Transversity form factors of the pion in chiral quark models
Broniowski, Wojciech; Dorokhov, Alexander E.; Arriola, Enrique Ruiz
2010-11-01
The transversity form factors of the pion, involving matrix elements of bilocal tensor currents, are evaluated in chiral quark models, both in the local Nambu-Jona-Lasinio with the Pauli-Villars regularization, as well as in nonlocal models involving momentum-dependent quark mass. After suitable QCD evolution, the agreement with recent lattice calculations is very good, in accordance to the fact that the spontaneously broken chiral symmetry governs the dynamics of the pion. Meson dominance of form factors with expected meson masses also works properly, conforming to the parton-hadron duality in the considered process.
Quark matter and meson properties in a Nonlocal SU(3) chiral quark model at finite temperature
Gomez Dumm, D.; Contrera, G. A.
2012-06-15
We study the finite temperature behavior of light scalar and pseudoscalar meson properties in the context of a three-flavor nonlocal chiral quark model. The model includes mixing with active strangeness degrees of freedom, and takes care of the effect of gauge interactions by coupling the quarks with a background color field. We analyze the chiral restoration and deconfinement transitions, as well as the temperature dependence of meson masses, mixing angles, and decay constants.
Isospin symmetry breaking in the chiral quark model
NASA Astrophysics Data System (ADS)
Song, Huiying; Zhang, Xinyu; Ma, Bo-Qiang
2010-12-01
We discuss the isospin symmetry breaking (ISB) of the valence- and sea-quark distributions between the proton and the neutron in the framework of the chiral quark model. We assume that isospin symmetry breaking is the result of mass differences between isospin multiplets and then analyze the effects of isospin symmetry breaking on the Gottfried sum rule and the NuTeV anomaly. We show that, although both flavor asymmetry in the nucleon sea and the ISB between the proton and the neutron can lead to the violation of the Gottfried sum rule, the main contribution is from the flavor asymmetry in the framework of the chiral quark model. We also find that the correction to the NuTeV anomaly is in an opposite direction, so the NuTeV anomaly cannot be removed by isospin symmetry breaking in the chiral quark model. It is remarkable that our results of ISB for both valence- and sea-quark distributions are consistent with the Martin-Roberts-Stirling-Thorne parametrization of quark distributions.
Non-leptonic decays in an extended chiral quark model
Eeg, J. O.
2012-10-23
We consider the color suppressed (nonfactorizable) amplitude for the decay mode B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0}. We treat the b-quark in the heavy quark limit and the energetic light (u,d,s) quarks within a variant of Large Energy Effective Theory combined with an extension of chiral quark models. Our calculated amplitude for B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0} is suppressed by a factor of order {Lambda}{sub QCD}/m{sub b} with respect to the factorized amplitude, as it should according to QCD-factorization. Further, for reasonable values of the (model dependent) gluon condensate and the constituent quark mass, the calculated nonfactorizable amplitude for B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0} can easily accomodate the experimental value. Unfortunately, the color suppressed amplitude is very sensitive to the values of these model dependent parameters. Therefore fine-tuning is necessary in order to obtain an amplitude compatible with the experimental result for B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0}.
Generalized quark transversity distribution of the pion in chiral quark models
Dorokhov, Alexander E.; Broniowski, Wojciech; Arriola, Enrique Ruiz
2011-10-01
The transversity generalized parton distributions (tGPDs) of the pion, involving matrix elements of the tensor bilocal quark current, are analyzed in chiral quark models. We apply the nonlocal chiral models involving a momentum-dependent quark mass, as well as the local Nambu-Jona-Lasinio with the Pauli-Villars regularization to calculate the pion tGPDs, as well as related quantities following from restrained kinematics, evaluation of moments, or taking the Fourier-Bessel transforms to the impact-parameter space. The obtained distributions satisfy the formal requirements, such as proper support and polynomiality, following from Lorentz covariance. We carry out the leading-order QCD evolution from the low quark-model scale to higher lattice scales, applying the method of Kivel and Mankiewicz. We evaluate several lowest-order generalized transversity form factors, accessible from the recent lattice QCD calculations. These form factors, after evolution, agree properly with the lattice data, in support of the fact that the spontaneously broken chiral symmetry is the key element also in the evaluation of the transversity observables.
Finite-temperature corrections in the dilated chiral quark model
Kim, Y.; Lee, Hyun Kyu |; Rho, M. |
1995-03-01
We calculate the finite-temperature corrections in the dilated chiral quark model using the effective potential formalism. Assuming that the dilaton limit is applicable at some short length scale, we interpret the results to represent the behavior of hadrons in dense and hot matter. We obtain the scaling law, f{sub {pi}}(T)/f{sub {pi}} = m{sub Q}(T)/m{sub Q} {approx_equal} m{sub {sigma}}(T)/m{sub {sigma}}while we argue, using PCAC, that pion mass does not scale within the temperature range involved in our Lagrangian. It is found that the hadron masses and the pion decay constant drop faster with temperature in the dilated chiral quark model than in the conventional linear sigma model that does not take into account the QCD scale anomaly. We attribute the difference in scaling in heat bath to the effect of baryonic medium on thermal properties of the hadrons. Our finding would imply that the AGS experiments (dense and hot matter) and the RHIC experiments (hot and dilute matter) will ``see`` different hadron properties in the hadronization exit phase.
Proton spin problem and chiral constituent quark model
Rana, J. M. S.; Dahiya, H.; Gupta, M.
2008-10-13
Some of the non-relativistic quark model (NRQM) predictions of some spin and flavor parameters are in sharp conflict with the observations made from deep inelastic scattering experiments. Besides this there are other spin and flavor dependent quantities which could not be explained by NRQM. These contradictions are referred to as Proton spin problem. These issues get resolved, to some extent, in Chiral Constituent Quark Model (CQM) which incorporates the basic features of NRQM and chiral symmetry. The implications of the latest data pertaining to u-bar-d-bar asymmetry and the spin polarization functions on the contributions of singlet Goldstone Boson {eta}' within CQM with configuration mixing for explaining the proton spin problem have been investigated. It is found that the present data favors smaller values of the coupling of singlet Goldstone Boson as compared to the corresponding contributions from {pi}, K and {eta}' Goldstone bosons. It seems that a small non-zero value of the coupling of {eta}'({zeta}{ne}0)({zeta}{ne}0) is preferred over {zeta} = -0.10 phenomenologically.
NASA Astrophysics Data System (ADS)
Girdhar, Aarti; Dahiya, Harleen; Randhawa, Monika
2015-08-01
The magnetic moments of JP=3/2+ decuplet baryons have been calculated in the chiral constituent quark model (χ CQM ) with explicit results for the contribution coming from the valence quark polarizations, sea quark polarizations, and their orbital angular momentum. Since the JP=3/2+ decuplet baryons have short lifetimes, the experimental information about them is limited. The χ CQM has important implications for chiral symmetry breaking as well as SU(3) symmetry breaking since it works in the region between the QCD confinement scale and the chiral symmetry breaking scale. The predictions in the model not only give a satisfactory fit when compared with the experimental data but also show improvement over the other models. The effect of the confinement on quark masses has also been discussed in detail and the results of χ CQM are found to improve further with the inclusion of effective quark masses.
Vector and axial vector mesons in a nonlocal chiral quark model
NASA Astrophysics Data System (ADS)
Izzo Villafañe, M. F.; Gómez Dumm, D.; Scoccola, N. N.
2016-09-01
Basic features of nonstrange vector and axial vector mesons are analyzed in the framework of a chiral quark model that includes nonlocal four-fermion couplings. Unknown model parameters are determined from some input values of masses and decay constants, while nonlocal form factors are taken from a fit to lattice QCD results for effective quark propagators. Numerical results show a good agreement with the observed meson phenomenology.
The nucleon-delta splitting in the chiral quark-meson model
NASA Astrophysics Data System (ADS)
Cohen, Thomas D.; Banerjee, Manoj K.
1986-01-01
Cranking techniques are employed to calculate the N - Δ splitting in the chiral quark-meson model. A splitting of 322 MeV is obtained. It is determined that about 80% of the angular momentum and isospin in the model are carried by the mesons.
Gravitational and higher-order form factors of the pion in chiral quark models
Broniowski, Wojciech; Arriola, Enrique Ruiz
2008-11-01
The gravitational form factor of the pion is evaluated in two chiral quark models and confronted with the recent full-QCD lattice data. We find good agreement for the case of the spectral quark model, which builds in the vector-meson dominance for the charge form factor. We derive a simple relation between the gravitational and electromagnetic form factors, holding in the considered quark models in the chiral limit. The relation implies that the gravitational mean squared radius is half the electromagnetic one. We also analyze higher-order quark generalized form factors of the pion, related to higher moments in the symmetric Bjorken X variable of the generalized parton distribution functions, and discuss their perturbative QCD evolution, which is needed to relate the quark-model predictions to the lattice data. The values of the higher-order quark form factors at t=0, computed on the lattice, also agree with our quark-model results within the statistical and method uncertainties.
From chiral quark dynamics with Polyakov loop to the hadron resonance gas model
Arriola, E. R.; Salcedo, L. L.; Megias, E.
2013-03-25
Chiral quark models with Polyakov loop at finite temperature have been often used to describe the phase transition. We show how the transition to a hadron resonance gas is realized based on the quantum and local nature of the Polyakov loop.
Adler function and hadronic contribution to the muon g-2 in a nonlocal chiral quark model
Dorokhov, Alexander E.
2004-11-01
The behavior of the vector Adler function at spacelike momenta is studied in the framework of a covariant chiral quark model with instantonlike quark-quark interaction. This function describes the transition between the high-energy asymptotically free region of almost massless current quarks to the low-energy hadronized regime with massive constituent quarks. The model reproduces the Adler function and V-A correlator extracted from the ALEPH and OPAL data on hadronic {tau} lepton decays, transformed into the Euclidean domain via dispersion relations. The leading order contribution from the hadronic part of the photon vacuum polarization to the anomalous magnetic moment of the muon, a{sub {mu}}{sup hvp(1)}, is estimated.
Generalized parton distributions of the pion in chiral quark models and their QCD evolution
Broniowski, Wojciech; Ruiz Arriola, Enrique; Golec-Biernat, Krzysztof
2008-02-01
We evaluate generalized parton distributions of the pion in two chiral quark models: the spectral quark model and the Nambu-Jona-Lasinio model with a Pauli-Villars regularization. We proceed by the evaluation of double distributions through the use of a manifestly covariant calculation based on the {alpha} representation of propagators. As a result polynomiality is incorporated automatically and calculations become simple. In addition, positivity and normalization constraints, sum rules, and soft-pion theorems are fulfilled. We obtain explicit formulas, holding at the low-energy quark-model scale. The expressions exhibit no factorization in the t-dependence. The QCD evolution of those parton distributions is carried out to experimentally or lattice accessible scales. We argue for the need of evolution by comparing the parton distribution function and the parton distribution amplitude of the pion to the available experimental and lattice data, and confirm that the quark-model scale is low, about 320 MeV.
Photon distribution amplitudes and light-cone wave functions in chiral quark models
Dorokhov, Alexander E.; Broniowski, Wojciech; Ruiz Arriola, Enrique
2006-09-01
The leading- and higher-twist distribution amplitudes and light-cone wave functions of real and virtual photons are analyzed in chiral quark models. The calculations are performed in the nonlocal quark model based on the instanton picture of the QCD vacuum, as well as in the spectral quark model and the Nambu-Jona-Lasinio model with the Pauli-Villars regulator, which both treat interaction of quarks with external fields locally. We find that in all considered models the leading-twist distribution amplitudes of the real photon defined at the quark-model momentum scale are constant or remarkably close to the constant in the x variable, thus are far from the asymptotic limit form. The QCD evolution to higher momentum scales is necessary and we carry it out at the leading order of the perturbative theory for the leading-twist amplitudes. We provide estimates for the magnetic susceptibility of the quark condensate {chi}{sub m} and the coupling f{sub 3{gamma}}, which in the nonlocal model turn out to be close to the estimates from QCD sum rules. We find the higher-twist distribution amplitudes at the quark model scale and compare them to the Wandzura-Wilczek estimates. In addition, in the spectral model we evaluate the distribution amplitudes and light-cone wave functions of the {rho}-meson.
Contrera, G. A.; Dumm, D. Gomez; Scoccola, Norberto N.
2010-03-01
We study the finite temperature behavior of light scalar and pseudoscalar meson properties in the context of a three-flavor nonlocal chiral quark model. The model includes mixing with active strangeness degrees of freedom, and takes care of the effect of gauge interactions by coupling the quarks with the Polyakov loop. We analyze the chiral restoration and deconfinement transitions, as well as the temperature dependence of meson masses, mixing angles and decay constants. The critical temperature is found to be T{sub c{approx_equal}}202 MeV, in better agreement with lattice results than the value recently obtained in the local SU(3) PNJL model. It is seen that above T{sub c} pseudoscalar meson masses get increased, becoming degenerate with the masses of their chiral partners. The temperatures at which this matching occurs depend on the strange quark composition of the corresponding mesons. The topological susceptibility shows a sharp decrease after the chiral transition, signalling the vanishing of the U(1){sub A} anomaly for large temperatures.
Isgur-Wise function within a modified heavy-light chiral quark model
Eeg, Jan O.; Kumericki, Kresimir
2010-04-01
We consider the Isgur-Wise function {xi}({omega}) within a new modified version of a heavy-light chiral quark model. While early versions of such models gave an absolute value of the slope that was too small, namely {xi}{sup '}(1){approx_equal}-0.4 to -0.3, we show how extended version(s) may lead to values around -1, in better agreement with recent measurements. This is obtained by introducing a new mass parameter in the heavy-quark propagator. We also shortly comment on the consequences for the decay modes B{yields}DD.
Duck, I. )
1993-04-01
Second-order radiative corrections to the nucleon axial vector coupling constant from gluon, pion, and sigma meson exchange are calculated in the chiral soliton quark model. Many apparent processes are found not to contribute. The soliton is elastically decoupled from meson radiative corrections which are dominated by a gluon exchange contribution equivalent to a gluonic hybrid component of the nucleon. A 30% radiative reduction of the axial coupling strength is indicated.
Nucleon structure functions and longitudinal spin asymmetries in the chiral quark constituent model
NASA Astrophysics Data System (ADS)
Dahiya, Harleen; Randhawa, Monika
2016-06-01
We have analyzed the phenomenological dependence of the spin independent (F1p ,n and F2p ,n) and the spin dependent (g1p ,n) structure functions of the nucleon on the Bjorken scaling variable x using the unpolarized distribution functions of the quarks q (x ) and the polarized distribution functions of the quarks Δ q (x ) respectively. The chiral constituent quark model, which is known to provide a satisfactory explanation of the proton spin crisis and related issues in the nonperturbative regime, has been used to compute explicitly the valence and sea quark flavor distribution functions of p and n . In light of the improved precision of the world data, the p and n longitudinal spin asymmetries [A1p(x ) and A1n(x )] have been calculated. The implication of the presence of the sea quarks has been discussed for the ratio of polarized to unpolarized quark distribution functions for up and down quarks in the p and n Δ/up(x ) up(x ) , Δ/dp(x ) dp(x ) , Δ/un(x ) un(x ) , and Δ/dn(x ) dn(x ) . The ratio of the n and p structure functions Rn p(x )=F/2n(x ) F2p(x ) has also been presented. The results have been compared with the recent available experimental observations. The results on the spin sum rule have also been included and compared with data and other recent approaches.
Generalized Ginzburg-Landau approach to inhomogeneous phases in nonlocal chiral quark models
NASA Astrophysics Data System (ADS)
Carlomagno, J. P.; Gómez Dumm, D.; Scoccola, N. N.
2015-05-01
We analyze the presence of inhomogeneous phases in the QCD phase diagram within the framework of nonlocal chiral quark models. We concentrate in particular in the positions of the tricritical (TCP) and Lifshitz (LP) points, which are studied in a general context using a generalized Ginzburg-Landau approach. We find that for all the phenomenologically acceptable model parametrizations considered the TCP is located at a higher temperature and a lower chemical potential in comparison with the LP. Consequently, these models seem to favor a scenario in which the onset of the first order transition between homogeneous phases is not covered by an inhomogeneous, energetically favored phase.
The nonstrange dibaryon and hidden-color effect in a chiral quark model
NASA Astrophysics Data System (ADS)
Dai, L. R.; Zhang, Y. N.; Sun, Y. L.; Shao, S. J.
2016-09-01
The exotic nonstrange ΔΔ dibaryon with I(JP) = 0(3+) has been confirmed by the experimental data reported by WASA-at-COSY Collaboration, and the result is consistent with our theoretical prediction in the chiral SU(3) quark model and extended chiral SU(3) quark model, showing that the effect from hidden-color channel ( CC is important. In the present work, we further investigate another exotic nonstrange ΔΔ dibaryon with I(JP) = 3(0+) in the chiral SU(3) quark model that describes the energies of baryon ground states and the nucleon-nucleon (NN) scattering data satisfactorily. We perform a dynamical coupled-channel study of the ΔΔ - CC system with I(JP) = 3(0+) within the framework of resonating group method (RGM). We find that the binding energy of I(JP) = 3(0+) state is about 22.3 MeV and a root-mean-square radius (RMS) of 1.03 fm in single-channel calculation. Then we extend the model to include the CC channel to further study the I(JP) = 3(0+) state and find that the binding energy is about 31.3 MeV and RMS is 0.97 fm in coupled-channel calculation. We can see that the CC channel coupling has a relatively large effect on this state. The color screening effect is further considered and we find that the bound state property will not change much. It is shown that the binding energy of this state is stably ranged around several tens of MeV; it means that its mass is always lower than the threshold of the ΔΔ channel and higher than the mass of NΔπ.
Pion-to-Photon Transition Distribution Amplitudes in the Non-Local Chiral Quark Model
NASA Astrophysics Data System (ADS)
Kotko, P.; Praszałowicz, M.
2009-01-01
We apply the non-local chiral quark model to study vector and axial pion-to-photon transition amplitudes that are needed as a nonperturbative input to estimate the cross-section of pion annihilation into the real and virtual photon. We use a simple form of the non-locality that allows to perform all calculations in the Minkowski space and guaranties polynomiality of the TDAs. We note only residual dependence on the precise form of the cut-off function, however vector TDA that is symmetric in skewedness parameter in the local quark model is no longer symmetric in the non-local case. We calculate also the transition form-factors and compare them with existing experimental parametrizations.
Calculation of screening masses in a chiral quark model
Li Xiangdong; Li Hu; Shakin, C.M.; Sun Qing
2004-10-01
We consider a simple model for the coordinate-space vacuum polarization function which is often parametrized in terms of a screening mass. We discuss the circumstances in which the value m{sub sc}={pi}T is obtained for the screening mass. In the model considered here, that result is obtained when the momenta in the relevant vacuum polarization integral are small with respect to the first Matsubara frequency.
Spin, masses and other baryonic observables in a chiral model of quark and gluon confinement
NASA Astrophysics Data System (ADS)
Stern, Jacqueline; Clément, Gérard
1989-11-01
The structure of non-strange baryons is investigated in a field-theoretical model which minimally incorporates soft confinement of quarks and gluons and approximate chiral symmetry. Baryonic states are recovered from the mean-field hedgehog solutions by the coherent cranking procedure, which generates mean chromomagnetic fields, modelling gluon exchange between quarks. The cranking method allows for a non-perturbative, self-consistent computation of gluonic effects on the nucleon and delta masses, corrected for spurious translational and rotational fluctuations, on the contribution Δu + Δd of the non-strange quark helicities to the proton spin, and on various other baryonic observables. For the physical values of the pion parameters mπ = 139.6 MeV, Fπ = 93 MeV, and the effective strong fine structure constant α s ⋍ 0.5 , the results which we obtain for these observables, including Δu + Δd ⋍ 0.26, are in good agreement with experiment.
Pion- and strangeness-baryon σ terms in the extended chiral constituent quark model
NASA Astrophysics Data System (ADS)
An, C. S.; Saghai, B.
2015-07-01
Within an extended chiral constituent quark formalism, we investigate contributions from all possible five-quark components in the octet baryons to the pion-baryon (σπ B) and strangeness-baryon (σs B) sigma terms: B ≡N ,Λ ,Σ ,Ξ . The probabilities of the quark-antiquark components in the ground-state baryon octet wave functions are calculated by taking the baryons to be admixtures of three- and five-quark components, with the relevant transitions handled via the 3P0 mechanism. Predictions for σπ B and σs B obtained by using input parameters taken from the literature are reported. Our results turn out to be, in general, consistent with the findings via lattice QCD and chiral perturbation theory.
A model with chiral quarks of electric charges -4/3 and 5/3
NASA Astrophysics Data System (ADS)
Alves, Alexandre; Barreto, E. Ramirez; Camargo, D. A.; Dias, A. G.
2013-07-01
We present a new model based on the SU(3)⨂SU(2)⨂U(1) symmetry, in which there is a new consistent set of chiral fermion fields that renders the model free from anomalies. The new fermions do not share the usual family structure of the Standard Model and some of them have exotic electric charges, as the quarks X and Y with electric charge 5 /3 and -4 /3, respectively. Interestingly, the model contains a new heavy neutral lepton which may be a dark matter candidate. Two Higgs doublets are present in our construction, so that two CP even scalars are present in the model particle spectrum. One of them is similar to the Standard Model Higgs boson, while the other one couples mainly with the new exotic fermions. We performed a discovery analysis showing that the 8 TeV LHC can find the Y quark from single and pair production with masses from 300 GeV up to ~ 750 GeV. We also show that the new spectrum does not contribute significantly to the oblique EW parameters, and that dangerous flavor changing neutral currents are suppressed. Characteristic signatures from the other new fermions in the model are also commented.
Pion pole light-by-light contribution to g-2 of the muon in a nonlocal chiral quark model
Dorokhov, Alexander E.; Broniowski, Wojciech
2008-10-01
We calculate the pion-pole term of the light-by-light contribution to the g-2 of the muon in the framework of an effective chiral quark model with instantonlike nonlocal quark-quark interaction. The full kinematic dependence of the pion-photon transition form factors is taken into account. The dependence of form factors on the pion virtuality decreases the result by about 15% in comparison to the calculation where this dependence is neglected. Further, it is demonstrated that the QCD constraints suggested by Melnikov and Vainshtein are satisfied within the model. The corresponding contributions originate from the box diagram as well from the pion-pole term. Our chiral nonlocal model result for the pion-pole light-by-light contribution to (g-2)/2 of the muon is (6.3-6.7)x10{sup -10}, which is in the ball park of other effective-model calculations.
Meson properties in a nonlocal SU(3) chiral quark model at finite temperature
Contrera, G. A.; Gomez Dumm, D.; Scoccola, N. N.
2010-11-12
Finite temperature meson properties are studied in the context of a nonlocal SU(3) quark model which includes flavor mixing and the coupling of quarks to the Polyakov loop (PL). We analyze the behavior of scalar and pseudoscalar meson masses and mixing angles, as well as quark-meson couplings and pseudoscalar meson decay constants.
Composite Models of Quarks and Leptons.
NASA Astrophysics Data System (ADS)
Geng, Chaoqiang
1987-09-01
We review the various constraints on composite models of quarks and leptons. Some dynamical mechanisms for chiral symmetry breaking in chiral preon models are discussed. We have constructed several "realistic candidate" chiral preon models satisfying complementarity between the Higgs and confining phases. The models predict three to four generations of ordinary quarks and leptons.
Ledwig, Tim; Silva, Antonio
2010-09-01
We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider 1/N{sub c} rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: {kappa}{sub T}{sup u}=3.56 and {kappa}{sub T}{sup d}=1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be {kappa}{sub T}{sup s}=0.2{approx}-0.2, that is compatible with zero. We also calculate the corresponding form factors {kappa}{sub T}{sup q}(Q{sup 2}) up to a momentum transfer Q{sup 2{<=}}1 GeV{sup 2} at a renormalization scale of 0.36 GeV{sup 2}.
Thermodynamics of quark matter with a chiral imbalance
NASA Astrophysics Data System (ADS)
Farias, Ricardo L. S.; Duarte, Dyana C.; Krein, Gastão; Ramos, Rudnei O.
2016-10-01
We show how a scheme of rewriting a divergent momentum integral can conciliate results obtained with the Nambu-Jona-Lasinio model and recent lattice results for the chiral transition in the presence of a chiral imbalance in quark matter. Purely vacuum contributions are separated from medium-dependent regularized momentum integrals in such a way that one is left with ultraviolet divergent momentum integrals that depend on vacuum quantities only. The scheme is applicable to other commonly used effective models to study quark matter with a chiral imbalance, it allows us to identify the source of their difficulties in reproducing the qualitative features of lattice results, and enhances their predictability and uses in other applications.
QCD phase transition with chiral quarks and physical quark masses.
Bhattacharya, Tanmoy; Buchoff, Michael I; Christ, Norman H; Ding, H-T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Renfrew, Dwight; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao
2014-08-22
We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)(3) and (11 fm)(3) and temperatures between 139 and 196 MeV. Each temperature is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD "phase transition" is not first order but a continuous crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV.
Chiral corrections to the vector and axial couplings of quarks and baryons
Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E.; Holstein, Barry R.
2008-06-01
We calculate chiral corrections to the semileptonic vector and axial quark coupling constants using a manifestly Lorentz covariant chiral quark approach up to order O(p{sup 4}) in the two- and three-flavor pictures. These couplings are then used in the evaluation of the corresponding couplings which govern the semileptonic transitions between octet baryon states. In the calculation of baryon matrix elements we use a general ansatz for the spatial form of the quark wave function, without referring to a specific realization of hadronization and confinement of quarks in baryons. Matching the physical amplitudes calculated within our approach to the model-independent predictions of baryon chiral perturbation theory allows us to deduce a connection between our parameters and those of baryon chiral perturbation theory.
Nam, Seung-il; Kim, Hyun-Chul
2006-10-01
We investigate the leading-twist light-cone distribution amplitudes for the pion and kaon based on the gauge-invariant nonlocal chiral quark model from the instanton vacuum in the presence of external axial-vector currents. We find that the nonlocal contribution from the gauge invariance has much effects on the pion distribution amplitudes, while it changes mildly the kaon ones. We also study the Gegenbauer moments of the distribution amplitudes and compare them with the empirical analysis of the CLEO data.
Combined analysis of the π-p →K0Λ , η n reactions in a chiral quark model
NASA Astrophysics Data System (ADS)
Xiao, Li-Ye; Ouyang, Fan; Wang, Kai-Lei; Zhong, Xian-Hui
2016-09-01
A combined analysis of the reactions π-p →K0Λ and η n is carried out with a chiral quark model. The data in the center-of-mass (c.m.) energy range from threshold up to W ≃1.8 GeV are reasonably described. For π-p →K0Λ , it is found that N (1535 ) S11 and N (1650 ) S11 play crucial roles near threshold. The N (1650 ) S11 resonance contributes to the reaction through configuration mixing with N (1535 ) S11 . The constructive interference between N (1535 ) S11 and N (1650 ) S11 is responsible for the peak structure around threshold in the total cross section. The n -pole, u -, and t -channel backgrounds provide significant contributions to the reaction as well. For the π-p →η n process, the "first peak" in the total cross section is dominated by N (1535 ) S11 , which has a sizeable destructive interference with N (1650 ) S11 . Around Pπ≃ 1.0 GeV/c (W ≃1.7 GeV), there seems to be a small bump structure in the total cross section, which might be explained by the interference between the u channel and N (1650 ) S11 . The N (1520 ) D13 resonance affects the angle distributions of the cross sections notably, although no obvious effects are seen in the total cross section. The role of P -wave state N (1720 ) P13 should be further confirmed by future experiments. If N (1720 ) P13 has a narrow width of Γ ≃120 MeV as found in our previous work by a study of the π0 photoproduction processes, obvious evidence should be seen in the π-p →K0Λ and η n processes as well. Finally, we give our predictions of the s -channel isospin-1/2 resonance contributions to the π N →π N reactions.
Chiral Symmetry and Hyperfine Quark-Antiquark Splittings
Felipe J. Llanes-Estrada; Stephen R. Cotanch; Adam P. Szczepaniak; Eric S. Swanson
2003-12-01
We briefly review theoretical calculations for the pseudoscalar-vector meson hyperfine splitting with no open flavor and also report a many body field theoretical effort to assess the impact of chiral symmetry in the choice of effective potentials for relativistic quark models. Our calculations predict the missing eta{sub b} meson to have mass near 9400 MeV. The radial excitation {eta}{sub c}(2S) is in agreement with the measurements of the BELLE and most recently BABAR collaborations.
Ideal quarks and mesons in the relativistic quark model
Kaneko, K. )
1994-05-01
We propose a microscopic theory for interacting mesons and ideal quarks in the relativistic quark model using the time-dependent mean-field theory technique. For simplicity we examined the Nambu--Jona-Lasinio model. The dynamical chiral-symmetry breaking leads to a zero-frequency mode (pion) due to the restoration of chiral symmetry. The ideal quarks are represented as dressed particles independent of mean fields, and do not have the conventional properties of fermions. This is due to the constraints of eliminating the double counting of degrees of freedom between the mean fields and quarks. The small fluctuation around the static solution is then investigated. The pseudoscalar and scalar mesons are represented as the collective modes of the mean fields.
Sea quark transverse momentum distributions and dynamical chiral symmetry breaking
Schweitzer, Peter; Strikman, Mark; Weiss, Christian
2014-01-01
Recent theoretical studies have provided new insight into the intrinsic transverse momentum distributions of valence and sea quarks in the nucleon at a low scale. The valence quark transverse momentum distributions (q - qbar) are governed by the nucleon's inverse hadronic size R{sup -1} ~ 0.2 GeV and drop steeply at large p{sub T}. The sea quark distributions (qbar) are in large part generated by non-perturbative chiral-symmetry breaking interactions and extend up to the scale rho{sup -1} ~ 0.6 GeV. These findings have many implications for modeling the initial conditions of perturbative QCD evolution of TMD distributions (starting scale, shape of p{sub T}. distributions, coordinate-space correlation functions). The qualitative difference between valence and sea quark intrinsic p{sub T}. distributions could be observed experimentally, by comparing the transverse momentum distributions of selected hadrons in semi-inclusive deep-inelastic scattering, or those of dileptons produced in pp and pbar-p scattering.
Santopinto, E.; Bijker, R.
2008-10-13
We present a new generation of unquenched quark models for baryons in which the effects of quark-antiquark pairs are taken into account in an explicit form via a microscopic, QCD-inspired, pair creation mechanism. As an application, we study the effect of quark-antiquark pairs on the spin of the proton.
NASA Astrophysics Data System (ADS)
Ruggieri, M.; Peng, G. X.
2016-05-01
In this article, we study spontaneous chiral symmetry breaking for quark matter in the background of static and homogeneous parallel electric field E and magnetic field B . We use a Nambu-Jona-Lasinio model with a local kernel interaction to compute the relevant quantities to describe chiral symmetry breaking at a finite temperature for a wide range of E and B . We study the effect of this background on the inverse catalysis of chiral symmetry breaking for E and B of the same order of magnitude. We then focus on the effect of the equilibration of chiral density n5 , produced dynamically by an axial anomaly on the critical temperature. The equilibration of n5 , a consequence of chirality-flipping processes in the thermal bath, allows for the introduction of the chiral chemical potential μ5, which is computed self-consistently as a function of the temperature and field strength by coupling the number equation to the gap equation and solving the two within an expansion in E /T2 , B /T2 , and μ52/T2 . We find that even if chirality is produced and equilibrates within a relaxation time τM , it does not change drastically the thermodynamics, with particular reference to the inverse catalysis induced by the external fields, as long as the average μ5 at equilibrium is not too large.
Chiral perturbation theory for staggered sea quarks and Ginsparg-Wilson valence quarks
Baer, Oliver; Bernard, Claude; Rupak, Gautam; Shoresh, Noam
2005-09-01
We study lattice QCD with staggered sea and Ginsparg-Wilson valence quarks. The Symanzik effective action for this mixed lattice theory, including the lattice spacing contributions of O(a{sup 2}), is derived. Using this effective theory we construct the leading-order chiral Lagrangian. The masses and decay constants of pseudoscalars containing two Ginsparg-Wilson valence quarks are computed at one-loop order.
Harada, Masayasu; Takemoto, Shinpei; Sasaki, Chihiro
2010-01-01
We explore general features of thermodynamic quantities and hadron mass spectra in a possible phase where chiral SU(2){sub L}xSU(2){sub R} symmetry is spontaneously broken while its center Z{sub 2} symmetry remains unbroken. In this phase, chiral symmetry breaking is driven by a quartic quark condensate although a bilinear quark condensate vanishes. A Ginzburg-Landau free energy leads to a new tricritical point between the Z{sub 2} broken and unbroken phases. Furthermore, a critical point can appear even in the chiral limit where explicit breaking is turned off, instead of a tricritical point at which restoration of chiral and its center symmetries takes place simultaneously. The net quark number density exhibits an abrupt change near the restoration of the center symmetry rather than that of the chiral symmetry. Hadron masses in possible phases are also studied in a linear sigma model. We show that, in the Z{sub 2} symmetric phase, the qq-type scalar meson with zero isospin I=0 splits from the qq-type pseudoscalar meson with I=1.
Quark confinement in a constituent quark model
Langfeld, K.; Rho, M.
1995-07-01
On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model`s phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density.
Ledwig, Tim; Kim, Hyun-Chul; Goeke, Klaus
2008-09-01
We investigate the axial-vector transition constants of the baryon antidecuplet to the octet and decuplet within the framework of the self-consistent SU(3) chiral quark-soliton model. Taking into account rotational 1/N{sub c} and linear m{sub s} corrections and using the symmetry-conserving quantization, we calculate the axial-vector transition constants. It is found that the leading-order contributions are generally almost canceled by the rotational 1/N{sub c} corrections. Thus, the m{sub s} corrections turn out to be essential contributions to the axial-vector constants. The decay width of the {theta}{sup +}{yields}NK transition is determined to be {gamma}({theta}{yields}NK)=0.71 MeV, based on the result of the axial-vector transition constant g{sub A}*({theta}{yields}NK)=0.05. In addition, other strong decays of the baryon antidecuplet are investigated. The forbidden decays from the baryon antidecuplet to the decuplet are also studied.
Chiral symmetry, constituent quarks and quasi-elastic electron-nucleus scattering
NASA Astrophysics Data System (ADS)
Henley, E. M.; Krein, G.
1989-11-01
The effects of chiral symmetry breaking are examined for quasi-elastic electron scattering on nuclei. Nucleons are assumed to be composed of constituent quarks with masses that depend on density. This density dependence is determined on the basis of the Nambu-Jona-Lasinio model. It is found that the effects of chiral symmetry breaking are in the right direction and the right order of magnitude to explain the discrepancies between theory and experiment. On leave from Departamento de Fisica, Universidade Federal de Santa Maria, 97100 Santa Maria, R.S., Brazil.
Nucleon sigma term and strange quark content from lattice QCD with exact chiral symmetry
Ohki, H.; Fukaya, H.; Hashimoto, S.; Kaneko, T.; Yamada, N.; Matsufuru, H.; Noaki, J.; Shintani, E.; Onogi, T.
2008-09-01
We calculate the nucleon sigma term in two-flavor lattice QCD utilizing the Feynman-Hellman theorem. Both sea and valence quarks are described by the overlap fermion formulation, which preserves exact chiral and flavor symmetries on the lattice. We analyze the lattice data for the nucleon mass using the analytical formulae derived from the baryon chiral perturbation theory. From the data at valence quark mass set different from sea quark mass, we may extract the sea quark contribution to the sigma term, which corresponds to the strange quark content. We find that the strange quark content is much smaller than the previous lattice calculations and phenomenological estimates.
Quark interchange model of baryon interactions
Maslow, J.N.
1983-01-01
The strong interactions at low energy are traditionally described by meson field theories treating hadrons as point-like particles. Here a mesonic quark interchange model (QIM) is presented which takes into account the finite size of the baryons and the internal quark structure of hadrons. The model incorporates the basic quark-gluon coupling of quantum chromodynamics (QCD) and the MIT bag model for color confinement. Because the quark-gluon coupling constant is large and it is assumed that confinement excludes overlap of hadronic quark bags except at high momenta, a non-perturbative method of nuclear interactions is presented. The QIM allows for exchange of quark quantum numbers at the bag boundary between colliding hadrons mediated at short distances by a gluon exchange between two quarks within the hadronic interior. This generates, via a Fierz transformation, an effective space-like t channel exchange of color singlet (q anti-q) states that can be identified with the low lying meson multiplets. Thus, a one boson exchange (OBE) model is obtained that allows for comparison with traditional phenomenological models of nuclear scattering. Inclusion of strange quarks enables calculation of YN scattering. The NN and YN coupling constants and the nucleon form factors show good agreement with experimental values as do the deuteron low energy data and the NN low energy phase shifts. Thus, the QIM provides a simple model of strong interactions that is chirally invariant, includes confinement and allows for an OBE form of hadronic interaction at low energies and momentum transfers.
Molecular model for chirality phenomena
NASA Astrophysics Data System (ADS)
Latinwo, Folarin; Stillinger, Frank H.; Debenedetti, Pablo G.
2016-10-01
Chirality is a hallmark feature for molecular recognition in biology and chemical physics. We present a three-dimensional continuum model for studying chirality phenomena in condensed phases using molecular simulations. Our model system is based upon a simple four-site molecule and incorporates non-trivial kinetic behavior, including the ability to switch chirality or racemize, as well as thermodynamics arising from an energetic preference for specific chiral interactions. In particular, we introduce a chiral renormalization parameter that can locally favor either homochiral or heterochiral configurations. Using this model, we explore a range of chirality-specific phenomena, including the kinetics of chiral inversion, the mechanism of spontaneous chiral symmetry breaking in the liquid, chirally driven liquid-liquid phase separation, and chiral crystal structures.
Petreczky P.; Bazavov, A.
2011-10-11
We report preliminary results on the chiral and deconfinement aspects of the QCD transition at finite temperature using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent of N{sub {tau}} = 6 and 8. The chiral aspects of the transition are studied in terms of quark condensates and the disconnected chiral susceptibility. We study the deconfinement transition in terms of the strange quark number susceptibility and the renormalized Polyakov loop. We made continuum estimates for some quantities and find reasonably good agreement between our results and the recent continuum extrapolated results obtained with the stout staggered quark action.
Alkofer, Reinhard; Fischer, Christian S. Llanes-Estrada, Felipe J.; Schwenzer, Kai
2009-01-15
The infrared behavior of the quark-gluon vertex of quenched Landau gauge QCD is studied by analyzing its Dyson-Schwinger equation. Building on previously obtained results for Green functions in the Yang-Mills sector, we analytically derive the existence of power-law infrared singularities for this vertex. We establish that dynamical chiral symmetry breaking leads to the self-consistent generation of components of the quark-gluon vertex forbidden when chiral symmetry is forced to stay in the Wigner-Weyl mode. In the latter case the running strong coupling assumes an infrared fixed point. If chiral symmetry is broken, either dynamically or explicitly, the running coupling is infrared divergent. Based on a truncation for the quark-gluon vertex Dyson-Schwinger equation which respects the analytically determined infrared behavior, numerical results for the coupled system of the quark propagator and vertex Dyson-Schwinger equation are presented. The resulting quark mass function as well as the vertex function show only a very weak dependence on the current quark mass in the deep infrared. From this we infer by an analysis of the quark-quark scattering kernel a linearly rising quark potential with an almost mass independent string tension in the case of broken chiral symmetry. Enforcing chiral symmetry does lead to a Coulomb type potential. Therefore, we conclude that chiral symmetry breaking and confinement are closely related. Furthermore, we discuss aspects of confinement as the absence of long-range van der Waals forces and Casimir scaling. An examination of experimental data for quarkonia provides further evidence for the viability of the presented mechanism for quark confinement in the Landau gauge.
The Quark's Model and Confinement
ERIC Educational Resources Information Center
Novozhilov, Yuri V.
1977-01-01
Quarks are elementary particles considered to be components of the proton, the neutron, and others. This article presents the quark model as a mathematical concept. Also discussed are gluons and bag models. A bibliography is included. (MA)
Generalized simplicial chiral models
NASA Astrophysics Data System (ADS)
Alimohammadi, Masoud
2000-02-01
Using the auxiliary field representation of the simplicial chiral models on a ( d-1)-dimensional simplex, the simplicial chiral models are generalized through replacing the term Tr (AA †) in the Lagrangian of these models by an arbitrary class function of AA †; V(AA †) . This is the same method used in defining the generalized two-dimensional Yang-Mills theories (gYM 2) from ordinary YM 2. We call these models the "generalized simplicial chiral models". Using the results of the one-link integral over a U( N) matrix, the large- N saddle-point equations for eigenvalue density function ρ( z) in the weak ( β> βc) and strong ( β< βc) regions are computed. In d=2, where the model is in some sense related to the gYM 2 theory, the saddle-point equations are solved for ρ( z) in the two regions, and the explicit value of critical point βc is calculated for V(B)= Tr B n(B=AA †) . For V(B)= Tr B 2, Tr B 3, and Tr B4, the critical behaviour of the model at d=2 is studied, and by calculating the internal energy, it is shown that these models have a third order phase transition.
The NJL Model for Quark Fragmentation Functions
T. Ito, W. Bentz, I. Cloet, A W Thomas, K. Yazaki
2009-10-01
A description of fragmentation functions which satisfy the momentum and isospin sum rules is presented in an effective quark theory. Concentrating on the pion fragmentation function, we first explain the reason why the elementary (lowest order) fragmentation process q → qπ is completely inadequate to describe the empirical data, although the “crossed” process π → qq describes the quark distribution functions in the pion reasonably well. Then, taking into account cascade-like processes in a modified jet-model approach, we show that the momentum and isospin sum rules can be satisfied naturally without introducing any ad-hoc parameters. We present numerical results for the Nambu-Jona-Lasinio model in the invariant mass regularization scheme, and compare the results with the empirical parametrizations. We argue that this NJL-jet model provides a very useful framework to calculate the fragmentation functions in an effective chiral quark theory.
Explicit versus Dynamical Chiral Symmetry Breaking and Mass Matrix of Quarks and Leptons
NASA Astrophysics Data System (ADS)
Handa, O.; Ishida, S.; Sekiguchi, M.
1992-02-01
By recourse to an analogy between strong and weak interactions, quark mass-matrices consisting of the two parts are proposed, which represent, respectively, dynamical chiral symmetry breaking and explicit one due to small preon mass. The sum rules among quark masses and mixing-matrix elements derived from it seem consistent with present experiments.
Nonfactorization of four-quark condensates at low energies within chiral perturbation theory
Gomez Nicola, A.; Pelaez, J. R.; Ruiz de Elvira, J.
2010-10-01
Four-quark correlators and the factorization hypothesis are analyzed in the meson sector within chiral perturbation theory. We define the four-quark condensate as lim{sub x{yields}0}
Chiral electric separation effect in the quark-gluon plasma
Jiang, Yin; Liao, Jinfeng; Huang, Xu-Guang
2015-02-02
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient σχe, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current JA that is generated in response to an externally applied electric field eE: JA=σχe(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure σχe∝μμ5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density μ5 ≠ 0. Using the Hard-Thermal-Loop framework, the CESEmore » conductivity for the QGP is found to be σχe = (#)TTrfQeQA/g⁴ln(1/g) μμ5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.« less
Chiral electric separation effect in the quark-gluon plasma
Jiang, Yin; Liao, Jinfeng; Huang, Xu-Guang
2015-02-02
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient σ_{χe}, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current J_{A} that is generated in response to an externally applied electric field eE: J_{A}=σ_{χe}(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure σ_{χe}∝μμ5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density μ5 ≠ 0. Using the Hard-Thermal-Loop framework, the CESE conductivity for the QGP is found to be σ_{χe} = (#)TT_{rf}Q_{e}Q_{A}/g⁴ln(1/g) μμ5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.
Electromagnetic field and the chiral magnetic effect in the quark-gluon plasma
NASA Astrophysics Data System (ADS)
Tuchin, Kirill
2015-06-01
Time evolution of an electromagnetic field created in heavy-ion collisions strongly depends on the electromagnetic response of the quark-gluon plasma, which can be described by the Ohmic and chiral conductivities. The latter is intimately related to the chiral magnetic effect. I argue that a solution to the classical Maxwell equations at finite chiral conductivity is unstable due to the soft modes k <σχ that grow exponentially with time. In the kinematical region relevant for the relativistic heavy-ion collisions, I derive analytical expressions for the magnetic field of a point charge. I show that finite chiral conductivity causes oscillations of magnetic field at early times.
Chiral matrix model of the semi-QGP in QCD
NASA Astrophysics Data System (ADS)
Pisarski, Robert D.; Skokov, Vladimir V.
2016-08-01
Previously, a matrix model of the region near the transition temperature, in the "semi"quark gluon plasma, was developed for the theory of S U (3 ) gluons without quarks. In this paper we develop a chiral matrix model applicable to QCD by including dynamical quarks with 2 +1 flavors. This requires adding a nonet of scalar fields, with both parities, and coupling these to quarks through a Yukawa coupling, y . Treating the scalar fields in mean field approximation, the effective Lagrangian is computed by integrating out quarks to one loop order. As is standard, the potential for the scalar fields is chosen to be symmetric under the flavor symmetry of S U (3 )L×S U (3 )R×Z (3 )A, except for a term linear in the current quark mass, mqk. In addition, at a nonzero temperature T it is necessary to add a new term, ˜mqkT2. The parameters of the gluon part of the matrix model are identical to those for the pure glue theory without quarks. The parameters in the chiral matrix model are fixed by the values, at zero temperature, of the pion decay constant and the masses of the pions, kaons, η , and η'. The temperature for the chiral crossover at Tχ=155 MeV is determined by adjusting the Yukawa coupling y . We find reasonable agreement with the results of numerical simulations on the lattice for the pressure and related quantities. In the chiral limit, besides the divergence in the chiral susceptibility there is also a milder divergence in the susceptibility between the Polyakov loop and the chiral order parameter, with critical exponent β -1 . We compute derivatives with respect to a quark chemical potential to determine the susceptibilities for baryon number, the χ2 n. Especially sensitive tests are provided by χ4-χ2 and by χ6, which changes in sign about Tχ. The behavior of the susceptibilities in the chiral matrix model strongly suggests that as the temperature increases from Tχ, that the transition to deconfinement is significantly quicker than indicated by the
Chiral symmetry breaking and quark confinement in the nilpotency expansion of QCD
Caracciolo, Sergio; Palumbo, Fabrizio
2011-06-01
We apply to lattice QCD a bosonization method previously developed in which dynamical bosons are generated by time-dependent Bogoliubov transformations. The transformed action can be studied by an expansion in the inverse of the nilpotency index, which is the number of fermionic states in the structure function of composite bosons. When this number diverges the model is solved by the saddle-point method which has a variational interpretation. We give a stationary covariant solution for a background matter field whose fluctuations describe mesons. In the saddle-point approximation fermionic quasiparticles exist which have quark quantum numbers. They are confined in the sense that they propagate only in pointlike color singlets. Conditions for chiral symmetry breaking are determined, to be studied numerically, and a derivation of a mesons-nucleons action is outlined.
Rahaman, Anisur
2015-10-15
The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson.
The chiral phase transition for lattice QCD with 2 color-sextet quarks
NASA Astrophysics Data System (ADS)
Kogut, J. B.; Sinclair, D. K.
2015-09-01
QCD with 2 flavors of massless color-sextet quarks is studied as a possible walking-Technicolor candidate. We simulate the lattice version of this model at finite temperatures near to the chiral-symmetry restoration transition, to determine whether it is indeed a walking theory (QCD-like with a running coupling which evolves slowly over an appreciable range of length scales) or if it has an infrared fixed point, making it a conformal field theory. The lattice spacing at this transition is decreased towards zero by increasing the number Nt of lattice sites in the temporal direction. Our simulations are performed at Nt=4 ,6 ,8 ,12 , on lattices with spatial extent much larger than the temporal extent. A range of small fermion masses is chosen to make predictions for the chiral (zero mass) limit. We find that the bare lattice coupling does decrease as the lattice spacing is decreased. However, it decreases more slowly than would be predicted by asymptotic freedom. We discuss whether this means that the coupling is approaching a finite value as lattice Nt is increased—the conformal option, or if the apparent disagreement with the scaling predicted by asymptotic freedom is because the lattice coupling is a poor expansion parameter, and the theory walks. Currently, evidence favors QCD with 2 color-sextet quarks being a conformal field theory. Other potential sources of disagreement with the walking hypothesis are also discussed. We also report an estimate of the position of the deconfinement transition for Nt=12 , needed for choosing parameters for zero-temperature simulations.
Stability of Quark Star Models
NASA Astrophysics Data System (ADS)
Azam, M.; Mardan, S. A.; Rehman, M. A.
2016-05-01
In this paper, we investigate the stability of quark stars with four different types of inner matter configurations; isotropic, charged isotropic, anisotropic and charged anisotropic by using the concept of cracking. For this purpose, we have applied local density perturbations technique to the hydrostatic equilibrium equation as well as on physical parameters involved in the model. We conclude that quark stars become potentially unstable when inner matter configuration is changed and electromagnetic field is applied.
Exploring the chiral regime of QCD in the interacting instanton liquid model
Cristoforetti, M.; Faccioli, P.; Traini, M. C.; Negele, J. W.
2007-02-01
The interacting instanton liquid model (IILM) is used to explore the role of instanton-induced dynamics in hadron structure. To support the validity of this model in the chiral regime, the quark mass dependencies of several properties are shown to agree with chiral perturbation theory, including the density of eigenmodes of the Dirac operator and the mass of the pion. A quark mass m*=80 MeV emerging naturally from the model is shown to specify the mass scale above which the fermion determinant is suppressed, the zero modes become subdominant, and the density of quasizero modes become independent of the quark mass.
NASA Astrophysics Data System (ADS)
Alexandru, Andrei; Horváth, Ivan
2016-01-01
The validity of recently proposed equivalence between valence spontaneous chiral symmetry breaking (vSChSB) and chiral polarization of low energy Dirac spectrum (ChP) in SU(3) gauge theory, is examined for the case of twelve mass-degenerate fundamental quark flavors. We find that the vSChSB-ChP correspondence holds for regularized systems studied. Moreover, our results suggest that vSChSB occurs in two qualitatively different circumstances: there is a quark mass mc such that for m > mc the mode condensing Dirac spectrum exhibits standard monotonically increasing density, while for mch < m < mc the peak around zero separates from the bulk of the spectrum, with density showing a pronounced depletion at intermediate scales. Valence chiral symmetry restoration may occur at yet smaller masses m < mch, but this has not yet been seen by overlap valence probe, leaving the mch = 0 possibility open. The latter option could place massless Nf=12 theory outside of conformal window. Anomalous behavior of overlap Dirac spectrum for mch < m < mc is qualitatively similar to one observed previously in zero and few-flavor theories as an effect of thermal agitation.
Martynov, M. V. Smirnov, A. D.
2012-03-15
A gauge model featuring a chiral color symmetry of quarks was considered, and possible manifestations of this symmetry in proton-antiproton and proton-proton collisions at the Tevatron and LHC energies were studied. The cross section {sigma}{sub tt}-bar for the production of tt-bar quark pairs at the Tevatron and the forward-backward asymmetry A{sub FB}{sup pp}-bar in this process were calculated and analyzed with allowance for the contributions of the G Prime -boson predicted by the chiral color symmetry of quarks, the G Prime -boson massm{sub G Prime} and the mixing angle {theta}{sub G} being treated as free parameters of the model. Limits on m{sub G Prime} versus {theta}{sub G} were studied on the basis of data from the Tevatron on {sigma}{sub tt}-bar and A{sub FB}{sup pp}-bar, and the region compatible with these data within one standard deviation was found in the m{sub G Prime }-{theta}{sub G} plane. The region ofm{sub G Prime }-mass values that is appropriate for observing the G Prime -boson at LHC is discussed.
Transversity quark distributions in a covariant quark-diquark model
I.C. Cloet; W. Bentz; A.W. Thomas
2008-01-01
Transversity quark light-cone momentum distributions are calculated for the nucleon. We utilize a modified Nambu--Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the relativistic Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. Particular attention is paid to comparing our results with the recent experimental extraction of the transversity distributions by Anselmino et al. We also compare our transversity results with earlier spin-independent and helicity quark distributions calculated in the same approach.
Kaon B parameter with the Wilson quark action using chiral Ward identities
NASA Astrophysics Data System (ADS)
Aoki, S.; Fukugita, M.; Hashimoto, S.; Ishizuka, N.; Iwasaki, Y.; Kanaya, K.; Kuramashi, Y.; Okawa, M.; Ukawa, A.; Yoshié, T.
1999-08-01
A lattice QCD calculation of the kaon B parameter BK is carried out with the Wilson quark action in the quenched approximation at β=6/g2=5.9-6.5. The mixing problem of the Δs=2 four-quark operators is solved nonperturbatively with full use of chiral Ward identities employing four external quarks with an equal off-shell momentum in the Landau gauge. This method, without invoking any effective theory, enables us to construct the weak four-quark operators exhibiting good chiral behavior. Our results for BK with the nonperturbative mixing coefficients show small scaling violation beyond the lattice cutoff a-1~2.5 GeV. Our estimate concludes BK(NDR,2 GeV)=0.69(7) at a-1=2.7-4.3 GeV, which agrees with the value obtained with the Kogut-Susskind quark action. For comparison we also calculate BK with one-loop perturbative mixing coefficients. While this yields incorrect values at finite lattice spacing, a linear extrapolation to the continuum limit as a function of a leads to a result consistent with those obtained with the Ward identity method.
Quark models of dibaryon resonances in nucleon-nucleon scattering
Ping, J. L.; Huang, H. X.; Pang, H. R.; Wang Fan; Wong, C. W.
2009-02-15
We look for {delta}{delta} and N{delta} resonances by calculating NN scattering phase shifts of two interacting baryon clusters of quarks with explicit coupling to these dibaryon channels. Two phenomenological nonrelativistic chiral quark models giving similar low-energy NN properties are found to give significantly different dibaryon resonance structures. In the chiral quark model (ChQM), the dibaryon system does not resonate in the NNS waves, in agreement with the experimental SP07 NN partial-wave scattering amplitudes. In the quark delocalization and color screening model (QDCSM), the S-wave NN resonances disappear when the nucleon size b falls below 0.53 fm. Both quark models give an IJ{sup P}=03{sup +}{delta}{delta} resonance. At b=0.52 fm, the value favored by the baryon spectrum, the resonance mass is 2390 (2420) MeV for the ChQM with quadratic (linear) confinement, and 2360 MeV for the QDCSM. Accessible from the {sup 3}D{sub 3}{sup NN} channel, this resonance is a promising candidate for the known isoscalar ABC structure seen more clearly in the pn{yields}d{pi}{pi} production cross section at 2410 MeV in the recent preliminary data reported by the CELSIUS-WASA Collaboration. In the isovector dibaryon sector, our quark models give a bound or almost bound {sup 5}S{sub 2}{sup {delta}}{sup {delta}} state that can give rise to a {sup 1}D{sub 2}{sup NN} resonance. None of the quark models used have bound N{delta}P states that might generate odd-parity resonances.
Fluid-Gravity Model for the Chiral Magnetic Effect
Kalaydzhyan, Tigran; Kirsch, Ingo
2011-05-27
We consider the STU model as a gravity dual of a strongly coupled plasma with multiple anomalous U(1) currents. In the bulk we add additional background gauge fields to include the effects of external electric and magnetic fields on the plasma. Reducing the number of chemical potentials in the STU model to two and interpreting them as quark and chiral chemical potential, we obtain a holographic description of the chiral magnetic and chiral vortical effects (CME and CVE) in relativistic heavy-ion collisions. These effects formally appear as first-order transport coefficients in the electromagnetic current. We compute these coefficients from our model using fluid-gravity duality. We also find analogous effects in the axial-vector current. Finally, we briefly discuss a variant of our model, in which the CME/CVE is realized in the late-time dynamics of an expanding plasma.
Fluid-gravity model for the chiral magnetic effect.
Kalaydzhyan, Tigran; Kirsch, Ingo
2011-05-27
We consider the STU model as a gravity dual of a strongly coupled plasma with multiple anomalous U(1) currents. In the bulk we add additional background gauge fields to include the effects of external electric and magnetic fields on the plasma. Reducing the number of chemical potentials in the STU model to two and interpreting them as quark and chiral chemical potential, we obtain a holographic description of the chiral magnetic and chiral vortical effects (CME and CVE) in relativistic heavy-ion collisions. These effects formally appear as first-order transport coefficients in the electromagnetic current. We compute these coefficients from our model using fluid-gravity duality. We also find analogous effects in the axial-vector current. Finally, we briefly discuss a variant of our model, in which the CME/CVE is realized in the late-time dynamics of an expanding plasma. PMID:21699286
Strange quark matter and quark stars with the Dyson-Schwinger quark model
NASA Astrophysics Data System (ADS)
Chen, H.; Wei, J.-B.; Schulze, H.-J.
2016-09-01
We calculate the equation of state of strange quark matter and the interior structure of strange quark stars in a Dyson-Schwinger quark model within rainbow or Ball-Chiu vertex approximation. We emphasize constraints on the parameter space of the model due to stability conditions of ordinary nuclear matter. Respecting these constraints, we find that the maximum mass of strange quark stars is about 1.9 solar masses, and typical radii are 9-11km. We obtain an energy release as large as 3.6 × 10^{53} erg from conversion of neutron stars into strange quark stars.
Large degeneracy of excited hadrons and quark models
Bicudo, P.
2007-11-01
The pattern of a large approximate degeneracy of the excited hadron spectra (larger than the chiral restoration degeneracy) is present in the recent experimental report of Bugg. Here we try to model this degeneracy with state of the art quark models. We review how the Coulomb Gauge chiral invariant and confining Bethe-Salpeter equation simplifies in the case of very excited quark-antiquark mesons, including angular or radial excitations, to a Salpeter equation with an ultrarelativistic kinetic energy with the spin-independent part of the potential. The resulting meson spectrum is solved, and the excited chiral restoration is recovered, for all mesons with J>0. Applying the ultrarelativistic simplification to a linear equal-time potential, linear Regge trajectories are obtained, for both angular and radial excitations. The spectrum is also compared with the semiclassical Bohr-Sommerfeld quantization relation. However, the excited angular and radial spectra do not coincide exactly. We then search, with the classical Bertrand theorem, for central potentials producing always classical closed orbits with the ultrarelativistic kinetic energy. We find that no such potential exists, and this implies that no exact larger degeneracy can be obtained in our equal-time framework, with a single principal quantum number comparable to the nonrelativistic Coulomb or harmonic oscillator potentials. Nevertheless we find it plausible that the large experimental approximate degeneracy will be modeled in the future by quark models beyond the present state of the art.
ERIC Educational Resources Information Center
Young, Robert D.
1973-01-01
Discusses the charge independence, wavefunctions, magnetic moments, and high-energy scattering of hadrons on the basis of group theory and nonrelativistic quark model with mass spectrum calculated by first-order perturbation theory. The presentation is explainable to advanced undergraduate students. (CC)
The Unquenching of the Quark Model
Santopinto, Elena; Bijker, Roelof
2011-05-24
We present an unquenched quark model for baryons in which the effects of quark-antiquark pair creation (uu-bar, dd and ss-bar) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. As an application we discuss the flavor content of octet baryons.
Brazovskii-Dyugaev effect on the inhomogeneous chiral transition in quark matter
NASA Astrophysics Data System (ADS)
Karasawa, Shintaro; Lee, Tong-Gyu; Tatsumi, Toshitaka
2016-04-01
We investigate the effects of quantum and thermal fluctuations on the phase boundary between the inhomogeneous chiral phase and the chiral-restored phase in the phase diagram in the plane of temperature and chemical potential. Introducing the composite fields made of quark bilinear fields, we construct an effective action for them in quark matter by way of the correlation function method. Utilizing this effective action, we discuss the effects of the quark-antiquark and particle-hole pair fluctuations to find possible modifications of the vertex functions of the order parameter included in the thermodynamic potential. We find that the most important effect of the pair fluctuations is to change the sign of the fourth-order vertex function to make the phase transition always the first, rather than the second, order (we call it the Brazovskii-Dyugaev effect). Another important effect manifests in the second-order vertex function: it exhibits a singular behavior near the critical point, which prohibits the second-order phase transition. It, together with the fourth-order vertex function, alters the location of the phase boundary.
CHIRAL LIMIT AND LIGHT QUARK MASSES IN 2+1 FLAVOR DOMAIN WALL QCD.
SCHOLZ,E.; LIN, M.
2007-07-30
We present results for meson masses and decay constants measured on 24{sup 3} x 64 lattices using the domain wall fermion formulation with an extension of the fifth dimension of L{sub s} = 16 for N{sub f} 2 + 1 dynamical quark flavors. The lightest dynamical meson mass in our set-up is around 331MeV. while partially quenched mesons reach masses as low as 250MeV. The applicability of SU(3) x SU(3) and SU(2) x SU(2) (partially quenched) chiral perturbation theory will be compared and we quote values for the low-energy constants from both approaches. We will extract the average light quark and strange quark masses and use a non-perturbative renormalization technique (RI/MOM) to quote their physical values. The pion and kaon decay constants are determined at those values from our chiral fits and their ratio is used to obtain the CKM-matrix element |V{sub us}|. The results presented here include statistical errors only.
Confining quark condensate model of the nucleon.
Frank, Michael; Tandy, Peter
1992-07-01
We obtain a mean-field solution for the nucleon as a quark-meson soliton obtained from the action of the global color-symmetry model of QCD. All dynamics is generated from an effective interaction of quark currents. At the quark-meson level there are two novel features: (1) absolute confinement is produced from the space-time structure of the dynamical self-energy in the vacuum quark propagator; and (2) the related scalar meson field is an extended q-barq composite that couples nonlocally to quarks. The influence of these features upon the nucleon mass contributions and other nucleon properties is presented.
The paradigm of Pseudodual Chiral Models
Zachos, C.K.; Curtright, T.L.
1994-08-01
This is a synopsis and extension of Phys. Rev. D49 5408 (1994). The Pseudodual Chiral Model illustrates 2-dimensional field theories which possess an infinite number of conservation laws but also allow particle production, at variance with naive expectations-a folk theorem of integrable models. We monitor the symmetries of the pseudodual model, both local and nonlocal, as transmutations of the symmetries of the (very different) usual Chiral Model. We refine the conventional algorithm to more efficiently produce the nonlocal symmetries of the model. We further find the canonical transformation which connects the usual chiral model to its fully equivalent dual model, thus contradistinguishing the pseudodual theory.
Radiatively induced quark and lepton mass model
NASA Astrophysics Data System (ADS)
Nomura, Takaaki; Okada, Hiroshi
2016-10-01
We propose a radiatively induced quark and lepton mass model in the first and second generation with extra U (1) gauge symmetry and vector-like fermions. Then we analyze the allowed regions which simultaneously satisfy the FCNCs for the quark sector, LFVs including μ- e conversion, the quark mass and mixing, and the lepton mass and mixing. Also we estimate the typical value for the (g - 2) μ in our model.
NASA Astrophysics Data System (ADS)
Senju, H.
1991-07-01
Inspired by unique features of the preon-subpreon model, we propose a new scheme for quark mixing. In our scheme, the mass relations m_{d} << m_{s} << m_{b} and m_{u} << m_{c} << m_{t} are naturally understood. The resultant CKM matrix has very nice properties. The fact that |V_{us}| and |V_{cd}| are remarkably large compared with other off-diagonal elements is naturally understood. |V_{cb}| =~ |V_{ts}| is predicted and their small values are explained. |V_{ub}| and |V_{td}| are predicted to be much smaller than |V_{cb}|. The parametrization invariant measure of CP violation, J, is predicted to be |V_{ud}| |V_{ub}| |V_{td}| sin phi. The mass relations and mixings of q', q'', l_{s} and leptons are also discussed.
Single Spin Asymmetry in Strongly Correlated Quark Model
Musulmanbekov, G.
2007-06-13
The Single Transverse - Spin Asymmetry (SSA) is analysed in the framework of the Strongly Correlated Quark Model proposed by author, where the proton spin emerges from the orbital momenta of quark and qluon condensates circulating around the valence quarks. It is shown that dominating factors of appearance of SSA are the orbiting around the valence quarks sea quark and qluon condensates and spin dependent quark-quark cross sections.
Top quark forward-backward asymmetry from the 3-3-1 model
NASA Astrophysics Data System (ADS)
Barreto, E. Ramirez; Coutinho, Y. A.; Sá Borges, J.
2011-03-01
The forward-backward asymmetry AFB in top quark pair production, measured at the Tevatron, is probably related to the contribution of new particles. The Tevatron result is more than a 2σ deviation from the standard model prediction and motivates the application of alternative models introducing new states. However, as the standard model predictions for the total cross section σtt and invariant mass distribution Mtt for this process are in good agreement with experiments, any alternative model must reproduce these predictions. These models can be placed into two categories: One introduces the s-channel exchange of new vector bosons with chiral couplings to the light quarks and to the top quark, and another relies on the t-channel exchange of particles with large flavor-violating couplings in the quark sector. In this work, we employ a model which introduces both s- and t-channel nonstandard contributions for the top quark pair production in proton-antiproton collisions. We use the minimal version of the SU(3)C⊗SU(3)L⊗U(1)X model (3-3-1 model) that predicts the existence of a new neutral gauge boson, called Z'. This gauge boson has both flavor-changing couplings to up and top quarks and chiral coupling to the light quarks and to the top quark. This very peculiar model coupling can correct the AFB for top quark pair production for two ranges of Z' mass while leading to a cross section and invariant mass distribution quite similar to the standard model ones. This result reinforces the role of the 3-3-1 model for any new physics effect.
Quark Model in the Quantum Mechanics Curriculum.
ERIC Educational Resources Information Center
Hussar, P. E.; And Others
1980-01-01
This article discusses in detail the totally symmetric three-quark karyonic wave functions. The two-body mesonic states are also discussed. A brief review of the experimental efforts to identify the quark model multiplets is given. (Author/SK)
Direct mass limits for chiral fourth-generation quarks in all mixing scenarios.
Flacco, Christian J; Whiteson, Daniel; Tait, Tim M P; Bar-Shalom, Shaouly
2010-09-10
Present limits on chiral fourth-generation quark masses mb' and mt' are broadly generalized and strengthened by combining both t' and b' decays and considering a full range of t' and b' flavor-mixing scenarios with the lighter generations (to 1-‖V44‖2≈10(-13)). Various characteristic mass-splitting choices are considered. With mt'>mb' we find that CDF Collaboration limits on the b' mass vary by no more than 10%-20% with any choice of flavor mixing, while for the t' mass, we typically find stronger bounds, in some cases up to mt'>430 GeV. For mb'>mt', we find mb'>380-430 GeV, depending on the flavor mixing and the size of the mt'-mb' mass splitting.
A Molecular Model for Chiral Symmetry Breaking
NASA Astrophysics Data System (ADS)
Latinwo, Folarin; Stillinger, Frank; Debenedetti, Pablo
In this work, we present a new class of molecular models for chiral phenomena in condensed matter systems. A key feature of these models is the ability of the four-site (tetramer) ``molecules'' to inter-convert between two distinct chiral forms (enantiomers). Given this feature, we use analytical theory and computer simulations to investigate the emergent chiral properties (including symmetry breaking) over a range of conditions. In particular, we consider the single-molecule level and condensed-phase behavior of our model system. Interestingly, we find that our liquid-phase predictions are in excellent agreement with recent experimental reports on chiral self-sorting in isotropic liquids. From this perspective, our model demonstrates accurate predictive capabilities, as well as a platform for understanding the microscopic origins of a variety of chiral phenomena. In a broader context, we anticipate that this class of models will be relevant to chirality-dominated areas such as the pharmaceutical industry and pre-biotic geochemistry.
Flavor asymmetry of sea quarks in the unquenched quark model
Santopinto, E.; Bijker, R.
2010-12-15
The flavor asymmetry of the nucleon sea is studied in the framework of the unquenched quark model in which the effects of quark-antiquark pairs (uu-bar, dd-bar, and ss-bar) are taken into account via a microscopic, QCD-inspired, quark-antiquark creation mechanism. The inclusion of the qq-bar pairs leads to an excess of d-bar over u-bar, in agreement with the experimental data for the proton. In addition, the results for the flavor asymmetry of all ground-state octet and decuplet baryons are presented. The isospin symmetry leads to simple relations among the flavor asymmetries of octet and decuplet baryons. The flavor asymmetry of the {Sigma}{sup +} hyperon is predicted to be very similar to that of the proton and much larger than that for the {Xi}{sup 0} hyperon. A comparison with other approaches shows large differences in the predictions for the flavor asymmetries of the hyperons.
Quantization of the chiral soliton in medium
NASA Astrophysics Data System (ADS)
Nagai, S.; Sawado, N.; Shiiki, N.
2006-01-01
Chiral solitons coupled with quarks in medium are studied based on the Wigner-Seitz approximation. The chiral quark soliton model is used to obtain the classical soliton solutions. To investigate nucleon and Δ in matter, the semi-classical quantization is performed by the cranking method. The saturation for nucleon matter and Δ matter are observed.
Chiral susceptibility in an effective interaction model
Min He; Yu Jiang; Sun Weimin; Zong Hongshi
2008-04-01
A closed integral expression for the chiral susceptibility at finite temperature is derived. The corresponding disconnected part, which proves to be of major physical relevance and free from the additive quadratic ultraviolet divergence, is identified. Then a calculation based on an effective model gluon propagator is conducted within the framework of the Dyson-Schwinger equations for two flavors in the chiral limit. A narrow, divergent peak is observed as temperature varies, and its implications are discussed.
The phase diagram in the SU(3) Nambu-Jona-Lasinio model with 't Hooft and eight-quark interactions
Moreira, J.; Hiller, B.; Blin, A. H.; Osipov, A. A.
2010-08-05
It is shown that the endpoint of the first order transition line which merges into a crossover regime in the phase diagram of the Nambu--Jona-Lasinio model, extended to include the six-quark 't Hooft and eight-quark interaction Lagrangians, is pushed towards vanishing chemical potential and higher temperatures with increasing strength of the OZI-violating eight-quark interactions. We clarify a connection between the location of the endpoint in the phase diagram and the mechanism of chiral symmetry breaking at the quark level. Constraints on the coupling strengths based on groundstate stability and physical considerations are explained.
Strangeness suppression in the unquenched quark model
NASA Astrophysics Data System (ADS)
Bijker, Roelof; García-Tecocoatzi, Hugo; Santopinto, Elena
2016-07-01
In this contribution, we discuss the strangeness suppression in the proton in the framework of the unquenched quark model. The theoretical results are in good agreement with the values extracted from CERN and JLab experiments.
From quarks and gluons to hadrons: Chiral symmetry breaking in dynamical QCD
NASA Astrophysics Data System (ADS)
Braun, Jens; Fister, Leonard; Pawlowski, Jan M.; Rennecke, Fabian
2016-08-01
We present an analysis of the dynamics of two-flavor QCD in the vacuum. Special attention is paid to the transition from the high-energy quark-gluon regime to the low-energy regime governed by hadron dynamics. This is done within a functional renormalization group approach to QCD amended by dynamical hadronization techniques. These techniques allow us to describe conveniently the transition from the perturbative high-energy regime to the nonperturbative low-energy limit without suffering from a fine-tuning of model parameters. In the present work, we apply these techniques to two-flavor QCD with physical quark masses and show how the dynamics of the dominant low-energy degrees of freedom emerge from the underlying quark-gluon dynamics.
Hadron loops in the quark model
Bijker, Roelof; Santopinto, Elena
2010-08-04
We present an unquenched quark model for baryons in which the effects of quark-antiquark pair creation (uu(bar sign), dd(bar sign) and ss(bar sign)) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. It is shown that, while the inclusion of the qq(bar sign) pairs does not affect the baryon magnetic moments, it leads to a sizeable contribution of the orbital angular momentum to the spin of the proton.
An Unquenched Quark Model of Baryons
Bijker, Roelof; Santopinto, Elena
2007-10-26
We present the formalism for a new generation of unquenched quark models for baryons in which the effects of quark-antiquark pairs are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. The present approach is an extension of the fiux-tube breaking model of Geiger and Isgur in which now the contribution of quark-antiquark pairs can be studied for any inital baryon, for any fiavor of the qq-bar pair (not only ss-bar but also uu-bar and dd-bar) and for arbitrary hadron wave functions. The method is illustrated with an application to the spin of the proton and the flavor asymmetry of the nucleon sea.
Valence QCD: Connecting QCD to the quark model
Liu, K.F.; Dong, S.J.; Draper, T.; Sloan, J.; Leinweber, D.; Wilcox, W.; Woloshyn, R.M.
1999-06-01
disappearance of the {open_quotes}constituent{close_quotes} quark mass which is dynamically generated through tadpole diagrams. The origin of the hyperfine splitting in the baryon is largely attributed to the Goldstone boson exchanges between the quarks. Both of these are the consequences of the lack of chiral symmetry in valence QCD. We discuss its implications concerning the models of hadrons. {copyright} {ital 1999} {ital The American Physical Society}
Search for doubly-heavy dibaryons in a quark model
NASA Astrophysics Data System (ADS)
Vijande, J.; Valcarce, A.; Richard, J.-M.; Sorba, P.
2016-08-01
We study the stability of hexaquark systems containing two heavy quarks and four light quarks within a simple quark model. No bound or metastable state is found. The reason stems from a delicate interplay between chromoelectric and chromomagnetic effects. Our calculation also provides information about anticharmed pentaquarks that are seemingly unbound in simple quark models.
NASA Astrophysics Data System (ADS)
Kahana, David E.; Jackson, A. D.; Ripka, G.
1986-11-01
Cranking of the chiral bag model is carried out in order to generate the correct quantum numbers for SU(2) baryons. The moment of inertia of the system is found to be divided between the meson and quark sectors. A numerical evaluation of the contributions to the moment of inertia from valence quarks and from mesons is presented. Finally, a discussion is given of the nucleon-delta mass splitting predicted in the chiral bag model.
Heavy Baryons in a Quark Model
Winston Roberts; Muslema Pervin
2007-11-14
A quark model is applied to the spectrum of baryons containing heavy quarks. The model gives masses for the known heavy baryons that are in agreement with experiment, but for the doubly-charmed baryon $\\Xi_{cc}$, the model prediction is too heavy. Mixing between the $\\Xi_Q$ and $\\Xi_Q^\\prime$ states is examined and is found to be small for the lowest lying states. In contrast with this, mixing between the $\\Xi_{bc}$ and $\\Xi_{bc}^\\prime$ states is found to be large, and the implication of this mixing for properties of these states is briefly discussed. We also examine heavy-quark spin-symmetry multiplets, and find that many states in the model can be placed in such multiplets.
Four-modulus ``Swiss Cheese'' chiral models
NASA Astrophysics Data System (ADS)
Collinucci, Andrés; Kreuzer, Maximilian; Mayrhofer, Christoph; Walliser, Nils-Ole
2009-07-01
We study the `Large Volume Scenario' on explicit, new, compact, four-modulus Calabi-Yau manifolds. We pay special attention to the chirality problem pointed out by Blumenhagen, Moster and Plauschinn. Namely, we thoroughly analyze the possibility of generating neutral, non-perturbative superpotentials from Euclidean D3-branes in the presence of chirally intersecting D7-branes. We find that taking proper account of the Freed-Witten anomaly on non-spin cycles and of the Kähler cone conditions imposes severe constraints on the models. Nevertheless, we are able to create setups where the constraints are solved, and up to three moduli are stabilized.
Isospin Mixing of Quark Cluster Diybaryon Resonances in the Bag Model*
NASA Astrophysics Data System (ADS)
Ward, Thomas
2000-10-01
Calculations of isospin mixing of dibaryon resonaces composed of color magentic six quark states using the quark cluster bag model are shown to result in a low lying J=2 dibaryon at 1913 MeV. The 1913 MeV resonance can only transition into NN states and a low energy (29-35 MeV) isoscaler meson multiplet, the sigma mesons (J=0,1,2). The J=1 axial-vector meson may already have been discovered at the Rutherford ISIS Facility, detected as a neutrino time anomaly known as the KARMEN particle. The predicted J=0 meson has the long sought after properties of the sigma meson or Higgs particle required for the Chiral Symmetry Breaking partner of the pion and light mass hadron generation. The influence of this predicted isoscaler multiplet in QCD and QFD is interpreted using the effective low energy model of Chiral Perturbation Theory.
Relativistic constituent quark model with infrared confinement
Branz, Tanja; Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E.; Ivanov, Mikhail A.; Koerner, Juergen G.
2010-02-01
We refine the relativistic constituent quark model developed in our previous papers to include the confinement of quarks. It is done, first, by introducing the scale integration in the space of {alpha} parameters, and, second, by cutting this scale integration on the upper limit which corresponds to an infrared cutoff. In this manner one removes all possible thresholds present in the initial quark diagram. The cutoff parameter is taken to be the same for all physical processes. We adjust other model parameters by fitting the calculated quantities of the basic physical processes to available experimental data. As an application, we calculate the electromagnetic form factors of the pion and the transition form factors of the {omega} and {eta} Dalitz decays.
The Constituent Quark Model: a Status Report
Eric S. Swanson
2002-06-07
A brief and biased overview of the status of the constituent quark model is presented. We concentrate on open issues and goals of hadronic phenomenology, rather than specific physics conundrums in the field. Modern attempts at addressing these issues are also presented.
NASA Astrophysics Data System (ADS)
Schleif, M.; Wünsch, R.; Maissner, T.
We study translational and spin-isospin symmetry restoration for the two-flavor chiral quark-loop soliton. Instead of a static soliton at rest we consider a boosted and rotating hedgehog soliton. Corrected classical meson fields are obtained by minimizing a corrected energy functional which has been derived by semi-classical methods (variation after projection). We evaluate corrected meson fields in the region 300 MeV ≤ M≤ 600 MeV of constituent quark masses M and compare them with the uncorrected fields. We study the effect of the corrections on various expectation values of nuclear observables such as the root-mean square radius, the axial-vector coupling constant, magnetic moments and the delta-nucleon mass splitting.
Properties of Doubly Heavy Baryons in the Relativistic Quark Model
Ebert, D.; Faustov, R.N.; Galkin, V.O.; Martynenko, A.P.
2005-05-01
Mass spectra and semileptonic decay rates of baryons consisting of two heavy (b or c) and one light quark are calculated in the framework of the relativistic quark model. The doubly heavy baryons are treated in the quark-diquark approximation. The ground and excited states of both the diquark and quark-diquark bound systems are considered. The quark-diquark potential is constructed. The light quark is treated completely relativistically, while the expansion in the inverse heavy-quark mass is used. The weak transition amplitudes of heavy diquarks bb and bc going, respectively, to bc and cc are explicitly expressed through the overlap integrals of the diquark wave functions in the whole accessible kinematic range. The relativistic baryon wave functions of the quark-diquark bound system are used for the calculation of the decay matrix elements, the Isgur-Wise function, and decay rates in the heavy-quark limit.
Chirally symmetric O(1/N{sub c}) corrections to the Nambu-Jona-Lasinio model
Dmitrasinovic, V.; Schulze, H.J.; Tegen, R.
1995-03-01
We develop an extended chirally symmetric self-consistent approximation scheme to the Nambu-Jona-Lasinio model, that corresponds to O(1/N{sub c}) corrections to the usual Hartree + random phase approximations. This scheme amounts to adding {open_quotes}meson cloud{close_quotes} contributions self-consistently to the quark self-energy and the meson polarization functions in a manner suggested by the weakly interacting nature of the quark and collective meson degrees of freedom of the NJL model in the large N{sub c} limit. We demonstrate explicitly that this scheme fulfills all the chiral symmetry theorems, namely the Goldstone theorem, the Goldberger-Treiman relation, and the conservation of the quark axial current. We explore the corrections to the quark self-energy and scalar condensate, as well as to the pion polarization function and the weak decay constant N{sub n}. The numerical evaluation of these corrections is presented and discussed. 23 refs., 14 figs., 2 tabs.
Anomalous transport model study of chiral magnetic effects in heavy ion collisions
NASA Astrophysics Data System (ADS)
Sun, Yifeng; Ko, Che Ming; Li, Feng
2016-10-01
Using an anomalous transport model for massless quarks and antiquarks, we study the effect of a magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in noncentral heavy ion collisions can last for a sufficiently long time, we obtain an appreciable electric quadrupole moment in the transverse plane of a heavy ion collision. The electric quadrupole moment subsequently leads to a splitting between the elliptic flows of quarks and antiquarks. The slope of the charge asymmetry dependence of the elliptic flow difference between positively and negatively charged particles is positive, which is expected from the chiral magnetic wave formed in the produced QGP and observed in experiments at the BNL Relativistic Heavy Ion Collider, only if the Lorentz force acting on the charged particles is neglected and the quark-antiquark scattering is assumed to be dominated by the chirality changing channel.
Exotic quarks in Twin Higgs models
Cheng, Hsin -Chia; Jung, Sunghoon; Salvioni, Ennio; Tsai, Yuhsin
2016-03-14
The Twin Higgs model provides a natural theory for the electroweak symmetry breaking without the need of new particles carrying the standard model gauge charges below a few TeV. In the low energy theory, the only probe comes from the mixing of the Higgs fields in the standard model and twin sectors. However, an ultraviolet completion is required below ~ 10 TeV to remove residual logarithmic divergences. In non-supersymmetric completions, new exotic fermions charged under both the standard model and twin gauge symmetries have to be present to accompany the top quark, thus providing a high energy probe of themore » model. Some of them carry standard model color, and may therefore be copiously produced at current or future hadron colliders. Once produced, these exotic quarks can decay into a top together with twin sector particles. If the twin sector particles escape the detection, we have the irreducible stop-like signals. On the other hand, some twin sector particles may decay back into the standard model particles with long lifetimes, giving spectacular displaced vertex signals in combination with the prompt top quarks. This happens in the Fraternal Twin Higgs scenario with typical parameters, and sometimes is even necessary for cosmological reasons. We study the potential displaced vertex signals from the decays of the twin bottomonia, twin glueballs, and twin leptons in the Fraternal Twin Higgs scenario. As a result, depending on the details of the twin sector, the exotic quarks may be probed up to ~ 2.5 TeV at the LHC and beyond 10 TeV at a future 100 TeV collider, providing a strong test of this class of ultraviolet completions.« less
A composite model of quarks and bosons
NASA Astrophysics Data System (ADS)
Moffat, J. W.
2015-01-01
A composite model of quarks and bosons is proposed in which a spin 1/2 isospin doublet ψ is the basic building block of quarks and bosons in the standard model. The ψ has two components v and w with charges Q = (1)/(3)e and Q = 0, respectively, that combine to form the three generations of colored quark flavors. A strong force described by a triplet of massless gluons binds the constituents called geminis. The confining constituent non-Abelian SU(2)C field theory is called constituent dynamics with a confining energy scale ΛCD. The constituent dynamics condensate <\\bar {v}v+\\bar {w}w>!=q 0 spontaneously breaks the electroweak symmetry SU(2)L×U(1)Y→U(1)EM and a triplet of Nambu-Goldstone bosons make the gauge bosons W± and Z0 massive, while retaining a massless photon. A global custodial SU(2)L×SU(2)R symmetry guarantees that the symmetry breaking in the weak interaction sector agrees with electroweak data. The non-Abelian SU(2)C color dynamics satisfies asymptotic freedom, which resolves the gauge and Higgs mass hierarchy problems and makes the model ultraviolet complete. The composite constituent dynamics model can realize a SU(3)C×SU(2)L×U(1)Y electroweak and strong interaction model that satisfies the naturalness principle. The three generations of colorless quarks α and β with charges Q = +1e and Q = 0, respectively, which are predicted to exist in the composite model can form bound states which can be identified with the spectrum of exotic mesons.
Personal recollections on chiral symmetry breaking
NASA Astrophysics Data System (ADS)
Kobayashi, Makoto
2016-07-01
The author's work on the mass of pseudoscalar mesons is briefly reviewed. The emergence of the study of CP violation in the renormalizable gauge theory from consideration of chiral symmetry in the quark model is discussed.
Rare top quark decays in extended models
Gaitan, R.; Miranda, O. G.; Cabral-Rosetti, L. G.
2006-09-25
Flavor changing neutral currents (FCNC) decays t {yields} H0 + c, t {yields} Z + c, and H0 {yields} t + c-bar are discussed in the context of Alternative Left-Right symmetric Models (ALRM) with extra isosinglet heavy fermions where FCNC decays may take place at tree-level and are only suppressed by the mixing between ordinary top and charm quarks, which is poorly constraint by current experimental values. The non-manifest case is also briefly discussed.
Model for quark and lepton constituents
NASA Astrophysics Data System (ADS)
Fairlie, D.; Nuyts, J.; Taormina, A.
1983-01-01
A model of subconstituents for quarks and leptons is presented in which each of three different types transforms under a different group which is gauged. The binding is taken as magnetic, the dual of the usual electric charge, and hence very strong. The spin of the constituents is zero. The spin of the bound states arises dynamically. Weak interactions violate parity maximally and the Weinberg angle, related to the generation problem, comes out well numerically. Two exotic states are predicted.
Chiral symmetry and pentaquarks
Dmitri Diakonov
2004-07-01
Spontaneous chiral symmetry breaking, mesons and baryons are illustrated in the language of the Dirac theory. Various forces acting between quarks inside baryons are discussed. I explain why the naive quark models typically overestimate pentaquark masses by some 500 MeV and why in the fully relativistic approach to baryons pentaquarks turn out to be light. I discuss briefly why it can be easier to produce pentaquarks at low than at high energies.
Quark nova model for fast radio bursts
NASA Astrophysics Data System (ADS)
Shand, Zachary; Ouyed, Amir; Koning, Nico; Ouyed, Rachid
2016-05-01
Fast radio bursts (FRBs) are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via β-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm‑3 pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of β-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies (˜ 1041 erg) and spectral shapes, and provide a theoretical framework for determining distances.
Quark nova model for fast radio bursts
NASA Astrophysics Data System (ADS)
Shand, Zachary; Ouyed, Amir; Koning, Nico; Ouyed, Rachid
2016-05-01
Fast radio bursts (FRBs) are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via β-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm‑3 pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of β-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies (∼ 1041 erg) and spectral shapes, and provide a theoretical framework for determining distances.
Two chiral preon models with SU(N) metacolor satisfying complementarity
NASA Astrophysics Data System (ADS)
Geng, C. Q.; Marshak, R. E.
1987-04-01
We have constructed two chiral preon models based on the group SU(N)MC×SU(N+4)F×U(1)F (MC is gauged metacolor and F is global color flavor), the simplest (M=0) version of a class of models SU(N)MC×SU(N+M+4)F×SU(M)F×U(1)F 2 studied by bars and Yankielowicz. In contrast with earlier work, our models satisfy the principle of complementarity between the Higgs and confining phases. In one model, N=16 and four generations of ordinary quarks and leptons are found at the gauged SO(10) level. The second model predicts three quark-lepton families at the gauged SU(5) level without a right-handed neutrino. We also show that complementarity holds for the M≠0 models but that, for N=15 or 16, the results at the gauged level are identical with the M=0 case.
Hybrid neutron stars with the Dyson-Schwinger quark model and various quark-gluon vertices
NASA Astrophysics Data System (ADS)
Chen, H.; Wei, J.-B.; Baldo, M.; Burgio, G. F.; Schulze, H.-J.
2015-05-01
We study cold dense quark matter and hybrid neutron stars with a Dyson-Schwinger quark model and various choices of the quark-gluon vertex. We obtain the equation of state of quark matter in beta equilibrium and investigate the hadron-quark phase transition in combination with a hadronic equation of state derived within the Brueckner-Hartree-Fock many-body theory. Comparing with the results for quark matter within the rainbow approximation, the Ball-Chiu (BC) Ansatz and the 1BC Ansatz for the quark-gluon vertex lead to a reduction of the effective interaction at finite chemical potential, qualitatively similar to the effect of our gluon propagator. We find that the phase transition and the equation of state of the quark or mixed phase and consequently the resulting hybrid star mass and radius depend mainly on a global reduction of the effective interaction due to effects of both the quark-gluon vertex and gluon propagator, but are not sensitive to details of the vertex Ansatz.
Isospin properties of quark matter from a 3-flavor NJL model
NASA Astrophysics Data System (ADS)
Liu, He; Xu, Jun; Chen, Lie-Wen; Sun, Kai-Jia
2016-09-01
We have studied the properties of hot and dense quark matter based on the 3-flavor Nambu-Jona-Lasinio (NJL) model as well as its Polyakov-loop extension (pNJL) with scalar-isovector and vector-isovector couplings. Provided a considerable large isospin asymmetry or isospin chemical potential, isospin splittings of constituent mass, chiral phase transition boundary, and critical point for u and d quarks can be observed for positive isovector coupling constants but are suppressed for negative ones. The quark matter symmetry energy decreases with the increasing isovector coupling constant, and is mostly enhanced in the pNJL model than in the NJL model. A positive scalar-isovector coupling constant is more likely to lead to an unstable isospin asymmetric quark matter. The isovector coupling has been further found to affect particle fractions as well as the equation of state in hybrid stars. Possible effects on the isospin properties of quark matter have also been discussed if the strangeness sector is further broken among the flavor symmetry.
Quark-Gluon Plasma Model and Origin of Magic Numbers
Ghahramany, N.; Ghanaatian, M.; Hooshmand, M.
2008-04-21
Using Boltzman distribution in a quark-gluon plasma sample it is possible to obtain all existing magic numbers and their extensions without applying the spin and spin-orbit couplings. In this model it is assumed that in a quark-gluon thermodynamic plasma, quarks have no interactions and they are trying to form nucleons. Considering a lattice for a central quark and the surrounding quarks, using a statistical approach to find the maximum number of microstates, the origin of magic numbers is explained and a new magic number is obtained.
A supersymmetric composite model of quarks and leptons
NASA Astrophysics Data System (ADS)
Luty, Markus A.; Mohapatra, Rabindra N.
1997-02-01
We present a class of supersymmetric models with complete generations of composite quarks and leptons using recent non-perturbative results for the low energy dynamics of supersymmetric QCD. In these models, the quarks arise as composite ``mesons'' and the leptons emerge as composite ``baryons''. The quark and lepton flavor symmetries are linked at the preon level. Baryon number violation is automatically suppressed by accidental symmetries. We give some speculations on how this model might be made realistic.
Quark matter as dark matter in modeling galactic halo
NASA Astrophysics Data System (ADS)
Rahaman, Farook; Kuhfittig, P. K. F.; Amin, Ruhul; Mandal, Gurudas; Ray, Saibal; Islam, Nasarul
2012-08-01
Considering the flat rotation curves as input and treating the matter content in the galactic halo region as quark matter, we have found out a background spacetime metric for the region of the galactic halo. We obtain fairly general conditions that ensure that gravity in the halo region is attractive. We also investigate the stability of circular orbits, along with a different role for quark matter. Bag-model quark matter meeting these conditions therefore provides a suitable model for dark matter.
NASA Astrophysics Data System (ADS)
Dunne, Gerald V.
2006-05-01
This talk reports work done in collaboration with Jin Hur, Choonkyu Lee and Hyunsoo Min concerning the computation of the precise mass dependence of the fermion determinant for quarks in the presence of an instanton background. The result interpolates smoothly between the previously known chiral and heavy quark limits of extreme small and large mass. The computational method makes use of the fact that the single instanton background has radial symmetry, so that the computation can be reduced to a sum over partial waves of logarithms of radial determinants, each of which can be computed numerically in an efficient manner using a theorem of Gelfand and Yaglom. The bare sum over partial waves is divergent and must be regulated and renormalized. We use the angular momentum cutoff regularization and renormalization scheme. Our results provide an extension of the Gelfand-Yaglom result to higher-dimensional separable differential operators. I also comment on the application of this approach to a wide variety of fluctuation determinant computations in quantum field theory.
Quark-jet model for transverse momentum dependent fragmentation functions
NASA Astrophysics Data System (ADS)
Bentz, W.; Kotzinian, A.; Matevosyan, H. H.; Ninomiya, Y.; Thomas, A. W.; Yazaki, K.
2016-08-01
In order to describe the hadronization of polarized quarks, we discuss an extension of the quark-jet model to transverse momentum dependent fragmentation functions. The description is based on a product ansatz, where each factor in the product represents one of the transverse momentum dependent splitting functions, which can be calculated by using effective quark theories. The resulting integral equations and sum rules are discussed in detail for the case of inclusive pion production. In particular, we demonstrate that the three-dimensional momentum sum rules are satisfied naturally in this transverse momentum dependent quark-jet model. Our results are well suited for numerical calculations in effective quark theories and can be implemented in Monte Carlo simulations of polarized quark hadronization processes.
Top Quark Properties in Little Higgs Models
Berger, C.F.; Perelstein, M.; Petriello, F.; /Wisconsin U., Madison
2005-12-08
Identifying the mechanism which breaks electroweak symmetry and generates fermion masses is one of the main physics goals for both the LHC and the ILC. Studies of the top quark have the potential to illuminate this issue; since it is the heaviest of the Standard Model (SM) fermions, the top is expected to couple strongly to the symmetry-breaking sector. Consequently, the structure of that sector can have significant, potentially observable effects on the properties of the top. for example, it is well known that the vector and axial t{bar t}Z form factors receive large corrections (of order 5-10%) in certain models of dynamical electroweak symmetry breaking [1]. At future colliders such as the LHC and the ILC, we will be able to pursue a program of precision top physics, similar to the program studying the Z at LEP and SLC. In this manuscript, they study the corrections to the top quark properties in ''Little Higgs'' models of electroweak symmetry breaking [2], and compare the expected deviations from the SM predictions with expected sensitivities of experiments at the LHC and the ILC. In the Little Higgs models, electroweak symmetry is driven by the radiative effects from the top sector, including the SM-like top and its heavy counterpart, a TeV-scale ''heavy top'' T. Probing this structure experimentally is quite difficult. While the LHC should be able to discover the T quark, its potential for studying its couplings is limited [3,4]. Direct production of the T will likely be beyond the kinematic reach of the ILC. However, we will show below that the corrections to the gauge couplings of the SM top, induced by its mixing with the T, will be observable at the ILC throughout the parameter range consistent with naturalness. Measuring these corrections will provide a unique window on the top sector of the Little Higgs. Many Little Higgs models have been proposed in the literature. We will consider two examples in this study, the ''Littlest Higgs'' model [5], and its
Transverse momentum correlations of quarks in recursive jet models
NASA Astrophysics Data System (ADS)
Artru, X.; Belghobsi, Z.; Redouane-Salah, E.
2016-08-01
In the symmetric string fragmentation recipe adopted by PYTHIA for jet simulations, the transverse momenta of successive quarks are uncorrelated. This is a simplification but has no theoretical basis. Transverse momentum correlations are naturally expected, for instance, in a covariant multiperipheral model of quark hadronization. We propose a simple recipe of string fragmentation which leads to such correlations. The definition of the jet axis and its relation with the primordial transverse momentum of the quark is also discussed.
Flavor content of the nucleon in an unquenched quark model
Bijker, R.; Santopinto, E.
2009-04-20
We discuss the flavor content of the nucleon in an unquenched quark model in which the effects of quark-antiquark pairs (uu-bar, dd-bar and ss-bar) are taken into account in an explicit form. It is shown that the inclusion of qq-bar pairs leads to an excess of d-bar over u-bar quarks in the proton and to a large contribution of orbital angular momentum to the spin of the proton.
Phase diagram of chirally imbalanced QCD matter
Chernodub, M. N.; Nedelin, A. S.
2011-05-15
We compute the QCD phase diagram in the plane of the chiral chemical potential and temperature using the linear sigma model coupled to quarks and to the Polyakov loop. The chiral chemical potential accounts for effects of imbalanced chirality due to QCD sphaleron transitions which may emerge in heavy-ion collisions. We found three effects caused by the chiral chemical potential: the imbalanced chirality (i) tightens the link between deconfinement and chiral phase transitions; (ii) lowers the common critical temperature; (iii) strengthens the order of the phase transition by converting the crossover into the strong first order phase transition passing via the second order end point. Since the fermionic determinant with the chiral chemical potential has no sign problem, the chirally imbalanced QCD matter can be studied in numerical lattice simulations.
Dibaryons with two strange quarks and one heavy flavor in a constituent quark model
NASA Astrophysics Data System (ADS)
Park, Aaron; Park, Woosung; Lee, Su Houng
2016-09-01
We investigate the symmetry property and the stability of dibaryons containing two strange quarks and one heavy flavor with isospin I =1/2 . We construct the wave function of the dibaryon in two ways. First, we directly construct the color and spin state of the dibaryon starting from the four possible S U (3 ) flavor states. Second, we consider the states composed of five light quarks and then construct the wave function of the dibaryon by adding one heavy quark. The stability of the dibaryon against the strong decay into two baryons is discussed by using the variational method in a constituent quark model with a confining and hyperfine potential. We find that, for all configurations with spin S =0 , 1, 2, the ground states of the dibaryons are the sum of two baryons, and there is no compact bound state that is stable against the strong decay.
Sinclair, D. K.
2008-09-01
Suggested holographic duals of QCD, based on AdS/CFT duality, predict that one should be able to vary the scales of color confinement and chiral-symmetry breaking independently. Furthermore they suggest that such independent variation of scales can be achieved by the inclusion of extra 4-fermion interactions in QCD. We simulate lattice QCD with such extra 4-fermion terms at finite temperatures and show that for strong enough 4-fermion couplings the deconfinement transition occurs at a lower temperature than the chiral-symmetry restoration transition. Moreover the separation of these transitions depends on the size of the 4-fermion coupling, confirming the predictions from the proposed holographic dual of QCD. We use simpler 4-fermion interactions than those suggested by these dual theories to facilitate our simulations. This is because we believe that the physics we wish to study should be insensitive to the precise form of these interactions.
Sinclair, D. K.; High Energy Physics
2008-01-01
Suggested holographic duals of QCD, based on AdS/CFT duality, predict that one should be able to vary the scales of color confinement and chiral-symmetry breaking independently. Furthermore they suggest that such independent variation of scales can be achieved by the inclusion of extra 4-fermion interactions in QCD. We simulate lattice QCD with such extra 4-fermion terms at finite temperatures and show that for strong enough 4-fermion couplings the deconfinement transition occurs at a lower temperature than the chiral-symmetry restoration transition. Moreover the separation of these transitions depends on the size of the 4-fermion coupling, confirming the predictions from the proposed holographic dual of QCD. We use simpler 4-fermion interactions than those suggested by these dual theories to facilitate our simulations. This is because we believe that the physics we wish to study should be insensitive to the precise form of these interactions.
The Thomas–Fermi quark model: Non-relativistic aspects
Liu, Quan Wilcox, Walter
2014-02-15
The first numerical investigation of non-relativistic aspects of the Thomas–Fermi (TF) statistical multi-quark model is given. We begin with a review of the traditional TF model without an explicit spin interaction and find that the spin splittings are too small in this approach. An explicit spin interaction is then introduced which entails the definition of a generalized spin “flavor”. We investigate baryonic states in this approach which can be described with two inequivalent wave functions; such states can however apply to multiple degenerate flavors. We find that the model requires a spatial separation of quark flavors, even if completely degenerate. Although the TF model is designed to investigate the possibility of many-quark states, we find surprisingly that it may be used to fit the low energy spectrum of almost all ground state octet and decuplet baryons. The charge radii of such states are determined and compared with lattice calculations and other models. The low energy fit obtained allows us to extrapolate to the six-quark doubly strange H-dibaryon state, flavor symmetric strange states of higher quark content and possible six quark nucleon–nucleon resonances. The emphasis here is on the systematics revealed in this approach. We view our model as a versatile and convenient tool for quickly assessing the characteristics of new, possibly bound, particle states of higher quark number content. -- Highlights: • First application of the statistical Thomas–Fermi quark model to baryonic systems. • Novel aspects: spin as generalized flavor; spatial separation of quark flavor phases. • The model is statistical, but the low energy baryonic spectrum is successfully fit. • Numerical applications include the H-dibaryon, strange states and nucleon resonances. • The statistical point of view does not encourage the idea of bound many-quark baryons.
Relativistic quark model for the Omega- electromagnetic form factors
G. Ramalho, K. Tsushima, Franz Gross
2009-08-01
We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.
Cranking the Chiral Soliton Bag Model:. Gluonic Effects
NASA Astrophysics Data System (ADS)
Stern, Jacqueline; Bourenane, Mohamed; Clément, Gérard
The nucleon-delta mass difference is computed in the chiral soliton bag model with soft confinement of gluons by the cranking method. The resulting value of the effective strong fine structure constant is αs≃0.7.
Ogino, Yoshiyuki; Asahi, Toru
2015-05-21
In this study, systems of complicated pathways involved in chiral drug metabolism were investigated. The development of chiral drugs resulted in significant improvement in the remedies available for the treatment of various severe sicknesses. Enantiopure drugs undergo various biological transformations that involve chiral inversion and thus result in the generation of multiple enantiomeric metabolites. Identification of the specific active substances determining a given drug׳s efficacy among such a mixture of different metabolites remains a challenge. To comprehend this complexity, we constructed a mathematical model representing the complicated metabolic pathways simultaneously involving chiral inversion. Moreover, this model is applied to the metabolism of thalidomide, which has recently been revived as a potentially effective prescription drug for a number of intractable diseases. The numerical simulation results indicate that retained chirality in the metabolites reflects the original chirality of the unmetabolized drug, and a higher level of enantiomeric purity is preserved during spontaneous degradation. In addition, chirality remaining after equilibration is directly related to the rate constant not only for chiral inversion but also for generation and degradation. Furthermore, the retention of chirality is quantitatively predictable using this combination of kinetic parameters. Our simulation results well explain the behavior of thalidomide in the practical biological experimental data. Therefore, this model promises a comprehensive understanding of dynamic metabolic systems involving chiral drugs that express multiple enantiospecific drug efficacies.
Ogino, Yoshiyuki; Asahi, Toru
2015-05-21
In this study, systems of complicated pathways involved in chiral drug metabolism were investigated. The development of chiral drugs resulted in significant improvement in the remedies available for the treatment of various severe sicknesses. Enantiopure drugs undergo various biological transformations that involve chiral inversion and thus result in the generation of multiple enantiomeric metabolites. Identification of the specific active substances determining a given drug׳s efficacy among such a mixture of different metabolites remains a challenge. To comprehend this complexity, we constructed a mathematical model representing the complicated metabolic pathways simultaneously involving chiral inversion. Moreover, this model is applied to the metabolism of thalidomide, which has recently been revived as a potentially effective prescription drug for a number of intractable diseases. The numerical simulation results indicate that retained chirality in the metabolites reflects the original chirality of the unmetabolized drug, and a higher level of enantiomeric purity is preserved during spontaneous degradation. In addition, chirality remaining after equilibration is directly related to the rate constant not only for chiral inversion but also for generation and degradation. Furthermore, the retention of chirality is quantitatively predictable using this combination of kinetic parameters. Our simulation results well explain the behavior of thalidomide in the practical biological experimental data. Therefore, this model promises a comprehensive understanding of dynamic metabolic systems involving chiral drugs that express multiple enantiospecific drug efficacies. PMID:25791284
Extending NEC to model wire objects in infinite chiral media
Burke, G.J.; Miller, E.K.; Bhattachryya, A.K.
1992-03-01
The development of a moment-method model for wire objects in an infinite chiral medium is described. In this work, the Numerical Electromagnetics Code (NEC) was extended by including a new integral-equation kernel obtained from the dyadic Green`s function for an infinite chiral medium. The NEC moment-method treatment using point matching and a three-term sinusoidal current expansion was adapted to the case of a chiral medium. Examples of current distributions and radiation patterns for simple antennas are presented, and the validation of the code is discussed. 15 refs.
Relativistic quark-diquark model of baryons
Ferretti, J.; Vassallo, A.; Santopinto, E.
2011-06-15
A relativistic quark-diquark mass operator with direct and exchange interaction has been constructed in the framework of point form dynamics. The nonstrange baryon spectrum has been calculated and compared with experimental data.
Flavor signatures of isosinglet vector-like down quark model
NASA Astrophysics Data System (ADS)
Alok, Ashutosh Kumar; Banerjee, Subhashish; Kumar, Dinesh; Uma Sankar, S.
2016-05-01
We consider a model where the standard model is extended by the addition of a vector-like isosinglet down-type quark b‧. We perform a χ2 fit to the flavor physics data and obtain the preferred central values along with errors of all the elements of the measurable 3 × 4 quark mixing matrix. The fit indicates that all the new-physics parameters are consistent with zero and the mixing of the b‧ quark with the other three is constrained to be small. The current flavor physics data rules out possibility of detectable new physics signals in most of the flavor physics observables. We also investigate possible deviations in the standard model Wtb couplings and bottom quark coupling to Higgs boson. We find that these deviations are less than a percent level which is too small to be observed at the LHC with current precision.
Cristoforetti, M.; Hell, T.; Klein, B.; Weise, W.
2010-06-01
The Monte-Carlo method is applied to the Polyakov-loop extended Nambu-Jona-Lasinio model. This leads beyond the saddle-point approximation in a mean-field calculation and introduces fluctuations around the mean fields. We study the impact of fluctuations on the thermodynamics of the model, both in the case of pure gauge theory and including two quark flavors. In the two-flavor case, we calculate the second-order Taylor expansion coefficients of the thermodynamic grand canonical partition function with respect to the quark chemical potential and present a comparison with extrapolations from lattice QCD. We show that the introduction of fluctuations produces only small changes in the behavior of the order parameters for chiral symmetry restoration and the deconfinement transition. On the other hand, we find that fluctuations are necessary in order to reproduce lattice data for the flavor nondiagonal quark susceptibilities. Of particular importance are pion fields, the contribution of which is strictly zero in the saddle point approximation.
Violation of quark-hadron duality and spectral chiral moments in QCD
Gonzalez-Alonso, Martin; Pich, Antonio; Prades, Joaquim
2010-04-01
We analyze the spectral moments of the V-A two-point correlation function. Using all known short-distance constraints and the most recent experimental data from tau decays, we determine the lowest spectral moments, trying to assess the uncertainties associated with the so-called violations of quark-hadron duality. We have generated a large number of acceptable spectral functions, satisfying all conditions, and have used them to extract the wanted hadronic parameters through a careful statistical analysis. We obtain accurate values for the {chi}PT couplings L{sub 10} and C{sub 87}, and a realistic determination of the dimension six and eight contributions in the operator product expansion, O{sub 6}=(-5.4{sub -1.6}{sup +3.6}){center_dot}10{sup -3} GeV{sup 6} and O{sub 8}=(-8.9{sub -7.4}{sup +12.6}){center_dot}10{sup -3} GeV{sup 8}, showing that the duality-violation effects have been underestimated in previous literature.
NASA Astrophysics Data System (ADS)
Cao, Shanshan; Luo, Tan; Qin, Guang-You; Wang, Xin-Nian
2016-07-01
A linearized Boltzmann transport (LBT) model coupled with hydrodynamical background is established to describe the evolution of jet shower partons and medium excitations in high energy heavy-ion collisions. We extend the LBT model to include both elastic and inelastic processes for light and heavy partons in the quark-gluon plasma. A hybrid model of fragmentation and coalescence is developed for the hadronization of heavy quarks. Within this framework, we investigate how heavy flavor observables depend on various ingredients, such as different energy loss and hadronization mechanisms, the momentum and temperature dependences of the transport coefficients, and the radial flow of the expanding fireball. Our model calculations show good descriptions of the D meson suppression and elliptic flow observed at the Larege Hadron Collider and the Relativistic Heavy-Ion Collider. The prediction for the Pb-Pb collisions at √{sN N}=5.02 TeV is provided.
Chirally symmetric but confining dense, cold matter
NASA Astrophysics Data System (ADS)
Glozman, L. Ya.; Wagenbrunn, R. F.
2008-03-01
The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at T=0 and finite chemical potential μ and obtain a clear chiral restoration phase transition at the critical value μcr. Below this value the spectrum is similar to the previously obtained one at μ=0. At μ>μcr the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.
Chirally symmetric but confining dense, cold matter
Glozman, L. Ya.; Wagenbrunn, R. F.
2008-03-01
The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at T=0 and finite chemical potential {mu} and obtain a clear chiral restoration phase transition at the critical value {mu}{sub cr}. Below this value the spectrum is similar to the previously obtained one at {mu}=0. At {mu}>{mu}{sub cr} the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.
Dissipative vibrational model for chiral recognition in olfaction
NASA Astrophysics Data System (ADS)
Tirandaz, Arash; Taher Ghahramani, Farhad; Shafiee, Afshin
2015-09-01
We examine the olfactory discrimination of left- and right-handed enantiomers of chiral odorants based on the odorant-mediated electron transport from a donor to an acceptor of the olfactory receptors embodied in a biological environment. The chiral odorant is effectively described by an asymmetric double-well potential whose minima are associated to the left- and right-handed enantiomers. The introduced asymmetry is considered an overall measure of chiral interactions. The biological environment is conveniently modeled as a bath of harmonic oscillators. The resulting spin-boson model is adapted by a polaron transformation to derive the corresponding Born-Markov master equation with which we obtain the elastic and inelastic electron tunneling rates. We show that the inelastic tunneling through left- and right-handed enantiomers occurs with different rates. The discrimination mechanism depends on the ratio of tunneling frequency to localization frequency.
Quark mean field model with pion and gluon corrections
NASA Astrophysics Data System (ADS)
Xing, Xueyong; Hu, Jinniu; Shen, Hong
2016-10-01
The properties of nuclear matter and finite nuclei are studied within the quark mean field (QMF) model by taking the effects of pions and gluons into account at the quark level. The nucleon is described as the combination of three constituent quarks confined by a harmonic oscillator potential. To satisfy the spirit of QCD theory, the contributions of pions and gluons on the nucleon structure are treated in second-order perturbation theory. In a nuclear many-body system, nucleons interact with each other by exchanging mesons between quarks. With different constituent quark mass, mq, we determine three parameter sets for the coupling constants between mesons and quarks, named QMF-NK1, QMF-NK2, and QMF-NK3, by fitting the ground-state properties of several closed-shell nuclei. It is found that all of the three parameter sets can give a satisfactory description of properties of nuclear matter and finite nuclei, moreover they also predict a larger neutron star mass around 2.3 M⊙ without hyperon degrees of freedom.
Estimate of quantum corrections to the mass of the chiral soliton in the Nambu-Jona-Lasinio model
NASA Astrophysics Data System (ADS)
Weigel, H.; Alkofer, R.; Reinhardt, H.
1995-01-01
The Bethe-Salpeter equation for pion fluctuations off the chiral soliton in the Nambu-Jona-Lasinio model is constructed. By Goldstone's theorem this equation has rotational and translational zero-modes because the classical soliton is a localized stationary field configuration which violates rotational and translational invariance. Furthermore, the proper normalization of the fluctuating eigenmodes is obtained. Second quantization of the pion fluctuations off the chiral soliton provides an energy functional of the pion fluctuations which formally coincides with that of a harmonic oscillator. The corresponding quantum corrections to the soliton mass together with the semi-classical cranking prescription yield reasonable predictions for the masses of the nucleon and the Δ-resonance when the constituent quark mass is chosen to be about 400 MeV. These calculations are, to some extent, hampered by the non-confining character of the Nambu-Jona-Lasinio model. Comments on the 1/ NC counting scheme are added.
Gapless chiral spin liquid in a kagome Heisenberg model
NASA Astrophysics Data System (ADS)
Bieri, Samuel; Messio, Laura; Bernu, Bernard; Lhuillier, Claire
2015-08-01
Motivated by recent experiments on the Heisenberg S =1 /2 quantum spin liquid candidate material kapellasite, we classify all possible chiral (time-reversal symmetry breaking) spin liquids with fermionic spinons on the kagome lattice. We obtain the phase diagram for the physically relevant extended Heisenberg model, comparing the energies of a wide range of microscopic variational wave functions. We propose that, at low temperature, kapellasite exhibits a gapless chiral spin liquid phase with spinon Fermi surfaces. This two-dimensional state inherits many properties of the nearby one-dimensional phase of decoupled antiferromagnetic spin chains, but also shows some remarkable differences. We discuss the spin structure factors and other physical properties.
Thermodynamics of an exactly solvable confining quark model
NASA Astrophysics Data System (ADS)
Mintz, Bruno W.
2016-04-01
The grand partition function of a model of confined quarks is exactly calculated at arbitrary temperatures and quark chemical potentials. The model is inspired by a version of QCD where the usual (perturbative) BRST symmetry is broken in the infrared, while possessing a quark mass function compatible with nonperturbative analyses of lattice simulations and Dyson-Schwinger equations. Even though the model is defined at tree level, we show that it produces a non-trivial and stable thermodynamic behaviour at any temperature or chemical potential. Results for the pressure, the entropy and the trace anomaly as a function of the temperature are qualitatively compatible with the effect of non-perturbative interactions as observed in lattice simulations. The finite density thermodynamics is also shown to contain non-trivial features, being far away from an ideal gas picture.
Thermodynamics of an exactly solvable confining quark model
NASA Astrophysics Data System (ADS)
Guimaraes, M. S.; Mintz, B. W.; Palhares, L. F.
2015-10-01
The grand partition function of a model of confined quarks is exactly calculated at arbitrary temperatures and quark chemical potentials. The model is inspired by a version of QCD with a soft breaking of the Becchi-Rouet-Stora-Tyutin symmetry and possesses a quark mass function compatible with nonperturbative analyses of lattice simulations and Dyson-Schwinger equations. Even though the model is defined at tree level, we show that it produces a nontrivial and stable thermodynamic behavior at any temperature or chemical potential. Results for the pressure, the entropy and the trace anomaly as a function of the temperature are qualitatively compatible with the effect of nonperturbative interactions as observed in lattice simulations. The finite density thermodynamics is also shown to contain nontrivial features, being far away from an ideal gas picture.
Strange hadronic loops of the proton: A quark model calculation
Paul Geiger; Nathan Isgur
1996-10-01
Nontrivial q{anti q} sea effects have their origin in the low-Q{sup 2} dynamics of strong QCD. The authors present here a quark model calculation of the contribution of s{anti s} pairs arising from a complete set of OZI-allowed strong Y{sup *}K{sup *} hadronic loops to the net spin of the proton, to its charge radius, and to its magnetic moment. The calculation is performed in an ``unquenched quark model'' which has been shown to preserve the spectroscopic successes of the naive quark model and to respect the OZI rule. They speculate that an extension of the calculation to the nonstrange sea will show that most of the ``missing spin'' of the proton is in orbital angular momenta.
NASA Astrophysics Data System (ADS)
Ghosh, Sabyasachi; Peixoto, Thiago C.; Roy, Victor; Serna, Fernando E.; Krein, Gastão
2016-04-01
We have calculated the temperature dependence of shear η and bulk ζ viscosities of quark matter due to quark-meson fluctuations. The quark thermal width originating from quantum fluctuations of quark-π and quark-σ loops at finite temperature is calculated with the formalism of real-time thermal field theory. Temperature-dependent constituent-quark and meson masses and quark-meson couplings are obtained in the Nambu-Jona-Lasinio model. We found a nontrivial influence of the temperature-dependent masses and couplings on the Landau-cut structure of the quark self-energy. Our results for the ratios η /s and ζ /s , where s is the entropy density (also determined in the Nambu-Jona-Lasinio model in the quasiparticle approximation), are in fair agreement with results of the literature obtained from different models and techniques. In particular, our result for η /s has a minimum very close to the quantum lower bound, η /s =1 /4 π .
Self-consistent Models of Strong Interaction with Chiral Symmetry
DOE R&D Accomplishments Database
Nambu, Y.; Pascual, P.
1963-04-01
Some simple models of (renormalizable) meson-nucleon interaction are examined in which the nucleon mass is entirely due to interaction and the chiral ( gamma {sub 5}) symmetry is "broken'' to become a hidden symmetry. It is found that such a scheme is possible provided that a vector meson is introduced as an elementary field. (auth)
Octet Baryon Electromagnetic Form Factors in a Relativistic Quark Model
Gilberto Ramalho, Kazuo Tsushima
2011-09-01
We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. As for the pion cloud contributions, we parameterize them in a covariant, phenomenological manner, combined with SU(3) symmetry. We also discuss the impact of the pion cloud effects on the octet baryon electromagnetic form factors and their radii.
Chiral Thirring–Wess model with Faddeevian regularization
Rahaman, Anisur
2015-03-15
Replacing vector type of interaction of the Thirring–Wess model by the chiral type a new model is presented which is termed here as chiral Thirring–Wess model. Ambiguity parameters of regularization are so chosen that the model falls into the Faddeevian class. The resulting Faddeevian class of model in general does not possess Lorentz invariance. However we can exploit the arbitrariness admissible in the ambiguity parameters to relate the quantum mechanically generated ambiguity parameters with the classical parameter involved in the masslike term of the gauge field which helps to maintain physical Lorentz invariance instead of the absence of manifestly Lorentz covariance of the model. The phase space structure and the theoretical spectrum of this class of model have been determined through Dirac’s method of quantization of constraint system.
A Composite Model of Quarks with the `Effective Supersymmetry'
NASA Astrophysics Data System (ADS)
Okada, N.
1998-04-01
We present a composite model of quarks with `effective supersymmetry'. The model is based on the gauge group (SU(2)S × SU(2)M) × (SU(2)U × SU(2)C × SU(2)T) × SU(5)SM , where SU(5)SM is the standard model gauge group. In the dynamical supersymmetry breaking sector based on the gauge group SU(2)S × SU(2)M , supersymmetry is dynamically broken. The preon sector is constructed by the model proposed by Nelson and Strassler. The fermion mass hierarchy among the up-type quarks originates from the SU(2)U × SU(2)C × SU(2)T gauge dynamics. The supersymmetry breaking is mediated to the minimal supersymmetric standard model sector by the `preon' superfields which compose the quarks in the first two generations. To obtain an experimentally acceptable mass spectrum, the scalar quarks in the first two generations need masses of order 10 TeV, while the other superpartners need masses less than 1 TeV. Therefore, the mass spectrum in our model is one example of the `effective supersymmetry' model proposed by Cohen, Kaplan and Nelson.
An Anderson-like model of the QCD chiral transition
NASA Astrophysics Data System (ADS)
Giordano, Matteo; Kovács, Tamás G.; Pittler, Ferenc
2016-06-01
We study the problems of chiral symmetry breaking and eigenmode localisation in finite-temperature QCD by looking at the lattice Dirac operator as a random Hamiltonian. We recast the staggered Dirac operator into an unconventional three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying internal degrees of freedom, with disorder provided by the fluctuations of the gauge links. In this framework, we identify the features relevant to chiral symmetry restoration and localisation of the low-lying Dirac eigenmodes in the ordering of the local Polyakov lines, and in the related correlation between spatial links across time slices, thus tying the two phenomena to the deconfinement transition. We then build a toy model based on QCD and on the Dirac-Anderson approach, replacing the Polyakov lines with spin variables and simplifying the dynamics of the spatial gauge links, but preserving the above-mentioned relevant dynamical features. Our toy model successfully reproduces the main features of the QCD spectrum and of the Dirac eigenmodes concerning chiral symmetry breaking and localisation, both in the ordered (deconfined) and disordered (confined) phases. Moreover, it allows us to study separately the roles played in the two phenomena by the diagonal and the off-diagonal terms of the Dirac-Anderson Hamiltonian. Our results support our expectation that chiral symmetry restoration and localisation of the low modes are closely related, and that both are triggered by the deconfinement transition.
Nucleation of quark matter in the PQM model
Mintz, Bruno W.; Stiele, Rainer; Schaffner-Bielich, Juergen; Ramos, Rudnei O.
2013-03-25
We use Langer's theory to calculate the surface tension of critical bubbles in a first-order quark-hadron phase transition at moderate and high baryon chemical potential, as predicted by the Polyakov-Quark-Meson (PQM) model at the mean-field level. We define an effective 4-dimensional order parameter, which is used to overestimate the surface tension of nucleating bubbles within the thin-wall approximation. We find relatively low values for the surface tension, {Sigma} Less-Than-Or-Equivalent-To 15MeV/fm{sup 2}. This implies that a metastable state, such as a supercooled quark-gluon plasma (QGP), quickly decays even in regions relatively close to the coexistence line of the phase diagram. Possible consequences for cosmology are briefly outlined.
Rare {Lambda}{sub b} decays in a quark model
Mott, L.; Roberts, W.
2010-08-05
Hadronic form factors for the rare weak transitions {Lambda}{sub b{yields}{Lambda}}{sup (*)} are calculated using a nonrelativistic quark model. The form factors obtained in this way are found to satisfy the relationships expecetd from the heavy quark effective theory. Differential decay rates and branching ratios are calculated for the dileptonic decays {Lambda}{sub b{yields}{Lambda}}{sup (*)}l{sup +}l{sup -}, for both ground state and excited daughter baryons. Inclusion of the long distance contributions from charmonium resonances significantly enhances the decay rates. Future work is outlined.
NASA Technical Reports Server (NTRS)
Takahashi, Y.; Eby, P. B.
1985-01-01
Possibilities of observing abundances of phi mesons and narrow hadronic pairs, as results of QGP and Chiral transitions, are considered for nucleus-nucleus interactions. Kinematical requirements in forming close pairs are satisfied in K+K decays of S(975) and delta (980) mesons with small phi, and phi (91020) mesons with large PT, and in pi-pi decays of familiar resonance mesons only in a partially restored chiral symmetry. Gluon-gluon dominance in QGP can enhance phi meson production. High hadronization rates of primordial resonance mesons which form narrow hadronic pairs are not implausible. Past cosmic ray evidences of anomalous phi production and narrow pair abundances are considered.
Constituent quarks in the Standard Model
NASA Astrophysics Data System (ADS)
Sukhoruchkin, Sergey
2016-02-01
Tuning effect in particle masses manifests itself in integer relations between masses of leptons, quarks, meson and baryons. It includes also dimensionless relation between such well-known SM-parameters as masses of the muon and Z-boson, mμ/MZ=115.9·10-5 coinciding with the QED radiative correction α/2π=115.9·10-5 considered for the electron mass me by V. Belokurov and D. Shirkov. Integer presentation of particle masses (n=1,13,16,17,18,115) for values mμ, fπ, mπ, ΔMΔ, neutron mass and (n=3x16, n=3x18) for constituent quarks M"q=mp,mω/2=780 MeV and Mq=3ΔMΔ=mΞ/3=441 MeV were found with the period δ=16me. More accurate relations with δ were found from precise ratio mn/me=1838.6836605(11). The shift δmn=161.65(6) keV of neutron mass from 115δ-me accounts integer ratio δmN/δmn=8(1.0001(1)) with nucleon mass splitting. With fundamental boson masses the parameters Mq=3ΔMΔ=mΞ/3=441 MeV and M”q =mρ/2=388.8(2) MeV are in ratios MZ/Mq=LZ=206.8 and MW/M”q =LW=207.3 coinciding with lepton ratio L=mμ/me=13·16-1=207.
Sensitivity to properties of the phi-meson in the nucleon structure in the chiral soliton model
Mukhopadhyay, N.C.; Zhang, L.
1994-04-01
The influence of the {phi}-meson on the nucleon properties in the chiral soliton model is discussed. Properties of the {phi}-meson and its photo- and electroproduction are of fundamental interest to CEBAF and its possible future extension. The quark model assigns {phi} an s{bar s} structure, thus forbidding the radiative decay {phi}{yields}{pi}{sup 0}{gamma}. Experimentally it is also found to be suppressed, yielding a branching fraction of 1.3{times}10{sup {minus}3}. However, {phi}{yields}{rho}{pi} and {phi}{yields}{pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} are not suppressed at all. Thus, it is possible to incorporate the widths of these decays into the framework of the chiral soliton model, by making use of a specific model for the compliance with OZI rule. Such a model is for example, the {omega}-{phi} mixing model. Consequence of this in the context of a chiral soliton model, which builds on the {pi}{rho}{omega}a{sub 1}(f{sub 1}) meson effective Lagrangian, is the context of this report.
Quark-gluon vertex from the Landau gauge Curci-Ferrari model
NASA Astrophysics Data System (ADS)
Peláez, Marcela; Tissier, Matthieu; Wschebor, Nicolás
2015-08-01
We investigate the quark-gluon three-point correlation function within a one-loop computation performed in the Curci-Ferrari massive extension of the Faddeev-Popov gauge-fixed action. The mass term is used as a minimal way for taking into account the influence of the Gribov ambiguity. Our results, with renormalization-group improvement, are compared with lattice data. We show that the comparison is, in general, very satisfactory for the functions which are compatible with chiral symmetry, except for one. We argue that this may be due to large systematic errors when extracting this function from lattice simulations. The quantities which break chiral symmetry are more sensitive to the details of the renormalization scheme. We, however, manage to reproduce some of them with good precision. The chosen parameters allow us to simultaneously fit the quark mass function coming from the quark propagator with reasonable agreement.
Quark fragmentation functions in NJL-jet model
NASA Astrophysics Data System (ADS)
Bentz, Wolfgang; Matevosyan, Hrayr; Thomas, Anthony
2014-09-01
We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. Supported by Grant in Aid for Scientific Research, Japanese Ministry of Education, Culture, Sports, Science and Technology, Project No. 20168769.
Nucleon-Nucleon Interactions from the Quark Model
Downum, C.; Stone, J. R.; Barnes, T.; Swanson, E. S.; Vidana, I.
2010-08-05
We report on investigations of the applicability of non-relativistic constituent quark models to the low-energy nucleon-nucleon (NN) interaction. The major innovations of a resulting NN potential are the use of the {sup 3}P{sub 0} decay model and quark model wave functions to derive nucleon-nucleon-meson form-factors, and the use of a colored spin-spin contact hyperfine interaction to model the repulsive core rather than the phenomenological treatment common in other NN potentials. We present the results of the model for experimental free NN scattering phase shifts, S-wave scattering lengths and effective ranges and deuteron properties. Plans for future study are discussed.
Microscopically constrained mean-field models from chiral nuclear thermodynamics
NASA Astrophysics Data System (ADS)
Rrapaj, Ermal; Roggero, Alessandro; Holt, Jeremy W.
2016-06-01
We explore the use of mean-field models to approximate microscopic nuclear equations of state derived from chiral effective field theory across the densities and temperatures relevant for simulating astrophysical phenomena such as core-collapse supernovae and binary neutron star mergers. We consider both relativistic mean-field theory with scalar and vector meson exchange as well as energy density functionals based on Skyrme phenomenology and compare to thermodynamic equations of state derived from chiral two- and three-nucleon forces in many-body perturbation theory. Quantum Monte Carlo simulations of symmetric nuclear matter and pure neutron matter are used to determine the density regimes in which perturbation theory with chiral nuclear forces is valid. Within the theoretical uncertainties associated with the many-body methods, we find that select mean-field models describe well microscopic nuclear thermodynamics. As an additional consistency requirement, we study as well the single-particle properties of nucleons in a hot/dense environment, which affect e.g., charged-current weak reactions in neutron-rich matter. The identified mean-field models can be used across a larger range of densities and temperatures in astrophysical simulations than more computationally expensive microscopic models.
discrete group as a source of the quark mass and mixing pattern in models
NASA Astrophysics Data System (ADS)
Cárcamo Hernández, A. E.; Martinez, R.; Nisperuza, Jorge
2015-02-01
We propose a model based on the gauge symmetry with an extra discrete group, which successfully accounts for the SM quark mass and mixing pattern. The observed hierarchy of the SM quark masses and quark mixing matrix elements arises from the and symmetries, which are broken at a very high scale by the scalar singlets (,) and , charged under these symmetries, respectively. The Cabbibo mixing arises from the down-type quark sector whereas the up quark sector generates the remaining quark mixing angles. The obtained magnitudes of the CKM matrix elements, the CP violating phase, and the Jarlskog invariant are in agreement with the experimental data.
Continuum model for chiral induced spin selectivity in helical molecules
Medina, Ernesto; González-Arraga, Luis A.; Finkelstein-Shapiro, Daniel; Mujica, Vladimiro; Berche, Bertrand
2015-05-21
A minimal model is exactly solved for electron spin transport on a helix. Electron transport is assumed to be supported by well oriented p{sub z} type orbitals on base molecules forming a staircase of definite chirality. In a tight binding interpretation, the spin-orbit coupling (SOC) opens up an effective π{sub z} − π{sub z} coupling via interbase p{sub x,y} − p{sub z} hopping, introducing spin coupled transport. The resulting continuum model spectrum shows two Kramers doublet transport channels with a gap proportional to the SOC. Each doubly degenerate channel satisfies time reversal symmetry; nevertheless, a bias chooses a transport direction and thus selects for spin orientation. The model predicts (i) which spin orientation is selected depending on chirality and bias, (ii) changes in spin preference as a function of input Fermi level and (iii) back-scattering suppression protected by the SO gap. We compute the spin current with a definite helicity and find it to be proportional to the torsion of the chiral structure and the non-adiabatic Aharonov-Anandan phase. To describe room temperature transport, we assume that the total transmission is the result of a product of coherent steps.
Color symmetrical superconductivity in a schematic nuclear quark model
NASA Astrophysics Data System (ADS)
Bohr, H.; Providência, C.; da Providência, J.
2010-02-01
In this letter, a novel BCS-type formalism is constructed in the framework of a schematic QCD inspired quark model, having in mind the description of color symmetrical superconducting states. In the usual approach to color superconductivity, the pairing correlations affect only the quasi-particle states of two colors, the single-particle states of the third color remaining unaffected by the pairing correlations. In the theory of color symmetrical superconductivity here proposed, the pairing correlations affect symmetrically the quasi-particle states of the three colors and vanishing net color charge is automatically insured. We stress that the present note is concerned with the description of quark matter in terms of effective models, such as the NJL model, which are solely expressed in terms of fermion operators, so that in them the gluonic gauge fields are not present.
Chiral symmetry breaking beyond BCS and theorem on the width of scalars
Bicudo, P.
2008-08-31
We review chiral symmetry breaking at the BCS level, in the framework of chiral invariant quark models and in the Schwinger-Dyson formalism. We revisit the {pi} mass problem beyond the BCS level. We show a theorem on the masses, on the widths and on the qq-bar content of the scalar mesons {sigma} and f{sub 0}.
Midrapidity inclusive densities in high energy pp collisions in additive quark model
NASA Astrophysics Data System (ADS)
Shabelski, Yu. M.; Shuvaev, A. G.
2016-08-01
High energy (CERN SPS and LHC) inelastic pp (pbar{p}) scattering is treated in the framework of the additive quark model together with Pomeron exchange theory. We extract the midrapidity inclusive density of the charged secondaries produced in a single quark-quark collision and investigate its energy dependence. Predictions for the π p collisions are presented.
Intrinsic transverse momentum and dynamical chiral symmetry breaking
Christian Weiss, Peter Schweitzer, Mark Strikman
2013-01-01
We study the effect of QCD vacuum structure on the intrinsic transverse momentum distribution of partons in the nucleon at a low scale. The dynamical breaking of chiral symmetry is caused by non-perturbative interactions at distances of the order rho ~ 0.2 - 0.3 fm, much smaller than the typical nucleon size R ~ 1 fm, resulting in a two-scale picture of nucleon structure. Using an effective dynamical model based on chiral constituent quark degrees of freedom and the 1/N_c expansion (chiral quark-soliton model), we calculate the transverse momentum distribution of quarks and antiquarks at a low scale. The distribution of valence quarks is localized at p_T ~ 1/R. The distribution of flavor-singlet unpolarized sea quarks exhibits a power-like tail extending up to the chiral-symmetry-breaking scale 1/{rho}. A similar tail is present in the flavor-nonsinglet polarized sea. These features are model-independent and represent the imprint of the QCD vacuum on the nucleon's partonic structure. At the level of the nucleon's light-cone wave function, we show that sea quarks partly exist in correlated pairs of transverse size {rho} << R, analogous to short-range NN correlations in nuclei. We discuss the implications of our findings for the transverse momentum distributions in hard scattering processes (semi-inclusive DIS, Drell-Yan pair production) and possible experimental tests of the non-perturbative parton correlations induced by QCD vacuum structure.
Angular correlations in top quark decays in standard model extensions
Batebi, S.; Etesami, S. M.; Mohammadi-Najafabadi, M.
2011-03-01
The CMS Collaboration at the CERN LHC has searched for the t-channel single top quark production using the spin correlation of the t-channel. The signal extraction and cross section measurement rely on the angular distribution of the charged lepton in the top quark decays, the angle between the charged lepton momentum and top spin in the top rest frame. The behavior of the angular distribution is a distinct slope for the t-channel single top (signal) while it is flat for the backgrounds. In this Brief Report, we investigate the contributions which this spin correlation may receive from a two-Higgs doublet model, a top-color assisted technicolor (TC2) and the noncommutative extension of the standard model.
Semileptonic decays of double heavy baryons in a relativistic constituent three-quark model
Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E.; Ivanov, Mikhail A.; Koerner, Juergen G.
2009-08-01
We study the semileptonic decays of double-heavy baryons using a manifestly Lorentz covariant constituent three-quark model. We present complete results on transition form factors between double-heavy baryons for finite values of the heavy quark/baryon masses and in the heavy quark symmetry limit, which is valid at and close to zero recoil. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit.
Broken chiral symmetry on a null plane
Beane, Silas R.
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-plane 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.
NN interaction from bag-model quark interchange
Bakker, B.L.G.; Bozoian, M.; Maslow, J.N.; Weber, H.J.
1982-03-01
A partial-wave helicity-state analysis of elastic nucleon-nucleon scattering is carried out in momentum space. Its basis is a one- and two-boson exchange amplitude from a bag-model quark interchange mechanism. The resulting phase shifts and bound-state parameters of the deuteron are compared with other meson theoretic potentials and data up to laboratory energies of approx.350 MeV.
Semileptonic Decays of Heavy Omega Baryons in a Quark Model
Muslema Pervin; Winston Roberts; Simon Capstick
2006-03-24
The semileptonic decays of {Omega}{sub c} and {Omega}{sub b} are treated in the framework of a constituent quark model developed in a previous paper on the semileptonic decays of heavy {Lambda} baryons. Analytic results for the form factors for the decays to ground states and a number of excited states are evaluated. For {Omega}{sub b} to {Omega}{sub c} the form factors obtained are shown to satisfy the relations predicted at leading order in the heavy-quark effective theory at the non-recoil point. A modified fit of nonrelativistic and semirelativistic Hamiltonians generates configuration-mixed baryon wave functions from the known masses and the measured {Lambda}{sub c}{sup +} {yields} {Lambda}e{sup +}{nu} rate, with wave functions expanded in both harmonic oscillator and Sturmian bases. Decay rates of {Omega}{sub b} to pairs of ground and excited {Omega}{sub c} states related by heavy-quark symmetry calculated using these configuration-mixed wave functions are in the ratios expected from heavy-quark effective theory, to a good approximation. Our predictions for the semileptonic elastic branching fraction of {Omega}{sub Q} vary minimally within the models we use. We obtain an average value of (84 {+-} 2%) for the fraction of {Omega}{sub c} {yields} {Xi}{sup (*)} decays to ground states, and 91% for the fraction of {Omega}{sub c} {yields} {Omega}{sup (*)} decays to the ground state {Omega}. The elastic fraction of {Omega}{sub b} {yields} {Omega}{sub c} ranges from about 50% calculated with the two harmonic-oscillator models, to about 67% calculated with the two Sturmian models.
Chiral Extrapolation of Lattice Data for Heavy Meson Hyperfine Splittings
X.-H. Guo; P.C. Tandy; A.W. Thomas
2006-03-01
We investigate the chiral extrapolation of the lattice data for the light-heavy meson hyperfine splittings D*-D and B*-B to the physical region for the light quark mass. The chiral loop corrections providing non-analytic behavior in m{sub {pi}} are consistent with chiral perturbation theory for heavy mesons. Since chiral loop corrections tend to decrease the already too low splittings obtained from linear extrapolation, we investigate two models to guide the form of the analytic background behavior: the constituent quark potential model, and the covariant model of QCD based on the ladder-rainbow truncation of the Dyson-Schwinger equations. The extrapolated hyperfine splittings remain clearly below the experimental values even allowing for the model dependence in the description of the analytic background.
Finite nuclei in relativistic models with a light chiral scalar meson
Serot, B.D.; Furnstahl, R.J.
1993-10-01
Relativistic chiral models with a light scalar, meson appear to provide an economical marriage of successful relativistic mean-field theories and chiral symmetry. In these models, the scalar meson serves as both the chiral partner of the pion and the mediator of the intermediate-range nucleon-nucleon (NN) attraction. However, while some of these models can reproduce the empirical nuclear matter saturation point, they fail to reproduce observed properties of finite nuclei, such as spin-orbit splittings, shell structure, charge densities, and surface energetics. There deficiencies imply that this realization of chiral symmetry is incorrect. An alternative scenario for chiral hadronic models, which features a heavy chiral scalar and dynamical generation of the NN attraction, is discussed.
Quasitriangular Chiral WZW Model in a Nutshell
NASA Astrophysics Data System (ADS)
Klimčík, C.
We give a bare-bone description of the quasitriangularchiral WZW model for the particular choice of the Lu-Weinstein-Soibelman Drinfeld double of the affine Kac-Moody group. The symplectic structure of the model and its Poisson-Lie symmetry are completely characterized by two r-matrices with spectral parameter. One of them is ordinary and trigonometric and characterizes the q-current algebra. The other is dynamical and elliptic (in fact Felder's one) and characterizes the braiding of q-primary fields.
Hyperon stars in a modified quark meson coupling model
NASA Astrophysics Data System (ADS)
Mishra, R. N.; Sahoo, H. S.; Panda, P. K.; Barik, N.; Frederico, T.
2016-09-01
We determine the equation of state (EOS) of nuclear matter with the inclusion of hyperons in a self-consistent manner by using a modified quark meson coupling model where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to σ ,ω , and ρ mesons through mean-field approximations. The effect of a nonlinear ω -ρ term on the EOS is studied. The hyperon couplings are fixed from the optical potential values and the mass-radius curve is determined satisfying the maximum mass constraint of 2 M⊙ for neutron stars, as determined in recent measurements of the pulsar PSR J0348+0432. We also observe that there is no significant advantage of introducing the nonlinear ω -ρ term in the context of obtaining the star mass constraint in the present set of parametrizations.
Successes and failures of the constituent quark model
Lipkin, H.J.
1982-01-01
Our approach considers the model as a possible bridge between QCD and the experimental data and examines its predictions to see where these succeed and where they fail. We also attempt to improve the model by looking for additional simple assumptions which give better fits to the experimental data. But we avoid complicated models with too many ad hoc assumptions and too many free parameters; these can fit everything but teach us nothing. We define our constituent quark model by analogy with the constituent electron model of the atom and the constituent nucleon model of the nucleus. In the same way that an atom is assumed to consist only of constituent electrons and a central Coulomb field and a nucleus is assumed to consist only of constituent nucleons hadrons are assumed to consist only of their constituent valence quarks with no bag, no glue, no ocean, nor other constituents. Although these constituent models are oversimplified and neglect other constituents we push them as far as we can. Atomic physics has photons and vacuum polarization as well as constituent electrons, but the constituent model is adequate for calculating most features of the spectrum when finer details like the Lamb shift are neglected. 54 references.
Phase structure in a chiral model of nuclear matter
Phat, Tran Huu; Anh, Nguyen Tuan; Tam, Dinh Thanh
2011-08-15
The phase structure of symmetric nuclear matter in the extended Nambu-Jona-Lasinio (ENJL) model is studied by means of the effective potential in the one-loop approximation. It is found that chiral symmetry gets restored at high nuclear density and a typical first-order phase transition of the liquid-gas transition occurs at zero temperature, T=0, which weakens as T grows and eventually ends up with a second-order critical point at T=20 MeV. This phase transition scenario is confirmed by investigating the evolution of the effective potential versus the effective nucleon mass and the equation of state.
Model-independent analysis of quark mass matrices
Choudhury, D.; Sarkar, U.
1989-06-01
In view of the apparent inconsistency of the Stech, Fritzsch-Stech, and Fritzsch-Shin models and only marginal agreement of the Fritzsch and modified Fritzsch-Stech models with recent data on /ital B//sub /ital d///sup 0/-/bar B/ /sub /ital d///sup 0/ mixing, we analyze the general quark mass matrices for three generations. Phenomenological considerations restrict the range of parameters involved to different sectors. In the present framework, the constraints corresponding to various /ital Ansa/$/ital uml/---/ital tze/ have been discussed.
The heavy Top Quark Partner in Little Higgs Models
Larios, F.; Perez, M. A.; Penunuri, F.
2008-07-02
Little Higgs models provide a natural explanation for the lightness of the Higgs mass. Through the mechanism of collective symmetry breaking, one loop quadratic divergent contributions to the Higgs mass are avoided. In these models a heavy partner of the Top quark appears as required to cancel out the Top's loop contribution. This heavy Top could be produced at the LHC mainly in the single mode. Because of flavor mixing a large FCNC gtT coupling can be generated at one loop that could boost the single T production mode through gg fusion.
Exotic hadron production in a quark combination model
Han Wei; Shao Fenglan; Li Shiyuan; Shang Yonghui; Yao Tao
2009-09-15
The philosophy on production of exotic hadrons (multiquark states) in the framework of the quark combination model is investigated, taking f{sub 0}(980) as an example. The production rate and p{sub T} spectra of f{sub 0}(980) considered as (ss) or (sqsq), respectively, are calculated and compared in Au+Au collisions at {radical}(s{sub NN})=200 GeV. The unitarity of various combination models, when open for exotic hadron production, is addressed.
Warm stellar matter within the quark-meson-coupling model
Panda, P. K.; Providencia, C.; Menezes, D. P.
2010-10-15
In the present article, we investigate stellar matter obtained within the quark-meson-coupling (QMC) model for fixed temperature and with the entropy of the order of 1 or 2 Boltzmann units per baryon for neutrino-free matter and matter with trapped neutrinos. A new prescription for the calculation of the baryon effective masses in terms of the free energy is used. Comparing the results of the present work with those obtained from the nonlinear Walecka model, smaller strangeness and neutrino fractions are predicted within QMC. As a consequence, QMC has a smaller window of metastability for conversion into a low-mass blackhole during cooling.
Azimuthal spin asymmetries in light-cone constituent quark models
Boffi, S.; Pasquini, B.; Efremov, A. V.; Schweitzer, P.
2009-05-01
We present results for all leading-twist azimuthal spin asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to T-even transverse-momentum dependent parton distribution functions on the basis of a light-cone constituent quark model. Attention is paid to discuss the range of applicability of the model, especially with regard to the scale dependence of the observables and the transverse-momentum dependence of the distributions. We find good agreement with available experimental data and present predictions to be further tested by future CLAS, COMPASS, and HERMES data.
Warm stellar matter within the quark-meson-coupling model
NASA Astrophysics Data System (ADS)
Panda, P. K.; Providência, C.; Menezes, D. P.
2010-10-01
In the present article, we investigate stellar matter obtained within the quark-meson-coupling (QMC) model for fixed temperature and with the entropy of the order of 1 or 2 Boltzmann units per baryon for neutrino-free matter and matter with trapped neutrinos. A new prescription for the calculation of the baryon effective masses in terms of the free energy is used. Comparing the results of the present work with those obtained from the nonlinear Walecka model, smaller strangeness and neutrino fractions are predicted within QMC. As a consequence, QMC has a smaller window of metastability for conversion into a low-mass blackhole during cooling.
Scadron, M. D.
2008-08-31
A model-independent chiral soft-pion theorem (SPT) shields the now observed scalar-meson ground-state isoscalar {sigma}(600) and isospinor {kappa}(800) resonances from detection in a{sub 1}{yields}{pi}({pi}{pi}){sub S-wave}, {gamma}{gamma}{yields}2{pi}{sup 0}, {pi}{sup -}P{yields}{pi}{sup -}{pi}{sup +}n, and K{sup -}P{yields}K{sup -}{pi}{sup +}n processes. Moreover, for pseudoscalar-to-vector-vector (PVV) decays, quark loops only are required.
General structure of democratic mass matrix of quark sector in E6 model
NASA Astrophysics Data System (ADS)
Ciftci, R.; ćiftci, A. K.
2016-03-01
An extension of the Standard Model (SM) fermion sector, which is inspired by the E6 Grand Unified Theory (GUT) model, might be a good candidate to explain a number of unanswered questions in SM. Existence of the isosinglet quarks might explain great mass difference of bottom and top quarks. Also, democracy on mass matrix elements is a natural approach in SM. In this study, we have given general structure of Democratic Mass Matrix (DMM) of quark sector in E6 model.
Strangeness in the Nucleon or the quark model beyond the valence approximation
Nathan Isgur
1999-01-01
Simple arguments based on unitarity indicate that meson loops diagrams, induced by an underlying qq pair creation process, should badly disturb the phenomenologically successful spectroscopy and dynamics of the valence quark model, including such simple but mysterious regularities as the OZI rule. The author discusses some recent progress in adding pair creation to the valence quark model in a way which provides rationale for the quark model's success.
Entanglement between deconfinement transition and chiral symmetry restoration
Sakai, Yuji; Sasaki, Takahiro; Yahiro, Masanobu; Kouno, Hiroaki
2010-10-01
We extend the Polyakov-loop extended Nambu-Jona-Lasinio model by introducing an effective four-quark vertex depending on the Polyakov loop. The effective vertex generates entanglement interactions between the Polyakov loop and the chiral condensate. The new model is consistent with lattice QCD data at imaginary quark-number chemical potential and real and imaginary isospin chemical potentials, particularly on the strong correlation between the chiral and deconfinement transitions and also on the quark-mass dependence of the order of the Roberge-Weiss endpoint. We investigate the influence of the entanglement interactions on the location of the tricritical point at real isospin chemical potential and on the location of the critical endpoint at real quark-number chemical potential.
Instantons, chiral dynamics, and hadronic resonances
Cristoforetti, M.; Faccioli, P.; Traini, M.
2007-03-01
We use the interacting instanton liquid model (IILM) as a tool to study the role played by the chiral interactions in the lowest-lying vector and axial-vector meson resonances. We find that narrow a{sub 1} and {rho} meson resonances can be generated by instanton-induced chiral forces, even in the absence of confinement. In the IILM, these hadrons are found to have masses only about 30% larger than the experimental value and small width < or approx. 10-50 MeV. This result suggests that chiral interactions are very important in these systems and provide most of their mass. We explore the decaying patterns of the {rho} meson, in the absence of confinement. We argue that, in our model where only chiral forces are switched on, this meson decays dissociating into its quark-antiquark constituents.
Viscous quark-gluon plasma model through fluid QCD approach
Djun, T. P.; Soegijono, B.; Mart, T.; Handoko, L. T. E-mail: Laksana.tri.handoko@lipi.go.id
2014-09-25
A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, are discussed. The energy momentum tensor that is relevant to the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.
Heavy-tailed chiral random matrix theory
NASA Astrophysics Data System (ADS)
Kanazawa, Takuya
2016-05-01
We study an unconventional chiral random matrix model with a heavy-tailed probabilistic weight. The model is shown to exhibit chiral symmetry breaking with no bilinear condensate, in analogy to the Stern phase of QCD. We solve the model analytically and obtain the microscopic spectral density and the smallest eigenvalue distribution for an arbitrary number of flavors and arbitrary quark masses. Exotic behaviors such as non-decoupling of heavy flavors and a power-law tail of the smallest eigenvalue distribution are illustrated.
Alajmi, Mohammed F; Hussain, Afzal; Suhail, Mohd; Mukhtar, Sofi Danish; Sahoo, Dibya Ranjan; Asnin, Leonid; Ali, Imran
2016-09-01
Chiral high-performance liquid chromatography (HPLC) separation and modeling of four stereomers of DL-leucine-tryptophan DL-dipeptide on AmyCoat-RP column are described. The mobile phase applied was ammonium acetate (10 mM)-methanol-acetonitrile (50:5:45, v/v). The flow rate of the mobile phases was 0.8 mL/min with UV detection at 230 nm. The values of retention factors for LL-, DD-, DL-, and LD- stereomers were 2.25, 3.60, 5.00, and 6.50, respectively. The values of separation and resolution factors were 1.60, 1.39, and 1.30 and 7.76, 8.05, and 7.19. The limits of detection and quantitation were ranging from 1.0-2.3 and 5.6-14.0 μg/mL. The simulation studies established the elution orders and the mechanism of chiral recognition. It was seen that π-π connections and hydrogen bondings were the main forces for enantiomeric resolution. The reported chiral HPLC method may be applied for the enantiomeric separation of DL-leucine-DL-tryptophan in unknown matrices. Chirality 28:642-648, 2016. © 2016 Wiley Periodicals, Inc. PMID:27474783
Diboson excess in the Higgs singlet and vectorlike quark models
NASA Astrophysics Data System (ADS)
Chen, Chuan-Hung; Nomura, Takaaki
2015-12-01
Diboson resonance with mass of 1.8-2 TeV is reported successively by CMS and ATLAS experiments in proton-proton collisions at √{s }=8 TeV . We investigate the potentiality of Higgs singlet as the TeV resonance. The challenges of low production cross section and high width for a fundamental scalar could be got over by three factors: (1) larger Yukawa couplings, (2) larger number of heavy quarks and (3) smaller mixing angle with standard model Higgs. We find that the required factors could be realized in the framework of two vectorlike triplet quarks (VLTQs) and the resulting production cross section and decay fraction of heavy Higgs σ (p p →H )×BR (H →W+W-+Z Z ) can be of O (10 ) fb when masses of new heavy quarks are 1 TeV, the values of Yukawa couplings are around 3 and the mixing angle is sin θ ˜0.11 . We also find that the SM Higgs production and its decay in the process p p →h →γ γ could be still consistent with current data when a color-triplet scalar (3 ,3 )1 /3 is considered. Furthermore, we study the product of VLTQ-pair production cross section and the BRs of VLTQ decays, and find that the cross sections in the decay channels, such as u4 ,5→b W+ , d5→t W- and d4→b h (Z ) could be 7-17 fb at 13 TeV LHC.
Finite Nuclei in the Quark-Meson Coupling Model.
Stone, J R; Guichon, P A M; Reinhard, P G; Thomas, A W
2016-03-01
We report the first use of the effective quark-meson coupling (QMC) energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the nonrelativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having a clear physics basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist, however, multiple Skyrme parameter sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter.
Finite Nuclei in the Quark-Meson Coupling Model.
Stone, J R; Guichon, P A M; Reinhard, P G; Thomas, A W
2016-03-01
We report the first use of the effective quark-meson coupling (QMC) energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the nonrelativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having a clear physics basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist, however, multiple Skyrme parameter sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter. PMID:26991171
How many parameters does a quark mass matrix model need
Koide, Y. )
1990-11-01
An investigation independent of matrix form is made of how many parameters, which characterize the difference between up- and down-quark mass matrices, are, at least, required from the present data on quark masses and mixings. From a general study of the model with hierarchical three-step mass generations described by the three parameters {alpha}{sub {ital q}}, {beta}{sub {ital q}}, and {gamma}{sub {ital q}} ({vert bar}{alpha}{sub {ital q}}{vert bar}{much gt}{vert bar}{beta}{sub {ital q}}{vert bar}{much gt}{vert bar}{gamma}{sub {ital q}}{vert bar}; {ital q}={ital u},{ital d}), it is pointed out that the model with {beta}{sub {ital u}}/{beta}{sub {ital d}}={gamma}{sub {ital u}}/{gamma}{sub {ital d}} (i.e., with two independent parameters {alpha}{sub {ital q}} and {beta}{sub {ital q}}) is ruled out.
Micropolar modeling of planar orthotropic rectangular chiral lattices
NASA Astrophysics Data System (ADS)
Chen, Yi; Liu, Xiaoning; Hu, Gengkai
2014-05-01
Rectangular chiral lattices possess a two-fold symmetry; in order to characterize the overall behavior of such lattices, a two-dimensional orthotropic chiral micropolar theory is proposed. Eight additional material constants are necessary to represent the anisotropy in comparison with triangular ones, four of which are devoted to chirality. Homogenization procedures are also developed for the chiral lattice with rigid or deformable circles, all material constants in the developed micropolar theory are derived analytically for the case of the rigid circles and numerically for the case of the deformable circles. The dependences of these material constants and of wave propagation on the microstructural parameters are also examined.
Entanglement between the Deconfinement and the Chiral Symmetry Restoration
Sakai, Yuji; Sasaki, Takahiro; Yahiro, Masanobu; Kouno, Hiroaki
2011-10-21
We extend the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model by introducing an effective four-quark vertex depending on the Polyakov loop. The effective vertex generates entanglement interactions between the Polyakov loop and the chiral condensate. The new model is consistent with lattice QCD data at imaginary quark-number chemical potential and real and imaginary isospin chemical potentials. We investigate the influence of the entanglement interactions on the location of the critical endpoint at real quark-number chemical potential.
Hyperon-hyperon interaction based on quark-model baryon-baryon interactions
NASA Astrophysics Data System (ADS)
Fukukawa, Kenji
2014-04-01
Energy-independent nonlocal Gaussian potential based on the quark-model baryon-baryon interaction is derived by using the Gauss-Legendre quadrature and the Bargmann algebra. The reliability of this potential is examined with respect to the NN, YN and YY phase shifts. This potential reproduces the phase shifts predicted by quark-model baryon-baryon interaction fss2.
Finite nuclei in relativistic models with a light chiral scalar meson
NASA Astrophysics Data System (ADS)
Furnstahl, R. J.; Serot, Brian D.
1993-05-01
Relativistic chiral models with a light scalar meson appear to provide an economical marriage of successful relativistic mean-field theories and chiral symmetry. The scalar meson serves as both the chiral partner of the pion and the mediator of the intermediate-range nucleon-nucleon (NN) attraction. However, while some of these models can reproduce the empirical nuclear matter saturation point, they fail to reproduce observed properties of finite nuclei, such as spin-orbit splittings, shell structure, charge densities, and surface energetics. These deficiencies imply that this realization of chiral symmetry is incorrect. An alternative scenario, which features a heavy chiral scalar and dynamical generation of the NN attraction, is discussed.
Chiral magnetic conductivity in an interacting lattice model of parity-breaking Weyl semimetal
NASA Astrophysics Data System (ADS)
Buividovich, P. V.; Puhr, M.; Valgushev, S. N.
2015-11-01
We report on the mean-field study of the chiral magnetic effect (CME) in static magnetic fields within a simple model of parity-breaking Weyl semimetal given by the lattice Wilson-Dirac Hamiltonian with constant chiral chemical potential. We consider both the mean-field renormalization of the model parameters and nontrivial corrections to the CME originating from resummed ladder diagrams with arbitrary number of loops. We find that onsite repulsive interactions affect the chiral magnetic conductivity almost exclusively through the enhancement of the renormalized chiral chemical potential. Our results suggest that nontrivial corrections to the chiral magnetic conductivity due to interfermion interactions are not relevant in practice since they only become important when the CME response is strongly suppressed by the large gap in the energy spectrum.
Finite nuclei in relativistic models with a light chiral scalar meson
Furnstahl, R.J. ); Serot, B.D. )
1993-05-01
Relativistic chiral models with a light scalar meson appear to provide an economical marriage of successful relativistic mean-field theories and chiral symmetry. The scalar meson serves as both the chiral partner of the pion and the mediator of the intermediate-range nucleon-nucleon ([ital NN]) attraction. However, while some of these models can reproduce the empirical nuclear matter saturation point, they fail to reproduce observed properties of finite nuclei, such as spin-orbit splittings, shell structure, charge densities, and surface energetics. These deficiencies imply that this realization of chiral symmetry is incorrect. An alternative scenario, which features a heavy chiral scalar and dynamical generation of the [ital NN] attraction, is discussed.
BPS states in supersymmetric chiral models with higher derivative terms
NASA Astrophysics Data System (ADS)
Nitta, Muneto; Sasaki, Shin
2014-11-01
We study the higher derivative chiral models with four supercharges and Bogomol'nyi-Prasad-Sommerfield (BPS) states in these models. The off-shell Lagrangian generically includes higher powers of the auxiliary fields F , which causes distinct on-shell branches associated with the solutions to the auxiliary fields equation. We point out that the model admits a supersymmetric completion of arbitrary higher derivative bosonic models of a single complex scalar field, and an arbitrary scalar potential can be introduced even without superpotentials. As an example, we present a supersymmetric extension of the Faddeev-Skyrme model without four time derivatives, in contrast to the previously proposed supersymmetric Faddeev-Skyrme-like model containing four time derivatives. In general, higher derivative terms together with a superpotential result in deformed scalar potentials. We find that higher derivative corrections to 1 /2 BPS domain walls and 1 /2 BPS lumps are exactly canceled out, while the 1 /4 BPS lumps (as compact baby Skyrmions) depend on a characteristic feature of the higher derivative models. We also find a new 1 /4 BPS condition for domain wall junctions, which generically receives higher derivative corrections.
Unquenched quark model for baryons: Magnetic moments, spins, and orbital angular momenta
Bijker, R.; Santopinto, E.
2009-12-15
We present an unquenched quark model for baryons in which the effects of the quark-antiquark pairs (uu, dd, and ss) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. In the present approach, the contribution of the quark-antiquark pairs can be studied for any inital baryon and for any flavor of the qq pairs. It is shown that, while the inclusion of the qq pairs does not affect the baryon magnetic moments, it leads to a sizable contribution of the orbital angular momentum to the spin of the proton and the {lambda} hyperon.
Thermodynamics and jet-quenching in the quark-gluon plasma from an AdS/QCD model
NASA Astrophysics Data System (ADS)
Lilleskov, Elias; Bartz, Sean
2015-10-01
The Anti-de Sitter Space/Conformal Field Theory Correspondence (AdS/CFT) has been used to study both hadronic dynamics and the thermodynamics and jet quenching behavior of the quark-gluon plasma created in heavy ion collisions. We attempt to connect the two regimes by adapting an AdS/QCD model previously used to study meson spectra to apply to the quark-gluon plasma. The model includes three fields: a dilaton to introduce confinement, and chiral and glueball condensates to reflect the zero-temperature dynamics. We dynamically solve the Einstein field equations to numerically determine the metric, which asymptotically describes an anti-de Sitter-Schwarzschild black hole solution. We then numerically calculate the temperature as a function of the black hole horizon location. Next, we determine the behavior of the entropy density, the speed of sound, and the jet quenching parameter as functions of the temperature. These quantities approach the behavior of a conformal plasma in the high temperature limit. The minimum of the temperature-horizon plot is interpreted as the plasma's deconfinement temperature, found to be 104 MeV.
Stochastic fluctuations and chiral symmetry breaking: exact solution of Lente model.
Shao, Jiushu; Liu, Lan
2007-09-27
The stochastic description for the autocatalytic process has been proposed by Lente (J. Phys. Chem. A 2004, 108, 9475) to demonstrate chiral symmetry breaking. He assumed that the number of reacting molecules is macroscopic and that no products are present initially. The Lente model consisting of a finite number of molecules that may include the product molecules as chiral seeds is explored and the characteristics of stochastic distributions of the product are examined. It is shown that the presence of racemic product in the substrate reduces the possibility of chiral symmetry breaking while a few more molecules of a specific enantiomer added can yield chiral dominance for strong autocatalysis. Besides, small reactive volumes or dense reactant concentrations have a preference for chiral symmetric breaking.
Aspects of the strongly interacting matter phase diagram within non-local quark models
Pagura, V.; Dumm, D. G.; Scoccola, N. N.
2013-03-25
We study a nonlocal extension of the so-called Polyakov Nambu-Jona-Lasinio model at finite temperature and chemical potential, considering the impact of the presence of dynamical quarks on the scale parameter appearing in the Polyakov potential. Both real and imaginary chemical potentials are considered. The effect of varying the current quark mass is also investigated.
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.
Chiral condensate in the Schwinger model with matrix product operators
NASA Astrophysics Data System (ADS)
Bañuls, Mari Carmen; Cichy, Krzysztof; Jansen, Karl; Saito, Hana
2016-05-01
Tensor network (TN) methods, in particular the matrix product states (MPS) ansatz, have proven to be a useful tool in analyzing the properties of lattice gauge theories. They allow for a very good precision, much better than standard Monte Carlo (MC) techniques for the models that have been studied so far, due to the possibility of reaching much smaller lattice spacings. The real reason for the interest in the TN approach, however, is its ability, shown so far in several condensed matter models, to deal with theories which exhibit the notorious sign problem in MC simulations. This makes it prospective for dealing with the nonzero chemical potential in QCD and other lattice gauge theories, as well as with real-time simulations. In this paper, using matrix product operators, we extend our analysis of the Schwinger model at zero temperature to show the feasibility of this approach also at finite temperature. This is an important step on the way to deal with the sign problem of QCD. We analyze in detail the chiral symmetry breaking in the massless and massive cases and show that the method works very well and gives good control over a broad range of temperatures, essentially from zero to infinite temperature.
S{sub 4} model for quarks and leptons with maximal atmospheric angle
Morisi, Stefano; Peinado, Eduardo
2010-04-15
We consider a model for quark and lepton masses and mixings based on S{sub 4} flavor symmetry. The model contains six Higgs doublets where three of them give mass to the leptons, and the other three gives mass to the quarks. Charged fermion and quark masses arise from renormalizable interactions while neutrino Majorana masses are generated through effective dimension five Weinberg operator. From the study of the minimization of the scalar potential we found a residual {mu}{r_reversible}{tau} symmetry in the neutrino sector predicting zero reactor angle and maximal atmospheric angle and for the quark sector we found a four-zero texture. We give a fit of the mass hierarchies and mixing angles in the quark sector.
Molecular modeling study of chiral drug crystals: lattice energy calculations.
Li, Z J; Ojala, W H; Grant, D J
2001-10-01
The lattice energies of a number of chiral drugs with known crystal structures were calculated using Dreiding II force field. The lattice energies, including van der Waals, Coulombic, and hydrogen-bonding energies, of homochiral and racemic crystals of some ephedrine derivatives and of several other chiral drugs, are compared. The calculated energies are correlated with experimental data to probe the underlying intermolecular forces responsible for the formation of racemic species, racemic conglomerates, or racemic compounds, termed chiral discrimination. Comparison of the calculated energies among ephedrine derivatives reveals that a greater Coulombic energy corresponds to a higher melting temperature, while a greater van der Waals energy corresponds to a larger enthalpy of fusion. For seven pairs of homochiral and racemic compounds, correlation of the differences between the two forms in the calculated energies and experimental enthalpy of fusion suggests that the van der Waals interactions play a key role in the chiral discrimination in the crystalline state. For salts of the chiral drugs, the counter ions diminish chiral discrimination by increasing the Coulombic interactions. This result may explain why salt forms favor the formation of racemic conglomerates, thereby facilitating the resolution of racemates.
Why the proton spin is not due to quarks
Karliner, M.
1988-07-01
Recent EMC data on the spin-dependent proton structure function suggest that very little of the proton spin is due to the helicity of the quarks inside it. We argue that, at leading order in the 1/N/sub c/ expansion, none of the proton spin would be carried by quarks in the chiral limit where m/sub q/ = 0. This model-independent result is based on a physical picture of the nucleon as a soliton solution of the effective chiral Lagrangian of large-N/sub c/ QCD. The Skyrme model is then used to estimate quark contribution to the proton spin when chiral symmetry and flavor SU(3) are broken: this contribution turns out to be small, as suggested by the EMC. Next, we discuss the other possible contributions to the proton helicity in the infinite-momentum frame---polarized gluons (..delta..G), and orbital angular momentum (L/sub z/). We argue on general grounds and by explicit example the ..delta..G = 0 and that if the parameters of the chiral Lagrangian are adjusted so that gluons carry /approximately/50% of the proton momentum, most of the orbital angular momentum L/sub z/ is carried by quarks. We mention several experiments to test the EMC results and their interpretation. 43 refs., 3 figs.
Chiral spin liquid in the extended Heisenberg model on the Kagome lattice
NASA Astrophysics Data System (ADS)
Hu, Wenjun; Zhu, Wei; Zhang, Yi; Gong, Shoushu; Becca, Federico; Sheng, Dongning; Donna Sheng Team
2015-03-01
We investigate the extended Heisenberg model on the Kagome lattice by using Gutzwiller projected fermionic states and the variational Monte Carlo technique. In particular, when both second- and third-neighbor super-exchanges are considered, we find that a gapped spin liquid described by non-trivial magnetic fluxes and long-range chiral-chiral correlations is energetically favored compared to the gapless U(1) Dirac state. Furthermore, the topological Chern number, obtained by integrating the Berry curvature, and the degeneracy of the ground state, by constructing linearly independent states, lead us to identify this flux state as the chiral spin liquid with C = 1 / 2 fractionalized Chern number.
Extending NEC to model wire objects in infinite chiral media. [Numerical electromagnetic code (NEC)
Burke, G.J. ); Miller, E.K. ); Bhattachryya, A.K. . Physical Science Lab.)
1992-01-01
The development of a moment-method model for wire objects in an infinite chiral medium is described. In this work, the Numerical Electromagnetics Code (NEC) was extended by including a new integral-equation kernel obtained from the dyadic Green's function for an infinite chiral medium. The NEC moment-method treatment using point matching and a three-term sinusoidal current expansion was adapted to the case of a chiral medium. Examples of current distributions and radiation patterns for simple antennas are presented, and the validation of the code is discussed. 15 refs.
Heavy-baryon quark model picture from lattice QCD
NASA Astrophysics Data System (ADS)
Vijande, J.; Valcarce, A.; Garcilazo, H.
2014-11-01
The ground state and excited spectra of baryons containing three identical heavy quarks, b or c , have been recently calculated in nonperturbative lattice QCD. The energy of positive and negative parity excitations has been determined with high precision. Lattice results constitute a unique opportunity to learn about the quark-confinement mechanism as well as elucidating our knowledge about the nature of the strong force. We analyze the nonperturbative lattice QCD results by means of heavy-quark static potentials derived using SU(3) lattice QCD. We make use of different numerical techniques for the three-body problem.
The Top Quark as a Window to Beyond the Standard Model Physics
Yu, Chiu-Tien
2013-01-01
The top quark was the last of the Standard Model quarks to be discovered, and is of considerable interest. The closeness of the top quark mass to the electroweak scale is suggestive that the top quark could be closely related to the mechanisms for electroweak symmetry breaking. Any new physics in electroweak symmetry breaking models could then preferentially couple to the top quark, making the top quark a promising probe for new physics. In this thesis, we will explore two aspects of the top quark as a harbinger to new physics: the top forward-backward asymmetry as seen at the Tevatron and the search for stops. In this thesis, we will discuss the Asymmetric Left-Right Model (ALRM), a model that is based on the gauge group $U'(1)\\times SU(2)\\times SU'(2)$ with couplings $g_1^\\prime, g_2^\\prime,$ and $g'$ associated with the fields $B',W,W'$, respectively, and show how this model can explain the top forward-backward asymmetry. We will then explore the scalar sector of the ALRM, and provide a specific Higgs mechanism that provides the masses for the $W'$ and $Z'$ bosons. The top forward-backward asymmetry is a test of invariance of charge-conjugation. Thus, we look at the $X$-gluon model, a model that was motivated by the top forward-backward asymmetry, and show that one can look at the longitudinal polarization of the top-quark to test parity conservation. Finally, we investigate searches for stop squarks, the supersymmetric partner of the top quark, at the Large Hadron Collider (LHC) using shape-based analyses.
Resurgence in η-deformed Principal Chiral Models
NASA Astrophysics Data System (ADS)
Demulder, Saskia; Dorigoni, Daniele; Thompson, Daniel C.
2016-07-01
We study the SU(2) Principal Chiral Model (PCM) in the presence of an integrable η-deformation. We put the theory on {R}× {S}^1 with twisted boundary conditions and then reduce the circle to obtain an effective quantum mechanics associated with the Whittaker-Hill equation. Using resurgent analysis we study the large order behaviour of perturbation theory and recover the fracton events responsible for IR renormalons. The fractons are modified from the standard PCM due to the presence of this η-deformation but they are still the constituents of uniton-like solutions in the deformed quantum field theory. We also find novel SL(2,{C}) saddles, thus strengthening the conjecture that the semi-classical expansion of the path integral gives rise to a resurgent transseries once written as a sum over Lefschetz thimbles living in a complexification of the field space. We conclude by connecting our quantum mechanics to a massive deformation of the {N} = 2 4-d gauge theory with gauge group SU(2) and N f = 2.
Quark matter symmetry energy and quark stars
Chu, Peng-Cheng; Chen, Lie-Wen
2014-01-10
We extend the confined-density-dependent-mass (CDDM) model to include isospin dependence of the equivalent quark mass. Within the confined-isospin-density-dependent-mass (CIDDM) model, we study the quark matter symmetry energy, the stability of strange quark matter, and the properties of quark stars. We find that including isospin dependence of the equivalent quark mass can significantly influence the quark matter symmetry energy as well as the properties of strange quark matter and quark stars. While the recently discovered large mass pulsars PSR J1614–2230 and PSR J0348+0432 with masses around 2 M {sub ☉} cannot be quark stars within the CDDM model, they can be well described by quark stars in the CIDDM model. In particular, our results indicate that the two-flavor u-d quark matter symmetry energy should be at least about twice that of a free quark gas or normal quark matter within the conventional Nambu-Jona-Lasinio model in order to describe PSR J1614–2230 and PSR J0348+0432 as quark stars.
Dark matter and dark energy from quark bag model
Brilenkov, Maxim; Eingorn, Maxim; Jenkovszky, Laszlo; Zhuk, Alexander E-mail: maxim.eingorn@gmail.com E-mail: ai.zhuk2@gmail.com
2013-08-01
We calculate the present expansion of our Universe endowed with relict colored objects — quarks and gluons — that survived hadronization either as isolated islands of quark-gluon ''nuggets'' or spread uniformly in the Universe. In the first scenario, the QNs can play the role of dark matter. In the second scenario, we demonstrate that uniform colored objects can play the role of dark energy providing the late-time accelerating expansion of the Universe.
Forward-backward asymmetry of the top quark in diquark models
Arhrib, Abdesslam; Benbrik, Rachid; Chen, Chuan-Hung
2010-08-01
Motivated by the recent unexpected large forward-backward asymmetry of the top-quark observed by D0 and CDF at the Tevatron, we investigate a possible explanation for the anomaly within the framework of diquark models. In the diquark models, the top-quark pair production is mediated by the u-channel diagram. It is found that the color-triplet diquark can generate the forward-backward asymmetry of 20% when the constraint from the cross section of the top-quark pair production is taken into account.
Matching the quark model to the 1/N{sub c} expansion
Pirjol, Dan; Schat, Carlos
2011-10-24
We compute the coefficients of the effective mass operator of the 1/N{sub c} expansion for negative parity L = 1 excited baryons using the Isgur-Karl model in order to compare the general approach, where the coefficients are obtained by fitting to data, with a specific constituent quark model calculation. We discuss the physics behind the fitted coefficients for the scalar part of the most general two-body quark-quark interaction. We find that both pion exchange and gluon exchange lead to the dominance of the same operator at the level of the effective mass operator, which is also observed from data.
NASA Astrophysics Data System (ADS)
Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry
2007-10-01
.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
Quark spectral function and deconfinement at nonzero temperature
NASA Astrophysics Data System (ADS)
Qin, Si-xue; Rischke, Dirk H.
2013-09-01
The maximum entropy method is used to compute the quark spectral function at nonzero temperature. We solve the gap equation of quantum chromodynamics (QCD) self-consistently, employing a rainbow kernel which phenomenologically models results from Dyson-Schwinger equations and lattice QCD. We use the criterion of positivity restoration of the spectral function as a signal for deconfinement. Our calculation indicates that the critical temperature of deconfinement Td is slightly smaller than the one of chiral symmetry restoration Tc: Td˜94%Tc in the chiral limit and Td˜96%Tc with physical light quark masses. Since these deviations are within the systematic error of our approach, it is reasonable to conclude that chiral symmetry restoration and deconfinement coincide at zero chemical potential.
Numerical modelling of chirality-induced bi-directional swimming of artificial flagella
Namdeo, S.; Khaderi, S. N.; Onck, P. R.
2014-01-01
Biomimetic micro-swimmers can be used for various medical applications, such as targeted drug delivery and micro-object (e.g. biological cells) manipulation, in lab-on-a-chip devices. Bacteria swim using a bundle of flagella (flexible hair-like structures) that form a rotating cork-screw of chiral shape. To mimic bacterial swimming, we employ a computational approach to design a bacterial (chirality-induced) swimmer whose chiral shape and rotational velocity can be controlled by an external magnetic field. In our model, we numerically solve the coupled governing equations that describe the system dynamics (i.e. solid mechanics, fluid dynamics and magnetostatics). We explore the swimming response as a function of the characteristic dimensionless parameters and put special emphasis on controlling the swimming direction. Our results provide fundamental physical insight on the chirality-induced propulsion, and it provides guidelines for the design of magnetic bi-directional micro-swimmers. PMID:24511253
Orientifold ABJM matrix model: chiral projections and worldsheet instantons
NASA Astrophysics Data System (ADS)
Moriyama, Sanefumi; Nosaka, Tomoki
2016-06-01
We study the partition function of the orientifold ABJM theory, which is a superconformal Chern-Simons theory associated with the orthosymplectic supergroup. We find that the partition function associated with any orthosymplectic supergroup can be realized as the partition function of a Fermi gas system whose density matrix is identical to that associated with the corresponding unitary supergroup with a projection to the even or odd chirality. Furthermore we propose an identity which gives directly all of the Gopakumar-Vafa invariants for the worldsheet instanton effects in the chirally projected theories. [Figure not available: see fulltext.
Quark Magnetar in Confined Isospin- and Density-dependent Mass Model
NASA Astrophysics Data System (ADS)
Chu, P. C.; Chen, L. W.; Wang, X.
2015-11-01
Within confined isospin- and density-dependent mass model, we study the equation of state(EOS) for the strange quark matter (SQM) and quark stars (QSs) under density-dependent magneticfields. The EOS of SQM is obtained self-consistently under a strong magnetic field, and thetransverse pressure which is perpendicular to the magnetic field is proved to be larger than thelongitudinal pressure that is parallel to the magnetic field. Our results indicate that the maximummass of quark magnetars can significantly increase (decrease) when the transverse (radial) magneticfield orientation is considered.
Effects of quark antisymmetrization in a schematic model of the nucleus
NASA Astrophysics Data System (ADS)
de Forest, T.; Mulders, P. J.
1987-05-01
It is shown that the effects of antisymmetrization between the quarks in different nucleons in the nucleus can be very strong. Using a schematic model in which a nucleus consists of two identical nucleons with two quarks each, the effects of antisymmetry on the charge form factor, quasielastic response function, Coulomb sum rule, and quark momentum distributions in nuclei are studied. In particular, it is found that the antisymmetrization leads to a violation of three commonly used prescriptions: factorization of the nucleon form factor, scaling in quasielastic electron scattering, and separation of nuclear and nucleon effects in Fermi smearing in deep-inelastic electron scattering.
NASA Astrophysics Data System (ADS)
Rajagopal, Krishna; Sadofyev, Andrey V.
2015-10-01
We provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in the sense that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks. The new contributions are proportional to the coefficient of the axial anomaly, and in this sense also are chiral. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect (CME) on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks, meaning that these novel effects do not in fact contribute to the CME current. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy quarks and
Interpretation of vector-like quark searches: heavy gluons in composite Higgs models
NASA Astrophysics Data System (ADS)
Araque, Juan Pedro; Castro, Nuno Filipe; Santiago, José
2015-11-01
Pair production of new vector-like quarks in pp collisions is considered model independent as it is usually dominated by QCD production. We discuss the interpretation of vector-like quark searches in the case that QCD is not the only relevant production mechanism for the new quarks. In particular we consider the effect of a new massive color octet vector boson with sizeable decay branching ratio into the new quarks. We pay special attention to the sensitivity of the Large Hadron Collider experiments, both in run-1 and early run-2, to differences in the kinematical distributions from the different production mechanisms. We have found that even though there can be significant differences in some kinematical distributions at the parton level, the differences are washed out at the reconstruction level. Thus, the published experimental results can be reinterpreted in models with heavy gluons by simply rescaling the production cross section.
Quark deconfinement in the proto-magnetar model of long gamma-ray bursts
NASA Astrophysics Data System (ADS)
Pili, A. G.; Bucciantini, N.; Drago, A.; Pagliara, G.; Del Zanna, L.
2016-10-01
We investigate the possible implications of quark deconfinement on the phenomenology of long gamma-ray bursts focusing, in particular, on the possibility to describe multiple prompt emission phases in the context of the proto-magnetar model. Starting from numerical models of rotating Hadron Stars and Quark Stars in full general relativity we track the electromagnetic spin-down evolution in both the hadronic and quark phase, linking the two families through conservation of baryon number and angular momentum. We give estimates of the time-scales and the energetics involved in the spin-down process deriving, in the relevant spin range, the relation between the initial and the final masses and rotational energies, whenever hadron-quark conversion is possible. We show how the results can be used in relevant astrophysical cases such as the double burst GRB 110709B.
Relativistic three-body quark model of light baryons based on hypercentral approach
NASA Astrophysics Data System (ADS)
Aslanzadeh, M.; Rajabi, A. A.
2015-05-01
In this paper, we have treated the light baryons as a relativistic three-body bound system. Inspired by lattice QCD calculations, we treated baryons as a spin-independent three-quark system within a relativistic three-quark model based on the three-particle Klein-Gordon equation. We presented the analytical solution of three-body Klein-Gordon equation with employing the constituent quark model based on a hypercentral approach through which two- and three-body forces are taken into account. Herewith the average energy values of the up, down and strange quarks containing multiplets are reproduced. To describe the hyperfine structure of the baryon, the splittings within the SU(6)-multiplets are produced by the generalized Gürsey Radicati mass formula. The considered SU(6)-invariant potential is popular "Coulomb-plus-linear" potential and the strange and non-strange baryons spectra are in general well reproduced.
Solvable model for many-quark systems in QCD Hamiltonians
Yepez-Martinez, Tochtli; Hess, P. O.; Civitarese, O.
2010-04-15
Motivated by a canonical QCD Hamiltonian, we propose an effective Hamiltonian to represent an arbitrary number of quarks in hadronic bags. The structure of the effective Hamiltonian is discussed and the BCS-type solutions that may represent constituent quarks are presented. The single-particle orbitals are chosen as three-dimensional harmonic oscillators, and we discuss a class of exact solutions that can be obtained when a subset of single-particle basis states is restricted to include a certain number of orbital excitations. The general problem, which includes all possible orbital states, can also be solved by combining analytical and numerical methods.
ERIC Educational Resources Information Center
Dakin, James T.
1974-01-01
Reviews theoretical principles underlying the quark model. Indicates that the agreement with experimental results and the understanding of the quark-quark force are two hurdles for the model to survive in the future. (CC)
Understanding complex chiral plasmonics.
Duan, Xiaoyang; Yue, Song; Liu, Na
2015-11-01
Chiral nanoplasmonics exhibits great potential for novel nanooptical devices due to the generation of a strong chiroptical response within nanoscale metallic structures. Recently, a number of different approaches have been utilized to create chiral nanoplasmonic structures. However, particularly for tailoring nanooptical chiral sensing devices, the understanding of the resulting chiroptical response when coupling chiral and achiral structures together is crucial and has not been completely understood to date. Here, we present a thorough and step-by-step experimental study to understand the intriguing chiral-achiral coupling scheme. We set up a hybrid plasmonic system, which bears resemblance to the 'host-guest' system in supramolecular chemistry to analyze and explain the complex chiral response both at the chiral and achiral plasmonic resonances. We also provide an elegant and simple analytical model, which can describe, predict, and comprehend the chiroptical spectra in detail. Our study will shed light on designing well-controlled chiral-achiral coupling platforms for reliable chiral sensing.
Weak decays of the B c meson to B s and B mesonsin the relativistic quark model
NASA Astrophysics Data System (ADS)
Ebert, D.; Faustov, R. N.; Galkin, V. O.
2003-12-01
Semileptonic and non-leptonic decays of the B c meson to B s and B mesons, caused by the cto s,d quark transitions, are studied in the framework of the relativistic quark model. The heavy quark expansion in inverse powers of the active c and spectator bar b quark is used to simplify calculations while the final s and d quarks in the B s and B mesons are treated relativistically. The decay form factors are explicitly expressed through the overlap integrals of the meson wave functions in the whole accessible kinematical range. The obtained results are compared with the predictions of other approaches.
Unified Dark Matter and Dark Energy Description in a Chiral Cosmological Model
NASA Astrophysics Data System (ADS)
Abbyazov, Renat R.; Chervon, Sergey V.
2013-03-01
We show the way of dark matter and dark energy presentation via ansatzs on the kinetic energies of the fields in the two-component chiral cosmological model (CCM). To connect a kinetic interaction of dark matter and dark energy with observational data the reconstruction procedure for the chiral metric component h22 and the potential of (self-)interaction V has been developed. The reconstruction of h22 and V for the early and later inflation have been performed. The proposed model is confronted to ΛCDM model as well.
Introduction to chiral symmetry
Koch, V.
1996-01-08
These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. Effective chiral models such as the linear and nonlinear sigma model will be discussed as well as the essential ideas of chiral perturbation theory. Some applications to the physics of ultrarelativistic heavy ion collisions will be presented.
Modelling the nucleation and chirality selection of carbon nanotubes.
Li, L; Reich, S; Robertson, J
2006-05-01
The selection of chiralities of single-walled carbon nanotubes is one of the key problems of nanotube science. We suggest that the chirality-selective growth of SWNTs could be achieved using chemical vapour deposition (CVD) by controlling the type of caps that form during the nucleation stage. As the catalyst can be solid during CVD, the formation of particular caps may be favoured by an epitaxial relationship to the catalyst surface. The corresponding tubes would then grow preferentially. We show by ab-initio calculations that the formation energy of some lattice-matched caps and tubes are 1-2 eV lower than the non lattice-matched structures.
Tong, Shengqiang; Shen, Mangmang; Xiong, Qing; Wang, Xiaoping; Lu, Mengxia; Yan, Jizhong
2016-05-20
The equilibrium model in enantioseparation of mandelic acid by chiral ligand exchange countercurrent chromatography was investigated using N-n-dodecyl-l-proline as chiral ligand and cupric ion as central metal. Important parameters, including physical partition coefficient and formation constants of binary and ternary coordination complexes in the two-phase solvent system, were determined. This equilibrium model could give an excellent prediction of distribution ratio and enantioseparation factor of the analyte in the biphasic solvent system, which was further verified by experiments. All the average relative deviations were less than 12%, indicating that the established model could provide a simple computational approach for optimization of enantioseparation conditions in chiral ligand exchange countercurrent chromatography.
Phase transition and critical behavior of d=3 chiral fermion models with left-right asymmetry
Gies, Holger; Janssen, Lukas; Rechenberger, Stefan; Scherer, Michael M.
2010-01-15
We investigate the critical behavior of three-dimensional relativistic fermion models with a U(N{sub L}){sub L} x U(1){sub R} chiral symmetry reminiscent of the Higgs-Yukawa sector of the standard model of particle physics. We classify all possible four-fermion interaction terms and the corresponding discrete symmetries. For sufficiently strong correlations in a scalar parity-conserving channel, the system can undergo a second-order phase transition to a chiral-symmetry broken phase, which is a 3d analog of the electroweak phase transition. We determine the critical behavior of this phase transition in terms of the critical exponent {nu} and the fermion and scalar anomalous dimensions for N{sub L{>=}}1. Our models define new universality classes that can serve as prototypes for studies of strongly correlated chiral fermions.
Axial form factors of the octet baryons in a covariant quark model
NASA Astrophysics Data System (ADS)
Ramalho, G.; Tsushima, K.
2016-07-01
We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q2. In our model the axial form factors GA(Q2) (axial-vector form factor) and GP(Q2) (induced pseudoscalar form factor) are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor gAq(Q2), and the induced pseudoscalar form factor gPq(Q2). The baryon wave functions are composed of a dominant S -state and a P -state mixture for the relative angular momentum of the quarks. First, we study in detail the nucleon case. We assume that the quark axial-vector form factor gAq(Q2) has the same function form as that of the quark electromagnetic isovector form factor. The remaining parameters of the model, the P -state mixture and the Q2 dependence of gPq(Q2), are determined by a fit to the nucleon axial form factor data obtained by lattice QCD simulations with large pion masses. In this lattice QCD regime the meson cloud effects are small, and the physics associated with the valence quarks can be better calibrated. Once the valence quark model is calibrated, we extend the model to the physical regime and use the low Q2 experimental data to estimate the meson cloud contributions for GA(Q2) and GP(Q2). Using the calibrated quark axial form factors and the generalization of the nucleon wave function for the other octet baryon members, we make predictions for all the possible weak interaction axial form factors GA(Q2) and GP(Q2) of the octet baryons. The results are compared with the corresponding experimental data for GA(0 ) and with the estimates of baryon-meson models based on S U (6 ) symmetry.
Some aspects of the chiral Potts model and the Ising model
NASA Astrophysics Data System (ADS)
Jin, Bai-Qi
Scope and method of study. In this thesis, we study two-dimensional statistical physics models. In the first three chapters, the 3-state chiral Potts model is used to study the question of the existence of a Lifshitz point and its related phase transitions. After an introduction in Chapter 1, the mean-field transfer matrix method with effective field determined by Bogoliubov's variational inequality is used to explore the phase diagram of this model in Chapter 2. In Chapter 3, we study this problem by the mean-field transfer matrix method with Weiss- and Bethe-type mean-field approximations respectively, and analyze the nature of the phase transition with the coherent anomaly method. Chapters 4 and 5 are contributions to the study of the Z-invariant Icing model and the quasi periodic Icing model. In Chapter 6, functional relations are used for the calculation of the exact free energy of the integrable chiral Potts model. Findings and conclusions. Our numerical studies indicate that possibly no Lifshitz point exists at finite chirality in the 3-state chiral Potts model. This result is in contrast with many other numerical studies. Furthermore, the coherent anomaly behaviors are examined in these mean-field transfer matrix approximations. Although the coherent anomaly method does give some interesting indications, we find that either much larger systems or some exact information are necessary for us to make a definite conclusion about the nature of the phase transitions in this model. In Chapter 4, the scaling form of the correlation function in the inhomogeneous Z-invariant Icing model is presented and it is applied to the study of quasi-periodic Icing models in Chapter 5. The results provide evidence that the ferromagnetic quasi-periodic Icing model with different strengths of interactions is not much different from the regular Icing model but significantly different---in its wavevector-dependent susceptibility pattern---from the case with both ferro- and
Intrinsic transverse momentum and parton correlations from dynamical chiral symmetry breaking
Peter Schweitzer, Mark Strikman, Christian Weiss
2013-01-01
The dynamical breaking of chiral symmetry in QCD is caused by nonperturbative interactions on a distance scale rho ~ 0.3 fm, much smaller than the typical hadronic size R ~ 1 fm. These short-distance interactions influence the intrinsic transverse momentum distributions of partons and their correlations at a low normalization point. We study this phenomenon in an effective description of the low-energy dynamics in terms of chiral constituent quark degrees of freedom, which refers to the large-N_c limit of QCD. The nucleon is obtained as a system of constituent quarks and antiquarks moving in a self-consistent classical chiral field (relativistic mean-field approximation, or chiral quark-soliton model). The calculated transverse momentum distributions of constituent quarks and antiquarks are matched with QCD quarks, antiquarks and gluons at the chiral symmetry--breaking scale rho^{-2}. We find that the transverse momentum distribution of valence quarks is localized at p_T^2 ~ R^{-2} and roughly of Gaussian shape. The distribution of unpolarized sea quarks exhibits a would-be power-like tail ~1/p_T^2 extending up to the chiral symmetry-breaking scale. Similar behavior is observed in the flavor-nonsinglet polarized sea. The high-momentum tails are the result of short-range correlations between sea quarks in the nucleon's light-cone wave function, which are analogous to short-range NN correlations in nuclei. We show that the nucleon's light-cone wave function contains correlated pairs of transverse size rho << R with scalar-isoscalar (Sigma) and pseudoscalar-isovector (Pi) quantum numbers, whose internal wave functions have a distinctive spin structure and become identical at p_T^2 ~ rho^{-2} (restoration of chiral symmetry). These features are model-independent and represent an effect of dynamical chiral symmetry breaking on the nucleon's partonic structure. Our results have numerous implications for the transverse momentum distributions of particles produced in hard
STRANGE GOINGS ON IN QUARK MATTER.
SCHAFER,T.
2001-06-05
We review recent work on how the superfluid state of three flavor quark matter is affected by non-zero quark masses and chemical potentials. The study of hadronic matter at high baryon density has recently attracted a lot of interest. At zero baryon density chiral symmetry is broken by a quark-anti-quark condensate. At high density condensation in the quark-anti-quark channel is suppressed. Instead, attractive interactions in the color anti-symmetric quark-quark channel favor the formation of diquark condensates. As a consequence, cold dense quark matter is expected to be a color superconductor. The symmetry breaking pattern depends on the density, the number of quark flavors, and their masses. A particularly symmetric phase is the color-flavor-locked (CFL) phase of three flavor quark matter. This phase is believed to be the true ground state of ordinary matter at very large density.
rule, and in and models with FCNC quark couplings
NASA Astrophysics Data System (ADS)
Buras, Andrzej J.; De Fazio, Fulvia; Girrbach, Jennifer
2014-07-01
The experimental value for the isospin amplitude in decays has been successfully explained within the standard model (SM), both within the large approach to QCD and by QCD lattice calculations. On the other hand within the large approach the value of is by at least below the data. While this deficit could be the result of theoretical uncertainties in this approach and could be removed by future precise QCD lattice calculations, it cannot be excluded that the missing piece in comes from new physics (NP). We demonstrate that this deficit can be significantly softened by tree-level FCNC transitions mediated by a heavy colourless gauge boson with a flavour-violating left-handed coupling and an approximately universal flavour diagonal right-handed coupling to the quarks. The approximate flavour universality of the latter coupling assures negligible NP contributions to . This property, together with the breakdown of the GIM mechanisms at tree level, allows one to enhance significantly the contribution of the leading QCD-penguin operator to . A large fraction of the missing piece in the rule can be explained in this manner for in the reach of the LHC, while satisfying the constraints from , , , LEP-II and the LHC. The presence of a small right-handed flavour-violating coupling and of enhanced matrix elements of left-right operators allows one to satisfy simultaneously the constraints from and , although this requires some fine-tuning. We identify the quartic correlation between contributions to , , and . The tests of this proposal will require much improved evaluations of and within the SM, of as well as precise tree-level determinations of and . We present correlations between , and with and without the rule constraint and generalise the whole analysis to with colour () and with FCNC couplings. In the latter case no improvement on can be achieved without destroying the agreement of the SM with the data on . Moreover, this scenario is very tightly constrained by . On the
Accidental symmetries and massless quarks in the economical 3-3-1 model
NASA Astrophysics Data System (ADS)
Montero, J. C.; Sánchez-Vega, B. L.
2015-02-01
In the framework of a 3-3-1 model with a minimal scalar sector, known as the economical 3-3-1 model, we study its capabilities of generating realistic quark masses. After a detailed study of the symmetries of the model, before and after the spontaneous symmetry breaking, we find a remaining axial symmetry that prevents some quarks from gaining mass at all orders in perturbation theory. Since this accidental symmetry is anomalous, we also consider briefly the possibility of generating their masses for nonperturbative effects. However, we find that nonperturbative effects are not enough to generate the measured masses for the three massless quarks. Hence, these results imply that the economical 3-3-1 model is not a realistic description of the electroweak interaction.
Comparison of models of critical opacity in the quark-gluon plasma
Li Xiangdong; Shakin, C.M.
2004-12-01
In this work we discuss two methods of calculation of quark propagation in the quark-gluon plasma. Both methods make use of the Nambu-Jona-Lasinio model. The essential difference of these calculations is the treatment of deconfinement. A model of confinement is not included in the work of Gastineau, Blanquier, and Aichelin (e-print hep-ph/0404207), however, the meson states they consider are still bound for temperatures greater than the deconfinement temperature T{sub c}. On the other hand, our model deals with unconfined quarks and includes a description of the qq resonances found in lattice QCD studies that make use of the maximum entropy method. We compare the qq cross sections calculated in these models.
Effects of quark matter and color superconductivity in compact stars
NASA Astrophysics Data System (ADS)
Blaschke, D.; Grigorian, H.; Aguilera, D. N.; Yasui, S.; Toki, H.
2003-04-01
The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the form factors of the interaction on the phase diagram of quark matter under the condition of β- equilibrium and charge neutrality. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state. We calculate the quark star configurations by solving the Tolman- Oppenheimer- Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ΔMc2 ~ 1053 erg. We study the consequences of antineutrino trapping in hot quark matter for quark star configurations with possible diquark condensation and discuss the claim that this energy could serve as an engine for explosive phenomena. A ``phase diagram'' for rotating compact stars (angular velocity-baryon mass plane) is suggested as a heuristic tool for obtaining constraints on the equation of state of QCD at high densities. It has a critical line dividing hadronic from quark core stars which is correlated with a local maximum of the moment of inertia and can thus be subject to experimental verification by observation of the rotational behavior of accreting compact stars.
NASA Astrophysics Data System (ADS)
Liu, Yizhuang; Nowak, Maciej A.; Zahed, Ismail
2016-08-01
We derive an exact formula for the stochastic evolution of the characteristic determinant of a class of deformed Wishart matrices following from a chiral random matrix model of QCD at finite chemical potential. In the WKB approximation, the characteristic determinant describes a sharp droplet of eigenvalues that deforms and expands at large stochastic times. Beyond the WKB limit, the edges of the droplet are fuzzy and described by universal edge functions. At the chiral point, the characteristic determinant in the microscopic limit is universal. Remarkably, the physical chiral condensate at finite chemical potential may be extracted from current and quenched lattice Dirac spectra using the universal edge scaling laws, without having to solve the QCD sign problem.
Dynamical chiral symmetry breaking in the NJL model with a constant external magnetic field
NASA Astrophysics Data System (ADS)
Shi, Song; Yang, You-Chang; Xia, Yong-Hui; Cui, Zhu-Fang; Liu, Xiao-Jun; Zong, Hong-Shi
2015-02-01
In this paper, we develop a new method that is different from the Schwinger proper time method to deduce the fermion propagator with a constant external magnetic field. In the NJL model, we use this method to find the gap equation at zero and nonzero temperature and give the numerical results and phase diagram between the magnetic field and temperature. Additionally, we introduce the current mass to study the susceptibilities because there is a new parameter (the strength of the external magnetic field) in this problem. Corresponding to this new parameter, we define a new susceptibility χB to compare with the other two susceptibilities χc (chiral susceptibility) and χT (thermal susceptibility). All three susceptibilities show that when the current mass is not zero, the phase transition is a crossover, while for comparison, in the chiral limit, the susceptibilities show a second order phase transition. Last, we give the critical coefficients of different susceptibilities in the chiral limit.
{rho}-{omega} mixing self-energy and model quark-gluon dynamics
Roberts, C.D.; Mitchell, K.L.; Tandy, P.C.; Cahill, R.T.
1995-08-01
The u-d quark-loop vacuum polarization process that mixes the {omega} and {rho} mesons and its contribution to the Charge-Symmetry-Breaking (CSB) piece of the nucleon-nucleon (NN) interaction has been studied in a QCD-based, model field theory: the Global Color-symmetry Model (GCM), using a confining quark propagator obtained in earlier studies. In fitting NN phase shifts it was found necessary to include a term in the NN potential that has, conventionally, been attributed to the mixing between {omega} and {rho} mesons that arises because of isospin asymmetry at the quark level, as manifest in the small u-d current-quark-mass difference. To the present, this term was modeled and assumed to be momentum independent. It is important to understand this term in the context of QCD. The results of this study indicate that the modification of the meson propagators produced by the quark loop is alone not sufficient to account for the observed charge symmetry breaking effects in the NN interaction. We are exploring other possible mechanisms which may describe the origin of CSB in the NN interaction.
Pion Form Factor in Chiral Limit of Hard-Wall AdS/QCD Model
Anatoly Radyushkin; Hovhannes Grigoryan
2007-12-01
We develop a formalism to calculate form factor and charge density distribution of pion in the chiral limit using the holographic dual model of QCD with hard-wall cutoff. We introduce two conjugate pion wave functions and present analytic expressions for these functions and for the pion form factor. They allow to relate such observables as the pion decay constant and the pion charge electric radius to the values of chiral condensate and hard-wall cutoff scale. The evolution of the pion form factor to large values of the momentum transfer is discussed, and results are compared to existing experimental data.
Isospin breaking and chiral symmetry restoration
Gomez Nicola, A.; Torres Andres, R.
2011-04-01
We analyze quark condensates and chiral (scalar) susceptibilities including isospin-breaking effects at finite temperature T. These include m{sub u{ne}}m{sub d} contributions as well as electromagnetic (e{ne}0) corrections, both treated in a consistent chiral Lagrangian framework to leading order in SU(2) and SU(3) chiral perturbation theory, so that our predictions are model-independent. The chiral restoration temperature extracted from
Babukhadia, L.; Berdnikov, Ya. A.; Ivanov, A. N.; Scadron, M. D.
2000-08-01
We demonstrate how a chiral soft pion theorem (SPT) shields the scalar meson ground-state isoscalar {sigma}(600-700) and isospinor {kappa}(800-900) from detection in a{sub 1}{yields}{pi}({pi}{pi}){sub swave}, {gamma}{gamma}{yields}2{pi}{sup 0}, {pi}{sup -}p{yields}{pi}{sup -}{pi}{sup +}n and K{sup -}p{yields}K{sup -}{pi}{sup +}n processes. While pseudoscalar meson PVV transitions are known to be determined by (only) quark loop diagrams, the above SPT also constrains scalar meson SVV transitions to be governed (only) by meson loop diagrams. We apply this latter SVV theorem to a{sub 0}{yields}{gamma}{gamma} and f{sub 0}{yields}{gamma}{gamma} decays. (c) 2000 The American Physical Society.
New quark-model calculations of photo-and electroproduction of N* and and Delta * resonances
Capstick, Simon
1992-06-01
An introduction is given to the calculation of resonance electromagnetic coupling in the nonrelativistic quark model. Recent improvements brought about by the inclusion of relativistic corrections to the transition operator are described. We show how such calculations may be further improved by the use of relativized-model wave functions, a modestly increased effective quark mass, and an ab initio calculation of the signs of the N-pidecay amplitudes of the resonances. A summary is given of the results for the photocouplings of all nonstrage baryons, as well as for certain amplitude ratios in electroproduction.
Quantum chromodynamic quark model study of hadron and few hadron systems
Ji, Chueng-Ryong.
1990-10-01
This report details research progress and results obtained during the five month period July 1, 1990 to November 30, 1990. The research project, entitled Quantum Chromodynamic Quark Model Study of Hadron and Few Hadron Systems,'' is supported by grant FG05-90ER40589 between North Carolina State University and the United States Department of Energy. This is a research program addressing theoretical investigations of hadron structure and reactions using quantum chromodynamic quark models. The new, significant research results are briefly summarized in the following sections.
A Petal-type Chiral NADH Model: Design, Synthesis and its Asymmetric Reduction
Bai, Cui-Bing; Wang, Nai-Xing; Wang, Yan-Jing; Xing, Yalan; Zhang, Wei; Lan, Xing-Wang
2015-01-01
A new type of NADH model compound has been synthesized by an efficient and convenient method. This model compound exhibits high reactivity and enantioselectivity in asymmetric reduction reactions. The results show that chiral NADH model S could be effectively combined with Mg2+ to form ternary complexes. This novel C3 symmetrical NADH model is capable of fluorescence emission at 460 nm when excited at 377 nm. PMID:26648413
Quark-lepton mass relation in a realistic A4 extension of the Standard Model
NASA Astrophysics Data System (ADS)
King, S. F.; Morisi, S.; Peinado, E.; Valle, J. W. F.
2013-07-01
We propose a realistic A4 extension of the Standard Model involving a particular quark-lepton mass relation, namely that the ratio of the third family mass to the geometric mean of the first and second family masses are equal for down-type quarks and charged leptons. This relation, which is approximately renormalization group invariant, is usually regarded as arising from the Georgi-Jarlskog relations, but in the present model there is no unification group or supersymmetry. In the neutrino sector we propose a simple modification of the so-called Zee-Wolfenstein mass matrix pattern which allows an acceptable reactor angle along with a deviation of the atmospheric and solar angles from their bi-maximal values. Quark masses, mixing angles and CP violation are well described by a numerical fit.
Realization of chiral symmetry breaking and restoration in holographic QCD
NASA Astrophysics Data System (ADS)
Chelabi, Kaddour; Fang, Zhen; Huang, Mei; Li, Danning; Wu, Yue-Liang
2016-05-01
With proper profiles of the scalar potential and the dilaton field, for the first time, the spontaneous chiral symmetry breaking in the vacuum and its restoration at finite temperature are correctly realized in the holographic QCD framework. In the chiral limit, a nonzero chiral condensate develops in the vacuum and decreases with temperature, and the phase transition is of the second order for a two-flavor case and of the first order for a three-flavor case. In the case of explicit chiral symmetry breaking, in the two-flavor case, the second-order phase transition turns into a crossover with any nonzero current quark mass, and in the three-flavor case, the first-order phase transition turns into a crossover at a finite current quark mass. The correct description of chiral symmetry breaking and restoration makes the holographic QCD models more powerful in dealing with nonperturbative QCD phenomena. This framework can be regarded as a general setup in an application of AdS/CFT to describe conventional Ginzburg-Landau-Wilson-type phase transitions, e.g. in condensed matter and cosmology systems.
Zheng Xiaoping; Liu Xuewen; Kang Miao; Yang Shuhua
2004-07-01
We study the bulk viscosity of the strange quark matter in the density-dependent quark mass model (DDQM) under the background of self-consistent thermodynamics. The correct formula of the viscosity is derived. We also find that the viscosity in the DDQM is larger by two to three orders of magnitude than that in MIT bag model. We calculate the damping time scale due to the coupling of the viscosity and r mode. The numerical results show that the time scale cannot be shorter than 10{sup -1} s.
CSOS models descending from chiral Potts models: degeneracy of the eigenspace and loop algebra
NASA Astrophysics Data System (ADS)
Au-Yang, Helen; Perk, Jacques H. H.
2016-04-01
Monodromy matrices of the {{\\boldsymbol{τ }}}2\\phantom{^{\\prime }} model are known to satisfy a Yang-Baxter equation with a six-vertex R-matrix as the intertwiner. The commutation relations of the elements of the monodromy matrices are completely determined by this R-matrix. We show the reason why in the superintegrable case the eigenspace is degenerate, but not in the general case. We then show that the eigenspaces of special CSOS models descending from the chiral Potts model are also degenerate. The existence of an L({{sl}}2) quantum loop algebra (or subalgebra) in these models is established by showing that the Serre relations hold for the generators. The highest weight polynomial (or the Drinfeld polynomial) of the representation is obtained by using the method of Baxter for the superintegrable case. As a byproduct, the eigenvalues of all such CSOS models are given explicitly.
X(5568) as a {su}\\bar{d}\\bar{b} tetraquark in a simple quark model
NASA Astrophysics Data System (ADS)
Stancu, Fl
2016-10-01
The S-wave eigenstates of tetraquarks of type {su}\\bar{d}\\bar{b} with J P = 0+, 1+ and 2+ are studied within a simple quark model with chromomagnetic interaction and effective quark masses extracted from meson and baryon spectra. It is tempting to see if this spectrum can accommodate the new narrow structure X(5568), observed by the DØ Collaboration, but not confirmed by the LHCb Collaboration. If it exists, such a tetraquark is a system with four different flavors and its study can improve our understanding of multiquark systems. The presently calculated mass of X(5568) agrees quite well with the experimental value of the DØ Collaboration. Predictions are also made for the spectrum of the charmed partner {su}\\bar{d}\\bar{c}. However we are aware of the difficulty of extracting effective quark masses, from mesons and baryons, to be used in multiquark systems.
The Quark-Deconfinement Nova model for Gamma-Ray Bursts
Bombaci, I.
2005-10-21
We report on a new model which is able to explain how a gamma-ray burst (GRB) can take place days or years after a supernova explosion. We show that above a threshold value of the gravitational mass a pure hadronic star ('neutron star') is metastable to the conversion into a quark star (hybrid star or strange star), i.e. a star made at least in part of deconfined quark matter. The stellar conversion process can be delayed if finite size effects at the interface between hadronic and deconfined quark matter phases are taken into account. A huge amount of energy, on the order of 1052 - 1053 ergs, is released during the conversion process and can produce a powerful gamma-ray burst. The delay between the supernova explosion generating the metastable neutron star and the new collapse can explain the delay inferred in GRB 990705 and in GRB 011211.
Aaltonen, T.; Adelman, Jahred A.; Akimoto, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, Dante E.; Anastassov, A.; Annovi, Alberto; Antos, Jaroslav; Apollinari, G.; Apresyan, A.; /Purdue U. /Waseda U.
2009-06-01
In a search for new phenomena in a signature suppressed in the standard model of elementary particles (SM), we compare the inclusive production of events containing a lepton ({ell}), a photon ({gamma}), significant transverse momentum imbalance (E{sub T}), and a jet identified as containing a b-quark, to SM predictions. The search uses data produced in proton-antiproton collisions at {radical}s = 1.96 TeV corresponding to 1.9 fb{sup -1} of integrated luminosity taken with the CDF detector at the Fermilab Tevatron. We find 28 {ell}{gamma}bE{sub T} events versus an expectation of 31.0{sub -3.5}{sup +4.1} events. If we further require events to contain at least three jets and large total transverse energy, simulations predict that the largest SM source is top-quark pair production with an additional radiated photon, t{bar t} + {gamma}. In the data we observe 16 t{bar t}{gamma} candidate events versus an expectation from non-top-quark SM sources of 11.2{sub -2.1}{sup +2.3}. Assuming the difference between the observed number and the predicted non-top-quark total is due to SM top quark production, we estimate the t{bar t} cross section to be 0.15 {+-} 0.08 pb.
The 3P0-VERSUS 3S1-MODELS for Quark-Antiquark Annihilation
NASA Astrophysics Data System (ADS)
Green, A. M.; Niskanen, J. A.
A comparison is made between the 3S1- and 3P0-models for quark-antiquark annihilation or creation. Even though the former appears, at first sight, to be superior for Nbar {N} annihilation into two mesons, it is argued from their effects in meson decays that this conclusion is premature.
Frederico, T.; Pace, E.; Pasquini, B.; Salme, G.
2010-08-05
Longitudinal and transverse parton distributions for pion and nucleon are calculated from hadron vertexes obtained by a study of form factors within relativistic quark models. The relevance of the one-gluon-exchange dominance at short range for the behavior of the form factors at large momentum transfer and of the parton distributions at the end points is stressed.
SU(2) Higher-order effective quark interactions from polarization
NASA Astrophysics Data System (ADS)
Braghin, Fábio L.
2016-10-01
Higher order quark effective interactions are found for SU(2) flavor by departing from a non-local quark-quark interaction. By integrating out a component of the quark field, the determinant is expanded in chirally symmetric and symmetry breaking effective interactions up to the fifth order in the quark bilinears. The resulting coupling constants are resolved in the leading order of the longwavelength limit and exact numerical ratios between several of these coupling constants are obtained in the large quark mass limit. In this level, chiral invariant interactions only show up in even powers of the quark bilinears, i.e. O(ψ bar ψ) 2 n (n = 1 , 2 , 3 , . .), whereas (explicit) chiral symmetry breaking terms emerge as O(ψ bar ψ) n being always proportional to some power of the Lagrangian quark mass.
Chiral symmetry and π-π scattering in the Covariant Spectator Theory
Biernat, Elmar P.; Peña, M. T.; Ribeiro, J. E.; Stadler, Alfred; Gross, Franz
2014-11-14
The π-π scattering amplitude calculated with a model for the quark-antiquark interaction in the framework of the Covariant Spectator Theory (CST) is shown to satisfy the Adler zero constraint imposed by chiral symmetry. The CST formalism is established in Minkowski space and our calculations are performed in momentum space. We prove that the axial-vector Ward-Takahashi identity is satisfied by our model. Then we show that, similarly to what happens within the Bethe-Salpeter formalism, application of the axial-vector Ward Takahashi identity to the CST π-π scattering amplitude allows us to sum the intermediate quark-quark interactions to all orders. Thus, the Adlermore » self-consistency zero for π-π scattering in the chiral limit emerges as the result for this sum.« less
Highly nonlinear wave solutions in a dual to the chiral model
NASA Astrophysics Data System (ADS)
Rajeev, S. G.; Ranken, Evan
2016-05-01
We consider a two-dimensional scalar field theory with a nilpotent current algebra, which is dual to the Principal Chiral Model. The quantum theory is renormalizable and not asymptotically free; the theory is strongly coupled at short distances (encountering a Landau pole). We suggest it can serve as a toy model for λ ϕ4 theory in four dimensions, just as the principal chiral model is a useful toy model for Yang-Mills theory. We find some classical wave solutions that survive the strong coupling limit and quantize them by the collective variable method. They describe excitations with an unusual dispersion relation ω ∝|k |2/3 . Perhaps they are the "preons" at strong coupling, the bound states of which form massless particles over long distances.
Bahrami, M; Donadi, S; Ferialdi, L; Bassi, A; Curceanu, C; Di Domenico, A; Hiesmayr, B C
2013-01-01
Collapse models provide a theoretical framework for understanding how classical world emerges from quantum mechanics. Their dynamics preserves (practically) quantum linearity for microscopic systems, while it becomes strongly nonlinear when moving towards macroscopic scale. The conventional approach to test collapse models is to create spatial superpositions of mesoscopic systems and then examine the loss of interference, while environmental noises are engineered carefully. Here we investigate a different approach: We study systems that naturally oscillate-creating quantum superpositions-and thus represent a natural case-study for testing quantum linearity: neutrinos, neutral mesons, and chiral molecules. We will show how spontaneous collapses affect their oscillatory behavior, and will compare them with environmental decoherence effects. We will show that, contrary to what previously predicted, collapse models cannot be tested with neutrinos. The effect is stronger for neutral mesons, but still beyond experimental reach. Instead, chiral molecules can offer promising candidates for testing collapse models.
Branz, Tanja; Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E.; Oexl, Bettina; Ivanov, Mikhail A.; Koerner, Juergen G.
2010-06-01
We study flavor-conserving radiative decays of double-heavy baryons using a manifestly Lorentz covariant constituent three-quark model. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit. We discuss in some detail hyperfine mixing effects.
Quark masses and their hierarchies
NASA Astrophysics Data System (ADS)
Ida, M.
1987-12-01
Electroweak symmetry breaking is attributed to dynamical generation of quark masses. Quarks q (and leptons l) are assumed to be produced by hypercolor confinement of preons at an intermediate scale Λ hc. Hierarchies observed in the q mass spectra can be explained by a BCS mechanism if the color interaction is enough asymptotically free and if residual ones emerging by the confinement are medium strong. The former assumption claims that N≦4, where N is the family number of q and l. Dynamical equations to determine q masses and mixings are given, but they require knowledge on the physics at Λ hc. A phenomenological approach is also made on the basis of an SU(7)× SU(7) chiral preon model with N=4. The mass ratio m t/ mb is related to ( m c/ m s)ηB with η B≃1.1 and m t'/ mb' to ( m u/ m d)ηA with η A≃1.4. In this scheme the fourth down quark is the heaviest (˜ 110 GeV) and contributes dominantly to F 2, where F is the Fermi scale.
ISO(2,1) chiral models and quantum gravity in 2 + 1 dimensions
NASA Astrophysics Data System (ADS)
Salomonson, P.; Skagerstam, B.-S.; Stern, A.
1990-12-01
We study gravity in 2 + 1 dimensions on the manifold M = D 2 × ℝ. A specific choice of boundary conditions leads to an equivalence of the system with a chiral Wess-Zumino-Novikov-Witten model associated with the group ISO(2,1). The model is written on the boundary S 1 × ℝ of M. We find induced representations of the corresponding Kac-Moody and Virasoro algebras with zero Virasoro anomaly.
SPECTRAL PROPERTIES OF QUARKS IN THE QUARK-GLUON PLASMA.
KARSCH,F.; KITAZAWA, M.
2007-07-30
We analyze the spectral properties of the quark propagator above the critical temperature for the deconfinement phase transition in quenched lattice QCD using clover improved Wilson fermions. The bare quark mass dependence of the quark spectral function is analyzed by varying the hopping parameter {kappa} in Landau gauge. We assume a two-pole structure for the quark spectral function, which is numerically found to work quite well for any value of {kappa}. It is shown that in the chiral limit the quark spectral function has two collective modes that correspond to the normal and plasmino excitations, while it is dominated by a single-pole structure when the bare quark mass becomes large.
Chiral and deconfinement transition from Dyson-Schwinger equations
Fischer, Christian S.; Mueller, Jens A.
2009-10-01
We determine the quark condensate and the dressed Polyakov loop from the finite temperature Landau gauge quark propagator evaluated with U(1)-valued boundary conditions in an approximation to quenched QCD. These gauge invariant quantities allow for an investigation of the chiral and deconfinement transitions. We compare results from Dyson-Schwinger equations on a lattice with infinite volume continuum results and study the temperature and quark mass dependence of both quantities. In particular we investigate the chiral condensate and the dressed Polyakov loop in the chiral limit. We also consider an alternative order parameter for the deconfinement transition, the dual scalar quark dressing, and compare it with the dressed Polyakov loop. As a result we find only slightly different transition temperatures for the chiral and the deconfinement transitions at finite quark masses; in the chiral limit both transitions coincide.
Exclusive Rare B ( s, c) Decays in Light-Front Quark Model
NASA Astrophysics Data System (ADS)
Choi, Ho-Meoyng
2013-03-01
We investigate the exclusive rare {B_sto (K,η^{(')})(ν_{ell}bar{ν_{ell}}, ell^+ell^-)} and {B_cto D_{(s)}(ν_{ell}bar{ν_{ell}}, ell^+ell^-)} ( ℓ = e, μ, τ) decays within the standard model and the light-front quark model constrained by the variational principle for the QCD motivated effective Hamiltonian. The branching ratios and the longitudinal lepton polarization asymmetries are calculated and compared with other theoretical model predictions.
Explanation of the masses of quarks and leptons in a supersymmetric preon model
NASA Astrophysics Data System (ADS)
Kim, Jongbae
1998-10-01
We have studied whether the radiative effects including gauge and Yukawa interaction corrections can improve the phenomenological consequences on the masses of quarks and leptons in the supersymmetric preon model. Our study shows that pure renormalization effects in the region from the metacolour scale to the electroweak scale produce quark-lepton distinction within a given family. They cannot, however, produce the desired up-down distinction or the expected quark-lepton asymmetry in the effective hierarchy parameter 0954-3899/24/10/006/img1 of the up, down and lepton sectors. It also shows that the pure radiative corrections cannot explain the `fine structure' effects exhibited by 0954-3899/24/10/006/img2. These lead us to conclude that the symmetry structure of the preon theory cannot strictly respect left-right, up-down and quark-lepton symmetries near and below the Planck scale. This subsequently implies the 0954-3899/24/10/006/img3 symmetry both as regards unification of couplings near the Planck scale in the model and as regards its possible origin from a superstring theory.
NASA Astrophysics Data System (ADS)
Jido, Daisuke; Sakashita, Minori
2016-08-01
The possibility of having a diquark configuration in heavy baryons, such as Λ and Λ, is examined by a nonrelativistic potential model with a heavy quark and a light scalar diquark. Assuming that the Λ and Λ baryons are composed of the heavy quark and the point-like scalar-isoscalar ud diquark, we solve the two-body Schrödinger equation with the Coulomb plus linear potential and obtain the energy spectra for the heavy baryons. Contrary to our expectation, it is found that the potential determined by the quarkonium spectra fails to reproduce the excitation spectra of the Λ and Λ in the quark-diquark picture, while the Λ and Λ spectra are reproduced with half the strength of the confinement string tension than for the quarkonium. The finite size effect of the diquark is also examined and it is found that the introduction of a finite size diquark would resolve the failure of the spectrum reproduction. The Ξ excitation energy is also calculated and is found to be smaller than Λ in the quark-diquark model. This is not consistent with experimental observations.
Anomalies and Discrete Chiral Symmetries
Creutz, M.
2009-09-07
The quantum anomaly that breaks the U(1) axial symmetry of massless multi-flavored QCD leaves behind a discrete flavor-singlet chiral invariance. With massive quarks, this residual symmetry has a close connection with the strong CP-violating parameter theta. One result is that if the lightest quarks are degenerate, then a first order transition will occur when theta passes through pi. The resulting framework helps clarify when the rooting prescription for extrapolating in the number of flavors is valid.
Chirality and Z2 vortices in a Heisenberg spin model on the kagome lattice
NASA Astrophysics Data System (ADS)
Domenge, J.-C.; Lhuillier, C.; Messio, L.; Pierre, L.; Viot, P.
2008-05-01
The phase diagram of the classical J1-J2 model on the kagome lattice is investigated by using extensive Monte Carlo simulations. In a realistic range of parameters, this model has a low-temperature chiral-ordered phase without long-range spin order. We show that the critical transition marking the destruction of the chiral order is preempted by the first-order proliferation of Z2 point defects. The core energy of these vortices appears to vanish when approaching the T=0 phase boundary, where both Z2 defects and gapless magnons contribute to disordering the system at very low temperatures. This situation might be typical of a large class of frustrated magnets. Possible relevance for real materials is also discussed.
Azcoiti, V.; Di Carlo, G.; Galante, A.; Grillo, A.F.; Laliena, V. Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati Dipartimento di Fisica dell'Universita dell'Aquila, 67100 L'Aquila )
1994-12-01
The microcanonical fermionic average method has been used so far in the context of lattice models with phase transitions at finite coupling. To test its applicability to asymptotically free theories, we have implemented it in two-dimensional QED, i.e., the Schwinger model. We exploit the possibility, intrinsic to this method, of studying the whole [beta],[ital m] plane without extra computer cost, to follow constant physics trajectories and measure the [ital m][r arrow]0 limit of the chiral condensate. We recover the continuum result within three decimal places. Moreover, the possibility, intrinsic to the method, of performing simulations directly in the chiral limit allows us to compute the average plaquette energy at [ital m]=0, the result being in perfect agreement with the expected value.
Color Confinement and Dynamical Chiral Symmetry Breaking
NASA Astrophysics Data System (ADS)
Nakamura, Naoki; Suzuki, Tsuneo
We study the relation between the quark confinement and the dynamical chiral symmetry breaking in SU(2) QCD by deriving an effective Lagrangian of a monopole field and the chiral fields from the dual Ginzburg-Landau type Lagrangian(DGL Lagrangian)…
Unexpected manifestation of quark condensation
Zinovjev, G. M.; Molodtsov, S. V.
2015-05-15
A comparative analysis of some quark ensembles governed by a four-fermion interaction is performed. Arguments in support of the statement that the presence of a gas-liquid phase transition is a feature peculiar to them are adduced. The instability of small quark droplets is discussed and is attributed to the formation of a chiral soliton. The stability of baryon matter is due to a mixed phase of the vacuum and baryon matter.
Propagation of cosmic rays through the atmosphere in the quark-gluon strings model
NASA Technical Reports Server (NTRS)
Erlykin, A. D.; Krutikova, N. P.; Shabelski, Y. M.
1985-01-01
The quark-gluon strings model succeeds in the description of multiple hadron production in the central rapidity region of nucleon-nucleon interctions. This model was developed for hadron-nucleus interactions and used for calculation of the cosmic ray propagation through the atmosphere. It is shown that at energies 10 to the 11th power to the 12th power eV, this model gives a satisfactory description of experimental data. But with the increase of the energy up to approximately 10 to the 14th power eV, results of calculations and of experiments begin to differ and this difference rises with the energy. It may indicate that the scaling violation in the fragmentation region of inclusive spectra for hadron-nucleus interactions is stronger than in the quark-gluon strings model.
Scalar-quark systems and chimera hadrons in SU(3){sub c} lattice QCD
Iida, H.; Takahashi, T. T.; Suganuma, H.
2007-06-01
In terms of mass generation in the strong interaction without chiral symmetry breaking, we perform the first study for light scalar-quarks {phi} (colored scalar particles with 3{sub c} or idealized diquarks) and their color-singlet hadronic states using quenched SU(3){sub c} lattice QCD with {beta}=5.70 (i.e., a{approx_equal}0.18 fm) and lattice size 16{sup 3}x32. We investigate ''scalar-quark mesons'' {phi}{sup {dagger}}{phi} and ''scalar-quark baryons'' {phi}{phi}{phi} as the bound states of scalar-quarks {phi}. We also investigate the color-singlet bound states of scalar-quarks {phi} and quarks {psi}, i.e., {phi}{sup {dagger}}{psi}, {psi}{psi}{phi}, and {phi}{phi}{psi}, which we name ''chimera hadrons.'' All the new-type hadrons including {phi} are found to have a large mass even for zero bare scalar-quark mass m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV. We find a ''constituent scalar-quark/quark picture'' for both scalar-quark hadrons and chimera hadrons. Namely, the mass of the new-type hadron composed of m {phi}'s and n {psi}'s, M{sub m{phi}}{sub +n{psi}}, approximately satisfies M{sub m{phi}}{sub +n{psi}}{approx_equal}mM{sub {phi}}+nM{sub {psi}}, where M{sub {phi}} and M{sub {psi}} are the constituent scalar-quark and quark masses, respectively. We estimate the constituent scalar-quark mass M{sub {phi}} for m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV as M{sub {phi}}{approx_equal}1.5-1.6 GeV, which is much larger than the constituent quark mass M{sub {psi}}{approx_equal}400 MeV in the chiral limit. Thus, scalar quarks acquire a large mass due to large quantum corrections by gluons in the systems including scalar quarks. Together with other evidences of mass generation of glueballs and charmonia, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluon effects. In addition, the large mass generation of pointlike colored scalar particles indicates that plausible diquarks used in effective hadron models cannot
NASA Astrophysics Data System (ADS)
Zamorano, M.; Torres-Silva, H.
2006-04-01
A new electrodynamics model formed by chiral bioplasma, which represents the human head inner structure and makes it possible to analyse its behaviour when it is irradiated by a microwave electromagnetic field from cellular phones, is presented. The finite-difference time-domain (FDTD) numeric technique is used, which allows simulation of the electromagnetic fields, deduced with Maxwell's equations, and allows us to simulate the specific absorption rate (SAR). The results show the SAR behaviour as a function of the input power and the chirality factor. In considering the chiral brain tissue in the proposed human head model, the two more important conclusions of our work are the following: (a) the absorption of the electromagnetic fields from cellular phones is stronger, so the SAR coefficient is higher than that using the classical model, when values of the chiral factor are of order of 1; (b) 'inverse skin effect' shows up at 1800 MHz, with respect to a 900 MHz source.
Champagne, Pier Alexandre; Houk, K N
2016-09-28
The origins of the high enantioselectivity of chiral phosphoric acid-catalyzed oxetane desymmetrizations were investigated by density functional theory (DFT) calculations. Distortion of the catalyst structure, caused by steric crowding in the catalyst pocket of one enantiomeric transition state, is the main cause for stereochemical preference. A general model was developed to assist in the rational design of new catalysts for related transformations. PMID:27629045
NASA Astrophysics Data System (ADS)
Hu, Wen-Jun; Zhu, Wei; Zhang, Yi; Gong, Shoushu; Becca, Federico; Sheng, D. N.
2015-01-01
We investigate the extended Heisenberg model on the kagome lattice by using Gutzwiller projected fermionic states and the variational Monte Carlo technique. In particular, when both second- and third-neighbor superexchanges are considered, we find that a gapped spin liquid described by nontrivial magnetic fluxes and long-range chiral-chiral correlations is energetically favored compared to the gapless U(1) Dirac state. Furthermore, the topological Chern number, obtained by integrating the Berry curvature, and the degeneracy of the ground state, by constructing linearly independent states, lead us to identify this flux state as the chiral spin liquid with a C =1 /2 fractionalized Chern number.
Some Possible Grand Unified Preon Models with Light Quarks and Leptons
NASA Astrophysics Data System (ADS)
Du, Dongsheng; Lu, Gongru
Three grand unified preon models with light quarks and leptons are presented. All these models have natural family structure at the composite level. One of them can give a very low metacolor scale, ΛMC~3×104 GeV. It is argued that the best choice for a metacolor group is SU(4) and that for a unification group it is SU(9).
Quark flavour observables in the Littlest Higgs model with T-parity after LHC Run 1
NASA Astrophysics Data System (ADS)
Blanke, Monika; Buras, Andrzej J.; Recksiegel, Stefan
2016-04-01
The Littlest Higgs model with T-parity (LHT) belongs to the simplest new physics scenarios with new sources of flavour and CP violation. The latter originate in the interactions of ordinary quarks and leptons with heavy mirror quarks and leptons that are mediated by new heavy gauge bosons. Also a heavy fermionic top partner is present in this model which communicates with the SM fermions by means of standard W^± and Z^0 gauge bosons. We present a new analysis of quark flavour observables in the LHT model in view of the oncoming flavour precision era. We use all available information on the CKM parameters, lattice QCD input and experimental data on quark flavour observables and corresponding theoretical calculations, taking into account new lower bounds on the symmetry breaking scale and the mirror quark masses from the LHC. We investigate by how much the branching ratios for a number of rare K and B decays are still allowed to depart from their SM values. This includes K^+→ π ^+ν bar{ν }, KL→ π ^0ν bar{ν }, K_L→ μ ^+μ ^-, B→ X_sγ , B_{s,d}→ μ ^+μ ^-, B→ K^{(*)}ℓ ^+ℓ ^-, B→ K^{(*)}ν bar{ν }, and \\varepsilon '/\\varepsilon . Taking into account the constraints from Δ F=2 processes, significant departures from the SM predictions for K^+→ π ^+ν bar{ν } and KL→ π ^0ν bar{ν } are possible, while the effects in B decays are much smaller. In particular, the LHT model favours B(Bs→ μ ^+μ ^-) ≥ B(Bs→ μ ^+μ ^-)_SM, which is not supported by the data, and the present anomalies in B→ K^{(*)}ℓ ^+ℓ ^- decays cannot be explained in this model. With the recent lattice and large N input the imposition of the \\varepsilon '/\\varepsilon constraint implies a significant suppression of the branching ratio for KL→ π ^0ν bar{ν } with respect to its SM value while allowing only for small modifications of K^+→ π ^+ν bar{ν }. Finally, we investigate how the LHT physics could be distinguished from other models by means of
Properties of quark matter in a new quasiparticle model with QCD running coupling
NASA Astrophysics Data System (ADS)
Lu, ZhenYan; Peng, GuangXiong; Xu, JianFeng; Zhang, ShiPeng
2016-06-01
The running of the QCD coupling in the effective mass causes thermodynamic inconsistency problem in the conventional quasiparticle model. We provide a novel treatment which removes the inconsistency by an effective bag constant. The chemical potential dependence of the renormalization subtraction point is constrained by the Cauchy condition in the chemical potential space. The stability and microscopic properties of strange quark matter are then studied within the completely self-consistent quasiparticle model, and the obtained equation of state of quark matter is applied to the investigation of strange stars. It is found that our improved model can describe well compact stars with mass about two times the solar mass, which indicates that such massive compact stars could be strange stars.
Heinson, A.P.; /UC, Riverside
2006-08-01
First observed in 1995, the top quark is one of a pair of third-generation quarks in the Standard Model of particle physics. It has charge +2/3e and a mass of 171.4 GeV, about 40 times heavier than its partner, the bottom quark. The CDF and D0 collaborations have identified several hundred events containing the decays of top-antitop pairs in the large dataset collected at the Tevatron proton-antiproton collider over the last four years. They have used these events to measure the top quark's mass to nearly 1% precision and to study other top quark properties. The mass of the top quark is a fundamental parameter of the Standard Model, and knowledge of its value with small uncertainty allows us to predict properties of the as-yet-unobserved Higgs boson. This paper presents the status of the measurements of the top quark mass.
Quark screening lengths in finite temperature QCD
Gocksch, A. California Univ., Santa Barbara, CA . Inst. for Theoretical Physics)
1990-11-01
We have computed Landau gauge quark propagators in both the confined and deconfined phase of QCD. I discuss the magnitude of the resulting screening lengths as well as aspects of chiral symmetry relevant to the quark propagator. 12 refs., 1 fig., 1 tab.
Consistent parameter fixing in the quark-meson model with vacuum fluctuations
NASA Astrophysics Data System (ADS)
Carignano, Stefano; Buballa, Michael; Elkamhawy, Wael
2016-08-01
We revisit the renormalization prescription for the quark-meson model in an extended mean-field approximation, where vacuum quark fluctuations are included. At a given cutoff scale the model parameters are fixed by fitting vacuum quantities, typically including the sigma-meson mass mσ and the pion decay constant fπ. In most publications the latter is identified with the expectation value of the sigma field, while for mσ the curvature mass is taken. When quark loops are included, this prescription is however inconsistent, and the correct identification involves the renormalized pion decay constant and the sigma pole mass. In the present article we investigate the influence of the parameter-fixing scheme on the phase structure of the model at finite temperature and chemical potential. Despite large differences between the model parameters in the two schemes, we find that in homogeneous matter the effect on the phase diagram is relatively small. For inhomogeneous phases, on the other hand, the choice of the proper renormalization prescription is crucial. In particular, we show that if renormalization effects on the pion decay constant are not considered, the model does not even present a well-defined renormalized limit when the cutoff is sent to infinity.
Uechi, Schun T.; Uechi, Hiroshi
2011-05-06
Density-dependent relations among saturation properties of symmetric nuclear matter and properties of hadronic stars are discussed by applying the conserving chiral nonlinear ({sigma},{pi},{omega}) hadronic mean-field theory. The chiral nonlinear ({sigma},{pi},{omega}) mean-field theory is an extension of the conserving nonlinear (nonchiral) {sigma}-{omega} hadronic mean-field theory which is thermodynamically consistent, relativistic and is a Lorentz-covariant mean-field theory of hadrons. In the extended chiral ({sigma},{pi},{omega}) mean-field model, all the masses of hadrons are produced by the breaking of chiral symmetry, which is different from other conventional chiral partner models. By comparing both nonchiral and chiral mean-field approximations, the effects of the chiral symmetry breaking mechanism on the mass of {sigma}-meson, coefficients of nonlinear interactions and Fermi-liquid properties are investigated in nuclear matter and neutron stars.
Cold Uniform Matter and Neutron Stars in the Quark-Meson-Coupling Model
J.R. Stone; P.A.M. Guichon; H.H. Matevosyan; A.W. Thomas
2007-08-01
A new density dependent effective baryon-baryon interaction has been recently derived from the quark-meson-coupling (QMC) model, offering impressive results in application to finite nuclei and dense baryon matter. This self-consistent, relativistic quark-level approach is used to construct the Equation of State (EoS) and to calculate key properties of high density matter and cold, slowly rotating neutron stars. The results include predictions for the maximum mass of neutron star models, together with the corresponding radius and central density, as well the properties of neutron stars with mass of order 1.4 M{sub {circle_dot}}. The cooling mechanism allowed by the QMC EoS is explored and the parameters relevant to slow rotation, namely the moment of inertia and the period of rotation investigated. The results of the calculation, which are found to be in good agreement with available observational data, are compared with the predictions of more traditional EoS, based on the A18+{delta}v+UIX* and modified Reid soft core potentials, the Skyrme SkM* interaction and two relativistic mean field (RMF) models for a hybrid stars including quark matter. The QMC EoS provides cold neutron star models with maximum mass 1.9-2.1 M{sub {circle_dot}}, with central density less than 6 times nuclear saturation density (n{sub 0} = 0.16 fm{sup -3}) and offers a consistent description of the stellar mass up to this density limit. In contrast with other models, QMC predicts no hyperon contribution at densities lower than 3n{sub 0}, for matter in {beta}-equilibrium. At higher densities, {Xi}{sup -,0} and {Lambda} hyperons are present. The absence of lighter {Sigma}{sup {+-},0} hyperons is understood as a consequence of antisymmetrization, together with the implementation of the color hyperfine interaction in the response of the quark bag to the nuclear scalar field.
Excited bottom and bottom-strange mesons in the quark model
NASA Astrophysics Data System (ADS)
Lü, Qi-Fang; Pan, Ting-Ting; Wang, Yan-Yan; Wang, En; Li, De-Min
2016-10-01
In order to understand the possible q q ¯ quark-model assignments of the BJ(5840 ) and BJ(5960 ) recently reported by the LHCb Collaboration, we evaluate mass spectra, strong decays, and radiative decays of bottom and bottom-strange mesons in a nonrelativistic quark model. Comparing these predictions with the relevant experimental results, we suggest that the BJ(5840 ) and BJ(5960 ) can be identified as the B (2 1S0) and B (1 3D3) , respectively, and the B (5970 ) reported by the CDF Collaboration can be interpreted as the B (2 3S1) or B (1 3D3) . Further precise measurements of the width, spin and decay modes of the B (5970 ) are needed to distinguish these two assignments. These predictions of bottom and bottom-strange mesons can provide useful information to further experimental investigations.
Variational Monte Carlo study of pentaquark states in a correlated quark model
Mark Paris
2005-10-25
Accurate numerical solution of the five-body Schrodinger equation is effected via variational Monte Carlo in a correlated quark model. The spectrum is assumed to exhibit a narrow resonance with strangeness $S=+1$. A fully antisymmetrized and pair-correlated five-quark wave function is obtained for the assumed non-relativistic Hamiltonian which has spin, isospin, and color dependent pair interactions and many-body confining terms which are fixed by the non-exotic spectra. Gauge field dynamics are modeled via flux tube exchange factors. The energy determined for the ground states with spin-parity 1/2- (1/2+) is 2.22 GeV (2.50 GeV). A lower energy negative parity state is consistent with recent lattice results.
Partial restoration of chiral symmetry in a confining string
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 string 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.
Phase diagram and critical end point in nonlocal PNJL models with wavefunction renormalization
Contrera, Gustavo A.; Orsaria, Milva G.; Scoccola, Norberto N.
2010-11-12
We study the chiral phase transition at finite temperature and chemical potential considering a non-local chiral quark model which includes wave-function renormalization and coupling to the Polyakov loop. In particular, we determine the position of the Critical End Point as well as the value of the associated critical exponents for different model parameterizations.
Chiral graphene nanoribbons: Objective molecular dynamics simulations and phase-transition modeling.
Akatyeva, E; Dumitrică, T
2012-12-21
There is a growing need to understand the stability of quasi-one-dimensional one-layer-thick graphene nanoribbons. Objective molecular dynamics based on density-functional tight-binding models are used to investigate the stability against torsional deformations of nanoribbons with bare, F-, and OH-decorated armchair edges. The prevalence of chiral nanoribbons, including homochiral ones, prompted the construction of a simple phenomenological model inspired from the Landau phase transition theory. Our model is based on atomistic data and gives the structural parameters of the nanoribbon as a function of its edge chemistry and axial strain.
Effective field theories of baryons and mesons, or, what do quarks do?
Keaton, G.L.
1995-06-26
This thesis is an attempt to understand the properties of the protons, pions and other hadrons in terms of their fundamental building blocks. In the first chapter the author reviews several of the approaches that have already been developed. The Nambu-Jona-Lasinio model offers the classic example of a derivation of meson properties from a quark Lagrangian. The chiral quark model encodes much of the intuition acquired in recent decades. The author also discusses the non-linear sigma model, the Skyrme model, and the constituent quark model, which is one of the oldest and most successful models. In the constituent quark model, the constituent quark appears to be different from the current quark that appears in the fundamental QCD Lagrangian. Recently it was proposed that the constituent quark is a topological soliton. In chapter 2 the author investigates this soliton, calculating its mass, radius, magnetic moment, color magnetic moment, and spin structure function. Within the approximations used, the magnetic moments and spin structure function cannot simultaneously be made to agree with the constituent quark model. In chapter 3 the author uses a different plan of attack. Rather than trying to model the constituents of the baryon, he begins with an effective field theory of baryons and mesons, with couplings and masses that are simply determined phenomenologically. Meson loop corrections to baryon axial currents are then computed in the 1/N expansion. It is already known that the one-loop corrections are suppressed by a factor 1/N; here it is shown that the two-loop corrections are suppressed by 1/N{sup 2}. To leading order, these corrections are exactly the same as would be calculated in the constituent quark model. This method therefore offers a different approach to the constituent quark.
Rare top quark decays in Alternative Left-Right Symmetric Models
Gaitan, R.; Miranda, O. G.; Cabral-Rosetti, L. G.
2007-06-19
We evaluate the flavor changing neutral currents (FCNC) decay t {yields} H0 + c in the context of Alternative Left-Right symmetric Models (ALRM) with extra isosinglet heavy fermions; the FCNC decays may place at tree level and are only supressed by the mixing between ordinary top and charm quarks. We also comment on the decay process t {yields} c + {gamma}, which involves radiative corrections.
A quark model calculation of yy->pipi including final-state interactions
H.G. Blundell; S. Godfrey; G. Hay; Eric Swanson
2000-02-01
A quark model calculation of the processes yy->pi+pi- and yy->pipi is performed. At tree level, only charged pions couple to the initial state photons and neutral pions are not exceeded in the final state. However a small but significant cross section is observed. We demonstrate that this may be accounted for by a rotation in isospin space induced by final-state interactions.
Microscopic nuclear structure models and methods: chiral symmetry, wobbling motion and γ–bands
NASA Astrophysics Data System (ADS)
Sheikh, Javid A.; Bhat, Gowhar H.; Dar, Waheed A.; Jehangir, Sheikh; Ganai, Prince A.
2016-06-01
A systematic investigation of the nuclear observables related to the triaxial degree of freedom is presented using the multi-quasiparticle triaxial projected shell model (TPSM) approach. These properties correspond to the observation of γ-bands, chiral doublet bands and the wobbling mode. In the TPSM approach, γ-bands are built on each quasiparticle configuration and it is demonstrated that some observations in high-spin spectroscopy that have remained unresolved for quite some time could be explained by considering γ-bands based on two-quasiparticle configurations. It is shown in some Ce-, Nd- and Ge-isotopes that the two observed aligned or s-bands originate from the same intrinsic configuration with one of them as the γ-band based on a two-quasiparticle configuration. In the present work, we have also performed a detailed study of γ-bands observed up to the highest spin in dysposium, hafnium, mercury and uranium isotopes. Furthermore, several measurements related to chiral symmetry breaking and wobbling motion have been reported recently. These phenomena, which are possible only for triaxial nuclei, have been investigated using the TPSM approach. It is shown that doublet bands observed in lighter odd–odd Cs-isotopes can be considered as candidates for chiral symmetry breaking. Transverse wobbling motion recently observed in 135Pr has also been investigated and it is shown that TPSM approach provides a reasonable description of the measured properties.
Ibrahim, Tarek; Nath, Pran
2010-09-01
The electric dipole moment (EDM) of the top quark is calculated in a model with a vector like multiplet which mixes with the third generation in an extension of the minimal supersymmetric standard model. Such mixings allow for new CP violating phases. Including these new CP phases, the EDM of the top in this class of models is computed. The top EDM arises from loops involving the exchange of the W, the Z as well as from the exchange involving the charginos, the neutralinos, the gluino, and the vector like multiplet and their superpartners. The analysis of the EDM of the top is more complicated than for the light quarks because the mass of the external fermion, in this case the top quark mass cannot be ignored relative to the masses inside the loops. A numerical analysis is presented and it is shown that the top EDM could be close to 10{sup -19} ecm consistent with the current limits on the EDM of the electron, the neutron and on atomic EDMs. A top EDM of size 10{sup -19} ecm could be accessible in collider experiments such as the International Linear Collider.
Quark-hadron phase transition in a chameleon Brans-Dicke model of brane gravity
NASA Astrophysics Data System (ADS)
Saaidi, Kh.; Mohammadi, A.; Golanbari, T.; Sheikhahmadi, H.; Ratra, B.
2012-08-01
In this work, the quark-hadron phase transition in a chameleon Brans-Dicke model of brane world cosmology within an effective model of QCD is investigated. Whereas, in the chameleon Brans-Dicke model of brane world cosmology, the Friedmann equation and conservation of density energy are modified, resulting in an increased expansion in the early Universe. These have important effects on quark-hadron phase transitions. We investigate the evolution of the physical quantities relevant to quantitative descriptions of the early times, namely, the energy density, ρ, temperature, T, and the scale factor, a, before, during, and after the phase transition. We do this for smooth crossover formalism in which lattice QCD data is used for obtaining the matter equation of state and first order phase transition formalism. Our analyses show that the quark-hadron phase transition has occurred at approximately one nanosecond after the big bang and the general behavior of temperature is similar in both of two approaches.
NASA Astrophysics Data System (ADS)
Zhou, Li-Juan; Zheng, Bo; Zhong, Hong-Wei; Ma, Wei-Xing
2015-03-01
Based on the Dyson-Schwinger Equations (DSEs), the two-quark vacuum condensate, the four-quark vacuum condensate, and the quark gluon mixed vacuum condensate in the non-perturbative QCD vacuum state are investigated by solving the DSEs with rainbow truncation at zero- and finite- temperature, respectively. These condensates are important input parameters in QCD sum rule with zero and finite temperature, and in studying hadron physics, as well as predicting the quark mean squared momentum m20- also called quark virtuality in the QCD vacuum state. The present calculated results show that these physical quantities are almost independent of the temperature below the critical point temperature Tc = 131 MeV, and above Tc the chiral symmetry is restored. For comparison we calculate the temperature dependence of the “in-hadron condensate” for pion. At the same time, we also calculate the ratio of the quark gluon mixed vacuum condensate to the two-quark vacuum condensate by using these condensates, and the unknown quark mean squared momentum in the QCD vacuum state has been obtained. The results show that the ratio m20(T) is almost flat in the temperature region from 0 to Tc, although there are drastic changes of the quark vacuum condensate and the quark gluon mixed vacuum condensate at the region. Our predicted ratio comes out to be m20(T)=2.41 GeV2 at the Chiral limit, which is consistent with other theory model predictions, and strongly indicates the significance that the quark gluon mixed vacuum condensate has played in the virtuality calculations. Supported by National Natural Science Foundation of China (11365002), Guangxi Natural Science Foundation for Young Researchers (2013GXNSFBB053007, 2011GXNSFA018140), Guangxi Education Department (2013ZD049), Guangxi Grant for Excellent Researchers (2011-54), and Guangxi University of Science and Technology Foundation for PhDs (11Z16)
Chiral rotational spectroscopy
NASA Astrophysics Data System (ADS)
Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.
2016-09-01
We introduce chiral rotational spectroscopy, a technique that enables the determination of the orientated optical activity pseudotensor components BX X, BY Y, and BZ Z of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample and provides an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral solely by virtue of their isotopic constitution and molecules with multiple chiral centers. A basic design for a chiral rotational spectrometer together with a model of its functionality is given. Our proposed technique offers the more familiar polarizability components αX X, αY Y, and αZ Z as by-products, which could see it find use even for achiral molecules.
Bottom-quark forward-backward asymmetry in the standard model and beyond.
Grinstein, Benjamín; Murphy, Christopher W
2013-08-01
We computed the bottom-quark forward-backward asymmetry at the Tevatron in the standard model (SM) and for several new physics scenarios. Near the Z pole, the SM bottom asymmetry is dominated by tree level exchanges of electroweak gauge bosons. While above the Z pole, next-to-leading order QCD dominates the SM asymmetry as was the case with the top-quark forward-backward asymmetry. Light new physics, M(NP)≲150 GeV, can cause significant deviations from the SM prediction for the bottom asymmetry. The bottom asymmetry can be used to distinguish between competing new physics (NP) explanations of the top asymmetry based on how the NP interferes with s-channel gluon and Z exchange.
Physical Origin of Density Dependent Force of the Skyrme Type within the Quark Meson Coupling Model
Pierre Guichon; Hrayr Matevosyan; N. Sandulescu; Anthony Thomas
2006-03-17
A density dependent, effective nucleon-nucleon force of the Skyrme type is derived from the quark-meson coupling model--a self-consistent, relativistic quark level description of nuclear matter. This new formulation requires no assumption that the mean scalar field is small and hence constitutes a significant advance over earlier work. The similarity of the effective interaction to the widely used SkM* force encourages us to apply it to a wide range of nuclear problems, beginning with the binding energies and charge distributions of doubly magic nuclei. Finding impressive results in this conventional arena, we apply the same effective interaction, within the Hartree-Fock-Bogoliubov approach, to the properties of nuclei far from stability. The resulting two neutron drip lines and shell quenching are quite satisfactory. Finally, we apply the relativistic formulation to the properties of dense nuclear matter in anticipation of future application to the properties of neutron stars.
nd Scattering Observables Derived from the Quark-Model Baryon-Baryon Interaction
Fujiwara, Y.; Fukukawa, K.
2010-05-12
We solve the nd scattering in the Faddeev formalism, employing the NN sector of the quark-model baryon-baryon interaction fss2. The energy-dependence of the NN interaction, inherent to the (3q)-(3q) resonating-group formulation, is eliminated by the standard off-shell transformation utilizing the 1/sq root(N) factor, where N is the normalization kernel for the (3q)-(3q) system. This procedure yields an extra nonlocality, whose effect is very important to reproduce all the scattering observables below E{sub n}<=65 MeV. The different off-shell properties from the standard meson-exchange potentials, related to the non-locality of the quark-exchange kernel, yields appreciable effects to the differential cross sections and polarization observables of the nd elastic scattering, which are usually attributed to the specific properties of three-body forces.
Hadronic Weak Decays of Λb Baryon in the Covariant Oscillator Quark Model
NASA Astrophysics Data System (ADS)
Mohanta, R.; Giri, A. K.; Khanna, M. P.; Ishida, M.; Ishida, S.; Oda, M.
1999-04-01
Cabibbo allowed two-body hadronic weak decays of Λb baryons are analyzed in the factorization approximation. We use the covariant oscillator quark model to evaluate the heavy --> heavy and heavy --> light form factors. When applied in the heavy quark limit, our form factors satisfy all the constraints imposed by heavy quark symmetry. The decay rates and up-down asymmetries for Λb baryon decaying into Λc+ P(V) are calculated. It is found that the up-down asymmetry is negative in all these decay modes. Furthermore, the prediction Br(Λb --> Λ + J / ψ )= 2.49 × 10-4 is consistent with the recent experimental data. Finally it is pointed out that the CKM-Wolfenstein parameter ▌ + ┨, where η is the CP phase, can be determined from the ratio of the widths Λb --> Λ bar{D}0 and Λb --> Λ J/ ψ, independent of the QCD parameter. The value of (▌ +┨)1/2 calculated in our model agrees very well with the value recently predicted by Rosner.
U{sub A}(1) breaking and phase transition in chiral random matrix model
Sano, T.; Fujii, H.; Ohtani, M.
2009-08-01
We propose a chiral random matrix model which properly incorporates the flavor-number dependence of the phase transition owing to the U{sub A}(1) anomaly term. At finite temperature, the model shows the second-order phase transition with mean-field critical exponents for two massless flavors, while in the case of three massless flavors the transition turns out to be of the first order. The topological susceptibility satisfies the anomalous U{sub A}(1) Ward identity and decreases gradually with the temperature increased.
Keegan, Ronan M.; Bibby, Jaclyn; Thomas, Jens; Xu, Dong; Zhang, Yang; Mayans, Olga; Winn, Martyn D.; Rigden, Daniel J.
2015-01-01
AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solutions produced by Phaser after only 5 min perform surprisingly well, improving the prospects for in situ structure solution by AMPLE during synchrotron visits. Taken together, the results show the potential for AMPLE to run more quickly and successfully solve more targets than previously suspected. PMID:25664744
Keegan, Ronan M; Bibby, Jaclyn; Thomas, Jens; Xu, Dong; Zhang, Yang; Mayans, Olga; Winn, Martyn D; Rigden, Daniel J
2015-02-01
AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solutions produced by Phaser after only 5 min perform surprisingly well, improving the prospects for in situ structure solution by AMPLE during synchrotron visits. Taken together, the results show the potential for AMPLE to run more quickly and successfully solve more targets than previously suspected.
The polarized structure function of the nucleons with a non-extensive statistical quark model
Trevisan, Luis A.; Mirez, Carlos
2013-05-06
We studied an application of nonextensive thermodynamics to describe the polarized structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution, often used in the statistical models, were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and the chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon and by {Delta}u and {Delta}d of the polarized functions.
Search for the Standard Model Higgs Boson Produced in Association with Top Quarks
Wilson, Jonathan Samuel
2011-01-01
We have performed a search for the Standard Model Higgs boson produced in association with top quarks in the lepton plus jets channel. We impose no constraints on the decay of the Higgs boson. We employ ensembles of neural networks to discriminate events containing a Higgs boson from the dominant tt¯background, and set upper bounds on the Higgs production cross section. At a Higgs boson mass mH = 120 GeV/c2 , we expect to exclude a cross section 12.7 times the Standard Model prediction, and we observe an exclusion 27.4 times the Standard Model prediction with 95 % confidence.
Probing the hadron-quark mixed phase at high isospin and baryon density. Sensitive observables
NASA Astrophysics Data System (ADS)
Di Toro, Massimo; Colonna, Maria; Greco, Vincenzo; Shao, Guo-Yun
2016-08-01
We discuss the isospin effect on the possible phase transition from hadronic to quark matter at high baryon density and finite temperatures. The two-Equation of State (Two-EoS) model is adopted to describe the hadron-quark phase transition in dense matter formed in heavy-ion collisions. For the hadron sector we use Relativistic Mean-Field (RMF) effective models, already tested on heavy-ion collision (HIC). For the quark phase we consider various effective models, the MIT-Bag static picture, the Nambu-Jona-Lasinio (NJL) approach with chiral dynamics and finally the NJL coupled to the Polyakov-loop field (PNJL), which includes both chiral and (de)confinement dynamics. The idea is to extract mixed phase properties which appear robust with respect to the model differences. In particular we focus on the phase transitions of isospin asymmetric matter, with two main results: i) an earlier transition to a mixed hadron-quark phase, at lower baryon density/chemical potential with respect to symmetric matter; ii) an "Isospin Distillation" to the quark component of the mixed phase, with predicted effects on the final hadron production. Possible observation signals are suggested to probe in heavy-ion collision experiments at intermediate energies, in the range of the NICA program.
Light fermions in composite models
NASA Astrophysics Data System (ADS)
Khlebnikov, S. Yu.; Peccei, R. D.
1993-07-01
In preon models based on chiral gauge theories, we show that light composite fermions can ensue as a result of gauging a subset of preons in a vectorlike manner. After demonstrating how this mechanism works in a toy example, we construct a one-generation model of quarks which admits a hierarchy between the up and down quark masses as well as between these masses and the compositeness scale. In simple extensions of this model to more generations we discuss the challenges of obtaining any quark mixing. Some possible phenomenological implications of scenarios where quarks and leptons which are heavier are also less pointlike are also considered.
Probing top quark neutral couplings in the Standard Model Effective Field Theory at NLO in QCD
NASA Astrophysics Data System (ADS)
Bylund, Olga Bessidskaia; Maltoni, Fabio; Tsinikos, Ioannis; Vryonidou, Eleni; Zhang, Cen
2016-05-01
Top quark pair production in association with a Z-boson or a photon at the LHC directly probes neutral top-quark couplings. We present predictions for these two processes in the Standard Model (SM) Effective Field Theory (EFT) at next-to-leading order (NLO) in QCD. We include the full set of CP-even dimension-six operators that enter the top-quark interactions with the SM gauge bosons. For comparison, we also present predictions in the SMEFT for top loop-induced HZ production at the LHC and for toverline{t} production at the ILC at NLO in QCD. Results for total cross sections and differential distributions are obtained and uncertainties coming from missing higher orders in the strong coupling and in the EFT expansions are discussed. NLO results matched to the parton shower are available, allowing for event generation to be directly employed in an experimental analyses. Our framework provides a solid basis for the interpretation of current and future measurements in the SMEFT, with improved accuracy and precision.
Spectroscopy without quarks: a Skyrme-model sampler
Karliner, M.; Mattis, M.P.
1986-06-01
Focusing on the characteristic energy range of the baryon resonances (typically 1.5 to 2.5 GeV) meson-nucleon scattering in skyrmion models of the nucleon is studied. It is shown that the purely mesonic Lagrangian yields accurate predictions concerning the spectrum of nucleon and delta resonances and the qualitative behavior of the large majority of pion-nucleon and antikaon-nucleon partial wave amplitudes. 16 refs., 7 figs. (LEW)
Chiral symmetry and chiral-symmetry breaking
Peskin, M.E.
1982-12-01
These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)
Testing the Standard Model by precision measurement of the weak charges of quarks
Ross Young; Roger Carlini; Anthony Thomas; Julie Roche
2007-05-01
In a global analysis of the latest parity-violating electron scattering measurements on nuclear targets, we demonstrate a significant improvement in the experimental knowledge of the weak neutral-current lepton-quark interactions at low-energy. The precision of this new result, combined with earlier atomic parity-violation measurements, limits the magnitude of possible contributions from physics beyond the Standard Model - setting a model-independent, lower-bound on the scale of new physics at ~1 TeV.
Systematic study of baryons in a three-body quark model
NASA Astrophysics Data System (ADS)
Aslanzadeh, M.; Rajabi, A. A.
2016-09-01
We investigated the structure of baryons within a three-body quark model based on hypercentral approach. We considered an SU(6)-invariant potential consisting of the well-known "Coulomb-plus-linear" potential plus some multipole interactions as V ( x) ∝ x - n with n > 2. Then, through an analytical solution, we obtained the energy eigenvalues and eigenfunctions of the three-body problem and evaluated some observables such as the mass spectrum of light baryons and both the electromagnetic elastic form factors, and the charge radii of nucleons. We compared our results with the experimental data and showed that the present model provides a good description of the observed resonances.
Weak Interaction Models with New Quarks and Right-handed Currents
DOE R&D Accomplishments Database
Wilczek, F. A.; Zee, A.; Kingsley, R. L.; Treiman, S. B.
1975-06-01
We discuss various weak interaction issues for a general class of models within the SU(2) x U(1) gauge theory framework, with special emphasis on the effects of right-handed, charged currents and of quarks bearing new quantum numbers. In particular we consider the restrictions on model building which are imposed by the small KL - KS mass difference and by the .I = = rule; and we classify various possibilities for neutral current interactions and, in the case of heavy mesons with new quantum numbers, various possibilities for mixing effects analogous to KL - KS mixing.
Electroweak properties of octet baryons in a light-cone quark-diquark model
NASA Astrophysics Data System (ADS)
Zhang, Jun; Ma, Bo-Qiang
2016-06-01
We study the electroweak properties of ground state octet baryons in a relativistic quark-spectator-diquark model, with a light-front formalism applied to take relativistic effects into account. Our model provides a consistent picture of the electroweak properties of the ground state octet baryons in the low momentum transfer region. The Melosh-Wigner rotation is applied as the transformation relation between spinors in the instant form and front form. Numerical results are presented for the magnetic moments, weak transition charges, and Sachs form factors. Our results are in good agreement with experimental measurements and other theoretical results.
Measurement of parity violation in electron-quark scattering.
2014-02-01
Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks' chirality preference when participating in the weak force, which have been measured directly only once in the past 40 years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2C2u - C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future.
Measurement of parity violation in electron–quark scattering
Wang, D.; Pan, K.; Subedi, R.; Deng, X.; Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Bellini, V.; Beminiwattha, R.; Benesch, J.; Benmokhtar, F.; Bertozzi, W.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, J.-P.; Chudakov, E.; Cisbani, E.; Dalton, M. M.; de Jager, C. W.; De Leo, R.; Deconinck, W.; Deur, A.; Dutta, C.; El Fassi, L.; Erler, J.; Flay, D.; Franklin, G. B.; Friend, M.; Frullani, S.; Garibaldi, F.; Gilad, S.; Giusa, A.; Glamazdin, A.; Golge, S.; Grimm, K.; Hafidi, K.; Hansen, J.-O.; Higinbotham, D. W.; Holmes, R.; Holmstrom, T.; Holt, R. J.; Huang, J.; Hyde, C. E.; Jen, C. M.; Jones, D.; Kang, Hoyoung; King, P. M.; Kowalski, S.; Kumar, K. S.; Lee, J. H.; LeRose, J. J.; Liyanage, N.; Long, E.; McNulty, D.; Margaziotis, D. J.; Meddi, F.; Meekins, D. G.; Mercado, L.; Meziani, Z.-E.; Michaels, R.; Mihovilovic, M.; Muangma, N.; Myers, K. E.; Nanda, S.; Narayan, A.; Nelyubin, V.; Nuruzzaman,; Oh, Y.; Parno, D.; Paschke, K. D.; Phillips, S. K.; Qian, X.; Qiang, Y.; Quinn, B.; Rakhman, A.; Reimer, P. E.; Rider, K.; Riordan, S.; Roche, J.; Rubin, J.; Russo, G.; Saenboonruang, K.; Saha, A.; Sawatzky, B.; Shahinyan, A.; Silwal, R.; Sirca, S.; Souder, P. A.; Suleiman, R.; Sulkosky, V.; Sutera, C. M.; Tobias, W. A.; Urciuoli, G. M.; Waidyawansa, B.; Wojtsekhowski, B.; Ye, L.; Zhao, B.; Zheng, X.
2014-02-05
Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks chirality preference when participating in the weak force, which have been measured directly3, 4 only once in the past 40?years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2C2u???C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future.
Measurement of parity violation in electron-quark scattering
NASA Astrophysics Data System (ADS)
The Jefferson Lab Pvdis Collaboration; Wang, D.; Pan, K.; Subedi, R.; Deng, X.; Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Bellini, V.; Beminiwattha, R.; Benesch, J.; Benmokhtar, F.; Bertozzi, W.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, J.-P.; Chudakov, E.; Cisbani, E.; Dalton, M. M.; de Jager, C. W.; de Leo, R.; Deconinck, W.; Deur, A.; Dutta, C.; El Fassi, L.; Erler, J.; Flay, D.; Franklin, G. B.; Friend, M.; Frullani, S.; Garibaldi, F.; Gilad, S.; Giusa, A.; Glamazdin, A.; Golge, S.; Grimm, K.; Hafidi, K.; Hansen, J.-O.; Higinbotham, D. W.; Holmes, R.; Holmstrom, T.; Holt, R. J.; Huang, J.; Hyde, C. E.; Jen, C. M.; Jones, D.; Kang, Hoyoung; King, P. M.; Kowalski, S.; Kumar, K. S.; Lee, J. H.; Lerose, J. J.; Liyanage, N.; Long, E.; McNulty, D.; Margaziotis, D. J.; Meddi, F.; Meekins, D. G.; Mercado, L.; Meziani, Z.-E.; Michaels, R.; Mihovilovic, M.; Muangma, N.; Myers, K. E.; Nanda, S.; Narayan, A.; Nelyubin, V.; Nuruzzaman; Oh, Y.; Parno, D.; Paschke, K. D.; Phillips, S. K.; Qian, X.; Qiang, Y.; Quinn, B.; Rakhman, A.; Reimer, P. E.; Rider, K.; Riordan, S.; Roche, J.; Rubin, J.; Russo, G.; Saenboonruang, K.; Saha, A.; Sawatzky, B.; Shahinyan, A.; Silwal, R.; Sirca, S.; Souder, P. A.; Suleiman, R.; Sulkosky, V.; Sutera, C. M.; Tobias, W. A.; Urciuoli, G. M.; Waidyawansa, B.; Wojtsekhowski, B.; Ye, L.; Zhao, B.; Zheng, X.
2014-02-01
Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks' chirality preference when participating in the weak force, which have been measured directly only once in the past 40years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2C2u-C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future.
Measurement of parity violation in electron-quark scattering.
2014-02-01
Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks' chirality preference when participating in the weak force, which have been measured directly only once in the past 40 years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2C2u - C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future. PMID:24499917
Inhomogeneous chiral symmetry breaking in dense neutron-star matter
NASA Astrophysics Data System (ADS)
Buballa, Michael; Carignano, Stefano
2016-03-01
An increasing number of model results suggests that chiral symmetry is broken inhomogeneously in a certain window at intermediate densities in the QCD phase diagram. This could have significant effects on the properties of compact stars, possibly leading to new astrophysical signatures. In this contribution we discuss this idea by reviewing recent results on inhomogeneous chiral symmetry breaking under an astrophysics-oriented perspective. After introducing two commonly studied spatial modulations of the chiral condensate, the chiral density wave and the real kink crystal, we focus on their properties and their effect on the equation of state of quark matter. We also describe how these crystalline phases are affected by different elements which are required for a realistic description of a compact star, such as charge neutrality, the presence of magnetic fields, vector interactions and the interplay with color superconductivity. Finally, we discuss possible signatures of inhomogeneous chiral symmetry breaking in the core of compact stars, considering the cases of mass-radius relations and neutrino emissivity explicitly.
Kohyama, Hiroaki
2008-07-01
We construct the phase diagram of the quark-antiquark and diquark condensates at finite temperature and density in the 2+1 dimensional (3D) two flavor massless Gross-Neveu (GN) model with the 4-component quarks. In contrast to the case of the 2-component quarks, there appears the coexisting phase of the quark-antiquark and diquark condensates. This is the crucial difference between the 2-component and 4-component quark cases in the 3D GN model. The coexisting phase is also seen in the 4D Nambu Jona-Lasinio model. Then we see that the 3D GN model with the 4-component quarks bears closer resemblance to the 4D Nambu Jona-Lasinio model.
Blanco, Celia; Ribó, Josep M; Hochberg, David
2015-02-01
We derive the class of population balance equations (PBE), recently applied to model the Viedma deracemization experiment, from an underlying microreversible kinetic reaction scheme. The continuum limit establishing the relationship between the micro- and macroscopic processes and the associated particle fluxes erases the microreversible nature of the molecular interactions in the population growth rate functions and limits the scope of such PBE models to strict kinetic control. The irreversible binary agglomeration processes modeled in those PBEs contribute an additional source of kinetic control. These limitations are crucial regarding the question of the origin of biological homochirality, where the interest in any model lies precisely in its ability for absolute asymmetric synthesis and the amplification of the tiny inherent statistical chiral fluctuations about the ideal racemic composition up to observable enantiometric excess levels.
Emergent Chiral Spin Liquid: Fractional Quantum Hall Effect in a Kagome Heisenberg Model
Gong, Shou-Shu; Zhu, Wei; Sheng, D. N.
2014-01-01
The fractional quantum Hall effect (FQHE) realized in two-dimensional electron systems under a magnetic field is one of the most remarkable discoveries in condensed matter physics. Interestingly, it has been proposed that FQHE can also emerge in time-reversal invariant spin systems, known as the chiral spin liquid (CSL) characterized by the topological order and the emerging of the fractionalized quasiparticles. A CSL can naturally lead to the exotic superconductivity originating from the condense of anyonic quasiparticles. Although CSL was highly sought after for more than twenty years, it had never been found in a spin isotropic Heisenberg model or related materials. By developing a density-matrix renormalization group based method for adiabatically inserting flux, we discover a FQHE in a isotropic kagome Heisenberg model. We identify this FQHE state as the long-sought CSL with a uniform chiral order spontaneously breaking time reversal symmetry, which is uniquely characterized by the half-integer quantized topological Chern number protected by a robust excitation gap. The CSL is found to be at the neighbor of the previously identified Z2 spin liquid, which may lead to an exotic quantum phase transition between two gapped topological spin liquids. PMID:25204626
Testing the standard model by precision measurement of the weak charges of quarks.
Young, R D; Carlini, R D; Thomas, A W; Roche, J
2007-09-21
In a global analysis of the latest parity-violating electron scattering measurements on nuclear targets, we demonstrate a significant improvement in the experimental knowledge of the weak neutral-current lepton-quark interactions at low energy. The precision of this new result, combined with earlier atomic parity-violation measurements, places tight constraints on the size of possible contributions from physics beyond the standard model. Consequently, this result improves the lower-bound on the scale of relevant new physics to approximately 1 TeV.
Regularities in hadron systematics, Regge trajectories and a string quark model.
Chekanov, S.; Levchenko, B.; High Energy Physics; Inst. of Nuclear Physics
2007-01-01
An empirical principle for the construction of a linear relationship between the total angular momentum and squared-mass of baryons is proposed. In order to examine linearity of the trajectories, a rigorous least-squares regression analysis was performed. Unlike the standard Regge-Chew-Frautschi approach, the constructed trajectories do not have nonlinear behavior. A similar regularity may exist for lowest-mass mesons. The linear baryonic trajectories are well described by a semiclassical picture based on a spinning relativistic string with tension. The obtained numerical solution of this model was used to extract the (di)quark masses.
Regularities in hadron systematics, Regge trajectories and a string quark model
Chekanov, S. V.; Levchenko, B. B.
2007-01-01
An empirical principle for the construction of a linear relationship between the total angular momentum and squared-mass of baryons is proposed. In order to examine linearity of the trajectories, a rigorous least-squares regression analysis was performed. Unlike the standard Regge-Chew-Frautschi approach, the constructed trajectories do not have nonlinear behavior. A similar regularity may exist for lowest-mass mesons. The linear baryonic trajectories are well described by a semiclassical picture based on a spinning relativistic string with tension. The obtained numerical solution of this model was used to extract the (di)quark masses.
Ground state heavy baryon production in a relativistic quark-diquark model
NASA Astrophysics Data System (ADS)
Gomshi Nobary, M. A.; Sepahvand, R.
2007-12-01
We use current-current interaction to calculate the fragmentation functions to describe the production of spin-1/2, spin-1/2', and spin-3/2 baryons with massive constituents in a relativistic quark-diquark model. Our results are in their analytic forms and are applicable for singly, doubly, and triply heavy baryons. We discuss the production of Ωbbc, Ωbcc, and Ωccc baryons in some detail. The results are satisfactorily compared with those obtained for triply heavy baryons calculated in a perturbative regime within reasonable values of the parameters involved.
Ground state heavy baryon production in a relativistic quark-diquark model
Gomshi Nobary, M. A.; Sepahvand, R.
2007-12-01
We use current-current interaction to calculate the fragmentation functions to describe the production of spin-1/2, spin-1/2{sup '}, and spin-3/2 baryons with massive constituents in a relativistic quark-diquark model. Our results are in their analytic forms and are applicable for singly, doubly, and triply heavy baryons. We discuss the production of {omega}{sub bbc}, {omega}{sub bcc}, and {omega}{sub ccc} baryons in some detail. The results are satisfactorily compared with those obtained for triply heavy baryons calculated in a perturbative regime within reasonable values of the parameters involved.
Djouadi, Abdelhak; Moreau, Gregory; Richard, Francois; Singh, Ritesh K.
2010-10-01
The CDF and D0 experiments have reported on the measurement of the forward-backward asymmetry of top quark pair production at the Tevatron and the result is that it is more than 2 standard deviations above the predicted value in the standard model. This has to be added to the long-standing anomaly in the forward-backward asymmetry for bottom quark production at LEP which is 3 standard deviations different from the standard model value. The discrepancy in the bottom asymmetry can be accounted for by the contributions of Kaluza-Klein excitations of electroweak gauge bosons at LEP in warped extra-dimensional models in which the fermions are localized differently along the extra dimension so that the gauge interactions of heavy third generation fermions are naturally different from that of light fermions. In this paper, we show that it is more difficult to elaborate a model generating a significant top asymmetry through exchanges of Kaluza-Klein gluons at the Tevatron due to the indirect constraints originating from precision electroweak data.
Quark propagator in a truncation scheme beyond the rainbow approximation
NASA Astrophysics Data System (ADS)
Fu, Hui-Feng; Wang, Qing
2016-01-01
The quark propagator is studied under a truncation scheme beyond the rainbow approximation by dressing the quark-gluon vertex nonperturbatively. It is found that, in the chiral limit with dynamical symmetry breaking, the dynamical quark mass and the quark condensate are significantly enhanced due to the non-Abelian contribution arising from the three-gluon interaction compared to those under the rainbow approximation, and the critical strength of the dynamical chiral symmetry breaking is much lowered. The Abelian contribution is much smaller than the non-Abelian contribution. A technical issue on removing the ultraviolet divergences, including the overlapping divergences, is discussed.
Ahmadov, A.; Azuelos, G.; Bauer, U.; Belyaev, A.; Berger, E. L.; Sullivan, Z.; Tait, T. M. P.
2000-03-24
The top quark, when it was finally discovered at Fermilab in 1995 completed the three-generation structure of the Standard Model (SM) and opened up the new field of top quark physics. Viewed as just another SM quark, the top quark appears to be a rather uninteresting species. Produced predominantly, in hadron-hadron collisions, through strong interactions, it decays rapidly without forming hadrons, and almost exclusively through the single mode t {r_arrow} Wb. The relevant CKM coupling V{sub tb} is already determined by the (three-generation) unitarity of the CKM matrix. Rare decays and CP violation are unmeasurable small in the SM. Yet the top quark is distinguished by its large mass, about 35 times larger than the mass of the next heavy quark, and intriguingly close to the scale of electroweak (EW) symmetry breaking. This unique property raises a number of interesting questions. Is the top quark mass generated by the Higgs mechanism as the SM predicts and is its mass related to the top-Higgs-Yukawa coupling? Or does it play an even more fundamental role in the EW symmetry breaking mechanism? If there are new particles lighter than the top quark, does the top quark decay into them? Could non-SM physics first manifest itself in non-standard couplings of the top quark which show up as anomalies in top quark production and decays? Top quark physics tries to answer these questions. Several properties of the top quark have already been examined at the Tevatron. These include studies of the kinematical properties of top production, the measurements of the top mass, of the top production cross-section, the reconstruction of t{bar t}pairs in the fully hadronic final states, the study of {tau} decays of the top quark, the reconstruction of hadronic decays of the W boson from top decays, the search for flavor changing neutral current decays, the measurement of the W helicity in top decays, and bounds on t{bar t} spin correlations. Most of these measurements are limited by
The Discovery of the Top Quark
DOE R&D Accomplishments Database
Sinervo, P.K.
1995-12-01
The top quark and the Higgs boson are the heaviest elementary particles predicted by the standard model. The four lightest quark flavours, the up, down, strange and charm quarks, were well-established by the mid-1970's. The discovery in 1977 of the {Tau} resonances, a new family of massive hadrons, required the introduction of the fifth quark flavour. Experimental and theoretical studies have indicated that this quark also has a heavier partner, the top quark.
Simplified models for Higgs physics: singlet scalar and vector-like quark phenomenology
Dolan, Matthew J.; Hewett, J. L.; Krämer, M.; Rizzo, T. G.
2016-07-08
Simplified models provide a useful tool to conduct the search and exploration of physics beyond the Standard Model in a model-independent fashion. In this study, we consider the complementarity of indirect searches for new physics in Higgs couplings and distributions with direct searches for new particles, using a simplified model which includes a new singlet scalar resonance and vector-like fermions that can mix with the SM top-quark. We fit this model to the combined ATLAS and CMS 125 GeV Higgs production and coupling measurements and other precision electroweak constraints, and explore in detail the effects of the new matter contentmore » upon Higgs production and kinematics. Finally, we highlight some novel features and decay modes of the top partner phenomenology, and discuss prospects for Run II.« less
Simplified models for Higgs physics: singlet scalar and vector-like quark phenomenology
NASA Astrophysics Data System (ADS)
Dolan, Matthew J.; Hewett, J. L.; Krämer, M.; Rizzo, T. G.
2016-07-01
Simplified models provide a useful tool to conduct the search and exploration of physics beyond the Standard Model in a model-independent fashion. In this work we consider the complementarity of indirect searches for new physics in Higgs couplings and distributions with direct searches for new particles, using a simplified model which includes a new singlet scalar resonance and vector-like fermions that can mix with the SM top-quark. We fit this model to the combined ATLAS and CMS 125 GeV Higgs production and coupling measurements and other precision electroweak constraints, and explore in detail the effects of the new matter content upon Higgs production and kinematics. We highlight some novel features and decay modes of the top partner phenomenology, and discuss prospects for Run II.
Phase diagram and the pseudogap state in a linear chiral homopolymer model
NASA Astrophysics Data System (ADS)
Sinelnikova, A.; Niemi, A. J.; Ulybyshev, M.
2015-09-01
The phase structure of a single self-interacting homopolymer chain is investigated in terms of a universal theoretical model, designed to describe the chain in the infrared limit of slow spatial variations. The effects of chirality are studied and compared with the influence of a short-range attractive interaction between monomers, at various ambient temperature values. In the high-temperature limit the homopolymer chain is in the self-avoiding random walk phase. At very low temperatures two different phases are possible: When short-range attractive interactions dominate over chirality, the chain collapses into a space-filling conformation. But when the attractive interactions weaken, there is a low-temperature unfolding transition and the chain becomes like a straight rod. Between the high- and low-temperature limits, several intermediate states are observed, including the θ regime and pseudogap state, which is a novel form of phase state in the context of polymer chains. Applications to polymers and proteins, in particular collagen, are suggested.
Diquark condensation effects on hot quark star configurations
NASA Astrophysics Data System (ADS)
Öztas, A.; Blaschke, D.; Fredriksson, S.; Grigorian, H.
The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the form-factors of the interaction on the phase diagram of quark matter. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state under the condition of β- equilibrium and charge neutrality. We calculate the quark star configurations by solving the Tolman- Oppenheimer- Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ΔMc2 ~ 1053 erg. We find that this energy could not serve as an engine for explosive phenomena since the phase transition is not first order. Contrary to naive expectations the mass defect increases when for a given temperature we neglect the possibility of diquark condensation.
Diquark condensation effects on hot quark star configurations
NASA Astrophysics Data System (ADS)
Blaschke, D.; Fredriksson, S.; Grigorian, H.; Öztasş, A. M.
2004-05-01
The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the formfactors of the interaction on the phase diagram of quark matter. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state under the condition of β-equilibrium and charge neutrality. We calculate the quark star configurations by solving the Tolman-Oppenheimer-Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ΔMc2~1053 erg. We find that this energy could not serve as an engine for explosive phenomena since the phase transition is not first order. Contrary to naive expectations the mass defect increases when for a given temperature we neglect the possibility of diquark condensation.
Jet substructures of boosted polarized hadronic top quarks
NASA Astrophysics Data System (ADS)
Kitadono, Yoshio; Li, Hsiang-nan
2016-03-01
We study jet substructures of a boosted polarized top quark, which undergoes the hadronic decay t →b u d ¯, in the perturbative QCD framework, focusing on the energy profile and the differential energy profile. These substructures are factorized into the convolution of a hard top-quark decay kernel with a bottom-quark jet function and a W -boson jet function, where the latter is further factorized into the convolution of a hard W -boson decay kernel with two light-quark jet functions. Computing the hard kernels to leading order in QCD and including the resummation effect in the jet functions, we show that the differential jet energy profile is a useful observable for differentiating the helicity of a boosted hadronic top quark: a right-handed top jet exhibits quick descent of the differential energy profile with the inner test cone radius r , which is attributed to the V -A structure of weak interaction and the dead-cone effect associated with the W -boson jet. The above helicity differentiation may help reveal the chiral structure of physics beyond the standard model at high energies.
Chiral perturbation theory with nucleons
Meissner, U.G.
1991-09-01
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, {pi}N scattering and the {sigma}-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon.
Nucleon-to-{delta} axial transition form factors in relativistic baryon chiral perturbation theory
Geng, L. S.; Camalich, J. Martin; Alvarez-Ruso, L.; Vacas, M. J. Vicente
2008-07-01
We report a theoretical study of the axial nucleon-to-delta (1232) (N{yields}{delta}) transition form factors up to one-loop order in relativistic baryon chiral perturbation theory. We adopt a formalism in which the {delta} couplings obey the spin-3/2 gauge symmetry and, therefore, decouple the unphysical spin-1/2 fields. We compare the results with phenomenological form factors obtained from neutrino bubble-chamber data and in quark models.
Excited D{sub s} (and Pentaquarks) in Chiral Perturbation Theory
Thomas Mehen
2005-01-01
I present results of a heavy hadron chiral perturbation theory analysis of the decays and masses of the recently discovered excited charm mesons. The present data on the electromagnetic branching ratios are consistent with heavy quark symmetry predictions and disfavor a molecular interpretation of these states. I also discuss model independent predictions for the strong decays of pentaquarks in the 10-bar representation of SU(3) which can be used to constrain the angular momentum and parity quantum numbers of these states.
Keegan, Ronan M.; Bibby, Jaclyn; Thomas, Jens; Xu, Dong; Zhang, Yang; Mayans, Olga; Winn, Martyn D.; Rigden, Daniel J.
2015-02-01
Two ab initio modelling programs solve complementary sets of targets, enhancing the success of AMPLE with small proteins. AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solutions produced by Phaser after only 5 min perform surprisingly well, improving the prospects for in situ structure solution by AMPLE during synchrotron visits. Taken together, the results show the potential for AMPLE to run more quickly and successfully solve more targets than previously suspected.
Hybrid stars using the quark-meson coupling and proper-time Nambu-Jona-Lasinio models
NASA Astrophysics Data System (ADS)
Whittenbury, D. L.; Matevosyan, H. H.; Thomas, A. W.
2016-03-01
Background: At high density deconfinement of hadronic matter may occur leading to quark matter. The immense densities reached in the inner core of massive neutron stars may be sufficient to facilitate the transition. Purpose: To investigate a crossover transition between two phenomenological models which epitomize quantum chromodynamics in two different regimes, while incorporating the influence of quark degrees of freedom in both. Method: We use the Hartree-Fock quark-meson coupling model and the proper-time regularized three-flavor Nambu-Jona-Lasinio model to describe hadronic and quark matter, respectively. Hybrid equations of state are obtained by interpolating the energy density as a function of total baryonic density and calculating the pressure. Results: Equations of state for hadronic, quark, and hybrid matter and the resulting mass versus radius curves for hybrid stars are shown, as well as other relevant physical quantities such as species fractions and the speed of sound in matter. Conclusions: The observations of massive neutron stars can certainly be explained within such a construction. However, the so-called thermodynamic correction arising from an interpolation method can have a considerable impact on the equation of state. The interpolation dependency of and physical meaning behind such corrections require further study.
The K⁻N→KΞ reaction in coupled channel chiral models up to next-to-leading order
Magas, V. K.; Ramos, A.; Feijoo, A.
2009-01-01
We study the meson-baryon interaction in S-wave in the strangeness S=-1 sector using a chiral unitary approach based on a next-to-leading order chiral SU(3) Lagrangian. We fit our model to the large set of experimental data in different two-body channels. We pay particular attention to the K⁻N→KΞ reaction, where the effect of the next-to-leading order terms in the Lagrangian are sufficiently large to be observed, since at tree level the cross section of this reaction is zero. For these channels we improve our approach by phenomenologically taking into account effects of the high spin hyperonic resonances.
Quark matter at high density based on an extended confined isospin-density-dependent mass model
NASA Astrophysics Data System (ADS)
Qauli, A. I.; Sulaksono, A.
2016-01-01
We investigate the effect of the inclusion of relativistic Coulomb terms in a confined-isospin-density-dependent-mass (CIDDM) model of strange quark matter (SQM). We found that if we include the Coulomb term in scalar density form, the SQM equation of state (EOS) at high densities is stiffer but if we include the Coulomb term in vector density form it is softer than that of the standard CIDDM model. We also investigate systematically the role of each term of the extended CIDDM model. Compared with what was reported by Chu and Chen [Astrophys. J. 780, 135 (2014)], we found the stiffness of SQM EOS is controlled by the interplay among the oscillator harmonic, isospin asymmetry and Coulomb contributions depending on the parameter's range of these terms. We have found that the absolute stable condition of SQM and the mass of 2 M⊙ pulsars can constrain the parameter of oscillator harmonic κ1≈0.53 in the case the Coulomb term is excluded. If the Coulomb term is included, for the models with their parameters are consistent with SQM absolute stability condition, the 2.0 M⊙ constraint more prefers the maximum mass prediction of the model with the scalar Coulomb term than that of the model with the vector Coulomb term. On the contrary, the high densities EOS predicted by the model with the vector Coulomb is more compatible with the recent perturbative quantum chromodynamics result [1] than that predicted by the model with the scalar Coulomb. Furthermore, we also observed the quark composition in a very high density region depends quite sensitively on the kind of Coulomb term used.
Chiral symmetry and $\pi $-$\pi $ scattering in the Covariant Spectator Theory
Biernat, Elmar P.; Peña, M. T.; Ribeiro, J. E.; Stadler, Alfred; Gross, Franz
2014-11-14
The π-π scattering amplitude calculated with a model for the quark-antiquark interaction in the framework of the Covariant Spectator Theory (CST) is shown to satisfy the Adler zero constraint imposed by chiral symmetry. The CST formalism is established in Minkowski space and our calculations are performed in momentum space. We prove that the axial-vector Ward-Takahashi identity is satisfied by our model. Then we show that, similarly to what happens within the Bethe-Salpeter formalism, application of the axial-vector Ward Takahashi identity to the CST π-π scattering amplitude allows us to sum the intermediate quark-quark interactions to all orders. Thus, the Adler self-consistency zero for π-π scattering in the chiral limit emerges as the result for this sum.
Phase transitions and ordering structures of a model of a chiral helimagnet in three dimensions
NASA Astrophysics Data System (ADS)
Nishikawa, Yoshihiko; Hukushima, Koji
2016-08-01
Phase transitions in a classical Heisenberg spin model of a chiral helimagnet with the Dzyaloshinskii-Moriya interaction in three dimensions are numerically studied. By using the event-chain Monte Carlo algorithm recently developed for particle and continuous spin systems, we perform equilibrium Monte Carlo simulations for large systems up to about 106 spins. Without magnetic fields, the system undergoes a continuous phase transition with critical exponents of the three-dimensional XY model, and a uniaxial periodic helical structure emerges in the low-temperature region. In the presence of a magnetic field perpendicular to the axis of the helical structure, it is found that there exists a critical point on the temperature and magnetic-field phase diagram and that above the critical point the system exhibits a phase transition with strong divergence of the specific heat and the uniform magnetic susceptibility.
Babich, Ronald; Howard, Joseph; Rebbi, Claudio; Garron, Nicolas; Hoelbling, Christian; Lellouch, Laurent
2006-10-01
We present results for the {delta}S=2 matrix elements which are required to study neutral kaon mixing in the standard model (SM) and beyond . We also provide leading chiral order results for the matrix elements of the electroweak penguin operators which give the dominant {delta}I=3/2 contribution to direct CP violation in K{yields}{pi}{pi} decays. Our calculations were performed with Neuberger fermions on two sets of quenched Wilson gauge configurations at inverse lattice spacings of approximately 2.2 GeV and 1.5 GeV. All renormalizations were implemented nonperturbatively in the regularization-independent/momentum (RI/MOM) scheme, where we accounted for subleading operator product expansion corrections and discretization errors. We find ratios of non-SM to SM matrix elements which are roughly twice as large as in the only other dedicated lattice study of these amplitudes. On the other hand, our results for the electroweak penguin matrix elements are in good agreement with two recent domain-wall fermion calculations. As a by-product of our study, we determine the strange quark mass. Our main results are summarized and discussed in Sec. VII. Within our statistics, we find no evidence for scaling violations.
Khachatryan, Vardan
2015-06-09
A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5fb-1 collected by the CMS experiment at the LHC in pp collisions at a centre-of-mass energy of 8TeV. In order to separate the signal from the larger tt¯ + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratiomore » between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, μ, relative to the standard model prediction for a Higgs boson mass of 125GeV. The observed (expected) exclusion limit at a 95 % confidence level is μ < 4.2 (3.3), corresponding to a best fit value μ^ = 1.2+1.6-1.5.« less
Khachatryan, Vardan
2015-06-09
A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5fb^{-1} collected by the CMS experiment at the LHC in pp collisions at a centre-of-mass energy of 8TeV. In order to separate the signal from the larger tt¯ + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, μ, relative to the standard model prediction for a Higgs boson mass of 125GeV. The observed (expected) exclusion limit at a 95 % confidence level is μ < 4.2 (3.3), corresponding to a best fit value μ^ = 1.2^{+1.6}_{-1.5}.
B → K(∗)μ+μ- in covariant quark model
NASA Astrophysics Data System (ADS)
Liptaj, A.; Dubnička, S.; Dubničková, A. Z.; Ivanov, M. A.
2015-11-01
The covariant quark model with infrared confinement (CQM) is a well-suited theoretical framework to describe large variety of hadronic processes, including rare decays of heavy mesons. In this text we focus on the reactions B → K(∗)μ+μ-, which have been recently measured by Refs. 1-4. The measurements include also information about the angular distributions and their significance is given by possible New Physics (NP) effects which are predicted in numerous beyond Standard Model (SM) scenarios. Even with clever choice of experimental observables, a model dependence cannot be fully removed from the theoretical predictions. In this text we present the computation of the B → K(∗) form factors within the CQM and give results for some of the most commonly used observables (AFB, FL).
Top quark polarization as a probe of models with extra gauge bosons.
Berger, E. L.; Cao, Q.-H.; Chen, C.-R.; Zhang, H.
2011-06-13
New heavy gauge bosons exist in many models of new physics beyond the standard model of particle physics. Discovery of these W{prime} and Z{prime} resonances and the establishment of their spins, couplings, and other quantum numbers would shed light on the gauge structure of the new physics. The measurement of the polarization of the SM fermions from the gauge boson decays would decipher the handedness of the coupling of the new states, an important relic of the primordial new physics symmetry. Since the top quark decays promptly, its decay preserves spin information. We show how decays of new gauge bosons into third generation fermions (W{prime} {yields} tb, Z{prime} {yields} t{bar t}) can be used to determine the handedness of the couplings of the new states and to discriminate among various new physics models.
Decay widths of ground-state and excited {Xi}{sub b} baryons in a nonrelativistic quark model
Limphirat, Ayut; Kobdaj, Chinorat; Suebka, Prasart; Yan, Yupeng
2010-11-15
Decay processes of ground and excited bottom baryons are studied in the {sup 3}P{sub 0} nonrelativistic quark model with all model parameters fixed in the sector of light quarks. Using as an input the recent mass of {Xi}{sub b} and the theoretical masses of {Xi}{sub b}{sup *} and {Xi}{sub b}{sup '}, narrow decay widths are predicted for the ground-state bottom baryons {Xi}{sub b}{sup *} and {Xi}{sub b}{sup '}. The work predicts large decay widths, about 100 MeV for the {rho}-type orbital excitation states of {Xi}{sub b}.
Adler, S.L.
1999-01-01
We construct extensions of the standard model based on the hypothesis that Higgs bosons also exhibit a family structure and that the flavor weak eigenstates in the three families are distinguished by a discrete Z{sub 6} chiral symmetry that is spontaneously broken by the Higgs sector. We study in detail at the tree level models with three Higgs doublets and with six Higgs doublets comprising two weakly coupled sets of three. In a leading approximation of S{sub 3} cyclic permutation symmetry the three-Higgs-doublet model gives a {open_quotes}democratic{close_quotes} mass matrix of rank 1, while the six-Higgs-doublet model gives either a rank-1 mass matrix or, in the case when it spontaneously violates {ital CP}, a rank-2 mass matrix corresponding to nonzero second family masses. In both models, the CKM matrix is exactly unity in the leading approximation. Allowing small explicit violations of cyclic permutation symmetry generates small first family masses in the six-Higgs-doublet model, and first and second family masses in the three-Higgs-doublet model, and gives a nontrivial CKM matrix in which the mixings of the first and second family quarks are naturally larger than mixings involving the third family. Complete numerical fits are given for both models, flavor-changing neutral current constraints are discussed in detail, and the issues of unification of couplings and neutrino masses are addressed. On a technical level, our analysis uses the theory of circulant and retrocirculant matrices, the relevant parts of which are reviewed. {copyright} {ital 1998} {ital The American Physical Society}
Baryons with Ginsparg-Wilson quarks in a staggered sea
Tiburzi, Brian C.
2005-11-01
We determine the masses and magnetic moments of the octet baryons in chiral perturbation theory formulated for a mixed lattice action of Ginsparg-Wilson valence quarks and staggered sea quarks. Taste-symmetry breaking does not occur at next-to-leading order in the combined lattice spacing and chiral expansion. Expressions derived for masses and magnetic moments are required for addressing lattice artifacts in mixed-action simulations of these observables.
Model-independent measurement of the W-boson helicity in top-quark decays at D0.
Abazov, V M; Abbott, B; Abolins, M; Acharya, B S; Adams, M; Adams, T; Aguilo, E; Ahn, S H; Ahsan, M; Alexeev, G D; Alkhazov, G; Alton, A; Alverson, G; Alves, G A; Anastasoaie, M; Ancu, L S; Andeen, T; Anderson, S; Andrieu, B; Anzelc, M S; Arnoud, Y; Arov, M; Arthaud, M; Askew, A; Asman, B; Assis Jesus, A C S; Atramentov, O; Autermann, C; Avila, C; Ay, C; Badaud, F; Baden, A; Bagby, L; Baldin, B; Bandurin, D V; Banerjee, S; Banerjee, P; Barberis, E; Barfuss, A-F; Bargassa, P; Baringer, P; Barreto, J; Bartlett, J F; Bassler, U; Bauer, D; Beale, S; Bean, A; Begalli, M; Begel, M; Belanger-Champagne, C; Bellantoni, L; Bellavance, A; Benitez, J A; Beri, S B; Bernardi, G; Bernhard, R; Bertram, I; Besançon, M; Beuselinck, R; Bezzubov, V A; Bhat, P C; Bhatnagar, V; Biscarat, C; Blazey, G; Blekman, F; Blessing, S; Bloch, D; Bloom, K; Boehnlein, A; Boline, D; Bolton, T A; Borissov, G; Bose, T; Brandt, A; Brock, R; Brooijmans, G; Bross, A; Brown, D; Buchanan, N J; Buchholz, D; Buehler, M; Buescher, V; Bunichev, V; Burdin, S; Burke, S; Burnett, T H; Buszello, C P; Butler, J M; Calfayan, P; Calvet, S; Cammin, J; Carvalho, W; Casey, B C K; Cason, N M; Castilla-Valdez, H; Chakrabarti, S; Chakraborty, D; Chan, K M; Chan, K; Chandra, A; Charles, F; Cheu, E; Chevallier, F; Cho, D K; Choi, S; Choudhary, B; Christofek, L; Christoudias, T; Cihangir, S; Claes, D; Coadou, Y; Cooke, M; Cooper, W E; Corcoran, M; Couderc, F; Cousinou, M-C; Crépé-Renaudin, S; Cutts, D; Cwiok, M; da Motta, H; Das, A; Davies, G; De, K; de Jong, S J; De La Cruz-Burelo, E; De Oliveira Martins, C; Degenhardt, J D; Déliot, F; Demarteau, M; Demina, R; Denisov, D; Denisov, S P; Desai, S; Diehl, H T; Diesburg, M; Dominguez, A; Dong, H; Dudko, L V; Duflot, L; Dugad, S R; Duggan, D; Duperrin, A; Dyer, J; Dyshkant, A; Eads, M; Edmunds, D; Ellison, J; Elvira, V D; Enari, Y; Eno, S; Ermolov, P; Evans, H; Evdokimov, A; Evdokimov, V N; Ferapontov, A V; Ferbel, T; Fiedler, F; Filthaut, F; Fisher, W; Fisk, H E; Ford, M; Fortner, M; Fox, H; Fu, S; Fuess, S; Gadfort, T; Galea, C F; Gallas, E; Galyaev, E; Garcia, C; Garcia-Bellido, A; Gavrilov, V; Gay, P; Geist, W; Gelé, D; Gerber, C E; Gershtein, Y; Gillberg, D; Ginther, G; Gollub, N; Gómez, B; Goussiou, A; Grannis, P D; Greenlee, H; Greenwood, Z D; Gregores, E M; Grenier, G; Gris, Ph; Grivaz, J-F; Grohsjean, A; Grünendahl, S; Grünewald, M W; Guo, J; Guo, F; Gutierrez, P; Gutierrez, G; Haas, A; Hadley, N J; Haefner, P; Hagopian, S; Haley, J; Hall, I; Hall, R E; Han, L; Hansson, P; Harder, K; Harel, A; Harrington, R; Hauptman, J M; Hauser, R; Hays, J; Hebbeker, T; Hedin, D; Hegeman, J G; Heinmiller, J M; Heinson, A P; Heintz, U; Hensel, C; Herner, K; Hesketh, G; Hildreth, M D; Hirosky, R; Hobbs, J D; Hoeneisen, B; Hoeth, H; Hohlfeld, M; Hong, S J; Hossain, S; Houben, P; Hu, Y; Hubacek, Z; Hynek, V; Iashvili, I; Illingworth, R; Ito, A S; Jabeen, S; Jaffré, M; Jain, S; Jakobs, K; Jarvis, C; Jesik, R; Johns, K; Johnson, C; Johnson, M; Jonckheere, A; Jonsson, P; Juste, A; Kajfasz, E; Kalinin, A M; Kalk, J R; Kalk, J M; Kappler, S; Karmanov, D; Kasper, P A; Katsanos, I; Kau, D; Kaur, R; Kaushik, V; Kehoe, R; Kermiche, S; Khalatyan, N; Khanov, A; Kharchilava, A; Kharzheev, Y M; Khatidze, D; Kim, T J; Kirby, M H; Kirsch, M; Klima, B; Kohli, J M; Konrath, J-P; Korablev, V M; Kozelov, A V; Krop, D; Kuhl, T; Kumar, A; Kunori, S; Kupco, A; Kurca, T; Kvita, J; Lacroix, F; Lam, D; Lammers, S; Landsberg, G; Lebrun, P; Lee, W M; Leflat, A; Lehner, F; Lellouch, J; Leveque, J; Li, J; Li, Q Z; Li, L; Lietti, S M; Lima, J G R; Lincoln, D; Linnemann, J; Lipaev, V V; Lipton, R; Liu, Y; Liu, Z; Lobodenko, A; Lokajicek, M; Love, P; Lubatti, H J; Luna, R; Lyon, A L; Maciel, A K A; Mackin, D; Madaras, R J; Mättig, P; Magass, C; Magerkurth, A; Mal, P K; Malbouisson, H B; Malik, S; Malyshev, V L; Mao, H S; Maravin, Y; Martin, B; McCarthy, R; Melnitchouk, A; Mendoza, L; Mercadante, P G; Merkin, M; Merritt, K W; Meyer, J; Meyer, A; Millet, T; Mitrevski, J; Molina, J; Mommsen, R K; Mondal, N K; Moore, R W; Moulik, T; Muanza, G S; Mulders, M; Mulhearn, M; Mundal, O; Mundim, L; Nagy, E; Naimuddin, M; Narain, M; Naumann, N A; Neal, H A; Negret, J P; Neustroev, P; Nilsen, H; Nogima, H; Novaes, S F; Nunnemann, T; O'Dell, V; O'Neil, D C; Obrant, G; Ochando, C; Onoprienko, D; Oshima, N; Osta, J; Otec, R; Otero Y Garzón, G J; Owen, M; Padley, P; Pangilinan, M; Parashar, N; Park, S-J; Park, S K; Parsons, J; Partridge, R; Parua, N; Patwa, A; Pawloski, G; Penning, B; Perfilov, M; Peters, K; Peters, Y; Pétroff, P; Petteni, M; Piegaia, R; Piper, J; Pleier, M-A; Podesta-Lerma, P L M; Podstavkov, V M; Pogorelov, Y; Pol, M-E; Polozov, P; Pope, B G; Popov, A V; Potter, C; Prado da Silva, W L; Prosper, H B; Protopopescu, S; Qian, J; Quadt, A; Quinn, B; Rakitine, A; Rangel, M S; Ranjan, K; Ratoff, P N; Renkel, P; Reucroft, S; Rich, P; Rieger, J; Rijssenbeek, M; Ripp-Baudot, I; Rizatdinova, F; Robinson, S; Rodrigues, R F; Rominsky, M; Royon, C; Rubinov, P; Ruchti, R; Safronov, G; Sajot, G; 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Varnes, E W; Vasilyev, I A; Vaupel, M; Verdier, P; Vertogradov, L S; Verzocchi, M; Villeneuve-Seguier, F; Vint, P; Vokac, P; Von Toerne, E; Voutilainen, M; Wagner, R; Wahl, H D; Wang, L; Wang, M H L S; Warchol, J; Watts, G; Wayne, M; Weber, M; Weber, G; Welty-Rieger, L; Wenger, A; Wermes, N; Wetstein, M; White, A; Wicke, D; Wilson, G W; Wimpenny, S J; Wobisch, M; Wood, D R; Wyatt, T R; Xie, Y; Yacoob, S; Yamada, R; Yan, M; Yasuda, T; Yatsunenko, Y A; Yip, K; Yoo, H D; Youn, S W; Yu, J; Zatserklyaniy, A; Zeitnitz, C; Zhao, T; Zhou, B; Zhu, J; Zielinski, M; Zieminska, D; Zieminski, A; Zivkovic, L; Zutshi, V; Zverev, E G
2008-02-15
We present the first model-independent measurement of the helicity of W bosons produced in top quark decays, based on a 1 fb(-1) sample of candidate tt events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron pp Collider. We reconstruct the angle theta(*) between the momenta of the down-type fermion and the top quark in the W boson rest frame for each top quark decay. A fit of the resulting costheta(*) distribution finds that the fraction of longitudinal W bosons f(0)=0.425+/-0.166(stat)+/-0.102(syst) and the fraction of right-handed W bosons f(+)=0.119+/-0.090(stat)+/-0.053(syst), which is consistent at the 30% C.L. with the standard model. PMID:18352460
Heinson, A. P.
2006-11-17
First observed in 1995, the top quark is one of a pair of third-generation quarks in the Standard Model of particle physics. It has charge +2/3e and a mass of 171.4 GeV, about 40 times heavier than its partner, the bottom quark. The CDF and DO collaborations have identified several hundred events containing the decays of top-antitop pairs in the large dataset collected at the Tevatron proton-antiproton collider over the last four years. They have used these events to measure the top quark's mass to nearly 1% precision and to study other top quark properties. The mass of the top quark is a fundamental parameter of the Standard Model, and knowledge of its value with small uncertainty allows us to predict properties of the as-yet-unobserved Higgs boson. This paper presents the status of the measurements of the top quark mass. It is based on a talk I gave at the Conference on the Intersections of Particle and Nuclear Physics in Puerto Rico, May 2006, which also included discussion of measurements of other top quark properties.
X (4140 ), X (4274 ), X (4500 ), and X (4700 ) in the relativized quark model
NASA Astrophysics Data System (ADS)
Lü, Qi-Fang; Dong, Yu-Bing
2016-10-01
We investigate the masses of c s c ¯ s ¯ tetraquark states in a diquark-antidiquark picture employing the relativized quark model proposed by Godfrey and Isgur. Only the antitriplet diquark states in color space are calculated. The diquark masses are obtained with the relativized potential first, and then the diquark and antidiquark are treated as the usual antiquark and quark, respectively, and the masses of the tetraquark states are obtained by solving the Schrödinger equation with the relativized potential between the diquark and antidiquark. The theoretical uncertainties induced by screening effects are also taken into account. It is found that the resonance of X (4140 ) can be regarded as the c s c ¯s ¯ tetraquark ground states, and the X (4700 ) can be assigned as the 2 S excited tetraquark state. When the internal excited diquarks are taken into account, the resonance of X (4500 ) can be explained as the tetraquark composed of one 2 S scalar diquark and one scalar antidiquark. In our approach, the X (4274 ) cannot be explained as a tetraquark state; however, it can be a good candidate of the conventional χc 1(3 3P1) state. In addition, other charmoniumlike states χc 0(3915 ), X (4350 ), X (4630 ), and X (4660 ), as the c s c ¯s ¯ tetraquark states, are also discussed.
Charged-particle rapidity density in Au+Au collisions in a quark combination model
NASA Astrophysics Data System (ADS)
Shao, Feng-Lan; Yao, Tao; Xie, Qu-Bing
2007-03-01
Rapidity/pseudorapidity densities for charged particles and their centrality, rapidity, and energy dependence in Au+Au collisions at the Relativistic Heavy Ion Collider are studied in a quark combination model. Using a Gaussian-type rapidity distribution for constituent quarks as a result of Landau hydrodynamic evolution, the data at sNN=130,200 GeV at various centralities in full pseudorapidity range are well described, and the charged-particle multiplicities are reproduced as functions of the number of participants. The energy dependence of the shape of the dNch/dη distribution is also described at various collision energies sNN=200,130,62.4 GeV in central collisions with same value of parameters except 19.6 GeV. The calculated rapidity distributions and yields for the charged pions and kaons in central Au+Au collisions at sNN=200 GeV are compared with experimental data of the BRAHMS Collaboration.
Chirally Symmetric but Confined Hadrons at Finite Density
NASA Astrophysics Data System (ADS)
Ya. Glozman, L.; Wagenbrunn, R. F.
At a critical finite chemical potential and low temperature QCD undergoes the chiral restoration phase transition. The folklore tradition is that simultaneously hadrons are deconfined and there appears the quark matter. We demonstrate that it is possible to have confined but chirally symmetric hadrons at a finite chemical potential and hence beyond the chiral restoration point at a finite chemical potential and low temperature there could exist a chirally symmetric matter consisting of chirally symmetric but confined hadrons. If it does happen in QCD, then the QCD phase diagram should be reconsidered with obvious implications for heavy ion programs and astrophysics.
NASA Astrophysics Data System (ADS)
Hoelbling, Christian; Zielinski, Christian
2016-07-01
We follow up on a suggestion by Adams and construct explicit domain wall fermion operators with staggered kernels. We compare different domain wall formulations, namely the standard construction as well as Boriçi's modified and Chiu's optimal construction, utilizing both Wilson and staggered kernels. In the process, we generalize the staggered kernels to arbitrary even dimensions and introduce both truncated and optimal staggered domain wall fermions. Some numerical investigations are carried out in the (1 +1 )-dimensional setting of the Schwinger model, where we explore spectral properties of the bulk, effective and overlap Dirac operators in the free-field case, on quenched thermalized gauge configurations and on smooth topological configurations. We compare different formulations using the effective mass, deviations from normality and violations of the Ginsparg-Wilson relation as measures of chirality.
Resurgence in quantum field theory: nonperturbative effects in the principal chiral model.
Cherman, Aleksey; Dorigoni, Daniele; Dunne, Gerald V; Ünsal, Mithat
2014-01-17
We explain the physical role of nonperturbative saddle points of path integrals in theories without instantons, using the example of the asymptotically free two-dimensional principal chiral model (PCM). Standard topological arguments based on homotopy considerations suggest no role for nonperturbative saddles in such theories. However, the resurgence theory, which unifies perturbative and nonperturbative physics, predicts the existence of several types of nonperturbative saddles associated with features of the large-order structure of the perturbation theory. These points are illustrated in the PCM, where we find new nonperturbative "fracton" saddle point field configurations, and suggest a quantum interpretation of previously discovered "uniton" unstable classical solutions. The fractons lead to a semiclassical realization of IR renormalons in the circle-compactified theory and yield the microscopic mechanism of the mass gap of the PCM.
Constituent Quarks and Gluons, Polyakov loop and the Hadron Resonance Gas Model ***
NASA Astrophysics Data System (ADS)
Megías, E.; Ruiz Arriola, E.; Salcedo, L. L.
2014-03-01
Based on first principle QCD arguments, it has been argued in [1] that the vacuum expectation value of the Polyakov loop can be represented in the hadron resonance gas model. We study this within the Polyakov-constituent quark model by implementing the quantum and local nature of the Polyakov loop [2, 3]. The existence of exotic states in the spectrum is discussed. Presented by E. Megías at the International Nuclear Physics Conference INPC 2013, 2-7 June 2013, Firenze, Italy.Supported by Plan Nacional de Altas Energías (FPA2011-25948), DGI (FIS2011-24149), Junta de Andalucía grant FQM-225, Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042), Spanish MINECO's Centro de Excelencia Severo Ochoa Program grant SEV-2012-0234, and the Juan de la Cierva Program.
Flavor-changing decays of the top quark in 5D warped models
NASA Astrophysics Data System (ADS)
Díaz-Furlong, Alfonso; Frank, Mariana; Pourtolami, Nima; Toharia, Manuel; Xoxocotzi, Reyna
2016-08-01
We study flavor-changing neutral current decays of the top quark in the context of general warped extra dimensions, where the five-dimensional (5D) metric is slightly modified from 5D anti-de Sitter (AdS5 ). These models address the Planck-electroweak hierarchies of the Standard Model and can obey all the low-energy flavor bounds and electroweak precision tests, while allowing the scale of new physics to be at the TeV level, and thus within the reach of the LHC at Run II. We perform the calculation of these exotic top decay rates for the case of a bulk Higgs, and thus include in particular the effect of the additional Kaluza-Klein (KK) Higgs modes running in the loops, along with the usual KK fermions and KK gluons.
Contrera, G. A.; Orsaria, M.; Scoccola, N. N.
2010-09-01
We study the phase diagram of strongly interacting matter in the framework of a nonlocal SU(2) chiral quark model which includes wave function renormalization and coupling to the Polyakov loop. Both nonlocal interactions based on the frequently used exponential form factor, and on fits to the quark mass and renormalization functions obtained in lattice calculations are considered. Special attention is paid to the determination of the critical points, both in the chiral limit and at finite quark mass. In particular, we study the position of the critical end point as well as the value of the associated critical exponents for different model parametrizations.
NASA Astrophysics Data System (ADS)
Chang, We-Fu; Ng, John N.; Wu, Jackson M. S.
2008-11-01
We study quark mass matrices in the Randall-Sundrum (RS) model with bulk symmetry SU(2)L×SU(2)R×U(1)B-L. The Yukawa couplings are assumed to be within an order of magnitude of each other, and perturbative. We find that quark mass matrices of the symmetrical form proposed by Koide et al. [Y. Koide, H. Nishiura, K. Matsuda, T. Kikuchi, and T. Fukuyama, Phys. Rev. D 66, 093006 (2002)PRVDAQ0556-282110.1103/PhysRevD.66.093006] can be accommodated in the RS framework with the assumption of hierarchyless Yukawa couplings, but not the Hermitian Fritzsch-type mass matrices. General asymmetrical mass matrices are also found which fit well simultaneously with the quark masses and the Cabibbo-Kobayashi-Maskawa matrix. Both left-handed (LH) and right-handed (RH) quark rotation matrices are obtained that allow analysis of flavor changing decay of both LH and RH top quarks. At a warped down scale of 1.65 TeV, the total branching ratio of t→Z+jets can be as high as ˜5×10-6 for symmetrical mass matrices and ˜2×10-5 for asymmetrical ones. This level of signal is within reach of the LHC.
Maxwell-Chern-Simons hydrodynamics for the chiral magnetic effect
Oezoender, Sener
2010-06-15
The rate of vacuum-changing topological solutions of the gluon field, sphalerons, is estimated to be large at the typical temperatures of heavy-ion collisions, particularly at the Relativistic Heavy Ion Collider. Such windings in the gluon field are expected to produce parity-odd bubbles, which cause separation of positively and negatively charged quarks along the axis of the external magnetic field. This chiral magnetic effect can be mimicked by Chern-Simons modified electromagnetism. Here we present a model of relativistic hydrodynamics including the effects of axial anomalies via the Chern-Simons term.
Chiral symmetry aspects in the open charm sector
NASA Astrophysics Data System (ADS)
Buchheim, T.; Hilger, T.; Kämpfer, B.
2016-01-01
QCD sum rules serve as tools to investigate changing hadronic properties in a hot and/or dense nuclear medium. The role of chiral symmetry breaking and restoration effects in a medium can be addressed also in the heavy-light meson sector. Thus, we consider Weinberg sum rules which refer to chiral partner mesons composed of a light and a heavy quark.
Dynamical chiral symmetry breaking and confinement with an infrared-vanishing gluon propagator
Roberts, C.D.; Hawes, F.T.; Williams, A.G.
1995-08-01
We have studied a model Dyson-Schwinger equation for the quark propagator, constructed using an Ansatz for the gluon propagator of the form D(q) {approximately} q{sup 2}/[(q{sup 2}){sup 2} + b{sup 4}] and two Ansatze for the quark-gluon vertex: the minimal Ball-Chiu and the modified form suggested by Curtis and Pennington. The aim was to determine whether such a form of the gluon propagator, which was suggested by a number of authors and which recent lattice simulations of QCD suggest may be plausible, can support dynamical chiral symmetry breaking and ensure quark confinement. The form of the gluon propagator at small space-like momenta is crucial to the nature of the strong interaction spectrum but is presently unknown and information gathered in such studies is invaluable in supporting or invalidating given hypotheses. It was found that there is a critical value of b = b{sub c} such that the model does not support dynamical chiral symmetry breaking for b > b{sub c}. Further, it was shown that this form of gluon propagator cannot confine quarks. As a consequence this form represents a physically unreasonable model. In addition, these results formed the basis for an invited presentation at a workshop on quantum infrared physics and will be published in the proceedings.
PQChPT with Staggered Sea and Valence Ginsparg-Wilson Quarks: Vector Meson Masses
Hovhannes R. Grigoryan; Anthony W. Thomas
2005-09-16
We consider partially quenched, mixed chiral perturbation theory with staggered sea and Ginsparg-Wilson valence quarks in order to extract a chiral-continuum extrapolation expression for the vector meson mass up to order O(a{sup 2}), at one-loop level. Based on general principles, we accomplish the task without explicitly constructing a sophisticated, heavy vector meson chiral Lagrangian.
NASA Astrophysics Data System (ADS)
Wang, Wenyu; Xiong, Zhao-Hua; Zhao, Xin-Yan
2016-09-01
In models with vector-like quark doublets, the mass matrices of up and down type quarks are related. Precise diagonalization of the mass matrices has become an obstacle in numerical studies. In this work we first propose a diagonalization method. As its application, in the Standard Model with one vector-like quark doublet we present the quark mass spectrum and Feynman rules for the calculation of B → Xsγ. We find that i) under the constraints of the CKM matrix measurements, the mass parameters in the bilinear term are constrained to a small value by the small deviation from unitarity; ii) compared with the fourth generation extension of the Standard Model, there is an enhancement to the B → Xsγ process in the contribution of vector-like quarks, resulting in a non-decoupling effect in such models. Supported by Natural Science Foundation of China (11375001) and Talents Foundation of Education Department of Beijing
Ji, C.R.
1999-04-01
This report details research progress and results obtained during the entire period of the research project. In compliance with grant requirements the Principal Investigator, Professor Chueng-Ryong Ji, has conducted a research program addressing theoretical investigations of hadron structure and reactions using quantum chromodynamic quark models. This Principal Investigator has devoted 50% of his time during the academic year and 100% of his time in the summer. This percent effort has continued during the entire period of the grant. The new, significant research results are briefly summarized in this report. Finally, full, detailed descriptions of completed work can be found in the project publications which are listed at the end of this technical report.
Relativistic Quark-Model Results for Baryon Ground and Resonant States
Plessas, W.; Melde, T.
2008-10-13
Latest results from a study of baryon ground and resonant states within relativistic constituent quark models are reported. After recalling some typical spectral properties, the description of ground states, especially with regard to the nucleon and hyperon electromagnetic structures, is addressed. In the following, recent covariant predictions for pion, eta, and kaon partial decay widths of light and strange baryon resonances below 2 GeV are summarized. These results exhibit a characteristic pattern that is distinct from nonrelativistic or relativized decay studies performed so far. Together with a detailed analysis of the spin, flavor, and spatial structures of the wave functions, it supports a new and extended classification scheme of baryon ground and resonant states into SU(3) flavor multiplets.
Gupta, R.
1994-12-31
This talk contains an analysis of quenched chiral perturbation theory and its consequences. The chiral behavior of a number of quantities such as the pion mass m{sub pi}{sup 2}, the Bernard-Golterman ratios R and {sub X}, the masses of nucleons, and the kaon B-parameter are examined to see if the singular terms induced by the additional Goldstone boson, {eta}{prime}, are visible in present data. The overall conclusion (different from that presented at the lattice meeting) of this analysis is that even though there are some caveats attached to the indications of the extra terms induced by {eta}{prime} loops, the standard expressions break down when extrapolating the quenched data with m{sub q} < m{sub s}/2 to physical light quarks. I then show that due to the single and double poles in the quenched {eta}{prime}, the axial charge of the proton cannot be calculated using the Adler-Bell-Jackiw anomaly condition. I conclude with a review of the status of the calculation of light quark masses from lattice QCD.
Wainer, I W; Doyle, T D; Fry, F S; Hamidzadeh, Z
1986-03-14
The mechanism of chiral recognition has been investigated for a series of enantiomeric cis-oxazolidines on a commercially available high-performance liquid chromatographic chiral stationary phase (HPLC-CSP). The oxazolidine molecules were synthesized through the condensation of ephedrine and ephedrine-related molecules with aromatic aldehydes. The resulting molecules are rigid five-membered rings whose configuration has been determined by proton magnetic resonance and single-crystal X-ray diffraction. The oxazolidines derived from the condensation of ephedrine and aldehydes containing a pi-basic moiety such as naphthaldehyde were resolved on the HPLC-CSP as were those oxazolidines synthesized by using a pi-acidic aldehyde such as p-nitrobenzaldehyde. However, there was a reversal in the elution order for the two types of oxazolidines. Oxazolidines resulting from the condensation of ephedrine and a pi-neutral aldehyde such as benzaldehyde were not resolved. The results of this study suggest a chiral recognition model based on the formation of diastereomeric solute-CSP complexes through a single attractive interaction and chiral discrimination resulting from the difference in steric fit. PMID:3700541
Chiral symmetry breaking revisited: the gap equation with lattice ingredients
Aguilar, Arlene C.
2011-05-23
We study chiral symmetry breaking in QCD, using as ingredients in the quark gap equation recent lattice results for the gluon and ghost propagators. The Ansatz employed for the quark-gluon vertex is purely non-Abelian, introducing a crucial dependence on the ghost dressing function and the quark-ghost scattering amplitude. The numerical impact of these quantities is considerable: the need to invoke confinement explicitly is avoided, and the dynamical quark masses generated are of the order of 300 MeV. In addition, the pion decay constant and the quark condensate are computed, and are found to be in good agreement with phenomenology.
Nathan Isgur
1991-07-01
Understanding the underlying quark and gluon structure of the nucleons is not only a fundamental objective in its own right, but also an essential first step in providing a basis within QCD for nuclear physics. In this article I present a pedagogical introduction to a simple but very successful nonrelativistic constituent quark model for baryons.
Chiral geometry in multiple chiral doublet bands
NASA Astrophysics Data System (ADS)
Zhang, Hao; Chen, Qibo
2016-02-01
The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with . The energy spectra, electromagnetic transition probabilities B(M1) and B(E2), angular momenta, and K-distributions are studied. It is demonstrated that the chirality still remains not only in the yrast and yrare bands, but also in the two higher excited bands when γ deviates from 30°. The chiral geometry relies significantly on γ, and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands. Supported by Plan Project of Beijing College Students’ Scientific Research and Entrepreneurial Action, Major State 973 Program of China (2013CB834400), National Natural Science Foundation of China (11175002, 11335002, 11375015, 11461141002), National Fund for Fostering Talents of Basic Science (NFFTBS) (J1103206), Research Fund for Doctoral Program of Higher Education (20110001110087) and China Postdoctoral Science Foundation (2015M580007)
Spin correlation and Majorana spectrum in chiral spin liquids in a decorated-honeycomb Kitaev model
NASA Astrophysics Data System (ADS)
Nasu, Joji; Motome, Yukitoshi
2016-02-01
Temperature evolution of the spin correlation and excitation spectrum is investigated for the Kitaev model defined on a decorated honeycomb lattice by using the quantum Monte Carlo simulation in the Majorana fermion representation. The ground state of this quantum spin model is given by two kinds of chiral spin liquids: one is topologically trivial with Abelian anyon excitations, and the other is topologically nontrivial with non-Abelian anyon excitations. While lowering temperature, the model exhibits several crossovers in the paramagnetic state, which originate from the fractionalization of quantum spins into Majorana fermions, in addition to a phase transition associated with time reversal symmetry breaking. We show that the spin correlation develops around the crossover temperatures, whereas it shows a slight change at the critical temperature, as in other Kitaev-type models. We also calculate the excitation spectrum in terms of Majorana fermions, and find that the excitation gap in the non-Abelian phase is fragile against thermal fluctuations of the Z2 fluxes, while that in the Abelian phase remains open.
NASA Astrophysics Data System (ADS)
Nagy, S.
2016-07-01
We construct the states and symmetries of N = 4 super-Yang-Mills by tensoring two N = 1 chiral multiplets and introducing two extra SUSY generators. This allows us to write the maximal N = 8 supergravity as four copies of the chiral multiplet. We extend this to higher dimensions and discuss applications to scattering amplitudes.
Chiral magnetic effect in condensed matter systems
Li, Qiang; Kharzeev, Dmitri E.
2016-12-01
The chiral magnetic effect is the generation of electrical current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum anomaly in relativistic field theory of chiral fermions. In the quark-gluon plasma, the axial anomaly induces topological charge changing transition that results in the generation of electrical current along the magnetic field. In condensed matter systems, the chiral magnetic effect was first predicted in the gapless semiconductors with tow energy bands having pointlike degeneracies. In addition, thirty years later after this prediction, the chiral magnetic effect was finally observed in the 3Dmore » Dirac/Weyl semimetals.« less
Quark-hadron phase transition in massive gravity
NASA Astrophysics Data System (ADS)
Atazadeh, K.
2016-11-01
We study the quark-hadron phase transition in the framework of massive gravity. We show that the modification of the FRW cosmological equations leads to the quark-hadron phase transition in the early massive Universe. Using numerical analysis, we consider that a phase transition based on the chiral symmetry breaking after the electroweak transition, occurred at approximately 10 μs after the Big Bang to convert a plasma of free quarks and gluons into hadrons.
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2007-02-01
We present a calculation of the quark distribution amplitudes (DAs), the Gegenbauer moments, and decay constants for {pi}, {rho}, K, and K* mesons using the light-front quark model. While the quark DA for {pi} is somewhat broader than the asymptotic one, that for {rho} meson is very close to the asymptotic one. The quark DAs for K and K* show asymmetric form due to the flavor SU(3)-symmetry breaking effect. The decay constants for the transversely polarized {rho} and K* mesons (f{sub {rho}}{sup T} and f{sub K*}{sup T}) as well as the longitudinally polarized ones (f{sub {rho}} and f{sub K*}) are also obtained. Our averaged values for f{sub V}{sup T}/f{sub V}, i.e. (f{sub {rho}}{sup T}/f{sub {rho}}){sub av}=0.78 and (f{sub K*}{sup T}/f{sub K*}){sub av}=0.84, are found to be consistent with other model predictions. Especially, our results for the decay constants are in good agreement with the SU(6) symmetry relation, f{sub {rho}}{sub (K*)}{sup T}=(f{sub {pi}}{sub (K)}+f{sub {rho}}{sub (K*)})/2.
Thimble regularization at work: From toy models to chiral random matrix theories
NASA Astrophysics Data System (ADS)
Di Renzo, F.; Eruzzi, G.
2015-10-01
We apply the Lefschetz thimble formulation of field theories to a couple of different problems. We first address the solution of a complex zero-dimensional ϕ4 theory. Although very simple, this toy model makes us appreciate a few key issues of the method. In particular, we will solve the model by a correct accounting of all the thimbles giving a contribution to the partition function and we will discuss a number of algorithmic solutions to simulate this (simple) model. We will then move to a chiral random matrix (CRM) theory. This is a somehow more realistic setting, giving us once again the chance to tackle the same couple of fundamental questions: How many thimbles contribute to the solution? How can we make sure that we correctly sample configurations on the thimble? Since the exact result is known for the observable we study (a condensate), we can verify that, in the region of parameters we studied, only one thimble contributes and that the algorithmic solution that we set up works well, despite its very crude nature. The deviation of results from phase quenched ones highlights that in a certain region of parameter space there is a quite important sign problem. In view of this, the success of our thimble approach is quite a significant one.
NASA Astrophysics Data System (ADS)
Varela, Solmar; Mujica, Vladimiro; Medina, Ernesto
2016-04-01
We derive a detailed analytical tight-binding (TB) model for a double helix emulating DNA with one type of nucleotide pair and a single oriented π orbital per base. The TB model incorporates both kinetic and intrinsic spin-orbit (ISO) contributions as well as Rashba-type interactions coupled to an external electric field along the axis of the double helix. The helical structure of the molecule renders the ISO first order in the interaction strength (in the meV range) as in carbon nanotubes. The coupling between the ISO and the chirality of the molecule is manifest in the effective coupling parameters while the Rashba coupling is only weakly dependent on structural chirality. A continuum model at half filling is derived where the dispersion is linear around the Fermi level. Spin transport can be completely solved in the case of ISO and the dominant Rashba type term. Spin selectivity is shown to exist for this minimal model (with features similar to recent experimental findings) when the double helix is biased and thus time reversal symmetry is broken. The model also display robustness toward scattering because of the chiral nature of the eigenstates.
Deconfinement Phase Transition and the Quark Condensate
Fischer, Christian S.
2009-07-31
We study the dual quark condensate as a signal for the confinement-deconfinement phase transition of QCD. This order parameter for center symmetry has been defined recently by Bilgici et al. within the framework of lattice QCD. In this work we determine the ordinary and the dual quark condensate with functional methods using a formulation of the Dyson-Schwinger equations for the quark propagator on a torus. The temperature dependence of these condensates serves to investigate the interplay between the chiral and deconfinement transitions of quenched QCD.
Optical properties of chiral nanotubes
NASA Astrophysics Data System (ADS)
Cecilia, Noguez; Román-Velázquez Carlos, E.; Ariadna, Sánchez; Montes Lilia, Meza
2004-03-01
A recent theoretical model [1] is applied to study the optical properties chiral nanostructures like carbon nanotubes. We calculate the Circular Dichroism (CD) spectra for carbon nanotubes with different chirality. The calculated CD spectra show features that allow us to distinguish between nanotubes with different indexes of chirality. Other nanostructures, like chiral fullerenes are also investigated.These results provide theoretical support for the quantification of chirality and its measurement, using the CD lineshapes of chiral. This work has been partly financed by CONACyT grant No. 36651-E and by DGAPA-UNAM grants No. IN104201. [1] C. E. Roman-Velazquez, et al., J. of Phys. Chem. B (Letter) 107, 12035 (2003)
Chair, Noureddine
2014-02-15
We have recently developed methods for obtaining exact two-point resistance of the complete graph minus N edges. We use these methods to obtain closed formulas of certain trigonometrical sums that arise in connection with one-dimensional lattice, in proving Scott’s conjecture on permanent of Cauchy matrix, and in the perturbative chiral Potts model. The generalized trigonometrical sums of the chiral Potts model are shown to satisfy recursion formulas that are transparent and direct, and differ from those of Gervois and Mehta. By making a change of variables in these recursion formulas, the dimension of the space of conformal blocks of SU(2) and SO(3) WZW models may be computed recursively. Our methods are then extended to compute the corner-to-corner resistance, and the Kirchhoff index of the first non-trivial two-dimensional resistor network, 2×N. Finally, we obtain new closed formulas for variant of trigonometrical sums, some of which appear in connection with number theory. -- Highlights: • Alternative derivation of certain trigonometrical sums of the chiral Potts model are given. • Generalization of these trigonometrical sums satisfy recursion formulas. • The dimension of the space of conformal blocks may be computed from these recursions. • Exact corner-to-corner resistance, the Kirchhoff index of 2×N are given.
NASA Astrophysics Data System (ADS)
Baskaran, G.
2003-08-01
Takada et al. have reported superconductivity in layered NaxCoO2yH2O (Tc≈5 K). We model a reference neutral CoO2 layer as an orbitally nondegenerate spin-1/2 antiferromagnetic Mott insulator on a triangular lattice and NaxCoO2yH2O as electron doped Mott insulators described by a t-J model. It is suggested that at optimal doping chiral spin fluctuations enhanced by the dopant dynamics lead to a gapful d-wave superconducting state. A chiral resonating valence bond (RVB) metal, a parity and time (PT) reversal violating state with condensed RVB gauge fields, with a possible weak ferromagnetism, and low temperature p-wave superconductivity are also suggested at higher dopings.
Quark-hadron phase transition in Brans-Dicke brane gravity
NASA Astrophysics Data System (ADS)
Atazadeh, K.; Ghezelbash, A. M.; Sepangi, H. R.
2011-04-01
A standard picture in cosmology has been emerging over the past decade in which a phase transition, associated with chiral symmetry breaking after the electroweak transition, has occurred at approximately 10-6 s after the Big Bang to convert a plasma of free quarks and gluons into hadrons. In this paper, we consider the quark-hadron phase transition in a Brans-Dicke brane world scenario within an effective model of QCD. We study the evolution of the physical quantities relevant to a quantitative description of the early universe, namely, the energy density, temperature and the scale factor before, during, and after the phase transition. We show that for different values of the Brans-Dicke coupling, ω, phase transition occurs and results in decreasing the effective temperature of the quark-gluon plasma and of the hadronic fluid. We then move on to consider the quark-hadron transition in the smooth crossover regime at high and low temperatures and show that such a transition occurs and results in decreasing the effective temperature of the quark-gluon plasma during the process of quark-hadron phase transition.
Staggered chiral perturbation theory in the two-flavor case
Du Xining
2010-07-01
I study two-flavor staggered chiral perturbation theory in the light pseudoscalar sector. The pion mass and decay constant are calculated through next-to-leading order in the partially-quenched case. In the limit where the strange quark mass is large compared to the light quark masses and the taste splittings, I show that the SU(2) staggered chiral theory emerges from the SU(3) staggered chiral theory, as expected. Explicit relations between SU(2) and SU(3) low energy constants and taste-violating parameters are given. The results are useful for SU(2) chiral fits to asqtad data and allow one to incorporate effects from varying strange quark masses.
Strangeness at high temperatures: from hadrons to quarks.
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
2013-08-23
Appropriate combinations of up to fourth order cumulants of net strangeness fluctuations and their correlations with net baryon number and electric charge fluctuations, obtained from lattice QCD calculations, have been used to probe the strangeness carrying degrees of freedom at high temperatures. For temperatures up to the chiral crossover, separate contributions of strange mesons and baryons can be well described by an uncorrelated gas of hadrons. Such a description breaks down in the chiral crossover region, suggesting that the deconfinement of strangeness takes place at the chiral crossover. On the other hand, the strangeness carrying degrees of freedom inside the quark gluon plasma can be described by a weakly interacting gas of quarks only for temperatures larger than twice the chiral crossover temperature. In the intermediate temperature window, these observables show considerably richer structures, indicative of the strongly interacting nature of the quark gluon plasma.
Classifying BPS states in supersymmetric gauge theories coupled to higher derivative chiral models
NASA Astrophysics Data System (ADS)
Nitta, Muneto; Sasaki, Shin
2015-06-01
We study N =1 supersymmetric gauge theories coupled with higher derivative chiral models in four dimensions in the off-shell superfield formalism. We solve the equation of motion for the auxiliary fields and find two distinct on-shell structures of the Lagrangian that we call the canonical and noncanonical branches characterized by zero and nonzero auxiliary fields, respectively. We classify Bogomol'nyi-Prasado-Sommerfield (BPS) states of the models in Minkowski and Euclidean spaces. In Minkowski space, we find Abelian and non-Abelian vortices, vortex lumps (or gauged lumps with fractional lump charges) as 1 /2 BPS states in the canonical branch, and higher derivative generalization of vortices and vortex-(BPS)baby Skyrmions (or gauged BPS baby Skyrmions with fractional baby Skyrme charges) as 1 /4 BPS states in the noncanonical branch. In four-dimensional Euclidean space, we find Yang-Mills instantons trapped inside a non-Abelian vortex, intersecting vortices, and intersecting vortex-(BPS)baby Skyrmions as 1 /4 BPS states in the canonical branch but no BPS states in the noncanonical branch other than those in the Minkowski space.
Magnetized strange quark matter in a mass-density-dependent model
NASA Astrophysics Data System (ADS)
Hou, Jia-Xun; Peng, Guang-Xiong; Xia, Cheng-Jun; Xu, Jian-Feng
2015-01-01
We investigate the properties of strange quark matter (SQM) in a strong magnetic field with quark confinement by the density dependence of quark masses considering the total baryon number conservation, charge neutrality and chemical equilibrium. It is found that an additional term should appear in the pressure expression to maintain thermodynamic consistency. At fixed density, the energy density of magnetized SQM varies with the magnetic field strength. By increasing the field strength an energy minimum exists located at about 6×1019 Gauss when the density is fixed at two times the normal nuclear saturation density.
Self-consistently thermodynamic treatment for strange quark matter in the effective mass bag model
NASA Astrophysics Data System (ADS)
Bao, Tmurbagan; Liu, Guang-Zhou; Zhao, En-Guang; Zhu, Ming-Feng
2008-12-01
In the framework of the effective mass bag model (EMBM) we have performed the thermodynamical treatment for strange quark matter (SQM) self-consistently, which overcomes the inconsistencies in the thermodynamical properties of the system. Because of the existence of the pressure extra term, the SQM equation of state (EOS) becomes stiffer comparing with the one for the original EMBM. It is interesting to find that in our treatment the SQM EOS is almost independent of the strong coupling constant g . In this case the SQM EOS seems to get back to the EOS for the original MIT bag model. However, this treatment still has influence on the EOS for hybrid star matter and the corresponding mass-radius relations. With the increase of the strong coupling constant g , the EOS for hybrid star matter gets obviously stiff. From our treatment we notice that the pressure extra term can make a hybrid star more compact than the one described in the original EMBM and this model is more suitable to describe the hybrid stars with small radii.
Non-perturbative QCD Modeling and Meson Physics
Nguyen, T.; Souchlas, N. A.; Tandy, P. C.
2009-04-20
Using a ladder-rainbow kernel previously established for light quark hadron physics, we explore the extension to masses and electroweak decay constants of ground state pseudoscalar and vector quarkonia and heavy-light mesons in the c- and b-quark regions. We make a systematic study of the effectiveness of a constituent mass concept as a replacement for a heavy quark dressed propagator for such states. The difference between vector and axial vector current correlators is explored within the same model to provide an estimate of the four quark chiral condensate and the leading distance scale for the onset of non-perturbative phenomena in QCD.
Non-perturbative QCD Modeling and Meson Physics
NASA Astrophysics Data System (ADS)
Nguyen, T.; Souchlas, N. A.; Tandy, P. C.
2009-04-01
Using a ladder-rainbow kernel previously established for light quark hadron physics, we explore the extension to masses and electroweak decay constants of ground state pseudoscalar and vector quarkonia and heavy-light mesons in the c- and b-quark regions. We make a systematic study of the effectiveness of a constituent mass concept as a replacement for a heavy quark dressed propagator for such states. The difference between vector and axial vector current correlators is explored within the same model to provide an estimate of the four quark chiral condensate and the leading distance scale for the onset of non-perturbative phenomena in QCD.
NASA Astrophysics Data System (ADS)
Suliman, FakhrEldin O.; Elbashir, Abdalla A.
2012-07-01
Using capillary electrophoresis baclofen (BF) enantiomers were separated only in the presence of β-cyclodextrin (βCD) as a chiral selector when added to the background electrolyte. Proton nuclear magnetic resonance and electrospray ionization mass spectrometry (ESI-MS) techniques were used to determine the structure of the BF-βCD inclusion complexes. From the MS data BF was found to form a 1:1 complex with α- and βCD, while the NMR data suggest location of the aromatic ring of BF into the cyclodextrin cavity. A molecular modeling study, using the semiempirical PM6 calculations was used to investigate the mechanism of enantiodifferentiation of BF with cyclodextrins. Optimization of the structures of the complexes by PM6 method indicated that separation is obtained in the presence of β-CD due to a large binding energy difference (ΔΔE) of 46.8 kJ mol-1 between S-BF-βCD and R-BF-βCD complexes. In the case of αCD complexes ΔΔE was 1.3 kJ mol-1 indicating poor resolution between the two enantiomers. Furthermore, molecular dynamic simulations show that the formation of more stable S-BF-βCD complex compared to R-BF-β-CD complex is primarily due to differences in intermolecular hydrogen bonding.
A Model Liquid Crystalline System Based on Rodlike Viruses with Tunable Chirality
NASA Astrophysics Data System (ADS)
Beller, Daniel; Barry, Edward; Dogic, Zvonimir
2009-03-01
Filamentous bacteriophages such as the fd virus have long been used as ideal model systems to investigate the phase behavior of suspensions of rodlike particles. We study the structure and phase behavior of a mutant, fd Y21M, and compare them to the properties of conventional fd wild-type (wt). These two viruses exhibit dramatically different phase behavior despite differing only by a single amino acid of the major coat protein pVIII. We find that this is attributable to significant differences in the flexibility of the viruses. Using the more rigid fd Y21M, we are able for the first time to quantitatively test the Onsager description of the isotropic-nematic phase transition of rigid rods. Even more surprising are the differences in the behavior of the cholesteric phase of fd Y21M and fd wt. While fd wt forms a cholesteric pitch with a left-handed helix, fd Y21M forms a cholesteric pitch with the opposite handedness. In addition, the magnitude of the cholesteric pitch changes by almost fivefold. Using mixtures of the two viruses, we are able to create liquid crystal systems with tunable control over the macroscopic chiral behavior.
Hill, Christopher S.; /UC, Santa Barbara
2004-12-01
The top quark, with its extraordinarily large mass (nearly that of a gold atom), plays a significant role in the phenomenology of EWSB in the Standard Model. In particular, the top quark mass when combined with the W mass constrains the mass of the as yet unobserved Higgs boson. Thus, a precise determination of the mass of the top quark is a principal goal of the CDF and D0 experiments. With the data collected thus far in Runs 1 and 2 of the Tevatron, CDF and D0 have measured the top quark mass in both the lepton+jets and dilepton decay channels using a variety of complementary experimental techniques. The author presents an overview of the most recent of the measurements.
Starosta, Krzysztof
2005-04-05
Nuclear chirality is a novel manifestation of spontaneous symmetry breaking resulting from an orthogonal coupling of angular momentum vectors in triaxial nuclei. Three perpendicular angular momenta can form two systems of opposite handedness; the time reversal operator, which reverses orientation of each of the angular momentum components, relates these two systems. The status of current experimental searches for chiral doubling of states, as well as recent progress on the theoretical side is reviewed.
Floss, H.G.
1994-12-01
This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.
Staggered heavy baryon chiral perturbation theory
Bailey, Jon A.
2008-03-01
Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms of O(m{sub {pi}}{sup 3}), which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms of O(a{sup 2}). The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in detail. The resulting chiral forms are appropriate to lattice results obtained with operators already in use and could be used to study the restoration of taste symmetry in the continuum limit. I assume that the fourth root of the fermion determinant can be incorporated in staggered chiral perturbation theory using the replica method.
Staggered heavy baryon chiral perturbation theory
NASA Astrophysics Data System (ADS)
Bailey, Jon A.
2008-03-01
Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms of O(mπ3), which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms of O(a2). The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in detail. The resulting chiral forms are appropriate to lattice results obtained with operators already in use and could be used to study the restoration of taste symmetry in the continuum limit. I assume that the fourth root of the fermion determinant can be incorporated in staggered chiral perturbation theory using the replica method.
NASA Astrophysics Data System (ADS)
Leutwyler, H.
2010-12-01
These lecture notes concern recent developments in our understanding of the low energy properties of QCD. Significant progress has been made on the lattice and the beautiful experimental results on the Ke4 and K3π decays, as well as those on pionic atoms also confirm the results obtained on the basis of Chiral Perturbation Theory. There is an exception: one of the precision experiments on Kμ3 decay is in flat contradiction with the Callan-Treiman relation. If confirmed, this would indicate physics beyond the Standard Model: right-handed quark couplings of the W-boson, for instance. Furthermore, I discuss two examples where the estimates of the effective coupling constants based on saturation by resonances appear to fail. In the second part, the progress made in extending the range of validity of the effective theory with dispersive methods is reviewed. In particular, I draw attention to an exact formula, which expresses the mass and width of a resonance in terms of observable quantities. The formula removes the ambiguities inherent in the analytic continuation from the real axis into the complex plane, which plagued previous determinations of the pole positions associated with broad resonances. In particular, it can now be demonstrated that the lowest resonance of QCD carries the quantum numbers of the vacuum.
Electroexcitation of the Δ(1232)32+ and Δ(1600)32+ in a light-front relativistic quark model
Aznauryan, Inna G.; Burkert, Volker D.
2015-09-30
Here, the magnetic-dipole form factor and the ratios REM and RSM for the γ* N → Δ(1232)3/2+ transition are predicted within light-front relativistic quark model up to photon virtuality Q2=12 GeV2. Furthermore, we predict the helicity amplitudes of the γ* N → Δ(1600)3/2+ transition assuming the Δ(1600)3/2+ is the first radial excitation of the ground state Delta(1232)3/2+.
Determination of the chiral condensate from QCD Dirac spectrum on the lattice
Fukaya, H.; Onogi, T.; Aoki, S.; Chiu, T. W.; Hashimoto, S.; Kaneko, T.; Yamada, N.; Noaki, J.
2011-04-01
We calculate the chiral condensate of QCD with 2, 2+1, and 3 flavors of sea quarks. Lattice QCD simulations are performed employing dynamical overlap fermions with up- and down-quark masses covering a range between 3 and 100 MeV. On L{approx}1.8-1.9 fm lattices at a lattice spacing {approx}0.11 fm, we calculate the eigenvalue spectrum of the overlap-Dirac operator. By matching the lattice data with the analytical prediction from chiral perturbation theory at the next-to-leading order, the chiral condensate in the massless limit of up and down quarks is determined.
Hadronic physics with domain-wall valence and improved staggered sea quarks
D. B. Renner; W. Schroers; R. Edwards; G. T. Fleming; Ph. Hagler; J. W. Negele; K. Orginos; A. V. Pochinski; D. Richards
2004-06-01
With the advent of chiral fermion formulations, the simulation of light valence quarks has finally become realistic for numerical simulations of lattice QCD. The simulation of light dynamical quarks, however, remains one of the major challenges and is still an obstacle to realistic simulations. We attempt to meet this challenge using a hybrid combination of Asqtad sea quarks and domain-wall valence quarks. Initial results for the proton form factor and the nucleon axial coupling are presented.
Phenomenology of heavy quark systems
Gilman, F.J.
1987-03-01
The spectroscopy of heavy quark systems is examined with regards to spin independent and spin dependent potentials. It is shown that a qualitative picture exists of the spin-independent forces, and that a semi-quantitative understanding exists for the spin-dependent effects. A brief review is then given of the subject of the decays of hadrons containing heavy quarks, including weak decays at the quark level, and describing corrections to the spectator model. (LEW)
Excitation rates of heavy quarks
NASA Astrophysics Data System (ADS)
Canal, C. A.; Santangelo, E. M.; Ducati, M. B.
1985-06-01
We obtain the production rates for c, b, and t quarks in deep-inelastic neutrino- (antineutrino-) nucleon interactions, in the standard six-quark model with left-handed couplings. The results are obtained with the most recent mixing parameters and we include a comparison between quark parametrizations. The excitations are calculated separately for each flavor, allowing the understanding of the role of threshold effects when considered through different rescaling variables.
Yang Bingfang; Han Jinzhong; Wang Lin; Wang Xuelei
2011-05-01
In the framework of the littlest Higgs model with T parity, we studied the contributions of the new particles to the top-quark pair production via e{sup +}e{sup -} collision at the International Linear Collider. We calculated the top-quark pair production cross section and found this process can generate significantly relative correction. The result may be a sensitive probe of the littlest Higgs model with T parity.
Effective Field Theories of Baryons and Mesons or, what do Quarks Do?.
NASA Astrophysics Data System (ADS)
Keaton, Gregory Lee
1995-01-01
This thesis is an attempt to understand the properties of the protons, pions and other hadrons in terms of their fundamental building blocks. In the first chapter, I review several of the approaches that have already been developed. The Nambu-Jona-Lasinio model offers the classic example of a derivation of meson properties from a quark Lagrangian. The chiral quark model encodes much of the intuition acquired in recent decades. I also discuss the non-linear sigma model, the Skyrme model, and the constituent quark model, which is one of the oldest and most successful models. In the constituent quark model, the constituent quark appears to be different from the "current" quark that appears in the fundamental QCD Lagrangian. Recently it was proposed that the constituent quark is a topological soliton. In chapter 2 I investigate this soliton, calculating its mass, radius, magnetic moment, color magnetic moment, and spin structure function. Within the approximations used, the magnetic moments and spin structure function cannot simultaneously be made to agree with the constituent quark model. Some discussion of what to expect from better approximations is included. In Chapter 3 I use a different plan of attack. Rather than trying to model the constituents of the baryon, I begin with an effective field theory of baryons and mesons, with couplings and masses that are simply determined phenomenologically. Meson loop corrections to baryon axial currents are then computed in the 1/N expansion. It is already known that the one -loop corrections are suppressed by a factor 1/N; here it is shown that the two-loop corrections are suppressed by 1/N^2. To leading order, these corrections are exactly the same as would be calculated in the constituent quark model. This method therefore offers a different approach to the constituent quark. The appendices give some calculational details omitted in the text, including the strange fractal-like behaviour encountered while integrating some
He, Guangliang.
1992-05-15
The Cloudy Quark Bag Model is extended from S-wave to P- and D-wave. The parameters of the model are determined by K{sup {minus}}p scattering cross section data, K{sup {minus}}p {yields}{Sigma}{pi}{pi}{pi} production data, K{sup {minus}}p threshold branching ratio data, and K{sup {minus}}p {yields}{Lambda}{pi}{pi}{pi} production data. The resonance structure of the {Lambda}(1405), {Sigma}(1385), and {Lambda}(1520) are studied in the model. The shift and width of kaonic hydrogen are calculated using the model.
Complex singularities in the quark propagator
Roberts, C.D.; Frank, M.R.
1995-08-01
The Dyson-Schwinger equation for the quark propagator is being studied in the rainbow approximation using a gluon propagator that incorporates asymptotic freedom and is an entire function. The gluon propagator has a number of parameters that may be varied in order to obtain a good description of low-energy pion observables; such as f{sub {pi}} and the {pi}-{pi} scattering lengths. This provides a direct means of relating hadronic observables to the form of the quark-quark interaction in the infrared and serves as an adjunct and extension of the separable Ansatz approach discussed above. It also provides a means of examining the pole structure of the quark propagator, which may hold the key to understanding quark confinement. The preliminary results are encouraging. It was demonstrated that it is possible to obtain a good description of pion observables in this approach. Further, when the strength of the quark-quark interaction in the infrared becomes larger than a given critical value, the pole in the quark propagator bifurcates into a pair of complex conjugate poles: m{sub q} = m{sub q}{sup R} {plus_minus} im{sub q}{sup I}, which is a signal of confinement. The interpretation in this case is of 1/m{sub q}{sup I} as the distance over which a quark may propagate before fragmenting. Further, there are indications from these studies that T{sub c}{sup D} < T{sub c}{sup {chi}}, where T{sub c}{sup D} is the critical temperature for deconfinement and T{sub c}{sup {chi}} is the critical temperature for chiral symmetry restoration; i.e., indications that deconfinement occurs at a lower temperature than chiral symmetry restoration. Available results from this work will be presented at the Washington meeting of the APS.
Skyrmions in Yang-Mills theories with massless adjoint quarks
Auzzi, R.; Bolognesi, S.; Shifman, M.
2008-06-15
Dynamics of SU(N{sub c}) Yang-Mills theories with N{sub f} adjoint Weyl fermions is quite different from that of SU(N{sub c}) gauge theories with fundamental quarks. The symmetry breaking pattern is SU(N{sub f}){yields}SO(N{sub f}). The corresponding sigma model supports Skyrmions whose microscopic identification is not immediately clear. We address this issue as well as the issue of the Skyrmion stability. The case of N{sub f}=2 had been considered previously. Here we discuss N{sub f}{>=}3. We discuss the coupling between the massless Goldstone bosons and massive composite fermions [with mass O(N{sub c}{sup 0})] from the standpoint of the low-energy chiral sigma model. We derive the Wess-Zumino-Novikov-Witten term and then determine Skyrmion statistics. We also determine their fermion number (mod 2) and observe an abnormal relation between the statistics and the fermion number. This explains the Skyrmion stability. In addition, we consider another microscopic theory--SO(N{sub c}) Yang-Mills with N{sub f} Weyl fermions in the vectorial representation--which has the same chiral symmetry breaking pattern and the same chiral Lagrangian. We discuss distinctive features of these two scenarios.
Potamianos, Karolos
2011-12-01
We present the recent results of top-quark physics using up to 6 fb{sup -1} of p{bar p} collisions analyzed by the CDF collaboration. The large number of top quark events analyzed, of the order of several thousands, allows stringent checks of the standard model predictions. Also, the top quark is widely believed to be a window to new physics. We present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.
Twist-3 T-odd fragmentation functions G⊥ and G˜⊥ in a spectator model
NASA Astrophysics Data System (ADS)
Yang, Yongliang; Lu, Zhun; Schmidt, Ivan
2016-10-01
We present a calculation of the twist-3 T-odd chiral-even fragmentation functions G⊥ and G˜⊥ using a spectator model. We consider the effect gluon exchange to calculate all necessary one-loop diagrams for the quark-quark and quark-gluon-quark correlation functions. We find that the gluon loops corrections generate non-zero contribution to these two fragmentation function. We numerically calculate their half-kT moments by integrating over the transverse momentum and also verify the equation of motion relation among G⊥, G˜⊥ and the Collins function.
Chiral Magnetic Effect in Heavy Ion Collisions
Liao, Jinfeng
2016-12-01
The Chiral Magnetic Effect (CME) is a remarkable phenomenon that stems from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. We show it is of fundamental importance to search for the CME in experiments. The heavy ion collisions provide a unique environment where a hot chiral-symmetric quark-gluon plasma is created, gluonic topological fluctuations generate chirality imbalance, and very strong magnetic fields |Β→|~m2π are present during the early stage of such collisions. Significant efforts have been made to look for CME signals in heavy ion collision experiments. Lastly, in this contribution we give a brief overview onmore » the status of such efforts.« less
Strange Quark Matter Status and Prospects
NASA Technical Reports Server (NTRS)
Sandweiss, J.
2004-01-01
The existence of quark states with more than three quarks is allowed in QCD. The stability of such quark matter states has been studied with lattice QCD and phenomenological bag models, but is not well constrained by theory. The addition of strange quarks to the system allows the quarks to be in lower energy states despite the additional mass penalty. There is additional stability from reduced Coulomb repulsion. SQM is expected to have a low Z/A. Stable or metastable massive multiquark states contain u, d, and s quarks.
Preon trinity—A schematic model of leptons, quarks and heavy vector bosons
NASA Astrophysics Data System (ADS)
Dugne, J.-J.; Fredriksson, S.; Hansson, J.
2002-10-01
Quarks, leptons and heavy vector bosons are suggested to be composed of stable spin-(1/2) preons, existing in three flavours, combined according to simple rules. Straightforward consequences of an SU(3) preon-flavour symmetry are the conservation of three lepton numbers, oscillations and decays between some neutrinos, and the mixing of the d and s quarks, as well as of the vector fields W0 and B0. We find a relation between the Cabibbo and Weinberg mixing angles, and predict new (heavy) leptons, quarks and vector bosons, some of which might be observable at the Fermilab Tevatron and the future CERN LHC. A heavy neutrino might even be visible in existing data from the CERN LEP facility.
NASA Astrophysics Data System (ADS)
Fischer, Tobias; Klähn, Thomas; Hempel, Matthias
2016-08-01
The thermodynamic bag model (tdBag) has been applied widely to model quark matter properties in both heavy-ion and astrophysics communities. Several fundamental physics aspects are missing in tdBag, e.g., dynamical chiral symmetry breaking (D χ SB) and repulsions due to the vector interaction are both included explicitly in the novel vBag quark matter model of Klähn and Fischer (Astrophys. J. 810, 134 (2015)). An important feature of vBag is the simultaneous D χ SB and deconfinement, where the latter links vBag to a given hadronic model for the construction of the phase transition. In this article we discuss the extension to finite temperatures and the resulting phase diagram for the isospin symmetric medium.
Wagdy, Hebatallah A; Hanafi, Rasha S; El-Nashar, Rasha M; Aboul-Enein, Hassan Y
2013-09-01
Pharmaceutical companies worldwide tend to apply chiral chromatographic separation techniques in their mass production strategy rather than asymmetric synthesis. The present work aims to investigate the predictability of chromatographic behavior of enantiomers using DryLab HPLC method development software, which is typically used to predict the effect of changing various chromatographic parameters on resolution in the reversed phase mode. Three different types of chiral stationary phases were tested for predictability: macrocyclic antibiotics-based columns (Chirobiotic V and T), polysaccharide-based chiral column (Chiralpak AD-RH), and protein-based chiral column (Ultron ES-OVM). Preliminary basic runs were implemented, then exported to DryLab after peak tracking was accomplished. Prediction of the effect of % organic mobile phase on separation was possible for separations on Chirobiotic V for several probes: racemic propranolol with 97.80% accuracy; mixture of racemates of propranolol and terbutaline sulphate, as well as, racemates of propranolol and salbutamol sulphate with average 90.46% accuracy for the effect of percent organic mobile phase and average 98.39% for the effect of pH; and racemic warfarin with 93.45% accuracy for the effect of percent organic mobile phase and average 99.64% for the effect of pH. It can be concluded that Chirobiotic V reversed phase retention mechanism follows the solvophobic theory. PMID:23775938
Heavy-light semileptonic decays in staggered chiral perturbation theory
NASA Astrophysics Data System (ADS)
Aubin, C.; Bernard, C.
2007-07-01
We calculate the form factors for the semileptonic decays of heavy-light pseudoscalar mesons in partially quenched staggered chiral perturbation theory (SχPT), working to leading order in 1/mQ, where mQ is the heavy-quark mass. We take the light meson in the final state to be a pseudoscalar corresponding to the exact chiral symmetry of staggered quarks. The treatment assumes the validity of the standard prescription for representing the staggered “fourth-root trick” within SχPT by insertions of factors of 1/4 for each sea-quark loop. Our calculation is based on an existing partially quenched continuum chiral perturbation theory calculation with degenerate sea quarks by Bećirević, Prelovsek, and Zupan, which we generalize to the staggered (and nondegenerate) case. As a byproduct, we obtain the continuum partially quenched results with nondegenerate sea quarks. We analyze the effects of nonleading chiral terms, and find a relation among the coefficients governing the analytic valence mass dependence at this order. Our results are useful in analyzing lattice computations of form factors B→π and D→K, when the light quarks are simulated with the staggered action.
Transition State Models for Understanding the Origin of Chiral Induction in Asymmetric Catalysis.
Sunoj, Raghavan B
2016-05-17
In asymmetric catalysis, a chiral catalyst bearing chiral center(s) is employed to impart chirality to developing stereogenic center(s). A rich and diverse set of chiral catalysts is now available in the repertoire of synthetic organic chemistry. The most recent trends point to the emergence of axially chiral catalysts based on binaphthyl motifs, in particular, BINOL-derived phosphoric acids and phosphoramidites. More fascinating ideas took shape in the form of cooperative multicatalysis wherein organo- and transition-metal catalysts are made to work in concert. At the heart of all such manifestations of asymmetric catalysis, classical or contemporary, is the stereodetermining transition state, which holds a perennial control over the stereochemical outcome of the catalytic process. Delving one step deeper, one would find that the origin of the stereoselectivity is delicately dependent on the relative stabilization of one transition state, responsible for the formation of the predominant stereoisomer, over the other transition state for the minor stereoisomer. The most frequently used working hypothesis to rationalize the experimentally observed stereoselectivity places an undue emphasis on steric factors and tends to regard the same as the origin of facial discrimination between the prochiral faces of the reacting partners. In light of the increasing number of asymmetric catalysts that rely on hydrogen bonding as well as other weak non-covalent interactions, it is important to take cognizance of the involvement of such interactions in the sterocontrolling transition states. Modern density functional theories offer a pragmatic and effective way to capture non-covalent interactions in transition states. Aided by the availability of such improved computational tools, it is quite timely that the molecular origin of stereoselectivity is subjected to more intelligible analysis. In this Account, we describe interesting molecular insights into the stereocontrolling
NASA Astrophysics Data System (ADS)
Mekki-Berrada, Ali
Bringing closer phospholipids each other on a bilayer of liposome, causes their rotation around their fatty acids axis, generating a force which brings closer the two sheets of the bilayer. In this theoretical study I show that for getting the greater cohesion of the liposome, by these forces, the serine in the hydrophilic head must have a L chirality. In the case where the hydrophilic head is absent amino acids with L chirality could contribute to this cohesion by taking the place of L-serine. Some coenzymes having a configuration similar to ethanolamine may also contribute. This is the case of pyridoxamine, thiamine and tetrahydrofolic acid. The grouping of amino acids of L chirality and pyridoxamine on the wall could initialize the prebiotic metabolism of these L amino acids only. This would explain the origin of the homo-chirality of amino acids in living world. Furthermore I show that in the hydrophilic head, the esterification of glycerol-phosphate by two fatty acids go through the positioning of dihydroxyacetone-phosphate and L-glyceraldehyde-3-phosphate, but not of D-glyceraldehyde-3-phosphate, prior their hydrogenation to glycerol-3- phosphate. The accumulation of D-glyceraldehyde-3-phosphate in the cytoplasm displace the thermodynamic equilibria towards the synthesis of D-dATP from D-glyceraldehyde-3-phosphate, acetaldehyde and prebiotic adenine, a reaction which does not require a coenzyme in the biotic metabolism. D-dATP and thiamine, more prebiotic metabolism of L-amino acids on the wall, would initialize D-pentoses phosphate and D-nucleotides pathways from the reaction of D-glyceraldehyde-3-phosphate + dihydroxyacetone-phosphate + prebiotic nucleic bases. The exhaustion of the prebiotic glyceraldehyde (racemic) and the nascent biotic metabolism dominated by D-glyceraldehyde-3-phosphate, would explain the origin of homo-chirality of sugars in living world. References: http://en.wikiversity.org/wiki/Prebiotic_chirality
Implications of the Oklo Phenomenon in a Chiral Approach to Nuclear Matter
NASA Astrophysics Data System (ADS)
Davis, Edward D.
2015-09-01
It has been customary to use data from the Oklo natural nuclear reactor to place bounds on the change that has occurred in the electromagnetic fine structure constant α over the last 2 billion years. Alternatively, an analysis could be based on a recently proposed expression for shifts in resonance energies which relates them to changes in both α and the average m q of the u and d current quark masses, and which makes explicit the dependence on mass number A and atomic number Z. (Recent model independent results on hadronic -terms suggest sensitivity to the strange quark mass is negligible.) The most sophisticated analysis, to date, of the quark mass term invokes a calculation of the nuclear mean-field within the Walecka model of quantum hadrodynamics. We comment on this study and consider an alternative in which the link to low-energy quantum chromodynamics and its pattern of chiral symmetry-breaking is more readily discernible. Specifically, we investigate the sensitivity to changes in the pion mass of a single nucleon potential determined by an in-medium chiral perturbation theory (PT) calculation which includes virtual -excitations. Subject to some reasonable assumptions about low-energy constants, we confirm that the m q -contribution to resonance shifts is enhanced by a factor of 10 or so relative to the -term and deduce that the Oklo data for Sm imply that.
Thermodynamics of (2+1)-flavor QCD: Confronting models with lattice studies
Schaefer, B.-J.; Wagner, M.; Wambach, J.
2010-04-01
The Polyakov-quark-meson model, which combines chiral as well as deconfinement aspects of strongly interacting matter, is introduced for three light quark flavors. An analysis of the chiral and deconfinement phase transition of the model and its thermodynamics at finite temperatures is given. Three different forms of the effective Polyakov-loop potential are considered. The findings of the 2+1 flavor model investigations are compared to corresponding recent QCD lattice simulations of the RBC-Bielefeld, HotQCD and Wuppertal-Budapest collaborations. The influence of the heavier quark masses, which are used in the lattice calculations, is taken into account. In the transition region the bulk thermodynamics of the Polyakov-quark-meson model agrees well with the lattice data.
Power counting regime of chiral effective field theory and beyond.
Hall, J. M.M.; Leinweber, D. B.; Young, R. D.; Physics; Univ. of Adelaide
2010-08-10
Chiral effective field theory ({chi}EFT) complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of {chi}EFT, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory ({chi}PT) beyond the PCR are reported.
Power counting regime of chiral effective field theory and beyond
Hall, J. M. M.; Leinweber, D. B.; Young, R. D.
2010-08-01
Chiral effective field theory ({chi}EFT) complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of {chi}EFT, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory ({chi}PT) beyond the PCR are reported.
Han Xiaofang; Wang Lei; Yang Jinmin
2009-07-01
In the littlest Higgs model with T-parity (LHT) the newly introduced mirror quarks have flavor-changing couplings with the standard model (SM) quarks and may enhance the flavor-changing neutral-current (FCNC) top-quark interactions which are extremely suppressed in the SM. In this work we perform a comprehensive study for the contributions of these mirror fermions to various top-quark FCNC decays and productions at the LHC, which includes the decays t{yields}cV (V=g, {gamma}, Z), t{yields}cgg and the productions proceeding through the parton processes cg{yields}t, gg{yields}tc, cg{yields}tg, cg{yields}t{gamma} and cg{yields}tZ. We find that although these FCNC processes can be greatly enhanced by the LHT contributions, they are hardly accessible at the LHC. Therefore, the LHT model may not cause the FCNC problem in the top-quark sector if the top-quark property is proved to be SM-like at the LHC.
NASA Astrophysics Data System (ADS)
Friedman, J. I.
2001-01-01
In the period following World War II, there was a rapid development of particle physics. With the construction of synchrotrons and the development of detector technology, many new particles were discovered and the systematics of their interactions investigated. The invention of the bubble chamber played an especially important role in uncovering the rich array of hadrons that were discovered in this period.In 1961 Murray Gell-Mann [1] and Yuval Ne'eman [2] independently introduced a classification scheme, based on SU(3) symmetry, which placed hadrons into families on the basis of spin and parity. Like the periodic table for the elements, this scheme was predictive as well as descriptive, and various hadrons, such as the - , were predicted within this framework and were later discovered.In 1964 Gell-Mann [3] and George Zweig [4] independently proposed quarks as the building blocks of hadrons as a way of generating the SU(3) classification scheme. When the quark model was first proposed, it postulated three types of quarks: up (u), down (d), and strange (s), with charges 2/3, - 1/3, and - 1/3 respectively. Each of these was hypothesized to be a spin1/2 particle. In this model the nucleon (and all other baryons) is made up of three quarks, and each meson consists of a quark and an antiquark. For example, as the proton and neutron both have ero strangeness, they are (u,u,d) and (d,d,u) systems respectively.
Aznauryan Inna, Burkert Volker
2012-05-01
We utilize a light-front relativistic quark model (LF RQM) to predict the 3q core contribution to the electroexcitation amplitudes for the {Delta}(1232)P{sub 33}, N(1440)P{sub 11}, N(1520)D{sub 13}, and N(1535)S{sub 11} up to Q{sup 2} = 12 GeV{sup 2}. The parameters of the model have been specified via description of the nucleon electromagnetic form factors in the approach that combines 3q and pion-cloud contributions in the LF dynamics.
NASA Astrophysics Data System (ADS)
Allen, P.; Grunfeld, A. G.; Scoccola, N. N.
2015-10-01
The influence of intense magnetic fields on the behavior of color superconducting cold quark matter is investigated using an SU(2 ) f Nambu-Jona-Lasinio-type model for which a novel regulation scheme is introduced. In such a scheme the contributions which are explicitly dependent on the magnetic field turn out to be finite and, thus, do not require to be regularized. As a result of this, nonphysical oscillations that might arise in the alternative regularization schemes previously used in the literature are naturally removed. In this way, a clearer interpretation of the physical oscillations is possible. The sensitivity of our results to the model parametrization is analyzed.
Chiral dynamics and partonic structure at large transverse distances
Strikman, M.; Weiss, C.
2009-12-30
In this paper, we study large-distance contributions to the nucleon’s parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x≲M_{π}/M_{N} and transverse distances b~1/M_{π}. We calculate this component using phenomenological pion exchange with a physical lower limit in b (the transverse “core” radius estimated from the nucleon’s axial form factor, R_{core}=0.55 fm) and demonstrate its universal character. This formulation preserves the basic picture of the “pion cloud” model of the nucleon’s sea quark distributions, while restricting its application to the region actually governed by chiral dynamics. It is found that (a) the large-distance component accounts for only ~1/3 of the measured antiquark flavor asymmetry d¯-u¯ at x~0.1; (b) the strange sea quarks s and s¯ are significantly more localized than the light antiquark sea; (c) the nucleon’s singlet quark size for x<0.1 is larger than its gluonic size, (b^{2})_{q+q¯}>(b^{2})_{g}, as suggested by the t-slopes of deeply-virtual Compton scattering and exclusive J/ψ production measured at HERA and FNAL. We show that our approach reproduces the general N_{c}-scaling of parton densities in QCD, thanks to the degeneracy of N and Δ intermediate states in the large-N_{c} limit. Finally, we also comment on the role of pionic configurations at large longitudinal distances and the limits of their applicability at small x.
Why quarks cannot be fundamental particles
NASA Astrophysics Data System (ADS)
Kalman, C. S.
2005-05-01
Many reasons why quarks should be considered composite particles are found in the book Preons by D'Souza and Kalman. One reason not found in the book is that all the quarks except for the u quark decay. The electron and the electron neutrino do not decay. A model of fundamental particles based upon the weak charge is presented.
Taşdemir, Demet; Karaküçük-İyidoğan, Ayşegül; Ulaşli, Mustafa; Taşkin-Tok, Tuğba; Oruç-Emre, Emİne Elçİn; Bayram, Hasan
2015-02-01
A series of new chiral thiosemicarbazones derived from homochiral amines in both enantiomeric forms were synthesized and evaluated for their in vitro antiproliferative activity against A549 (human alveolar adenocarcinoma), MCF-7 (human breast adenocarcinoma), HeLa (human cervical adenocarcinoma), and HGC-27 (human stomach carcinoma) cell lines. Some of compounds showed inhibitory activities on the growth of cancer cell lines. Especially, compound exhibited the most potent activity (IC50 4.6 μM) against HGC-27 as compared with the reference compound, sindaxel (IC50 10.3 μM), and could be used as a lead compound to search new chiral thiosemicarbazone derivatives as antiproliferative agents. PMID:25399965
Taşdemir, Demet; Karaküçük-İyidoğan, Ayşegül; Ulaşli, Mustafa; Taşkin-Tok, Tuğba; Oruç-Emre, Emİne Elçİn; Bayram, Hasan
2015-02-01
A series of new chiral thiosemicarbazones derived from homochiral amines in both enantiomeric forms were synthesized and evaluated for their in vitro antiproliferative activity against A549 (human alveolar adenocarcinoma), MCF-7 (human breast adenocarcinoma), HeLa (human cervical adenocarcinoma), and HGC-27 (human stomach carcinoma) cell lines. Some of compounds showed inhibitory activities on the growth of cancer cell lines. Especially, compound exhibited the most potent activity (IC50 4.6 μM) against HGC-27 as compared with the reference compound, sindaxel (IC50 10.3 μM), and could be used as a lead compound to search new chiral thiosemicarbazone derivatives as antiproliferative agents.
Top Quark Physics at the Tevatron
Deliot, Frederic; Glenzinski, Douglas A.; /Fermilab
2010-10-01
The authors review the field of top-quark physics with an emphasis on experimental techniques. The role of the top quark in the Standard Model of particle physics is summarized and the basic phenomenology of top-quark production and decay is introduced. They discuss how contributions from physics beyond the Standard model could affect the top-quark properties or event samples. The many measurements made at the Fermilab Tevatron, which test the Standard model predictions or probe for direct evidence of new physics using the top-quark event samples, are reviewed here.
An explicit SU(12) family and flavor unification model with natural fermion masses and mixings
Albright, Carl H.; Feger, Robert P.; Kephart, Thomas W.
2012-07-01
We present an SU(12) unification model with three light chiral families, avoiding any external flavor symmetries. The hierarchy of quark and lepton masses and mixings is explained by higher dimensional Yukawa interactions involving Higgs bosons that contain SU(5) singlet fields with VEVs about 50 times smaller than the SU(12) unification scale. The presented model has been analyzed in detail and found to be in very good agreement with the observed quark and lepton masses and mixings.
Mechanism of chirality conversion by periodic change of temperature: Role of chiral clusters
NASA Astrophysics Data System (ADS)
Katsuno, Hiroyasu; Uwaha, Makio
2016-01-01
By grinding crystals in a solution, the chirality of crystal structure (and the molecular chirality for the case of chiral molecules as well) can be converted, and the cause of the phenomenon is attributed to crystal growth with chiral clusters. We show that the recently found chirality conversion with a periodic change of temperature can also be explained by crystal growth with chiral clusters. With the use of a generalized Becker-Döring model, which includes enantio-selective incorporation of small chiral clusters to large solid clusters, the change of cluster distribution and the mass flow between clusters are studied. The chiral clusters act as a reservoir to pump out the minority species to the majority, and the exponential amplification of the enantiomeric excess found in the experiment is reproduced in the numerical calculation.
Hierarchical chirality transfer in the growth of Towel Gourd tendrils
NASA Astrophysics Data System (ADS)
Wang, Jian-Shan; Wang, Gang; Feng, Xi-Qiao; Kitamura, Takayuki; Kang, Yi-Lan; Yu, Shou-Wen; Qin, Qing-Hua
2013-10-01
Chirality plays a significant role in the physical properties and biological functions of many biological materials, e.g., climbing tendrils and twisted leaves, which exhibit chiral growth. However, the mechanisms underlying the chiral growth of biological materials remain unclear. In this paper, we investigate how the Towel Gourd tendrils achieve their chiral growth. Our experiments reveal that the tendrils have a hierarchy of chirality, which transfers from the lower levels to the higher. The change in the helical angle of cellulose fibrils at the subcellular level induces an intrinsic torsion of tendrils, leading to the formation of the helical morphology of tendril filaments. A chirality transfer model is presented to elucidate the chiral growth of tendrils. This present study may help understand various chiral phenomena observed in biological materials. It also suggests that chirality transfer can be utilized in the development of hierarchically chiral materials having unique properties.
Hierarchical chirality transfer in the growth of Towel Gourd tendrils.
Wang, Jian-Shan; Wang, Gang; Feng, Xi-Qiao; Kitamura, Takayuki; Kang, Yi-Lan; Yu, Shou-Wen; Qin, Qing-Hua
2013-01-01
Chirality plays a significant role in the physical properties and biological functions of many biological materials, e.g., climbing tendrils and twisted leaves, which exhibit chiral growth. However, the mechanisms underlying the chiral growth of biological materials remain unclear. In this paper, we investigate how the Towel Gourd tendrils achieve their chiral growth. Our experiments reveal that the tendrils have a hierarchy of chirality, which transfers from the lower levels to the higher. The change in the helical angle of cellulose fibrils at the subcellular level induces an intrinsic torsion of tendrils, leading to the formation of the helical morphology of tendril filaments. A chirality transfer model is presented to elucidate the chiral growth of tendrils. This present study may help understand various chiral phenomena observed in biological materials. It also suggests that chirality transfer can be utilized in the development of hierarchically chiral materials having unique properties. PMID:24173107
Hierarchical chirality transfer in the growth of Towel Gourd tendrils
Wang, Jian-Shan; Wang, Gang; Feng, Xi-Qiao; Kitamura, Takayuki; Kang, Yi-Lan; Yu, Shou-Wen; Qin, Qing-Hua
2013-01-01
Chirality plays a significant role in the physical properties and biological functions of many biological materials, e.g., climbing tendrils and twisted leaves, which exhibit chiral growth. However, the mechanisms underlying the chiral growth of biological materials remain unclear. In this paper, we investigate how the Towel Gourd tendrils achieve their chiral growth. Our experiments reveal that the tendrils have a hierarchy of chirality, which transfers from the lower levels to the higher. The change in the helical angle of cellulose fibrils at the subcellular level induces an intrinsic torsion of tendrils, leading to the formation of the helical morphology of tendril filaments. A chirality transfer model is presented to elucidate the chiral growth of tendrils. This present study may help understand various chiral phenomena observed in biological materials. It also suggests that chirality transfer can be utilized in the development of hierarchically chiral materials having unique properties. PMID:24173107
Larkin-Ovchinnikov-Fulde-Ferrell state in two-color quark matter
Fukushima, Kenji; Iida, Kei
2007-09-01
We explore the phase structure of two-color and two-flavor QCD in the space of the quark chemical potential {mu}{sub q} and the isospin chemical potential {mu}{sub I}. Using a mean-field model we calculate the chiral and diquark condensates, {sigma} and {delta}, self-consistently. In weak coupling and in the chiral limit, we confirm the interval of the isospin chemical potential, 0.71{delta}{sub 0}<{mu}{sub I}<0.75{delta}{sub 0}, in which a single plane-wave Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase is favored over isotropic superfluidity and normal quark matter. The LOFF window becomes slightly wider at high density. For stronger coupling with nonzero quark mass, which is relevant to currently available numerical simulations in lattice two-color QCD, the single plane-wave LOFF phase appears only at sufficiently high density. The prediction obtained for the LOFF region could be tested with lattice since we can prove that the present system is free from the fermion sign problem. We draw the energy landscape on which local minima corresponding to the isotropic superfluid phase and the LOFF phase and a local maximum corresponding to the gapless phase are manifest. Our results clearly illustrate the path from the unstable gapless phase down to the LOFF phase.
Chirality effect in disordered graphene ribbon junctions
NASA Astrophysics Data System (ADS)
Long, Wen
2012-05-01
We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.
Micropatterning of cells reveals chiral morphogenesis
2013-01-01
Invariant left-right (LR) patterning or chirality is critical for embryonic development. The loss or reversal of LR asymmetry is often associated with malformations and disease. Although several theories have been proposed, the exact mechanism of the initiation of the LR symmetry has not yet been fully elucidated. Recently, chirality has been detected within single cells as well as multicellular structures using several in vitro approaches. These studies demonstrated the universality of cell chirality, its dependence on cell phenotype, and the role of physical boundaries. In this review, we discuss the theories for developmental LR asymmetry, compare various in vitro cell chirality model systems, and highlight possible roles of cell chirality in stem cell differentiation. We emphasize that the in vitro cell chirality systems have great promise for helping unveil the nature of chiral morphogenesis in development. PMID:23672821
NASA Astrophysics Data System (ADS)
Kahana, D. E.; Milana, J.
1987-07-01
A perturbative QCD calculation of gluon exchange corrections to the cranking moment of inertia of the chiral bag model is done using the full time-dependent cavity propagators. Cranking is used to construct the nucleon and delta states and a value of the effective strong coupling constant is extracted by fitting the empirical Δ N mass splitting. The MIT bag limit (large bag radius) of the chiral bag model is also examined.
Ayala, Alejandro; Bashir, Adnan; Raya, Alfredo; Sanchez, Angel
2009-08-01
Working in the linear sigma model with quarks, we compute the finite-temperature effective potential in the presence of a weak magnetic field, including the contribution of the pion ring diagrams and considering the sigma as a classical field. In the approximation where the pion self-energy is computed perturbatively, we show that there is a region of the parameter space where the effect of the ring diagrams is to preclude the phase transition from happening. Inclusion of the magnetic field has small effects that however become more important as the system evolves to the lowest temperatures allowed in the analysis.
Dynamical study of the X(3915) as a D*D* bound state in a quark model
Yang Youchang; Ping Jialun
2010-06-01
Considering the coupling of color 1 x 1 and 8 x 8 structures, we calculate the energy of the newly observed X(3915) as an S-wave D*D* state in the Bhaduri, Cohler, and Nogami quark model by the Gaussian expansion method. Because of the color coupling, the bound state of D*D* with J{sup PC}=0{sup ++} is found, which is well consonant with the experimental data of the X(3915). The bound states of B*B* with J{sup PC}=0{sup ++} and 2{sup ++} are also predicted in this work.
Transverse Force on Quarks in DIS
Burkardt, Matthias
2009-01-01
The $x^2$-moment of the twist-3 polarized parton distribution $g_2(x)$ is related to the transverse force acting on the active quark in deep-inelastic scattering off a transversely polarized nucleon immediately after it has absorbed the virtual photon. Lattice calculations of the corresponding matrix element as well as experimental measurements of $g_2(x)$ are used to estimate sign and magnitude of this force. Similarly, the $x^2$-moment of the chirally odd twist-3 unpolarized parton distribution $e(x)$ can be related to the transverse force experienced by a transversely polarized quark ejected from a transversely polarized nucleon.
Chiral symmetry restoration versus deconfinement in heavy-ion collisions at high baryon density
NASA Astrophysics Data System (ADS)
Cassing, W.; Palmese, A.; Moreau, P.; Bratkovskaya, E. L.
2016-01-01
We study the production of strange hadrons in nucleus-nucleus collisions from 4 to 160 A GeV within the parton-hadron-string dynamics (PHSD) transport approach that is extended to incorporate essentials aspects of chiral symmetry restoration (CSR) in the hadronic sector (via the Schwinger mechanism) on top of the deconfinement phase transition as implemented in PHSD. Especially the K+/π+ and the (Λ +Σ0) /π- ratios in central Au+Au collisions are found to provide information on the relative importance of both transitions. The modeling of chiral symmetry restoration is driven by the pion-nucleon Σ term in the computation of the quark scalar condensate that serves as an order parameter for CSR and also scales approximately with the effective quark masses ms and mq. Furthermore, the nucleon scalar density ρs, which also enters the computation of
, is evaluated within the nonlinear σ -ω model which is constrained by Dirac-Brueckner calculations and low-energy heavy-ion reactions. The Schwinger mechanism (for string decay) fixes the ratio of strange to light quark production in the hadronic medium. We find that above ˜80 A GeV the reaction dynamics of heavy nuclei is dominantly driven by partonic degrees of freedom such that traces of the chiral symmetry restoration are hard to identify. Our studies support the conjecture of "quarkyonic matter" in heavy-ion collisions from about 5 to 40 A GeV and provide a microscopic explanation for the maximum in the K+/π+ ratio at about 30 A GeV, which only shows up if a transition to partonic degrees of freedom is incorporated in the reaction dynamics and is discarded in the traditional hadron-string models.
Two-flavor QCD simulation with exact chiral symmetry
Aoki, S.; Fukaya, H.; Hashimoto, S.; Kaneko, T.; Yamada, N.; Ishikawa, K-I.; Okawa, M.; Kanaya, K.; Matsufuru, H.; Okamoto, M.; Onogi, T.; Ukawa, A; Yoshie, T.
2008-07-01
We perform numerical simulations of lattice QCD with two flavors of dynamical overlap quarks, which have exact chiral symmetry on the lattice. While this fermion discretization is computationally demanding, we demonstrate the feasibility to simulate reasonably large and fine lattices by a careful choice of the lattice action and algorithmic improvements. Our production runs are carried out on a 16{sup 3}x32 lattice at a single lattice spacing around 0.12 fm. We explore the sea quark mass region down to m{sub s}/6, where m{sub s} is the physical strange quark mass, for a good control of the chiral extrapolation in future calculations of physical observables. We describe in detail our setup and algorithmic properties of the production simulations and present results for the static quark potential to fix the lattice scale and the locality of the overlap operator.
Quark mass functions and pion structure in Minkowski space
Biernat, Elmer P.; Gross, Franz L.; Pena, Maria Teresa; Stadler, Alfred
2014-03-01
We present a study of the dressed quark mass function and the pion structure in Minkowski space using the Covariant Spectator Theory (CST). The quark propagators are dressed with the same kernel that describes the interaction between different quarks. We use an interaction kernel in momentum space that is a relativistic generalization of the linear confining q-qbar potential and a constant potential shift that defines the energy scale. The confining interaction has a Lorentz scalar part that is not chirally invariant by itself but decouples from the equations in the chiral limit and therefore allows the Nambu--Jona-Lasinio (NJL) mechanism to work. We adjust the parameters of our quark mass function calculated in Minkowski-space to agree with LQCD data obtained in Euclidean space. Results of a calculation of the pion electromagnetic form factor in the relativistic impulse approximation using the same mass function are presented and compared with experimental data.
Phase diagram and critical end point for strongly interacting quarks.
Qin, Si-xue; Chang, Lei; Chen, Huan; Liu, Yu-xin; Roberts, Craig D
2011-04-29
We introduce a method based on chiral susceptibility, which enables one to draw a phase diagram in the chemical-potential-temperature plane for strongly interacting quarks whose interactions are described by any reasonable gap equation, even if the diagrammatic content of the quark-gluon vertex is unknown. We locate a critical end point at (μ(E),T(E))∼(1.0,0.9)T(c), where T(c) is the critical temperature for chiral-symmetry restoration at μ=0, and find that a domain of phase coexistence opens at the critical end point whose area increases as a confinement length scale grows.
Heavy quark signals from radiative corrections to the Z{sup '} boson decay in 3-3-1 models
Martinez, R.; Ochoa, F.
2009-10-01
One-loop corrections to the Z{sup '} decay width are derived and analyzed in the framework of the general form of the 3-3-1 models. We identify two important sources of corrections: oblique corrections associated to the Z{sup '} propagator through vacuum polarizations induced by virtual particle-antiparticle pairs of new heavy quarks J, and vertex corrections to the Z{sup '}qq vertex through virtual exchange of new K{sup Q{sub 1,2}} gauge bosons. Fixing a specific renormalization scheme, we obtain dominant oblique corrections that exhibit a quadratic dependence on the J quark mass, which are absorbed into two oblique parameters: a global parameter {rho}{sub f}{sup '} which modify the Z{sup '} decay width, and a parameter {kappa}{sub f}{sup '} that define effective Z{sup '} couplings. Numerical results in an specific 3-3-1 model gives a strong contribution of the oblique corrections from about 1.3% in the d(s) quark channel to 10.5% in the neutrino channel, for m{sub J}=2 TeV. The vertex corrections contribute to the oblique corrections up to 1.4% for the same channel and m{sub J} value. For pp collisions at the CERN LHC collider, we find that the corrections significantly modify the shape of the cross section distributions for e{sup +}e{sup -} and tt final states, where the distributions including the radiative corrections increases up to 1.23 times the tree-level distribution for the dielectron events and to 1.07 for the top events when m{sub J}=3 TeV.
NASA Astrophysics Data System (ADS)
Tan, Meng-Chwan
2007-07-01
In this paper, we study the perturbative aspects of a ``B-twisted" two-dimensional (0,2) heterotic sigma model on a holomorphic gauge bundle Script E over a complex, hermitian manifold X. We show that the model can be naturally described in terms of the mathematical theory of ``Chiral Differential Operators". In particular, the physical anomalies of the sigma model can be reinterpreted as an obstruction to a global definition of the associated sheaf of vertex superalgebras derived from the free conformal field theory describing the model locally on X. In addition, one can also obtain a novel understanding of the sigma model one-loop beta function solely in terms of holomorphic data. At the (2,2) locus, one can describe the resulting half-twisted variant of the topological B-model in terms of a mirror ``Chiral de Rham complex" (or CDR) defined by Malikov et al. in [1]. Via mirror symmetry, one can also derive various conjectural expressions relating the sheaf cohomology of the mirror CDR to that of the original CDR on pairs of Calabi-Yau mirror manifolds. An analysis of the half-twisted model on a non-Kähler group manifold with torsion also allows one to draw conclusions about the corresponding sheaves of CDR (and its mirror) that are consistent with mathematically established results by Ben-Bassat in [2] on the mirror symmetry of generalised complex manifolds. These conclusions therefore suggest an interesting relevance of the sheaf of CDR in the recent study of generalised mirror symmetry.
Masina, Isabella; Notari, Alessio
2012-05-11
For a narrow band of values of the top quark and Higgs boson masses, the standard model Higgs potential develops a false minimum at energies of about 10(16) GeV, where primordial inflation could have started in a cold metastable state. A graceful exit to a radiation-dominated era is provided, e.g., by scalar-tensor gravity models. We pointed out that if inflation happened in this false minimum, the Higgs boson mass has to be in the range 126.0±3.5 GeV, where ATLAS and CMS subsequently reported excesses of events. Here we show that for these values of the Higgs boson mass, the inflationary gravitational wave background has be discovered with a tensor-to-scalar ratio at hand of future experiments. We suggest that combining cosmological observations with measurements of the top quark and Higgs boson masses represent a further test of the hypothesis that the standard model false minimum was the source of inflation in the universe.
Masina, Isabella; Notari, Alessio
2012-05-11
For a narrow band of values of the top quark and Higgs boson masses, the standard model Higgs potential develops a false minimum at energies of about 10(16) GeV, where primordial inflation could have started in a cold metastable state. A graceful exit to a radiation-dominated era is provided, e.g., by scalar-tensor gravity models. We pointed out that if inflation happened in this false minimum, the Higgs boson mass has to be in the range 126.0±3.5 GeV, where ATLAS and CMS subsequently reported excesses of events. Here we show that for these values of the Higgs boson mass, the inflationary gravitational wave background has be discovered with a tensor-to-scalar ratio at hand of future experiments. We suggest that combining cosmological observations with measurements of the top quark and Higgs boson masses represent a further test of the hypothesis that the standard model false minimum was the source of inflation in the universe. PMID:23003024
Pion and η -meson mass splitting at the two-flavor chiral crossover
NASA Astrophysics Data System (ADS)
Heller, Markus; Mitter, Mario
2016-10-01
We study the splitting in the screening mass of pions and the η -meson across the chiral crossover. This splitting is determined by the 't Hooft determinant. We use results for the renormalization group scale dependence of the 't Hooft determinant obtained within the functional renormalization group in quenched QCD with two flavors. The scale dependence of the 't Hooft determinant is mapped to its temperature dependence with the help of a Polyakov-quark-meson model. As a result we obtain the temperature dependence of the splitting in the screening mass of pions and the η -meson.
Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya
2015-10-15
The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.
Applications of partially quenched chiral perturbation theory
Golterman, M.F.; Leung, K.C.
1998-05-01
Partially quenched theories are theories in which the valence- and sea-quark masses are different. In this paper we calculate the nonanalytic one-loop corrections of some physical quantities: the chiral condensate, weak decay constants, Goldstone boson masses, B{sub K}, and the K{sup +}{r_arrow}{pi}{sup +}{pi}{sup 0} decay amplitude, using partially quenched chiral perturbation theory. Our results for weak decay constants and masses agree with, and generalize, results of previous work by Sharpe. We compare B{sub K} and the K{sup +} decay amplitude with their real-world values in some examples. For the latter quantity, two other systematic effects that plague lattice computations, namely, finite-volume effects and unphysical values of the quark masses and pion external momenta, are also considered. We find that typical one-loop corrections can be substantial. {copyright} {ital 1998} {ital The American Physical Society}
Jiang, Kun; Zhang, Yi; Zhou, Sen; Wang, Ziqiang
2015-05-29
We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping t_{1} and second nearest-neighbor hopping t_{2}, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction U induces antiferromagnetic (AF) chiral spin density wave (χSDW) order in a wide range of κ=t_{2}/t_{1} where both the two-sublattice AF order at small κ and the decoupled three-sublattice 120° order at large κ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a χSDW semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a χSDW insulator with a zero total Chern number but an anomalous ac Hall effect. The χSDW is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons. PMID:26066448
Jiang, Kun; Zhang, Yi; Zhou, Sen; Wang, Ziqiang
2015-05-29
We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping t_{1} and second nearest-neighbor hopping t_{2}, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction U induces antiferromagnetic (AF) chiral spin density wave (χSDW) order in a wide range of κ=t_{2}/t_{1} where both the two-sublattice AF order at small κ and the decoupled three-sublattice 120° order at large κ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a χSDW semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a χSDW insulator with a zero total Chern number but an anomalous ac Hall effect. The χSDW is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
Nuclear chiral dynamics and thermodynamics
NASA Astrophysics Data System (ADS)
Holt, Jeremy W.; Kaiser, Norbert; Weise, Wolfram
2013-11-01
This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit Δ(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependences of the chiral (quark) condensate are investigated.
Asaturyan, R.; Ent, R.; Mkrtchyan, H.; Navasardyan, T.; Tadevosyan, V.; Adams, G. S.; Ahmidouch, A.; Angelescu, T.; Arrington, J.; Asaturyan, A.; et al
2012-01-01
A large set of cross sections for semi-inclusive electroproduction of charged pions (π±) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared W2 > 4 GeV2 and range in four-momentum transfer squared 2 < Q2 < 4 (GeV/c)2, and cover a range in the Bjorken scaling variable 0.2 < x < 0.6. The fractional energy of the pions spans a range 0.3 < z < 1, with small transverse momenta with respect to the virtual-photon direction, Pt2 < 0.2 (GeV/c)2. The invariant mass that goes undetected, Mx or W',more » is in the nucleon resonance region, W' < 2 GeV. The new data conclusively show the onset of quark-hadron duality in this process, and the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark → pion production mechanisms. The x, z and Pt2 dependences of several ratios (the ratios of favored-unfavored fragmentation functions, charged pion ratios, deuteron-hydrogen and aluminum-deuteron ratios for π+ and π-) have been studied. The ratios are found to be in good agreement with expectations based upon a high-energy quark-parton model description. We find the azimuthal dependences to be small, as compared to exclusive pion electroproduction, and consistent with theoretical expectations based on tree-level factorization in terms of transverse-momentum-dependent parton distribution and fragmentation functions. In the context of a simple model, the initial transverse momenta of d quarks are found to be slightly smaller than for u quarks, while the transverse momentum width of the favored fragmentation function is about the same as for the unfavored one, and both fragmentation widths are larger than the quark widths.« less
A simple reason based on supersymmetry for replication of chiral families
NASA Astrophysics Data System (ADS)
Babu, K. S.; Pati, Jogesh C.; Stremnitzer, Hanns
1991-03-01
In the context of the minimal flavon-chromon preon model, we show that supersymmetry, because of fermion-boson pairing in its field content, provides a rather simple reason for replication of composite quark-lepton families. At the level of minimum number of core constituents, which turns out to be three, it also provides a good reason why one may expect to have just three light chiral families. One crucial prediction is that there must exist complete vector-like families with mass of order 1 TeV for quark-like and few hundred GeV for lepton-like members. This can be tested at SSC, LHC and future high energy e-e+ machines.
Wicke, Daniel; /Wuppertal U., Dept. Math.
2009-08-01
The aim of particle physics is the understanding of elementary particles and their interactions. The current theory of elementary particle physics, the Standard Model, contains twelve different types of fermions which (neglecting gravity) interact through the gauge bosons of three forces. In addition a scalar particle, the Higgs boson, is needed for theoretical consistency. These few building blocks explain all experimental results found in the context of particle physics, so far. Nevertheless, it is believed that the Standard Model is only an approximation to a more complete theory. First of all the fourth known force, gravity, has withstood all attempts to be included until now. Furthermore, the Standard Model describes several features of the elementary particles like the existence of three families of fermions or the quantisation of charges, but does not explain these properties from underlying principles. Finally, the lightness of the Higgs boson needed to explain the symmetry breaking is difficult to maintain in the presence of expected corrections from gravity at high scales. This is the so called hierarchy problem. In addition astrophysical results indicate that the universe consists only to a very small fraction of matter described by the Standard Model. Large fractions of dark energy and dark matter are needed to describe the observations. Both do not have any correspondence in the Standard Model. Also the very small asymmetry between matter and anti-matter that results in the observed universe built of matter (and not of anti-matter) cannot be explained until now. It is thus an important task of experimental particle physics to test the predictions of the Standard Model to the best possible accuracy and to search for deviations pointing to necessary extensions or modifications of our current theoretical understanding. The top quark was predicted to exist by the Standard Model as the partner of the bottom quark. It was first observed in 1995 by the
No-Drag Frame for Anomalous Chiral Fluid.
Stephanov, Mikhail A; Yee, Ho-Ung
2016-03-25
We show that for an anomalous fluid carrying dissipationless chiral magnetic and/or vortical currents there is a frame in which a stationary obstacle experiences no drag, but energy and charge currents do not vanish, resembling superfluidity. However, unlike ordinary superfluid flow, the anomalous chiral currents can transport entropy in this frame. We show that the second law of thermodynamics completely determines the amounts of these anomalous nondissipative currents in the "no-drag frame" as polynomials in temperature and chemical potential with known anomaly coefficients. These general results are illustrated and confirmed by a calculation in the chiral kinetic theory and in the quark-gluon plasma at high temperature.
Transverse Quark Spin Effects and the Flavor Dependence of the Boer-Mulders Function
Leonard P. Gamberg; Gary R. Goldstein; Marc Schlegel
2007-07-30
The naive time reversal odd (T-odd) parton distribution $h_{1}^{\\perp}$, the so-called Boer-Mulders function, for both $u$- and $d$-quarks is considered in the diquark spectator model. While other approaches give evidence that the signs of the Boer-Mulders function for both flavors $u$ and $d$ are the same and negative, previous caculations in the diquark-spectator model found $h_{1}^{\\perp(u)}$ and $h_{1}^{\\perp(d)}$ have differnet signs. The flavor dependence is of significance for the analysis of the azimuthal $\\cos(2\\phi)$ asymmetries in unpolarized SIDIS and DY-processes, as well as for the overall physical understanding of the distribution of transversely polarized quarks in unpolarized nucleons. We find substantial differences with previous work. In particular we obtain estimates of the zeroth, half and first moments of Boer-Mulders functions that are negative over the full range in Bjorken $x$ for both the up and down quarks. In conjunction with the Collins function we then predict the $\\cos(2\\phi)$ azimuthal asymmetry for $\\pi^{+}$ and $\\pi^{-}$ in this framework. We also find that the Sivers up and down quark are negative and postive respectively. As a by-product of the formalism, we calculate the chiral-odd but T-even function $h_{1L}^{\\perp}$ in the spectator framework, which allows us to present a prediction for the single spin asymmetry $A_{UL}^{\\sin(2\\phi)}$ for a longitudinally polarized target in SIDIS.
Aaltonen, T; Álvarez González, B; Amerio, S; Amidei, D; Anastassov, A; Annovi, A; Antos, J; Apollinari, G; Appel, J A; Arisawa, T; Artikov, A; Asaadi, J; Ashmanskas, W; Auerbach, B; Aurisano, A; Azfar, F; Badgett, W; Bae, T; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Barria, P; Bartos, P; Bauce, M; Bedeschi, F; Behari, S; Bellettini, G; Bellinger, J; Benjamin, D; Beretvas, A; Bhatti, A; Bisello, D; Bizjak, I; Bland, K R; Blumenfeld, B; Bocci, A; Bodek, A; Bortoletto, D; Boudreau, J; Boveia, A; Brigliadori, L; Bromberg, C; Brucken, E; Budagov, J; Budd, H S; Burkett, K; Busetto, G; Bussey, P; Buzatu, A; Calamba, A; Calancha, C; Camarda, S; Campanelli, M; Campbell, M; Canelli, F; Carls, B; Carlsmith, D; Carosi, R; Carrillo, S; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavaliere, V; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, K; Chokheli, D; Chung, W H; Chung, Y S; Ciocci, M A; Clark, A; Clarke, C; Compostella, G; Connors, J; Convery, M E; Conway, J; Corbo, M; Cordelli, M; Cox, C A; Cox, D J; Crescioli, F; Cuevas, J; Culbertson, R; Dagenhart, D; d'Ascenzo, N; Datta, M; de Barbaro, P; Dell'Orso, M; Demortier, L; Deninno, M; Devoto, F; d'Errico, M; Di Canto, A; Di Ruzza, B; Dittmann, J R; D'Onofrio, M; Donati, S; Dong, P; Dorigo, M; Dorigo, T; Ebina, K; Elagin, A; Eppig, A; Erbacher, R; Errede, S; Ershaidat, N; Eusebi, R; Farrington, S; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Forrest, R; Frank, M J; Franklin, M; Freeman, J C; Funakoshi, Y; Furic, I; Gallinaro, M; Garcia, J E; Garfinkel, A F; Garosi, P; Gerberich, H; Gerchtein, E; Giagu, S; Giakoumopoulou, V; Giannetti, P; Gibson, K; Ginsburg, C M; Giokaris, N; Giromini, P; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldin, D; Goldschmidt, N; Golossanov, A; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Goulianos, K; Grinstein, S; Grosso-Pilcher, C; Group, R C; Guimaraes da Costa, J; Hahn, S R; Halkiadakis, E; Hamaguchi, A; Han, J Y; Happacher, F; Hara, K; Hare, D; Hare, M; Harr, R F; Hatakeyama, K; Hays, C; Heck, M; Heinrich, J; Herndon, M; Hewamanage, S; Hocker, A; Hopkins, W; Horn, D; Hou, S; Hughes, R E; Hurwitz, M; Husemann, U; Hussain, N; Hussein, M; Huston, J; Introzzi, G; Iori, M; Ivanov, A; James, E; Jang, D; Jayatilaka, B; Jeon, E J; Jindariani, S; Jones, M; Joo, K K; Jun, S Y; Junk, T R; Kamon, T; Karchin, P E; Kasmi, A; Kato, Y; Ketchum, W; Keung, J; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kim, Y J; Kimura, N; Kirby, M; Klimenko, S; Knoepfel, K; Kondo, K; Kong, D J; Konigsberg, J; Kotwal, A V; Kreps, M; Kroll, J; Krop, D; Kruse, M; Krutelyov, V; Kuhr, T; Kurata, M; Kwang, S; Laasanen, A T; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lecompte, T; Lee, E; Lee, H S; Lee, J S; Lee, S W; Leo, S; Leone, S; Lewis, J D; Limosani, A; Lin, C-J; Lindgren, M; Lipeles, E; Lister, A; Litvintsev, D O; Liu, C; Liu, H; Liu, Q; Liu, T; Lockwitz, S; Loginov, A; Lucchesi, D; Lueck, J; Lujan, P; Lukens, P; Lungu, G; Lys, J; Lysak, R; Madrak, R; Maeshima, K; Maestro, P; Malik, S; Manca, G; Manousakis-Katsikakis, A; Margaroli, F; Marino, C; Martínez, M; Mastrandrea, P; Matera, K; Mattson, M E; Mazzacane, A; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Mehtala, P; Mesropian, C; Miao, T; Mietlicki, D; Mitra, A; Miyake, H; Moed, S; Moggi, N; Mondragon, M N; Moon, C S; Moore, R; Morello, M J; Morlock, J; Movilla Fernandez, P; Mukherjee, A; Muller, Th; Murat, P; Mussini, M; Nachtman, J; Nagai, Y; Naganoma, J; Nakano, I; Napier, A; Nett, J; Neu, C; Neubauer, M S; Nielsen, J; Nodulman, L; Noh, S Y; Norniella, O; Oakes, L; Oh, S H; Oh, Y D; Oksuzian, I; Okusawa, T; Orava, R; Ortolan, L; Pagan Griso, S; Pagliarone, C; Palencia, E; Papadimitriou, V; Paramonov, A A; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Pianori, E; Pilot, J; Pitts, K; Plager, C; Pondrom, L; Poprocki, S; Potamianos, K; Prokoshin, F; Pranko, A; Ptohos, F; Punzi, G; Rahaman, A; Ramakrishnan, V; Ranjan, N; Redondo, I; Renton, P; Rescigno, M; Riddick, T; Rimondi, F; Ristori, L; Robson, A; Rodrigo, T; Rodriguez, T; Rogers, E; Rolli, S; Roser, R; Ruffini, F; Ruiz, A; Russ, J; Rusu, V; Safonov, A; Sakumoto, W K; Sakurai, Y; Santi, L; Sato, K; Saveliev, V; Savoy-Navarro, A; Schlabach, P; Schmidt, A; Schmidt, E E; Schwarz, T; Scodellaro, L; Scribano, A; Scuri, F; Seidel, S; Seiya, Y; Semenov, A; Sforza, F; Shalhout, S Z; Shears, T; Shepard, P F; Shimojima, M; Shochet, M; Shreyber-Tecker, I; Simonenko, A; Sinervo, P; Sliwa, K; Smith, J R; Snider, F D; Soha, A; Sorin, V; Song, H; Squillacioti, P; Stancari, M; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Strycker, G L; Sudo, Y; Sukhanov, A; Suslov, I; Takemasa, K; Takeuchi, Y; Tang, J; Tecchio, M; Teng, P K; Thom, J; Thome, J; Thompson, G A; Thomson, E; Toback, D; Tokar, S; Tollefson, K; Tomura, T; Tonelli, D; Torre, S; Torretta, D; Totaro, P; Trovato, M; Ukegawa, F; Uozumi, S; Varganov, A; Vázquez, F; Velev, G; Vellidis, C; Vidal, M; Vila, I; Vilar, R; Vizán, J; Vogel, M; Volpi, G; Wagner, P; Wagner, R L; Wakisaka, T; Wallny, R; Wang, S M; Warburton, A; Waters, D; Wester, W C; Whiteson, D; Wicklund, A B; Wicklund, E; Wilbur, S; Wick, F; Williams, H H; Wilson, J S; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, H; Wright, T; Wu, X; Wu, Z; Yamamoto, K; Yamato, D; Yang, T; Yang, U K; Yang, Y C; Yao, W-M; Yeh, G P; Yi, K; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanetti, A; Zeng, Y; Zhou, C; Zucchelli, S
2012-11-01
A search is presented for the standard model Higgs boson produced in association with top quarks using the full Run II proton-antiproton collision data set, corresponding to 9.45 fb(-1), collected by the Collider Detector at Fermilab. No significant excess over the expected background is observed, and 95% credibility-level upper bounds are placed on the cross section σ(ttH → lepton + missing transverse energy+jets). For a Higgs boson mass of 125 GeV/c(2), we expect to set a limit of 12.6 and observe a limit of 20.5 times the standard model rate. This represents the most sensitive search for a standard model Higgs boson in this channel to date.
Quark Physics without Quarks: A Review of Recent Developments in S-Matrix Theory.
ERIC Educational Resources Information Center
Capra, Fritjof
1979-01-01
Reviews the developments in S-matrix theory over the past five years which have made it possible to derive results characteristic of quark models without any need to postulate the existence of physical quarks. In the new approach, the quark patterns emerge as a consequence of combining the general S-matrix principles with the concept of order.…
NASA Astrophysics Data System (ADS)
Singha, Subhash; Nasim, Md.
2016-03-01
We studied the number of constituent quark scaling (NCQ) behavior of elliptic flow (v2) under the framework of a multiphase transport model (AMPT) at both top-RHIC and LHC energies. The NCQ-scaling in v2 holds at top RHIC energy with AMPT string melting version, while it breaks in Pb+Pb collisions at LHC energy using the same framework. The breaking of NCQ scaling at LHC energy has been studied by varying the magnitude of parton-parton scattering cross sections and lifetime of hadronic cascade as implemented in AMPT. We find that the breaking of NCQ scaling in Pb+Pb collisions at √{sNN}=2.76 TeV is independent of the magnitude of parton-parton cross sections and the later stage hadronic interactions. Further we observed that scaling holds in a small collision system like Si+Si at √{sNN}=2.76 TeV. We discussed that the breaking of NCQ scaling is possibly due to high phase-space density of constituents quarks in Pb+Pb collisions at √{sNN}=2.76 TeV.
REVIEW ARTICLE: Chiral metamaterials: simulations and experiments
NASA Astrophysics Data System (ADS)
Wang, Bingnan; Zhou, Jiangfeng; Koschny, Thomas; Kafesaki, Maria; Soukoulis, Costas M.
2009-11-01
Electromagnetic metamaterials are composed of periodically arranged artificial structures. They show peculiar properties, such as negative refraction and super-lensing, which are not seen in natural materials. The conventional metamaterials require both negative epsilon and negative μ to achieve negative refraction. Chiral metamaterial is a new class of metamaterials offering a simpler route to negative refraction. In this paper, we briefly review the history of metamaterials and the developments on chiral metamaterials. We study the wave propagation properties in chiral metamaterials and show that negative refraction can be realized in chiral metamaterials with a strong chirality, with neither epsilon nor μ negative required. We have developed a retrieval procedure, adopting a uniaxial bi-isotropic model to calculate the effective parameters such as n ± , κ, epsilon and μ of the chiral metamaterials. Our work on the design, numerical calculations and experimental measurements of chiral metamaterials is introduced. Strong chiral behaviors such as optical activity and circular dichroism are observed and negative refraction is obtained for circularly polarized waves in these chiral metamaterials. We show that 3D isotropic chiral metamaterials can eventually be realized.
Chiral anomaly, bosonization, and fractional charge
Mignaco, J.A.; Monteiro, M.A.R.
1985-06-15
We present a method to evaluate the Jacobian of chiral rotations, regulating determinants through the proper-time method and using Seeley's asymptotic expansion. With this method we compute easily the chiral anomaly for ..nu.. = 4,6 dimensions, discuss bosonization of some massless two-dimensional models, and handle the problem of charge fractionization. In addition, we comment on the general validity of Fujikawa's approach to regulate the Jacobian of chiral rotations with non-Hermitian operators.
Light Four-Quark States and New Observations by BES
NASA Astrophysics Data System (ADS)
Zhang, A.; Huang, T.; Steele, T.
Four-quark states are discussed within the constituent quark model.Incompleteness of existed studies of four-quark state with QCD sum rule is analyzed. The masses of diquark cluster were determined by QCD sum rules, and light four-quark states masses were obtained in terms of the diquark. The four-quark state possibility of the newly observed near-threshold pbar p enhancement, X(1835), X(1812) and X(1576) by BES is discussed.
Quark number fluctuations at high temperatures
Petreczky, P.; Hegde, P.; Velytsky, A.
2009-11-01
We calculate the second, fourth and sixth order quark number fluctuations in the deconfined phase of 2+1 flavor QCD using lattices with temporal extent N{sub t} = 4,6,8 and 12. We consider light, strange and charm quarks. We use p4 action for valence quarks and gauge configurations generated with p4 action with physical value of the strange quark mass and light quark mass m{sub q} = 0.1 m{sub s} generated by the RBC-Bielefeld collaboration. We observe that for all quark masses the quark number fluctuations rapidly get close to the corresponding ideal gas limits. We compare our results to predictions of a quasi-particle model and resummed high temperature perturbative calculations. We also investigate correlations among different flavor channels.
Rosen, Brad M; Roche, Cécile; Percec, Virgil
2013-01-01
Biological macromolecules are homochiral, composed of sequences of stereocenters possessing the same repeated absolute configuration. This chapter addresses the mechanism of homochiral selection in polypeptides. In particular, the relationship between the stereochemistry (L or D) of structurally distinct α-amino acids is explored. Through functionalization of Tyr-Xaa dipeptides with self-assembling dendrons, the effect of stereochemical sequence of the dipeptide on the thermodynamics of self-assembly and the resulting structural features can be quantified. The dendritic dipeptide approach effectively isolates the stereochemical information of the shortest sequence of stereochemical information possible in polypeptide, while simultaneously allowing for dendron driven tertiary and quaternary structure formation and subsequent transfer of chiral information from the dipeptide to the dendritic sheath. This approach elucidates a mechanism of selecting a homochiral relationship between dissimilar but neighboring α-amino acids through thermodynamic preference for homochirality in solution-phase and bulk supramolecular helical polymerization. PMID:23306867
Lattice QCD Calculation of the Kaon B Parameter with the Wilson Quark Action
NASA Astrophysics Data System (ADS)
Aoki, S.; Fukugita, M.; Hashimoto, S.; Ishizuka, N.; Iwasaki, Y.; Kanaya, K.; Kuramashi, Y.; Okawa, M.; Ukawa, A.; Yoshie, T.; Jlqcd Collaboration
1998-08-01
The kaon B parameter is calculated in quenched lattice QCD with the Wilson quark action. The mixing problem of the Δs = 2 four-quark operators is solved nonperturbatively with full use of chiral Ward identities, and this method enables us to construct the weak four-quark operators exhibiting good chiral behavior. We find BK\\(NDR,2 GeV\\) = 0.69\\(7\\) (where NDR denotes naive dimensional regularization) at the lattice cutoff scale of a-1 = 2.7-4.3 GeV.
Generalized parton distributions from domain wall valence quarks and staggered sea quarks
Renner, Dru; Bratt, Jonathan; Edwards, Robert; Engelhardt, Michael; Fleming, George; Haegler, Philipp; Musch, Bernhard; Negele, John; Orginos, Konstantinos; Pochinsky, Andrew; Richards, David; Schroers, Wolfram
2007-11-01
Moments of the generalized parton distributions of the nucleon, calculated with a mixed action of domain wall valence quarks and asqtad staggered sea quarks, are presented for pion masses extending down to 359 MeV. Results for the moments of the unpolarized, helicity, and transversity distributions are given and compared to the available experimental measurements. Additionally, a selection of the generalized form factors are shown and the implications for the spin decomposition and transverse structure of the nucleon are discussed. Particular emphasis is placed on understanding systematic errors in the lattice calculation and exploring a variety of chiral extrapolations.
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
Matevosyan, Hrayr H.; Thomas, Anthony W.; Tandy, Peter C.
2007-04-15
We include a generalized infinite class of quark-gluon vertex dressing diagrams in a study of how dynamics beyond the ladder-rainbow truncation influences the Bethe-Salpeter description of light-quark pseudoscalar and vector mesons. The diagrammatic specification of the vertex is mapped into a corresponding specification of the Bethe-Salpeter kernel, which preserves chiral symmetry. This study adopts the algebraic format afforded by the simple interaction kernel used in previous work on this topic. The new feature of the present work is that in every diagram summed for the vertex and the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be the self-consistent vertex solution. We also adopt from previous work the effective accounting for the role of the explicitly non-Abelian three-gluon coupling in a global manner through one parameter determined from recent lattice-QCD data for the vertex. Within the current model, the more consistent dressed vertex limits the ladder-rainbow truncation error for vector mesons to be never more than 10% as the current quark mass is varied from the u/d region to the b region.
Higher twists in polarized DIS and the size of the constituent quark
Alexander Sidorov; Christian Weiss
2006-02-15
The spontaneous breaking of chiral symmetry implies the presence of a short-distance scale in the QCD vacuum, which phenomenologically may be associated with the ''size'' of the constituent quark, rho {approx} 0.3 fm. We discuss the role of this scale in the matrix elements of the twist-4 and 3 quark-gluon operators determining the leading power (1/Q{sup 2}-) corrections to the moments of the nucleon spin structure functions. We argue that the flavor-nonsinglet twist-4 matrix element, f{sub 2}{sup u-d}, has a sizable negative value of the order rho{sup -2}, due to the presence of sea quarks with virtualities {approx} rho{sup -2} in the proton wave function. The twist-3 matrix element, d{sub 2}, is not related to the scale rho{sup -2}. Our arguments support the results of previous calculations of the matrix elements in the instanton vacuum model. We show that this qualitative picture is in agreement with the phenomenological higher-twist correction extracted from an NLO QCD fit to the world data on g{sub 1}{sup p} and g{sub 1}{sup n}, which include recent data from the Jefferson Lab Hall A and COMPASS experiments. We comment on the implications of the short-distance scale rho for quark-hadron duality and the x-dependence of higher-twist contributions.
Stable Pentaquarks from Strange Chiral Multiplets
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. 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.
Asymmetric synthesis using chiral-encoded metal.
Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander
2016-08-26
The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.
Asymmetric synthesis using chiral-encoded metal.
Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander
2016-01-01
The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity. PMID:27562028
Asymmetric synthesis using chiral-encoded metal
Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander
2016-01-01
The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity. PMID:27562028