HERA in the QCD dipole picture

NASA Astrophysics Data System (ADS)

Bialas, A.; Peschanski, R.; Royon, Ch.

1998-06-01

It is argued that the QCD dipole picture allows us to build a unified theoretical description, based on Balitskii-Fadin-Kuraev-Lipatov dynamics, of the total and diffractive nucleon structure functions. This description is in qualitative agreement with the present collection of data obtained by the H1 Collaboration. More precise theoretical estimates, in particular the determination of the normalizations and proton transverse momentum behavior of the diffractive components, are shown to be required in order to reach definite conclusions.

Lattice field theory applications in high energy physics

NASA Astrophysics Data System (ADS)

Gottlieb, Steven

2016-10-01

Lattice gauge theory was formulated by Kenneth Wilson in 1974. In the ensuing decades, improvements in actions, algorithms, and computers have enabled tremendous progress in QCD, to the point where lattice calculations can yield sub-percent level precision for some quantities. Beyond QCD, lattice methods are being used to explore possible beyond the standard model (BSM) theories of dynamical symmetry breaking and supersymmetry. We survey progress in extracting information about the parameters of the standard model by confronting lattice calculations with experimental results and searching for evidence of BSM effects.

Chiral dynamics in the low-temperature phase of QCD

NASA Astrophysics Data System (ADS)

Brandt, Bastian B.; Francis, Anthony; Meyer, Harvey B.; Robaina, Daniel

2014-09-01

We investigate the low-temperature phase of QCD and the crossover region with two light flavors of quarks. The chiral expansion around the point (T,m=0) in the temperature vs quark-mass plane indicates that a sharp real-time excitation exists with the quantum numbers of the pion. An exact sum rule is derived for the thermal modification of the spectral function associated with the axial charge density; the (dominant) pion pole contribution obeys the sum rule. We determine the two parameters of the pion dispersion relation using lattice QCD simulations and test the applicability of the chiral expansion. The time-dependent correlators are also analyzed using the maximum entropy method, yielding consistent results. Finally, we test the predictions of the chiral expansion around the point (T=0,m=0) for the temperature dependence of static observables.

C P -odd sector and θ dynamics in holographic QCD

NASA Astrophysics Data System (ADS)

Areán, Daniel; Iatrakis, Ioannis; Järvinen, Matti; Kiritsis, Elias

2017-07-01

The holographic model of V-QCD is used to analyze the physics of QCD in the Veneziano large-N limit. An unprecedented analysis of the C P -odd physics is performed going beyond the level of effective field theories. The structure of holographic saddle points at finite θ is determined, as well as its interplay with chiral symmetry breaking. Many observables (vacuum energy and higher-order susceptibilities, singlet and nonsinglet masses and mixings) are computed as functions of θ and the quark mass m . Wherever applicable the results are compared to those of chiral Lagrangians, finding agreement. In particular, we recover the Witten-Veneziano formula in the small x →0 limit, we compute the θ dependence of the pion mass, and we derive the hyperscaling relation for the topological susceptibility in the conformal window in terms of the quark mass.

The Evolution of Soft Collinear Effective Theory

DOE PAGES

Lee, Christopher

2015-02-25

Soft Collinear Effective Theory (SCET) is an effective field theory of Quantum Chromodynamics (QCD) for processes where there are energetic, nearly lightlike degrees of freedom interacting with one another via soft radiation. SCET has found many applications in high-energy and nuclear physics, especially in recent years the physics of hadronic jets in e +e -, lepton-hadron, hadron-hadron, and heavy-ion collisions. SCET can be used to factorize multi-scale cross sections in these processes into single-scale hard, collinear, and soft functions, and to evolve these through the renormalization group to resum large logarithms of ratios of the scales that appear in themore » QCD perturbative expansion, as well as to study properties of nonperturbative effects. We overview the elementary concepts of SCET and describe how they can be applied in high-energy and nuclear physics.« less

NLO QCD corrections to B c( B*c) production around the Z pole at an e + e - collider

NASA Astrophysics Data System (ADS)

Zheng, XuChang; Chang, ChaoHsi; Feng, TaiFu; Pan, Zan

2018-03-01

The production of B c and B*c mesons at a Z-factory (an e + e - collider operating at energies around the Z pole) is calculated up to the next-to-leading order (NLO) QCD accuracy. The results show that the dependence of the total cross sections on the renormalization scale μ is suppressed by the corrections, and the NLO corrections enhance the total cross sections of B c by 52% and of B*c by 33% when the renormalization scale is taken at μ = 2 m b . To observe the various behaviors of the production of the mesons B c and B*c, such as the differential cross section vs. the out-going angle, the forward-backward asymmetry, and the distribution vs. the energy fraction z up to NLO QCD accuracy as well as the relevant K-factor (NLO to LO) for the production, are calculated, and it is pointed out that some of the observables obtained in the present work may be used as a specific precision test of the standard model.

Relaxation of the composite Higgs little hierarchy

NASA Astrophysics Data System (ADS)

Batell, Brian; Fedderke, Michael A.; Wang, Lian-Tao

2017-12-01

We describe a composite Higgs scenario in which a cosmological relaxation mechanism naturally gives rise to a hierarchy between the weak scale and the scale of spontaneous global symmetry breaking. This is achieved through the scanning of sources of explicit global symmetry breaking by a relaxion field during an exponentially long period of inflation in the early universe. We explore this mechanism in detail in a specific composite Higgs scenario with QCD-like dynamics, based on an ultraviolet SU( N )TC `technicolor' confining gauge theory with three Dirac technifermion flavors. We find that we can successfully generate a hierarchy of scales ξ≡〈 h〉2/ F π 2 ≳ 1.2 × 10- 4 (i.e., compositeness scales F π ˜ 20 TeV) without tuning. This evades all current electroweak precision bounds on our (custodial violating) model. While directly observing the heavy composite states in this model will be challenging, a future electroweak precision measurement program can probe most of the natural parameter space for the model. We also highlight signatures of more general composite Higgs models in the cosmological relaxation framework, including some implications for flavor and dark matter.

QCD Axion Dark Matter with a Small Decay Constant

NASA Astrophysics Data System (ADS)

Co, Raymond T.; Hall, Lawrence J.; Harigaya, Keisuke

2018-05-01

The QCD axion is a good dark matter candidate. The observed dark matter abundance can arise from misalignment or defect mechanisms, which generically require an axion decay constant fa˜O (1011) GeV (or higher). We introduce a new cosmological origin for axion dark matter, parametric resonance from oscillations of the Peccei-Quinn symmetry breaking field, that requires fa˜(108- 1011) GeV . The axions may be warm enough to give deviations from cold dark matter in large scale structure.

Perturbative corrections to B → D form factors in QCD

NASA Astrophysics Data System (ADS)

Wang, Yu-Ming; Wei, Yan-Bing; Shen, Yue-Long; Lü, Cai-Dian

2017-06-01

We compute perturbative QCD corrections to B → D form factors at leading power in Λ/ m b , at large hadronic recoil, from the light-cone sum rules (LCSR) with B-meson distribution amplitudes in HQET. QCD factorization for the vacuum-to- B-meson correlation function with an interpolating current for the D-meson is demonstrated explicitly at one loop with the power counting scheme {m}_c˜ O(√{Λ {m}_b}) . The jet functions encoding information of the hard-collinear dynamics in the above-mentioned correlation function are complicated by the appearance of an additional hard-collinear scale m c , compared to the counterparts entering the factorization formula of the vacuum-to- B-meson correction function for the construction of B → π from factors. Inspecting the next-to-leading-logarithmic sum rules for the form factors of B → Dℓν indicates that perturbative corrections to the hard-collinear functions are more profound than that for the hard functions, with the default theory inputs, in the physical kinematic region. We further compute the subleading power correction induced by the three-particle quark-gluon distribution amplitudes of the B-meson at tree level employing the background gluon field approach. The LCSR predictions for the semileptonic B → Dℓν form factors are then extrapolated to the entire kinematic region with the z-series parametrization. Phenomenological implications of our determinations for the form factors f BD +,0 ( q 2) are explored by investigating the (differential) branching fractions and the R( D) ratio of B → Dℓν and by determining the CKM matrix element |V cb | from the total decay rate of B → Dμν μ .

Holograms of a dynamical top quark

NASA Astrophysics Data System (ADS)

Clemens, Will; Evans, Nick; Scott, Marc

2017-09-01

We present holographic descriptions of dynamical electroweak symmetry breaking models that incorporate the top mass generation mechanism. The models allow computation of the spectrum in the presence of large anomalous dimensions due to walking and strong Nambu-Jona-Lasinio interactions. Technicolor and QCD dynamics are described by the bottom-up Dynamic AdS/QCD model for arbitrary gauge groups and numbers of quark flavors. An assumption about the running of the anomalous dimension of the quark bilinear operator is input, and the model then predicts the spectrum and decay constants for the mesons. We add Nambu-Jona-Lasinio interactions responsible for flavor physics from extended technicolor, top-color, etc., using Witten's multitrace prescription. We show the key behaviors of a top condensation model can be reproduced. We study generation of the top mass in (walking) one doublet and one family technicolor models and with strong extended technicolor interactions. The models clearly reveal the tensions between the large top mass and precision data for δ ρ . The necessary tunings needed to generate a model compatible with precision constraints are simply demonstrated.

Calculation of shear viscosity using Green-Kubo relations within a parton cascade

NASA Astrophysics Data System (ADS)

Wesp, C.; El, A.; Reining, F.; Xu, Z.; Bouras, I.; Greiner, C.

2011-11-01

The shear viscosity of a gluon gas is calculated using the Green-Kubo relation. Time correlations of the energy-momentum tensor in thermal equilibrium are extracted from microscopic simulations using a parton cascade solving various Boltzmann collision processes. We find that the perturbation-QCD- (pQCD-) based gluon bremsstrahlung described by Gunion-Bertsch processes significantly lowers the shear viscosity by a factor of 3 to 8 compared to elastic scatterings. The shear viscosity scales with the coupling as η˜1/[αs2log(1/αs)]. For constant αs the shear viscosity to entropy density ratio η/s has no dependence on temperature. Replacing the pQCD-based collision angle distribution of binary scatterings by an isotropic form decreases the shear viscosity by a factor of 3.

Energy dependence of Kπ, pπ and Kp fluctuations in Au+Au collisions from √s NN=7.7 to 200 GeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamczyk, L.

A search for the quantum chromodynamics (QCD) critical point was performed by the STAR experiment at the Relativistic Heavy Ion Collider, using dynamical fluctuations of unlike particle pairs. Heavy ion collisions were studied over a large range of collision energies with homogeneous acceptance and excellent particle identification, covering a significant range in the QCD phase diagram where a critical point may be located. Dynamical Kπ, pπ, and Kp fluctuations as measured by the STAR experiment in central 0–5% Au+Au collisions from center-of-mass collision energies √s NN=7.7 to 200 GeV are presented. The observable νdyn was used to quantify the magnitudemore » of the dynamical fluctuations in event-by-event measurements of the Kπ, pπ, and Kp pairs. The energy dependences of these fluctuations from central 0–5% Au+Au collisions all demonstrate a smooth evolution with collision energy.« less

Testing the QCD string at large Nc from the thermodynamics of the hadronic phase

NASA Astrophysics Data System (ADS)

Cohen, Thomas D.

2007-02-01

It is generally believed that in the limit of a large number of colors (Nc) the description of confinement via flux tubes becomes valid and QCD can be modeled accurately via a hadronic string theory—at least for highly excited states. QCD at large Nc also has a well-defined deconfinement transition at a temperature Tc. In this talk it is shown how the thermodyanmics of the metastable hadronic phase of QCD (above Tc) at large NC can be related directly to properties of the effective QCD string. The key points in the derivation is the weakly interacting nature of hadrons at large Nc and the existence of a Hagedorn temperature TH for the effective string theory. From this it can be seen at large Nc and near TH, the energy density and pressure of the hadronic phase scale as E ˜ (TH - T)-(D⊥-6)/2 (for D⊥ < 6) and P ˜ (TH - T)-(D⊥-4)/2 (for D⊥ < 4) where D⊥ is the effective number of transverse dimensions of the string theory. This behavior for D⊥ < 6 is qualitatively different from typical models in statistical mechanics and if observed on the lattice would provide a direct test of the stringy nature of large Nc QCD. However since it can be seen that TH > Tc this behavior is of relevance only to the metastable phase. The prospect of using this result to extract D⊥ via lattice simulations of the metastable hadronic phase at moderately large Nc is discussed.

Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.

2012-02-16

Light-Front Holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations it provides important physical insights into the nonperturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z inmore » AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions, and thus the fall-off as a function of the invariant mass of the constituents. The soft-wall holographic model modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics - a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions {Psi}{sub n/H} (x{sub i}, k{sub {perpendicular}i}, {lambda}{sub i}) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark and gluon level, such as elastic and transition form factors, distribution amplitudes, structure functions, generalized parton distributions and transverse momentum distributions. The effective confining potential also creates quark-antiquark pairs from the amplitude q {yields} q{bar q}q. Thus in holographic QCD higher Fock states can have any number of extra q{bar q} pairs. We discuss the relevance of higher Fock-states for describing the detailed structure of space and time-like form factors. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also obtained.« less

Non-perturbative quark mass renormalisation and running in N_{f}=3 QCD

NASA Astrophysics Data System (ADS)

Campos, I.; Fritzsch, P.; Pena, C.; Preti, D.; Ramos, A.; Vladikas, A.

2018-05-01

We determine from first principles the quark mass anomalous dimension in N_{f}=3 QCD between the electroweak and hadronic scales. This allows for a fully non-perturbative connection of the perturbative and non-perturbative regimes of the Standard Model in the hadronic sector. The computation is carried out to high accuracy, employing massless O (a)-improved Wilson quarks and finite-size scaling techniques. We also provide the matching factors required in the renormalisation of light quark masses from lattice computations with O (a)-improved Wilson fermions and a tree-level Symanzik improved gauge action. The total uncertainty due to renormalisation and running in the determination of light quark masses in the SM is thus reduced to about 1%.

Cosmological evolution of the Higgs boson's vacuum expectation value

NASA Astrophysics Data System (ADS)

Calmet, Xavier

2017-11-01

We point out that the expansion of the universe leads to a cosmological time evolution of the vacuum expectation of the Higgs boson. Within the standard model of particle physics, the cosmological time evolution of the vacuum expectation of the Higgs leads to a cosmological time evolution of the masses of the fermions and of the electroweak gauge bosons, while the scale of Quantum Chromodynamics (QCD) remains constant. Precise measurements of the cosmological time evolution of μ =m_e/m_p, where m_e and m_p are, respectively, the electron and proton mass (which is essentially determined by the QCD scale), therefore provide a test of the standard models of particle physics and of cosmology. This ratio can be measured using modern atomic clocks.

Locating the Gribov horizon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Fei; Qin, Si-Xue; Roberts, Craig D.

We explore whether a tree-level expression for the gluon two-point function, supposed to express effects of an horizon term introduced to eliminate the Gribov ambiguity, is consistent with the propagator obtained in simulations of lattice-regularised quantum chromodynamics (QCD). In doing so, we insist that the gluon two-point function obey constraints that ensure a minimal level of consistency with parton-like behaviour at ultraviolet momenta. In consequence, we are led to a position which supports a conjecture that the gluon mass and horizon scale are equivalent emergent massscales, each with a value of roughly 0.5 GeV; and wherefrom it appears plausible thatmore » the dynamical generation of a running gluon mass may alone be sufficient to remove the Gribov ambiguity.« less

Locating the Gribov horizon

DOE PAGES

Gao, Fei; Qin, Si-Xue; Roberts, Craig D.; ...

2018-02-08

We explore whether a tree-level expression for the gluon two-point function, supposed to express effects of an horizon term introduced to eliminate the Gribov ambiguity, is consistent with the propagator obtained in simulations of lattice-regularised quantum chromodynamics (QCD). In doing so, we insist that the gluon two-point function obey constraints that ensure a minimal level of consistency with parton-like behaviour at ultraviolet momenta. In consequence, we are led to a position which supports a conjecture that the gluon mass and horizon scale are equivalent emergent massscales, each with a value of roughly 0.5 GeV; and wherefrom it appears plausible thatmore » the dynamical generation of a running gluon mass may alone be sufficient to remove the Gribov ambiguity.« less

A lattice calculation of the hadronic vacuum polarization contribution to (g - 2)µ

NASA Astrophysics Data System (ADS)

Della Morte, M.; Francis, A.; Gérardin, A.; Gülpers, V.; Herdoíza, G.; von Hippel, G.; Horch, H.; Jäger, B.; Meyer, H. B.; Nyffeler, A.; Wittig, H.

2018-03-01

We present results of calculations of the hadronic vacuum polarisation contribution to the muon anomalous magnetic moment. Specifically, we focus on controlling the infrared regime of the vacuum polarisation function. Our results are corrected for finite-size effects by combining the Gounaris-Sakurai parameterisation of the timelike pion form factor with the Lüscher formalism. The impact of quark-disconnected diagrams and the precision of the scale determination is discussed and included in our final result in two-flavour QCD, which carries an overall uncertainty of 6%. We present preliminary results computed on ensembles with Nf = 2 + 1 dynamical flavours and discuss how the long-distance contribution can be accurately constrained by a dedicated spectrum calculation in the iso-vector channel.

Prompt atmospheric neutrino fluxes: perturbative QCD models and nuclear effects

DOE PAGES

Bhattacharya, Atri; Enberg, Rikard; Jeong, Yu Seon; ...

2016-11-28

We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, k T factorization including low-x resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest datamore » on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we investigate the role of nuclear shadowing by including nuclear parton distribution functions (PDF) for the target air nucleus using two different nuclear PDF schemes. Depending on the scheme used, we find the reduction of the flux due to nuclear effects varies from 10% to 50% at the highest energies. Finally, we compare our results with the IceCube limit on the prompt neutrino flux, which is already providing valuable information about some of the QCD models.« less

QCD-Electroweak First-Order Phase Transition in a Supercooled Universe.

PubMed

Iso, Satoshi; Serpico, Pasquale D; Shimada, Kengo

2017-10-06

If the electroweak sector of the standard model is described by classically conformal dynamics, the early Universe evolution can be substantially altered. It is already known that-contrarily to the standard model case-a first-order electroweak phase transition may occur. Here we show that, depending on the model parameters, a dramatically different scenario may happen: A first-order, six massless quark QCD phase transition occurs first, which then triggers the electroweak symmetry breaking. We derive the necessary conditions for this dynamics to occur, using the specific example of the classically conformal B-L model. In particular, relatively light weakly coupled particles are predicted, with implications for collider searches. This scenario is also potentially rich in cosmological consequences, such as renewed possibilities for electroweak baryogenesis, altered dark matter production, and gravitational wave production, as we briefly comment upon.

QCD-Electroweak First-Order Phase Transition in a Supercooled Universe

NASA Astrophysics Data System (ADS)

Iso, Satoshi; Serpico, Pasquale D.; Shimada, Kengo

2017-10-01

If the electroweak sector of the standard model is described by classically conformal dynamics, the early Universe evolution can be substantially altered. It is already known that—contrarily to the standard model case—a first-order electroweak phase transition may occur. Here we show that, depending on the model parameters, a dramatically different scenario may happen: A first-order, six massless quark QCD phase transition occurs first, which then triggers the electroweak symmetry breaking. We derive the necessary conditions for this dynamics to occur, using the specific example of the classically conformal B -L model. In particular, relatively light weakly coupled particles are predicted, with implications for collider searches. This scenario is also potentially rich in cosmological consequences, such as renewed possibilities for electroweak baryogenesis, altered dark matter production, and gravitational wave production, as we briefly comment upon.

Updates on the Studies of $${\\varvec{N}}^\\mathbf{*}$$ N * Structure with CLAS and the Prospects with CLAS12

DOE PAGES

Mokeev, V. I.

2016-06-16

Here, the recent results onmore » $$\\gamma_vpN^*$$ electrocouplings from analyses of the data on exclusive meson electroproduction off protons measured with the CLAS detector at Jefferson Lab are presented. The impact of these results on the exploration of the excited nucleon state structure and non-perturbative strong interaction dynamics behind its formation is outlined. The future extension of these studies in the experiments with the CLAS12 detector in the upgraded Hall-B at JLab will provide for the first time $$\\gamma_vpN^*$$ electrocouplings of all prominent resonances at the still unexplored distance scales that correspond to extremely low (0.05~GeV$^2 < Q^2 <$ 0.5~GeV$^2$) and the highest photon virtualities (5.0~GeV$^2 < Q^2 <$ 12.0~GeV$^2$) ever achieved in the exclusive electroproduction measurements. The expected results will address the most important open problems of the Standard Model: on the nature of more than 98\\% of hadron mass, quark-gluon confinement and emergence of the excited nucleon state structure from the QCD Lagrangian, as well as allowing a search for the new states of hadron matter predicted from the first principles of QCD, the so-called hybrid baryons.« less

Updates on the Studies of {\\varvec{N}}^* Structure with CLAS and the Prospects with CLAS12

NASA Astrophysics Data System (ADS)

Mokeev, V. I.

2016-10-01

The recent results on γ _vpN^* electrocouplings from analyses of the data on exclusive meson electroproduction off protons measured with the CLAS detector at Jefferson Lab are presented. The impact of these results on the exploration of the excited nucleon state structure and non-perturbative strong interaction dynamics behind its formation is outlined. The future extension of these studies in the experiments with the CLAS12 detector in the upgraded Hall-B at JLab will provide for the first time γ _vpN^* electrocouplings of all prominent resonances at the still unexplored distance scales that correspond to extremely low (0.05 GeV^2 < Q^2< 0.5 GeV^2) and the highest photon virtualities (5.0 GeV^2 < Q^2< 12.0 GeV^2) ever achieved in the exclusive electroproduction measurements. The expected results will address the most important open problems of the Standard Model: on the nature of more than 98 % of hadron mass, quark-gluon confinement and emergence of the excited nucleon state structure from the QCD Lagrangian, as well as allowing a search for the new states of hadron matter predicted from the first principles of QCD, the so-called hybrid baryons.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Cohen, Saul D.

Here, we present results for the isovector axial, scalar, and tensor charges g u–d A, g u–d S, and g u–d T of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear β-decays, and the flavor-diagonal tensor charges g u T, g d T, and g s T are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations weremore » done using nine ensembles of gauge configurations generated by the MILC Collaboration using the highly improved staggered quarks action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings a ≈ 0.06,0.09, and 0.12 fm and light-quark masses corresponding to the pion masses M π ≈ 135, 225, and 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, lattice volume, and light-quark masses for the connected contributions. Our final estimates, in the ¯MS scheme at 2 GeV, of the isovector charges are g u–d A = 1.195(33)(20), g u–d S = 0.97(12)(6), and g u–d T = 0.987(51)(20). The first error includes statistical and all systematic uncertainties except that due to the extrapolation Ansatz, which is given by the second error estimate. Combining our estimate for gu–dS with the difference of light quarks masses (m d–m u) QCD = 2.67(35) MeV given by the Flavor Lattice Average Group, we obtain (M N – M P) QCD = 2.59(49) MeV. Estimates of the connected part of the flavor-diagonal tensor charges of the proton are g u T = 0.792(42) and g d T = –0.194(14). Combining our new estimates with precision low-energy experiments, we present updated constraints on novel scalar and tensor interactions, ε S,T, at the TeV scale.« less

Convergence of the chiral expansion in two-flavor lattice QCD.

PubMed

Noaki, J; Aoki, S; Chiu, T W; Fukaya, H; Hashimoto, S; Hsieh, T H; Kaneko, T; Matsufuru, H; Onogi, T; Shintani, E; Yamada, N

2008-11-14

We test the convergence property of the chiral perturbation theory using a lattice QCD calculation of pion mass and decay constant with two dynamical quark flavors. The lattice calculation is performed using the overlap fermion formulation, which realizes exact chiral symmetry at finite lattice spacing. By comparing various expansion prescriptions, we find that the chiral expansion is well saturated at the next-to-leading order for pions lighter than approximately 450 MeV. Better convergence behavior is found, in particular, for a resummed expansion parameter xi, with which the lattice data in the pion mass region 290-750 MeV can be fitted well with the next-to-next-to-leading order formulas. We obtain the results in two-flavor QCD for the low energy constants l[over ]_{3} and l[over ]_{4} as well as the pion decay constant, the chiral condensate, and the average up and down quark mass.

Anatomy of the magnetic catalysis by renormalization-group method

NASA Astrophysics Data System (ADS)

Hattori, Koichi; Itakura, Kazunori; Ozaki, Sho

2017-12-01

We first examine the scaling argument for a renormalization-group (RG) analysis applied to a system subject to the dimensional reduction in strong magnetic fields, and discuss the fact that a four-Fermi operator of the low-energy excitations is marginal irrespective of the strength of the coupling constant in underlying theories. We then construct a scale-dependent effective four-Fermi interaction as a result of screened photon exchanges at weak coupling, and establish the RG method appropriately including the screening effect, in which the RG evolution from ultraviolet to infrared scales is separated into two stages by the screening-mass scale. Based on a precise agreement between the dynamical mass gaps obtained from the solutions of the RG and Schwinger-Dyson equations, we discuss an equivalence between these two approaches. Focusing on QED and Nambu-Jona-Lasinio model, we clarify how the properties of the interactions manifest themselves in the mass gap, and point out an importance of respecting the intrinsic energy-scale dependences in underlying theories for the determination of the mass gap. These studies are expected to be useful for a diagnosis of the magnetic catalysis in QCD.

The Symmetries of QCD

ScienceCinema

Chivukula, Sekhar

2017-12-22

The symmetries of a quantum field theory can be realized in a variety of ways. Symmetries can be realized explicitly, approximately, through spontaneous symmetry breaking or, via an anomaly, quantum effects can dynamically eliminate a symmetry of the theory that was present at the classical level.  Quantum Chromodynamics (QCD), the modern theory of the strong interactions, exemplify each of these possibilities. The interplay of these effects determine the spectrum of particles that we observe and, ultimately, account for 99% of the mass of ordinary matter. 

Hidden axion dark matter decaying through mixing with QCD axion and the 3.5 keV X-ray line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higaki, Tetsutaro; Kitajima, Naoya; Takahashi, Fuminobu, E-mail: thigaki@post.kek.jp, E-mail: kitajima@tuhep.phys.tohoku.ac.jp, E-mail: fumi@tuhep.phys.tohoku.ac.jp

2014-12-01

Hidden axions may be coupled to the standard model particles through a kinetic or mass mixing with QCD axion. We study a scenario in which a hidden axion constitutes a part of or the whole of dark matter and decays into photons through the mixing, explaining the 3.5 keV X-ray line signal. Interestingly, the required long lifetime of the hidden axion dark matter can be realized for the QCD axion decay constant at an intermediate scale, if the mixing is sufficiently small. In such a two component dark matter scenario, the primordial density perturbations of the hidden axion can bemore » highly non-Gaussian, leading to a possible dispersion in the X-ray line strength from various galaxy clusters and near-by galaxies. We also discuss how the parallel and orthogonal alignment of two axions affects their couplings to gauge fields. In particular, the QCD axion decay constant can be much larger than the actual Peccei-Quinn symmetry breaking.« less

Broken chiral symmetry on a null plane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beane, Silas R., E-mail: silas@physics.unh.edu

2013-10-15

On a null-plane (light-front), all effects of spontaneous chiral symmetry breaking are contained in the three Hamiltonians (dynamical Poincaré generators), while the vacuum state is a chiral invariant. This property is used to give a general proof of Goldstone’s theorem on a null-plane. Focusing on null-plane QCD with N degenerate flavors of light quarks, the chiral-symmetry breaking Hamiltonians are obtained, and the role of vacuum condensates is clarified. In particular, the null-plane Gell-Mann–Oakes–Renner formula is derived, and a general prescription is given for mapping all chiral-symmetry breaking QCD condensates to chiral-symmetry conserving null-plane QCD condensates. The utility of the null-planemore » description lies in the operator algebra that mixes the null-plane Hamiltonians and the chiral symmetry charges. It is demonstrated that in a certain non-trivial limit, the null-plane operator algebra reduces to the symmetry group SU(2N) of the constituent quark model. -- Highlights: •A proof (the first) of Goldstone’s theorem on a null-plane is given. •The puzzle of chiral-symmetry breaking condensates on a null-plane is solved. •The emergence of spin-flavor symmetries in null-plane QCD is demonstrated.« less

Nucleon resonance structure in the finite volume of lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jia -Jun; Kamano, H.; Lee, T. -S. H.

An approach for relating the nucleon resonances extracted from πN reaction data to lattice QCD calculations has been developed by using the finite-volume Hamiltonian method. Within models of πN reactions, bare states are introduced to parametrize the intrinsic excitations of the nucleon. We show that the resonance can be related to the probability P N*(E) of finding the bare state, N*, in the πN scattering states in infinite volume. We further demonstrate that the probability P V N*(E) of finding the same bare states in the eigenfunctions of the underlying Hamiltonian in finite volume approaches P N*(E) as the volumemore » increases. Our findings suggest that the comparison of P N*(E) and P V N*(E) can be used to examine whether the nucleon resonances extracted from the πN reaction data within the dynamical models are consistent with lattice QCD calculation. We also discuss the measurement of P V N*(E) directly from lattice QCD. Furthermore, the practical differences between our approach and the approach using the Lüscher formalism to relate LQCD calculations to the nucleon resonance poles embedded in the data are also discussed.« less

Nucleon resonance structure in the finite volume of lattice QCD

DOE PAGES

Wu, Jia -Jun; Kamano, H.; Lee, T. -S. H.; ...

2017-06-19

An approach for relating the nucleon resonances extracted from πN reaction data to lattice QCD calculations has been developed by using the finite-volume Hamiltonian method. Within models of πN reactions, bare states are introduced to parametrize the intrinsic excitations of the nucleon. We show that the resonance can be related to the probability P N*(E) of finding the bare state, N*, in the πN scattering states in infinite volume. We further demonstrate that the probability P V N*(E) of finding the same bare states in the eigenfunctions of the underlying Hamiltonian in finite volume approaches P N*(E) as the volumemore » increases. Our findings suggest that the comparison of P N*(E) and P V N*(E) can be used to examine whether the nucleon resonances extracted from the πN reaction data within the dynamical models are consistent with lattice QCD calculation. We also discuss the measurement of P V N*(E) directly from lattice QCD. Furthermore, the practical differences between our approach and the approach using the Lüscher formalism to relate LQCD calculations to the nucleon resonance poles embedded in the data are also discussed.« less

The Emergence of Hadrons from QCD Color

NASA Astrophysics Data System (ADS)

Brooks, William; Color Dynamics in Cold Matter (CDCM) Collaboration

2015-10-01

The formation of hadrons from energetic quarks, the dynamical enforcement of QCD confinement, is not well understood at a fundamental level. In Deep Inelastic Scattering, modifications of the distributions of identified hadrons emerging from nuclei of different sizes reveal a rich variety of spatial and temporal characteristics of the hadronization process, including its dependence on spin, flavor, energy, and hadron mass and structure. The EIC will feature a wide range of kinematics, allowing a complete investigation of medium-induced gluon bremsstrahlung by the propagating quarks, leading to partonic energy loss. This fundamental process, which is also at the heart of jet quenching in heavy ion collisions, can be studied for light and heavy quarks at the EIC through observables quantifying hadron ``attenuation'' for a variety of hadron species. Transverse momentum broadening of hadrons, which is sensitive to the nuclear gluonic field, will also be accessible, and can be used to test our understanding from pQCD of how this quantity evolves with pathlength, as well as its connection to partonic energy loss. The evolution of the forming hadrons in the medium will shed new light on the dynamical origins of the forces between hadrons, and thus ultimately on the nuclear force. Supported by the Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) of Chile.

Nonperturbative quark, gluon, and meson correlators of unquenched QCD

NASA Astrophysics Data System (ADS)

Cyrol, Anton K.; Mitter, Mario; Pawlowski, Jan M.; Strodthoff, Nils

2018-03-01

We present nonperturbative first-principle results for quark, gluon, and meson 1PI correlation functions of two-flavor Landau-gauge QCD in the vacuum. These correlation functions carry the full information about the theory. They are obtained by solving their functional renormalization group equations in a systematic vertex expansion, aiming at apparent convergence. This work represents a crucial prerequisite for quantitative first-principle studies of the QCD phase diagram and the hadron spectrum within this framework. In particular, we have computed the gluon, ghost, quark, and scalar-pseudoscalar meson propagators, as well as gluon, ghost-gluon, quark-gluon, quark, quark-meson, and meson interactions. Our results stress the crucial importance of the quantitatively correct running of different vertices in the semiperturbative regime for describing the phenomena and scales of confinement and spontaneous chiral symmetry breaking without phenomenological input.

Top quark mass determination from the energy peaks of b-jets and B-hadrons at NLO QCD

DOE PAGES

Agashe, Kaustubh; Franceschini, Roberto; Kim, Doojin; ...

2016-11-21

Here, we analyze the energy spectra of single b-jets and B-hadrons resulting from the production and decay of top quarks within the SM at the LHC at the NLO QCD. For both hadrons and jets, we calculate the correlation of the peak of the spectrum with the top quark mass, considering the “energy peak” as an observable to determine the top quarkmass. Such a method is motivated by our previous work where we argued that this approach can have reduced sensitivity to the details of the production mechanism of the top quark, whether it concerns higher-order QCD effects or newmore » physics contributions. For a 1% jet energy scale uncertainty, the top quark mass can then be extracted using the energy peak of b-jets with an error ±(1.2(exp) + 0.6(th)) GeV. In view of the dominant jet energy scale uncertainty in the measurement using b-jets, we also investigate the extraction of the top quark mass from the energy peak of the corresponding B-hadrons which, in principle, can be measured without this uncertainty. The calculation of the B-hadron energy spectrum is carried out using fragmentation functions at NLO. The dependence on the fragmentation scale turns out to be the largest theoretical uncertainty in this extraction of top quark mass.« less

Top quark mass determination from the energy peaks of b-jets and B-hadrons at NLO QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agashe, Kaustubh; Franceschini, Roberto; Kim, Doojin

Here, we analyze the energy spectra of single b-jets and B-hadrons resulting from the production and decay of top quarks within the SM at the LHC at the NLO QCD. For both hadrons and jets, we calculate the correlation of the peak of the spectrum with the top quark mass, considering the “energy peak” as an observable to determine the top quarkmass. Such a method is motivated by our previous work where we argued that this approach can have reduced sensitivity to the details of the production mechanism of the top quark, whether it concerns higher-order QCD effects or newmore » physics contributions. For a 1% jet energy scale uncertainty, the top quark mass can then be extracted using the energy peak of b-jets with an error ±(1.2(exp) + 0.6(th)) GeV. In view of the dominant jet energy scale uncertainty in the measurement using b-jets, we also investigate the extraction of the top quark mass from the energy peak of the corresponding B-hadrons which, in principle, can be measured without this uncertainty. The calculation of the B-hadron energy spectrum is carried out using fragmentation functions at NLO. The dependence on the fragmentation scale turns out to be the largest theoretical uncertainty in this extraction of top quark mass.« less

Precise QCD Predictions for the Production of a Z Boson in Association with a Hadronic Jet.

PubMed

Gehrmann-De Ridder, A; Gehrmann, T; Glover, E W N; Huss, A; Morgan, T A

2016-07-08

We compute the cross section and differential distributions for the production of a Z boson in association with a hadronic jet to next-to-next-to-leading order (NNLO) in perturbative QCD, including the leptonic decay of the Z boson. We present numerical results for the transverse momentum and rapidity distributions of both the Z boson and the associated jet at the LHC. We find that the NNLO corrections increase the NLO predictions by approximately 1% and significantly reduce the scale variation uncertainty.

QCD Axion Dark Matter with a Small Decay Constant.

PubMed

Co, Raymond T; Hall, Lawrence J; Harigaya, Keisuke

2018-05-25

The QCD axion is a good dark matter candidate. The observed dark matter abundance can arise from misalignment or defect mechanisms, which generically require an axion decay constant f_{a}∼O(10^{11})  GeV (or higher). We introduce a new cosmological origin for axion dark matter, parametric resonance from oscillations of the Peccei-Quinn symmetry breaking field, that requires f_{a}∼(10^{8}-10^{11})  GeV. The axions may be warm enough to give deviations from cold dark matter in large scale structure.

Centrality, rapidity, and transverse momentum dependence of isolated prompt photon production in lead-lead collisions at s N N = 2.76 TeV measured with the ATLAS detector

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2016-03-28

In this study, prompt photon production in √s NN = 2.76-TeV Pb+Pb collisions has been measured by the ATLAS experiment at the Large Hadron Collider using data collected in 2011 with an integrated luminosity of 0.14 nb -1. Inclusive photon yields, scaled by the mean nuclear thickness function, are presented as a function of collision centrality and transverse momentum in two pseudorapidity intervals, |η| < 1.37 and 1.52 ≤ |η| < 2.37. The scaled yields in the two pseudorapidity intervals, as well as the ratios of the forward yields to those at midrapidity, are compared to the expectations from next-to-leading-ordermore » perturbative QCD (pQCD) calculations. The measured cross sections agree well with the predictions for proton-proton collisions within statistical and systematic uncertainties. Both the yields and the ratios are also compared to two other pQCD calculations, one which uses the isospin content appropriate to colliding lead nuclei and another which includes nuclear modifications to the nucleon parton distribution functions.« less

A precise determination of the top-quark pole mass

NASA Astrophysics Data System (ADS)

Wang, Sheng-Quan; Wu, Xing-Gang; Si, Zong-Guo; Brodsky, Stanley J.

2018-03-01

The Principle of Maximum Conformality (PMC) provides a systematic way to eliminate the renormalization scheme and renormalization scale uncertainties for high-energy processes. We have observed that by applying PMC scale setting, one obtains comprehensive and self-consistent pQCD predictions for the top-quark pair total cross section and the top-quark pair forward-backward asymmetry in agreement with the measurements at the Tevatron and LHC. As a step forward, in the present paper, we determine the top-quark pole mass via a detailed comparison of the top-quark pair cross section with the measurements at the Tevatron and LHC. The results for the top-quark pole mass are m_t=174.6^{+3.1}_{-3.2} GeV for the Tevatron with √{S}=1.96 TeV, m_t=173.7± 1.5 and 174.2± 1.7 GeV for the LHC with √{S} = 7 and 8 TeV, respectively. Those predictions agree with the average, 173.34± 0.76 GeV, obtained from various collaborations via direct measurements. The consistency of the pQCD predictions using the PMC with all of the collider measurements at different energies provides an important verification of QCD.

Vector-Boson Fusion Higgs Production at Three Loops in QCD.

PubMed

Dreyer, Frédéric A; Karlberg, Alexander

2016-08-12

We calculate the next-to-next-to-next-to-leading-order (N^{3}LO) QCD corrections to inclusive vector-boson fusion Higgs production at proton colliders, in the limit in which there is no color exchange between the hadronic systems associated with the two colliding protons. We also provide differential cross sections for the Higgs transverse momentum and rapidity distributions. We find that the corrections are at the 1‰-2‰ level, well within the scale uncertainty of the next-to-next-to-leading-order calculation. The associated scale uncertainty of the N^{3}LO calculation is typically found to be below the 2‰ level. We also consider theoretical uncertainties due to missing higher order parton distribution functions, and provide an estimate of their importance.

Current-Current Interactions, Dynamical Symmetry - and Quantum Chromodynamics.

NASA Astrophysics Data System (ADS)

Neuenschwander, Dwight Edward, Jr.

Quantum Chromodynamics with massive gluons (gluon mass (TBOND) xm(,p)) in a contact-interaction limit called CQCD (strong coupling g (--->) (INFIN); x (--->) (INFIN)), despite its non-renormalizability and lack of hope of confinement, is nevertheless interesting for at least two reasons. (1) Some authors have suggested a relation between 4-Fermi and Yang-Mills theories. If g/x('2) << 1, then CQCD is not merely a 4-Fermi interaction, but includes 4, 6, 8, ...-Fermi non-Abelian contact interactions. (2) With the possibility of infrared slavery, perturbative evaluation of QCD in the infrared is a dubious practice. However, if g('2)/x('2) << 1 in CQCD, then the simplest 4-Fermi interaction is dominant, and CQCD admits perturbative treatment, but only in the infrared. With the dominant interaction, a dynamical Nambu-Goldstone realization of chiral symmetry -breaking (XSB) is found. Although in QCD the relation between confinement and XSB is controversial, XSB occurs in CQCD provided confinement is sacrificed.

Effective chiral restoration in the ρ' meson in lattice QCD

NASA Astrophysics Data System (ADS)

Glozman, L. Ya.; Lang, C. B.; Limmer, Markus

2010-11-01

In simulations with dynamical quarks it has been established that the ground state ρ in the infrared is a strong mixture of the two chiral representations (0,1)+(1,0) and (1/2,1/2)b. Its angular momentum content is approximately the S13 partial wave. Effective chiral restoration in an excited ρ-meson would require that in the infrared this meson couples predominantly to one of the two representations. The variational method allows one to study the mixing of interpolators with different chiral transformation properties in the nonperturbatively determined excited state at different resolution scales. We present results for the first excited state of the ρ-meson using simulations with nf=2 dynamical quarks. We point out, that in the infrared a leading contribution to ρ'=ρ(1450) comes from (1/2,1/2)b, in contrast to the ρ. The ρ' wave function contains a significant contribution of the D13 wave which is not consistent with the quark model prediction.

Holographic entropy and real-time dynamics of quarkonium dissociation in non-Abelian plasma

DOE PAGES

Iatrakis, Ioannis; Kharzeev, Dmitri E.

2016-04-26

The peak of the heavy quark pair entropy at the deconfinement transition, observed in lattice QCD, suggests that the transition is effectively driven by the increase of the entropy of bound states. The growth of the entropy with the interquark distance leads to the emergent entropic force that induces dissociation of quarkonium states. Since the quark-gluon plasma around the transition point is a strongly coupled system, we use the gauge-gravity duality to study the entropy of heavy quarkonium and the real-time dynamics of its dissociation. In particular, we employ the improved holographic QCD model as a dual description of largemore » N c Yang-Mills theory. Studying the dynamics of the fundamental string between the quarks placed on the boundary, we find that the entropy peaks at the transition point. We also study the real-time dynamics of the system by considering the holographic string falling in the black hole horizon where it equilibrates. As a result, in the vicinity of the deconfinement transition, the dissociation time is found to be less than a fermi, suggesting that the entropic destruction is the dominant dissociation mechanism in this temperature region.« less

Spin dynamics of qqq wave function on light front in high momentum limit of QCD: Role of qqq force

NASA Astrophysics Data System (ADS)

Mitra, A. N.

2008-04-01

The contribution of a spin-rich qqq force (in conjunction with pairwise qq forces) to the analytical structure of the qqq wave function is worked out in the high momentum regime of QCD where the confining interaction may be ignored, so that the dominant effect is Coulombic. A distinctive feature of this study is that the spin-rich qqq force is generated by a ggg vertex (a genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on as many quark lines, giving rise to a (Mercedes-Benz type) Y-shaped diagram. The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these ingredients, the differential equation for the 3D wave function ϕ receives well-defined contributions from the qq and qqq forces. In particular a negative eigenvalue of the spin operator iσ1 · σ2 × σ3 which is an integral part of the qqq force, causes a characteristic singularity in the differential equation, signalling the dynamical effect of a spin-rich qqq force not yet considered in the literature. The potentially crucial role of this interesting effect vis-a-vis the so-called 'spin anomaly' of the proton, is a subject of considerable physical interest.

Scalar pseudo-Nambu-Goldstone boson in nuclei and dense nuclear matter

NASA Astrophysics Data System (ADS)

Lee, Hyun Kyu; Paeng, Won-Gi; Rho, Mannque

2015-12-01

The notion that the scalar listed as f0(500 ) in the particle data booklet is a pseudo-Nambu-Goldstone (NG) boson of spontaneously broken scale symmetry, explicitly broken by a small departure from an infrared fixed point, is explored in nuclear dynamics. This notion—which puts the scalar (which we shall identify as the "dilaton") on the same footing as the pseudoscalar pseudo-NG bosons, i.e., octet π , while providing a simple explanation for the Δ I =1 /2 rule for kaon decay—generalizes the standard chiral perturbation theory (χ PT ) to "scale chiral perturbation theory," denoted χPT σ , with one infrared mass scale for both symmetries, with the σ figuring as a chiral singlet NG mode in the nonstrange sector. Applied to nuclear dynamics, it is seen to provide answers to various hitherto unclarified nuclear phenomena, such as the success of one-boson-exchange potentials, the large cancellation of a strongly attractive scalar potential by a strongly repulsive vector potential in relativistic mean-field theory of nuclear systems and in-medium QCD sum rules, the interplay of the dilaton and the vector meson ω in dense Skyrmion matter, the Bogomol'nyi-Prasad-Sommerfeld Skyrmion structure of nuclei accounting for small binding energies of medium-heavy nuclei, and the suppression of hyperon degrees of freedom in compact-star matter.

Cumulants vs correlation functions and the QCD phase diagram at low energies

DOE PAGES

Bzdak, A.; Koch, V.; Skokov, V.; ...

2017-09-25

We discuss the relation between particle number cumulants and genuine correlation functions. Here, it is argued that measuring multi-particle correlation functions could provide cleaner information on possible non-trivial dynamics in heavy-ion collisions.

Cumulants vs correlation functions and the QCD phase diagram at low energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bzdak, A.; Koch, V.; Skokov, V.

We discuss the relation between particle number cumulants and genuine correlation functions. Here, it is argued that measuring multi-particle correlation functions could provide cleaner information on possible non-trivial dynamics in heavy-ion collisions.

Nonperturbative Contributions to a Resummed Leptonic Angular Distribution in Inclusive Z/γ* Boson Production

NASA Astrophysics Data System (ADS)

Guzzi, Marco; Nadolsky, Pavel M.

We summarize a new analysis of the distribution φ η * of charged leptons produced in decays of Z and γ* bosons in the Collins-Soper-Sterman (CSS) formalism for transverse momentum resummation. By comparing the φ η * distribution measured at the Tevatron with the resummed CSS cross section with approximate {O}(α s2) Wilson coefficients, we constrain the magnitude of the nonperturbative Gaussian smearing factor and analyze its uncertainty caused by variations in scale parameters. We find excellent agreement between the φ η * data and our theoretical prediction, provided by the RESBOS resummation program. The nonperturbative factor that we obtained can be used to update resummed QCD predictions for precision measurements in inclusive W and Z production and for comparisons to various models of nonperturbative dynamics.

Next-to-leading-order QCD corrections to Higgs boson production in association with a top quark pair and a jet.

PubMed

van Deurzen, H; Luisoni, G; Mastrolia, P; Mirabella, E; Ossola, G; Peraro, T

2013-10-25

We present the calculation of the cross section for Higgs boson production in association with a top quark pair plus one jet, at next-to-leading-order accuracy in QCD. All mass dependence is retained without recurring to any approximation. After including the complete next-to-leading-order QCD corrections, we observe a strong reduction in the scale dependence of the result. We also show distributions for the invariant mass of the top quark pair, with and without the additional jet, and for the transverse momentum and the pseudorapidity of the Higgs boson. Results for the virtual contributions are obtained with a novel reduction approach based on integrand decomposition via the Laurent expansion, as implemented in the library, NINJA. Cross sections and differential distributions are obtained with an automated setup which combines the GOSAM and SHERPA frameworks.

Duality between QCD perturbative series and power corrections

NASA Astrophysics Data System (ADS)

Narison, S.; Zakharov, V. I.

2009-08-01

We elaborate on the relation between perturbative and power-like corrections to short-distance sensitive QCD observables. We confront theoretical expectations with explicit perturbative calculations existing in literature. As is expected, the quadratic correction is dual to a long perturbative series and one should use one of them but not both. However, this might be true only for very long perturbative series, with number of terms needed in most cases exceeding the number of terms available. What has not been foreseen, the quartic corrections might also be dual to the perturbative series. If confirmed, this would imply a crucial modification of the dogma. We confront this quadratic correction against existing phenomenology (QCD (spectral) sum rules scales, determinations of light quark masses and of αs from τ-decay). We find no contradiction and (to some extent) better agreement with the data and with recent lattice calculations.

Anderson localization in sigma models

NASA Astrophysics Data System (ADS)

Bruckmann, Falk; Wellnhofer, Jacob

2018-03-01

In QCD above the chiral restoration temperature there exists an Anderson transition in the fermion spectrum from localized to delocalized modes. We investigate whether the same holds for nonlinear sigma models which share properties like dynamical mass generation and asymptotic freedom with QCD. In particular we study the spectra of fermions coupled to (quenched) CP(N-1) configurations at high temperatures. We compare results in two and three space-time dimensions: in two dimensions the Anderson transition is absent, since all fermion modes are localized, while in three dimensions it is present. Our measurements include a more recent observable characterizing level spacings: the distribution of ratios of consecutive level spacings.

Degeneracy of vector-channel spatial correlators in high temperature QCD

NASA Astrophysics Data System (ADS)

Rohrhofer, Christian; Aoki, Yasumichi; Cossu, Guido; Fukaya, Hidenori; Glozman, Leonid; Hashimoto, Shoji; Lang, Christian B.; Prelovsek, Sasa

2018-03-01

We study spatial isovector meson correlators in Nf = 2 QCD with dynamical domain-wall fermions on 323 × 8 lattices at temperatures up to 380 MeV with various quark masses. We measure the correlators of spin-one isovector operators including vector, axial-vector, tensor and axial-tensor. At temperatures above Tc we observe an approximate degeneracy of the correlators in these channels, which is unexpected because some of them are not related under SU(2)L×SU(2)R nor U(1)A symmetries. The observed approximate degeneracy suggests emergent SU(2)CS (chiral-spin) and SU(4) symmetries at high T.

Diphotons, new vacuum angles, and strong CP

DOE PAGES

Draper, Patrick; McKeen, David

2016-04-20

The Standard Model contains a well-understood, natural, spin-0 diphoton resonance: the π 0. Numerous studies have pointed out that the hint of a new diphoton resonance at 750 GeV could be a pion analog, identified with the pseudo-Nambu-Goldstone boson of a chiral symmetry spontaneously broken by new strong dynamics at the TeV scale. These “hypercolor” models are generically expected to violate parity through a topological angle θ ~. We discuss the physics of θ ~ and its impact on the phenomenology of the new sector. We also describe some of the theoretical implications of a nonzero θ ~. In particular,more » θ ~ can generate an O(1) threshold correction to the QCD vacuum angle θ near the TeV scale, sharply constraining ultraviolet solutions to the strong CP problem. Furthermore, finding that θ ~ is small may be interpreted as evidence in favor of UV solutions to strong CP, particularly those based on spontaneously broken P or CP symmetries.« less

Diphotons, new vacuum angles, and strong CP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Draper, Patrick; McKeen, David

The Standard Model contains a well-understood, natural, spin-0 diphoton resonance: the π 0. Numerous studies have pointed out that the hint of a new diphoton resonance at 750 GeV could be a pion analog, identified with the pseudo-Nambu-Goldstone boson of a chiral symmetry spontaneously broken by new strong dynamics at the TeV scale. These “hypercolor” models are generically expected to violate parity through a topological angle θ ~. We discuss the physics of θ ~ and its impact on the phenomenology of the new sector. We also describe some of the theoretical implications of a nonzero θ ~. In particular,more » θ ~ can generate an O(1) threshold correction to the QCD vacuum angle θ near the TeV scale, sharply constraining ultraviolet solutions to the strong CP problem. Furthermore, finding that θ ~ is small may be interpreted as evidence in favor of UV solutions to strong CP, particularly those based on spontaneously broken P or CP symmetries.« less

Global QCD Analysis of the Nucleon Tensor Charge with Lattice QCD Constraints

NASA Astrophysics Data System (ADS)

Shows, Harvey, III; Melnitchouk, Wally; Sato, Nobuo

2017-09-01

By studying the parton distribution functions (PDFs) of a nucleon, we probe the partonic scale of nature, exploring what it means to be a nucleon. In this study, we are interested in the transversity PDF-the least studied of the three collinear PDFs. By conducting a global analysis on experimental data from semi-inclusive deep inelastic scattering (SIDIS), as well as single-inclusive e+e- annihilation (SIA), we extract the fit parameters needed to describe the transverse moment dependent (TMD) transversity PDF, as well as the Collins fragmentation function. Once the collinear transversity PDF is obtained by integrating the extracted TMD PDF, we wish to resolve discrepancies between lattice QCD calculations and phenomenological extractions of the tensor charge from data. Here we show our results for the transversity distribution and tensor charge. Using our method of iterative Monte Carlo, we now have a more robust understanding of the transversity PDF. With these results we are able to progress in our understanding of TMD PDFs, as well as testify to the efficacy of current lattice QCD calculations. This work is made possible through support from NSF award 1659177 to Old Dominion University.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darling, Christopher Lynn

By determining the production cross sections for heavy flavor hadrons, we test the theoretical predictions from perturhative quantum chroma-dynamics (QCD). In the case of pion induced beauty production, the few published results do not resolve the issue of the applicability of perturbative QCD. This analysis is undertaken in order to help resolve this situation. We determine the total beauty and charm production cross sections using an analysis of single electron decay products. We extract the cross sections per nucleon from the two-dimensional distribution of electron p versus impact parameter ( d) to the primary vertex. We place an upper limit on the beauty production cross section of σ bmore » $$\\bar{b}$$ < 105 nb at the 90% confidence level, where the limit includes both statistical and systematic errors. The charm production cross section is determined to be σ cc = 13.9$$+2.4/atop{-2.3}$$ (stat) ± 1.8 (syst) μ.b, which is in good agreement with next-to-leading order QCD predictions and other measurements.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darling, Christopher Lynn

By determining the production cross sections for heavy flavor hadrons, we test the theoretical predictions from perturhative quantum chroma-dynamics (QCD). In the case of pion induced beauty production, the few published results do not resolve the issue of the applicability of perturbative QCD. This analysis is undertaken in order to help resolve this situation. We determine the total beauty and charm production cross sections using an analysis of single electron decay products. We extract the cross sections per nucleon from the two-dimensional distribution of electronmore » $$p^2_{\\tau}$$ versus impact parameter (d) to the primary vertex. We place an upper limit on the beauty production cross section of $$\\sigma_{b\\overline{b}}$$ < 105 nb at the 90% confidence level, where the limit includes both statistical and systematic errors. The charm production cross section is determined to be $$\\sigma_{c\\overline{c}} = 13.9 ^{+2.4}_{-2.3}$$(stat)±l.8(syst) $$\\mu b$$, which is in good agreement with next-to-leading order QCD predictions and other measurements.« less

SO(3) "Nuclear Physics" with ultracold Gases

NASA Astrophysics Data System (ADS)

Rico, E.; Dalmonte, M.; Zoller, P.; Banerjee, D.; Bögli, M.; Stebler, P.; Wiese, U.-J.

2018-06-01

An ab initio calculation of nuclear physics from Quantum Chromodynamics (QCD), the fundamental SU(3) gauge theory of the strong interaction, remains an outstanding challenge. Here, we discuss the emergence of key elements of nuclear physics using an SO(3) lattice gauge theory as a toy model for QCD. We show that this model is accessible to state-of-the-art quantum simulation experiments with ultracold atoms in an optical lattice. First, we demonstrate that our model shares characteristic many-body features with QCD, such as the spontaneous breakdown of chiral symmetry, its restoration at finite baryon density, as well as the existence of few-body bound states. Then we show that in the one-dimensional case, the dynamics in the gauge invariant sector can be encoded as a spin S = 3/2 Heisenberg model, i.e., as quantum magnetism, which has a natural realization with bosonic mixtures in optical lattices, and thus sheds light on the connection between non-Abelian gauge theories and quantum magnetism.

Condensates in quantum chromodynamics and the cosmological constant

PubMed Central

Brodsky, Stanley J.; Shrock, Robert

2011-01-01

Casher and Susskind [Casher A, Susskind L (1974) Phys Rev 9:436–460] have noted that in the light-front description, spontaneous chiral symmetry breaking is a property of hadronic wavefunctions and not of the vacuum. Here we show from several physical perspectives that, because of color confinement, quark and gluon condensates in quantum chromodynamics (QCD) are associated with the internal dynamics of hadrons. We discuss condensates using condensed matter analogues, the Anti de Sitter/conformal field theory correspondence, and the Bethe–Salpeter–Dyson–Schwinger approach for bound states. Our analysis is in agreement with the Casher and Susskind model and the explicit demonstration of “in-hadron” condensates by Roberts and coworkers [Maris P, Roberts CD, Tandy PC (1998) Phys Lett B 420:267–273], using the Bethe–Salpeter–Dyson–Schwinger formalism for QCD-bound states. These results imply that QCD condensates give zero contribution to the cosmological constant, because all of the gravitational effects of the in-hadron condensates are already included in the normal contribution from hadron masses.

Hadron electric polarizability from lattice QCD

NASA Astrophysics Data System (ADS)

Alexandru, Andrei; Lujan, Michael; Freeman, Walter; Lee, Frank

2015-04-01

Electric polarizability measures the ability of the electric field to deform a particle. Experimentally, electric and magnetic polarizabilities can be measured in Compton scattering experiments. To compute these quantities theoretically we need to understand the internal structure of the scatterer and the dynamics of its constituents. For hadrons - bound stated of quarks and gluons - this is a very difficult problem. Lattice QCD can be used to compute the polarizabilities directly in terms of quark and gluons degrees of freedom. In this talk we focus on the neutron. We present results for the electric polarizability for two different quark masses, light enough to connect to chiral perturbation theory. These are currently the lightest quark masses used in lattice QCD polarizability studies. For each pion mass we compute the polarizability at four different volumes and perform an infinite volume extrapolation. For one ensemble, we also discuss the effect of turning on the coupling between the background field and the sea quarks. We compare our results to chiral perturbation theory expectations.

Strong coupling constant from Adler function in lattice QCD

NASA Astrophysics Data System (ADS)

Hudspith, Renwick J.; Lewis, Randy; Maltman, Kim; Shintani, Eigo

2016-09-01

We compute the QCD coupling constant, αs, from the Adler function with vector hadronic vacuum polarization (HVP) function. On the lattice, Adler function can be measured by the differential of HVP at two different momentum scales. HVP is measured from the conserved-local vector current correlator using nf = 2 + 1 flavor Domain Wall lattice data with three different lattice cutoffs, up to a-1 ≈ 3.14 GeV. To avoid the lattice artifact due to O(4) symmetry breaking, we set the cylinder cut on the lattice momentum with reflection projection onto vector current correlator, and it then provides smooth function of momentum scale for extracted HVP. We present a global fit of the lattice data at a justified momentum scale with three lattice cutoffs using continuum perturbation theory at 𝒪(αs4) to obtain the coupling in the continuum limit at arbitrary scale. We take the running to Z boson mass through the appropriate thresholds, and obtain αs(5)(MZ) = 0.1191(24)(37) where the first is statistical error and the second is systematic one.

The order of the quantum chromodynamics transition predicted by the standard model of particle physics.

PubMed

Aoki, Y; Endrodi, G; Fodor, Z; Katz, S D; Szabó, K K

2006-10-12

Quantum chromodynamics (QCD) is the theory of the strong interaction, explaining (for example) the binding of three almost massless quarks into a much heavier proton or neutron--and thus most of the mass of the visible Universe. The standard model of particle physics predicts a QCD-related transition that is relevant for the evolution of the early Universe. At low temperatures, the dominant degrees of freedom are colourless bound states of hadrons (such as protons and pions). However, QCD is asymptotically free, meaning that at high energies or temperatures the interaction gets weaker and weaker, causing hadrons to break up. This behaviour underlies the predicted cosmological transition between the low-temperature hadronic phase and a high-temperature quark-gluon plasma phase (for simplicity, we use the word 'phase' to characterize regions with different dominant degrees of freedom). Despite enormous theoretical effort, the nature of this finite-temperature QCD transition (that is, first-order, second-order or analytic crossover) remains ambiguous. Here we determine the nature of the QCD transition using computationally demanding lattice calculations for physical quark masses. Susceptibilities are extrapolated to vanishing lattice spacing for three physical volumes, the smallest and largest of which differ by a factor of five. This ensures that a true transition should result in a dramatic increase of the susceptibilities. No such behaviour is observed: our finite-size scaling analysis shows that the finite-temperature QCD transition in the hot early Universe was not a real phase transition, but an analytic crossover (involving a rapid change, as opposed to a jump, as the temperature varied). As such, it will be difficult to find experimental evidence of this transition from astronomical observations.

AdS/QCD and Light Front Holography: A New Approximation to QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; de Teramond, Guy

2010-02-15

The combination of Anti-de Sitter space (AdS) methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound states. Starting from the bound-state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give themore » hadronic spectrum, and its eigenmodes represent the probability distribution of the hadronic constituents at a given scale. Applications to the light meson and baryon spectra are presented. The predicted meson spectrum has a string-theory Regge form M{sup 2} = 4{kappa}{sup 2}(n+L+S/2); i.e., the square of the eigenmass is linear in both L and n, where n counts the number of nodes of the wavefunction in the radial variable {zeta}. The space-like pion form factor is also well reproduced. One thus obtains a remarkable connection between the description of hadronic modes in AdS space and the Hamiltonian formulation of QCD in physical space-time quantized on the light-front at fixed light-front time {tau}. The model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms.« less

The CP-PACS parallel computer

NASA Astrophysics Data System (ADS)

Ukawa, Akira

1998-05-01

The CP-PACS computer is a massively parallel computer consisting of 2048 processing units and having a peak speed of 614 GFLOPS and 128 GByte of main memory. It was developed over the four years from 1992 to 1996 at the Center for Computational Physics, University of Tsukuba, for large-scale numerical simulations in computational physics, especially those of lattice QCD. The CP-PACS computer has been in full operation for physics computations since October 1996. In this article we describe the chronology of the development, the hardware and software characteristics of the computer, and its performance for lattice QCD simulations.

Effective Theories for QCD-like at TeV Scale

NASA Astrophysics Data System (ADS)

Lu, Jie; Bijnens, Johan

2016-04-01

We study the Effective Field Theory of three QCD-like theories, which can be classified by having quarks in a complex, real or pseudo-real representations of the gauge group. The Lagrangians are written in a very similar way so that the calculations can be done using techniques from Chiral Perturbation Theory (ChPT). We calculated the vacuum-expectation-value, the mass and the decay constant of pseudo-Goldstone Bosons up to next-to-next-to leading order (NNLO) [J. Bijnens and J. Lu, JHEP 0911 (2009) 116 [arxiv:arXiv:0910.5424 [hep-ph

Search for quark contact interactions and extra spatial dimensions using dijet angular distributions in proton–proton collisions at $$\\sqrt s =$$ 8 TeV

DOE PAGES

Khachatryan, Vardan

2015-04-24

Our search is presented for quark contact interactions and extra spatial dimensions in proton–proton collisions at √s=8TeVusing dijet angular distributions. The search is based on a data set corresponding to an integrated luminosity of 19.7fb -1collected by the CMS detector at the CERN LHC. Dijet angular distributions are found to be in agreement with the perturbative QCD predictions that include electroweak corrections. Limits on the contact interaction scale from a variety of models at next-to-leading order in QCD corrections are obtained. A benchmark model in which only left-handed quarks participate is excluded up to a scale of 9.0 (11.7)TeV formore » destructive (constructive) interference at 95% confidence level. Finally, lower limits between 5.9 and 8.4TeV on the scale of virtual graviton exchange are extracted for the Arkani-Hamed–Dimopoulos–Dvali model of extra spatial dimensions.« less

Search for quark contact interactions and extra spatial dimensions using dijet angular distributions in proton-proton collisions at √{ s} = 8 TeV

NASA Astrophysics Data System (ADS)

Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Erö, J.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hartl, C.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Kiesenhofer, W.; Knünz, V.; Krammer, M.; Krätschmer, I.; Liko, D.; Mikulec, I.; Rabady, D.; Rahbaran, B.; Rohringer, H.; Schöfbeck, R.; Strauss, J.; Treberer-Treberspurg, W.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Alderweireldt, S.; Bansal, M.; Bansal, S.; Cornelis, T.; De Wolf, E. A.; Janssen, X.; Knutsson, A.; Lauwers, J.; Luyckx, S.; Ochesanu, S.; Rougny, R.; Van De Klundert, M.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Blekman, F.; Blyweert, S.; D'Hondt, J.; Daci, N.; Heracleous, N.; Keaveney, J.; Lowette, S.; Maes, M.; Olbrechts, A.; Python, Q.; Strom, D.; Tavernier, S.; Van Doninck, W.; Van Mulders, P.; Van Onsem, G. P.; Villella, I.; Caillol, C.; Clerbaux, B.; De Lentdecker, G.; Dobur, D.; Favart, L.; Gay, A. P. R.; Grebenyuk, A.; Léonard, A.; Mohammadi, A.; Perniè, L.; Reis, T.; Seva, T.; Thomas, L.; Vander Velde, C.; Vanlaer, P.; Wang, J.; Zenoni, F.; Adler, V.; Beernaert, K.; Benucci, L.; Cimmino, A.; Costantini, S.; Crucy, S.; Dildick, S.; Fagot, A.; Garcia, G.; Mccartin, J.; Ocampo Rios, A. A.; Ryckbosch, D.; Salva Diblen, S.; Sigamani, M.; Strobbe, N.; Thyssen, F.; Tytgat, M.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Beluffi, C.; Bruno, G.; Castello, R.; Caudron, A.; Ceard, L.; Da Silveira, G. G.; Delaere, C.; du Pree, T.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Jafari, A.; Jez, P.; Komm, M.; Lemaitre, V.; Nuttens, C.; Pagano, D.; Perrini, L.; Pin, A.; Piotrzkowski, K.; Popov, A.; Quertenmont, L.; Selvaggi, M.; Vidal Marono, M.; Vizan Garcia, J. M.; Beliy, N.; Caebergs, T.; Daubie, E.; Hammad, G. H.; Aldá Júnior, W. L.; Alves, G. A.; Brito, L.; Correa Martins Junior, M.; Dos Reis Martins, T.; Mora Herrera, C.; Pol, M. E.; Carvalho, W.; Chinellato, J.; Custódio, A.; Da Costa, E. M.; De Jesus Damiao, D.; De Oliveira Martins, C.; Fonseca De Souza, S.; Malbouisson, H.; Matos Figueiredo, D.; Mundim, L.; Nogima, H.; Prado Da Silva, W. L.; Santaolalla, J.; Santoro, A.; Sznajder, A.; Tonelli Manganote, E. J.; Vilela Pereira, A.; Bernardes, C. A.; Dogra, S.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Mercadante, P. G.; Novaes, S. F.; Padula, Sandra S.; Aleksandrov, A.; Genchev, V.; Iaydjiev, P.; Marinov, A.; Piperov, S.; Rodozov, M.; Sultanov, G.; Vutova, M.; Dimitrov, A.; Glushkov, I.; Hadjiiska, R.; Kozhuharov, V.; Litov, L.; Pavlov, B.; Petkov, P.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Chen, M.; Cheng, T.; Du, R.; Jiang, C. H.; Plestina, R.; Romeo, F.; Tao, J.; Wang, Z.; Asawatangtrakuldee, C.; Ban, Y.; Li, Q.; Liu, S.; Mao, Y.; Qian, S. J.; Wang, D.; Zou, W.; Avila, C.; Chaparro Sierra, L. F.; Florez, C.; Gomez, J. P.; Gomez Moreno, B.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Polic, D.; Puljak, I.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Kadija, K.; Luetic, J.; Mekterovic, D.; Sudic, L.; Attikis, A.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Bodlak, M.; Finger, M.; Finger, M.; Assran, Y.; Elgammal, S.; Mahmoud, M. A.; Radi, A.; Kadastik, M.; Murumaa, M.; Raidal, M.; Tiko, A.; Eerola, P.; Fedi, G.; Voutilainen, M.; Härkönen, J.; Karimäki, V.; Kinnunen, R.; Kortelainen, M. J.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Wendland, L.; Talvitie, J.; Tuuva, T.; Besancon, M.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Favaro, C.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Malcles, J.; Rander, J.; Rosowsky, A.; Titov, M.; Baffioni, S.; Beaudette, F.; Busson, P.; Charlot, C.; Dahms, T.; Dalchenko, M.; Dobrzynski, L.; Filipovic, N.; Florent, A.; Granier de Cassagnac, R.; Mastrolorenzo, L.; Miné, P.; Mironov, C.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Paganini, P.; Regnard, S.; Salerno, R.; Sauvan, J. B.; Sirois, Y.; Veelken, C.; Yilmaz, Y.; Zabi, A.; Agram, J.-L.; Andrea, J.; Aubin, A.; Bloch, D.; Brom, J.-M.; Chabert, E. C.; Collard, C.; Conte, E.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Goetzmann, C.; Le Bihan, A.-C.; Van Hove, P.; Gadrat, S.; Beauceron, S.; Beaupere, N.; Boudoul, G.; Bouvier, E.; Brochet, S.; Carrillo Montoya, C. A.; Chasserat, J.; Chierici, R.; Contardo, D.; Depasse, P.; El Mamouni, H.; Fan, J.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Kurca, T.; Lethuillier, M.; Mirabito, L.; Perries, S.; Ruiz Alvarez, J. D.; Sabes, D.; Sgandurra, L.; Sordini, V.; Vander Donckt, M.; Verdier, P.; Viret, S.; Xiao, H.; Tsamalaidze, Z.; Autermann, C.; Beranek, S.; Bontenackels, M.; Edelhoff, M.; Feld, L.; Heister, A.; Hindrichs, O.; Klein, K.; Ostapchuk, A.; Raupach, F.; Sammet, J.; Schael, S.; Weber, H.; Wittmer, B.; Zhukov, V.; Ata, M.; Brodski, M.; Dietz-Laursonn, E.; Duchardt, D.; Erdmann, M.; Fischer, R.; Güth, A.; Hebbeker, T.; Heidemann, C.; Hoepfner, K.; Klingebiel, D.; Knutzen, S.; Kreuzer, P.; Merschmeyer, M.; Meyer, A.; Millet, P.; Olschewski, M.; Padeken, K.; Papacz, P.; Reithler, H.; Schmitz, S. A.; Sonnenschein, L.; Teyssier, D.; Thüer, S.; Weber, M.; Cherepanov, V.; Erdogan, Y.; Flügge, G.; Geenen, H.; Geisler, M.; Haj Ahmad, W.; Hoehle, F.; Kargoll, B.; Kress, T.; Kuessel, Y.; Künsken, A.; Lingemann, J.; Nowack, A.; Nugent, I. M.; Perchalla, L.; Pooth, O.; Stahl, A.; Asin, I.; Bartosik, N.; Behr, J.; Behrenhoff, W.; Behrens, U.; Bell, A. J.; Bergholz, M.; Bethani, A.; Borras, K.; Burgmeier, A.; Cakir, A.; Calligaris, L.; Campbell, A.; Choudhury, S.; Costanza, F.; Diez Pardos, C.; Dolinska, G.; Dooling, S.; Dorland, T.; Eckerlin, G.; Eckstein, D.; Eichhorn, T.; Flucke, G.; Garay Garcia, J.; Geiser, A.; Gunnellini, P.; Hauk, J.; Hempel, M.; Horton, D.; Jung, H.; Kalogeropoulos, A.; Kasemann, M.; Katsas, P.; Kieseler, J.; Kleinwort, C.; Korol, I.; Krücker, D.; Lange, W.; Leonard, J.; Lipka, K.; Lobanov, A.; Lohmann, W.; Lutz, B.; Mankel, R.; Marfin, I.; Melzer-Pellmann, I.-A.; Meyer, A. B.; Mittag, G.; Mnich, J.; Mussgiller, A.; Naumann-Emme, S.; Nayak, A.; Novgorodova, O.; Ntomari, E.; Perrey, H.; Pitzl, D.; Placakyte, R.; Raspereza, A.; Ribeiro Cipriano, P. M.; Roland, B.; Ron, E.; Sahin, M. Ö.; Salfeld-Nebgen, J.; Saxena, P.; Schmidt, R.; Schoerner-Sadenius, T.; Schröder, M.; Seitz, C.; Spannagel, S.; Vargas Trevino, A. D. R.; Walsh, R.; Wissing, C.; Aldaya Martin, M.; Blobel, V.; Centis Vignali, M.; Draeger, A. R.; Erfle, J.; Garutti, E.; Goebel, K.; Görner, M.; Haller, J.; Hoffmann, M.; Höing, R. S.; Kirschenmann, H.; Klanner, R.; Kogler, R.; Lange, J.; Lapsien, T.; Lenz, T.; Marchesini, I.; Ott, J.; Peiffer, T.; Perieanu, A.; Pietsch, N.; Poehlsen, J.; Poehlsen, T.; Rathjens, D.; Sander, C.; Schettler, H.; Schleper, P.; Schlieckau, E.; Schmidt, A.; Seidel, M.; Sola, V.; Stadie, H.; Steinbrück, G.; Troendle, D.; Usai, E.; Vanelderen, L.; Vanhoefer, A.; Barth, C.; Baus, C.; Berger, J.; Böser, C.; Butz, E.; Chwalek, T.; De Boer, W.; Descroix, A.; Dierlamm, A.; Feindt, M.; Frensch, F.; Giffels, M.; Gilbert, A.; Hartmann, F.; Hauth, T.; Husemann, U.; Katkov, I.; Kornmayer, A.; Kuznetsova, E.; Lobelle Pardo, P.; Mozer, M. U.; Müller, Th.; Nürnberg, A.; Quast, G.; Rabbertz, K.; Ratnikov, F.; Röcker, S.; Simonis, H. J.; Stober, F. M.; Ulrich, R.; Wagner-Kuhr, J.; Wayand, S.; Weiler, T.; Wolf, R.; Anagnostou, G.; Daskalakis, G.; Geralis, T.; Giakoumopoulou, V. A.; Kyriakis, A.; Loukas, D.; Markou, A.; Markou, C.; Psallidas, A.; Topsis-Giotis, I.; Agapitos, A.; Kesisoglou, S.; Panagiotou, A.; Saoulidou, N.; Stiliaris, E.; Aslanoglou, X.; Evangelou, I.; Flouris, G.; Foudas, C.; Kokkas, P.; Manthos, N.; Papadopoulos, I.; Paradas, E.; Strologas, J.; Bencze, G.; Hajdu, C.; Hidas, P.; Horvath, D.; Sikler, F.; Veszpremi, V.; Vesztergombi, G.; Zsigmond, A. J.; Beni, N.; Czellar, S.; Karancsi, J.; Molnar, J.; Palinkas, J.; Szillasi, Z.; Makovec, A.; Raics, P.; Trocsanyi, Z. L.; Ujvari, B.; Swain, S. K.; Beri, S. B.; Bhatnagar, V.; Gupta, R.; Bhawandeep, U.; Kalsi, A. K.; Kaur, M.; Kumar, R.; Mittal, M.; Nishu, N.; Singh, J. B.; Kumar, Ashok; Kumar, Arun; Ahuja, S.; Bhardwaj, A.; Choudhary, B. C.; Kumar, A.; Malhotra, S.; Naimuddin, M.; Ranjan, K.; Sharma, V.; Banerjee, S.; Bhattacharya, S.; Chatterjee, K.; Dutta, S.; Gomber, B.; Jain, Sa.; Jain, Sh.; Khurana, R.; Modak, A.; Mukherjee, S.; Roy, D.; Sarkar, S.; Sharan, M.; Abdulsalam, A.; Dutta, D.; Kailas, S.; Kumar, V.; Mohanty, A. K.; Pant, L. M.; Shukla, P.; Topkar, A.; Aziz, T.; Banerjee, S.; Bhowmik, S.; Chatterjee, R. M.; Dewanjee, R. K.; Dugad, S.; Ganguly, S.; Ghosh, S.; Guchait, M.; Gurtu, A.; Kole, G.; Kumar, S.; Maity, M.; Majumder, G.; Mazumdar, K.; Mohanty, G. B.; Parida, B.; Sudhakar, K.; Wickramage, N.; Bakhshiansohi, H.; Behnamian, H.; Etesami, S. M.; Fahim, A.; Goldouzian, R.; Khakzad, M.; Mohammadi Najafabadi, M.; Naseri, M.; Paktinat Mehdiabadi, S.; Rezaei Hosseinabadi, F.; Safarzadeh, B.; Zeinali, M.; Felcini, M.; Grunewald, M.; Abbrescia, M.; Calabria, C.; Chhibra, S. S.; Colaleo, A.; Creanza, D.; De Filippis, N.; De Palma, M.; Fiore, L.; Iaselli, G.; Maggi, G.; Maggi, M.; My, S.; Nuzzo, S.; Pompili, A.; Pugliese, G.; Radogna, R.; Selvaggi, G.; Sharma, A.; Silvestris, L.; Venditti, R.; Abbiendi, G.; Benvenuti, A. C.; Bonacorsi, D.; Braibant-Giacomelli, S.; Brigliadori, L.; Campanini, R.; Capiluppi, P.; Castro, A.; Cavallo, F. R.; Codispoti, G.; Cuffiani, M.; Dallavalle, G. M.; Fabbri, F.; Fanfani, A.; Fasanella, D.; Giacomelli, P.; Grandi, C.; Guiducci, L.; Marcellini, S.; Masetti, G.; Montanari, A.; Navarria, F. L.; Perrotta, A.; Primavera, F.; Rossi, A. M.; Rovelli, T.; Siroli, G. P.; Tosi, N.; Travaglini, R.; Albergo, S.; Cappello, G.; Chiorboli, M.; Costa, S.; Giordano, F.; Potenza, R.; Tricomi, A.; Tuve, C.; Barbagli, G.; Ciulli, V.; Civinini, C.; D'Alessandro, R.; Focardi, E.; Gallo, E.; Gonzi, S.; Gori, V.; Lenzi, P.; Meschini, M.; Paoletti, S.; Sguazzoni, G.; Tropiano, A.; Benussi, L.; Bianco, S.; Fabbri, F.; Piccolo, D.; Ferretti, R.; Ferro, F.; Lo Vetere, M.; Robutti, E.; Tosi, S.; Dinardo, M. E.; Fiorendi, S.; Gennai, S.; Gerosa, R.; Ghezzi, A.; Govoni, P.; Lucchini, M. T.; Malvezzi, S.; Manzoni, R. A.; Martelli, A.; Marzocchi, B.; Menasce, D.; Moroni, L.; Paganoni, M.; Pedrini, D.; Ragazzi, S.; Redaelli, N.; Tabarelli de Fatis, T.; Buontempo, S.; Cavallo, N.; Di Guida, S.; Fabozzi, F.; Iorio, A. O. M.; Lista, L.; Meola, S.; Merola, M.; Paolucci, P.; Azzi, P.; Bacchetta, N.; Bisello, D.; Branca, A.; Carlin, R.; Checchia, P.; Dall'Osso, M.; Dorigo, T.; Dosselli, U.; Galanti, M.; Gasparini, F.; Gasparini, U.; Giubilato, P.; Gozzelino, A.; Kanishchev, K.; Lacaprara, S.; Margoni, M.; Meneguzzo, A. T.; Pazzini, J.; Pozzobon, N.; Ronchese, P.; Simonetto, F.; Torassa, E.; Tosi, M.; Zotto, P.; Zucchetta, A.; Zumerle, G.; Gabusi, M.; Ratti, S. P.; Re, V.; Riccardi, C.; Salvini, P.; Vitulo, P.; Biasini, M.; Bilei, G. M.; Ciangottini, D.; Fanò, L.; Lariccia, P.; Mantovani, G.; Menichelli, M.; Saha, A.; Santocchia, A.; Spiezia, A.; Androsov, K.; Azzurri, P.; Bagliesi, G.; Bernardini, J.; Boccali, T.; Broccolo, G.; Castaldi, R.; Ciocci, M. A.; Dell'Orso, R.; Donato, S.; Fiori, F.; Foà, L.; Giassi, A.; Grippo, M. T.; Ligabue, F.; Lomtadze, T.; Martini, L.; Messineo, A.; Moon, C. S.; Palla, F.; Rizzi, A.; Savoy-Navarro, A.; Serban, A. T.; Spagnolo, P.; Squillacioti, P.; Tenchini, R.; Tonelli, G.; Venturi, A.; Verdini, P. G.; Vernieri, C.; Barone, L.; Cavallari, F.; D'imperio, G.; Del Re, D.; Diemoz, M.; Jorda, C.; Longo, E.; Margaroli, F.; Meridiani, P.; Micheli, F.; Nourbakhsh, S.; Organtini, G.; Paramatti, R.; Rahatlou, S.; Rovelli, C.; Santanastasio, F.; Soffi, L.; Traczyk, P.; Amapane, N.; Arcidiacono, R.; Argiro, S.; Arneodo, M.; Bellan, R.; Biino, C.; Cartiglia, N.; Casasso, S.; Costa, M.; Degano, A.; Demaria, N.; Finco, L.; Mariotti, C.; Maselli, S.; Migliore, E.; Monaco, V.; Musich, M.; Obertino, M. M.; Ortona, G.; Pacher, L.; Pastrone, N.; Pelliccioni, M.; Pinna Angioni, G. L.; Potenza, A.; Romero, A.; Ruspa, M.; Sacchi, R.; Solano, A.; Staiano, A.; Tamponi, U.; Belforte, S.; Candelise, V.; Casarsa, M.; Cossutti, F.; Della Ricca, G.; Gobbo, B.; La Licata, C.; Marone, M.; Schizzi, A.; Umer, T.; Zanetti, A.; Chang, S.; Kropivnitskaya, A.; Nam, S. K.; Kim, D. H.; Kim, G. N.; Kim, M. S.; Kong, D. J.; Lee, S.; Oh, Y. D.; Park, H.; Sakharov, A.; Son, D. C.; Kim, T. J.; Kim, J. Y.; Song, S.; Choi, S.; Gyun, D.; Hong, B.; Jo, M.; Kim, H.; Kim, Y.; Lee, B.; Lee, K. S.; Park, S. K.; Roh, Y.; Choi, M.; Kim, J. H.; Park, I. C.; Ryu, G.; Ryu, M. S.; Choi, Y.; Choi, Y. K.; Goh, J.; Kim, D.; Kwon, E.; Lee, J.; Seo, H.; Yu, I.; Juodagalvis, A.; Komaragiri, J. R.; Md Ali, M. A. B.; Casimiro Linares, E.; Castilla-Valdez, H.; De La Cruz-Burelo, E.; Heredia-de La Cruz, I.; Hernandez-Almada, A.; Lopez-Fernandez, R.; Sanchez-Hernandez, A.; Carrillo Moreno, S.; Vazquez Valencia, F.; Pedraza, I.; Salazar Ibarguen, H. A.; Morelos Pineda, A.; Krofcheck, D.; Butler, P. H.; Reucroft, S.; Ahmad, A.; Ahmad, M.; Hassan, Q.; Hoorani, H. R.; Khan, W. A.; Khurshid, T.; Shoaib, M.; Bialkowska, H.; Bluj, M.; Boimska, B.; Frueboes, T.; Górski, M.; Kazana, M.; Nawrocki, K.; Romanowska-Rybinska, K.; Szleper, M.; Zalewski, P.; Brona, G.; Bunkowski, K.; Cwiok, M.; Dominik, W.; Doroba, K.; Kalinowski, A.; Konecki, M.; Krolikowski, J.; Misiura, M.; Olszewski, M.; Wolszczak, W.; Bargassa, P.; Beirão Da Cruz E Silva, C.; Faccioli, P.; Ferreira Parracho, P. G.; Gallinaro, M.; Lloret Iglesias, L.; Nguyen, F.; Rodrigues Antunes, J.; Seixas, J.; Varela, J.; Vischia, P.; Bunin, P.; Gavrilenko, M.; Golutvin, I.; Gorbunov, I.; Karjavin, V.; Konoplyanikov, V.; Lanev, A.; Malakhov, A.; Matveev, V.; Moisenz, P.; Palichik, V.; Perelygin, V.; Savina, M.; Shmatov, S.; Shulha, S.; Skatchkov, N.; Smirnov, V.; Zarubin, A.; Golovtsov, V.; Ivanov, Y.; Kim, V.; Levchenko, P.; Murzin, V.; Oreshkin, V.; Smirnov, I.; Sulimov, V.; Uvarov, L.; Vavilov, S.; Vorobyev, A.; Vorobyev, An.; Andreev, Yu.; Dermenev, A.; Gninenko, S.; Golubev, N.; Kirsanov, M.; Krasnikov, N.; Pashenkov, A.; Tlisov, D.; Toropin, A.; Epshteyn, V.; Gavrilov, V.; Lychkovskaya, N.; Popov, V.; Pozdnyakov, I.; Safronov, G.; Semenov, S.; Spiridonov, A.; Stolin, V.; Vlasov, E.; Zhokin, A.; Andreev, V.; Azarkin, M.; Dremin, I.; Kirakosyan, M.; Leonidov, A.; Mesyats, G.; Rusakov, S. V.; Vinogradov, A.; Belyaev, A.; Boos, E.; Bunichev, V.; Dubinin, M.; Dudko, L.; Ershov, A.; Klyukhin, V.; Kodolova, O.; Lokhtin, I.; Obraztsov, S.; Perfilov, M.; Petrushanko, S.; Savrin, V.; Azhgirey, I.; Bayshev, I.; Bitioukov, S.; Kachanov, V.; Kalinin, A.; Konstantinov, D.; Krychkine, V.; Petrov, V.; Ryutin, R.; Sobol, A.; Tourtchanovitch, L.; Troshin, S.; Tyurin, N.; Uzunian, A.; Volkov, A.; Adzic, P.; Ekmedzic, M.; Milosevic, J.; Rekovic, V.; Alcaraz Maestre, J.; Battilana, C.; Calvo, E.; Cerrada, M.; Chamizo Llatas, M.; Colino, N.; De La Cruz, B.; Delgado Peris, A.; Domínguez Vázquez, D.; Escalante Del Valle, A.; Fernandez Bedoya, C.; Fernández Ramos, J. P.; Flix, J.; Fouz, M. C.; Garcia-Abia, P.; Gonzalez Lopez, O.; Goy Lopez, S.; Hernandez, J. M.; Josa, M. I.; Navarro De Martino, E.; Pérez-Calero Yzquierdo, A.; Puerta Pelayo, J.; Quintario Olmeda, A.; Redondo, I.; Romero, L.; Soares, M. S.; Albajar, C.; de Trocóniz, J. F.; Missiroli, M.; Moran, D.; Brun, H.; Cuevas, J.; Fernandez Menendez, J.; Folgueras, S.; Gonzalez Caballero, I.; Brochero Cifuentes, J. A.; Cabrillo, I. J.; Calderon, A.; Duarte Campderros, J.; Fernandez, M.; Gomez, G.; Graziano, A.; Lopez Virto, A.; Marco, J.; Marco, R.; Martinez Rivero, C.; Matorras, F.; Munoz Sanchez, F. J.; Piedra Gomez, J.; Rodrigo, T.; Rodríguez-Marrero, A. Y.; Ruiz-Jimeno, A.; Scodellaro, L.; Vila, I.; Vilar Cortabitarte, R.; Abbaneo, D.; Auffray, E.; Auzinger, G.; Bachtis, M.; Baillon, P.; Ball, A. H.; Barney, D.; Benaglia, A.; Bendavid, J.; Benhabib, L.; Benitez, J. F.; Bernet, C.; Bloch, P.; Bocci, A.; Bonato, A.; Bondu, O.; Botta, C.; Breuker, H.; Camporesi, T.; Cerminara, G.; Colafranceschi, S.; D'Alfonso, M.; d'Enterria, D.; Dabrowski, A.; David, A.; De Guio, F.; De Roeck, A.; De Visscher, S.; Di Marco, E.; Dobson, M.; Dordevic, M.; Dorney, B.; Dupont-Sagorin, N.; Elliott-Peisert, A.; Eugster, J.; Franzoni, G.; Funk, W.; Gigi, D.; Gill, K.; Giordano, D.; Girone, M.; Glege, F.; Guida, R.; Gundacker, S.; Guthoff, M.; Hammer, J.; Hansen, M.; Harris, P.; Hegeman, J.; Innocente, V.; Janot, P.; Kousouris, K.; Krajczar, K.; Lecoq, P.; Lourenço, C.; Magini, N.; Malgeri, L.; Mannelli, M.; Marrouche, J.; Masetti, L.; Meijers, F.; Mersi, S.; Meschi, E.; Moortgat, F.; Morovic, S.; Mulders, M.; Musella, P.; Orsini, L.; Pape, L.; Perez, E.; Perrozzi, L.; Petrilli, A.; Petrucciani, G.; Pfeiffer, A.; Pierini, M.; Pimiä, M.; Piparo, D.; Plagge, M.; Racz, A.; Rolandi, G.; Rovere, M.; Sakulin, H.; Schäfer, C.; Schwick, C.; Sharma, A.; Siegrist, P.; Silva, P.; Simon, M.; Sphicas, P.; Spiga, D.; Steggemann, J.; Stieger, B.; Stoye, M.; Takahashi, Y.; Treille, D.; Tsirou, A.; Veres, G. I.; Wardle, N.; Wöhri, H. K.; Wollny, H.; Zeuner, W. D.; Bertl, W.; Deiters, K.; Erdmann, W.; Horisberger, R.; Ingram, Q.; Kaestli, H. C.; Kotlinski, D.; Langenegger, U.; Renker, D.; Rohe, T.; Bachmair, F.; Bäni, L.; Bianchini, L.; Buchmann, M. A.; Casal, B.; Chanon, N.; Dissertori, G.; Dittmar, M.; Donegà, M.; Dünser, M.; Eller, P.; Grab, C.; Hits, D.; Hoss, J.; Lustermann, W.; Mangano, B.; Marini, A. C.; Martinez Ruiz del Arbol, P.; Masciovecchio, M.; Meister, D.; Mohr, N.; Nägeli, C.; Nessi-Tedaldi, F.; Pandolfi, F.; Pauss, F.; Peruzzi, M.; Quittnat, M.; Rebane, L.; Rossini, M.; Starodumov, A.; Takahashi, M.; Theofilatos, K.; Wallny, R.; Weber, H. A.; Amsler, C.; Canelli, M. F.; Chiochia, V.; De Cosa, A.; Hinzmann, A.; Hreus, T.; Kilminster, B.; Lange, C.; Millan Mejias, B.; Ngadiuba, J.; Robmann, P.; Ronga, F. J.; Taroni, S.; Verzetti, M.; Yang, Y.; Cardaci, M.; Chen, K. H.; Ferro, C.; Kuo, C. M.; Lin, W.; Lu, Y. J.; Volpe, R.; Yu, S. S.; Chang, P.; Chang, Y. H.; Chang, Y. W.; Chao, Y.; Chen, K. F.; Chen, P. H.; Dietz, C.; Grundler, U.; Hou, W.-S.; Kao, K. Y.; Lei, Y. J.; Liu, Y. F.; Lu, R.-S.; Majumder, D.; Petrakou, E.; Tzeng, Y. M.; Wilken, R.; Asavapibhop, B.; Singh, G.; Srimanobhas, N.; Suwonjandee, N.; Adiguzel, A.; Bakirci, M. N.; Cerci, S.; Dozen, C.; Dumanoglu, I.; Eskut, E.; Girgis, S.; Gokbulut, G.; Gurpinar, E.; Hos, I.; Kangal, E. E.; Kayis Topaksu, A.; Onengut, G.; Ozdemir, K.; Ozturk, S.; Polatoz, A.; Sunar Cerci, D.; Tali, B.; Topakli, H.; Vergili, M.; Akin, I. V.; Bilin, B.; Bilmis, S.; Gamsizkan, H.; Isildak, B.; Karapinar, G.; Ocalan, K.; Sekmen, S.; Surat, U. E.; Yalvac, M.; Zeyrek, M.; Albayrak, E. A.; Gülmez, E.; Kaya, M.; Kaya, O.; Yetkin, T.; Cankocak, K.; Vardarlı, F. I.; Levchuk, L.; Sorokin, P.; Brooke, J. J.; Clement, E.; Cussans, D.; Flacher, H.; Goldstein, J.; Grimes, M.; Heath, G. P.; Heath, H. F.; Jacob, J.; Kreczko, L.; Lucas, C.; Meng, Z.; Newbold, D. M.; Paramesvaran, S.; Poll, A.; Sakuma, T.; Senkin, S.; Smith, V. J.; Williams, T.; Bell, K. W.; Belyaev, A.; Brew, C.; Brown, R. M.; Cockerill, D. J. A.; Coughlan, J. A.; Harder, K.; Harper, S.; Olaiya, E.; Petyt, D.; Shepherd-Themistocleous, C. H.; Thea, A.; Tomalin, I. R.; Womersley, W. J.; Worm, S. D.; Baber, M.; Bainbridge, R.; Buchmuller, O.; Burton, D.; Colling, D.; Cripps, N.; Cutajar, M.; Dauncey, P.; Davies, G.; Della Negra, M.; Dunne, P.; Ferguson, W.; Fulcher, J.; Futyan, D.; Hall, G.; Iles, G.; Jarvis, M.; Karapostoli, G.; Kenzie, M.; Lane, R.; Lucas, R.; Lyons, L.; Magnan, A.-M.; Malik, S.; Mathias, B.; Nash, J.; Nikitenko, A.; Pela, J.; Pesaresi, M.; Petridis, K.; Raymond, D. M.; Rogerson, S.; Rose, A.; Seez, C.; Sharp, P.; Tapper, A.; Vazquez Acosta, M.; Virdee, T.; Zenz, S. C.; Cole, J. E.; Hobson, P. R.; Khan, A.; Kyberd, P.; Leggat, D.; Leslie, D.; Martin, W.; Reid, I. D.; Symonds, P.; Teodorescu, L.; Turner, M.; Dittmann, J.; Hatakeyama, K.; Kasmi, A.; Liu, H.; Scarborough, T.; Charaf, O.; Cooper, S. I.; Henderson, C.; Rumerio, P.; Avetisyan, A.; Bose, T.; Fantasia, C.; Lawson, P.; Richardson, C.; Rohlf, J.; St. John, J.; Sulak, L.; Alimena, J.; Berry, E.; Bhattacharya, S.; Christopher, G.; Cutts, D.; Demiragli, Z.; Dhingra, N.; Ferapontov, A.; Garabedian, A.; Heintz, U.; Kukartsev, G.; Laird, E.; Landsberg, G.; Luk, M.; Narain, M.; Segala, M.; Sinthuprasith, T.; Speer, T.; Swanson, J.; Breedon, R.; Breto, G.; Calderon De La Barca Sanchez, M.; Chauhan, S.; Chertok, M.; Conway, J.; Conway, R.; Cox, P. T.; Erbacher, R.; Gardner, M.; Ko, W.; Lander, R.; Miceli, T.; Mulhearn, M.; Pellett, D.; Pilot, J.; Ricci-Tam, F.; Searle, M.; Shalhout, S.; Smith, J.; Squires, M.; Stolp, D.; Tripathi, M.; Wilbur, S.; Yohay, R.; Cousins, R.; Everaerts, P.; Farrell, C.; Hauser, J.; Ignatenko, M.; Rakness, G.; Takasugi, E.; Valuev, V.; Weber, M.; Burt, K.; Clare, R.; Ellison, J.; Gary, J. W.; Hanson, G.; Heilman, J.; Ivova Rikova, M.; Jandir, P.; Kennedy, E.; Lacroix, F.; Long, O. R.; Luthra, A.; Malberti, M.; Olmedo Negrete, M.; Shrinivas, A.; Sumowidagdo, S.; Wimpenny, S.; Branson, J. G.; Cerati, G. B.; Cittolin, S.; D'Agnolo, R. T.; Holzner, A.; Kelley, R.; Klein, D.; Letts, J.; Macneill, I.; Olivito, D.; Padhi, S.; Palmer, C.; Pieri, M.; Sani, M.; Sharma, V.; Simon, S.; Sudano, E.; Tadel, M.; Tu, Y.; Vartak, A.; Welke, C.; Würthwein, F.; Yagil, A.; Barge, D.; Bradmiller-Feld, J.; Campagnari, C.; Danielson, T.; Dishaw, A.; Dutta, V.; Flowers, K.; Franco Sevilla, M.; Geffert, P.; George, C.; Golf, F.; Gouskos, L.; Incandela, J.; Justus, C.; Mccoll, N.; Richman, J.; Stuart, D.; To, W.; West, C.; Yoo, J.; Apresyan, A.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Rogan, C.; Spiropulu, M.; Timciuc, V.; Vlimant, J. R.; Wilkinson, R.; Xie, S.; Zhu, R. Y.; Azzolini, V.; Calamba, A.; Carlson, B.; Ferguson, T.; Iiyama, Y.; Paulini, M.; Russ, J.; Vogel, H.; Vorobiev, I.; Cumalat, J. P.; Ford, W. T.; Gaz, A.; Krohn, M.; Luiggi Lopez, E.; Nauenberg, U.; Smith, J. G.; Stenson, K.; Ulmer, K. A.; Wagner, S. R.; Alexander, J.; Chatterjee, A.; Chaves, J.; Chu, J.; Dittmer, S.; Eggert, N.; Mirman, N.; Nicolas Kaufman, G.; Patterson, J. R.; Ryd, A.; Salvati, E.; Skinnari, L.; Sun, W.; Teo, W. D.; Thom, J.; Thompson, J.; Tucker, J.; Weng, Y.; Winstrom, L.; Wittich, P.; Winn, D.; Abdullin, S.; Albrow, M.; Anderson, J.; Apollinari, G.; Bauerdick, L. A. T.; Beretvas, A.; Berryhill, J.; Bhat, P. C.; Bolla, G.; Burkett, K.; Butler, J. N.; Cheung, H. W. K.; Chlebana, F.; Cihangir, S.; Elvira, V. D.; Fisk, I.; Freeman, J.; Gao, Y.; Gottschalk, E.; Gray, L.; Green, D.; Grünendahl, S.; Gutsche, O.; Hanlon, J.; Hare, D.; Harris, R. M.; Hirschauer, J.; Hooberman, B.; Jindariani, S.; Johnson, M.; Joshi, U.; Kaadze, K.; Klima, B.; Kreis, B.; Kwan, S.; Linacre, J.; Lincoln, D.; Lipton, R.; Liu, T.; Lykken, J.; Maeshima, K.; Marraffino, J. M.; Martinez Outschoorn, V. I.; Maruyama, S.; Mason, D.; McBride, P.; Merkel, P.; Mishra, K.; Mrenna, S.; Musienko, Y.; Nahn, S.; Newman-Holmes, C.; O'Dell, V.; Prokofyev, O.; Sexton-Kennedy, E.; Sharma, S.; Soha, A.; Spalding, W. J.; Spiegel, L.; Taylor, L.; Tkaczyk, S.; Tran, N. V.; Uplegger, L.; Vaandering, E. W.; Vidal, R.; Whitbeck, A.; Whitmore, J.; Yang, F.; Acosta, D.; Avery, P.; Bortignon, P.; Bourilkov, D.; Carver, M.; Curry, D.; Das, S.; De Gruttola, M.; Di Giovanni, G. P.; Field, R. D.; Fisher, M.; Furic, I. K.; Hugon, J.; Konigsberg, J.; Korytov, A.; Kypreos, T.; Low, J. F.; Matchev, K.; Milenovic, P.; Mitselmakher, G.; Muniz, L.; Rinkevicius, A.; Shchutska, L.; Snowball, M.; Sperka, D.; Yelton, J.; Zakaria, M.; Hewamanage, S.; Linn, S.; Markowitz, P.; Martinez, G.; Rodriguez, J. L.; Adams, T.; Askew, A.; Bochenek, J.; Diamond, B.; Haas, J.; Hagopian, S.; Hagopian, V.; Johnson, K. F.; Prosper, H.; Veeraraghavan, V.; Weinberg, M.; Baarmand, M. M.; Hohlmann, M.; Kalakhety, H.; Yumiceva, F.; Adams, M. R.; Apanasevich, L.; Bazterra, V. E.; Berry, D.; Betts, R. R.; Bucinskaite, I.; Cavanaugh, R.; Evdokimov, O.; Gauthier, L.; Gerber, C. E.; Hofman, D. J.; Khalatyan, S.; Kurt, P.; Moon, D. H.; O'Brien, C.; Silkworth, C.; Turner, P.; Varelas, N.; Bilki, B.; Clarida, W.; Dilsiz, K.; Duru, F.; Haytmyradov, M.; Merlo, J.-P.; Mermerkaya, H.; Mestvirishvili, A.; Moeller, A.; Nachtman, J.; Ogul, H.; Onel, Y.; Ozok, F.; Penzo, A.; Rahmat, R.; Sen, S.; Tan, P.; Tiras, E.; Wetzel, J.; Yi, K.; Barnett, B. A.; Blumenfeld, B.; Bolognesi, S.; Fehling, D.; Gritsan, A. V.; Maksimovic, P.; Martin, C.; Swartz, M.; Baringer, P.; Bean, A.; Benelli, G.; Bruner, C.; Kenny, R. P., III; Malek, M.; Murray, M.; Noonan, D.; Sanders, S.; Sekaric, J.; Stringer, R.; Wang, Q.; Wood, J. S.; Chakaberia, I.; Ivanov, A.; Khalil, S.; Makouski, M.; Maravin, Y.; Saini, L. K.; Shrestha, S.; Skhirtladze, N.; Svintradze, I.; Gronberg, J.; Lange, D.; Rebassoo, F.; Wright, D.; Baden, A.; Belloni, A.; Calvert, B.; Eno, S. C.; Gomez, J. A.; Hadley, N. J.; Kellogg, R. G.; Kolberg, T.; Lu, Y.; Marionneau, M.; Mignerey, A. C.; Pedro, K.; Skuja, A.; Tonjes, M. B.; Tonwar, S. C.; Apyan, A.; Barbieri, R.; Bauer, G.; Busza, W.; Cali, I. A.; Chan, M.; Di Matteo, L.; Gomez Ceballos, G.; Goncharov, M.; Gulhan, D.; Klute, M.; Lai, Y. S.; Lee, Y.-J.; Levin, A.; Luckey, P. D.; Ma, T.; Paus, C.; Ralph, D.; Roland, C.; Roland, G.; Stephans, G. S. F.; Stöckli, F.; Sumorok, K.; Velicanu, D.; Veverka, J.; Wyslouch, B.; Yang, M.; Zanetti, M.; Zhukova, V.; Dahmes, B.; Gude, A.; Kao, S. C.; Klapoetke, K.; Kubota, Y.; Mans, J.; Pastika, N.; Rusack, R.; Singovsky, A.; Tambe, N.; Turkewitz, J.; Acosta, J. G.; Oliveros, S.; Avdeeva, E.; Bloom, K.; Bose, S.; Claes, D. R.; Dominguez, A.; Gonzalez Suarez, R.; Keller, J.; Knowlton, D.; Kravchenko, I.; Lazo-Flores, J.; Malik, S.; Meier, F.; Snow, G. R.; Zvada, M.; Dolen, J.; Godshalk, A.; Iashvili, I.; Kharchilava, A.; Kumar, A.; Rappoccio, S.; Alverson, G.; Barberis, E.; Baumgartel, D.; Chasco, M.; Haley, J.; Massironi, A.; Morse, D. M.; Nash, D.; Orimoto, T.; Trocino, D.; Wang, R.-J.; Wood, D.; Zhang, J.; Hahn, K. A.; Kubik, A.; Mucia, N.; Odell, N.; Pollack, B.; Pozdnyakov, A.; Schmitt, M.; Stoynev, S.; Sung, K.; Velasco, M.; Won, S.; Brinkerhoff, A.; Chan, K. M.; Drozdetskiy, A.; Hildreth, M.; Jessop, C.; Karmgard, D. J.; Kellams, N.; Lannon, K.; Luo, W.; Lynch, S.; Marinelli, N.; Pearson, T.; Planer, M.; Ruchti, R.; Valls, N.; Wayne, M.; Wolf, M.; Woodard, A.; Antonelli, L.; Brinson, J.; Bylsma, B.; Durkin, L. S.; Flowers, S.; Hart, A.; Hill, C.; Hughes, R.; Kotov, K.; Ling, T. Y.; Puigh, D.; Rodenburg, M.; Smith, G.; Winer, B. L.; Wolfe, H.; Wulsin, H. W.; Driga, O.; Elmer, P.; Hardenbrook, J.; Hebda, P.; Hunt, A.; Koay, S. A.; Lujan, P.; Marlow, D.; Medvedeva, T.; Mooney, M.; Olsen, J.; Piroué, P.; Quan, X.; Saka, H.; Stickland, D.; Tully, C.; Werner, J. S.; Zuranski, A.; Brownson, E.; Mendez, H.; Ramirez Vargas, J. E.; Barnes, V. E.; Benedetti, D.; Bortoletto, D.; De Mattia, M.; Gutay, L.; Hu, Z.; Jha, M. K.; Jones, M.; Jung, K.; Kress, M.; Leonardo, N.; Lopes Pegna, D.; Maroussov, V.; Miller, D. H.; Neumeister, N.; Radburn-Smith, B. C.; Shi, X.; Shipsey, I.; Silvers, D.; Svyatkovskiy, A.; Wang, F.; Xie, W.; Xu, L.; Yoo, H. D.; Zablocki, J.; Zheng, Y.; Parashar, N.; Stupak, J.; Adair, A.; Akgun, B.; Ecklund, K. M.; Geurts, F. J. M.; Li, W.; Michlin, B.; Padley, B. P.; Redjimi, R.; Roberts, J.; Zabel, J.; Betchart, B.; Bodek, A.; Covarelli, R.; de Barbaro, P.; Demina, R.; Eshaq, Y.; Ferbel, T.; Garcia-Bellido, A.; Goldenzweig, P.; Han, J.; Harel, A.; Khukhunaishvili, A.; Korjenevski, S.; Petrillo, G.; Vishnevskiy, D.; Ciesielski, R.; Demortier, L.; Goulianos, K.; Lungu, G.; Mesropian, C.; Arora, S.; Barker, A.; Chou, J. P.; Contreras-Campana, C.; Contreras-Campana, E.; Duggan, D.; Ferencek, D.; Gershtein, Y.; Gray, R.; Halkiadakis, E.; Hidas, D.; Kaplan, S.; Lath, A.; Panwalkar, S.; Park, M.; Patel, R.; Salur, S.; Schnetzer, S.; Somalwar, S.; Stone, R.; Thomas, S.; Thomassen, P.; Walker, M.; Rose, K.; Spanier, S.; York, A.; Bouhali, O.; Castaneda Hernandez, A.; Eusebi, R.; Flanagan, W.; Gilmore, J.; Kamon, T.; Khotilovich, V.; Krutelyov, V.; Montalvo, R.; Osipenkov, I.; Pakhotin, Y.; Perloff, A.; Roe, J.; Rose, A.; Safonov, A.; Suarez, I.; Tatarinov, A.; Akchurin, N.; Cowden, C.; Damgov, J.; Dragoiu, C.; Dudero, P. R.; Faulkner, J.; Kovitanggoon, K.; Kunori, S.; Lee, S. W.; Libeiro, T.; Volobouev, I.; Appelt, E.; Delannoy, A. G.; Greene, S.; Gurrola, A.; Johns, W.; Maguire, C.; Mao, Y.; Melo, A.; Sharma, M.; Sheldon, P.; Snook, B.; Tuo, S.; Velkovska, J.; Arenton, M. W.; Boutle, S.; Cox, B.; Francis, B.; Goodell, J.; Hirosky, R.; Ledovskoy, A.; Li, H.; Lin, C.; Neu, C.; Wood, J.; Clarke, C.; Harr, R.; Karchin, P. E.; Kottachchi Kankanamge Don, C.; Lamichhane, P.; Sturdy, J.; Belknap, D. A.; Carlsmith, D.; Cepeda, M.; Dasu, S.; Dodd, L.; Duric, S.; Friis, E.; Hall-Wilton, R.; Herndon, M.; Hervé, A.; Klabbers, P.; Lanaro, A.; Lazaridis, C.; Levine, A.; Loveless, R.; Mohapatra, A.; Ojalvo, I.; Perry, T.; Pierro, G. A.; Polese, G.; Ross, I.; Sarangi, T.; Savin, A.; Smith, W. H.; Taylor, D.; Verwilligen, P.; Vuosalo, C.; Woods, N.

2015-06-01

A search is presented for quark contact interactions and extra spatial dimensions in proton-proton collisions at √{ s} = 8 TeV using dijet angular distributions. The search is based on a data set corresponding to an integrated luminosity of 19.7 fb-1 collected by the CMS detector at the CERN LHC. Dijet angular distributions are found to be in agreement with the perturbative QCD predictions that include electroweak corrections. Limits on the contact interaction scale from a variety of models at next-to-leading order in QCD corrections are obtained. A benchmark model in which only left-handed quarks participate is excluded up to a scale of 9.0 (11.7) TeV for destructive (constructive) interference at 95% confidence level. Lower limits between 5.9 and 8.4 TeV on the scale of virtual graviton exchange are extracted for the Arkani-Hamed-Dimopoulos-Dvali model of extra spatial dimensions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, C. D.; Schmidt, S. M.; Physics

Continuum strong QCD is the application of models and continuum quantum field theory to the study of phenomena in hadronic physics, which includes; e.g., the spectrum of QCD bound states and their interactions; and the transition to, and properties of, a quark gluon plasma. We provide a contemporary perspective, couched primarily in terms of the Dyson-Schwinger equations but also making comparisons with other approaches and models. Our discourse provides a practitioners' guide to features of the Dyson-Schwinger equations [such as confinement and dynamical chiral symmetry breaking] and canvasses phenomenological applications to light meson and baryon properties in cold, sparse QCD.more » These provide the foundation for an extension to hot, dense QCD, which is probed via the introduction of the intensive thermodynamic variables: chemical potential and temperature. We describe order parameters whose evolution signals deconfinement and chiral symmetry restoration, and chronicle their use in demarcating the quark gluon plasma phase boundary and characterizing the plasma's properties. Hadron traits change in an equilibrated plasma. We exemplify this and discuss putative signals of the effects. Finally, since plasma formation is not an equilibrium process, we discuss recent developments in kinetic theory and its application to describing the evolution from a relativistic heavy ion collision to an equilibrated quark gluon plasma.« less

Computer Simulation of Electron Positron Annihilation Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, y

2003-10-02

With the launching of the Next Linear Collider coming closer and closer, there is a pressing need for physicists to develop a fully-integrated computer simulation of e{sup +}e{sup -} annihilation process at center-of-mass energy of 1TeV. A simulation program acts as the template for future experiments. Either new physics will be discovered, or current theoretical uncertainties will shrink due to more accurate higher-order radiative correction calculations. The existence of an efficient and accurate simulation will help us understand the new data and validate (or veto) some of the theoretical models developed to explain new physics. It should handle well interfacesmore » between different sectors of physics, e.g., interactions happening at parton levels well above the QCD scale which are described by perturbative QCD, and interactions happening at much lower energy scale, which combine partons into hadrons. Also it should achieve competitive speed in real time when the complexity of the simulation increases. This thesis contributes some tools that will be useful for the development of such simulation programs. We begin our study by the development of a new Monte Carlo algorithm intended to perform efficiently in selecting weight-1 events when multiple parameter dimensions are strongly correlated. The algorithm first seeks to model the peaks of the distribution by features, adapting these features to the function using the EM algorithm. The representation of the distribution provided by these features is then improved using the VEGAS algorithm for the Monte Carlo integration. The two strategies mesh neatly into an effective multi-channel adaptive representation. We then present a new algorithm for the simulation of parton shower processes in high energy QCD. We want to find an algorithm which is free of negative weights, produces its output as a set of exclusive events, and whose total rate exactly matches the full Feynman amplitude calculation. Our strategy is to create the whole QCD shower as a tree structure generated by a multiple Poisson process. Working with the whole shower allows us to include correlations between gluon emissions from different sources. QCD destructive interference is controlled by the implementation of ''angular-ordering,'' as in the HERWIG Monte Carlo program. We discuss methods for systematic improvement of the approach to include higher order QCD effects.« less

A minimal scale invariant axion solution to the strong CP-problem

NASA Astrophysics Data System (ADS)

Tokareva, Anna

2018-05-01

We present a scale-invariant extension of the Standard model allowing for the Kim-Shifman-Vainstein-Zakharov (KSVZ) axion solution of the strong CP problem in QCD. We add the minimal number of new particles and show that the Peccei-Quinn scalar might be identified with the complex dilaton field. Scale invariance, together with the Peccei-Quinn symmetry, is broken spontaneously near the Planck scale before inflation, which is driven by the Standard Model Higgs field. We present a set of general conditions which makes this scenario viable and an explicit example of an effective theory possessing spontaneous breaking of scale invariance. We show that this description works both for inflation and low-energy physics in the electroweak vacuum. This scenario can provide a self-consistent inflationary stage and, at the same time, successfully avoid the cosmological bounds on the axion. Our general predictions are the existence of colored TeV mass fermion and the QCD axion. The latter has all the properties of the KSVZ axion but does not contribute to dark matter. This axion can be searched via its mixing to a photon in an external magnetic field.

The Secret Life of Quarks, Final Report for the University of North Carolina at Chapel Hill

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fowler, Robert J.

This final report summarizes activities and results at the University of North Carolina as part of the the SciDAC-2 Project The Secret Life of Quarks: National Computational Infrastructure for Lattice Quantum Chromodynamics. The overall objective of the project is to construct the software needed to study quantum chromo- dynamics (QCD), the theory of the strong interactions of subatomic physics, and similar strongly coupled gauge theories anticipated to be of importance in the LHC era. It built upon the successful efforts of the SciDAC-1 project National Computational Infrastructure for Lattice Gauge Theory, in which a QCD Applications Programming Interface (QCD API)more » was developed that enables lat- tice gauge theorists to make effective use of a wide variety of massively parallel computers. In the SciDAC-2 project, optimized versions of the QCD API were being created for the IBM Blue- Gene/L (BG/L) and BlueGene/P (BG/P), the Cray XT3/XT4 and its successors, and clusters based on multi-core processors and Infiniband communications networks. The QCD API is being used to enhance the performance of the major QCD community codes and to create new applications. Software libraries of physics tools have been expanded to contain sharable building blocks for inclusion in application codes, performance analysis and visualization tools, and software for au- tomation of physics work flow. New software tools were designed for managing the large data sets generated in lattice QCD simulations, and for sharing them through the International Lattice Data Grid consortium. As part of the overall project, researchers at UNC were funded through ASCR to work in three general areas. The main thrust has been performance instrumentation and analysis in support of the SciDAC QCD code base as it evolved and as it moved to new computation platforms. In support of the performance activities, performance data was to be collected in a database for the purpose of broader analysis. Third, the UNC work was done at RENCI (Renaissance Computing Institute), which has extensive expertise and facilities for scientific data visualization, so we acted in an ongoing consulting and support role in that area.« less

A precise determination of the top-quark pole mass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Sheng-Quan; Wu, Xing-Gang; Si, Zong-Guo

The Principle of Maximum Conformality (PMC) provides a systematic way to eliminate the renormalization scheme and renormalization scale uncertainties for high-energy processes. We have observed that by applying PMC scale setting, one obtains comprehensive and self-consistent pQCD predictions for the top-quark pair total cross section and the top-quark pair forward–backward asymmetry in agreement with the measurements at the Tevatron and LHC. As a step forward, in the present work, we determine the top-quark pole mass via a detailed comparison of the top-quark pair cross section with the measurements at the Tevatron and LHC. The results for the top-quark pole mass are m t=174.6more » $$+3.1\\atop{-3.2}$$ GeV for the Tevatron with $$\\sqrt{s}$$ =1.96 TeV, m t=173.7±1.5 and 174.2±1.7 GeV for the LHC with $$\\sqrt{s}$$ =7 and 8 TeV, respectively. Those predictions agree with the average, 173.34±0.76 GeV, obtained from various collaborations via direct measurements. The consistency of the pQCD predictions using the PMC with all of the collider measurements at different energies provides an important verification of QCD.« less

A precise determination of the top-quark pole mass

DOE PAGES

Wang, Sheng-Quan; Wu, Xing-Gang; Si, Zong-Guo; ...

2018-03-20

The Principle of Maximum Conformality (PMC) provides a systematic way to eliminate the renormalization scheme and renormalization scale uncertainties for high-energy processes. We have observed that by applying PMC scale setting, one obtains comprehensive and self-consistent pQCD predictions for the top-quark pair total cross section and the top-quark pair forward–backward asymmetry in agreement with the measurements at the Tevatron and LHC. As a step forward, in the present work, we determine the top-quark pole mass via a detailed comparison of the top-quark pair cross section with the measurements at the Tevatron and LHC. The results for the top-quark pole mass are m t=174.6more » $$+3.1\\atop{-3.2}$$ GeV for the Tevatron with $$\\sqrt{s}$$ =1.96 TeV, m t=173.7±1.5 and 174.2±1.7 GeV for the LHC with $$\\sqrt{s}$$ =7 and 8 TeV, respectively. Those predictions agree with the average, 173.34±0.76 GeV, obtained from various collaborations via direct measurements. The consistency of the pQCD predictions using the PMC with all of the collider measurements at different energies provides an important verification of QCD.« less

Tetraquark resonances computed with static lattice QCD potentials and scattering theory

NASA Astrophysics Data System (ADS)

Bicudo, Pedro; Cardoso, Marco; Peters, Antje; Pflaumer, Martin; Wagner, Marc

2018-03-01

We study tetraquark resonances with lattice QCD potentials computed for two static quarks and two dynamical quarks, the Born-Oppenheimer approximation and the emergent wave method of scattering theory. As a proof of concept we focus on systems with isospin I = 0, but consider different relative angular momenta l of the heavy b quarks. We compute the phase shifts and search for S and T matrix poles in the second Riemann sheet. We predict a new tetraquark resonance for l = 1, decaying into two B mesons, with quantum numbers I(JP) = 0(1-), mass m = 10576-4+4 MeV and decay width Γ = 112-103+90 MeV.

Electric Dipole Moment of the Neutron from 2+1 Flavor Lattice QCD.

PubMed

Guo, F-K; Horsley, R; Meissner, U-G; Nakamura, Y; Perlt, H; Rakow, P E L; Schierholz, G; Schiller, A; Zanotti, J M

2015-08-07

We compute the electric dipole moment d(n) of the neutron from a fully dynamical simulation of lattice QCD with 2+1 flavors of clover fermions and nonvanishing θ term. The latter is rotated into a pseudoscalar density in the fermionic action using the axial anomaly. To make the action real, the vacuum angle θ is taken to be purely imaginary. The physical value of dd(n) is obtained by analytic continuation. We find d(n)=-3.9(2)(9)×10(-16) θ  e cm, which, when combined with the experimental limit on d(n), leads to the upper bound |θ|≲7.4×10(-11).

Axion dark matter and the Lattice

NASA Astrophysics Data System (ADS)

Moore, Guy

2018-03-01

First I will review the QCD theta problem and the Peccei-Quinn solution, with its new particle, the axion. I will review the possibility of the axion as dark matter. If PQ symmetry was restored at some point in the hot early Universe, it should be possible to make a definite prediction for the axion mass if it constitutes the Dark Matter. I will describe progress on one issue needed to make this prediction - the dynamics of axionic string-wall networks and how they produce axions. Then I will discuss the sensitivity of the calculation to the high temperature QCD topological susceptibility. My emphasis is on what temperature range is important, and what level of precision is needed.

Lattice QCD and heavy ion collisions: a review of recent progress.

PubMed

Ratti, Claudia

2018-04-04

In the last few years, numerical simulations of QCD on the lattice have reached a new level of accuracy. A wide range of thermodynamic quantities is now available in the continuum limit and for physical quark masses. This allows a comparison with measurements from heavy ion collisions for the first time. Furthermore, calculations of dynamical quantities are also becoming available. The combined effort from first principles and experiment allows us to gain an unprecedented understanding of the properties of quark-gluon plasma. I will review the state-of-the-art results from lattice simulations and connect them to the experimental information from RHIC and the LHC. © 2018 IOP Publishing Ltd.

Unraveling strong dynamics with the fifth dimension

NASA Astrophysics Data System (ADS)

Batell, Brian Thomas

Theories with strong gauge dynamics, such as quantum chromodynamics and technicolor, have evaded analytic solutions despite more than thirty years of efforts on the part of elementary particle theorists. Holography refers to methods inspired by the AdS/CFT correspondence in string theory to understand gauge theories in the nonperturbative regime using extra dimensions. The studies presented in this thesis describe new applications of holography to models of electroweak symmetry breaking and quantum chromodynamics. The four-dimensional holographic description of the Randall-Sundrum model, or warped extra dimension, is a theory of electroweak symmetry breaking with strong gauge dynamics, similar to technicolor or composite Higgs theories. A new tool, the holographic basis, is presented that allows one to quantitatively characterize the mixing between the elementary and composite states in the holographic theory. An exploration of localized gauge fields in the Randall-Sundrum framework is detailed, focusing on both theoretical and phenomenological issues. The holographic dual interpretation of localized gauge bosons is also derived. Bottom-up holographic approaches to quantum chromodynamics, referred to as AdS/QCD, describe the observed properties of mesons reasonably well. In models with a soft infrared wall, Regge trajectories for high radial and spin states can also be obtained. A dynamical soft-wall AdS/QCD model is described, and the implications for top-down string constructions are discussed.

Current-current interactions, dynamical symmetry-breaking, and quantum chromodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neuenschwander, D.E. Jr.

1983-01-01

Quantum Chromodynamics with massive gluons (gluon mass triple bond xm/sub p/) in a contact-interaction limit called CQCD (strong coupling g..-->..infinity; x..-->..infinity), despite its non-renormalizability and lack of hope of confinement, is nevertheless interesting for at least two reasons. Some authors have suggested a relation between 4-Fermi and Yang-Mills theories. If g/x/sup 2/ much less than 1, then CQCD is not merely a 4-Fermi interaction, but includes 4,6,8 etc-Fermi non-Abelian contact interactions. With possibility of infrared slavery, perturbative evaluation of QCD in the infrared is a dubious practice. However, if g/sup 2//x/sup 2/ much less than 1 in CQCD, then themore » simplest 4-Fermi interaction is dominant, and CQCD admits perturbative treatment, but only in the infrared. With the dominant interaction, a dynamical Nambu-Goldstone realization of chiral symmetry-breaking (XSB) is found. Although in QCD the relation between confinement and XSB is controversial, XSB occurs in CQCD provided confinement is sacrificed.« less

Baryon bags in strong coupling QCD

NASA Astrophysics Data System (ADS)

Gattringer, Christof

2018-04-01

We discuss lattice QCD with one flavor of staggered fermions and show that in the path integral the baryon contributions can be fully separated from quark and diquark contributions. The baryonic degrees of freedom (d.o.f.) are independent of the gauge field, and the corresponding free fermion action describes the baryons through the joint propagation of three quarks. The nonbaryonic dynamics is described by quark and diquark terms that couple to the gauge field. When evaluating the quark and diquark contributions in the strong coupling limit, the partition function completely factorizes into baryon bags and a complementary domain. Baryon bags are regions in space-time where the dynamics is described by a single free fermion made out of three quarks propagating coherently as a baryon. Outside the baryon bags, the relevant d.o.f. are monomers and dimers for quarks and diquarks. The partition sum is a sum over all baryon bag configurations, and for each bag, a free fermion determinant appears as a weight factor.

Axions, Inflation and String Theory

NASA Astrophysics Data System (ADS)

Mack, Katherine J.; Steinhardt, P. J.

2009-01-01

The QCD axion is the leading contender to rid the standard model of the strong-CP problem. If the Peccei-Quinn symmetry breaking occurs before inflation, which is likely in string theory models, axions manifest themselves cosmologically as a form of cold dark matter with a density determined by the axion's initial conditions and by the energy scale of inflation. Constraints on the dark matter density and on the amplitude of CMB isocurvature perturbations currently demand an exponential degree of fine-tuning of both axion and inflationary parameters beyond what is required for particle physics. String theory models generally produce large numbers of axion-like fields; the prospect that any of these fields exist at scales close to that of the QCD axion makes the problem drastically worse. I will discuss the challenge of accommodating string-theoretic axions in standard inflationary cosmology and show that the fine-tuning problems cannot be fully addressed by anthropic principle arguments.

Supersymmetry across the light and heavy-light hadronic spectrum. II.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dosch, Hans Gunter; de Téramond, Guy F.; Brodsky, Stanley J.

We extend our analysis of the implications of hadronic supersymmetry for heavy-light hadrons in light-front holographic QCD. Although conformal symmetry is strongly broken by the heavy quark mass, supersymmetry and the holographic embedding of semiclassical light-front dynamics derived from five-dimensional anti-de Sitter space nevertheless determine the form of the confining potential in the light-front Hamiltonian to be harmonic. The resulting light-front bound-state equations lead to a heavy-light Regge-like spectrum for both mesons and baryons. The confinement hadron mass scale and their Regge slopes depend, however, on the mass of the heavy quark in the meson or baryon as expected frommore » heavy quark effective theory. Furthermore, this procedure reproduces the observed spectra of heavy-light hadrons with good precision and makes predictions for yet unobserved states.« less

Supersymmetry across the light and heavy-light hadronic spectrum. II.

DOE PAGES

Dosch, Hans Gunter; de Téramond, Guy F.; Brodsky, Stanley J.

2017-02-15

We extend our analysis of the implications of hadronic supersymmetry for heavy-light hadrons in light-front holographic QCD. Although conformal symmetry is strongly broken by the heavy quark mass, supersymmetry and the holographic embedding of semiclassical light-front dynamics derived from five-dimensional anti-de Sitter space nevertheless determine the form of the confining potential in the light-front Hamiltonian to be harmonic. The resulting light-front bound-state equations lead to a heavy-light Regge-like spectrum for both mesons and baryons. The confinement hadron mass scale and their Regge slopes depend, however, on the mass of the heavy quark in the meson or baryon as expected frommore » heavy quark effective theory. Furthermore, this procedure reproduces the observed spectra of heavy-light hadrons with good precision and makes predictions for yet unobserved states.« less

QCD corrections to massive color-octet vector boson pair production

NASA Astrophysics Data System (ADS)

Freitas, Ayres; Wiegand, Daniel

2017-09-01

This paper describes the calculation of the next-to-leading order (NLO) QCD corrections to massive color-octet vector boson pair production at hadron colliders. As a concrete framework, a two-site coloron model with an internal parity is chosen, which can be regarded as an effective low-energy approximation of Kaluza-Klein gluon physics in universal extra dimensions. The renormalization procedure involves several subtleties, which are discussed in detail. The impact of the NLO corrections is relatively modest, amounting to a reduction of 11-14% in the total cross-section, but they significantly reduce the scale dependence of the LO result.

Top Quark Pair Production in Association with a Jet with Next-to-Leading-Order QCD Off-Shell Effects at the Large Hadron Collider.

PubMed

Bevilacqua, G; Hartanto, H B; Kraus, M; Worek, M

2016-02-05

We present a complete description of top quark pair production in association with a jet in the dilepton channel. Our calculation is accurate to next-to-leading order (NLO) in QCD and includes all nonresonant diagrams, interferences, and off-shell effects of the top quark. Moreover, nonresonant and off-shell effects due to the finite W gauge boson width are taken into account. This calculation constitutes the first fully realistic NLO computation for top quark pair production with a final state jet in hadronic collisions. Numerical results for differential distributions as well as total cross sections are presented for the Large Hadron Collider at 8 TeV. With our inclusive cuts, NLO predictions reduce the unphysical scale dependence by more than a factor of 3 and lower the total rate by about 13% compared to leading-order QCD predictions. In addition, the size of the top quark off-shell effects is estimated to be below 2%.

Double-beta decay processes from lattice quantum chromodynamics

NASA Astrophysics Data System (ADS)

Davoudi, Zohreh; Tiburzi, Brian; Wagman, Michael; Winter, Frank; Chang, Emmanuel; Detmold, William; Orginos, Kostas; Savage, Martin; Shanahan, Phiala; Nplqcd Collaboration

2017-09-01

While an observation of neutrinoless double-beta decay in upcoming experiments will establish that the neutrinos are Majorana particles, the underlying new physics responsible for this decay can only be constrained if the theoretical predictions of the rate are substantially refined. This talk demonstrates the roadmap in connecting the underlying high-scale theory to the corresponding nuclear matrix elements, focusing mainly on the nucleonic matrix elements in the simplest extension of Standard Model in which a light Majorana neutrino is mediating the process. The role of lattice QCD and effective field theory in this program, in particular, the prospect of a direct matching of the nn to pp amplitude to lattice QCD will be discussed. As a first step towards this goal, the results of the first lattice QCD calculation of the relevant matrix element for neutrinofull double-beta decay will be presented, albeit with unphysical quark masses, along with important lessons that could impact the calculations of nuclear matrix elements involved in double-beta decays of realistic nuclei.

Studies of jet cross-sections and production properties with the ATLAS and CMS detectors

NASA Astrophysics Data System (ADS)

Anjos, Nuno

2016-07-01

Several characteristics of jet production in pp collisions have been measured by the ATLAS and CMS collaborations at the LHC. Measurements of event shapes and multi-jet production probe the dynamics of QCD in the soft regime and can constrain parton shower and hadronisation models. Measurements of multi-jet systems with a veto on additional jets probe QCD radiation effects. Double-differential cross-sections for threeand four-jet final states are measured at different centre-of-mass energies of pp collisions and are compared to expectations based on NLO QCD calculations. The distribution of the jet charge has been measured in di-jet events and compared to predictions from different hadronisation models and tunes. Jet-jet energy correlations are sensitive to the strong coupling constant. These measurements constitute precision tests of QCD in a new energy regime. Work supported by the Beatriu de Pinós program managed by Agència de Gestió d'Ajuts Universitaris i de Recerca with the support of the Secretaria d'Universitats i Recerca of the Departament d'Economia i Coneixement of the Generalitat de Catalunya, and the Cofund program of the Marie Curie Actions of the 7th R&D Framework Program of the European Union. Work partially supported by MINECO under grants SEV-2012-0234, FPA2013-48308, and FPA2012-38713, which include FEDER funds from the European Union.

Testing the Standard Model and Fundamental Symmetries in Nuclear Physics with Lattice QCD and Effective Field Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker-Loud, Andre

The research supported by this grant is aimed at probing the limits of the Standard Model through precision low-energy nuclear physics. The work of the PI (AWL) and additional personnel is to provide theory input needed for a number of potentially high-impact experiments, notably, hadronic parity violation, Dark Matter direct detection and searches for permanent electric dipole moments (EDMs) in nucleons and nuclei. In all these examples, a quantitative understanding of low-energy nuclear physics from the fundamental theory of strong interactions, Quantum Chromo-Dynamics (QCD), is necessary to interpret the experimental results. The main theoretical tools used and developed in thismore » work are the numerical solution to QCD known as lattice QCD (LQCD) and Effective Field Theory (EFT). This grant is supporting a new research program for the PI, and as such, needed to be developed from the ground up. Therefore, the first fiscal year of this grant, 08/01/2014-07/31/2015, has been spent predominantly establishing this new research effort. Very good progress has been made, although, at this time, there are not many publications to show for the effort. After one year, the PI accepted a job at Lawrence Berkeley National Laboratory, so this final report covers just a single year of five years of the grant.« less

Strong and Electroweak Matter 2004

NASA Astrophysics Data System (ADS)

Eskola, Kari J.; Kainulainen, Kimmo; Kajantie, Keijo; Rummukainen, Kari

RHIC experimental summary: the message from pp, d+Au and Au+Au collisions / M. Calderón de la Barca Sánchez -- Hydrodynamic aspects of relativistic heavy ion collisions at RHIC / P. F. Kolb -- Photon emission in a hot QCD plasma / P. Aurenche -- In search of the saturation scale: intrinsic features of the CGC / H. Weigert -- From leading hadron suppression to jet quenching at RHIC and LHC / U. A. Wiedemann -- Lattice simulations with chemical potential / C. Schmidt -- Mesonic correlators in hot QCD / M. Laine -- Thermalization and plasma instabilities / P. Arnold -- Transport coefficients in hot QCD / G. D. Moore -- Classical fields and heavy ion collisions / T. Lappi -- Progress in nonequilibrium quantum field theory II / J. Berges and J. Serreau -- A general effective theory for dense quark matter / P. T. Reuter, Q. Wang and D. H. Rischke -- Thermal leptogenesis / M. Plümacher -- Cold electroweak Baryogenesis / J. Smit -- Proton-nucleus collisions in the color glass condensate framework / J.-P. Blaizot, F. Gelis and R. Venugopalan -- From classical to quantum saturation in the nuclear wavefunction / D. N. Triantafyllopoulos -- Charge correlations in heavy ion collisions / A. Rajantie -- Whitening of the quark-gluon plasma / S. Mrówczyński -- Progress in anisotropic plasma physics / P. Romatschke and M. Strickland -- Deconfinement and chiral symmetry: competing orders / K. Tuominen -- Relation between the chiral and deconfinement phase transitions / Y. Hatta -- Renormalized Polyakov loops, matrix models and the Gross-Witten point / A. Dumitru and J. T. Lenaghan -- The nature of the soft excitation at the critical end point of QCD / A. Jakovác ... [et al.] -- Thermodynamics of the 1+1-dimensional nonlinear sigma model through next-to-leading order in 1/N / H. J. Warringa -- Light quark meson correlations at high temperature / E. Laemann ... [et al.] -- Charmonia at finite momenta in a deconfined plasma / S. Datta ... [et al.] -- QCD thermodynamics: lattice results confront models / M. D'Elia and M. P. Lombardo -- Singlet free energies of a static quark-antiquark pair / K. Petrov -- Contributions to transport theory from multi-particle interactions and production processes / M. E. Carrington -- Transport coefficients and the 2PI effective action in the large N limit / G. Aarts and J. M. Martinez Resco -- Thermal features far from equilibrium: prethermalization / S. Borsányi -- QCD phase diagram at small Baryon densities from imaginary [symbol]: status report / O. Philipsen and Ph. de Forcrand -- Two loop renormalisation of the magnetic coupling in hot QCD and spatial Wilson loop / P. Giovannangeli -- Thermodynamics of deconfined QCD at small and large chemical potential / A. Ipp -- Evading the infrared problem of thermal QCD / Y. Schroder -- Chiral mesons in hot matter / A. Gómez Nicola, F. J. Llanes-Estrada and J. R. Peláez -- Thermal production of axinos in the early universe / A. Brandenburg and F. D. Steffen -- The 2-PI-1/N approximation applied to tachyonic preheating / A. Tranberg, A. Arrizabalaga and J. Smit -- Nonequilibrium dynamics in scalar hybrid models / J. Baacke and A. Heinen -- Photon mass in inflation and nearly minimal magnetogenesis / T. Prokopec -- Transport equations for chiral fermions to order [symbol] and electroweak Baryogenesis / S. Weinstock, M. G. Schmidt and T. Prokopec -- The gapless 2SC phase / M. Huang and I. A. Shovkovy -- Gapless CFL and its competition with mixed phases / M. Alford, C. Kouvaris and K. Rajagopal -- Transport coefficients in color superconducting quark matter / C. Manuel -- Renormalization and resummation in finite temperature field theories / A. Jakovác and Zs. Szép -- Renormalization and gauge symmetry for 2PI effective actions / U. Reinosa -- Out-of-equilibrium massless Schwinger model / R. F. Alvarez-Estrada -- Selfconsistent calculations of hadrons at finite temperature / C. Beckmann -- Fermion production in classical fields / D. D. Dietrich -- Numerical study of the equation of state for two flavor QCD at non-zero Baryon density / S. Ejiri ... [et al.] -- Phase conversion after a chiral transition: effects from inhomogeneities and finite size / E. S. Fraga -- Coherent Baryogenesis and nonthermal leptogenesis: a comparison / B. Garbrecht, T. Prokopec and M. G. Schmidt -- Two aspects of color superconductivity: gauge independence and neutrality / A. Gerhold -- QCD phase diagram in nonlocal chiral quark models / D. Gómez Dumm -- QCD equation of state and dark matter / M. Hindmarsh and O. Philipsen -- Analytical approach to SU(2) Yang-Mills thermodynamics / R. Hofmann -- Free energies of static three quark systems / K. Hübner ... [et al.] -- Color ferromagnetic state of dense quark matter / A. Iwazaki -- Axial currents from CKM matrix CP violation and electroweak Baryogenesis / T. Konstandin -- Dilute monopole gas, and K-tensions in gluodynamics / C. P. Korthals Altes and P. Giovannangeli -- Infrared QCD and the renormalisation group / D. F. Litim ... [et al.] -- Residual confinement in high-temperature Yang-Mills theory / A. Maas ... [et al.] -- Scalar O(N) model at finite temperature - 2PI effective potential in different approximations / J. Baacke and S. Michalski -- Cutoff effects in meson spectral functions / T. Blum and P. Petreczky -- Anomalous specific heat in ultradegenerate QED and QCD / A. Gerhold, A. Ipp and A. Rebhan -- Color-superconducting phases in cold and dense quark matter / A. Schmitt -- Non fermi liquid effects in dense matter and compact star cooling / K. Schwenzer and T. Schäfer -- Prethermalisation and the build-up of the Higgs effect / D. Sexty and A. Patkós -- Vector meson at non-zero Baryon density and zero sound / S. J. Hands and C. G. Strouthos -- Impact of Baryon resonances on the chiral phase transition / D. Zschiesche ... [et al.].

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alioli, Simone; Farina, Marco; Pappadopulo, Duccio

New physics, that is too heavy to be produced directly, can leave measurable imprints on the tails of kinematic distributions at the LHC.We use energetic QCD processes to perform novel measurements of the Standard Model (SM) Effective Field Theory. We show that the dijet invariant mass spectrum, and the inclusive jet transverse momentum spectrum, are sensitive to a dimension 6 operator that modifies the gluon propagator at high energies. The dominant effect is constructive or destructive interference with SM jet production. Here, we compare differential next-to-leading order predictions from POWHEG to public 7TeV jet data, including scale, PDF, and experimentalmore » uncertainties and their respective correlations. Furthermore, we constrain a New Physics (NP) scale of 3.5TeV with current data. We project the reach of future 13 and 100TeV measurements, which we estimate to be sensitive to NP scales of 8 and 60TeV, respectively. As an application, we apply our bounds to constrain heavy vector octet colorons that couple to the QCD current. We conclude that effective operators will surpass bump hunts, in terms of coloron mass reach, even for sequential couplings.« less

Predictions for the top-quark forward-backward asymmetry at high invariant pair mass using the principle of maximum conformality

DOE PAGES

Wang, Sheng -Quan; Wu, Xing -Gang; Si, Zong -Guo; ...

2016-01-07

In this study, the D0 collaboration at FermiLab has recently measured the top-quark pair forward-backward asymmetry inmore » $$\\bar{p}p$$ → $$t\\bar{t}$$X reactions as a function of the $$t\\bar{t}$$ invariant mass M $$t\\bar{t}$$. The D0 result for A FB(M $$t\\bar{t}$$ > 650 GeV) is smaller than A FB(M $$t\\bar{t}$$) obtained for small values of M $$t\\bar{t}$$, which may indicate an “increasing-decreasing” behavior for A FB(M $$t\\bar{t}$$ > M cut). This behavior is not explained using conventional renormalization scale setting, or even by a next-to-next-to-leading order (N 2LO) QCD calculation—one predicts a monotonically increasing behavior. In the conventional scale-setting method, one simply guesses a single renormalization scale μr for the argument of the QCD running coupling and then varies it over an arbitrary range. However, the conventional method has inherent difficulties.« less

Relaxion: A landscape without anthropics

NASA Astrophysics Data System (ADS)

Nelson, Ann; Prescod-Weinstein, Chanda

2017-12-01

The relaxion mechanism provides a potentially elegant solution to the hierarchy problem without resorting to anthropic or other fine-tuning arguments. This mechanism introduces an axion-like field, dubbed the relaxion, whose expectation value determines the electroweak hierarchy as well as the QCD strong C P -violating θ ¯ parameter. During an inflationary period, the Higgs mass squared is selected to be negative and hierarchically small in a theory which is consistent with 't Hooft's technical naturalness criteria. However, in the original model proposed by Graham, Kaplan, and Rajendran [Phys. Rev. Lett. 115, 221801 (2015), 10.1103/PhysRevLett.115.221801], the relaxion does not solve the strong C P problem, and in fact contributes to it, as the coupling of the relaxion to the Higgs field and the introduction of a linear potential for the relaxion produces large strong C P violation. We resolve this tension by considering inflation with a Hubble scale which is above the QCD scale but below the weak scale, and estimating the Hubble temperature dependence of the axion mass. The relaxion potential is thus very different during inflation than it is today. We find that provided the inflationary Hubble scale is between the weak scale and about 3 GeV, the relaxion resolves the hierarchy, strong C P , and dark matter problems in a way that is technically natural.

Flavour symmetry breaking in the kaon parton distribution amplitude

DOE PAGES

none,

2014-11-01

We compute the kaon's valence-quark (twist-two parton) distribution amplitude (PDA) by projecting its Poincaré-covariant Bethe–Salpeter wave-function onto the light-front. At a scale ζ = 2 GeV, the PDA is a broad, concave and asymmetric function, whose peak is shifted 12–16% away from its position in QCD's conformal limit. These features are a clear expression of SU(3)-flavour-symmetry breaking. They show that the heavier quark in the kaon carries more of the bound-state's momentum than the lighter quark and also that emergent phenomena in QCD modulate the magnitude of flavour-symmetry breaking: it is markedly smaller than one might expect based on themore » difference between light-quark current masses. Our results add to a body of evidence which indicates that at any energy scale accessible with existing or foreseeable facilities, a reliable guide to the interpretation of experiment requires the use of such nonperturbatively broadened PDAs in leading-order, leading-twist formulae for hard exclusive processes instead of the asymptotic PDA associated with QCD's conformal limit. We illustrate this via the ratio of kaon and pion electromagnetic form factors: using our nonperturbative PDAs in the appropriate formulae, F K/F π=1.23 at spacelike-Q 2=17 GeV 2, which compares satisfactorily with the value of 0.92(5) inferred in e +e - annihilation at s=17 GeV 2.« less

Hadronic decays of B →a1(1260 )b1(1235 ) in the perturbative QCD approach

NASA Astrophysics Data System (ADS)

Jing, Hao-Yang; Liu, Xin; Xiao, Zhen-Jun

2017-12-01

We calculate the branching ratios and polarization fractions of the B →a1b1 decays in the perturbative QCD(pQCD) approach at leading order, where a1(b1) stands for the axial-vector a1(1260 )[b1(1235 )] state. By combining the phenomenological analyses with the perturbative calculations, we find the following results: (a) the large decay rates around 10-5 to 10-6 of the B →a1b1 decays dominated by the longitudinal polarization(except for the B+→b1+a10 mode) are predicted and basically consistent with those in the QCD factorization(QCDF) within errors, which are expected to be tested by the Large Hadron Collider and Belle-II experiments. The large B0→a10b10 branching ratio could provide hints to help explore the mechanism of the color-suppressed decays. (b) the rather different QCD behaviors between the a1 and b1 mesons result in the destructive(constructive) contributions in the nonfactorizable spectator diagrams with a1(b1) emission. Therefore, an interesting pattern of the branching ratios appears for the color-suppressed B0→a10a10,a10b10, and b10b10 modes in the pQCD approach, BR (B0→b10b10)>BR (B0→a10b10)≳BR (B0→a10a10), which is different from BR (B0→b10b10)˜BR (B0→a10b10)≳BR (B0→a10a10) in the QCDF and would be verified at future experiments. (c) the large naive factorization breaking effects are observed in these B →a1b1 decays. Specifically, the large nonfactorizable spectator(weak annihilation) amplitudes contribute to the B0→b1+a1-(B+→a1+b10andB+→b1+a10) mode(s), which demand confirmations via the precise measurements. Furthermore, the different phenomenologies shown among B →a1b1, B →a1a1, and B →b1b1 decays are also expected to be tested stringently, which could shed light on the typical QCD dynamics involved in these modes, even further distinguish those two popular pQCD and QCDF approaches.

Transverse spin structure of the nucleon from lattice-QCD simulations.

PubMed

Göckeler, M; Hägler, Ph; Horsley, R; Nakamura, Y; Pleiter, D; Rakow, P E L; Schäfer, A; Schierholz, G; Stüben, H; Zanotti, J M

2007-06-01

We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72, 094020 (2005)], we predict that the Boer-Mulders function h(1/1), describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks.

Onset transition to cold nuclear matter from lattice QCD with heavy quarks.

PubMed

Fromm, M; Langelage, J; Lottini, S; Neuman, M; Philipsen, O

2013-03-22

Lattice QCD at finite density suffers from a severe sign problem, which has so far prohibited simulations of the cold and dense regime. Here we study the onset of nuclear matter employing a three-dimensional effective theory derived by combined strong coupling and hopping expansions, which is valid for heavy but dynamical quarks and has a mild sign problem only. Its numerical evaluations agree between a standard Metropolis and complex Langevin algorithm, where the latter is free of the sign problem. Our continuum extrapolated data approach a first order phase transition at μ(B) ≈ m(B) as the temperature approaches zero. An excellent description of the data is achieved by an analytic solution in the strong coupling limit.

Physics with charmonium - Highlights of BESIII and PANDA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messchendorp, Johan

2014-11-11

The physics of the strong interaction is undoubtedly one of the most challenging areas of modern science. Quantum ChromoDynamics (QCD) is reproducing successfully the physics phenomena at distances much shorter than the size of the nucleon, where perturbation theory can be used yielding results of high precision and predictive power. At larger distance scales, however, perturbative methods cannot be applied anymore, although spectacular phenomena, such as the generation of hadron masses and quark confinement, occur. Studies using charmed quarks and gluon-rich matter have the potential to connect the perturbative and the non-perturbative QCD region. The annihilation of matter with antimattermore » in the mass regime of charmonium is an ideal environment to discover new states or transitions that could reveal the secrets of the strong interaction. Hadronic and electromagnetic transitions between charmonium states and their decays have been measured with a world-record in precision with the BESIII spectrometer at the electron-positron collider at IHEP Beijing, China. Moreover, unconventional narrow charmonium-rich states have been discovered recently in an energy regime above the open-charm threshold, thereby, possibly initiating a new era in charmonium spectroscopy. The near future experiment, PANDA, at the research facility FAIR in Germany, Darmstadt, will exploit the annihilation of cooled anti-protons with protons to perform charmonium spectroscopy with an incredible precision. I will present the most promising results that have been recently obtained with BESIII together with the future perspectives of PANDA in the field of charmonium spectroscopy.« less

Physics with charmonium - Highlights of BESIII and PANDA

NASA Astrophysics Data System (ADS)

Messchendorp, Johan

2014-11-01

The physics of the strong interaction is undoubtedly one of the most challenging areas of modern science. Quantum ChromoDynamics (QCD) is reproducing successfully the physics phenomena at distances much shorter than the size of the nucleon, where perturbation theory can be used yielding results of high precision and predictive power. At larger distance scales, however, perturbative methods cannot be applied anymore, although spectacular phenomena, such as the generation of hadron masses and quark confinement, occur. Studies using charmed quarks and gluon-rich matter have the potential to connect the perturbative and the non-perturbative QCD region. The annihilation of matter with antimatter in the mass regime of charmonium is an ideal environment to discover new states or transitions that could reveal the secrets of the strong interaction. Hadronic and electromagnetic transitions between charmonium states and their decays have been measured with a world-record in precision with the BESIII spectrometer at the electron-positron collider at IHEP Beijing, China. Moreover, unconventional narrow charmonium-rich states have been discovered recently in an energy regime above the open-charm threshold, thereby, possibly initiating a new era in charmonium spectroscopy. The near future experiment, PANDA, at the research facility FAIR in Germany, Darmstadt, will exploit the annihilation of cooled anti-protons with protons to perform charmonium spectroscopy with an incredible precision. I will present the most promising results that have been recently obtained with BESIII together with the future perspectives of PANDA in the field of charmonium spectroscopy.

The cosmic QCD phase transition with dense matter and its gravitational waves from holography

NASA Astrophysics Data System (ADS)

Ahmadvand, M.; Bitaghsir Fadafan, K.

2018-04-01

Consistent with cosmological constraints, there are scenarios with the large lepton asymmetry which can lead to the finite baryochemical potential at the cosmic QCD phase transition scale. In this paper, we investigate this possibility in the holographic models. Using the holographic renormalization method, we find the first order Hawking-Page phase transition, between the Reissner-Nordström AdS black hole and thermal charged AdS space, corresponding to the de/confinement phase transition. We obtain the gravitational wave spectra generated during the evolution of bubbles for a range of the bubble wall velocity and examine the reliability of the scenarios and consequent calculations by gravitational wave experiments.

QCD matter thermalization at the RHIC and the LHC

NASA Astrophysics Data System (ADS)

Xu, Zhe; Cheng, Luan; El, Andrej; Gallmeister, Kai; Greiner, Carsten

2009-06-01

Employing the perturbative QCD inspired parton cascade, we investigate kinetic and chemical equilibration of the partonic matter created in central heavy ion collisions at RHIC and LHC energies. Two types of initial conditions are chosen. One is generated by the model of wounded nucleons using the PYTHIA event generator and Glauber geometry. Another is considered as a color glass condensate. We show that kinetic equilibration is almost independent of the chosen initial conditions, whereas there is a sensitive dependence for chemical equilibration. The time scale of thermalization lies between 1 and 1.5 fm/c. The final parton transverse energy obtained from BAMPS calculations is compared with the RHIC data and is estimated for the LHC energy.

Higgs Boson Production in Association with a Jet at Next-to-Next-to-Leading Order.

PubMed

Boughezal, Radja; Caola, Fabrizio; Melnikov, Kirill; Petriello, Frank; Schulze, Markus

2015-08-21

We present precise predictions for Higgs boson production in association with a jet. We work in the Higgs effective field theory framework and compute next-to-next-to-leading order QCD corrections to the gluon-gluon and quark-gluon channels, which is sufficient for reliable LHC phenomenology. We present fully differential results as well as total cross sections for the LHC. Our next-to-next-to-leading order predictions reduce the unphysical scale dependence by more than a factor of 2 and enhance the total rate by about twenty percent compared to next-to-leading order QCD predictions. Our results demonstrate for the first time satisfactory convergence of the perturbative series.

Probing collective effects in hadronisation with the extremes of the underlying event

NASA Astrophysics Data System (ADS)

Martin, T.; Skands, P.; Farrington, S.

2016-05-01

We define a new set of observables to probe the structure of the underlying event in hadron collisions. We use the conventional definition of the "transverse region" in jet events and, for a fixed window in jet p_perp , propose to measure several discriminating quantities as a function of the level of activity in the transverse region. The measurement of these observables in LHC data would reveal whether, e.g., the properties of "low-UE" events are compatible with equivalent measurements in e^+e^- collisions (jet universality), and whether the scaling behaviour towards "high-UE" events exhibits properties of non-trivial soft-QCD dynamics, such as colour reconnections or other collective phenomena. We illustrate at √{s} = 13 {TeV} that significant discriminatory power is obtained in comparisons between MC models with varying treatments of collective effects, including Pythia 8, epos, and Dipsy.

Lattice QCD inputs to the CKM unitarity triangle analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laiho, Jack; Department of Physics and Astronomy, University of Glasgow, Glasgow, G128 QQ; Lunghi, E.

2010-02-01

We perform a global fit to the Cabibbo-Kobayashi-Maskawa unitarity triangle using the latest experimental and theoretical constraints. Our emphasis is on the hadronic weak matrix elements that enter the analysis, which must be computed using lattice QCD or other nonperturbative methods. Realistic lattice QCD calculations which include the effects of the dynamical up, down, and strange quarks are now available for all of the standard inputs to the global fit. We therefore present lattice averages for all of the necessary hadronic weak matrix elements. We attempt to account for correlations between lattice QCD results in a reasonable but conservative manner:more » whenever there are reasons to believe that an error is correlated between two lattice calculations, we take the degree of correlation to be 100%. These averages are suitable for use as inputs both in the global Cabibbo-Kobayashi-Maskawa unitarity triangle fit and other phenomenological analyses. In order to illustrate the impact of the lattice averages, we make standard model predictions for the parameters B-circumflex{sub K}, |V{sub cb}|, and |V{sub ub}|/|V{sub cb}|. We find a (2-3){sigma} tension in the unitarity triangle, depending upon whether we use the inclusive or exclusive determination of |V{sub cb}|. If we interpret the tension as a sign of new physics in either neutral kaon or B mixing, we find that the scenario with new physics in kaon mixing is preferred by present data.« less

Lattice QCD Inputs to the CKM Unitarity Triangle Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van de Water, R.; Lunghi, E; Laiho, J

2010-02-02

We perform a global fit to the Cabibbo-Kobayashi-Maskawa unitarity triangle using the latest experimental and theoretical constraints. Our emphasis is on the hadronic weak matrix elements that enter the analysis, which must be computed using lattice QCD or other nonperturbative methods. Realistic lattice QCD calculations which include the effects of the dynamical up, down, and strange quarks are now available for all of the standard inputs to the global fit. We therefore present lattice averages for all of the necessary hadronic weak matrix elements. We attempt to account for correlations between lattice QCD results in a reasonable but conservative manner:more » whenever there are reasons to believe that an error is correlated between two lattice calculations, we take the degree of correlation to be 100%. These averages are suitable for use as inputs both in the global Cabibbo-Kobayashi-Maskawa unitarity triangle fit and other phenomenological analyses. In order to illustrate the impact of the lattice averages, we make standard model predictions for the parameters B{sub K}, |V{sub cb}|, and |V{sub ub}|/|Vcb|. We find a (2-3){sigma} tension in the unitarity triangle, depending upon whether we use the inclusive or exclusive determination of |V{sub cb}|. If we interpret the tension as a sign of new physics in either neutral kaon or B mixing, we find that the scenario with new physics in kaon mixing is preferred by present data.« less

RG flows and bifurcations

DOE PAGES

Gukov, Sergei

2017-03-29

Interpreting RG flows as dynamical systems in the space of couplings we produce a variety of constraints, global (topological) as well as local. These constraints, in turn, rule out some of the proposed RG flows and also predict new phases and fixed points, surprisingly, even in familiar theories such as model, QED3, or QCD4.

Topological susceptibility of QCD with dynamical Möbius domain-wall fermions

NASA Astrophysics Data System (ADS)

Aoki, S.; Cossu, G.; Fukaya, H.; Hashimoto, S.; Kaneko, T.

2018-04-01

We compute the topological susceptibility χ_t of lattice QCD with 2+1 dynamical quark flavors described by the Möbius domain-wall fermion. Violation of chiral symmetry as measured by the residual mass is kept at ˜1 MeV or smaller. We measure the fluctuation of the topological charge density in a "slab" sub-volume of the simulated lattice using the method proposed by W. Bietenholz, P. de Forcrand, and U. Gerber, J. High Energy Phys. 12, 070 (2015) and W. Bietenholz, K. Cichy, P. de Forcrand, A. Dromard, and U. Gerber, PoS LATTICE 2016, 321 (2016). The quark mass dependence of χ_t is consistent with the prediction of chiral perturbation theory, from which the chiral condensate is extracted as Σ^{\\overlineMS}(2 GeV) = [274(13)(29) MeV]^3, where the first error is statistical and the second one is systematic. Combining the results for the pion mass M_π and decay constant F_π, we obtain χ_t = 0.229(03)(13)M_π^2F_π^2 at the physical point.

Axial charges of N(1535) and N(1650) in lattice QCD with two flavors of dynamical quarks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takahashi, Toru T.; Kunihiro, Teiji

2008-07-01

We show the first lattice QCD results on the axial charge g{sub A}{sup N}*{sup N}* of N*(1535) and N*(1650). The measurements are performed with two flavors of dynamical quarks employing the renormalization-group improved gauge action at {beta}=1.95 and the mean-field improved clover quark action with the hopping parameters, {kappa}=0.1375, 0.1390, and 0.1400. In order to properly separate signals of N*(1535) and N*(1650), we construct 2x2 correlation matrices and diagonalize them. Wraparound contributions in the correlator, which can be another source of signal contaminations, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axialmore » charge of N*(1535) takes small values such as g{sub A}{sup N}*{sup N}*{approx}O(0.1), whereas that of N*(1650) is about 0.5, which is found independent of quark masses and consistent with the predictions by the naive nonrelativistic quark model.« less

Minimally doubled fermions and spontaneous chiral symmetry breaking

NASA Astrophysics Data System (ADS)

Osmanaj (Zeqirllari), Rudina; Hyka (Xhako), Dafina

2018-03-01

Chiral symmetry breaking in massless QCD is a very important feature in the current understanding of low energy physics. Low - lying Dirac modes are suitable to help us understand the spontaneous chiral symmetry breaking, since the formation of a non zero chiral condensate is an effect of their accumulation near zero. The Banks - Casher relation links the spectral density of the Dirac operator to the condensate with an identity that can be read in both directions. In this work we propose a spectral method to achieve a reliable determination of the density of eigenvalues of Dirac operator near zero using the Gauss - Lanczos quadrature. In order to understand better the dynamical chiral symmetry breaking and use the method we propose, we have chosen to work with minimally doubled fermions. These kind of fermions have been proposed as a strictly local discretization of the QCD fermions action, which preserves chiral symmetry at finite cut-off. Being chiral fermions, is easier to work with them and their low - lying Dirac modes and to understand the dynamical spontaneous chiral symmetry breaking.

Lattice QCD in rotating frames.

PubMed

Yamamoto, Arata; Hirono, Yuji

2013-08-23

We formulate lattice QCD in rotating frames to study the physics of QCD matter under rotation. We construct the lattice QCD action with the rotational metric and apply it to the Monte Carlo simulation. As the first application, we calculate the angular momenta of gluons and quarks in the rotating QCD vacuum. This new framework is useful to analyze various rotation-related phenomena in QCD.

Fuzzy Dark Matter from Infrared Confining Dynamics

NASA Astrophysics Data System (ADS)

Davoudiasl, Hooman; Murphy, Christopher W.

2017-04-01

A very light boson of mass O (10-22) eV may potentially be a viable dark matter (DM) candidate, which can avoid phenomenological problems associated with cold DM. Such "fuzzy DM (FDM)" may naturally be an axion with a decay constant fa˜1 016- 1 018 GeV and a mass ma˜μ2/fa with μ ˜1 02 eV . Here, we propose a concrete model, where μ arises as a dynamical scale from infrared confining dynamics, analogous to QCD. Our model is an alternative to the usual approach of generating μ through string theoretic instanton effects. We outline the features of this scenario that result from various cosmological constraints. We find that those constraints are suggestive of a period of mild of inflation, perhaps from a strong first order phase transition, that reheats the standard model (SM) sector only. A typical prediction of our scenario, broadly speaking, is a larger effective number of neutrinos compared to the SM value Neff≈3 , as inferred from precision measurements of the cosmic microwave background. Some of the new degrees of freedom may be identified as "sterile neutrinos," which may be required to explain certain neutrino oscillation anomalies. Hence, aspects of our scenario could be testable in terrestrial experiments, which is a novelty of our FDM model.

Measurement of D ∗ meson cross sections at HERA and determination of the gluon density in the proton using NLO QCD

NASA Astrophysics Data System (ADS)

Adloff, C.; Anderson, M.; Andreev, V.; Andrieu, B.; Arkadov, V.; Arndt, C.; Ayyaz, I.; Babaev, A.; Bähr, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Bate, P.; Beck, M.; Beglarian, A.; Behnke, O.; Behrend, H.-J.; Beier, C.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bertrand-Coremans, G.; Biddulph, P.; Bizot, J. C.; Boudry, V.; Braunschweig, W.; Brisson, V.; Brown, D. P.; Brückner, W.; Bruel, P.; Bruncko, D.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burrage, A.; Buschhorn, G.; Calvet, D.; Campbell, A. J.; Carli, T.; Chabert, E.; Charlet, M.; Clarke, D.; Clerbaux, B.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Cousinou, M.-C.; Cox, B. E.; Cozzika, G.; Cvach, J.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davidsson, M.; De Roeck, A.; De Wolf, E. A.; Delcourt, B.; Demirchyan, R.; Diaconu, C.; Dirkmann, M.; Dixon, P.; Dlugosz, W.; Donovan, K. T.; Dowell, J. D.; Droutskoi, A.; Ebert, J.; Eckerlin, G.; Eckstein, D.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Elsen, E.; Enzenberger, M.; Erdmann, M.; Fahr, A. B.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Fleischer, M.; Flügge, G.; Fomenko, A.; Formánek, J.; Foster, J. M.; Franke, G.; Gabathuler, E.; Gabathuler, K.; Gaede, F.; Garvey, J.; Gassner, J.; Gayler, J.; Gerhards, R.; Ghazaryan, S.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Gorelov, I.; Grab, C.; Grässler, H.; Greenshaw, T.; Griffiths, R. K.; Grindhammer, G.; Hadig, T.; Haidt, D.; Hajduk, L.; Haller, T.; Hampel, M.; Haustein, V.; Haynes, W. J.; Heinemann, B.; Heinzelmann, G.; Henderson, R. C. W.; Hengstmann, S.; Henschel, H.; Heremans, R.; Herynek, I.; Hewitt, K.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoffmann, D.; Horisberger, R.; Hurling, S.; Ibbotson, M.; İşsever, Ç.; Jacquet, M.; Jaffre, M.; Jansen, D. M.; Jönsson, L.; Johnson, D. P.; Jones, M.; Jung, H.; Kästli, H. K.; Kander, M.; Kant, D.; Kapichine, M.; Karlsson, M.; Karschnik, O.; Katzy, J.; Kaufmann, O.; Kausch, M.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhne, J. H.; Kolanoski, H.; Kolya, S. D.; Korbel, V.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, K.; Küpper, A.; Küster, H.; Kuhlen, M.; Kurča, T.; Lahmann, R.; Landon, M. P. J.; Lange, W.; Langenegger, U.; Lebedev, A.; Lehner, F.; Lemaitre, V.; Lendermann, V.; Levonian, S.; Lindstroem, M.; List, B.; Lobo, G.; Lobodzinska, E.; Lubimov, V.; Lüders, S.; Lüke, D.; Lytkin, L.; Magnussen, N.; Mahlke-Krüger, H.; Malinovski, E.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martin, G.; Martyn, H.-U.; Martyniak, J.; Maxfield, S. J.; McMahon, T. R.; Mehta, A.; Meier, K.; Merkel, P.; Metlica, F.; Meyer, A.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Mikocki, S.; Milstead, D.; Moeck, J.; Mohr, R.; Mohrdieck, S.; Moreau, F.; Morris, J. V.; Müller, D.; Müller, K.; Murin, P.; Nagovizin, V.; Naroska, B.; Naumann, Th.; Négri, I.; Newman, P. R.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Niggli, H.; Nikitin, D.; Nix, O.; Nowak, G.; Nunnemann, T.; Oberlack, H.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panassik, V.; Pascaud, C.; Passaggio, S.; Patel, G. D.; Pawletta, H.; Perez, E.; Phillips, J. P.; Pieuchot, A.; Pitzl, D.; Pöschl, R.; Pope, G.; Povh, B.; Rabbertz, K.; Rauschenberger, J.; Reimer, P.; Reisert, B.; Reyna, D.; Rick, H.; Riess, S.; Rizvi, E.; Robmann, P.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rusakov, S.; Rybicki, K.; Sankey, D. P. C.; Schacht, P.; Scheins, J.; Schilling, F.-P.; Schleif, S.; Schleper, P.; Schmidt, D.; Schmidt, D.; Schoeffel, L.; Schröder, V.; Schultz-Coulon, H.-C.; Schwab, B.; Sefkow, F.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Sirois, Y.; Sloan, T.; Smirnov, P.; Smith, M.; Solochenko, V.; Soloviev, Y.; Spaskov, V.; Specka, A.; Spiekermann, J.; Spitzer, H.; Squinabol, F.; Steffen, P.; Steinberg, R.; Steinhart, J.; Stella, B.; Stellberger, A.; Stiewe, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Swart, M.; Tapprogge, S.; Taševský, M.; Tchernshov, V.; Tchetchelnitski, S.; Theissen, J.; Thompson, G.; Thompson, P. D.; Tobien, N.; Todenhagen, R.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Tzamariudaki, E.; Udluft, S.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Van Esch, P.; Van Haecke, A.; Van Mechelen, P.; Vazdik, Y.; Villet, G.; Wacker, K.; Wallny, R.; Walter, T.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; West, L. R.; Wiesand, S.; Wilksen, T.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wittmann, E.; Wobisch, M.; Wollatz, H.; Wünsch, E.; Žaček, J.; Zálešak, J.; Zhang, Z.; Zhokin, A.; Zini, P.; Zomer, F.; Zsembery, J.; zurNedden, M.; H1 Collaboration

1999-04-01

With the H1 detector at the ep collider HERA, D ∗ meson production cross sections have been measured in deep inelastic scattering with four-momentum transfers Q2 > 3 GeV 2 and in photoproduction at energies around Wγp ≈ 88 GeV and 194 GeV. Next-to-Leading Order QCD calculations are found to describe the differential cross sections within theoretical and experimental uncertainties. Using these calculations, the NLO gluon momentum distribution in the proton, xgg( xg), has been extracted in the momentum fraction range 7.5 × 10 -4 < xg < 4 × 10 -2 at average scales μ2 = 25 to 50 GeV 2. The gluon momentum fraction xg has been obtained from the measured kinematics of the scattered electron and the D ∗ meson in the final state. The results compare well with the gluon distribution obtained from the analysis of scaling violations of the proton structure function F2.

Mesons in strong magnetic fields: (I) General analyses

DOE PAGES

Hattori, Koichi; Kojo, Toru; Su, Nan

2016-03-21

Here, we study properties of neutral and charged mesons in strong magnetic fields |eB| >> Λ 2 QCD with Λ QCD being the QCD renormalization scale. Assuming long-range interactions, we examine magnetic-field dependences of various quantities such as the constituent quark mass, chiral condensate, meson spectra, and meson wavefunctions by analyzing the Schwinger–Dyson and Bethe–Salpeter equations. Based on the density of states obtained from these analyses, we extend the hadron resonance gas (HRG) model to investigate thermodynamics at large B. As B increases the meson energy behaves as a slowly growing function of the meson's transverse momenta, and thus amore » large number of meson states is accommodated in the low energy domain; the density of states at low temperature is proportional to B 2. This extended transverse phase space in the infrared regime significantly enhances the HRG pressure at finite temperature, so that the system reaches the percolation or chiral restoration regime at lower temperature compared to the case without a magnetic field; this simple picture would offer a gauge invariant and intuitive explanation of the inverse magnetic catalysis.« less

Tetraquarks in holographic QCD

NASA Astrophysics Data System (ADS)

Gutsche, Thomas; Lyubovitskij, Valery E.; Schmidt, Ivan

2017-08-01

Using a soft-wall AdS/QCD approach we derive the Schrödinger-type equation of motion for the tetraquark wave function, which is dual to the dimension-4 AdS bulk profile. The latter coincides with the number of constituents in the leading Fock state of the tetraquark. The obtained equation of motion is solved analytically, providing predictions for both the tetraquark wave function and its mass. A low mass limit for possible tetraquark states is given by M ≥2 κ =1 GeV , where κ =0.5 GeV is the typical value of the scale parameter in soft-wall AdS/QCD. We confirm results of the COMPASS Collaboration recently reported on the discovery of the a1(1414 ) state, interpreted as a tetraquark state composed of light quarks and having JP C=1++. Our prediction for the mass of this state, Ma1=√{2 } GeV ≃1.414 GeV , is in good agreement with the COMPASS result Ma1=1.41 4-0.013+0.015 GeV . Next we included finite quark mass effects, which are essential for the tetraquark states involving heavy quarks.

Towards laboratory detection of topological vortices in superfluid phases of QCD

NASA Astrophysics Data System (ADS)

Das, Arpan; Dave, Shreyansh S.; de, Somnath; Srivastava, Ajit M.

2017-10-01

Topological defects arise in a variety of systems, e.g. vortices in superfluid helium to cosmic strings in the early universe. There is an indirect evidence of neutron superfluid vortices from the glitches in pulsars. One also expects that the topological defects may arise in various high baryon density phases of quantum chromodynamics (QCD), e.g. superfluid topological vortices in the color flavor locked (CFL) phase. Though vastly different in energy/length scales, there are universal features in the formation of all these defects. Utilizing this universality, we investigate the possibility of detecting these topological superfluid vortices in laboratory experiments, namely heavy-ion collisions (HICs). Using hydrodynamic simulations, we show that vortices can qualitatively affect the power spectrum of flow fluctuations. This can give an unambiguous signal for superfluid transition resulting in vortices, allowing for the check of defect formation theories in a relativistic quantum field theory system, and the detection of superfluid phases of QCD. Detection of nucleonic superfluid vortices in low energy HICs will give opportunity for laboratory controlled study of their properties, providing crucial inputs for the physics of pulsars.

Baryon interactions from lattice QCD with physical masses — strangeness S = -1 sector —

NASA Astrophysics Data System (ADS)

Nemura, Hidekatsu; Aoki, Sinya; Doi, Takumi; Gongyo, Shinya; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Miyamoto, Takaya; Sasaki, Kenji

2018-03-01

We present our recent results of baryon interactions with strangeness S = -1 based on Nambu-Bethe-Salpeter (NBS) correlation functions calculated fromlattice QCD with almost physical quark masses corresponding to (mk,mk) ≈ (146, 525) MeV and large volume (La)4 ≈ (96a)4 ≈ (8.1 fm)4. In order to perform a comprehensive study of baryon interactions, a large number of NBS correlation functions from NN to ΞΞ are calculated simultaneously by using large scale computer resources. In this contribution, we focus on the strangeness S = -1 channels of the hyperon interactions by means of HAL QCD method. Four sets of three potentials (the 3S1 - 3 D1 central, 3S1 - 3 D1 tensor, and the 1S0 central potentials) are presented for the ∑N - ∑N (the isospin I = 3/2) diagonal, the ∧N - ∧N diagonal, the ∧N → ∑N transition, and the ∑N - ∑N (I = 1/2) diagonal interactions. Scattering phase shifts for ∑N (I = 3/2) system are presented.

Transverse energy and forward jet production in the low x regime at HERA

NASA Astrophysics Data System (ADS)

Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Brasse, F.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Colombo, M.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Coutures, Ch; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Delcourt, B.; Del Buono, L.; De Roeck, A.; De Wolf, E. A.; Di Nezza, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Ehrlichmann, H.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Garvey, J.; Gayler, J.; Gebauer, M.; Gellrich, A.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Gonzalez-Pineiro, B.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Hampel, M.; Hapke, M.; Haynes, W. J.; Heatherington, J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hildesheim, W.; Hill, P.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Horisberger, R.; Hudgson, V. L.; Huet, Ph; Hütte, M.; Hufnagel, H.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kant, D.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Krüner-Marquis, U.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Lanius, P.; Laporte, J.-F.; Lebedev, A.; Lehner, F.; Leverenz, C.; Levonian, S.; Ley, Ch; Lindner, A.; Lindström, G.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lohmander, H.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, A.; Meyer, C. A.; Meyer, H.; Meyer, J.; Migliori, A.; Mikocki, S.; Milstead, D.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Nicholls, T. C.; Nieberball, F.; Niebuhr, C.; Niedzballa, Ch; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Ozerov, D.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Peppel, E.; Perez, E.; Phillips, J. P.; Pichler, Ch; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Prosi, R.; Rabbertz, K.; Rädel, G.; Raupach, F.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Rick, H.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Rylko, R.; Sahlmann, N.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sciacca, G.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Spiekermann, J.; Spitzer, H.; Starosta, R.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stiewe, J.; Stößlein, U.; Stolze, K.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Truöl, P.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; Van Esch, P.; Van Mechelen, P.; Vartapetian, A.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walther, A.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wright, A. E.; Wünsch, E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zimmer, M.; Zimmermann, W.; Zomer, F.; Zuber, K.; zur Nedden, M.; H1 Collaboration

1995-02-01

The production of transverse energy in deep inelastic scattering is measured as a function of the kinematic variables x and Q2 using the H1 detector at the ep collider HERA. The results are compared to the different predictions based upon two alternative QCD evolution equations, namely the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equations. In a pseudorapidity interval which is central in the hadronic centre of mass system between the current and the proton remnant fragmentation region the produced transverse energy increases with decreasing x for constant Q2. Such a behaviour can be explained with a QCD calculation based upon the BFKL ansatz. The rate of forward jets, proposed as a signature for BFKL dynamics, has been measured.

JEWEL 2.0.0: directions for use

NASA Astrophysics Data System (ADS)

Zapp, Korinna

2014-02-01

In this publication the first official release of the Jewel 2.0.0 code [The first version Jewel 1 (Zapp et al. in Eur Phys J C 60:617, 2009) could only treat elastic scattering explicitly and the code was never published, The code can be downloaded from the official Jewel homepage http://jewel.hepforge.org] is presented. Jewel is a Monte Carlo event generator simulating QCD jet evolution in heavy-ion collisions. It treats the interplay of QCD radiation and re-scattering in a medium with fully microscopic dynamics in a consistent perturbative framework with minimal assumptions. After a qualitative introduction into the physics of Jewel detailed information about the practical aspects of using the code is given. The code is available from the official Jewel homepage http://jewel.hepforge.org.

What are the low- Q and large- x boundaries of collinear QCD factorization theorems?

DOE PAGES

Moffat, E.; Melnitchouk, W.; Rogers, T. C.; ...

2017-05-26

Familiar factorized descriptions of classic QCD processes such as deeply-inelastic scattering (DIS) apply in the limit of very large hard scales, much larger than nonperturbative mass scales and other nonperturbative physical properties like intrinsic transverse momentum. Since many interesting DIS studies occur at kinematic regions where the hard scale,more » $$Q \\sim$$ 1-2 GeV, is not very much greater than the hadron masses involved, and the Bjorken scaling variable $$x_{bj}$$ is large, $$x_{bj} \\gtrsim 0.5$$, it is important to examine the boundaries of the most basic factorization assumptions and assess whether improved starting points are needed. Using an idealized field-theoretic model that contains most of the essential elements that a factorization derivation must confront, we retrace in this paper the steps of factorization approximations and compare with calculations that keep all kinematics exact. We examine the relative importance of such quantities as the target mass, light quark masses, and intrinsic parton transverse momentum, and argue that a careful accounting of parton virtuality is essential for treating power corrections to collinear factorization. Finally, we use our observations to motivate searches for new or enhanced factorization theorems specifically designed to deal with moderately low-$Q$ and large-$$x_{bj}$$ physics.« less

Lattice QCD Thermodynamics and RHIC-BES Particle Production within Generic Nonextensive Statistics

NASA Astrophysics Data System (ADS)

Tawfik, Abdel Nasser

2018-05-01

The current status of implementing Tsallis (nonextensive) statistics on high-energy physics is briefly reviewed. The remarkably low freezeout-temperature, which apparently fails to reproduce the firstprinciple lattice QCD thermodynamics and the measured particle ratios, etc. is discussed. The present work suggests a novel interpretation for the so-called " Tsallis-temperature". It is proposed that the low Tsallis-temperature is due to incomplete implementation of Tsallis algebra though exponential and logarithmic functions to the high-energy particle-production. Substituting Tsallis algebra into grand-canonical partition-function of the hadron resonance gas model seems not assuring full incorporation of nonextensivity or correlations in that model. The statistics describing the phase-space volume, the number of states and the possible changes in the elementary cells should be rather modified due to interacting correlated subsystems, of which the phase-space is consisting. Alternatively, two asymptotic properties, each is associated with a scaling function, are utilized to classify a generalized entropy for such a system with large ensemble (produced particles) and strong correlations. Both scaling exponents define equivalence classes for all interacting and noninteracting systems and unambiguously characterize any statistical system in its thermodynamic limit. We conclude that the nature of lattice QCD simulations is apparently extensive and accordingly the Boltzmann-Gibbs statistics is fully fulfilled. Furthermore, we found that the ratios of various particle yields at extreme high and extreme low energies of RHIC-BES is likely nonextensive but not necessarily of Tsallis type.

Mrst '96: Current Ideas in Theoretical Physics - Proceedings of the Eighteenth Annual Montréal-Rochester-Syracuse-Toronto Meeting

NASA Astrophysics Data System (ADS)

O'Donnell, Patrick J.; Smith, Brian Hendee

1996-11-01

The Table of Contents for the full book PDF is as follows: * Preface * Roberto Mendel, An Appreciaton * The Infamous Coulomb Gauge * Renormalized Path Integral in Quantum Mechanics * New Analysis of the Divergence of Perturbation Theory * The Last of the Soluble Two Dimensional Field Theories? * Rb and Heavy Quark Mixing * Rb Problem: Loop Contributions and Supersymmetry * QCD Radiative Effects in Inclusive Hadronic B Decays * CP-Violating Dipole Moments of Quarks in the Kobayashi-Maskawa Model * Hints of Dynamical Symmetry Breaking? * Pi Pi Scattering in an Effective Chiral Lagrangian * Pion-Resonance Parameters from QCD Sum Rules * Higgs Theorem, Effective Action, and its Gauge Invariance * SUSY and the Decay H_2^0 to gg * Effective Higgs-to-Light Quark Coupling Induced by Heavy Quark Loops * Heavy Charged Lepton Production in Superstring Inspired E6 Models * The Elastic Properties of a Flat Crystalline Membrane * Gauge Dependence of Topological Observables in Chern-Simons Theory * Entanglement Entropy From Edge States * A Simple General Treatment of Flavor Oscillations * From Schrödinger to Maupertuis: Least Action Principles from Quantum Mechanics * The Matrix Method for Multi-Loop Feynman Integrals * Simplification in QCD and Electroweak Calculations * Programme * List of Participants

Partonic quasidistributions of the proton and pion from transverse-momentum distributions

NASA Astrophysics Data System (ADS)

Broniowski, Wojciech; Arriola, Enrique Ruiz

2018-02-01

The parton quasidistribution functions (QDFs) of Ji have been found by Radyushkin to be directly related to the transverse momentum distributions (TMDs), to the pseudodistributions, and to the Ioffe-time distributions (ITDs). This makes the QDF results at finite longitudinal momentum of the hadron interesting in their own right. Moreover, the QDF-TMD relation provides a gateway to the pertinent QCD evolution, with respect to the resolution scale Q , for the QDFs. Using the Kwieciński evolution equations and well established parametrizations at a low initial scale, we analyze the QCD evolution of quark and gluon QDF components of the proton and the pion. We discuss the resulting breaking of the longitudinal-transverse factorization and show that it has little impact on QDFs at the relatively low scales presently accessible on the lattice, but the effect is visible in reduced ITDs at sufficiently large values of the Ioffe time. Sum rules involving derivatives of ITDs and moments of the parton distribution functions (PDFs) are applied to the European Twisted Mass Collaboration lattice data. This allows us for a lattice determination of the transverse-momentum width of the TMDs from QDF studies.

Computing Properties of Hadrons, Nuclei and Nuclear Matter from Quantum Chromodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savage, Martin J.

This project was part of a coordinated software development effort which the nuclear physics lattice QCD community pursues in order to ensure that lattice calculations can make optimal use of present, and forthcoming leadership-class and dedicated hardware, including those of the national laboratories, and prepares for the exploitation of future computational resources in the exascale era. The UW team improved and extended software libraries used in lattice QCD calculations related to multi-nucleon systems, enhanced production running codes related to load balancing multi-nucleon production on large-scale computing platforms, and developed SQLite (addressable database) interfaces to efficiently archive and analyze multi-nucleon datamore » and developed a Mathematica interface for the SQLite databases.« less

Asymmetric dark matter and the hadronic spectra of hidden QCD

NASA Astrophysics Data System (ADS)

Lonsdale, Stephen J.; Schroor, Martine; Volkas, Raymond R.

2017-09-01

The idea that dark matter may be a composite state of a hidden non-Abelian gauge sector has received great attention in recent years. Frameworks such as asymmetric dark matter motivate the idea that dark matter may have similar mass to the proton, while mirror matter and G ×G grand unified theories provide rationales for additional gauge sectors which may have minimal interactions with standard model particles. In this work we explore the hadronic spectra that these dark QCD models can allow. The effects of the number of light colored particles and the value of the confinement scale on the lightest stable state, the dark matter candidate, are examined in the hyperspherical constituent quark model for baryonic and mesonic states.

Complementarity of Symmetry Tests at the Energy and Intensity Frontiers

NASA Astrophysics Data System (ADS)

Peng, Tao

We studied several symmetries and interactions beyond the Standard Model and their phenomenology in both high energy colliders and low energy experiments. The lepton number conservation is not a fundamental symmetry in Standard Model (SM). The nature of the neutrino depends on whether or not lepton number is violated. Leptogenesis also requires lepton number violation (LNV). So we want to know whether lepton number is a good symmetry or not, and we want to compare the sensitivity of high energy collider and low energy neutrinoless double-beta decay (0nubetabeta) experiments. To do this, We included the QCD running effects, the background analysis, and the long-distance contributions to nuclear matrix elements. Our result shows that the reach of future tonne-scale 0nubetabeta decay experiments generally exceeds the reach of the 14 TeV LHC for a class of simplified models. For a range of heavy particle masses at the TeV scale, the high luminosity 14 TeV LHC and tonne-scale 0nubetabeta decay experiments may provide complementary probles. The 100 TeV collider with a luminosity of 30 ab-1 exceeds the reach of the tonne-scale 0nubetabeta experiments for most of the range of the heavy particle masses at the TeV scale. We considered a non-Abelian kinetic mixing between the Standard Model gauge bosons and a U(1)' gauge group dark photon, with the existence of an SU(2)L scalar triplet. The coupling constant between the dark photon and the SM gauge bosons epsilon is determined by the triplet vacuum expectation value (vev), the scale of the effective theory Lambda, and the effective operator Wiloson coefficient. The triplet vev is constrained to ≤ 4 GeV. By taking the effective operator Wiloson coefficient to be O(1) and Lambda > 1 TeV, we will have a small value of epsilon which is consistent with the experimental constraint. We outlined the possible LHC signatures and recasted the current ATLAS dark photon experimental results into our non-Abelian mixing scenario. We analyzed the QCD corrections to dark matter (DM) interactions with SM quarks and gluons. Because we like to know the new physics at high scale and the effect of the direct detection of DM at low scale, we studied the QCD running for a list of dark matter effective operators. These corrections are important in precision DM physics. Currently little is known about the short-distance physics of DM. We find that the short-distance QCD corrections generate a finite matching correction when integrating out the electroweak gauge bosons. The high precision measurements of electroweak precision observables can provide crucial input in the search for supersymmetry (SUSY) and play an important role in testing the universality of the SM charged current interaction. We studied the SUSY corrections to such observables DeltaCKM and Deltae/mu, with the experimental constraints on the parameter space. Their corrections are generally of order O(10 -4). Future experiments need to reach this precision to search for SUSY using these observables.

Higher order corrections to mixed QCD-EW contributions to Higgs boson production in gluon fusion

NASA Astrophysics Data System (ADS)

Bonetti, Marco; Melnikov, Kirill; Tancredi, Lorenzo

2018-03-01

We present an estimate of the next-to-leading-order (NLO) QCD corrections to mixed QCD-electroweak contributions to the Higgs boson production cross section in gluon fusion, combining the recently computed three-loop virtual corrections and the approximate treatment of real emission in the soft approximation. We find that the NLO QCD corrections to the mixed QCD-electroweak contributions are nearly identical to NLO QCD corrections to QCD Higgs production. Our result confirms an earlier estimate of these O (α αs2) effects by Anastasiou et al. [J. High Energy Phys. 04 (2009) 003, 10.1088/1126-6708/2009/04/003] and provides further support for the factorization approximation of QCD and electroweak corrections.

QCD for Postgraduates (1/5)

ScienceCinema

Zanderighi, Giulia

2018-04-26

Modern QCD - Lecture 1 Starting from the QCD Lagrangian we will revisit some basic QCD concepts and derive fundamental properties like gauge invariance and isospin symmetry and will discuss the Feynman rules of the theory. We will then focus on the gauge group of QCD and derive the Casimirs CF and CA and some useful color identities.

Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks

NASA Astrophysics Data System (ADS)

Ohta, Shigemi

2006-12-01

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is a-1 ˜ 1.7GeV and the spatial volume is about (1.9fm)3 . Despite the small volume, the ratio of the isovector vector and axial charges gA /gV and that of structure function moments x u-d / x u- d are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is a-1 ˜ 1.6GeV and the spatial volume is about (3.0fm)3 . Even with preliminary statistics of 25-30 gauge configurations, the ratios gA /gV and x u-d / x u- d are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d1 , though yet to be renormalized, appears small in both sets.

Hard QCD processes in the nuclear medium

NASA Astrophysics Data System (ADS)

Freese, Adam

The environment inside the atomic nucleus is one of the most fascinating arenas for the study of quantum chromodynamics (QCD). The strongly-interacting nature of the nuclear medium a?ects the nature of both QCD processes and the quark-gluon structure of hadrons, allowing several unique aspects of the strong nuclear force to be investigated in reactions involving nuclear targets. The research presented in this dissertation explores two aspects of nuclear QCD: firstly, the partonic structure of the nucleus itself; and secondly, the use of the nucleus as a micro-laboratory in which QCD processes can be studied. The partonic structure of the nucleus is calculated in this work by deriving and utilizing a convolution formula. The hadronic structure of the nucleus and the quark-gluon structure of its constituent nucleons are taken together to determine the nuclear partonic structure. Light cone descriptions of short range correlations, in terms of both hadronic and partonic structure, are derived and taken into account. Medium modifications of the bound nucleons are accounted for using the color screening model, and QCD evolution is used to connect nuclear partonic structure at vastly di?erent energy scales. The formalism developed for calculating nuclear partonic structure is applied to inclusive dijet production from proton-nucleus collisions at LHC kinematics, and novel predictions are calculated and presented for the dijet cross section. The nucleus is investigated as a micro-laboratory in vector meson photoproduction reactions. In particular, the deuteron is studied in the break-up reaction gammad → Vpn, for both the φ(1020) and J/v vector mesons. The generalized eikonal approximation is utilized, allowing unambiguous separation of the impulse approximation and final state interactions (FSIs). Two peaks or valleys are seen in the angular distribution of the reaction cross section, each of which is due to an FSI between either the proton and neutron, or the produced vector meson and the spectator nucleon. The presence and size of the latter FSI valley/peak contains information about the meson-nucleon interaction, and it is shown that several models of this interaction can be distinguished by measuring the angular distribution for the deuteron breakup reaction.

Transverse Quark Spin Effects in SIDIS and Drell Yan Scattering

NASA Astrophysics Data System (ADS)

Gamberg, Leonard

2006-10-01

The connection between quark orbital angular momentum and final state interactions for transversely polarized quarks in unpolarized hadrons suggests significant azimuthal asymmetries in pion production in semi-inclusive deep inelastic scattering (SIDIS) (e p->e^'X π) as well as in di- lepton production in Drell Yan (p p->&+circ;&-circ;X and &-circ;p->&+circ;&-circ;X) scattering. When transverse momentum of the reaction, PT is on the order of or less than λqcd, that is PT˜kT where kT is intrinsic transverse quark momentum, these effects are characterized in term of naive time reversal odd (so called T-odd) transverse momentum dependent (TMD) parton distribution and fragmentation functions. At these moderate transverse momentum scales we estimate the size of the 2φ azimuthal asymmetry in SIDIS and Drell Yan scattering in the parton spectator framework. In the former case we consider this so called ``Boer-Mulders'' effect for a proposed experiment at the upgraded CLAS-12 GeV detector at Jefferson LAB. In the latter case we consider this asymmetry for proton anti-proton collider, as well as π nucleon fixed target experiments. We also consider competing contributions to these asymmetries from perturbative QCD (pQCD) contributions which emerge when PT> λqcd. Evidence of a strong dependence on transverse momentum would indicate the presence of T-odd structures in unpolarized SIDIS and Drell Yan scattering, implying that transversity properties of the nucleon can be accessed without invoking beam or target polarization.

Novel topological effects in dense QCD in a magnetic field

NASA Astrophysics Data System (ADS)

Ferrer, E. J.; de la Incera, V.

2018-06-01

We study the electromagnetic properties of dense QCD in the so-called Magnetic Dual Chiral Density Wave phase. This inhomogeneous phase exhibits a nontrivial topology that comes from the fermion sector due to the asymmetry of the lowest Landau level modes. The nontrivial topology manifests in the electromagnetic effective action via a chiral anomaly term θFμνF˜μν, with a dynamic axion field θ given by the phase of the Dual Chiral Density Wave condensate. The coupling of the axion with the electromagnetic field leads to several macroscopic effects that include, among others, an anomalous, nondissipative Hall current, an anomalous electric charge, magnetoelectricity, and the formation of a hybridized propagating mode known as an axion polariton. Connection to topological insulators and Weyls semimetals, as well as possible implications for heavy-ion collisions and neutron stars are all highlighted.

Ab initio calculation of finite-temperature charmonium potentials

NASA Astrophysics Data System (ADS)

Evans, P. W. M.; Allton, C. R.; Skullerud, J.-I.

2014-04-01

The interquark potential in charmonium states is calculated in both the zero and nonzero temperature phases from a first-principles lattice QCD calculation. Simulations with two dynamical quark flavors are used with temperatures T in the range 0.4Tc≲T≲1.7Tc, where Tc is the deconfining temperature. The correlators of point-split operators are analyzed to gain spatial information about the charmonium states. A method introduced by the HAL QCD Collaboration and based on the Schrödinger equation is applied to obtain the interquark potential. We find a clear temperature dependence with the central potential agreeing with the Cornell potential in the confined phase and becoming flatter (more screened) as the temperature increases past the deconfining temperature. This is the first time the interquark potential has been calculated for realistic quarks at finite temperature.

Progress on Complex Langevin simulations of a finite density matrix model for QCD

NASA Astrophysics Data System (ADS)

Bloch, Jacques; Glesaaen, Jonas; Verbaarschot, Jacobus; Zafeiropoulos, Savvas

2018-03-01

We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to intended theory with dynamical quarks. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. We study the effect of gauge cooling on the Dirac eigenvalue distribution and time evolution of the norm for various cooling norms, which were specifically designed to remove the pathologies of the complex Langevin evolution. The cooling is further supplemented with a shifted representation for the random matrices. Unfortunately, none of these modifications generate a substantial improvement on the complex Langevin evolution and the final results still do not agree with the analytical predictions.

Chiral Dynamics 2006

NASA Astrophysics Data System (ADS)

Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry

2007-10-01

pt. A. Plenary session. Opening remarks: experimental tests of chiral symmetry breaking / A. M. Bernstein. [Double pie symbols] scattering / H. Leutwyler. Chiral effective field theory in a [Triangle]-resonance region / V. Pascalutsa. Some recent developments in chiral perturbation theory / Ulf-G. Mei ner. Chiral extrapolation and nucleon structure from the lattice / R.D. Young. Recent results from HAPPEX / R. Michaels. Chiral symmetries and low energy searches for new physics / M.J. Ramsey-Musolf. Kaon physics: recent experimental progress / M. Moulson. Status of the Cabibbo angle / V. Cirigliano. Lattice QCD and nucleon spin structure / J.W. Negele. Spin sum rules and polarizabilities: results from Jefferson lab / J-P Chen. Compton scattering and nucleon polarisabilities / Judith A. McGovern. Virtual compton scattering at MIT-bates / R. Miskimen. Physics results from the BLAST detector at the BATES accelerator / R.P. Redwine. The [Pie sympbol]NN system, recent progress / C. Hanhart. Application of chiral nuclear forces to light nuclei / A. Nogga. New results on few-body experiments at low energy / Y. Nagai. Few-body lattice calculations / M.J. Savage. Research opportunities at the upgraded HI?S facility / H.R. Weller -- pt. B. Goldstone boson dynamics. Working group summary: Goldstone Boson dynamics / G. Colangelo and S. Giovannella. Recent results on radiative Kaon decays from NA48 and NA48/2 / S.G. López. Cusps in K-->3 [Pie symbol] decays / B. Kubis. Recent KTeV results on radiative Kaon decays / M.C. Ronquest. The [Double pie symbols] scattering amplitude / J.R. Peláez. Determination of the Regge parameters in the [Double pie symbols] scattering amplitude / I. Caprini. e+e- Hadronic cross section measurement at DA[symbol]NE with the KLOE detector / P. Beltrame. Measurement of the form factors of e+e- -->2([Pie symbol]+[Pie symbol]-), pp and the resonant parameters of the heavy charmonia at BES / H. Hu. Measurement of e+e- multihadronic cross section below 4.5 GeV with BABAR / A. Denig. The pion vector form-factor and (g-2)u / C. Smith. Partially quenched CHPT results to two loops / J. Bijnens. Pion-pion scattering with mixed action lattice QCD / P.F. Bedaque. Meson systems with Ginsparg-Wilson valence quarks / A. Walker-Loud. Low energy constants from the MILC collaboration / C. Bernard. Finite volume effects: lattice meets CHPT / G. Schierholz. Lattice QCD simulations with two light dynamical (Wilson) quarks / L. Giusti. Do we understand the low-energy constant L8? / M. Golterman. Quark mass dependence of LECs in the two-flavour sector / M. Schmid. Progress report on the [Pie symbol]0 Lifetime experiment (PRIMEX) at Jlab / D.E. McNulty. Determination of the charged pion polarizabilities / L.V. Fil'kov. Proposed measurement of electroproduction of [Pie symbol]0 near threshold using a large acceptance spectrometer / R.A. Lindgren. The [Pie symbol] meson in [Pie symbol]K scattering / B. Moussallam. Strangeness -1 Meson-Baryon scattering S-wave / J.A. Oller. Results on light mesons decays and dynamics at KLOE / M. Martini. Studies of decays of [symbol] and [symbol] mesons with WASA detector / A. Kupsc. Heavy Quark-Diquark symmetry and X PT for doubly heavy baryons / T. Mehen. HHChPT applied to the charmed-strange parity partners/ R.P. Springer. Study of pion structure through precise measurements of the [Pie symbol]+ --> e+[symbol] decay / D. Pocanic. Exceptional and non-exceptional contributions to the radiative [Pie symbol] decay / V. Mateu. Leading chiral logarithms from unitarity, analyticity and the Roy equations / A. Fuhrer. All orders symmetric subtraction of the nonlinear sigma model in D=4 / A. Quadri -- pt. C. Chiral dynamics in few-nucleon systems. Working group summary: chiral dynamics in few-nucleon systems / H.W Hammer, N. Kalantar-Nayestanaki, and D.R. Phillips. Power counting in nuclear chiral effective field theory / U. van Kolck. On the consistency of Weinberg's power counting / U-G Mei ner. Renormalization of singular potentials and power counting / M.P. Valderrrama. The challenge of calculating Baryon-Baryon scattering from lattice QCD / S.R. Beane. Precise absolute np scattering cross section and the charged [Pie symbol] NN coupling constant / S. E. Vigdor. Probing hadronic parity violation using few nucleon systems / S.A. Page. Extracting the neutron-neutron scattering length from neutron-deuteron breakup / C.R. Howell. Extraction of [equationl] from [Pie symbol]-d --> [equation] / A. Grudestig. The three- and four-body system with large scattering length / L. Platter. 3N and 4N systems and the Ay puzzle / T. Clegg. Recent progress in nuclear lattice simulations with effective field theory / D. Lee. Few-body studies at KVI / J.G. Messchendorp. Results of three nucleon experiments from RIKEN / K. Sekiguchi. A new opportunity to measure the total photoabsorption cross section of helium / P. T. Debevec. Three-body photodisintegration of 3He with double polarizations / X. Zong. Large two-pion exchange contributions to the pp --> pp[Pie symbol]0 reaction / F. Myhrer. Towards a systematic theory of nuclear forces / E. Epelbaum. Ab initio calculations of eletromagnetic reactions in light nuclei / W. Leidemann. Electron scattering from a polarized deuterium target at BLAST / R. Fatemi. Neutron-neutron scattering length from the reaction [equation] / V. Lensky. Renormalization group analysis of nuclear current operators / S.X. Nakamura. Recent results and future plans at MAX-LAB / K.G. Fissum. Nucleon polarizabilities from deutron compton scattering, and its lessons for chiral power counting / H. W. Grie hammer. Compton scattering on HE-3 / D. Choudhury -- pt. D. Hadron structure and Meson-Baryon interactions. Summary of the working group on Hadron structure and Meson-Baryon interactions / G. Feldman and T.R. Hemmert. Finite volume effects: lattice meets CHPT / G. Schierholz. Lattice discretization errors in chiral effective field theories / B.C. Tiburzi. SU(3)-breaking effects in hyperon semileptonic decays from lattice QCD / S. Simula. Uncertainty bands for chiral extrapolations / B.U. Musch. Update of the nucleon electromagnetic form factors / C. B. Crawford. N and N to ? transition from factors from lattice QCD / C. Alexandrou. The [equation] transition at low Q2 and the pionic contribution / S. Stave. Strange Quark CoNtributions to the form factors of the nucleon / F. Benmokhtar. Dynamical polarizabilities of the nucleon / B. Pasquini. Hadron magnetic moments and polarizabilities in lattice QCD / F.X. Lee. Spin-dependent compton scattering from 3He and the neutron spin polarizabilities / H. Gao. Chiral dynamics from Dyson-Schwinger equations / C.D. Roberts. Radiative neutron [Beta symbol]-decay in effective field theory / S. Gardner. Comparison between different renormalization schemes for co-variant BChPT / T.A. Gail. Non-perturbative study of the light pseudoscalar masses in chiral dynamics / José Antonio Oller. Masses and widths of hadrons in nuclear matter / M. Kotulla. Chiral effective field theory at finite density / R.J. Furnstahl. The K-nuclear interaction: a search fro deeply bound K-nuclear clusters / P. Camerini. Moments of GPDs from lattice QCD / D.G. Richards. Generalized parton distributions in effective field theory / J.W. Chen. Near-threshold pion production: experimental update / M.W. Ahmed. Pion photoproduction near threshold theory update / L. Tiator.

Exploring Partonic Structure of Hadrons Using ab initio Lattice QCD Calculations.

PubMed

Ma, Yan-Qing; Qiu, Jian-Wei

2018-01-12

Following our previous proposal, we construct a class of good "lattice cross sections" (LCSs), from which we can study the partonic structure of hadrons from ab initio lattice QCD calculations. These good LCSs, on the one hand, can be calculated directly in lattice QCD, and on the other hand, can be factorized into parton distribution functions (PDFs) with calculable coefficients, in the same way as QCD factorization for factorizable hadronic cross sections. PDFs could be extracted from QCD global analysis of the lattice QCD generated data of LCSs. We also show that the proposed functions for lattice QCD calculation of PDFs in the literature are special cases of these good LCSs.

Renormalization constants for 2-twist operators in twisted mass QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexandrou, C.; Computation-based Science and Technology Research Center, The Cyprus Institute, 15 Kypranoros Str., 1645 Nicosia; Constantinou, M.

2011-01-01

Perturbative and nonperturbative results on the renormalization constants of the fermion field and the twist-2 fermion bilinears are presented with emphasis on the nonperturbative evaluation of the one-derivative twist-2 vector and axial-vector operators. Nonperturbative results are obtained using the twisted mass Wilson fermion formulation employing two degenerate dynamical quarks and the tree-level Symanzik improved gluon action. The simulations have been performed for pion masses in the range of about 450-260 MeV and at three values of the lattice spacing a corresponding to {beta}=3.9, 4.05, 4.20. Subtraction of O(a{sup 2}) terms is carried out by performing the perturbative evaluation of thesemore » operators at 1-loop and up to O(a{sup 2}). The renormalization conditions are defined in the RI{sup '}-MOM scheme, for both perturbative and nonperturbative results. The renormalization factors, obtained for different values of the renormalization scale, are evolved perturbatively to a reference scale set by the inverse of the lattice spacing. In addition, they are translated to MS at 2 GeV using 3-loop perturbative results for the conversion factors.« less

Introducing MCgrid 2.0: Projecting cross section calculations on grids

NASA Astrophysics Data System (ADS)

Bothmann, Enrico; Hartland, Nathan; Schumann, Steffen

2015-11-01

MCgrid is a software package that provides access to interpolation tools for Monte Carlo event generator codes, allowing for the fast and flexible variation of scales, coupling parameters and PDFs in cutting edge leading- and next-to-leading-order QCD calculations. We present the upgrade to version 2.0 which has a broader scope of interfaced interpolation tools, now providing access to fastNLO, and features an approximated treatment for the projection of MC@NLO-type calculations onto interpolation grids. MCgrid 2.0 also now supports the extended information provided through the HepMC event record used in the recent SHERPA version 2.2.0. The additional information provided therein allows for the support of multi-jet merged QCD calculations in a future update of MCgrid.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, John; Carena, Marcela; Harnik, Roni

We consider interference between the Higgs signal and QCD background inmore » $$gg\\rightarrow h \\rightarrow \\gamma\\gamma$$ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the Standard Model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss potential width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly probe widths of order tens of MeV.« less

Hard diffraction in the QCD dipole picture

NASA Astrophysics Data System (ADS)

Bialas, A.; Peschanski, R.

1996-02-01

Using the QCD dipole picture of the BFKL pomeron, the gluon contribution to the cross-section for single diffractive dissociation in deep-inelastic high-energy scattering is calculated. The resulting contribution to the proton diffractive structure function integrated over t is given in terms of relevant variables, xP, Q2, and β = {x Bj}/{x P}. It factorizes into an explicit x P-dependent Hard Pomeron flux factor and structure function. The lux factor is found to have substantial logarithmic corrections which may account for the recent measurements of the Pomeron intercept in this process. The triple Pomeron coupling is shown to be strongly enhanced by the resummation of leading logs. The obtained pattern of scaling violation at small β is similar to that for F2 at small xBj.

Modified QCD ghost f(T,TG) gravity

NASA Astrophysics Data System (ADS)

Jawad, Abdul; Rani, Shamaila; Chattopadhyay, Surajit

2015-12-01

In this paper, we explore the reconstruction scenario of modified QCD ghost dark energy model and newly proposed f(T,TG) gravity in flat FRW universe. We consider the well-known assumption of scale factor, i.e., power law form. We construct the f(T,TG) model and discuss its cosmological consequences through various cosmological parameters such as equation of state parameter, squared speed of sound and ω_{DE}-ω '_{DE}. The equation of state parameter provides the quintom-like behavior of the universe. The squared speed of sound exhibits the stability of model in the later time. Also, ω_{DE}- ω '_{DE} corresponds to freezing as well as thawing regions. It is also interesting to remark here that the results of equation of state parameter and w_{DE}-w'_{DE} coincide with the observational data.

A Scale-Invariant ``Discrete-Time'' Balitsky--Kovchegov Equation

NASA Astrophysics Data System (ADS)

Bialas, A.; Peschanski, R.

2005-06-01

We consider a version of QCD dipole cascading corresponding to a finite number n of discrete Δ Y steps of branching in rapidity. Using the discretization scheme preserving the holomorphic factorizability and scale-invariance in position space of the dipole splitting function, we derive an exact recurrence formula from step to step which plays the rôle of a ``discrete-time'' Balitsky--Kovchegov equation. The BK solutions are recovered in the limit n=∞ and Δ Y=0.

Combination and QCD analysis of charm and beauty production cross-section measurements in deep inelastic ep scattering at HERA

NASA Astrophysics Data System (ADS)

Abramowicz, H.; Abt, I.; Adamczyk, L.; Adamus, M.; Aggarwal, R.; Andreev, V.; Antonelli, S.; Aushev, V.; Baghdasaryan, A.; Begzsuren, K.; Behnke, O.; Behrens, U.; Belousov, A.; Bertolin, A.; Bloch, I.; Bolz, A.; Boudry, V.; Brandt, G.; Brisson, V.; Britzger, D.; Brock, I.; Brook, N. H.; Brugnera, R.; Bruni, A.; Buniatyan, A.; Bussey, P. J.; Bylinkin, A.; Bystritskaya, L.; Caldwell, A.; Campbell, A. J.; Avila, K. B. Cantun; Capua, M.; Catterall, C. D.; Cerny, K.; Chekelian, V.; Chwastowski, J.; Ciborowski, J.; Ciesielski, R.; Contreras, J. G.; Cooper-Sarkar, A. M.; Corradi, M.; Cvach, J.; Dainton, J. B.; Daum, K.; Dementiev, R. K.; Devenish, R. C. E.; Diaconu, C.; Dobre, M.; Dusini, S.; Eckerlin, G.; Egli, S.; Elsen, E.; Favart, L.; Fedotov, A.; Feltesse, J.; Fleischer, M.; Fomenko, A.; Foster, B.; Gallo, E.; Garfagnini, A.; Gayler, J.; Geiser, A.; Gizhko, A.; Gladilin, L. K.; Goerlich, L.; Gogitidze, N.; Golubkov, Yu. A.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Grzelak, G.; Gwenlan, C.; Haidt, D.; Henderson, R. C. W.; Hladkỳ, J.; Hlushchenko, O.; Hochman, D.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Ibrahim, Z. A.; Iga, Y.; Jacquet, M.; Janssen, X.; Jomhari, N. Z.; Jung, A. W.; Jung, H.; Kadenko, I.; Kananov, S.; Kapichine, M.; Karshon, U.; Katzy, J.; Kaur, P.; Kiesling, C.; Kisielewska, D.; Klanner, R.; Klein, M.; Klein, U.; Kleinwort, C.; Kogler, R.; Korzhavina, I. A.; Kostka, P.; Kotański, A.; Kovalchuk, N.; Kowalski, H.; Kretzschmar, J.; Krücker, D.; Krüger, K.; Krupa, B.; Kuprash, O.; Kuze, M.; Landon, M. P. J.; Lange, W.; Laycock, P.; Lebedev, A.; Levchenko, B. B.; Levonian, S.; Levy, A.; Libov, V.; Lipka, K.; Lisovyi, M.; List, B.; List, J.; Lobodzinski, B.; Löhr, B.; Lohrmann, E.; Longhin, A.; Lukina, O. Yu.; Makarenko, I.; Malinovski, E.; Malka, J.; Martyn, H.-U.; Masciocchi, S.; Maxfield, S. J.; Mehta, A.; Meyer, A. B.; Meyer, H.; Meyer, J.; Mikocki, S.; Idris, F. Mohamad; Mohammad Nasir, N.; Morozov, A.; Müller, K.; Myronenko, V.; Nagano, K.; Nam, J. D.; Naumann, Th.; Newman, P. R.; Nicassio, M.; Niebuhr, C.; Nowak, G.; Olsson, J. E.; Onderwaater, J.; Onishchuk, Yu.; Ozerov, D.; Pascaud, C.; Patel, G. D.; Paul, E.; Perez, E.; Perlański, W.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Pokrovskiy, N. S.; Polifka, R.; Polini, A.; Przybycień, M.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Ruspa, M.; Šálek, D.; Sankey, D. P. C.; Sauter, M.; Sauvan, E.; Saxon, D. H.; Schioppa, M.; Schmitt, S.; Schneekloth, U.; Schoeffel, L.; Schöning, A.; Schörner-Sadenius, T.; Sefkow, F.; Selyuzhenkov, I.; Shcheglova, L. M.; Shushkevich, S.; Shyrma, Yu.; Skillicorn, I. O.; Słomiński, W.; Solano, A.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Stanco, L.; Steder, M.; Stefaniuk, N.; Stella, B.; Stern, A.; Stopa, P.; Straumann, U.; Surrow, B.; Sykora, T.; Sztuk-Dambietz, J.; Tassi, E.; Thompson, P. D.; Tokushuku, K.; Tomaszewska, J.; Traynor, D.; Truöl, P.; Tsakov, I.; Tseepeldorj, B.; Tsurugai, T.; Turcato, M.; Turkot, O.; Tymieniecka, T.; Valkárová, A.; Vallée, C.; Van Mechelen, P.; Vazdik, Y.; Verbytskyi, A.; Abdullah, W. A. T. Wan; Wegener, D.; Wichmann, K.; Wing, M.; Wünsch, E.; Yamada, S.; Yamazaki, Y.; Žáček, J.; Żarnecki, A. F.; Zawiejski, L.; Zenaiev, O.; Zhang, Z.; Zhautykov, B. O.; Žlebčík, R.; Zohrabyan, H.; Zomer, F.

2018-06-01

Measurements of open charm and beauty production cross sections in deep inelastic ep scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the kinematic range of negative four-momentum transfer squared of the photon 2.5 GeV^2≤Q^2 ≤2000 GeV^2 and Bjorken scaling variable 3 \\cdot 10^{-5} ≤ x_Bj ≤ 5 \\cdot 10^{-2}. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as m_c(m_c) = 1.290^{+0.046}_{-0.041} (exp/fit) {}^{+0.062}_{-0.014} (model) {}^{+0.003}_{-0.031} (parameterisation) GeV and m_b(m_b) = 4.049^{+0.104}_{-0.109} (exp/fit) {}^{+0.090}_{-0.032} (model) {}^{+0.001}_{-0.031} (parameterisation) GeV.

Heavy quarkonia in a potential model: binding energy, decay width, and survival probability

NASA Astrophysics Data System (ADS)

Srivastava, P. K.; Chaturvedi, O. S. K.; Thakur, Lata

2018-06-01

Recently a lot of progress has been made in deriving the heavy quark potential within a QCD medium. In this article we have considered heavy quarkonium in a hot quark gluon plasma phase. The heavy-quark potential has been modeled properly for short as well as long distances. The potential at long distances is modeled as a QCD string which is screened at the same scale as the Coulomb field. We have numerically solved the 1+1-dimensional Schrodinger equation for this potential and obtained the eigen wavefunction and binding energy for the 1 S and 2 S states of charmonium and bottomonium. Further, we have calculated the decay width and dissociation temperature of quarkonium states in the QCD plasma. Finally, we have used our recently proposed unified model with these new values of decay widths to calculate the survival probability of the various quarkonium states with respect to centrality at relativistic heavy ion collider and large hadron collider energies. This study provides a unified, consistent and comprehensive description of spectroscopic properties of various quarkonium states at finite temperatures along with their nuclear modification factor at different collision energies.

Applications of QCD factorization in multiscale Hadronic scattering

NASA Astrophysics Data System (ADS)

Wang, Bowen

In this thesis I apply QCD factorization theorems to two important hadronic processes. In the first study, I treat the inclusive cross section of the production of massive quarks through neutral current deep inelasitc scattering (DIS): (n/a). In this study I work out a method to consistently organize the QCD radiative contributions up to O(alphas 3) (N3LO), with a proper inclusion of the heavy quark mass dependence at different momentum scales. The generic implementation of the mass dependence developed in this thesis can be used by calculations in both an intermediate-mass factorization scheme and a general-mass factorization scheme. The mass effect is relevant to the predictions for Higgs, and W and Z cross sections measured at the LHC. The second study examines the transverse-momentum distribution of the lepton-pair production in Drell-yan process. The theory predictions based on the Collins-Soper-Sterman (CSS) resummation formalism at NNLL accuracy are compared with the new data on the angular distribution *eta of Drell-Yan pairs measured at the Tevatron and the LHC. The main finding is that the nonperturbative component of the CSS resummed cross section plays a crucial part in explaining the data in the small transverse momentum region.

Nucleon Structure from 2+1 Flavor Domain Wall QCD at Nearly Physical Pion Mass

NASA Astrophysics Data System (ADS)

Ohta, Shigemi

2011-05-01

The RBC and UKQCD collaborations have been investigating hadron physics in numerical lattice quantum chromodynamics (QCD) with (2+1) flavors of dynamical domain wall fermions (DWF) quarks that preserves continuum-like chiral and flavor symmetries. The strange quark mass is adjusted to physical value via reweighting and degenerate up and down quark masses are set as light as possible. In a recent study of nucleon structure we found a strong dependence on pion mass and lattice spatial extent in isovector axialvector-current form factors. This is likely the first credible evidence for the pion cloud surrounding nucleon. Here we report the status of nucleon structure calculations with a new (2+1)-flavor dynamical DWF ensembles with much lighter pion mass of 180 and 250 MeV and a much larger lattice spatial exent of 4.6 fm. A combination of the Iwasaki and dislocation-suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while keeping the residual breaking of chiral symmetry sufficiently small. Nucleon source Gaussian smearing has been optimized. Preliminary nucleon mass estimates are 0.98 and 1.05 GeV.

Holographic Jet Shapes and their Evolution in Strongly Coupled Plasma

NASA Astrophysics Data System (ADS)

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey; van der Schee, Wilke

2017-11-01

Recently our group analyzed how the probability distribution for the jet opening angle is modified in an ensemble of jets that has propagated through an expanding cooling droplet of plasma [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603]. Each jet in the ensemble is represented holographically by a string in the dual 4+1- dimensional gravitational theory with the distribution of initial energies and opening angles in the ensemble given by perturbative QCD. In [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603], the full string dynamics were approximated by assuming that the string moves at the speed of light. We are now able to analyze the full string dynamics for a range of possible initial conditions, giving us access to the dynamics of holographic jets just after their creation. The nullification timescale and the features of the string when it has nullified are all results of the string evolution. This emboldens us to analyze the full jet shape modification, rather than just the opening angle modification of each jet in the ensemble as in [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603]. We find the result that the jet shape scales with the opening angle at any particular energy. We construct an ensemble of dijets with energies and energy asymmetry distributions taken from events in proton-proton collisions, opening angle distribution as in [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603], and jet shape taken from proton-proton collisions and scaled according to our result. We study how these observables are modified after we send the ensemble of dijets through the strongly-coupled plasma.

QCD as a Theory of Hadrons

NASA Astrophysics Data System (ADS)

Narison, Stephan

2004-05-01

About Stephan Narison; Outline of the book; Preface; Acknowledgements; Part I. General Introduction: 1. A short flash on particle physics; 2. The pre-QCD era; 3. The QCD story; 4. Field theory ingredients; Part II. QCD Gauge Theory: 5. Lagrangian and gauge invariance; 6. Quantization using path integral; 7. QCD and its global invariance; Part III. MS scheme for QCD and QED: Introduction; 8. Dimensional regularization; 9. The MS renormalization scheme; 10. Renormalization of operators using the background field method; 11. The renormalization group; 12. Other renormalization schemes; 13. MS scheme for QED; 14. High-precision low-energy QED tests; Part IV. Deep Inelastic Scattering at Hadron Colliders: 15. OPE for deep inelastic scattering; 16. Unpolarized lepton-hadron scattering; 17. The Altarelli-Parisi equation; 18. More on unpolarized deep inelastic scatterings; 19. Polarized deep-inelastic processes; 20. Drell-Yan process; 21. One 'prompt photon' inclusive production; Part V. Hard Processes in e+e- Collisions: Introduction; 22. One hadron inclusive production; 23. gg scatterings and the 'spin' of the photon; 24. QCD jets; 25. Total inclusive hadron productions; Part VI. Summary of QCD Tests and as Measurements; Part VII. Power Corrections in QCD: 26. Introduction; 27. The SVZ expansion; 28. Technologies for evaluating Wilson coefficients; 29. Renormalons; 30. Beyond the SVZ expansion; Part VIII. QCD Two-Point Functions: 31. References guide to original works; 32. (Pseudo)scalar correlators; 33. (Axial-)vector two-point functions; 34. Tensor-quark correlator; 35. Baryonic correlators; 36. Four-quark correlators; 37. Gluonia correlators; 38. Hybrid correlators; 39. Correlators in x-space; Part IX. QCD Non-Perturbative Methods: 40. Introduction; 41. Lattice gauge theory; 42. Chiral perturbation theory; 43. Models of the QCD effective action; 44. Heavy quark effective theory; 45. Potential approaches to quarkonia; 46. On monopole and confinement; Part X. QCD Spectral Sum Rules: 47. Introduction; 48. Theoretical foundations; 49. Survey of QCD spectral sum rules; 50. Weinberg and DMO sum rules; 51. The QCD coupling as; 52. The QCD condensates; 53. Light and heavy quark masses, etc.; 54. Hadron spectroscopy; 55. D, B and Bc exclusive weak decays; 56. B0(s)-B0(s) mixing, kaon CP violation; 57. Thermal behaviour of QCD; 58. More on spectral sum rules; Part XI. Appendix A: physical constants and unites; Appendix B: weight factors for SU(N)c; Appendix C: coordinates and momenta; Appendix D: Dirac equation and matrices; Appendix E: Feynman rules; Appendix F: Feynman integrals; Appendix G: useful formulae for the sum rules; Bibliography; Index.

QCD as a Theory of Hadrons

NASA Astrophysics Data System (ADS)

Narison, Stephan

2007-07-01

About Stephan Narison; Outline of the book; Preface; Acknowledgements; Part I. General Introduction: 1. A short flash on particle physics; 2. The pre-QCD era; 3. The QCD story; 4. Field theory ingredients; Part II. QCD Gauge Theory: 5. Lagrangian and gauge invariance; 6. Quantization using path integral; 7. QCD and its global invariance; Part III. MS scheme for QCD and QED: Introduction; 8. Dimensional regularization; 9. The MS renormalization scheme; 10. Renormalization of operators using the background field method; 11. The renormalization group; 12. Other renormalization schemes; 13. MS scheme for QED; 14. High-precision low-energy QED tests; Part IV. Deep Inelastic Scattering at Hadron Colliders: 15. OPE for deep inelastic scattering; 16. Unpolarized lepton-hadron scattering; 17. The Altarelli-Parisi equation; 18. More on unpolarized deep inelastic scatterings; 19. Polarized deep-inelastic processes; 20. Drell-Yan process; 21. One 'prompt photon' inclusive production; Part V. Hard Processes in e+e- Collisions: Introduction; 22. One hadron inclusive production; 23. gg scatterings and the 'spin' of the photon; 24. QCD jets; 25. Total inclusive hadron productions; Part VI. Summary of QCD Tests and as Measurements; Part VII. Power Corrections in QCD: 26. Introduction; 27. The SVZ expansion; 28. Technologies for evaluating Wilson coefficients; 29. Renormalons; 30. Beyond the SVZ expansion; Part VIII. QCD Two-Point Functions: 31. References guide to original works; 32. (Pseudo)scalar correlators; 33. (Axial-)vector two-point functions; 34. Tensor-quark correlator; 35. Baryonic correlators; 36. Four-quark correlators; 37. Gluonia correlators; 38. Hybrid correlators; 39. Correlators in x-space; Part IX. QCD Non-Perturbative Methods: 40. Introduction; 41. Lattice gauge theory; 42. Chiral perturbation theory; 43. Models of the QCD effective action; 44. Heavy quark effective theory; 45. Potential approaches to quarkonia; 46. On monopole and confinement; Part X. QCD Spectral Sum Rules: 47. Introduction; 48. Theoretical foundations; 49. Survey of QCD spectral sum rules; 50. Weinberg and DMO sum rules; 51. The QCD coupling as; 52. The QCD condensates; 53. Light and heavy quark masses, etc.; 54. Hadron spectroscopy; 55. D, B and Bc exclusive weak decays; 56. B0(s)-B0(s) mixing, kaon CP violation; 57. Thermal behaviour of QCD; 58. More on spectral sum rules; Part XI. Appendix A: physical constants and unites; Appendix B: weight factors for SU(N)c; Appendix C: coordinates and momenta; Appendix D: Dirac equation and matrices; Appendix E: Feynman rules; Appendix F: Feynman integrals; Appendix G: useful formulae for the sum rules; Bibliography; Index.

Tests of Local Position Invariance Using Continuously Running Atomic Clocks

DTIC Science & Technology

2013-01-22

of the difference in anomalous redshift parameters, β = β1 − β2. (a) Dark data points are previous measurements: (i) neutral strontium optical...and the ratio of the light quark mass to the quantum chromodynamics length scale, mq/ QCD, where mq is the average of the up and down quark masses [17

QCD evolution of the Sivers function

NASA Astrophysics Data System (ADS)

Aybat, S. M.; Collins, J. C.; Qiu, J. W.; Rogers, T. C.

2012-02-01

We extend the Collins-Soper-Sterman (CSS) formalism to apply it to the spin dependence governed by the Sivers function. We use it to give a correct numerical QCD evolution of existing fixed-scale fits of the Sivers function. With the aid of approximations useful for the nonperturbative region, we present the results as parametrizations of a Gaussian form in transverse-momentum space, rather than in the Fourier conjugate transverse coordinate space normally used in the CSS formalism. They are specifically valid at small transverse momentum. Since evolution has been applied, our results can be used to make predictions for Drell-Yan and semi-inclusive deep inelastic scattering at energies different from those where the original fits were made. Our evolved functions are of a form that they can be used in the same parton-model factorization formulas as used in the original fits, but now with a predicted scale dependence in the fit parameters. We also present a method by which our evolved functions can be corrected to allow for twist-3 contributions at large parton transverse momentum.

Two-color QCD at high density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boz, Tamer; Skullerud, Jon-Ivar; Centre for the Subatomic Structure of Matter, Adelaide University, Adelaide, SA 5005

2016-01-22

QCD at high chemical potential has interesting properties such as deconfinement of quarks. Two-color QCD, which enables numerical simulations on the lattice, constitutes a laboratory to study QCD at high chemical potential. Among the interesting properties of two-color QCD at high density is the diquark condensation, for which we present recent results obtained on a finer lattice compared to previous studies. The quark propagator in two-color QCD at non-zero chemical potential is referred to as the Gor’kov propagator. We express the Gor’kov propagator in terms of form factors and present recent lattice simulation results.

Progress in vacuum susceptibilities and their applications to the chiral phase transition of QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Zhu-Fang, E-mail: phycui@nju.edu.cn; State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing, 100190; Hou, Feng-Yao

2015-07-15

The QCD vacuum condensates and various vacuum susceptibilities are all important parameters which characterize the nonperturbative properties of the QCD vacuum. In the QCD sum rules external field formula, various QCD vacuum susceptibilities play important roles in determining the properties of hadrons. In this paper, we review the recent progress in studies of vacuum susceptibilities together with their applications to the chiral phase transition of QCD. The results of the tensor, the vector, the axial–vector, the scalar, and the pseudo-scalar vacuum susceptibilities are shown in detail in the framework of Dyson–Schwinger equations.

Lattice NRQCD study of S- and P-wave bottomonium states in a thermal medium with Nf=2 +1 light flavors

NASA Astrophysics Data System (ADS)

Kim, Seyong; Petreczky, Peter; Rothkopf, Alexander

2015-03-01

We investigate the properties of S - and P -wave bottomonium states in the vicinity of the deconfinement transition temperature. The light degrees of freedom are represented by dynamical lattice quantum chromodynamics (QCD) configurations of the HotQCD collaboration with Nf=2 +1 flavors. Bottomonium correlators are obtained from bottom quark propagators, computed in nonrelativistic QCD under the background of these gauge field configurations. The spectral functions for the 3S1 (ϒ ) and 3P1 (χb 1) channel are extracted from the Euclidean time correlators using a novel Bayesian approach in the temperature region 140 MeV ≤T ≤249 MeV and the results are contrasted to those from the standard maximum entropy method. We find that the new Bayesian approach is far superior to the maximum entropy method. It enables us to study reliably the presence or absence of the lowest state signal in the spectral function of a certain channel, even under the limitations present in the finite temperature setup. We find that χb 1 survives up to T =249 MeV , the highest temperature considered in our study, and put stringent constraints on the size of the medium modification of ϒ and χb 1 states.

Finite-volume and partial quenching effects in the magnetic polarizability of the neutron

NASA Astrophysics Data System (ADS)

Hall, J. M. M.; Leinweber, D. B.; Young, R. D.

2014-03-01

There has been much progress in the experimental measurement of the electric and magnetic polarizabilities of the nucleon. Similarly, lattice QCD simulations have recently produced dynamical QCD results for the magnetic polarizability of the neutron approaching the chiral regime. In order to compare the lattice simulations with experiment, calculation of partial quenching and finite-volume effects is required prior to an extrapolation in quark mass to the physical point. These dependencies are described using chiral effective field theory. Corrections to the partial quenching effects associated with the sea-quark-loop electric charges are estimated by modeling corrections to the pion cloud. These are compared to the uncorrected lattice results. In addition, the behavior of the finite-volume corrections as a function of pion mass is explored. Box sizes of approximately 7 fm are required to achieve a result within 5% of the infinite-volume result at the physical pion mass. A variety of extrapolations are shown at different box sizes, providing a benchmark to guide future lattice QCD calculations of the magnetic polarizabilities. A relatively precise value for the physical magnetic polarizability of the neutron is presented, βn=1.93(11)stat(11)sys×10-4 fm3, which is in agreement with current experimental results.

QCD topological susceptibility from the nonlocal chiral quark model

NASA Astrophysics Data System (ADS)

Nam, Seung-Il; Kao, Chung-Wen

2017-06-01

We investigate the quantum chromodynamics (QCD) topological susceptibility χ by using the semi-bosonized nonlocal chiral-quark model (SB-NLχQM) for the leading large- N c contributions. This model is based on the liquid-instanton QCD-vacuum configuration, in which SU(3) flavor symmetry is explicitly broken by the finite current-quark mass ( m u,d, m s) ≈ (5, 135) MeV. To compute χ, we derive the local topological charge-density operator Q t( x) from the effective action of SB-NLχQM. We verify that the derived expression for χ in our model satisfies the Witten- Veneziano (WV) and the Leutwyler-Smilga (LS) formulae, and the Crewther theorem in the chiral limit by construction. Once the average instanton size and the inter-instanton distance are fixed with ρ¯ = 1/3 fm and R¯ = 1 fm, respectively, all the other parameters are determined self-consistently within the model. We obtain χ = (167.67MeV)4, which is comparable with the empirical value χ = (175±5MeV)4 whereas it turns out that χ QL = (194.30MeV)4 in the quenched limit. Thus, we conclude that the value of χ will be reduced around 10 20% by the dynamical-quark contribution.

Deep Exclusive Pseudoscalar Meson Production at Jefferson Lab Hall C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basnet, Samip

2017-09-01

Measurements of exclusive meson production are a useful tool in the study of hadronic structure. In particular, one can discern the relevant degrees of freedom at different distance scales through these studies. In the transition region between low momentum transfer (where a description of hadronic degrees of freedom in terms of effective hadronic Lagrangians is valid) and high momentum transfer (where the degrees of freedom are quarks and gluons), the predictive power of Quantum Chromodynamics (QCD), the theory of the strong interaction, is limited due to the absence of a complete solution. Thus, one has to rely upon experimental datamore » from the non-perturbative intermediate-energy regime to thoroughly understand the onset of perturbative QCD (pQCD) as the momentum transfer is increased. This work involves two deep exclusive meson electroproduction experiments at Jefferson Lab (JLab). The p(e,e'pi+)n reaction is studied at fixed Q^2 and W of 2.5 GeV2 and 2.0 GeV, respectively, while varying the four momentum transfer to the nucleon -t from 0.2 to 2.1 GeV2 . As -t is increased, the hadronic interaction scale is reduced independently of the observation scale of the virtual photon, providing valuable information about the hard- scattering process in general. The data was taken at JLab Hall C in 2003, as a part of the experiment E01-004, Fpi-2, using the High Momentum Spectrometer (HMS) and Short Orbit Spectrometer (SOS), and in this work, the results of the differential cross section analysis are presented and compared to prior data, as well as two theoretical models. Using these results over a wide -t range, the transition from hard to soft QCD is also studied. In addition, the p(e,e'K+)Lambda(Sigma0) reactions are also studied. Despite their importance in elucidating the reaction mechanism underlying strangeness production, we still do not have complete understanding of these reactions above the resonance region. The experiment, E12- 09-011, intends to perform, for the first time, a full Rosenbluth (L/T/LT/TT) separation of p(e,e'K+)Lambda(Sigma0) cross sections above the resonance region using the newly upgraded standard equipment, Super High Momentum Spectrometer (SHMS) at JLab Hall C. The separated data will allow us to better understand the Kaon production reaction mechanism and the hard-soft QCD transition in exclusive processes. The kinematic settings being studied in the experiment ranges from Q^2 of 0.4 to 5.5 GeV2, W of 2.3 to 3.1 GeV, and -t of 0.06 to 0.53 GeV2. Here, the results from some pre-experimental studies with regards to estimations of singles rates as well as real and accidental coincidence rates are presented, using two different models. The implications of these projections on the runplan for the experiment are also discussed.« less

Fuzzy Dark Matter from Infrared Confining Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davoudiasl, Hooman; Murphy, Christopher W.

A very light boson of mass O ( 10 - 22 ) eV may potentially be a viable dark matter (DM) candidate, which can avoid phenomenological problems associated with cold DM. Such “fuzzy DM (FDM)” may naturally be an axion with a decay constant f a ~ 1 0 16 – 1 0 18 GeV and a mass m a ~ μ 2 / f a with μ ~ 1 0 2 eV . Here, we propose a concrete model, where μ arises as a dynamical scale from infrared confining dynamics, analogous to QCD. This model is an alternative tomore » the usual approach of generating μ through string theoretic instanton effects. We outline the features of this scenario that result from various cosmological constraints. We also found that those constraints are suggestive of a period of mild of inflation, perhaps from a strong first order phase transition, that reheats the standard model (SM) sector only. A typical prediction of our scenario, broadly speaking, is a larger effective number of neutrinos compared to the SM value N eff ≈ 3 , as inferred from precision measurements of the cosmic microwave background. Some of the new degrees of freedom may be identified as “sterile neutrinos,” which may be required to explain certain neutrino oscillation anomalies. Thus, aspects of our scenario could be testable in terrestrial experiments, which is a novelty of our FDM model.« less

Fuzzy Dark Matter from Infrared Confining Dynamics

DOE PAGES

Davoudiasl, Hooman; Murphy, Christopher W.

2017-04-03

A very light boson of mass O ( 10 - 22 ) eV may potentially be a viable dark matter (DM) candidate, which can avoid phenomenological problems associated with cold DM. Such “fuzzy DM (FDM)” may naturally be an axion with a decay constant f a ~ 1 0 16 – 1 0 18 GeV and a mass m a ~ μ 2 / f a with μ ~ 1 0 2 eV . Here, we propose a concrete model, where μ arises as a dynamical scale from infrared confining dynamics, analogous to QCD. This model is an alternative tomore » the usual approach of generating μ through string theoretic instanton effects. We outline the features of this scenario that result from various cosmological constraints. We also found that those constraints are suggestive of a period of mild of inflation, perhaps from a strong first order phase transition, that reheats the standard model (SM) sector only. A typical prediction of our scenario, broadly speaking, is a larger effective number of neutrinos compared to the SM value N eff ≈ 3 , as inferred from precision measurements of the cosmic microwave background. Some of the new degrees of freedom may be identified as “sterile neutrinos,” which may be required to explain certain neutrino oscillation anomalies. Thus, aspects of our scenario could be testable in terrestrial experiments, which is a novelty of our FDM model.« less

QCD In Extreme Conditions

NASA Astrophysics Data System (ADS)

Wilczek, Frank

Introduction Symmetry and the Phenomena of QCD Apparent and Actual Symmetries Asymptotic Freedom Confinement Chiral Symmetry Breaking Chiral Anomalies and Instantons High Temperature QCD: Asymptotic Properties Significance of High Temperature QCD Numerical Indications for Quasi-Free Behavior Ideas About Quark-Gluon Plasma Screening Versus Confinement Models of Chiral Symmetry Breaking More Refined Numerical Experiments High-Temperature QCD: Phase Transitions Yoga of Phase Transitions and Order Parameters Application to Glue Theories Application to Chiral Transitions Close Up on Two Flavors A Genuine Critical Point! (?) High-Density QCD: Methods Hopes, Doubts, and Fruition Another Renormalization Group Pairing Theory Taming the Magnetic Singularity High-Density QCD: Color-Flavor Locking and Quark-Hadron Continuity Gauge Symmetry (Non)Breaking Symmetry Accounting Elementary Excitations A Modified Photon Quark-Hadron Continuity Remembrance of Things Past More Quarks Fewer Quarks and Reality

Recent development in lattice QCD studies for three-nucleon forces

NASA Astrophysics Data System (ADS)

Doi, Takumi; HAL QCD Collaboration

2014-09-01

The direct determination of nuclear forces from QCD has been one of the most desirable challenges in nuclear physics. Recently, a first-principles lattice QCD determination is becoming possible by a novel theoretical method, HAL QCD method, in which Nambu-Bethe-Salpeter (NBS) wave functions are utilized. In this talk, I will focus on the study of three-nucleon forces in HAL QCD method by presenting the recent theoretical/numerical development.

Transverse momentum dependent parton distribution and fragmentation functions with QCD evolution

NASA Astrophysics Data System (ADS)

Aybat, S. Mert; Rogers, Ted C.

2011-06-01

We assess the current phenomenological status of transverse momentum dependent (TMD) parton distribution functions (PDFs) and fragmentation functions (FFs) and study the effect of consistently including perturbative QCD (pQCD) evolution. Our goal is to initiate the process of establishing reliable, QCD-evolved parametrizations for the TMD PDFs and TMD FFs that can be used both to test TMD factorization and to search for evidence of the breakdown of TMD factorization that is expected for certain processes. In this article, we focus on spin-independent processes because they provide the simplest illustration of the basic steps and can already be used in direct tests of TMD factorization. Our calculations are based on the Collins-Soper-Sterman (CSS) formalism, supplemented by recent theoretical developments which have clarified the precise definitions of the TMD PDFs and TMD FFs needed for a valid TMD-factorization theorem. Starting with these definitions, we numerically generate evolved TMD PDFs and TMD FFs using as input existing parametrizations for the collinear PDFs, collinear FFs, nonperturbative factors in the CSS factorization formalism, and recent fixed-scale fits. We confirm that evolution has important consequences, both qualitatively and quantitatively, and argue that it should be included in future phenomenological studies of TMD functions. Our analysis is also suggestive of extensions to processes that involve spin-dependent functions such as the Boer-Mulders, Sivers, or Collins functions, which we intend to pursue in future publications. At our website [http://projects.hepforge.org/tmd/], we have made available the tables and calculations needed to obtain the TMD parametrizations presented herein.

Naturalizing supersymmetry with a two-field relaxion mechanism

DOE PAGES

Evans, Jason L.; Gherghetta, Tony; Nagata, Natsumi; ...

2016-09-26

We present a supersymmetric version of a two-field relaxion model that naturalizes tuned versions of supersymmetry. This arises from a relaxion mechanism that does not depend on QCD dynamics and where the relaxion potential barrier height is controlled by a second axion-like field. During the cosmological evolution, the relaxion rolls with a nonzero value that breaks supersymmetry and scans the soft supersymmetric mass terms. Electroweak symmetry is broken after the soft masses become of order the supersymmetric Higgs mass term and causes the relaxion to stop rolling for superpartner masses up to ~10 9 GeV. This can explain the tuningmore » in supersymmetric models, including split-SUSY models, while preserving the QCD axion solution to the strong CP problem. Furthermore, besides predicting two very weakly-coupled axion-like particles, the supersymmetric spectrum may contain an extra Goldstino, which could be a viable dark matter candidate.« less

Three-body decays B →ϕ (ρ )K γ in perturbative QCD approach

NASA Astrophysics Data System (ADS)

Wang, Chao; Liu, Jing-Bin; Li, Hsiang-nan; Lü, Cai-Dian

2018-02-01

We study the three-body radiative decays B →ϕ (ρ )K γ induced by a flavor-changing neutral current in the perturbative QCD approach. Pseudoscalar-vector (P V ) distribution amplitudes (DAs) are introduced for the final-state ϕ K (ρ K ) pair to capture important infrared dynamics in the region with a small P V -pair invariant mass. The dependence of these P V DAs on the parton momentum fraction is parametrized in terms of the Gegenbauer polynomials, and the dependence on the meson momentum fraction is derived through their normalizations to timelike P V form factors. In addition to the dominant electromagnetic penguin, the subleading chromomagnetic penguin, quark-loop and annihilation diagrams are also calculated. After determining the P V DAs from relevant branching-ratio data, the direct C P asymmetries and decay spectra in the P V -pair invariant mass are predicted for each B →ϕ (ρ )K γ mode.

Electromagnetic corrections to the hadronic vacuum polarization of the photon within QEDL and QEDM

NASA Astrophysics Data System (ADS)

Bussone, Andrea; Della Morte, Michele; Janowski, Tadeusz

2018-03-01

We compute the leading QED corrections to the hadronic vacuum polarization (HVP) of the photon, relevant for the determination of leptonic anomalous magnetic moments, al. We work in the electroquenched approximation and use dynamical QCD configurations generated by the CLS initiative with two degenerate flavors of nonperturbatively O(a)-improved Wilson fermions. We consider QEDL and QEDM to deal with the finite-volume zero modes. We compare results for the Wilson loops with exact analytical determinations. In addition we make sure that the volumes and photon masses used in QEDM are such that the correct dispersion relation is reproduced by the energy levels extracted from the charged pions two-point functions. Finally we compare results for pion masses and the HVP between QEDL and QEDM. For the vacuum polarization, corrections with respect to the pure QCD case, at fixed pion masses, turn out to be at the percent level.

Progress on Complex Langevin simulations of a finite density matrix model for QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bloch, Jacques; Glesaan, Jonas; Verbaarschot, Jacobus

We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to intended theory with dynamical quarks. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. We study the effect of gauge cooling on the Dirac eigenvalue distribution and time evolution of the norm for various cooling norms, which were specifically designed to remove the pathologies of the complex Langevin evolution. The cooling is further supplementedmore » with a shifted representation for the random matrices. Unfortunately, none of these modifications generate a substantial improvement on the complex Langevin evolution and the final results still do not agree with the analytical predictions.« less

Determination of s- and p-wave I = 1/2 Kπ scattering amplitudes in Nf = 2 + 1 lattice QCD

NASA Astrophysics Data System (ADS)

Brett, Ruairí; Bulava, John; Fallica, Jacob; Hanlon, Andrew; Hörz, Ben; Morningstar, Colin

2018-07-01

The elastic I = 1 / 2, s- and p-wave kaon-pion scattering amplitudes are calculated using a single ensemble of anisotropic lattice QCD gauge field configurations with Nf = 2 + 1 flavors of dynamical Wilson-clover fermions at mπ = 230 MeV. A large spatial extent of L = 3.7 fm enables a good energy resolution while partial wave mixing due to the reduced symmetries of the finite volume is treated explicitly. The p-wave amplitude is well described by a Breit-Wigner shape with parameters mK* /mπ = 3.808 (18) and gK*Kπ BW = 5.33 (20) which are insensitive to the inclusion of d-wave mixing and variation of the s-wave parametrization. An effective range description of the near-threshold s-wave amplitude yields mπa0 = - 0.353 (25).

Sivers and Boer-Mulders observables from lattice QCD

NASA Astrophysics Data System (ADS)

Musch, B. U.; Hägler, Ph.; Engelhardt, M.; Negele, J. W.; Schäfer, A.

2012-05-01

We present a first calculation of transverse momentum-dependent nucleon observables in dynamical lattice QCD employing nonlocal operators with staple-shaped, “process-dependent” Wilson lines. The use of staple-shaped Wilson lines allows us to link lattice simulations to TMD effects determined from experiment, and, in particular, to access nonuniversal, naively time-reversal odd TMD observables. We present and discuss results for the generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS and DY cases. The effect of staple-shaped Wilson lines on T-even observables is studied for the generalized tensor charge and a generalized transverse shift related to the worm-gear function g1T. We emphasize the dependence of these observables on the staple extent and the Collins-Soper evolution parameter. Our numerical calculations use an nf=2+1 mixed action scheme with domain wall valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV.

Light meson form factors at high Q2 from lattice QCD

NASA Astrophysics Data System (ADS)

Koponen, Jonna; Zimermmane-Santos, André; Davies, Christine; Lepage, G. Peter; Lytle, Andrew

2018-03-01

Measurements and theoretical calculations of meson form factors are essential for our understanding of internal hadron structure and QCD, the dynamics that bind the quarks in hadrons. The pion electromagnetic form factor has been measured at small space-like momentum transfer |q2| < 0.3 GeV2 by pion scattering from atomic electrons and at values up to 2.5 GeV2 by scattering electrons from the pion cloud around a proton. On the other hand, in the limit of very large (or infinite) Q2 = -q2, perturbation theory is applicable. This leaves a gap in the intermediate Q2 where the form factors are not known. As a part of their 12 GeV upgrade Jefferson Lab will measure pion and kaon form factors in this intermediate region, up to Q2 of 6 GeV2. This is then an ideal opportunity for lattice QCD to make an accurate prediction ahead of the experimental results. Lattice QCD provides a from-first-principles approach to calculate form factors, and the challenge here is to control the statistical and systematic uncertainties as errors grow when going to higher Q2 values. Here we report on a calculation that tests the method using an ηs meson, a 'heavy pion' made of strange quarks, and also present preliminary results for kaon and pion form factors. We use the nf = 2 + 1 + 1 ensembles made by the MILC collaboration and Highly Improved Staggered Quarks, which allows us to obtain high statistics. The HISQ action is also designed to have small dicretisation errors. Using several light quark masses and lattice spacings allows us to control the chiral and continuum extrapolation and keep systematic errors in check. Warning, no authors found for 2018EPJWC.17506016.

Higgs pair production at NLO QCD for CP-violating Higgs sectors

NASA Astrophysics Data System (ADS)

Gröber, R.; Mühlleitner, M.; Spira, M.

2017-12-01

Higgs pair production through gluon fusion is an important process at the LHC to test the dynamics underlying electroweak symmetry breaking. Higgs sectors beyond the Standard Model (SM) can substantially modify this cross section through novel couplings not present in the SM or the on-shell production of new heavy Higgs bosons that subsequently decay into Higgs pairs. CP violation in the Higgs sector is important for the explanation of the observed matter-antimatter asymmetry through electroweak baryogenesis. In this work we compute the next-to-leading order (NLO) QCD corrections in the heavy top quark limit, including the effects of CP violation in the Higgs sector. We choose the effective theory (EFT) approach, which provides a rather model-independent way to explore New Physics (NP) effects by adding dimension-6 operators, both CP-conserving and CP-violating ones, to the SM Lagrangian. Furthermore, we perform the computation within a specific UV-complete model and choose as benchmark model the general 2-Higgs-Doublet Model with CP violation, the C2HDM. Depending on the dimension-6 coefficients, the relative NLO QCD corrections are affected by several per cent through the new CP-violating operators. This is also the case for SM-like Higgs pair production in the C2HDM, while the relative QCD corrections in the production of heavier C2HDM Higgs boson pairs deviate more strongly from the SM case. The absolute cross sections both in the EFT and the C2HDM can be modified by more than an order of magnitude. In particular, in the C2HDM the resonant production of Higgs pairs can by far exceed the SM cross section.

Magnetic bion condensation: A new mechanism of confinement and mass gap in four dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uensal, Mithat

In recent work, we derived the long-distance confining dynamics of certain QCD-like gauge theories formulated on small S{sup 1}xR{sup 3} based on symmetries, an index theorem, and Abelian duality. Here, we give the microscopic derivation. The solution reveals a new mechanism of confinement in QCD(adj) in the regime where we have control over both perturbative and nonperturbative aspects. In particular, consider SU(2) QCD(adj) theory with 1{<=}n{sub f}{<=}4 Majorana fermions, a theory which undergoes gauge symmetry breaking at small S{sup 1}. If the magnetic charge of the Bogomol'nyi-Prasad-Sommerfield (BPS) monopole is normalized to unity, we show that confinement occurs due tomore » condensation of objects with magnetic charge 2, not 1. Because of index theorems, we know that such an object cannot be a two identical monopole configuration. Its net topological charge must vanish, and hence it must be topologically indistinguishable from the perturbative vacuum. We construct such non-self-dual topological excitations, the magnetically charged, topologically null molecules of a BPS monopole and KK antimonopole, which we refer to as magnetic bions. An immediate puzzle with this proposal is the apparent Coulomb repulsion between the BPS-KK pair. An attraction which overcomes the Coulomb repulsion between the two is induced by 2n{sub f}-fermion exchange. Bion condensation is also the mechanism of confinement in N=1 SYM on the same four-manifold. The SU(N) generalization hints a possible hidden integrability behind nonsupersymmetric QCD of affine Toda type, and allows us to analytically compute the mass gap in the gauge sector. We currently do not know the extension to R{sup 4}.« less

The current matrix elements from HAL QCD method

NASA Astrophysics Data System (ADS)

Watanabe, Kai; Ishii, Noriyoshi

2018-03-01

HAL QCD method is a method to construct a potential (HAL QCD potential) that reproduces the NN scattering phase shift faithful to the QCD. The HAL QCD potential is obtained from QCD by eliminating the degrees of freedom of quarks and gluons and leaving only two particular hadrons. Therefor, in the effective quantum mechanics of two nucleons defined by HAL QCD potential, the conserved current consists not only of the nucleon current but also an extra current originating from the potential (two-body current). Though the form of the two-body current is closely related to the potential, it is not straight forward to extract the former from the latter. In this work, we derive the the current matrix element formula in the quantum mechanics defined by the HAL QCD potential. As a first step, we focus on the non-relativistic case. To give an explicit example, we consider a second quantized non-relativistic two-channel coupling model which we refer to as the original model. From the original model, the HAL QCD potential for the open channel is constructed by eliminating the closed channel in the elastic two-particle scattering region. The current matrix element formula is derived by demanding the effective quantum mechanics defined by the HAL QCD potential to respond to the external field in the same way as the original two-channel coupling model.

Forward di-jet production in p+Pb collisions in the small-x improved TMD factorization framework

DOE PAGES

van Hameren, A.; Kotko, P.; Kutak, K.; ...

2016-12-12

We study the production of forward di-jets in proton-lead and proton-proton collisions at the Large Hadron Collider. Such configurations, with both jets produced in the forward direction, impose a dilute-dense asymmetry which allows to probe the gluon density of the lead or proton target at small longitudinal momentum fractions. Even though the jet momenta are always much bigger than the saturation scale of the target, Qs, the transverse momentum imbalance of the di-jet system may be either also much larger than Qs, or of the order Qs, implying that the small-x QCD dynamics involved is either linear or non-linear, respectively.more » The small-x improved TMD factorization framework deals with both situations in the same formalism. In the latter case, which corresponds to nearly back-to-back jets, we find that saturation effects induce a significant suppression of the forward di-jet azimuthal correlations in proton-lead versus proton-proton collisions.« less

Forward di-jet production in p+Pb collisions in the small-x improved TMD factorization framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Hameren, A.; Kotko, P.; Kutak, K.

We study the production of forward di-jets in proton-lead and proton-proton collisions at the Large Hadron Collider. Such configurations, with both jets produced in the forward direction, impose a dilute-dense asymmetry which allows to probe the gluon density of the lead or proton target at small longitudinal momentum fractions. Even though the jet momenta are always much bigger than the saturation scale of the target, Qs, the transverse momentum imbalance of the di-jet system may be either also much larger than Qs, or of the order Qs, implying that the small-x QCD dynamics involved is either linear or non-linear, respectively.more » The small-x improved TMD factorization framework deals with both situations in the same formalism. In the latter case, which corresponds to nearly back-to-back jets, we find that saturation effects induce a significant suppression of the forward di-jet azimuthal correlations in proton-lead versus proton-proton collisions.« less

B{sub K} with two flavors of dynamical overlap fermions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, S.; Riken BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973; Fukaya, H.

2008-05-01

We present a two-flavor QCD calculation of B{sub K} on a 16{sup 3}x32 lattice at a{approx}0.12 fm (or equivalently a{sup -1}=1.67 GeV). Both valence and sea quarks are described by the overlap fermion formulation. The matching factor is calculated nonperturbatively with the so-called RI/MOM scheme. We find that the lattice data are well described by the next-to-leading order (NLO) partially quenched chiral perturbation theory (PQChPT) up to around a half of the strange quark mass (m{sub s}{sup phys}/2). The data at quark masses heavier than m{sub s}{sup phys}/2 are fitted including a part of next-to-next-to-leading order terms. We obtain B{submore » K}{sup MS}(2 GeV)=0.537(4)(40), where the first error is statistical and the second is an estimate of systematic uncertainties from finite volume, fixing topology, the matching factor, and the scale setting.« less

QCD dirac operator at nonzero chemical potential: lattice data and matrix model.

PubMed

Akemann, Gernot; Wettig, Tilo

2004-03-12

Recently, a non-Hermitian chiral random matrix model was proposed to describe the eigenvalues of the QCD Dirac operator at nonzero chemical potential. This matrix model can be constructed from QCD by mapping it to an equivalent matrix model which has the same symmetries as QCD with chemical potential. Its microscopic spectral correlations are conjectured to be identical to those of the QCD Dirac operator. We investigate this conjecture by comparing large ensembles of Dirac eigenvalues in quenched SU(3) lattice QCD at a nonzero chemical potential to the analytical predictions of the matrix model. Excellent agreement is found in the two regimes of weak and strong non-Hermiticity, for several different lattice volumes.

Lattice QCD Calculations in Nuclear Physics towards the Exascale

NASA Astrophysics Data System (ADS)

Joo, Balint

2017-01-01

The combination of algorithmic advances and new highly parallel computing architectures are enabling lattice QCD calculations to tackle ever more complex problems in nuclear physics. In this talk I will review some computational challenges that are encountered in large scale cold nuclear physics campaigns such as those in hadron spectroscopy calculations. I will discuss progress in addressing these with algorithmic improvements such as multi-grid solvers and software for recent hardware architectures such as GPUs and Intel Xeon Phi, Knights Landing. Finally, I will highlight some current topics for research and development as we head towards the Exascale era This material is funded by the U.S. Department of Energy, Office Of Science, Offices of Nuclear Physics, High Energy Physics and Advanced Scientific Computing Research, as well as the Office of Nuclear Physics under contract DE-AC05-06OR23177.

Interference in the gg→h→γγ On-Shell Rate and the Higgs Boson Total Width.

PubMed

Campbell, John; Carena, Marcela; Harnik, Roni; Liu, Zhen

2017-11-03

We consider interference between the Higgs signal and QCD background in gg→h→γγ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the standard model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss possible width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly constrain widths of order tens of MeV.

Predicted and Totally Unexpected in the Energy Frontier Opened by LHC

NASA Astrophysics Data System (ADS)

Zichichi, Antonino

2011-01-01

Opening lectures. Sid Coleman and Erice / A. Zichichi. Remembering Sidney Coleman / G.'t Hooft -- Predicted signals at LHC. From extra-dimensions: Multiple branes scenarios and their contenders / I. Antoniadis. Predicted signals at the LHC from technicolor / A. Martin. The one-parameter model at LHC / J. Maxin, E. Mayes and D. V. Nanopoulos. How supercritical string cosmology affects LHC / D. V. Nanopoulos. High scale physics connection to LHC data / P. Nath. Predicted signatures at the LHC from U(I) extensions of the standard model / P. Nath -- Hot theoretical topics. Progress on the ultraviolet finiteness of supergravity / Z. Bern. Status of supersymmetry: Foundations and applications / S. Ferrara and A. Marrani. Quantum gravity from dynamical triangulation / R. Loll. Status of superstring and M-theory / J. H. Schwarz. Some effects of instantons in QCD / G.'t Hooft. Crystalline gravity / G.'t Hooft -- QCD problems. Strongly coupled gauge theories / R. Kenway. Strongly interacting matter at high energy density / L. McLerran. Seminars on specialized topics. The nature and the mass of neutrinos. Majorana vs. Dirac / A. Bettini. The anomalous spin distributions in the nucleon / A. Deshpande. Results from PHENIX at RHIC / M. J. Tannenbaum -- Highlights from laboratories. Highlights from RHIC / Y. Akiba. News from the Gran Sasso Underground Laboratory / E. Coccia. Highlights from TRIUMF / N. S. Lockyer. Highlights from Superkamiokande / M. Koshiba. Highlights from Fermilab / P. J. Oddone. Highlights from IHEP / Y. Wang -- Special sessions for new talents. Fake supergravity and black hole evolution / A. Gnecchi. Track-based improvement in the jet transverse momentum resolution for ATLAS / Z. Marshall. Searches for supersymmetric dark matter with XENON / K. Ni. Running of Newton's constant and quantum gravitational effects / D. Reeb.

Axial-vector form factors of the nucleon from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Rajan; Jang, Yong-Chull; Lin, Huey-Wen

In this paper, we present results for the form factors of the isovector axial vector current in the nucleon state using large scale simulations of lattice QCD. The calculations were done using eight ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2 + 1 + 1 dynamical flavors. These ensembles span three lattice spacings a ≈ 0.06 , 0.09, and 0.12 fm and light-quark masses corresponding to the pion masses M π ≈ 135, 225, and 310 MeV. High-statistics estimates allow us to quantify systematic uncertainties in the extraction of G A (Q 2)more » and the induced pseudoscalar form factor G P(Q 2) . We perform a simultaneous extrapolation in the lattice spacing, lattice volume and light-quark masses of the axial charge radius r A data to obtain physical estimates. Using the dipole ansatz to fit the Q 2 behavior we obtain r A | dipole = 0.49(3) fm , which corresponds to M A = 1.39(9) GeV , and is consistent with M A = 1.35(17) GeV obtained by the miniBooNE collaboration. The estimate obtained using the z -expansion is r A | z - expansion = 0.46(6) fm, and the combined result is r A | combined = 0.48(4) fm. Analysis of the induced pseudoscalar form factor G P (Q 2) yields low estimates for g* P and g πNN compared to their phenomenological values. To understand these, we analyze the partially conserved axial current (PCAC) relation by also calculating the pseudoscalar form factor. Lastly, we find that these low values are due to large deviations in the PCAC relation between the three form factors, and in the pion-pole dominance hypothesis.« less

Axial-vector form factors of the nucleon from lattice QCD

DOE PAGES

Gupta, Rajan; Jang, Yong-Chull; Lin, Huey-Wen; ...

2017-12-04

In this paper, we present results for the form factors of the isovector axial vector current in the nucleon state using large scale simulations of lattice QCD. The calculations were done using eight ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2 + 1 + 1 dynamical flavors. These ensembles span three lattice spacings a ≈ 0.06 , 0.09, and 0.12 fm and light-quark masses corresponding to the pion masses M π ≈ 135, 225, and 310 MeV. High-statistics estimates allow us to quantify systematic uncertainties in the extraction of G A (Q 2)more » and the induced pseudoscalar form factor G P(Q 2) . We perform a simultaneous extrapolation in the lattice spacing, lattice volume and light-quark masses of the axial charge radius r A data to obtain physical estimates. Using the dipole ansatz to fit the Q 2 behavior we obtain r A | dipole = 0.49(3) fm , which corresponds to M A = 1.39(9) GeV , and is consistent with M A = 1.35(17) GeV obtained by the miniBooNE collaboration. The estimate obtained using the z -expansion is r A | z - expansion = 0.46(6) fm, and the combined result is r A | combined = 0.48(4) fm. Analysis of the induced pseudoscalar form factor G P (Q 2) yields low estimates for g* P and g πNN compared to their phenomenological values. To understand these, we analyze the partially conserved axial current (PCAC) relation by also calculating the pseudoscalar form factor. Lastly, we find that these low values are due to large deviations in the PCAC relation between the three form factors, and in the pion-pole dominance hypothesis.« less

Measurements of the vector boson production with the ATLAS detector

NASA Astrophysics Data System (ADS)

Lapertosa, A.

2018-01-01

Measurements of the Drell-Yan production of W and Z bosons at the LHC provide a benchmark of our understanding of perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration has performed new high precision measurements at a center-of-mass energy of 7 TeV. The measurements are performed for W+, W- and Z bosons integrated and as a function of the boson or lepton rapidity and the Z mass. Unprecedented precision is reached and strong constraints on Parton Distribution Functions, in particular the strange density are found. Z boson cross sections are also measured at center-of-mass energies of 8 TeV and 13 TeV, and cross-section ratios to the top-quark pair production have been derived. This ratio measurement leads to a cancellation of systematic effects and allows for a high precision comparison to the theory predictions. The production of jets in association with vector bosons is a further important process to study perturbative QCD in a multi-scale environment. The ATLAS collaboration has performed new measurements of Z boson plus jets cross sections, differential in several kinematic variables, in proton-proton collision data taken at a center-of-mass energy of 13 TeV. The measurements are compared to state-of-the art theory predictions. They are sensitive to higher-order pQCD effects, probe flavour and mass schemes and can be used to constrain the proton structure. In addition, a new measurement of the splitting scales of the kt jet-clustering algorithm for final states containing a Z boson candidate at a center-of-mass energy of 8 TeV is presented.

Up quark mass in lattice QCD with three light dynamical quarks and implications for strong CP invariance.

PubMed

Nelson, Daniel R; Fleming, George T; Kilcup, Gregory W

2003-01-17

A standing mystery in the standard model is the unnatural smallness of the strong CP violating phase. A massless up quark has long been proposed as one potential solution. A lattice calculation of the constants of the chiral Lagrangian essential for the determination of the up quark mass, 2alpha(8)-alpha(5), is presented. We find 2alpha(8)-alpha(5)=0.29+/-0.18, which corresponds to m(u)/m(d)=0.410+/-0.036. This is the first such calculation using a physical number of dynamical light quarks, N(f)=3.

QCD for Postgraduates (2/5)

ScienceCinema

Zanderighi, Giulia

2018-05-21

Modern QCD - Lecture 2 We will start discussing the matter content of the theory and revisit the experimental measurements that led to the discovery of quarks. We will then consider a classic QCD observable, the R-ratio, and use it to illustrate the appearance of UV divergences and the need to renormalize the coupling constant of QCD. We will then discuss asymptotic freedom and confinement. Finally, we will examine a case where soft and collinear infrared divergences appear, will discuss the soft approximation in QCD and will introduce the concept of infrared safe jets.

Nucleon-nucleon interactions via Lattice QCD: Methodology. HAL QCD approach to extract hadronic interactions in lattice QCD

NASA Astrophysics Data System (ADS)

Aoki, Sinya

2013-07-01

We review the potential method in lattice QCD, which has recently been proposed to extract nucleon-nucleon interactions via numerical simulations. We focus on the methodology of this approach by emphasizing the strategy of the potential method, the theoretical foundation behind it, and special numerical techniques. We compare the potential method with the standard finite volume method in lattice QCD, in order to make pros and cons of the approach clear. We also present several numerical results for nucleon-nucleon potentials.

Renormalization of Extended QCD2

NASA Astrophysics Data System (ADS)

Fukaya, Hidenori; Yamamura, Ryo

2015-10-01

Extended QCD (XQCD), proposed by Kaplan [D. B. Kaplan, arXiv:1306.5818], is an interesting reformulation of QCD with additional bosonic auxiliary fields. While its partition function is kept exactly the same as that of original QCD, XQCD naturally contains properties of low-energy hadronic models. We analyze the renormalization group flow of 2D (X)QCD, which is solvable in the limit of a large number of colors N_c, to understand what kind of roles the auxiliary degrees of freedom play and how the hadronic picture emerges in the low-energy region.

θ and the η ' in large N supersymmetric QCD

DOE PAGES

Dine, Michael; Draper, Patrick; Stephenson-Haskins, Laurel; ...

2017-05-22

Here, we study the large N θ dependence and the η' potential in supersymmetric QCD with small soft SUSY-breaking terms. Known exact results in SUSY QCD are found to reflect a variety of expectations from large N perturbation theory, including the presence of branches and the behavior of theories with matter (both with N f << N and N f ~ N ). But, there are also striking departures from ordinary QCD and the conventional large N description: instanton effects, when under control, are not exponentially suppressed at large N , and branched structure in supersymmetric QCD is always associatedmore » with approximate discrete symmetries. We suggest that these differences motivate further study of large N QCD on the lattice.« less

Matrix theory for baryons: an overview of holographic QCD for nuclear physics.

PubMed

Aoki, Sinya; Hashimoto, Koji; Iizuka, Norihiro

2013-10-01

We provide, for non-experts, a brief overview of holographic QCD (quantum chromodynamics) and a review of the recent proposal (Hashimoto et al 2010 (arXiv:1003.4988[hep-th])) of a matrix-like description of multi-baryon systems in holographic QCD. Based on the matrix model, we derive the baryon interaction at short distances in multi-flavor holographic QCD. We show that there is a very universal repulsive core of inter-baryon forces for a generic number of flavors. This is consistent with a recent lattice QCD analysis for Nf = 2, 3 where the repulsive core looks universal. We also provide a comparison of our results with the lattice QCD and the operator product expansion analysis.

Exploring Partonic Structure of Hadrons Using ab initio Lattice QCD Calculations

DOE PAGES

Ma, Yan-Qing; Qiu, Jian-Wei

2018-01-10

Following our previous proposal, we construct a class of good "lattice cross sections" (LCSs), from which we can study the partonic structure of hadrons from ab initio lattice QCD calculations. These good LCSs, on the one hand, can be calculated directly in lattice QCD, and on the other hand, can be factorized into parton distribution functions (PDFs) with calculable coefficients, in the same way as QCD factorization for factorizable hadronic cross sections. PDFs could be extracted from QCD global analysis of the lattice QCD generated data of LCSs. In conclusion, we also show that the proposed functions for lattice QCDmore » calculation of PDFs in the literature are special cases of these good LCSs.« less

QCD studies in ep collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, W.H.

1997-06-01

These lectures describe QCD physics studies over the period 1992--1996 from data taken with collisions of 27 GeV electrons and positrons with 820 GeV protons at the HERA collider at DESY by the two general-purpose detectors H1 and ZEUS. The focus of these lectures is on structure functions and jet production in deep inelastic scattering, photoproduction, and diffraction. The topics covered start with a general introduction to HERA and ep scattering. Structure functions are discussed. This includes the parton model, scaling violation, and the extraction of F{sub 2}, which is used to determine the gluon momentum distribution. Both low andmore » high Q{sup 2} regimes are discussed. The low Q{sup 2} transition from perturbative QCD to soft hadronic physics is examined. Jet production in deep inelastic scattering to measure {alpha}{sub s}, and in photoproduction to study resolved and direct photoproduction, is also presented. This is followed by a discussion of diffraction that begins with a general introduction to diffraction in hadronic collisions and its relation to ep collisions, and moves on to deep inelastic scattering, where the structure of diffractive exchange is studied, and in photoproduction, where dijet production provides insights into the structure of the Pomeron. 95 refs., 39 figs.« less

The scalar glueball operator, the a-theorem, and the onset of conformality

NASA Astrophysics Data System (ADS)

Nunes da Silva, T.; Pallante, E.; Robroek, L.

2018-03-01

We show that the anomalous dimension γG of the scalar glueball operator contains information on the mechanism that leads to the onset of conformality at the lower edge of the conformal window in a non-Abelian gauge theory. In particular, it distinguishes whether the merging of an UV and an IR fixed point - the simplest mechanism associated to a conformal phase transition and preconformal scaling - does or does not occur. At the same time, we shed light on new analogies between QCD and its supersymmetric version. In SQCD, we derive an exact relation between γG and the mass anomalous dimension γm, and we prove that the SQCD exact beta function is incompatible with merging as a consequence of the a-theorem; we also derive the general conditions that the latter imposes on the existence of fixed points, and prove the absence of an UV fixed point at nonzero coupling above the conformal window of SQCD. Perhaps not surprisingly, we then show that an exact relation between γG and γm, fully analogous to SQCD, holds for the massless Veneziano limit of large-N QCD. We argue, based on the latter relation, the a-theorem, perturbation theory and physical arguments, that the incompatibility with merging may extend to QCD.

A non-perturbative exploration of the high energy regime in Nf=3 QCD. ALPHA Collaboration

NASA Astrophysics Data System (ADS)

Dalla Brida, Mattia; Fritzsch, Patrick; Korzec, Tomasz; Ramos, Alberto; Sint, Stefan; Sommer, Rainer

2018-05-01

Using continuum extrapolated lattice data we trace a family of running couplings in three-flavour QCD over a large range of scales from about 4 to 128 GeV. The scale is set by the finite space time volume so that recursive finite size techniques can be applied, and Schrödinger functional (SF) boundary conditions enable direct simulations in the chiral limit. Compared to earlier studies we have improved on both statistical and systematic errors. Using the SF coupling to implicitly define a reference scale 1/L_0≈ 4 GeV through \\bar{g}^2(L_0) =2.012, we quote L_0 Λ ^{N_f=3}_{{\\overline{MS}}} =0.0791(21). This error is dominated by statistics; in particular, the remnant perturbative uncertainty is negligible and very well controlled, by connecting to infinite renormalization scale from different scales 2^n/L_0 for n=0,1,\\ldots ,5. An intermediate step in this connection may involve any member of a one-parameter family of SF couplings. This provides an excellent opportunity for tests of perturbation theory some of which have been published in a letter (ALPHA collaboration, M. Dalla Brida et al. in Phys Rev Lett 117(18):182001, 2016). The results indicate that for our target precision of 3 per cent in L_0 Λ ^{N_f=3}_{{\\overline{MS}}}, a reliable estimate of the truncation error requires non-perturbative data for a sufficiently large range of values of α _s=\\bar{g}^2/(4π ). In the present work we reach this precision by studying scales that vary by a factor 2^5= 32, reaching down to α _s≈ 0.1. We here provide the details of our analysis and an extended discussion.

JPRS Report, Science & Technology, China.

DTIC Science & Technology

1992-08-20

nature of the nuclear medium. QCD [quantum chromodynamic] lattice gauge calculations have predicted the existence of a new phase of the nuclear medium...and A106 octahedra; the atoms Nb and Al are located at the vacants of the octahedra, but a fraction of Al in the lattice is replaced by Nb atoms, and...superlattice and quantum-well lattice dynamics and electron structure, transport processes in superlattice low-dimensionality systems, semiconductor

Two-baryon systems from HAL QCD method and the mirage in the temporal correlation of the direct method

NASA Astrophysics Data System (ADS)

Iritani, Takumi

2018-03-01

Both direct and HAL QCD methods are currently used to study the hadron interactions in lattice QCD. In the direct method, the eigen-energy of two-particle is measured from the temporal correlation. Due to the contamination of excited states, however, the direct method suffers from the fake eigen-energy problem, which we call the "mirage problem," while the HAL QCD method can extract information from all elastic states by using the spatial correlation. In this work, we further investigate systematic uncertainties of the HAL QCD method such as the quark source operator dependence, the convergence of the derivative expansion of the non-local interaction kernel, and the single baryon saturation, which are found to be well controlled. We also confirm the consistency between the HAL QCD method and the Lüscher's finite volume formula. Based on the HAL QCD potential, we quantitatively confirm that the mirage plateau in the direct method is indeed caused by the contamination of excited states.

The QCD mass gap and quark deconfinement scales as mass bounds in strong gravity

NASA Astrophysics Data System (ADS)

Burikham, Piyabut; Harko, Tiberiu; Lake, Matthew J.

2017-11-01

Though not a part of mainstream physics, Salam's theory of strong gravity remains a viable effective model for the description of strong interactions in the gauge singlet sector of QCD, capable of producing particle confinement and asymptotic freedom, but not of reproducing interactions involving SU(3) color charge. It may therefore be used to explore the stability and confinement of gauge singlet hadrons, though not to describe scattering processes that require color interactions. It is a two-tensor theory of both strong interactions and gravity, in which the strong tensor field is governed by equations formally identical to the Einstein equations, apart from the coupling parameter, which is of order 1 {GeV}^{-1}. We revisit the strong gravity theory and investigate the strong gravity field equations in the presence of a mixing term which induces an effective strong cosmological constant, Λ f. This introduces a strong de Sitter radius for strongly interacting fermions, producing a confining bubble, which allows us to identify Λ f with the `bag constant' of the MIT bag model, B ˜eq 2 × 10^{14} {g} {cm}^{-3}. Assuming a static, spherically symmetric geometry, we derive the strong gravity TOV equation, which describes the equilibrium properties of compact hadronic objects. From this, we determine the generalized Buchdahl inequalities for a strong gravity `particle', giving rise to upper and lower bounds on the mass/radius ratio of stable, compact, strongly interacting objects. We show, explicitly, that the existence of the lower mass bound is induced by the presence of Λ _f, producing a mass gap, and that the upper bound corresponds to a deconfinement phase transition. The physical implications of our results for holographic duality in the context of the AdS/QCD and dS/QCD correspondences are also discussed.

Precise Predictions for Dijet Production at the LHC

NASA Astrophysics Data System (ADS)

Currie, J.; Gehrmann-De Ridder, A.; Gehrmann, T.; Glover, E. W. N.; Huss, A.; Pires, J.

2017-10-01

We present the calculation of dijet production, doubly differential in dijet mass mj j and rapidity difference |y*|, at leading color in all partonic channels at next-to-next-to-leading order (NNLO) in perturbative QCD. We consider the long-standing problems associated with scale choice for dijet production at next-to-leading order (NLO) and investigate the impact of including the NNLO contribution. We find that the NNLO theory provides reliable predictions, even when using scale choices that display pathological behavior at NLO. We choose the dijet invariant mass as the theoretical scale on the grounds of perturbative convergence and residual scale variation and compare the predictions to the ATLAS 7 TeV 4.5 fb-1 data.

Probing parton dynamics of QCD matter with Ω and ϕ production

NASA Astrophysics Data System (ADS)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; di Ruzza, B.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, S.; Gupta, A.; Guryn, W.; Hamad, A. I.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, X.; Huang, B.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Jentsch, A.; Jia, J.; Jiang, K.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z. H.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, X.; Li, Y.; Li, W.; Lin, T.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, R.; Ma, G. L.; Ma, Y. G.; Ma, L.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Matis, H. S.; McDonald, D.; McKinzie, S.; Meehan, K.; Mei, J. C.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, S.; Raniwala, R.; Ray, R. L.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, B.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Summa, B.; Sun, Z.; Sun, X. M.; Sun, Y.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, F.; Wang, G.; Wang, J. S.; Wang, H.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xin, K.; Xu, Y. F.; Xu, Q. H.; Xu, N.; Xu, H.; Xu, Z.; Xu, J.; Yang, S.; Yang, Y.; Yang, Y.; Yang, C.; Yang, Y.; Yang, Q.; Ye, Z.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, X. P.; Zhang, Y.; Zhang, J.; Zhang, J.; Zhang, S.; Zhang, S.; Zhang, Z.; Zhang, J. B.; Zhao, F.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

2016-02-01

We present measurements of Ω and ϕ production at midrapidity from Au+Au collisions at nucleon-nucleon center-of-mass energies √{sN N}=7.7 , 11.5 , 19.6 , 27, and 39 GeV by the STAR experiment at the BNL Relativistic Heavy Ion Collider (RHIC). Motivated by the coalescence formation mechanism for these strange hadrons, we study the ratios of N (Ω-+Ω¯+) /[2 N (ϕ ) ] . These ratios as a function of transverse momentum pT fall on a consistent trend at high collision energies, but start to show deviations in peripheral collisions at √{sN N}=19.6 , 27, and 39 GeV, and in central collisions at 11.5 GeV in the intermediate pT region of 2.4 -3.6 GeV/c . We further evaluate empirically the strange quark pT distributions at hadronization by studying the Ω /ϕ ratios scaled by the number of constituent quarks (NCQ). The NCQ-scaled Ω /ϕ ratios show a suppression of strange quark production in central collisions at 11.5 GeV compared to √{sN N}≥19.6 GeV. The shapes of the presumably thermal strange quark distributions in 0-60% most central collisions at 7.7 GeV show significant deviations from those in 0-10% most central collisions at higher energies. These features suggest that there is likely a change of the underlying strange quark dynamics in the transition from quark matter to hadronic matter at collision energies below 19.6 GeV.

Probing parton dynamics of QCD matter with Ω and Φ production

DOE PAGES

Adamczyk, L.

2016-02-24

In this paper, we present measurements of Ω and Φ production at midrapidity from Au+Au collisions at nucleon-nucleon center-of-mass energies √sNN = 7.7, 11.5, 19.6 , 27, and 39 GeV by the STAR experiment at the BNL Relativistic Heavy Ion Collider (RHIC). Motivated by the coalescence formation mechanism for these strange hadrons, we study the ratios of N(Ω - +more » $$\\overline{Ω}$$ +) / [2N (Φ)] . These ratios as a function of transverse momentum p T fall on a consistent trend at high collision energies, but start to show deviations in peripheral collisions at √sNN = 19.6, 27, and 39 GeV, and in central collisions at 11.5 GeV in the intermediate p T region of 2.4 - 3.6 GeV/ . We further evaluate empirically the strange quark p T distributions at hadronization by studying the Ω/Φ ratios scaled by the number of constituent quarks (NCQ). The NCQ-scaled Ω/Φ ratios show a suppression of strange quark production in central collisions at 11.5 GeV compared to √sNN ≥ 19.6 GeV. The shapes of the presumably thermal strange quark distributions in 0–60% most central collisions at 7.7 GeV show significant deviations from those in 0–10% most central collisions at higher energies. Lastly, these features suggest that there is likely a change of the underlying strange quark dynamics in the transition from quark matter to hadronic matter at collision energies below 19.6 GeV.« less

Determination of the strong coupling constant \\varvec{α _s (m_Z)} in next-to-next-to-leading order QCD using H1 jet cross section measurements

NASA Astrophysics Data System (ADS)

Andreev, V.; Baghdasaryan, A.; Begzsuren, K.; Belousov, A.; Bertone, V.; Bolz, A.; Boudry, V.; Brandt, G.; Brisson, V.; Britzger, D.; Buniatyan, A.; Bylinkin, A.; Bystritskaya, L.; Campbell, A. J.; Cantun Avila, K. B.; Cerny, K.; Chekelian, V.; Contreras, J. G.; Cvach, J.; Currie, J.; Dainton, J. B.; Daum, K.; Diaconu, C.; Dobre, M.; Dodonov, V.; Eckerlin, G.; Egli, S.; Elsen, E.; Favart, L.; Fedotov, A.; Feltesse, J.; Fleischer, M.; Fomenko, A.; Gabathuler, E.; Gayler, J.; Gehrmann, T.; Ghazaryan, S.; Goerlich, L.; Gogitidze, N.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Gwenlan, C.; Haidt, D.; Henderson, R. C. W.; Hladkỳ, J.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Huss, A.; Jacquet, M.; Janssen, X.; Jung, A. W.; Jung, H.; Kapichine, M.; Katzy, J.; Kiesling, C.; Klein, M.; Kleinwort, C.; Kogler, R.; Kostka, P.; Kretzschmar, J.; Krücker, D.; Krüger, K.; Landon, M. P. J.; Lange, W.; Laycock, P.; Lebedev, A.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Malinovski, E.; Martyn, H.-U.; Maxfield, S. J.; Mehta, A.; Meyer, A. B.; Meyer, H.; Meyer, J.; Mikocki, S.; Morozov, A.; Müller, K.; Naumann, Th.; Newman, P. R.; Niebuhr, C.; Niehues, J.; Nowak, G.; Olsson, J. E.; Ozerov, D.; Pascaud, C.; Patel, G. D.; Perez, E.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Plačakytė, R.; Polifka, R.; Rabbertz, K.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Šálek, D.; Sankey, D. P. C.; Sauter, M.; Sauvan, E.; Schmitt, S.; Schoeffel, L.; Schöning, A.; Sefkow, F.; Shushkevich, S.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Steder, M.; Stella, B.; Straumann, U.; Sutton, M. R.; Sykora, T.; Thompson, P. D.; Traynor, D.; Truöl, P.; Tsakov, I.; Tseepeldorj, B.; Valkárová, A.; Vallée, C.; Van Mechelen, P.; Vazdik, Y.; Wegener, D.; Wünsch, E.; Žáček, J.; Zhang, Z.; Žlebčík, R.; Zohrabyan, H.; Zomer, F.

2017-11-01

The strong coupling constant α _s is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic ep scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of α _s (m_Z) at the Z-boson mass m_Z are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be α _s (m_Z) =0.1157 (20)_exp (29)_th. Complementary, α _s (m_Z) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value α _s (m_Z) =0.1142 (28)_tot obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.

Nucleon QCD sum rules in the instanton medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryskin, M. G.; Drukarev, E. G., E-mail: drukarev@pnpi.spb.ru; Sadovnikova, V. A.

2015-09-15

We try to find grounds for the standard nucleon QCD sum rules, based on a more detailed description of the QCD vacuum. We calculate the polarization operator of the nucleon current in the instanton medium. The medium (QCD vacuum) is assumed to be a composition of the small-size instantons and some long-wave gluon fluctuations. We solve the corresponding QCD sum rule equations and demonstrate that there is a solution with the value of the nucleon mass close to the physical one if the fraction of the small-size instantons contribution is w{sub s} ≈ 2/3.

Large $N$ approach to kaon decays and mixing 28 years later: $$\\Delta I = 1/2$$ rule, $$\\hat B_K$$ and $$\\Delta M_K$$

DOE PAGES

Buras, Andrzej J.; Gérard, Jean -Marc; Bardeen, William A.

2014-05-20

We review and update our results for K → π π decays and K⁰- K¯⁰ mixing obtained by us in the 1980s within an approach based on the dual representation of QCD as a theory of weakly interacting mesons for large N colours. In our analytic approach the dynamics behind the enhancement of ReA 0 and suppression of ReA 2, the so-called ΔI = 1/2 rule for K → π π decays, has a simple structure: the usual octet enhancement through quark-gluon renormalization group evolution down to the scales O(1 GeV) is continued as a meson evolution down to zeromore » momentum scales at which the factorization of hadronic matrix elements is at work. The inclusion of lowest-lying vector meson contributions in addition to the pseudoscalar ones and of Wilson coefficients in a momentum scheme improves significantly the matching between quark-gluon and meson evolutions. In particular, the anomalous dimension matrix governing the meson evolution exhibits the structure of the known anomalous dimension matrix in the quark-gluon evolution. The recent results on ReA 2 and ReA 0 from the RBC-UKQC collaboration give support for our approach. In particular, the signs of the two main contractions found numerically by these authors follow uniquely from our analytic approach. At NLO in 1/N we obtain R = ReA 0/ReA 2= 16.0±1.5 which amounts to an order of magnitude enhancement over the strict large N limit value √2. QCD penguins contribute at 15% level to this result. We also find B^ K = 0.73± 0.02, with the smallness of 1/N corrections to the large N value B^ K = 3/4 resulting within our approach from an approximate cancellation between pseudoscalar and vector meson one-loop contributions. We summarize the status of ΔM K in this approach.« less

NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

LIN H.-W.; OHTA, S.

2006-10-02

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments {sub u-d}/{submore » {Delta}u-{Delta}d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is a{sup -1} {approx} 1.6GeV and the spatial volume is about (3.0fm){sup 3}. Even with preliminary statistics of 25-30 gauge configurations, the ratios g{sub A}/g{sub V} and {sub u-d}/{sub {Delta}u-{Delta}d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d{sub 1}, though yet to be renormalized, appears small in both sets.« less

Interference in the g g → h → γ γ On-Shell Rate and the Higgs Boson Total Width

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, John; Carena, Marcela; Harnik, Roni

We consider interference between the Higgs signal and QCD background inmore » $$gg\\rightarrow h \\rightarrow \\gamma\\gamma$$ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the Standard Model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss potential width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly probe widths of order tens of MeV.« less

Medium-Induced QCD Cascade: Democratic Branching and Wave Turbulence

NASA Astrophysics Data System (ADS)

Blaizot, J.-P.; Iancu, E.; Mehtar-Tani, Y.

2013-08-01

We study the average properties of the gluon cascade generated by an energetic parton propagating through a quark-gluon plasma. We focus on the soft, medium-induced emissions which control the energy transport at large angles with respect to the leading parton. We show that the effect of multiple branchings is important. In contrast with what happens in a usual QCD cascade in vacuum, medium-induced branchings are quasidemocratic, with offspring gluons carrying sizable fractions of the energy of their parent gluon. This results in an efficient mechanism for the transport of energy toward the medium, which is akin to wave turbulence with a scaling spectrum ˜1/ω. We argue that the turbulent flow may be responsible for the excess energy carried by very soft quanta, as revealed by the analysis of the dijet asymmetry observed in Pb-Pb collisions at the LHC.

ππ P-wave resonant scattering from lattice QCD

NASA Astrophysics Data System (ADS)

Paul, Srijit; Alexandrou, Constantia; Leskovec, Luka; Meinel, Stefan; Negele, John W.; Petschlies, Marcus; Pochinsky, Andrew; Rendon Suzuki, Jesus Gumaro; Syritsyn, Sergey

2018-03-01

We present a high-statistics analysis of the ρ resonance in ππ scattering, using 2 + 1 flavors of clover fermions at a pion mass of approximately 320 MeV and a lattice size of approximately 3:6 fm. The computation of the two-point functions are carried out using combinations of forward, sequential, and stochastic propagators. For the extraction of the ρ-resonance parameters, we compare different fit methods and demonstrate their consistency. For the ππ scattering phase shift, we consider different Breit-Wigner parametrizations and also investigate possible nonresonant contributions. We find that the minimal Breit-Wigner model is suffcient to describe our data, and obtain amρ = 0:4609(16)stat(14)sys and gρππ = 5:69(13)stat(16)sys. In our comparison with other lattice QCD results, we consider the dimensionless ratios amρ/amN and amπ/amN to avoid scale setting ambiguities.

Stiff self-interacting strings at high temperature QCD

NASA Astrophysics Data System (ADS)

S Bakry, A.; Chen, X.; Deliyergiyev, M.; Galal, A.; Khalaf, A.; M Pengming, P.

2018-03-01

We investigate the implications of Nambu-Goto (NG), Lüscher Weisz (LW) and Polyakov-Kleinert (PK) effective string actions for the Casimir energy and the width of the quantum delocalization of the string in 4-dim pure SU(3) Yang-Mills lattice gauge theory. At a temperature closer to the critical point T/Tc=0.9, we found that the next to leading-order (NLO) contributions from the expansion of the NG string in addition to the boundary terms in LW action to decrease the deviations from the lattice data in the intermediate distance scales for both the quark-antiquark QQ̅ potential and broadening of the color tube compared to the free string approximation. We conjecture possible stiffness of the QCD string through studying the effects of extrinsic curvature term in PK action and find a good fitting behavior for the lattice Monte-Carlo data at both long and intermediate quark separations regions.

Leading-twist parton distribution amplitudes of S-wave heavy-quarkonia

DOE PAGES

Ding, Minghui; Gao, Fei; Chang, Lei; ...

2015-12-08

Here, the leading-twist parton distribution amplitudes (PDAs) of ground-state 1S 0 and 3S 1 cc¯- and bb¯quarkonia are calculated using a symmetry-preserving continuum treatment of the meson bound-state problem which unifies the properties of these heavy-quark systems with those of light-quark bound-states, including QCD's Goldstone modes. Analysing the evolution of 1S 0 and 3S 1 PDAs with current-quark mass, m^ q, increasing away from the chiral limit, it is found that in all cases there is a value of m^ q for which the PDA matches the asymptotic form appropriate to QCD's conformal limit and hence is insensitive to changesmore » in renormalisation scale, ζ. This mass lies just above that associated with the s-quark. At current-quark masses associated with heavy-quarkonia, on the other hand, the PDAs are piecewise convex–concave–convex.« less

MS overline -on-shell quark mass relation up to four loops in QCD and a general SU (N ) gauge group

NASA Astrophysics Data System (ADS)

Marquard, Peter; Smirnov, Alexander V.; Smirnov, Vladimir A.; Steinhauser, Matthias; Wellmann, David

2016-10-01

We compute the relation between heavy quark masses defined in the modified minimal subtraction and the on-shell schemes. Detailed results are presented for all coefficients of the SU (Nc) color factors. The reduction of the four-loop on-shell integrals is performed for a general QCD gauge parameter. Altogether there are about 380 master integrals. Some of them are computed analytically, others with high numerical precision using Mellin-Barnes representations, and the rest numerically with the help of FIESTA. We discuss in detail the precise numerical evaluation of the four-loop master integrals. Updated relations between various short-distance masses and the MS ¯ quark mass to next-to-next-to-next-to-leading order accuracy are provided for the charm, bottom and top quarks. We discuss the dependence on the renormalization and factorization scale.

Additional strange hadrons from QCD thermodynamics and strangeness freezeout in heavy ion collisions.

PubMed

Bazavov, A; Ding, H-T; Hegde, P; Kaczmarek, O; Karsch, F; Laermann, E; Maezawa, Y; Mukherjee, Swagato; Ohno, H; Petreczky, P; Schmidt, C; Sharma, S; Soeldner, W; Wagner, M

2014-08-15

We compare lattice QCD results for appropriate combinations of net strangeness fluctuations and their correlations with net baryon number fluctuations with predictions from two hadron resonance gas (HRG) models having different strange hadron content. The conventionally used HRG model based on experimentally established strange hadrons fails to describe the lattice QCD results in the hadronic phase close to the QCD crossover. Supplementing the conventional HRG with additional, experimentally uncharted strange hadrons predicted by quark model calculations and observed in lattice QCD spectrum calculations leads to good descriptions of strange hadron thermodynamics below the QCD crossover. We show that the thermodynamic presence of these additional states gets imprinted in the yields of the ground-state strange hadrons leading to a systematic 5-8 MeV decrease of the chemical freeze-out temperatures of ground-state strange baryons.

$B$- and $D$-meson leptonic decay constants from four-flavor lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazavov, A.; Bernard, C.; Brown, N.

We calculate the leptonic decay constants of heavy-light pseudoscalar mesons with charm and bottom quarks in lattice quantum chromodynamics on four-flavor QCD gauge-field configurations with dynamicalmore » $u$, $d$, $s$, and $c$ quarks. We analyze over twenty isospin-symmetric ensembles with six lattice spacings down to $$a\\approx 0.03$$~fm and several values of the light-quark mass down to the physical value $$\\frac{1}{2}(m_u+m_d)$$. We employ the highly-improved staggered-quark (HISQ) action for the sea and valence quarks; on the finest lattice spacings, discretization errors are sufficiently small that we can calculate the $B$-meson decay constants with the HISQ action for the first time directly at the physical $b$-quark mass. We obtain the most precise determinations to-date of the $D$- and $B$-meson decay constants and their ratios, $$f_{D^+} = 212.6 (0.5)$$~MeV, $$f_{D_s} = 249.8(0.4)$$~MeV, $$f_{D_s}/f_{D^+} = 1.1749(11)$$, $$f_{B^+} = 189.4(1.4)$$~MeV, $$f_{B_s} = 230.7(1.2)$$~MeV, $$f_{B_s}/f_{B^+} = 1.2180(49)$$, where the errors include statistical and all systematic uncertainties. Our results for the $B$-meson decay constants are three times more precise than the previous best lattice-QCD calculations, and bring the QCD errors in the Standard-Model predictions for the rare leptonic decays $$\\overline{\\mathcal{B}}(B_s \\to \\mu^+\\mu^-) = 3.65(11) \\times 10^{-9}$$, $$\\overline{\\mathcal{B}}(B^0 \\to \\mu^+\\mu^-) = 1.00(3) \\times 10^{-11}$$, and $$\\overline{\\mathcal{B}}(B^0 \\to \\mu^+\\mu^-)/\\overline{\\mathcal{B}}(B_s \\to \\mu^+\\mu^-) = 0.00264(7)$$ to well below other sources of uncertainty. As a byproduct of our analysis, we also update our previously published results for the light-quark-mass ratios and the scale-setting quantities $$f_{p4s}$$, $$M_{p4s}$$, and $$R_{p4s}$$. We obtain the most precise lattice-QCD determination to date of the ratio $$f_{K^+}/f_{\\pi^+} = 1.1950(^{+15}_{-22})$$~MeV.« less

Heavy-flavor production and medium properties in high-energy nuclear collisions --What next?

DOE PAGES

Aarts, G.; Aichelin, J.; Allton, C.; ...

2017-05-16

Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Some recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop Tomography of the Quark-Gluon Plasma with Heavy Quarks, which was held in October 2016 in Leiden, The Netherlands. Here, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profoundmore » knowledge of the dynamical properties of the quark-gluon plasma.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Yan-Qing; Qiu, Jian-Wei

Following our previous proposal, we construct a class of good "lattice cross sections" (LCSs), from which we can study the partonic structure of hadrons from ab initio lattice QCD calculations. These good LCSs, on the one hand, can be calculated directly in lattice QCD, and on the other hand, can be factorized into parton distribution functions (PDFs) with calculable coefficients, in the same way as QCD factorization for factorizable hadronic cross sections. PDFs could be extracted from QCD global analysis of the lattice QCD generated data of LCSs. In conclusion, we also show that the proposed functions for lattice QCDmore » calculation of PDFs in the literature are special cases of these good LCSs.« less

The quark condensate in multi-flavour QCD – planar equivalence confronting lattice simulations

DOE PAGES

Armoni, Adi; Shifman, Mikhail; Shore, Graham; ...

2015-02-01

Planar equivalence between the large N limits of N=1 Super Yang–Mills (SYM) theory and a variant of QCD with fermions in the antisymmetric representation is a powerful tool to obtain analytic non-perturbative results in QCD itself. In particular, it allows the quark condensate for N=3 QCD with quarks in the fundamental representation to be inferred from exact calculations of the gluino condensate in N=1 SYM. In this paper, we review and refine our earlier predictions for the quark condensate in QCD with a general number nf of flavours and confront these with lattice results.

QCD tests in $$p\\bar{p}$$ collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huth, John E.; Mangano, Michelangelo L.

1993-02-01

We review the status of QCD tests in high energy p-pbar collisions. Contents: i) Introduction ii) QCD in Hadronic Collisions iii) Jet Production iv) Heavy Flavour Production v) W and Z Production vi) Direct Photons.

Parton distributions and lattice QCD calculations: A community white paper

NASA Astrophysics Data System (ADS)

Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred; Orginos, Kostas; Rojo, Juan; Accardi, Alberto; Alexandrou, Constantia; Bacchetta, Alessandro; Bozzi, Giuseppe; Chen, Jiunn-Wei; Collins, Sara; Cooper-Sarkar, Amanda; Constantinou, Martha; Del Debbio, Luigi; Engelhardt, Michael; Green, Jeremy; Gupta, Rajan; Harland-Lang, Lucian A.; Ishikawa, Tomomi; Kusina, Aleksander; Liu, Keh-Fei; Liuti, Simonetta; Monahan, Christopher; Nadolsky, Pavel; Qiu, Jian-Wei; Schienbein, Ingo; Schierholz, Gerrit; Thorne, Robert S.; Vogelsang, Werner; Wittig, Hartmut; Yuan, C.-P.; Zanotti, James

2018-05-01

In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this document we present an overview of lattice-QCD and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. This document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.

Strangeness S =-1 hyperon-nucleon interactions: Chiral effective field theory versus lattice QCD

NASA Astrophysics Data System (ADS)

Song, Jing; Li, Kai-Wen; Geng, Li-Sheng

2018-06-01

Hyperon-nucleon interactions serve as basic inputs to studies of hypernuclear physics and dense (neutron) stars. Unfortunately, a precise understanding of these important quantities has lagged far behind that of the nucleon-nucleon interaction due to lack of high-precision experimental data. Historically, hyperon-nucleon interactions are either formulated in quark models or meson exchange models. In recent years, lattice QCD simulations and chiral effective field theory approaches start to offer new insights from first principles. In the present work, we contrast the state-of-the-art lattice QCD simulations with the latest chiral hyperon-nucleon forces and show that the leading order relativistic chiral results can already describe the lattice QCD data reasonably well. Given the fact that the lattice QCD simulations are performed with pion masses ranging from the (almost) physical point to 700 MeV, such studies provide a useful check on both the chiral effective field theory approaches as well as lattice QCD simulations. Nevertheless more precise lattice QCD simulations are eagerly needed to refine our understanding of hyperon-nucleon interactions.

Extension of the HAL QCD approach to inelastic and multi-particle scatterings in lattice QCD

NASA Astrophysics Data System (ADS)

Aoki, S.

We extend the HAL QCD approach, with which potentials between two hadrons can be obtained in QCD at energy below inelastic thresholds, to inelastic and multi-particle scatterings. We first derive asymptotic behaviors of the Nambu-Bethe-Salpeter (NBS) wave function at large space separations for systems with more than 2 particles, in terms of the one-shell $T$-matrix consrainted by the unitarity of quantum field theories. We show that its asymptotic behavior contains phase shifts and mixing angles of $n$ particle scatterings. This property is one of the essential ingredients of the HAL QCD scheme to define "potential" from the NBS wave function in quantum field theories such as QCD. We next construct energy independent but non-local potentials above inelastic thresholds, in terms of these NBS wave functions. We demonstrate an existence of energy-independent coupled channel potentials with a non-relativistic approximation, where momenta of all particles are small compared with their own masses. Combining these two results, we can employ the HAL QCD approach also to investigate inelastic and multi-particle scatterings.

Physics Opportunity with an Electron-Ion Collider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rossi, Patrizia

2016-12-01

Understanding the emergence of nucleons and nuclei and their interactions from the properties and dynamics of quarks and gluons in Quantum Chromodynamics (QCD) is a fundamental and compelling goal of nuclear science. A high-energy, high-luminosity polarized electron-ion collider (EIC) will be needed to explore and advance many aspects of QCD studies in the gluon dominated regions in nucleon and nuclei. The federal Nuclear Science Advisory Committee unanimously approved a high-energy electro-ion collider to explore a new frontier in physics research. In fact, the committee calls the collider the country's next "highest priority" in new facility construction, and is one ofmore » four main recommendations contained in its 2015 Long Range Plan for Nuclear Science. Two proposals for the EIC are being considered in the U.S.: one each at Jefferson Laboratory (JLab) and at Brookhaven National Laboratory (BNL). An overview of the physics opportunities an EIC presents to the nuclear science community in future decades is presented.« less

Partial restoration of chiral symmetry in a confining string

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharzeev, Dmitri E.; Loshaj, F.

2014-08-01

Here, we attempt to describe the interplay of confinement and chiral symmetry breaking in QCD by using the string model. We argue that in the quasi-Abelian picture of confinement based on the condensation of magnetic monopoles and the dual Meissner effect, the world sheet dynamics of the confining string can be effectively described by the 1+1 dimensional massless electrodynamics, which is exactly soluble. The transverse plane distribution of the chromoelectric field stretched between the quark and antiquark sources can then be attributed to the fluctuations in the position of the string. The dependence of the chiral condensate in the stringmore » on the (chromo-)electric field can be evaluated analytically, and is determined by the chiral anomaly and the θ-vacuum structure. Moreover, our picture allows us to predict the distribution of the chiral condensate in the plane transverse to the axis connecting the quark and antiquark. This prediction is compared to the lattice QCD results; a good agreement is found.« less

The hadronic vacuum polarization contribution to the muon g - 2 from lattice QCD

NASA Astrophysics Data System (ADS)

Morte, M. Della; Francis, A.; Gülpers, V.; Herdoíza, G.; von Hippel, G.; Horch, H.; Jäger, B.; Meyer, H. B.; Nyffeler, A.; Wittig, H.

2017-10-01

We present a calculation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment, a μ hvp , in lattice QCD employing dynamical up and down quarks. We focus on controlling the infrared regime of the vacuum polarization function. To this end we employ several complementary approaches, including Padé fits, time moments and the time-momentum representation. We correct our results for finite-volume effects by combining the Gounaris-Sakurai parameterization of the timelike pion form factor with the Lüscher formalism. On a subset of our ensembles we have derived an upper bound on the magnitude of quark-disconnected diagrams and found that they decrease the estimate for a μ hvp by at most 2%. Our final result is {a}_{μ}^{hvp} = (654 ± {32}{^{-23}}^{+21}) ·10-10, where the first error is statistical, and the second denotes the combined systematic uncertainty. Based on our findings we discuss the prospects for determining a μ hvp with sub-percent precision.

Holographic QCD phase diagram with critical point from Einstein-Maxwell-dilaton dynamics

NASA Astrophysics Data System (ADS)

Knaute, J.; Yaresko, R.; Kämpfer, B.

2018-03-01

Supplementing the holographic Einstein-Maxwell-dilaton model of [1,2] by input of lattice QCD data for 2 + 1 flavors and physical quark masses for the equation of state and quark number susceptibility at zero baryo-chemical potential we explore the resulting phase diagram over the temperature-chemical potential plane. A first-order phase transition sets in at a temperature of about 112 MeV and a baryo-chemical potential of 612 MeV. We estimate the accuracy of the critical point position in the order of approximately 5-8% by considering parameter variations and different low-temperature asymptotics for the second-order quark number susceptibility. The critical pressure as a function of the temperature has a positive slope, i.e. the entropy per baryon jumps up when crossing the phase border line from larger values of temperature/baryo-chemical potential, thus classifying the phase transition as a gas-liquid one. The updated holographic model exhibits in- and outgoing isentropes in the vicinity of the first-order phase transition.

Distribution law of the Dirac eigenmodes in QCD

NASA Astrophysics Data System (ADS)

Catillo, Marco; Glozman, Leonid Ya.

2018-04-01

The near-zero modes of the Dirac operator are connected to spontaneous breaking of chiral symmetry in QCD (SBCS) via the Banks-Casher relation. At the same time, the distribution of the near-zero modes is well described by the Random Matrix Theory (RMT) with the Gaussian Unitary Ensemble (GUE). Then, it has become a standard lore that a randomness, as observed through distributions of the near-zero modes of the Dirac operator, is a consequence of SBCS. The higher-lying modes of the Dirac operator are not affected by SBCS and are sensitive to confinement physics and related SU(2)CS and SU(2NF) symmetries. We study the distribution of the near-zero and higher-lying eigenmodes of the overlap Dirac operator within NF = 2 dynamical simulations. We find that both the distributions of the near-zero and higher-lying modes are perfectly described by GUE of RMT. This means that randomness, while consistent with SBCS, is not a consequence of SBCS and is linked to the confining chromo-electric field.

π π → π γ * amplitude and the resonant ρ → π γ * transition from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briceño, Raúl A.; Dudek, Jozef J.; Edwards, Robert G.

2016-06-01

We present a determination of themore » $P$-wave $$\\pi\\pi\\to\\pi\\gamma^\\star$$ transition amplitude from lattice quantum chromodynamics. Matrix elements of the vector current in a finite-volume are extracted from three-point correlation functions, and from these we determine the infinite-volume amplitude using a generalization of the Lellouch-L\\"uscher formalism. We determine the amplitude for a range of discrete values of the $$\\pi\\pi$$ energy and virtuality of the photon, and observe the expected dynamical enhancement due to the $$\\rho$$ resonance. Describing the energy dependence of the amplitude, we are able to analytically continue into the complex energy plane and from the residue at the $$\\rho$$ pole extract the $$\\rho\\to\\gamma^\\star\\pi$$ transition form factor. This calculation, at $$m_\\pi\\approx 400$$~MeV, is the first time a form factor of a hadron resonance has been calculated within a first-principles approach to QCD.« less

Roper resonance and S11(1535) from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

N. Mathur; Y. Chen; S.J. Dong

2005-01-06

Using the constrained curve fitting method and overlap fermions with the lowest pion mass at 180 MeV, we observe that the masses of the first positive and negative parity excited states of the nucleon tend to cross over as the quark masses are taken to the chiral limit. Both results at the physical pion mass agree with the experimental values of the Roper resonance (N{sup 1/2+} (1440)) and S{sub 11} (N{sup 1/2-}(1535)). This is seen for the first time in a lattice QCD calculation. These results are obtained on a quenched Iwasaki 16{sup 3} x 28 lattice with a =more » 0.2 fm. We also extract the ghost {eta}{prime} N states (a quenched artifact) which are shown to decouple from the nucleon interpolation field above m{sub {pi}} {approx} 300 MeV. From the quark mass dependence of these states in the chiral region, we conclude that spontaneously broken chiral symmetry dictates the dynamics of light quarks in the nucleon.« less

Sivers and Boer-Mulders observables from lattice QCD.

DOE Office of Scientific and Technical Information (OSTI.GOV)

B.U. Musch, Ph. Hagler, M. Engelhardt, J.W. Negele, A. Schafer

We present a first calculation of transverse momentum dependent nucleon observables in dynamical lattice QCD employing non-local operators with staple-shaped, 'process-dependent' Wilson lines. The use of staple-shaped Wilson lines allows us to link lattice simulations to TMD effects determined from experiment, and in particular to access non-universal, naively time-reversal odd TMD observables. We present and discuss results for the generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS and DY cases. The effect of staple-shaped Wilson lines on T-even observables is studied for the generalized tensor charge and a generalized transverse shift related to the worm gear function g{submore » 1}T. We emphasize the dependence of these observables on the staple extent and the Collins-Soper evolution parameter. Our numerical calculations use an n{sub f} = 2+1 mixed action scheme with domain wall valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV.« less

QCD constituent counting rules for neutral vector mesons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

QCD constituent counting rules define the scaling behavior of exclusive hadronic scattering and electromagnetic scattering amplitudes at high momentum transfer in terms of the total number of fundamental constituents in the initial and final states participating in the hard subprocess. The scaling laws reflect the twist of the leading Fock state for each hadron and hence the leading operator that creates the composite state from the vacuum. Thus, the constituent counting scaling laws can be used to identify the twist of exotic hadronic candidates such as tetraquarks and pentaquarks. Effective field theories must consistently implement the scaling rules in ordermore » to be consistent with the fundamental theory. Here in this paper, we examine how one can apply constituent counting rules for the exclusive production of one or two neutral vector mesons V 0 in e + e - annihilation, processes in which the V 0 can couple via intermediate photons. In the case of a (narrow) real V 0, the photon virtuality is fixed to a precise value s 1 = m2V 0, thus treating the V 0 as a single fundamental particle. Each real V 0 thus contributes to the constituent counting rules with NV0 = 1 . In effect, the leading operator underlying the V 0 has twist 1. Thus, in the specific physical case of single or double on-shell V 0 production via intermediate photons, the predicted scaling from counting rules coincides with vector-meson dominance (VMD), an effective theory that treats V 0 as an elementary field. However, the VMD prediction fails in the general case where the V 0 is not coupled through an elementary photon field, and then the leading-twist interpolating operator has twist NV 0 = 2 . Analogous effects appear in pp scattering processes.« less

QCD constituent counting rules for neutral vector mesons

NASA Astrophysics Data System (ADS)

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

2018-02-01

QCD constituent counting rules define the scaling behavior of exclusive hadronic scattering and electromagnetic scattering amplitudes at high momentum transfer in terms of the total number of fundamental constituents in the initial and final states participating in the hard subprocess. The scaling laws reflect the twist of the leading Fock state for each hadron and hence the leading operator that creates the composite state from the vacuum. Thus, the constituent counting scaling laws can be used to identify the twist of exotic hadronic candidates such as tetraquarks and pentaquarks. Effective field theories must consistently implement the scaling rules in order to be consistent with the fundamental theory. Here, we examine how one can apply constituent counting rules for the exclusive production of one or two neutral vector mesons V0 in e+e- annihilation, processes in which the V0 can couple via intermediate photons. In the case of a (narrow) real V0, the photon virtuality is fixed to a precise value s1=mV02, thus treating the V0 as a single fundamental particle. Each real V0 thus contributes to the constituent counting rules with NV0=1. In effect, the leading operator underlying the V0 has twist 1. Thus, in the specific physical case of single or double on-shell V0 production via intermediate photons, the predicted scaling from counting rules coincides with vector-meson dominance (VMD), an effective theory that treats V0 as an elementary field. However, the VMD prediction fails in the general case where the V0 is not coupled through an elementary photon field, and then the leading-twist interpolating operator has twist NV 0=2 . Analogous effects appear in p p scattering processes.

QCD constituent counting rules for neutral vector mesons

DOE PAGES

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

2018-02-08

QCD constituent counting rules define the scaling behavior of exclusive hadronic scattering and electromagnetic scattering amplitudes at high momentum transfer in terms of the total number of fundamental constituents in the initial and final states participating in the hard subprocess. The scaling laws reflect the twist of the leading Fock state for each hadron and hence the leading operator that creates the composite state from the vacuum. Thus, the constituent counting scaling laws can be used to identify the twist of exotic hadronic candidates such as tetraquarks and pentaquarks. Effective field theories must consistently implement the scaling rules in ordermore » to be consistent with the fundamental theory. Here in this paper, we examine how one can apply constituent counting rules for the exclusive production of one or two neutral vector mesons V 0 in e + e - annihilation, processes in which the V 0 can couple via intermediate photons. In the case of a (narrow) real V 0, the photon virtuality is fixed to a precise value s 1 = m2V 0, thus treating the V 0 as a single fundamental particle. Each real V 0 thus contributes to the constituent counting rules with NV0 = 1 . In effect, the leading operator underlying the V 0 has twist 1. Thus, in the specific physical case of single or double on-shell V 0 production via intermediate photons, the predicted scaling from counting rules coincides with vector-meson dominance (VMD), an effective theory that treats V 0 as an elementary field. However, the VMD prediction fails in the general case where the V 0 is not coupled through an elementary photon field, and then the leading-twist interpolating operator has twist NV 0 = 2 . Analogous effects appear in pp scattering processes.« less

Light-front field theory in the description of hadrons

NASA Astrophysics Data System (ADS)

Ji, Chueng-Ryong

2017-03-01

We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame and the light-front dynamics and the advantage of the light-front dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify the presence of the delta-function contributions associated with end-point singularities arising from the chiral effective theory calculation. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.

Inclusive parton cross sections in photoproduction and photon structure

NASA Astrophysics Data System (ADS)

Ahmed, T.; Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Baehr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Brasse, F.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Colombo, M.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Delcourt, B.; Del Buono, L.; De Roeck, A.; De Wolf, E. A.; Di Nezza, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Ehrlichmann, H.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gebauer, M.; Gellrich, A.; Genzel, H.; Gerhards, R.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Gonzalez-Pineiro, B.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Hampel, M.; Hanlon, E. M.; Hapke, M.; Haynes, W. J.; Heatherington, J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hildesheim, W.; Hill, P.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Horisberger, R.; Hudgson, V. L.; Huet, Ph.; Hütte, M.; Hufnagel, H.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kant, D.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Krüner-Marquis, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Lanius, P.; Laporte, J.-F.; Lebedev, A.; Leverenz, C.; Levonian, S.; Ley, Ch.; Lindner, A.; Lindström, G.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lohmander, H.; Lomas, J.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Migliori, A.; Mikocki, S.; Milstead, D.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Ozerov, D.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Peppel, E.; Perez, E.; Phillips, J. P.; Pichler, Ch.; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Prosi, R.; Rabbertz, K.; Rädel, G.; Raupach, F.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Rick, H.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Rylko, R.; Sahlmann, N.; Salesch, S. G.; Sanchez, E.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Schwind, A.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Starosta, R.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stiewe, J.; Stösslein, U.; Stolze, K.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Truöl, P.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Van Esch, P.; Van Mechelen, P.; Vartapetian, A.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walker, I. W.; Walther, A.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wright, A. E.; Wünsch, E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zimmer, M.; Zimmermann, W.; Zomer, F.; Zuber, K.; H1 Collaboration

1995-02-01

Photoproduction of 2-jet events is studied with the H1 detector at HERA. Parton cross sections are extracted from the data by an unfolding method using leading order parton-jet correlations of a QCD generator. The gluon distribution in the photon is derived in the fractional momentum range 0.04 ⩽ xγ ⩽ 1 at the average factorization scale 75 GeV 2.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dine, Michael; Draper, Patrick; Stephenson-Haskins, Laurel

Here, we study the large N θ dependence and the η' potential in supersymmetric QCD with small soft SUSY-breaking terms. Known exact results in SUSY QCD are found to reflect a variety of expectations from large N perturbation theory, including the presence of branches and the behavior of theories with matter (both with N f << N and N f ~ N ). But, there are also striking departures from ordinary QCD and the conventional large N description: instanton effects, when under control, are not exponentially suppressed at large N , and branched structure in supersymmetric QCD is always associatedmore » with approximate discrete symmetries. We suggest that these differences motivate further study of large N QCD on the lattice.« less

Update on ɛK with lattice QCD inputs

NASA Astrophysics Data System (ADS)

Jang, Yong-Chull; Lee, Weonjong; Lee, Sunkyu; Leem, Jaehoon

2018-03-01

We report updated results for ɛK, the indirect CP violation parameter in neutral kaons, which is evaluated directly from the standard model with lattice QCD inputs. We use lattice QCD inputs to fix B\\hatk,|Vcb|,ξ0,ξ2,|Vus|, and mc(mc). Since Lattice 2016, the UTfit group has updated the Wolfenstein parameters in the angle-only-fit method, and the HFLAV group has also updated |Vcb|. Our results show that the evaluation of ɛK with exclusive |Vcb| (lattice QCD inputs) has 4.0σ tension with the experimental value, while that with inclusive |Vcb| (heavy quark expansion based on OPE and QCD sum rules) shows no tension.

Cosmological constraints on pseudo-Nambu-Goldstone bosons

NASA Technical Reports Server (NTRS)

Frieman, Joshua A.; Jaffe, Andrew H.

1991-01-01

Particle physics models with pseudo-Nambu-Goldstone bosons (PNGBs) are characterized by two mass scales: a global spontaneous symmetry breaking scale, f, and a soft (explicit) symmetry breaking scale, Lambda. General model insensitive constraints were studied on this 2-D parameter space arising from the cosmological and astrophysical effects of PNGBs. In particular, constraints were studied arising from vacuum misalignment and thermal production of PNGBs, topological defects, and the cosmological effects of PNGB decay products, as well as astrophysical constraints from stellar PNGB emission. Bounds on the Peccei-Quinn axion scale, 10(exp 10) GeV approx. = or less than f sub pq approx. = or less than 10(exp 10) to 10(exp 12) GeV, emerge as a special case, where the soft breaking scale is fixed at Lambda sub QCD approx. = 100 MeV.

Symmetric and anti-symmetric LS hyperon potentials from lattice QCD

NASA Astrophysics Data System (ADS)

Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji; Inoue, Takashi; HAL QCD Collaboration

2014-09-01

We present recent results of odd-parity hyperon-hyperon potentials from lattice QCD. By using HAL QCD method, we generate hyperon-hyperon potentials from Nambu-Bethe-Salpeter (NBS) wave functions generated by lattice QCD simulation in the flavor SU(3) limit. Potentials in the irreducible flavor SU(3) representations are combined to make a Lambda-N potential which has a strong symmetric LS potential and a weak anti-symmetric LS potential. We discuss a possible cancellation between symmetric and anti-symmetric LS (Lambda-N) potentials after the coupled Sigma-N sector is integrated out. We present recent results of odd-parity hyperon-hyperon potentials from lattice QCD. By using HAL QCD method, we generate hyperon-hyperon potentials from Nambu-Bethe-Salpeter (NBS) wave functions generated by lattice QCD simulation in the flavor SU(3) limit. Potentials in the irreducible flavor SU(3) representations are combined to make a Lambda-N potential which has a strong symmetric LS potential and a weak anti-symmetric LS potential. We discuss a possible cancellation between symmetric and anti-symmetric LS (Lambda-N) potentials after the coupled Sigma-N sector is integrated out. This work is supported by JSPS KAKENHI Grant Number 25400244.

QCD on the BlueGene/L Supercomputer

NASA Astrophysics Data System (ADS)

Bhanot, G.; Chen, D.; Gara, A.; Sexton, J.; Vranas, P.

2005-03-01

In June 2004 QCD was simulated for the first time at sustained speed exceeding 1 TeraFlops in the BlueGene/L supercomputer at the IBM T.J. Watson Research Lab. The implementation and performance of QCD in the BlueGene/L is presented.

Vortical susceptibility of finite-density QCD matter

DOE PAGES

Aristova, A.; Frenklakh, D.; Gorsky, A.; ...

2016-10-07

Here, the susceptibility of finite-density QCD matter to vorticity is introduced, as an analog of magnetic susceptibility. It describes the spin polarization of quarks and antiquarks in finite-density QCD matter induced by rotation. We estimate this quantity in the chirally broken phase using the mixed gauge-gravity anomaly at finite baryon density. It is proposed that the vortical susceptibility of QCD matter is responsible for the polarization of Λ and Λ¯ hyperons observed recently in heavy ion collisions at RHIC by the STAR collaboration.

Polyakov loop modeling for hot QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukushima, Kenji; Skokov, Vladimir

Here, we review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.

Polyakov loop modeling for hot QCD

DOE PAGES

Fukushima, Kenji; Skokov, Vladimir

2017-06-19

Here, we review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.

The Bayesian reconstruction of the in-medium heavy quark potential from lattice QCD and its stability

NASA Astrophysics Data System (ADS)

Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander

2016-01-01

We report recent results of a non-perturbative determination of the static heavy-quark potential in quenched and dynamical lattice QCD at finite temperature. The real and imaginary part of this complex quantity are extracted from the spectral function of Wilson line correlators in Coulomb gauge. To obtain spectral information from Euclidean time numerical data, our study relies on a novel Bayesian prescription that differs from the Maximum Entropy Method. We perform simulations on quenched 323 × Nτ (β = 7.0, ξ = 3.5) lattices with Nτ = 24, …, 96, which cover 839MeV ≥ T ≥ 210MeV. To investigate the potential in a quark-gluon plasma with light u,d and s quarks we utilize Nf = 2 + 1 ASQTAD lattices with ml = ms/20 by the HotQCD collaboration, giving access to temperatures between 286MeV ≥ T ≥ 148MeV. The real part of the potential exhibits a clean transition from a linear, confining behavior in the hadronic phase to a Debye screened form above deconfinement. Interestingly its values lie close to the color singlet free energies in Coulomb gauge at all temperatures. We estimate the imaginary part on quenched lattices and find that it is of the same order of magnitude as in hard-thermal loop perturbation theory. From among all the systematic checks carried out in our study, we discuss explicitly the dependence of the result on the default model and the number of datapoints.

Some New/Old Approaches to QCD

DOE R&D Accomplishments Database

Gross, D. J.

1992-11-01

In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD.

Light meson gas in the QCD vacuum and oscillating universe

NASA Astrophysics Data System (ADS)

Prokhorov, George; Pasechnik, Roman

2018-01-01

We have developed a phenomenological effective quantum-field theoretical model describing the "hadron gas" of the lightest pseudoscalar mesons, scalar σ-meson and σ-vacuum, i.e. the expectation value of the σ-field, at finite temperatures. The corresponding thermodynamic approach was formulated in terms of the generating functional derived from the effective Lagrangian providing the basic thermodynamic information about the "meson plasma + QCD condensate" system. This formalism enables us to study the QCD transition from the hadron phase with direct implications for cosmological evolution. Using the hypothesis about a positively-definite QCD vacuum contribution stochastically produced in early universe, we show that the universe could undergo a series of oscillations during the QCD epoch before resuming unbounded expansion.

Symmetry Transition Preserving Chirality in QCD: A Versatile Random Matrix Model

NASA Astrophysics Data System (ADS)

Kanazawa, Takuya; Kieburg, Mario

2018-06-01

We consider a random matrix model which interpolates between the chiral Gaussian unitary ensemble and the Gaussian unitary ensemble while preserving chiral symmetry. This ensemble describes flavor symmetry breaking for staggered fermions in 3D QCD as well as in 4D QCD at high temperature or in 3D QCD at a finite isospin chemical potential. Our model is an Osborn-type two-matrix model which is equivalent to the elliptic ensemble but we consider the singular value statistics rather than the complex eigenvalue statistics. We report on exact results for the partition function and the microscopic level density of the Dirac operator in the ɛ regime of QCD. We compare these analytical results with Monte Carlo simulations of the matrix model.

Universal effective hadron dynamics from superconformal algebra

DOE PAGES

Brodsky, Stanley J.; de Teramond, Guy F.; Dosch, Hans Gunter; ...

2016-05-25

An effective supersymmetric QCD light-front Hamiltonian for hadrons composed of light quarks, which includes a spin–spin interaction between the hadronic constituents, is constructed by embedding superconformal quantum mechanics into AdS space. A specific breaking of conformal symmetry inside the graded algebra determines a unique effective quark-confining potential for light hadrons, as well as remarkable connections between the meson and baryon spectra. The results are consistent with the empirical features of the light-quark hadron spectra, including a universal mass scale for the slopes of the meson and baryon Regge trajectories and a zero-mass pion in the limit of massless quarks. Ourmore » analysis is consistently applied to the excitation spectra of the π , ρ , K , K* and Φ meson families as well as to the N , Δ, Λ, Σ, Σ* , Ξ and Ξ* in the baryon sector. Here, we also predict the existence of tetraquarks which are degenerate in mass with baryons with the same angular momentum. The mass of light hadrons is expressed in a universal and frame-independent decomposition in the semiclassical approximation described here.« less

Scaling violations of the proton structure function F2 at small x

NASA Astrophysics Data System (ADS)

Abt, I.; Ahmed, T.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Bärwolff, H.; Bán, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bergstein, H.; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Biddulph, P.; Binder, E.; Bischoff, A.; Bizot, J. C.; Blobel, V.; Borras, K.; Bosetti, P. C.; Boudry, V.; Bourdarios, C.; Brasse, F.; Braun, U.; Braunschweig, W.; Bruncko, D.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Clarke, D.; Clegg, A. B.; Colombo, M.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Danilov, M.; Dann, A. W. E.; Dau, W. D.; David, M.; Deffur, E.; Delcourt, B.; Del Buono, L.; Devel, M.; De Roeck, A.; Dingus, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Drescher, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebbinghaus, R.; Eberle, M.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellis, N. N.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Fensome, I. F.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Flauger, W.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Fuhrmann, P.; Gabathuler, E.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gellrich, A.; Gennis, M.; Genzel, H.; Gerhards, R.; Godfrey, L.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goodall, A. M.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Greif, H.; Grindhammer, G.; Gruber, C.; Haack, J.; Hajduk, L.; Hamon, O.; Handschuh, D.; Hanlon, E. M.; Hapke, M.; Harjes, J.; Haydar, R.; Haynes, W. J.; Heatherington, J.; Hedberg, V.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herma, R.; Herynek, I.; Hildesheim, W.; Hill, P.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Huet, Ph.; Hufnagel, H.; Huot, N.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Jansen, T.; Jönsson, L.; Johannsen, K.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kasarian, S.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Kaufmann, H. H.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Langkau, R.; Lanius, P.; Laporte, J. F.; Lebedev, A.; Leuschner, A.; Leverenz, C.; Levonian, S.; Lewin, D.; Ley, Ch.; Lindner, A.; Lindström, G.; Linsel, F.; Lipinski, J.; Loch, P.; Lohmander, H.; Lopez, G. C.; Lüers, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, A.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Mikocki, S.; Milone, V.; Monnier, E.; Moreau, F.; Moreels, J.; Morris, J. V.; Müller, K.; Murín, P.; Murray, S. A.; Nagovizin, V.; Naroska, B.; Naumann, Th.; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Niebergall, F.; Niebuhr, C.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Orenstein, S.; Ould-Saada, F.; Pascaud, C.; Patel, G. D.; Peppel, E.; Peters, S.; Phillips, H. T.; Phillips, J. P.; Pichler, Ch.; Pilgram, W.; Pitzl, D.; Prell, S.; Prosi, R.; Rädel, G.; Raupach, F.; Rauschnabel, K.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Robertson, S. M.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Royon, C.; Rudowicz, M.; Ruffer, M.; Rusakov, S.; Rybicki, K.; Sahlmann, N.; Sanchez, E.; Sankey, D. P. C.; Savitsky, M.; Schacht, P.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmitz, W.; Schöning, A.; Schröder, V.; Schulz, M.; Schwab, B.; Schwind, A.; Scobel, W.; Seehausen, U.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Smolik, L.; Soloviev, Y.; Spitzer, H.; Staroba, P.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stösslein, U.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Taylor, R. E.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Tichomirov, I.; Truöl, P.; Turnau, J.; Tutas, J.; Urban, L.; Usik, A.; Valkar, S.; Valkarova, A.; Vallée, C.; Van Esch, P.; Vartapetian, A.; Vazdik, Y.; Vecko, M.; Verrecchia, P.; Vick, R.; Villet, G.; Vogel, E.; Wacker, K.; Walker, I. W.; Walther, A.; Weber, G.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Winde, M.; Winter, G.-G.; Wolff, Th.; Womersley, L. A.; Wright, A. E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Závada, P.; Zeitnitz, C.; Ziaeepour, H.; Zimmer, M.; Zimmermann, W.; Zomer, F.; H1 Collaboration

1994-01-01

An analysis is presented of scaling violations of the proton structure function F2( x, Q2) measured with the H1 detector at HERA in the range of Bjorken x values between x = 3 × 10 -4 and 10 -2 for four-momentum transfers Q> 2 larger than 8.7 GeV 2. The structure function F2( x, Q2) is observed to rise linearly with ln Q2. Under the assumption that the observed scaling violations at small x ⩽ 0.01 are described correctly by perturbative QCD, an estimate is obtained of the gluon distribution function G( x, Q02) at Q22 = 20 GeV 2.

Dynamical gluon mass in the instanton vacuum model

NASA Astrophysics Data System (ADS)

Musakhanov, M.; Egamberdiev, O.

2018-04-01

We consider the modifications of gluon properties in the instanton liquid model (ILM) for the QCD vacuum. Rescattering of gluons on instantons generates the dynamical momentum-dependent gluon mass Mg (q). First, we consider the case of a scalar gluon, no zero-mode problem occurs and its dynamical mass Ms (q) can be found. Using the typical phenomenological values of the average instanton size ρ = 1 / 3 fm and average inter-instanton distance R = 1 fm we get Ms (0) = 256 MeV. We then extend this approach to the real vector gluon with zero-modes carefully considered. We obtain the following expression Mg2 (q) = 2 Ms2 (q). This modification of the gluon in the instanton media will shed light on nonperturbative aspect on heavy quarkonium physics.

Chiral phases of fundamental and adjoint quarks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natale, A. A.; Instituto de Física Teórica - UNESP Rua Dr. Bento T. Ferraz, 271, Bl.II - 01140-070, São Paulo, SP

2016-01-22

We consider a QCD chiral symmetry breaking model where the gap equation contains an effective confining propagator and a dressed gluon propagator with a dynamically generated mass. This model is able to explain the ratios between the chiral transition and deconfinement temperatures in the case of fundamental and adjoint quarks. It also predicts the recovery of the chiral symmetry for a large number of quarks (n{sub f} ≈ 11 – 13) in agreement with lattice data.

Estimation of stopped protons at energies relevant for a beam energy scan at the BNL Relativistic Heavy Ion Collider

NASA Astrophysics Data System (ADS)

Thakur, Dhananjaya; Jakhar, Sunil; Garg, Prakhar; Sahoo, Raghunath

2017-04-01

The recent net-proton fluctuation results of the STAR (Solenoidal Tracker At RHIC) experiment from the beam energy scan (BES) program at the BNL Relativistic Heavy Ion Collider (RHIC) have drawn much attention to exploring the QCD critical point and the nature of deconfinement phase transition. There has been much speculation that the nonmonotonic behavior of κ σ2 of the produced protons around √{sN N} = 19.6 GeV in the STAR results may be due to the existence of a QCD critical point. However, the experimentally measured proton distributions contain protons from heavy resonance decays, from baryon stopping, and from direct production processes. These proton distributions are used to estimate the net-proton number fluctuation. Because it is difficult to disentangle the protons from the above-mentioned sources, it is better to devise a method which will account for the directly produced baryons (protons) to study the dynamical fluctuation at different center-of-mass energies. This is because it is assumed that any associated criticality in the system could affect the particle production mechanism and hence the dynamical fluctuation in various conserved numbers. In the present work, we demonstrate a method to estimate the number of stopped protons at RHIC BES energies for central 0-5% Au +Au collisions within STAR acceptance and discuss its implications on the net-proton fluctuation results.

A first determination of the unpolarized quark TMDs from a global analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bacchetta, Alessandro; Delcarro, Filippo; Pisano, Cristian

Transverse momentum dependent distribution and fragmentation functions of unpolarized quarks inside unpolarized protons are extracted, for the first time, through a simultaneous analysis of semi-inclusive deep-inelastic scattering, Drell-Yan and Z boson hadroproduction processes. This study is performed at leading order in perturbative QCD, with energy scale evolution at the next-to-leading logarithmic accuracy. Moreover, some specific choices are made to deal with low scale evolution around 1 GeV2. Since only data in the low transverse momentum region are considered, no matching to fixed-order calculations at high transverse momentum is needed.

Weak mixing below the weak scale in dark-matter direct detection

NASA Astrophysics Data System (ADS)

Brod, Joachim; Grinstein, Benjamin; Stamou, Emmanuel; Zupan, Jure

2018-02-01

If dark matter couples predominantly to the axial-vector currents with heavy quarks, the leading contribution to dark-matter scattering on nuclei is either due to one-loop weak corrections or due to the heavy-quark axial charges of the nucleons. We calculate the effects of Higgs and weak gauge-boson exchanges for dark matter coupling to heavy-quark axial-vector currents in an effective theory below the weak scale. By explicit computation, we show that the leading-logarithmic QCD corrections are important, and thus resum them to all orders using the renormalization group.

Baryon interactions in lattice QCD: the direct method vs. the HAL QCD potential method

NASA Astrophysics Data System (ADS)

Iritani, T.; HAL QCD Collaboration

We make a detailed comparison between the direct method and the HAL QCD potential method for the baryon-baryon interactions, taking the $\\Xi\\Xi$ system at $m_\\pi= 0.51$ GeV in 2+1 flavor QCD and using both smeared and wall quark sources. The energy shift $\\Delta E_\\mathrm{eff}(t)$ in the direct method shows the strong dependence on the choice of quark source operators, which means that the results with either (or both) source are false. The time-dependent HAL QCD method, on the other hand, gives the quark source independent $\\Xi\\Xi$ potential, thanks to the derivative expansion of the potential, which absorbs the source dependence to the next leading order correction. The HAL QCD potential predicts the absence of the bound state in the $\\Xi\\Xi$($^1$S$_0$) channel at $m_\\pi= 0.51$ GeV, which is also confirmed by the volume dependence of finite volume energy from the potential. We also demonstrate that the origin of the fake plateau in the effective energy shift $\\Delta E_\\mathrm{eff}(t)$ at $t \\sim 1$ fm can be clarified by a few low-lying eigenfunctions and eigenvalues on the finite volume derived from the HAL QCD potential, which implies that the ground state saturation of $\\Xi\\Xi$($^1$S$_0$) requires $t \\sim 10$ fm in the direct method for the smeared source on $(4.3 \\ \\mathrm{fm})^3$ lattice, while the HAL QCD method does not suffer from such a problem.

Evolution equation in the field theory of strings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marui, M.; Sugamoto, A.; Oda, I.

This paper reports on a stringy version of the Altarelli-Parisi equation given within the field theory of bosonic strings formulated in the light-cone gauge. Using this equation, the authors study the behavior of the decay function of strings under the change of reference scale, especially imposing an assumption of large transverse momentum. In some cases the n-th moment of the decay function behaves very differently from QCD.

First Renormalized Parton Distribution Functions from Lattice QCD

NASA Astrophysics Data System (ADS)

Lin, Huey-Wen; LP3 Collaboration

2017-09-01

We present the first lattice-QCD results on the nonperturbatively renormalized parton distribution functions (PDFs). Using X.D. Ji's large-momentum effective theory (LaMET) framework, lattice-QCD hadron structure calculations are able to overcome the longstanding problem of determining the Bjorken- x dependence of PDFs. This has led to numerous additional theoretical works and exciting progress. In this talk, we will address a recent development that implements a step missing from prior lattice-QCD calculations: renormalization, its effects on the nucleon matrix elements, and the resultant changes to the calculated distributions.

The CP-PACS Project and Lattice QCD Results

NASA Astrophysics Data System (ADS)

Iwasaki, Y.

The aim of the CP-PACS project was to develop a massively parallel computer for performing numerical research in computational physics with primary emphasis on lattice QCD. The CP-PACS computer with a peak speed of 614 GFLOPS with 2048 processors was completed in September 1996, and has been in full operation since October 1996. We present an overview of the CP-PACS project and describe characteristics of the CP-PACS computer. The CP-PACS has been mainly used for hadron spectroscopy studies in lattice QCD. Main results in lattice QCD simulations are given.

Remarks on the Phase Transition in QCD

NASA Astrophysics Data System (ADS)

Wilczek, Frank

The significance of the question of the order of the phase transition in QCD, and recent evidence that real-world QCD is probably close to having a single second order transition as a function of temperature, is reviewed. Although this circumstance seems to remove the possibility that the QCD transition during the big bang might have had spectacular cosmological consequences, there is some good news: it allows highly non-trivial yet reliable quantitative predictions to be made for the behavior near the transition. These predictions can be tested in numerical simulations and perhaps even eventually in heavy ion collisions. The present paper is a very elementary discussion of the relevant concepts, meant to be an accessible introduction for those innocent of the renormalization group approach to critical phenomena and/or the details of QCD.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dudek, Jozef

Highlights of the research include: the determination of the form of the lowest energy gluonic excitation within QCD and the spectrum of hybrid hadrons which follows; the first calculation of the spectrum of hybrid baryons within a first-principles approach to QCD; a detailed mapping out of the phase-shift of elastic ππ scattering featuring the ρ resonance at two values of the light quark mass within lattice QCD; the first (and to date, only) determinations of coupled-channel meson-meson scattering within first-principles QCD; the first (and to date, only) determinations of the radiative coupling of a resonant state, the ρ appearing inmore » πγ→ππ; the first (and to date, only) determination of the properties of the broad σ resonance in elastic ππ scattering within QCD without unjustified approximations.« less

Highlights in light-baryon spectroscopy and searches for gluonic excitations

NASA Astrophysics Data System (ADS)

Crede, Volker

2016-01-01

The spectrum of excited hadrons - mesons and baryons - serves as an excellent probe of quantum chromodynamics (QCD), the fundamental theory of the strong interaction. The strong coupling however makes QCD challenging. It confines quarks and breaks chiral symmetry, thus providing us with the world of light hadrons. Highly-excited hadronic states are sensitive to the details of quark confinement, which is only poorly understood within QCD. This is the regime of non-perturbative QCD and it is one of the key issues in hadronic physics to identify the corresponding internal degrees of freedom and how they relate to strong coupling QCD. The quark model suggests mesons are made of a constituent quark and an antiquark and baryons consist of three such quarks. QCD predicts other forms of matter. What is the role of glue? Resonances with large gluonic components are predicted as bound states by QCD. The lightest hybrid mesons with exotic quantum numbers are estimated to have masses in the range from 1 to 2 GeV/c2 and are well in reach of current experimental programs. At Jefferson Laboratory (JLab) and other facilities worldwide, the high-energy electron and photon beams present a remarkably clean probe of hadronic matter, providing an excellent microscope for examining atomic nuclei and the strong nuclear force.

Leptoquarks meet ɛ '/ ɛ and rare Kaon processes

NASA Astrophysics Data System (ADS)

Bobeth, Christoph; Buras, Andrzej J.

2018-02-01

We analyse for the first time the CP violating ratio ɛ '/ ɛ in K → ππ decays in leptoquark (LQ) models. Assuming a mass gap to the electroweak (EW) scale, the main mechanism for LQs to contribute to ɛ ' /ɛ is EW gauge-mixing of semi-leptonic into non-leptonic operators, which we treat in the Standard Model effective theory (SMEFT). We perform also the one-loop decoupling for scalar LQs, finding that in all models with both left-handed and right-handed LQ couplings box-diagrams generate numerically strongly enhanced EW-penguin operators Q 8,8' already at the LQ scale. We then investigate correlations of ɛ ' /ɛ with rare Kaon processes ( {K}_L\\to {π}^0ν \\overline{ν} , {K}+\\to {π}+ν \\overline{ν} , {K}_L\\to {π}^0ℓ \\overline{ℓ} , {K}_S\\to μ \\overline{μ} , Δ M K and ɛ K ) and find that even imposing only a moderate enhancement of ( ɛ ' /ɛ)NP = 5 × 10-4 to explain the current anomaly hinted by the Dual QCD approach and RBC-UKQCD lattice QCD calculations leads to conflicts with experimental upper bounds on rare Kaon processes. They exclude all LQ models with only a single coupling as an explanation of the ɛ ' /ɛ anomaly and put strong-to-serious constraints on parameter spaces of the remaining models. Future results on {K}+\\to {π}+ν \\overline{ν} from the NA62 collaboration, {K}_L\\to {π}^0ν \\overline{ν} from the KOTO experiment and {K}_S\\to μ \\overline{μ} from LHCb will even stronger exhibit the difficulty of LQ models in explaining the measured ɛ ' /ɛ, in case the ɛ ' /ɛ anomaly will be confirmed by improved lattice QCD calculations. Hopefully also improved measurements of {K}_L\\to {π}^0ℓ \\overline{ℓ} decays will one day help in this context.

Chiral phase structure of three flavor QCD at vanishing baryon number density

DOE PAGES

Bazavov, A.; Ding, H. -T.; Hegde, P.; ...

2017-04-12

In this paper, we investigate the phase structure of QCD with three degenerate quark flavors as a function of the degenerate quark masses at vanishing baryon number density. We use the highly improved staggered quarks on lattices with temporal extent N τ = 6 and perform calculations for six values of quark masses, which in the continuum limit correspond to pion masses in the range 80 MeV ≲ m π ≲ 230 MeV. By analyzing the volume and temperature dependence of the chiral condensate and chiral susceptibility, we find no direct evidence for a first-order phase transition in this rangemore » of pion mass values. Finally, relying on the universal scaling behaviors of the chiral observables near an anticipated chiral critical point, we estimate an upper bound for the critical pion mass m c π ≲ 50 MeV, below which a region of first-order chiral phase transition is favored.« less

Low energy constants of S U ( 2 ) partially quenched chiral perturbation theory from N f = 2 + 1 domain wall QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyle, P. A.; Christ, N. H.; Garron, N.

2016-03-09

Here, we have performed fits of the pseudoscalar masses and decay constants, from a variety of the RBC-UKQCD Collaboration’s domain wall fermion ensembles, to SU(2) partially quenched chiral perturbation theory at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). We report values for 9 NLO and 8 linearly independent combinations of NNLO partially quenched low-energy constants, which we compare to other lattice and phenomenological determinations. We discuss the size of successive terms in the chiral expansion and use our large set of low-energy constants to make predictions for mass splittings due to QCD isospin-breaking effects and the S-wave ππ scattering lengths.more » Lastly, we conclude that, for the range of pseudoscalar masses explored in this work, 115 MeV≲mPS≲430 MeV, the NNLO SU(2) expansion is quite robust and can fit lattice data with percent-scale accuracy.« less

Quark masses and strong coupling constant in 2+1 flavor QCD

DOE PAGES

Maezawa, Y.; Petreczky, P.

2016-08-30

We present a determination of the strange, charm and bottom quark masses as well as the strong coupling constant in 2+1 flavor lattice QCD simulations using highly improved staggered quark action. The ratios of the charm quark mass to the strange quark mass and the bottom quark mass to the charm quark mass are obtained from the meson masses calculated on the lattice and found to be mc/ms = 11.877(91) and mb/mc = 4.528(57) in the continuum limit. We also determine the strong coupling constant and the charm quark mass using the moments of pseudoscalar charmonium correlators: α s(μ =more » m c) = 0.3697(85) and mc(μ = mc) = 1.267(12) GeV. Our result for αs corresponds to the determination of the strong coupling constant at the lowest energy scale so far and is translated to the value α s(μ = M Z, n f = 5) = 0.11622(84).« less

Searching for the QCD Axion with Black Holes and Gravitational Waves

NASA Astrophysics Data System (ADS)

Baryakhtar, Masha

2017-01-01

The LIGO detection of gravitational waves has opened a new window on the universe. I will discuss how the process of superradiance, combined with gravitational wave measurements, makes black holes into nature's laboratories to search for new light bosons. When a bosonic particle's Compton wavelength is comparable to the horizon size of a black hole, superradiance of these bosons into bound ``Bohr orbitals'' extracts energy and angular momentum from the black hole. The occupation number of the levels grows exponentially and the black hole spins down. For efficient superradiance of stellar black holes, the particle must be ultralight, with mass below 10-10 eV; one candidate for such an ultralight boson is the QCD axion with decay constant above the GUT scale. Measurements of BH spins in X-ray binaries and in mergers at Advanced LIGO can exclude or provide evidence for an ultralight axion. Axions transitioning between levels of the gravitational ``atom'' and annihilating to gravitons may produce thousands of monochromatic gravitational wave signals, turning LIGO into a particle detector.

An ϵ' improvement from right-handed currents

DOE PAGES

Cirigliano, Vincenzo; Dekens, Wouter Gerard; de Vries, Jordy; ...

2017-01-23

Recent lattice QCD calculations of direct CP violation in K L → ππ decays indicate tension with the experimental results. Assuming this tension to be real, we investigate a possible beyond-the-Standard Model explanation via right-handed charged currents. By using chiral perturbation theory in combination with lattice QCD results, we accurately calculate the modification of ϵ'/ϵ induced by right-handed charged currents and extract values of the couplings that are necessary to explain the discrepancy, pointing to a scale around 10–100 TeV. We find that couplings of this size are not in conflict with constraints from other precision experiments, but next-generation hadronicmore » electric dipole moment searches (such as neutron and 225Ra) can falsify this scenario. As a result, we work out in detail a direct link, based on chiral perturbation theory, between CP violation in the kaon sector and electric dipole moments induced by right-handed currents which can be used in future analyses of left-right symmetric models.« less

Performance of the Cray T3D and Emerging Architectures on Canopy QCD Applications

NASA Astrophysics Data System (ADS)

Fischler, Mark; Uchima, Mike

1996-03-01

The Cray T3D, an MIMD system with NUMA shared memory capabilities and in principle very low communications latency, can support the Canopy framework for grid-oriented applications. CANOPY has been ported to the T3D, with the intent of making it available to a spectrum of users. The performance of the T3D running Canopy has been benchmarked on five QCD applications extensively run on ACPMAPS at Fermilab, requiring a variety of data access patterns. The net performance and scaling behavior reveals an efficiency relative to peak Gflops almost identical to that achieved on ACPMAPS. Detailed studies of the major factors impacting performance are presented. Generalizations applying this analysis to the newly emerging crop of commercial systems reveal where their limitations will lie. On these applications, efficiencies of above 25% are not to be expected; eliminating overheads due to Canopy will improve matters, but by less than a factor of two.

Performance of the Cray T3D and emerging architectures on canopy QCD applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischler, M.; Uchima, M.

1995-11-01

The Cray T3D, an MIMD system with NUMA shared memory capabilities and in principle very low communications latency, can support the Canopy framework for grid-oriented applications. CANOPY has been ported to the T3D, with the intent of making it available to a spectrum of users. The performance of the T3D running Canopy has been benchmarked on five QCD applications extensively run on ACPMAPS at Fermilab, requiring a variety of data access patterns. The net performance and scaling behavior reveals an efficiency relative to peak Gflops almost identical to that achieved on ACPMAPS. Detailed studies of the major factors impacting performancemore » are presented. Generalizations applying this analysis to the newly emerging crop of commercial systems reveal where their limitations will lie. On these applications, efficiencies of above 25% are not to be expected; eliminating overheads due to Canopy will improve matters, but by less than a factor of two.« less

Gravitational wave from dark sector with dark pion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsumura, Koji; Yamada, Masatoshi; Yamaguchi, Yuya, E-mail: ko2@gauge.scphys.kyoto-u.ac.jp, E-mail: m.yamada@thphys.uni-heidelberg.de, E-mail: yy@particle.sci.hokudai.ac.jp

In this work, we investigate the spectra of gravitational waves produced by chiral symmetry breaking in dark quantum chromodynamics (dQCD) sector. The dark pion (π) can be a dark matter candidate as weakly interacting massive particle (WIMP) or strongly interacting massive particle (SIMP). For a WIMP scenario, we introduce the dQCD sector coupled to the standard model (SM) sector with classical scale invariance and investigate the annihilation process of the dark pion via the 2π → 2 SM process. For a SIMP scenario, we investigate the 3π → 2π annihilation process of the dark pion as a SIMP using chiralmore » perturbation theory. We find that in the WIMP scenario the gravitational wave background spectra can be observed by future space gravitational wave antennas. On the other hand, when the dark pion is the SIMP dark matter with the constraints for the chiral perturbative limit and pion-pion scattering cross section, the chiral phase transition becomes crossover and then the gravitational waves are not produced.« less

Neutral Pion Electroproduction in the Δ Resonance Region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villano, Anthony

2007-11-01

The electroproduction of baryon resonances at high Q 2 is examined. Analysis focuses on the Δ(1232) resonance via exclusive pseudoscalar meson production of π 0 particles. Differential cross sections are extracted for exclusive π 0 electroproduction. In the central invariant mass (W) region the cross sections are used to extract resonant multipole amplitudes. In particular, the ratio of the electric quadrupole to magnetic dipole amplitudes (E2/M1) will be discussed for the Δ(1232) resonance. The transition to pQCD is discussed in terms of E2/M1 and other multipoles. The helicity amplitude A 3/2 can be used as a baryon helicity conservation meter in this context and will be discussed. The fast shrinking of the resonant contribution in the Δ region is observed at this high momentum transfer. Apart from the observables related to pQCD scaling, the transition form factor Gmore » $$*\\atop{M}$$ is extracted along with the scalar to magnetic dipole ratio C2/M1.« less

The supersymmetric method in random matrix theory and applications to QCD

NASA Astrophysics Data System (ADS)

Verbaarschot, Jacobus

2004-12-01

The supersymmetric method is a powerful method for the nonperturbative evaluation of quenched averages in disordered systems. Among others, this method has been applied to the statistical theory of S-matrix fluctuations, the theory of universal conductance fluctuations and the microscopic spectral density of the QCD Dirac operator. We start this series of lectures with a general review of Random Matrix Theory and the statistical theory of spectra. An elementary introduction of the supersymmetric method in Random Matrix Theory is given in the second and third lecture. We will show that a Random Matrix Theory can be rewritten as an integral over a supermanifold. This integral will be worked out in detail for the Gaussian Unitary Ensemble that describes level correlations in systems with broken time-reversal invariance. We especially emphasize the role of symmetries. As a second example of the application of the supersymmetric method we discuss the calculation of the microscopic spectral density of the QCD Dirac operator. This is the eigenvalue density near zero on the scale of the average level spacing which is known to be given by chiral Random Matrix Theory. Also in this case we use symmetry considerations to rewrite the generating function for the resolvent as an integral over a supermanifold. The main topic of the second last lecture is the recent developments on the relation between the supersymmetric partition function and integrable hierarchies (in our case the Toda lattice hierarchy). We will show that this relation is an efficient way to calculate superintegrals. Several examples that were given in previous lectures will be worked out by means of this new method. Finally, we will discuss the quenched QCD Dirac spectrum at nonzero chemical potential. Because of the nonhermiticity of the Dirac operator the usual supersymmetric method has not been successful in this case. However, we will show that the supersymmetric partition function can be evaluated by means of the replica limit of the Toda lattice equation.

Parton distributions and lattice QCD calculations: A community white paper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred

In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this paper we present an overview of lattice-QCDmore » and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. Finally, this document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.« less

Parton distributions and lattice QCD calculations: A community white paper

DOE PAGES

Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred; ...

2018-01-31

In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this paper we present an overview of lattice-QCDmore » and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. Finally, this document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.« less

Electromagnetic effects on the light hadron spectrum

DOE PAGES

Basak, S.; Bazavov, A.; Bernard, C.; ...

2015-09-28

Calculations studying electromagnetic effects on light mesons are reported. The calculations use fully dynamical QCD, but only quenched photons, which suffices to NLO in χPT; that is, the sea quarks are electrically neutral, while the valence quarks carry charge. The non-compact formalism is used for photons. New results are obtained with lattice spacing as small as 0.045 fm and a large range of volumes. The success of chiral perturbation theory in describing these results and the implications for light quark masses are considered.