Eric S. Swanson; Adam P. Szczepaniak
2002-06-07
The relationship of the quark model to the known chiral properties of QCD is a long-standing problem in the interpretation of low energy QCD. In particular, how can the pion be viewed as both a collective Goldstone boson quasiparticle and as a valence quark antiquark bound state? A comparison of the many-body solution of a simplified model of QCD to the constituent quark model demonstrates that the quark model is sufficiently flexible to describe meson hyperfine splitting provided proper renormalization conditions and correct degrees of freedom are employed consistently.
Meson phenomenology and phase transitions in nonlocal chiral quark models
NASA Astrophysics Data System (ADS)
Carlomagno, J. P.; Gomez Dumm, D.; Pagura, V.; Scoccola, N. N.
2015-07-01
We study the features of nonlocal chiral quark models that include wave function renormalization. Model parameters are determined from meson phenomenology, considering different nonlocal form factor shapes. In this context we analyze the characteristics of the deconfinement and chiral restoration transitions at finite temperature and chemical potential, introducing the couplings of fermions to the Polyakov loop for different Polyakov potentials. The results for various thermodynamical quantities are compared with data obtained from lattice QCD calculations.
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.
Quark matter under strong magnetic fields in chiral models
Rabhi, Aziz; Providencia, Constanca
2011-05-15
The chiral model is used to describe quark matter under strong magnetic fields and is compared to other models, the MIT bag model and the two-flavor Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic-field vacuum corrections are not taken into account explicitly, the parameters of the models should be fitted to low-density meson properties in the presence of the magnetic field.
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}.
Axially symmetric multi-baryon solutions and their quantization in the chiral quark soliton model
NASA Astrophysics Data System (ADS)
Komori, S.; Sawado, N.; Shiiki, N.
2004-05-01
We study axially symmetric solutions with B=2-5 in the chiral quark soliton model. In the background of axially symmetric chiral fields, the quark eigenstates and profile functions of the chiral fields are computed self-consistently. The resultant quark bound spectrum are doubly degenerate due to the symmetry of the chiral field. Upon quantization, various observable spectra of the chiral solitons are obtained. Taking account of the Finkelstein-Rubinstein constraints, we show that the quantum numbers of our solitons coincide with the physical observations for B=2 and 4 while B=3 and 5 do not.
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.
Understanding the structure of d*(2380) in chiral quark model
NASA Astrophysics Data System (ADS)
Huang, Fei; Shen, PengNian; Dong, YuBing; Zhang, ZongYe
2016-02-01
The structure and decay properties of d* have been detailedly investigated in both the chiral SU(3) quark model and the extended chiral SU(3) quark model that describe the energies of baryon ground states and the nucleon-nucleon (NN) scattering data satisfactorily. By performing a dynamical coupled-channels study of the system of ΔΔ and hidden-color channel (CC) with quantum numbers I( J P ) = 0(3+) in the framework of the resonating group method (RGM), we find that the d* has a mass of about 2.38-2.42 GeV and a root-mean-square radius (RMS) of about 0.76-0.88 fm. The channel wave function is extracted by a projection of the RGM wave function onto the physical basis, and the fraction of CC component in the d* is found to be about 66%-68%, which indicates that the d* is a hexaquark-dominated exotic state. Based on this scenario the partial decay widths of d* → d π 0 π 0 and d∗ → d π + π - are further explicitly evaluated and the total width is then obtained by use of the branching ratios extracted from the measured cross sections of other possible decay channels. Both the mass and the decay width of d* calculated in this work are compatible with the data ( M ≈ 2380 MeV, Γ ≈ 70 MeV) reported by WASA-at-COSY Collaboration.
Phase diagram of neutral quark matter in nonlocal chiral quark models
NASA Astrophysics Data System (ADS)
Gómez Dumm, D.; Blaschke, D. B.; Grunfeld, A. G.; Scoccola, N. N.
2006-06-01
We consider the phase diagram of two-flavor quark matter under neutron star constraints for two nonlocal, covariant quark models within the mean-field approximation. In the first case (Model I) the nonlocality arises from the regularization procedure, motivated by the instanton liquid model, whereas in the second one (Model II) a separable approximation of the one-gluon exchange interaction is applied. We find that Model II predicts a larger quark mass gap and a chiral symmetry breaking (CSB) phase transition line which extends 15 20% further into the phase diagram spanned by temperature (T) and chemical potential (μ). The corresponding critical temperature at μ=0, Tc(0)≃140MeV, is in better accordance to recent lattice QCD results than the prediction of the standard local NJL model, which exceeds 200 MeV. For both Model I and Model II we have considered various coupling strengths in the scalar diquark channel, showing that different low-temperature quark matter phases can occur at intermediate densities: a normal quark matter (NQM) phase, a two-flavor superconducting (2SC) quark matter phase and a mixed 2SC-NQM phase. Although in most cases there is also a gapless 2SC phase, this occurs in general in a small region at nonzero temperatures, thus its effect should be negligible for compact star applications.
Charmed baryon strong decays in a chiral quark model
Zhong Xianhui; Zhao Qiang
2008-04-01
Charmed baryon strong decays are studied in a chiral quark model. The data for the decays of {lambda}{sub c}{sup +}(2593), {lambda}{sub c}{sup +}(2625), {sigma}{sub c}{sup ++,+,0}, and {sigma}{sub c}{sup +,0}(2520) are accounted for successfully, which allows one to fix the pseudoscalar-meson-quark couplings in an effective chiral Lagrangian. Extending this framework to analyze the strong decays of the newly observed charmed baryons, we classify that {lambda}{sub c}(2880) and {lambda}{sub c}(2940) as D-wave states in the N=2 shell; {lambda}{sub c}(2880) could be |{lambda}{sub c}{sup 2}D{sub {lambda}}{sub {lambda}}(3/2){sup +}> and {lambda}{sub c}(2940) could be |{lambda}{sub c}{sup 2}D{sub {lambda}}{sub {lambda}}(5/2){sup +}>. Our calculation also suggests that {lambda}{sub c}(2765) is very likely a {rho}-mode P-wave excited state in the N=1 shell, and favors a |{lambda}{sub c}{sup 4}P{sub {rho}}(1/2){sup -}> configuration. The {sigma}{sub c}(2800) favors being a |{sigma}{sub c}{sup 2}P{sub {lambda}}(1/2){sup -}> state. But its being |{sigma}{sub c}{sup ++4}P{sub {lambda}}(5/2){sup -}> cannot be ruled out.
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.
Quark Number Fluctuations in a Chiral Model with a Magnetic Field
NASA Astrophysics Data System (ADS)
Cheng, Lidens; Incera, Vivian
2013-04-01
An important consequence of quantum chromodynamics (QCD) is the existence of a phase transition between the hadronic and quark-gluon phases. The hadronic phase exhibits confinement and broken chiral symmetry. The quark-gluon phase exhibits deconfinement and chiral symmetry. The phase boundary can be seen in the temperature-quark chemical potential plane. For large chemical potential, there is a first order chiral transition. For small chemical potential and 2 massless quarks flavors, there is a second order chiral transition. Thus, a critical end point (CEP) is expected where the first order phase transitions end. In the chiral limit or for finite quark masses, the net quark number susceptibility diverges at the CEP. However, when clear from the CEP, it is finite. Hence, the net quark number susceptibility is non-monotonic along the phase boundary if there is a CEP. In this case, the Nambu--Jona-Lasinio model is composed at finite temperature and quark and isospin chemical potentials. The addition of a strong magnetic field in the model is significant because strong magnetic fields are produced in off-central heavy-ion collisions and are present at the core of neutron stars.
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.
Octet baryon magnetic moments in the chiral quark model with configuration mixing
Linde, J.; Ohlsson, T.; Snellman, H.
1998-01-01
The Coleman{endash}Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman{endash}Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two models of wave functions with configuration mixing are studied. One of these models violates the Coleman{endash}Glashow sum-rule to the right degree and also reproduces the octet baryon magnetic moments rather accurately. {copyright} {ital 1997} {ital The American Physical Society}
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.
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
NASA Astrophysics Data System (ADS)
Biernat, Elmar P.; Peña, M. T.; Ribeiro, J. E.; Stadler, A.; Gross, F.
2016-03-01
We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for π-π-scattering imposed by chiral symmetry.
Hadronic contributions to the muon anomaly in the Constituent Chiral Quark Model
NASA Astrophysics Data System (ADS)
Greynat, David
2016-04-01
The hadronic contributions to the anomalous magnetic moment of the muon which are relevant for the confrontation between theory and experiment at the present level of accuracy, are evaluated within the same framework: the constituent chiral quark model. This includes the contributions from the dominant hadronic vacuum polarization as well as from the next-to-leading order hadronic vacuum polarization, the contributions from the hadronic light-by-light scattering, and the contributions from the electroweak hadronic Zγγ vertex. They are all evaluated as a function of only one free parameter: the constituent quark mass. We also comment on the comparison between our results and other phenomenological evaluations.
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.
Influence of the Polyakov loop on the chiral phase transition in the two flavor chiral quark model
NASA Astrophysics Data System (ADS)
Markó, G.; Szép, Zs.
2010-09-01
The SU(2)L×SU(2)R chiral quark model consisting of the (σ,π→) meson multiplet and the constituent quarks propagating on the homogeneous background of a temporal gauge field is solved at finite temperature and quark baryon chemical potential μq using an expansion in the number of flavors Nf, both in the chiral limit and for the physical value of the pion mass. Keeping the fermion propagator at its tree level, several approximations to the pion propagator are investigated. These approximations correspond to different partial resummations of the perturbative series. Comparing their solution with a diagrammatically formulated resummation relying on a strict large-Nf expansion of the perturbative series, one concludes that only when the local part of the approximated pion propagator resums infinitely many orders in 1/Nf of fermionic contributions a sufficiently rapid crossover transition at μq=0 is achieved allowing for the existence of a tricritical point or a critical end point in the μq-T phase diagram. The renormalization and the possibility of determining the counterterms in the resummation provided by a strict large-Nf expansion are investigated.
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.
Light pseudoscalar mesons in a nonlocal three flavor chiral quark model
Gomez Dumm, D.; Scarpettini, A.; Scoccola, N.N.
2004-12-02
We study the properties of light pseudoscalar mesons in a three flavor chiral quark model with nonlocal separable interactions. We consider the case of a Gaussian regulator, evaluating meson masses and decay constants. Our results are found to be in good agreement with empirical values, in particular, in the case of the ratio f{kappa}/f{pi} and the decay {pi}0 {yields} {gamma}{gamma}. The model leads also to a reasonable description of the observed phenomenology in the {eta} - {eta}' sector, where two significantly different mixing angles are required. Detailed description of the work sketched here can be found elsewhere.
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.
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.
Semileptonic decay constants of octet baryons in the chiral quark-soliton model
Kim, H.; Polyakov, M.V.; Praszalowicz, M.; Goeke, K.
1998-01-01
Based on the recent study of the magnetic moments and axial-vector constants within the framework of the chiral quark-soliton model, we investigate the baryon semileptonic decay constants (f{sub 1},f{sub 2}) and (g{sub 1},g{sub 2}). Employing the relations between the diagonal transition matrix elements and off-diagonal ones in the vector and axial-vector channels, we obtain the ratios of baryon semileptonic decay constants f{sub 2}/f{sub 1} and g{sub 1}/f{sub 1}. The F/D ratio is also discussed and found that the value predicted by the present model naturally lies between that of the Skyrme model and that of the nonrelativistic quark model. The singlet axial-vector constant g{sub A}{sup (0)} can be expressed in terms of the F/D ratio and g{sub A}{sup (3)} in the present model and turns out to be small. The results are compared with available experimental data and found to be in good agreement with them. In addition, the induced pseudotensor coupling constants g{sub 2}/f{sub 1} are calculated, the SU(3) symmetry breaking being considered. The results indicate that the effect of SU(3) symmetry breaking might play an important role for some decay modes in hyperon semileptonic decay. {copyright} {ital 1997} {ital The American Physical Society}
The nonlocal chiral quark model and the muon g - 2 problem
NASA Astrophysics Data System (ADS)
Dorokhov, A. E.; Radzhabov, A. E.; Shamakhov, F. A.; Zhevlakov, A. S.
2016-05-01
In the first part of the review we discuss the effective nonlocal approach in the quantum field theory. It concerns primary the historical retrospective of this approach, and than we concentrate on the interaction of matter particles (fermions and bosons) with the (abelian and nonabelian) gauge fields. In the second part of the review we consider the hadronic corrections (vacuum polarization) to the anomalous magnetic moment of the muon g - 2 factor discussed within the SUf(2) nonlocal chiral quark model. This is considered in the leading and, partially, in the next-to-leading orders (the effect of the fermion propagator dressing due to pion field) of expansion in small parameter 1/ N c ( N c is the number of colors in QCD).
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.
Chiral quark model of nucleon spin-flavor structure with SU(3) and axial-U(1) breakings
Cheng, T.P.; Li, L.
1998-01-01
The chiral quark model with a nonet of Goldstone bosons can yield an adequate description of the observed proton flavor and spin structure. In a previous publication we have compared the results of an SU(3) symmetric calculation with the phenomenological findings based on experimental measurements and SU(3) symmetry relations. In this paper we discuss their SU(3) and axial U(1) breaking corrections. Our result demonstrates the broad consistency of the chiral quark model with the experimental observations of the proton spin-flavor structure. With two parameters, we obtain a very satifactory fit to the F/D ratios for the octet baryon masses and for their axial vector couplings, as well as the different quark flavor contributions to the proton spin. The result also can account for not only the light quark asymmetry {bar u}{minus}{bar d} but also the strange quark content {bar s} of the proton sea. SU(3) breaking is the key in reconciling the {bar s} value as measured in the neutrino charm production and that as deduced from the pion nucleon {sigma} term. {copyright} {ital 1997} {ital The American Physical Society}
NASA Astrophysics Data System (ADS)
Ledwig, Tim; Silva, Antonio; Kim, Hyun-Chul
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/Nc 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: κTu=3.56 and κTd=1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be κTs=0.2˜-0.2, that is compatible with zero. We also calculate the corresponding form factors κTq(Q2) up to a momentum transfer Q2≤1GeV2 at a renormalization scale of 0.36GeV2.
NASA Astrophysics Data System (ADS)
Nam, Seung-il
2012-10-01
We investigate the parton-distribution functions (PDFs) for the positively charged pion and kaon at a low renormalization scale ˜1GeV. To this end, we employ the gauge-invariant effective chiral action from the nonlocal chiral-quark model, resulting in the vector currents being conserved. All the model parameters are determined phenomenologically with the normalization condition for PDF and the empirical values for the pseudoscalar meson weak-decay constants. We consider the momentum dependence of the effective quark mass properly within the model calculations. It turns out that the leading local contribution provides about 70% of the total strength for PDF, whereas the nonlocal one, which is newly taken into account in this work for the gauge invariance, does the rest. High-Q2 evolution to 27GeV2 is performed for the valance-quark distribution function, using the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation. The moments for the pion and kaon valance-quark distribution functions are also computed. The numerical results are compared with the empirical data and theoretical estimations, and show qualitatively agreement with them.
NASA Astrophysics Data System (ADS)
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2014-02-01
Although the meson decay amplitude described by a two-point function may be regarded as one of the simplest possible physical observables, it is interesting that this apparently simple amplitude bears abundant fundamental information on QCD vacuum dynamics and chiral symmetry. The light-front zero-mode issue of the vector meson decay constant fV is in this respect highly nontrivial and deserves careful analysis. We discuss the zero-mode issue in the light-front quark model (LFQM) prediction of fV from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. We extend the exactly solvable, manifestly covariant Bethe-Salpeter model calculation to the more phenomenologically accessible, realistic light-front quark model and present a self-consistent covariant description of fV, analyzing the twist-2 and twist-3 quark-antiquark distribution amplitudes with even chirality.
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. PMID:25192088
{Sigma}{sub c}D and {Lambda}{sub c}D states in a chiral quark model
Wang, W. L.; Zhang, Z. Y.; Zou, B. S.; Huang, F.
2011-07-15
The S-wave {Sigma}{sub c}D and {Lambda}{sub c}D states with isospin I=1/2 and spin S=1/2 are dynamically investigated within the framework of a chiral constituent quark model by solving a resonating group method equation. The results show that the interaction between {Sigma}{sub c} and D is attractive, which consequently results in a {Sigma}{sub c}D bound state with a binding energy of about 5-42 MeV, unlike the case of the {Lambda}{sub c}D state, which has a repulsive interaction and thus is unbound. The channel-coupling effect of {Sigma}{sub c}D and {Lambda}{sub c}D is found to be negligible owing to the fact that the gap between the {Sigma}{sub c}D and {Lambda}{sub c}D thresholds is relatively large and the {Sigma}{sub c}D and {Lambda}{sub c}D transition interaction is weak.
Scadron, Michael D.; Kleefeld, Frieder; Rupp, George
2007-02-27
Light constituent quark masses and the corresponding dynamical quark masses are determined by data, the quark-level linear {sigma} model, and infrared QCD. This allows to define effective nonstrange and strange current quark masses, which reproduce the experimental pion and kaon masses very accurately, by simple additivity. In contrast, the usual nonstrange and strange current quarks employed by the Particle Data Group and Chiral Perturbation Theory do not allow a straightforward quantitative explanation of the pion and kaon masses.
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.
NASA Astrophysics Data System (ADS)
Ledwig, Tim; Silva, Antonio; Kim, Hyun-Chul
2010-08-01
We investigate the tensor form factors of the baryon octet within the framework of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear 1/Nc rotational as well as linear ms corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors HTq(Q2) corresponding to the generalized parton distributions HT(x,ξ,t). The tensor form factors are obtained for the momentum transfer up to Q2≤1GeV2 and at a renormalization scale of 0.36GeV2. We find for the tensor charges δu=1.08, δd=-0.32, and δs=-0.01 and discuss their physical consequences, comparing them with those from other models. Results for tensor charges for the baryon octet are also given.
Confinement, quark mass functions, and spontaneous chiral symmetry breaking in Minkowski space
Biernat, Elmar P.; Gross, Franz L.; Pena, Teresa; Stadler, Alfred
2014-01-01
We formulate the covariant equations for quark-antiquark bound states in Minkowski space in the framework of the Covariant Spectator Theory. The quark propagators are dressed with the same kernel that describes the interaction between different quarks. We show that these equations are charge conjugation invariant, and that in the chiral limit of vanishing bare quark mass, a massless pseudoscalar bound state is produced in a Nambu--Jona-Lasinio (NJL) mechanism, which is associated with the Goldstone boson of spontaneous chiral symmetry breaking. In this introductory paper we test the formalism by using a simplified kernel consisting of a momentum-space $\\delta$-function with a vector Lorentz structure, to which one adds a mixed scalar and vector confining interaction. The scalar part of the confining interaction is not chirally invariant by itself, but decouples from the equations in the chiral limit and therefore allows the NJL mechanism to work. With this model we calculate the quark mass function, and we compare our Minkowski-space results to LQCD data obtained in Euclidean space. In a companion paper we apply this formalism to a calculation of the pion form factor.
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.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Ledwig, Tim; Kim, Hyun-Chul; Goeke, Klaus
2008-10-01
We investigate the vector transition form factors of the nucleon and vector meson K to the pentaquark baryon Θ within the framework of the SU(3) chiral quark-soliton model. We take into account the rotational 1/N and linear m corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. It turns out that the leading-order contributions to the form factors are almost cancelled by the rotational corrections. Because of this, the flavor SU(3) symmetry-breaking terms yield sizeable effects on the vector transition form factors. In particular, the main contribution to the electric-like transition form factor comes from the wave-function corrections, which is a consequence of the generalized Ademollo-Gatto theorem derived in the present work. We estimate with the help of the vector meson dominance the K vector and tensor coupling constants for the Θ: g=0.74-0.87 and f=0.53-1.16. We argue that the outcome of the present work is consistent with the null results of the CLAS experiments in the reactions γn→KΘ and γp→KΘ. The results of the present work are also consistent with the recent experiments at KEK. In addition, we present the results of the Σ→NK transition form factors and its KNΣ coupling constants.
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.
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.
NASA Astrophysics Data System (ADS)
Maslow, Joel Neal
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 we assume 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 (qq) 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.
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.
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.
NASA Astrophysics Data System (ADS)
Alkofer, Reinhard; Fischer, Christian S.; Llanes-Estrada, Felipe J.; Schwenzer, Kai
2009-01-01
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)
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.
Thermodynamics of lattice QCD with 2 quark flavours : chiral symmetry and topology.
Lagae, J.-F.
1998-06-09
We have studied the restoration of chiral symmetry in lattice QCD at the finite temperature transition from hadronic matter to a quark-gluon plasma. By measuring the screening masses of flavour singlet and non-singlet meson excitations, we have seen evidence that, although flavour chiral symmetry is restored at this transition, flavour singlet (U(1)) axial symmetry is not. We conclude that this indicates that instantons continue to play an important role in the quark-gluon plasma phase.
Gravitational catalysis of chiral and color symmetry breaking of quark matter in hyperbolic space
Ebert, D.; Tyukov, A. V.; Zhukovsky, V. Ch.
2009-10-15
We study the dynamical breaking of chiral and color symmetries of dense quark matter in the ultrastatic hyperbolic spacetime R x H{sup 3} in the framework of an extended Nambu-Jona-Lasinio model. On the basis of analytical expressions for chiral and color condensates as functions of curvature and temperature, the phenomenon of dimensional reduction and gravitational catalysis of symmetry breaking in strong gravitational field is demonstrated in the regime of weak coupling constants. In the case of strong couplings it is shown that curvature leads to small corrections to the flat-space values of condensate and thus enhances the symmetry breaking effects. Finally, using numerical calculations phase transitions under the influence of chemical potential and negative curvature are considered and the phase portrait of the system is constructed.
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}
Thomas Mehen; Brian C. Tiburzi
2006-07-17
We extend the chiral Lagrangian with heavy quark-diquark symmetry to quenched and partially quenched theories. These theories are used to derive formulae for the chiral extrapolation of masses and hyperfine splittings of doubly heavy baryons in lattice QCD simulations. A quark-diquark symmetry prediction for the hyperfine splittings of heavy mesons and doubly heavy baryons is rather insensitive to chiral corrections in both quenched and partially quenched QCD. Extrapolation formulae for the doubly heavy baryon electromagnetic transition moments are also determined for the partially quenched theory.
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.
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 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
Relativistic quantum model of confinement and the current quark masses
NASA Astrophysics Data System (ADS)
Soloviev, L. D.
1998-08-01
We consider a relativistic quantum model of confined massive spinning quarks and antiquarks which describes the leading Regge trajectories of mesons. The quarks are described by the Dirac equations and the gluon contribution is approximated by the Nambu-Goto straight-line string. The string tension and the current quark masses are the main parameters of the model. Additional parameters are phenomenological constants which approximate nonstring short-range contributions. A comparison of the measured meson masses with the model predictions allows one to determine the current quark masses (in MeV) to be ms=227+/-5, mc=1440+/-10, and mb=4715+/-20. The chiral SU3 model makes it possible to estimate from here the u- and d-quark masses to be mu=6.2+/-0.2 Mev and md=11.1+/-0.4 Mev.
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.
NASA Astrophysics Data System (ADS)
Kobayashi, Makoto
2014-11-01
After a short review of the activities of Shoichi Sakata and his group, how the six-quark model explains CP violation is described. Experimental verification of the model at the B-factories is also briefly discussed.
Chiral vortical wave and induced flavor charge transport in a rotating quark-gluon plasma
NASA Astrophysics Data System (ADS)
Jiang, Yin; Huang, Xu-Guang; Liao, Jinfeng
2015-10-01
We show the existence of a new gapless collective excitation in a rotating fluid system with chiral fermions, named the chiral vortical wave (CVW). The CVW has its microscopic origin at the quantum anomaly and macroscopically arises from interplay between vector and axial charge fluctuations induced by vortical effects. The wave equation is obtained both from hydrodynamic current equations and from chiral kinetic theory, and its solutions show nontrivial CVW-induced charge transport from different initial conditions. Using the rotating quark-gluon plasma in heavy ion collisions as a concrete example, we show the formation of an induced flavor quadrupole in quark-gluon plasma and estimate the elliptic flow splitting effect for Λ baryons that may be experimentally measured.
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.
Semiclassical projection of hedgehog models with quarks
Cohen, T.D.; Broniowski, W.
1986-12-01
A simple semiclassical method is presented for calculating physical observables in states with good angular momentum and isospin for models whose mean-field solutions are hedgehogs. The method is applicable for theories which have both quark and meson degrees of freedom. The basic approach is to find slowly rotating solutions to the time-dependent mean-field equations. A nontrivial set of differential equations must be solved to find the quark configuration for these rotating hedgehogs. The parameters which specify the rotating solutions are treated as the collective degrees of freedom. They are requantized by imposing a set of commutation relations which ensures the correct algebra for the SU(2) x SU(2) group of angular momentum and isospin. Collective wave functions can then be found and with these wave functions all matrix elements can be calculated. The method is applied to a simple version of the chiral quark-meson model. A number of physical quantities such as magnetic moments, charge distributions, g/sub A/, g/sub ..pi..//sub N//sub N/, N-..delta.. mass splitting, properties of the N-..delta.. transition, etc., are calculated.
Semiclassical projection of hedgehog models with quarks
NASA Astrophysics Data System (ADS)
Cohen, Thomas D.; Broniowski, Wojciech
1986-12-01
A simple semiclassical method is presented for calculating physical observables in states with good angular momentum and isospin for models whose mean-field solutions are hedgehogs. The method is applicable for theories which have both quark and meson degrees of freedom. The basic approach is to find slowly rotating solutions to the time-dependent mean-field equations. A nontrivial set of differential equations must be solved to find the quark configuration for these rotating hedgehogs. The parameters which specify the rotating solutions are treated as the collective degrees of freedom. They are requantized by imposing a set of commutation relations which ensures the correct algebra for the SU(2)×SU(2) group of angular momentum and isospin. Collective wave functions can then be found and with these wave functions all matrix elements can be calculated. The method is applied to a simple version of the chiral quark-meson model. A number of physical quantities such as magnetic moments, charge distributions, gA, gπNN, N-Δ mass splitting, properties of the N-Δ transition, etc., are calculated.
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.
Nucleon quark distributions in a covariant quark-diquark model
Ian Cloet; W. Bentz; Anthony Thomas
2005-04-01
Spin-dependent and spin-independent quark light-cone momentum distributions and structure functions 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 Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquarks channels are included. We find excellent agreement between our model results and empirical data.
Stability of Quark Star Models
NASA Astrophysics Data System (ADS)
M., Azam; S. A., Mardan; M. A., Rehman
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.
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.
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)
Compact stars with a quark core within the Nambu-Jona-Lasinio (NJL) model
Lenzi, C. H.; Schneider, A. S.; Providencia, C.; Marinho, R. M. Jr.
2010-07-15
An ultraviolet cutoff dependent on the chemical potential as proposed by Casalbuoni et al. is used in the SU(3) Nambu-Jona-Lasinio model. The model is applied to the description of stellar quark matter and compact stars. It is shown that with a new cutoff parametrization it is possible to obtain stable hybrid stars with a quark core. A larger cutoff at finite densities leads to a partial chiral symmetry restoration of quark s at lower densities. A direct consequence is the onset of the s quark in stellar matter at lower densities and a softening of the equation of state.
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.
The Soliton-Soliton Interaction in the Chiral Dilaton Model
NASA Astrophysics Data System (ADS)
Mantovani-Sarti, Valentina; Park, Byung-Yoon; Vento, Vicente
2013-10-01
We study the interaction between two B = 1 states in the Chiral Dilaton Model where baryons are described as nontopological solitons arising from the interaction of chiral mesons and quarks. By using the hedgehog solution for B = 1 states we construct, via a product ansatz, three possible B = 2 configurations to analyse the role of the relative orientation of the hedgehog quills in the dynamics of the soliton-soliton interaction and investigate the behavior of these solutions in the range of long/intermediate distance. One of the solutions is quite binding due to the dynamics of the π and σ fields at intermediate distance and should be used for nuclear matter studies. Since the product ansatz break down as the two solitons get close, we explore the short range distance regime with a model that describes the interaction via a six-quark bag ansatz. We calculate the interaction energy as a function of the inter-soliton distance and show that for small separations the six quarks bag, assuming a hedgehog structure, provides a stable bound state that at large separations connects with a special configuration coming from the product ansatz.
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.
Lattice QCD analysis for relation between quark confinement and chiral symmetry breaking
NASA Astrophysics Data System (ADS)
Doi, Takahiro M.; Suganuma, Hideo; Iritani, Takumi
2016-01-01
The Polyakov loop and the Dirac modes are connected via a simple analytical relation on the temporally odd-number lattice, where the temporal lattice size is odd with the normal (nontwisted) periodic boundary condition. Using this relation, we investigate the relation between quark confinement and chiral symmetry breaking in QCD. In this paper, we discuss the properties of this analytical relation and numerically investigate each Dirac-mode contribution to the Polyakov loop in both confinement and deconfinement phases at the quenched level. This relation indicates that low-lying Dirac modes have little contribution to the Polyakov loop, and we numerically confirmed this fact. From our analysis, it is suggested that there is no direct one-to-one corresponding between quark confinement and chiral symmetry breaking in QCD. Also, in the confinement phase, we numerically find that there is a new "positive/negative symmetry" in the Dirac-mode matrix elements of link-variable operator which appear in the relation and the Polyakov loop becomes zero because of this symmetry. In the deconfinement phase, this symmetry is broken and the Polyakov loop is non-zero.
Baryon resonances without quarks: A chiral soliton perspective
Karliner, M.
1987-03-01
In many processes involving low momentum transfer it is fruitful to regard the nucleon as a soliton or ''monopole-like'' configuration of the pion field. In particular, within this framework it is possible to obtain detailed predictions for pion-nucleon scattering amplitudes and for properties of baryon resonances. One can also derive model-independent linear relations between scattering amplitudes, such as ..pi..N and anti KN. A short survey of some recent results is given, including comparison with experimental data.
Exploring the nature of chiral phase transition in two-flavor QCD using extra heavy quarks
NASA Astrophysics Data System (ADS)
Ejiri, Shinji; Iwami, Ryo; Yamada, Norikazu
2016-03-01
Chiral phase transition of two-flavor QCD at finite quark masses is known to be a crossover except near the chiral limit, but it can turn to a first order transition when adding many extra flavors. This property is used to explore the nature of the phase transition of massless two-flavor QCD using lattice numerical simulations. The extra heavy flavors being incorporated in the form of the hopping parameter expansion through the reweighting, the number of the extra flavors and their masses appear only in a single parameter, defined by h . We determine the critical value of h , at which the first order and the crossover regions are separated, and examine its dependence on the two-flavor mass. The lattice calculations are carried out at Nt=4 , and show that the critical value of h does not depend on the two-flavor mass in the range we have studied (0.46 ≤mπ/mρ≤0.66 ) and appears to remain finite and positive in the chiral limit, suggesting that the phase transition of massless two-flavor QCD is of second order.
CHIRAL MODEL FOR DENSE, HOT AND STRANGE HADRONIC MATTER
ZSCHIESCHE,D.; PAPAZOGLOU,P.; BECKMANN,C.W.; SCHRAMM,S.; SCHAFFNER-BIELICH,J.; STOCKER,H.; GREINER,W.
1999-06-10
Until now it is not possible to determine the equation of state (EOS) of hadronic matter from QCD. One successfully applied alternative way to describe the hadronic world at high densities and temperatures are effective models like the RMF-models, where the relevant degrees of freedom are baryons and mesons instead of quarks and gluons. Since approximate chiral symmetry is an essential feature of QCD, it should be a useful concept for building and restricting effective models. It has been shown that effective {sigma}-{omega}-models including SU(2) chiral symmetry are able to obtain a reasonable description of nuclear matter and finite nuclei. Recently [4] the authors have shown that an extended SU(3) x SU(3) chiral {sigma}-{omega} model is able to describe nuclear matter ground state properties, vacuum properties and finite nuclei satisfactorily. This model includes the lowest SU(3) multiplets of the baryons (octet and decuplet), the spin-0 and the spin-1 mesons as the relevant degrees of freedom. Here they discuss the predictions of this model for dense, hot, and strange hadronic matter.
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.
Analysis of the QCD spectrum and chiral symmetry breaking with varying quark masses
Simonov, Yu. A.
2013-04-15
The meson spectrum of QCD is studied in the framework of nonperturbative QCD as a function of varying quark masses m{sub q}. It is shown that the total spectrum consists of two branches: 1) the standard one, which may be called the flux-tube spectrum, depending approximately linearly on m{sub q}, and 2) the chiral symmetry breaking (CSB) spectrum for pseudoscalar (PS) flavor nonsinglet mesons with mass dependence {radical}m{sub q}. The formalism for PS mesons is derived from the QCD Lagrangian with m{sub q} corrections, and a unified form of the PS propagator was derived. It is shown that the CSB branch of PS mesons joins to the flux-tube branch at around m{sub q} = 200 MeV. All these results are in close correspondence with recent numerical data on large lattices.
Thermodynamics of lattice QCD with massless quarks and chiral 4-fermion interactions.
Kogut, J. B.
1998-10-30
N{sub f} = 2 lattice QCD with massless quarks and a weak 4-fermion interaction appears to have the expected second order transition, at least for N{sub t} {ge} 6. More work is needed to clarify the N{sub t} = 4 case. With more statistics the N{sub t} = 6 simulations should produce an accurate determination of the critical exponent {beta}{sub m}. Moving to finite mass at {beta} = {beta}{sub c} should allow an accurate determination of {sigma}. Hadronic screening masses need further analysis. Other order parameters remain to be analyzed. Unfortunately, there is no obvious way to include 4-fermion interactions with full SU(2) x SU(2) chiral flavor symmetry.
Chiral phase transition in the soft-wall model of AdS/QCD
NASA Astrophysics Data System (ADS)
Chelabi, Kaddour; Fang, Zhen; Huang, Mei; Li, Danning; Wu, Yue-Liang
2016-04-01
We investigate the chiral phase transition in the soft-wall model of AdS/QCD at zero chemical potential for two-flavor and three-flavor cases, respectively. We show that there is no spontaneous chiral symmetry breaking in the original soft-wall model. After detailed analysis, we find that in order to realize chiral symmetry breaking and restoration, both profiles for the scalar potential and the dilaton field are essential. The scalar potential determines the possible solution structure of the chiral condensate, except the mass term, it takes another quartic term for the two-flavor case, and for the three-flavor case, one has to take into account an extra cubic term due to the t'Hooft determinant interaction. The profile of the dilaton field reflects the gluodynamics, which is negative at a certain ultraviolet scale and approaches positive quadratic behavior at far infrared region. With this set-up, the spontaneous chiral symmetry breaking in the vacuum and its restoration at finite temperature can be realized perfectly. In the two-flavor case, it gives a second order chiral phase transition in the chiral limit, while the transition turns to be a crossover for any finite quark mass. In the case of three-flavor, the phase transition becomes a first order one in the chiral limit, while above sufficient large quark mass it turns to be a crossover again. This scenario agrees exactly with the current understanding on chiral phase transition from lattice QCD and other effective model studies.
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.
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)
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.
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.
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
NASA Astrophysics Data System (ADS)
Hayata, Tomoya; Yamamoto, Arata
2015-05-01
We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
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.
Mean field theory of the linear sigma-model: chiral solitons
Kahana, S.; Ripka, G.
1983-01-01
The mean field theory of the chiral invariant sigma-model is outlined. bound states (solitons) of valence quarks are obtained self-consistently using a hedgehog shape for the pion field. A schematic model for the coupled fermion-boson fields is presented. Renormalization is worked out for the fermion one-loop corrections and numerical results presented for the purely scalar-field case. The interpretation of the baryon number of the perturbed vacuum is considered.
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.
Quantum group extended chiral p-models
NASA Astrophysics Data System (ADS)
Hadjiivanov, L. K.; Paunov, R. R.; Todorov, I. T.
1991-06-01
The quantum symmetry group U q of an extended chiral conformal model is determined by the requirement that symmetry transformations commute with braid group statistics operators and by the relation between fusion rules and tensor product expansions of a certain class of U 4 representations. For thermal minimal " p-models", involving no more than p - 1 unitary lowest weight representations of the Virasoro algebra Vir, U 4 is the quantum universal enveloping (QUE) algebra U 4(sl(2)) with deformation parameter q satisfying q + q-1 = 2 cos π/ p ( qp = - 1, p = 4, 5,…). To each 2-dimensional local field labelled by a pair of nonnegative integers v, v¯ (0 ⩽ v, v¯ ⩽ p - 2) we make correspond an analytic chiral field φv, of weight Δ vand q- spin I v¯. The correlation functions of φv, transform under an 1-dimensional unitary representation of the braid group. As a result we reproduce the ADE classification of 2-dimensional p models in terms of their extended chiral counterparts. It turns out that U q-extended chiral p-models always involve non-unitary and indecomposable representations of Vir.
NASA Astrophysics Data System (ADS)
Pagura, V.; Gómez Dumm, D.; Scoccola, N. N.
2012-01-01
We study the deconfinement and chiral restoration transitions in the context of non-local PNJL models, considering the impact of the presence of dynamical quarks on the scale parameter appearing in the Polyakov potential. We show that the corresponding critical temperatures are naturally entangled for both zero and imaginary chemical potential, in good agreement with lattice QCD results. We also analyze the Roberge-Weiss transition, which is found to be first order at the associated endpoint.
Preskill, J.
1982-01-01
Calculability of quark and lepton masses and mixing angles is stressed as the primary motivation for constructing models in which quarks and leptons are composite particles. A general strategy for constructing such models is outlined, in which quarks and leptons are kept light compared to their inverse sizes by approximate chiral symmetries. The origin of multiple families is discussed, and an unrealistic model is exhibited which has several generations and a complicated pattern of masses and generation-mixing angles. The new physics responsible for binding quarks and leptons tends to induce various rare processes at rates which are potentially too large.
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.
NASA Astrophysics Data System (ADS)
Ma, Ernest; Melić, Blaženka
2013-10-01
A model proposed in 2004 using the non-Abelian discrete symmetry S3 for understanding the flavor structure of quarks and leptons is updated, with special focus on the quark and scalar sectors. We show how the approximate residual symmetries of this model explain both the pattern of the quark mixing matrix and why the recently observed particle of 126 GeV at the Large Hadron Collider is so much like the one Higgs boson of the Standard Model. We identify the strongest phenomenological bounds on the scalar masses of this model, and predict a possibly observable decay b → sτ-μ+ (Bs →τ+μ-), but not b → sτ+μ- (Bs →τ-μ+).
Exotic multi-quark states in the deconfined phase from gravity dual models
NASA Astrophysics Data System (ADS)
Burikham, P.; Chatrabhuti, A.; Hirunsirisawat, E.
2009-05-01
In the deconfined phase of quark-gluon plasma, it seems that most of the quarks, antiquarks and gluons should be effectively free in the absence of the linear confining potential. However, the remaining Coulomb-type potential between quarks in the plasma could still be sufficiently strong that certain bound states, notably of heavy quarks such as J/ψ are stable even in the deconfined plasma up to a certain temperature. Baryons can also exist in the deconfined phase provided that the density is sufficiently large. We study three kinds of exotic multi-quark bound states in the deconfined phase of quark-gluon plasma from gravity dual models in addition to the normal baryon. They are k-baryon, (N+bar k)-baryon and a bound state of j mesons which we call ``j-mesonance''. Binding energies and screening lengths of these exotic states are studied and are found to have similar properties to those of mesons and baryons at the leading order. Phase diagram for the exotic nuclear phases is subsequently studied in the Sakai-Sugimoto model. Even though the exotics are less stable than normal baryons, in the region of high chemical potential and low temperature, they are more stable thermodynamically than the vacuum and chiral-symmetric quark-gluon plasma phases (χS-QGP).
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.
Three-flavor chiral effective model with four baryonic multiplets within the mirror assignment
NASA Astrophysics Data System (ADS)
Olbrich, Lisa; Zétényi, Miklós; Giacosa, Francesco; Rischke, Dirk H.
2016-02-01
In the case of three quark flavors, (pseudo)scalar diquarks transform as antiquarks under chiral transformations. We construct four spin-1 /2 baryonic multiplets from left- and right-handed quarks as well as left- and right-handed diquarks. The fact that two of these multiplets transform in a "mirror" way allows for chirally invariant mass terms. We then embed these baryonic multiplets into the Lagrangian of the so-called extended linear sigma model, which features (pseudo)scalar and (axial-)vector mesons, as well as glueballs. Reducing the Lagrangian to the two-flavor case, we obtain four doublets of nucleonic states. These mix to produce four experimentally observed states with definite parity: the positive-parity nucleon N (939 ) and Roper resonance N (1440 ), as well as the negative-parity resonances N (1535 ) and N (1650 ). We determine the parameters of the nucleonic part of the Lagrangian from a fit to masses and decay properties of the aforementioned states. Studying the limit of vanishing quark condensate, we conclude that N (939 ) and N (1535 ), as well as N (1440 ) and N (1650 ), form pairs of chiral partners.
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.
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.
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.
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.
Exotic quarks in Twin Higgs models
NASA Astrophysics Data System (ADS)
Cheng, Hsin-Chia; Jung, Sunghoon; Salvioni, Ennio; Tsai, Yuhsin
2016-03-01
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 the 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. Depending on the details of the twin sector, the exotic quarks may be probed up to ˜ 2.5TeV at the LHC and beyond 10TeV at a future 100TeV collider, providing a strong test of this class of ultraviolet completions.
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
The Bonn nuclear quark model revisited
Providencia, Constanca; Providencia, Joao da Cordeiro, Flavio; Yamamura, Masatoshi; Tsue, Yasuhiko; Nishiyama, Seiya
2009-08-15
We present the exact solutions to the equations of the lowest energy states of the colored and color-symmetric sectors of the Bonn quark model, which is SU(3) symmetric and is defined in terms of an effective pairing force with su(4) algebraic structure. We show that the groundstate of the model is not color symmetrical except for a narrow interval in the range of possible quark numbers. We also study the performance of the Glauber coherent state, as well as of superconducting states of the BCS type, with respect to the description, not only of the absolute (colored) groundstate, but also of the minimum energy state of the color-symmetrical sector, finding that it is remarkably good. We use the model to discuss, in a schematic context, some controversial aspects of the conventional treatment of color superconductivity.
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.
Spontaneous 1 chiral symmetry breaking in model bacterial suspensions
NASA Astrophysics Data System (ADS)
Breier, Rebekka; Selinger, Robin; Ciccotti, Giovanni; Herminghaus, Stephan; Mazza, Marco G.
2015-03-01
Chiral symmetry breaking is ubiquitous in biological systems, from DNA to bacterial suspensions. A key unresolved problem is how chiral structures may spontaneously emerge from achiral interactions. We study a simple model of bacterial suspensions in three dimensions that effectively incorporates active motion and hydrodynamic interactions. We perform large-scale molecular dynamics simulations (up to 106 particles) and describe stable (or long-lived metastable) collective states that exhibit chiral organization although the interactions are achiral. We elucidate under which conditions these chiral states will emerge and grow to large scales. We also study a related equilibrium model that clarifies the role of orientational fluctuations.
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.
Confronting effective models for deconfinement in dense quark matter with lattice data
NASA Astrophysics Data System (ADS)
Andersen, Jens O.; Brauner, Tomáš; Naylor, William R.
2015-12-01
Ab initio numerical simulations of the thermodynamics of dense quark matter remain a challenge. Apart from the infamous sign problem, lattice methods have to deal with finite volume and discretization effects as well as with the necessity to introduce sources for symmetry-breaking order parameters. We study these artifacts in the Polyakov-loop-extended Nambu-Jona-Lasinio (PNJL) model and compare its predictions to existing lattice data for cold and dense two-color matter with two flavors of Wilson quarks. To achieve even qualitative agreement with lattice data requires the introduction of two novel elements in the model: (i) explicit chiral symmetry breaking in the effective contact four-fermion interaction, referred to as the chiral twist, and (ii) renormalization of the Polyakov loop. The feedback of the dense medium to the gauge sector is modeled by a chemical-potential-dependent scale in the Polyakov-loop potential. In contrast to previously used analytical Ansätze, we determine its dependence on the chemical potential from lattice data for the expectation value of the Polyakov loop. Finally, we propose adding a two-derivative operator to our effective model. This term acts as an additional source of explicit chiral symmetry breaking, mimicking an analogous term in the lattice Wilson action.
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.
NASA Astrophysics Data System (ADS)
Zhevlakov, A. S.; Radzhabov, A. E.; Dorokhov, A. E.
2010-11-01
The muon contribution to the anomalous magnetic moment from light-by-light scattering diagrams with pion participation is calculated for a nonlocal chiral quark model. For various nonlocal model parameterizations, the contribution makes a μ Had,LbL = 5.1(0.2) 10-10. Later on, we plan to calculate contributions from diagrams with an intermediate scalar meson and quark boxing.
NASA Astrophysics Data System (ADS)
Samart, Daris; Nualchimplee, Chakrit; Yan, Yupeng
2016-06-01
In this work we construct a chiral SU(3) Lagrangian with D mesons of spin JP=0- and JP=1- and charmed baryons of spin JP=1 /2+ and JP=3 /2+. There are 42 leading two-body counterterms involving two charmed baryon fields and two D meson fields in the constructed Lagrangian. The heavy-quark spin symmetry leads to 35 sum rules, while the large-Nc operator analysis predicts 29 at the next-to leading order of the 1 /Nc expansion. The combination of the sum rules from both the heavy-quark symmetry and the large-Nc analysis results in 38 independent sum rules, which reduces the number of free parameters in the chiral Lagrangian to only four. This is a remarkable result demonstrating the consistency of the heavy-quark symmetry and large-Nc operator analysis.
NASA Astrophysics Data System (ADS)
Thacker, H. B.; Xiong, Chi; Kamat, Ajinkya S.
2011-11-01
The Witten-Sakai-Sugimoto construction of holographic QCD in terms of D4 color branes and D8 flavor branes in type IIA string theory is used to investigate the role of topological charge in the chiral dynamics of quarks in QCD. The QCD theta term arises from a compactified five-dimensional Chern-Simons term on the D4 branes. This term couples the QCD topological charge to the Ramond-Ramond (RR) U(1) gauge field of type IIA string theory. For large Nc the contribution of instantons (D0 branes) is suppressed, and the nonzero topological susceptibility of pure-glue QCD is attributed to the presence of D6 branes, which constitute magnetic sources of the RR gauge field. The topological charge of QCD is required, by an anomaly inflow argument, to coincide in space-time with the intersection of the D6 branes and the D4 color branes. This clarifies the relation between D6 branes and the coherent, codimension-one topological charge membranes observed in QCD Monte Carlo calculations. Using open-string/closed-string duality, we interpret a quark loop (represented by a D4-D8 open-string loop) in terms of closed-string exchange between color and flavor branes. The role of the RR gauge field in quark-antiquark annihilation processes is discussed. RR exchange in the s-channel generates a 4-quark contact term which produces an η' mass insertion and provides an explanation for the observed spin-parity structure of the Okubo-Zweig-Iizuka rule. The (logDetU)2 form of the U(1) anomaly emerges naturally. RR exchange in the t-channel of the qq¯ scattering amplitude produces a Nambu-Jona-Lasinio interaction which may provide a mechanism for spontaneous breaking of SU(Nf)×SU(Nf).
Orbital structure of quarks inside the nucleon in the light-cone diquark model
Lu Zhun; Schmidt, Ivan
2010-11-01
We study the orbital angular momentum structure of the quarks inside the proton. By employing the light-cone diquark model and the overlap representation formalism, we calculate the chiral-even generalized parton distribution functions H{sub q}(x,{xi},{Delta}{sup 2}), H-tilde{sub q}(x,{xi},{Delta}{sup 2}), and E{sub q}(x,{xi},{Delta}{sup 2}) at zero skewedness for q=u and d quarks. In our model, E{sub u} and E{sub d} have opposite sign with similar size. Those generalized parton distribution functions are applied to calculate the orbital angular momentum distributions, showing that L{sub u}(x) is positive, while L{sub d}(x) is consistent with zero compared with L{sub u}(x). We introduce the impact parameter dependence of the quark orbital angular momentum distribution. It describes the position space distribution of the quark orbital angular momentum at given x. We found that the impact parameter dependence of the quark orbital angular momentum distribution is axially symmetric in the light-cone diquark model.
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.
Currents, charges, and canonical structure of pseudodual chiral models
Curtright, T. ); Zachos, C. )
1994-05-15
We discuss the pseudodual chiral model to illustrate a class of two-dimensional theories which have an infinite number of conservation laws but allow particle production, at variance with naive expectations. We describe the symmetries of the pseudodual model, both local and nonlocal, as transmutations of the symmetries of the usual chiral model. We refine the conventional algorithm to more efficiently produce the nonlocal symmetries of the model, and we discuss the complete local current algebra for the pseudodual theory. We also exhibit the canonical transformation which connects the usual chiral model to its fully equivalent dual, further distinguishing the pseudodual theory.
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.
Nebreda, J.; Pelaez, J. R.
2010-08-05
We study the strange and non-strange quark mass dependence of the parameters of the f{sub 0}(600),{kappa}(800), {rho}(770) and K*(892) resonances generated from elastic meson-meson scattering using unitarized one-loop Chiral Perturbation Theory. We fit simultaneously all experimental scattering data up to 0.8-1 GeV together with lattice results on decay constants and scattering lengths up to a pion mass of 440 MeV. Then, the strange and non-strange quark masses are varied from the chiral limit up to values of interest for lattice studies. In these amplitudes, the mass and width of the {rho}(770) and K*(892) present a similar and smooth quark mass dependence. In contrast, both scalars present a similar non-analyticity at high quark masses. Nevertheless the f{sub 0}(600) dependence on both quark masses is stronger than for the {kappa}(800) and the vectors. We also confirm the lattice assumption of quark mass independence of the vector two-meson coupling that, in contrast, is violated for scalars.
Mesoscopic modelling of colloids in chiral nematics.
Ravnik, Miha; Alexander, Gareth P; Yeomans, Julia M; Zumer, Slobodan
2010-01-01
We present numerical modelling of colloidal particles in chiral nematics with cubic symmetry (blue phases) within the framework of the Landau-de Gennes free energy. The interaction potential of a single, nano-sized colloidal particle with a -1/2 disclination line is calculated as a generic trapping mechanism for particles within the cholesteric blue phases. The interaction potential is shown to be highly anisotropic and have threefold rotational symmetry. We discuss the equilibration of the colloidal texture with respect to particle positions and the unit cell size of the blue phase. We also describe how preservation of the liquid crystal volume and the number of particles allows blue phase colloidal structures with different unit cell sizes and configurations to be compared numerically. PMID:20158028
Light quarks in the screened dyon-antidyon Coulomb liquid model. II.
NASA Astrophysics Data System (ADS)
Liu, Yizhuang; Shuryak, Edward; Zahed, Ismail
2015-10-01
We discuss an extension of the dyon-antidyon liquid model that includes light quarks in the dense center symmetric phase. In this work, like in our previous one, we use the simplest color SU(2) group. We start with a single fermion flavor Nf=1 and explicitly map the model onto a three-dimensional quantum effective theory with a fermion that is only UV(1 ) symmetric. We use it to show, in the mean-field approximation, that in the dense center, the symmetric regime leads to the nonzero chiral condensate. We estimate its value and the σ ,η meson masses. We then extend our analysis to an arbitrary number of quark flavors Nf>1 and colors Nc>2 and show that in the dense plasma phase the spontaneous chiral symmetry breaking disappears when Nf/Nc≥2 . A reorganization of the ensemble into a gas of dyon-antidyon molecules restores chiral symmetry but may still preserve center symmetry in the linearized approximation.
Phase diagram of chiral quark matter: From weakly to strongly coupled Fulde-Ferrell phase
Sedrakian, Armen; Rischke, Dirk H.
2009-10-01
We calculate the phase diagram of two-flavor quark matter within the Nambu-Jona-Lasinio (NJL) model in the temperature-flavor asymmetry plane in the case where there are three competing phases: the homogeneous Bardeen-Cooper-Schrieffer (BCS) phase, the unpaired phase, and a phase with broken spatial symmetry, which is here taken to be the counterpart of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in condensed matter physics. The system belongs to the universality class of paramagnetic-ferromagnetic-helical systems, and therefore contains a tricritical Lifshitz point in its phase diagram, where the momentum scale characterizing the breaking of translational invariance has a critical exponent of 1/2 to leading order. Upon varying the coupling constant of the theory we find that in weak coupling, the FFLO phase is favored at arbitrary flavor asymmetries for sufficiently low temperatures; at intermediate coupling its occupancy domain is shifted towards larger asymmetries. Strong coupling features a new regime of an inhomogeneous FF state, which we identify with a current-carrying Bose-Einstein condensate of tightly bound up and down quarks. The temperature and asymmetry dependence of the gap function is studied. It is shown that the anomalous temperature dependence of the gap in the homogeneous, flavor-asymmetric phase is transformed into a normal dependence (self-similar to the BCS phase) at arbitrary coupling, once the FF phase is allowed for. We analyze the occupation numbers and the Cooper-pair wave function and show that when the condensate momentum is orthogonal to the particle momentum the minority component contains a blocking region (breach) around the Fermi sphere in the weak-coupling limit, which engulfs more low-momentum modes as the coupling is increased, and eventually leads to a topological change in strong coupling, where the minority Fermi sphere contains either two occupied strips or an empty sphere. For nonorthogonal momenta, the blocking
Inverse magnetic catalysis and confinement within a contact interaction model for quarks
NASA Astrophysics Data System (ADS)
Ahmad, A.; Raya, A.
2016-06-01
We evaluate the impact of an external magnetic field on the chiral symmetry and confinement–deconfinement transition temperatures by using a vector–vector contact interaction model for quarks regularized so as to include an explicit confining scale in the corresponding gap equation. Exploring the evolution of the chiral condensate and the confining scale with temperature T and magnetic field strength eB (e represents the fundamental electric charge), we determine the pseudo-critical temperatures for the chiral ({T}cχ ) and deconfinement (T c c ) transitions from their inflection points, respectively. By construction, {T}cχ ={T}cc in the chiral limit. Within a mean-field approximation, we observe the magnetic catalysis phenomenon, characterized by a rising behavior of {T}cχ and T c c with growing eB. By considering a lattice-inspired running coupling which monotonically decreases with eB, inverse magnetic catalysis takes place in our model. We explore the role of the magnetic field in the traits of the confinement–deconfinement transition described by the model. Our findings are also in agreement with predictions derived from effective models of strong interactions.
Chiral field theories as models for hadron substructure
Kahana, S.H.
1987-03-01
A model for the nucleon as soliton of quarks interacting with classical meson fields is described. The theory, based on the linear sigma model, is renormalizable and capable of including sea quarks straightforwardly. Application to nuclear matter is made in a Wigner-Seitz approximation.
NASA Astrophysics Data System (ADS)
Tiwari, Vivek Kumar
2013-10-01
We are computing the modifications for the scalar and pseudoscalar meson masses and mixing angles due to the proper accounting of fermionic vacuum fluctuation in the framework of the generalized 2+1 flavor quark meson model and the Polyakov loop augmented quark meson model (PQM). The renormalized contribution of the divergent fermionic vacuum fluctuation at one loop level makes these models effective QCD-like models. It has been explicitly shown that analytical expressions for the model parameters, meson masses, and mixing angles do not depend on any arbitrary renormalization scale. We have investigated how the incorporation of fermionic vacuum fluctuation in quark meson and PQM models qualitatively and quantitatively affects the convergence in the masses of the chiral partners in pseudoscalar (π,η,η',K) and scalar (σ,a0,f0,κ) meson nonets as the temperature is varied on the reduced temperature scale. Comparison of present results in the quark meson model with vacuum term and the PQM model with vacuum term with the already existing calculations in the bare 2+1 quark meson and PQM models shows that the restoration of chiral symmetry becomes smoother due to the influence of the fermionic vacuum term. We find that the melting of the strange condensate registers a significant increase in the presence of the fermionic vacuum term and its highest melting is found in the PQM model with vacuum term. The role of the UA(1) anomaly in determining the isoscalar masses and mixing angles for the pseudoscalar (η and η') and scalar (σ and f0) meson complex has also been significantly modified due to the fermionic vacuum correction. In its influence, the interplay of chiral symmetry restoration and the setting up of the UA(1) restoration trends have also been shown to be significantly modified.
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
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.
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
Semileptonic meson decays in the quark model: An update
D. Scora; N. Isgur
1995-03-01
The authors present the predictions of ISGW2, an update of the ISGW quark model for semileptonic meson decays. The updated model incorporates a number of features which should make it more reliable, including the constraints imposed by Heavy Quark Symmetry, hyperfine distortions of wave-functions, and form factors with more realistic high recoil behaviors.
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.
Ward identities and the analogous Goldberger-Treiman relation in a three-flavor Spectral Quark Model
NASA Astrophysics Data System (ADS)
Reis, E. A.; Mota, A. L.; Dias, E. W.
2016-04-01
This work presents the first results of an extension of the spectral quark model which includes different flavors. The spectral quark model is an approach based on a generalization of the Lehmann representation for the quark propagator. Gauge and chiral invariance are ensured with the help of gauge technique which provides particular solutions to the Ward-Takahashi identities. General conditions on the quark spectral function follow from natural physical requirements. In particular, the function is normalized, its positive momenta must vanish, while the physical observables depend on negative moments and the so-called log moments. As a consequence, the model is made finite. To allow the description of mesons constituted by different flavors of quarks we introduce different spectral functions and obtain vertex functions constructed from Ward-Takahashi identities that includes two different spectral (constituent) quark masses, allowing the physical description of strange mesons, for example. We obtain some observables based on the current approach and, in particular, the spectral version of the Kaon analogous Goldberger-Treiman relation.
CP Violation in Six Quark Scheme -- Legacy of Sakata Model
NASA Astrophysics Data System (ADS)
Kobayashi, Makoto
2015-03-01
After a short review of the activities of Shoichi Sakata and his group, how the six-quark model explains CP violation is described. Experimental verification of the model at the B-factories is also briefly discussed.
Barnes, T. |
1992-12-31
In this talk I summarize recent calculations of meson-meson scattering amplitudes in the nonrelativistic quark potential model, which assume that the scattering mechanism is one-gluon-exchange followed by constituent exchange (OGE+CEX). We refer to the scattering diagrams as ``quark Born diagrams``. For the cases chosen to isolate this mechanism, I=2 {pi}{pi} and I=3/2 K{pi}, the theoretical results are in remarkably good agreement with experimental S- and P-wave phase shifts and PCAC scattering lengths, given standard potential-model parameters.
Barnes, T. Tennessee Univ., Knoxville, TN . Dept. of Physics)
1992-01-01
In this talk I summarize recent calculations of meson-meson scattering amplitudes in the nonrelativistic quark potential model, which assume that the scattering mechanism is one-gluon-exchange followed by constituent exchange (OGE+CEX). We refer to the scattering diagrams as quark Born diagrams''. For the cases chosen to isolate this mechanism, I=2 [pi][pi] and I=3/2 K[pi], the theoretical results are in remarkably good agreement with experimental S- and P-wave phase shifts and PCAC scattering lengths, given standard potential-model parameters.
Automorphism groups of composition algebras and quark models
Bjerregard, P.A.; Gonzalez, C.M.
1996-12-01
In this the authors study the automorphisms and derivations of real composition algebras with a view to its physical interpretations. They obtain canonical forms with a special stress in the four and eight dimensional cases. Also, using this description, they work with two mathematical models which describe some particles with certain observables in a surprising way. A first model, split g{sub 2}, describes two observables for three quarks, their antiquarks, and eight mesons combining the quarks involved. A second one, so(4,4) {circle_plus} so(2,2), describes all the observables for all quarks (u, d, s, c, b and t).
Nonequilibrium hadronization and constituent quark number scaling
Zschocke, Sven; Horvat, Szabolcs; Mishustin, Igor N.; Csernai, Laszlo P.
2011-04-15
The constituent quark number scaling of elliptic flow is studied in a nonequilibrium hadronization and freeze-out model with rapid dynamical transition from ideal, deconfined, and chirally symmetric quark-gluon plasma, to final noninteracting hadrons. In this transition a bag model of constituent quarks is considered, where the quarks gain constituent quark mass while the background bag field breaks up and vanishes. The constituent quarks then recombine into simplified hadron states, while chemical, thermal, and flow equilibrium break down one after the other. In this scenario the resulting temperatures and flow velocities of baryons and mesons are different. Using a simplified few source model of the elliptic flow, we are able to reproduce the constituent quark number scaling, with assumptions on the details of the nonequilibrium processes.
Dibaryons with two strange quarks and total spin zero in a constituent quark model
NASA Astrophysics Data System (ADS)
Park, Woosung; Park, Aaron; Lee, Su Houng
2016-04-01
We investigate the symmetry property and construct the wave function of the dibaryon states containing two strange quarks with S =0 in both the flavor SU(3) symmetric and breaking cases. We discuss how the color ⊗ isospin ⊗ spin states of dibaryon in the symmetry broken case of flavor SU(3) can be extracted from the fully antisymmetric states in flavor SU(3). The stability of the dibaryon against the strong decay into two baryons is then discussed, by using the variational method within a constituent quark model with confining and color-spin interactions. To compare our results with those from lattice QCD in the flavor SU(3) limit, we search for the stable H-dibaryon in a wide range of π meson masses. We find that with the given potential, there is no compact six-quark dibaryon state in the SU(3) flavor symmetry broken case with realistic quark masses as well as in the flavor SU(3) symmetric case in a wide range of quark masses.
Quark model study of the semileptonic B {yields} {pi} decay
Albertus, C.; Flynn, J. M.; Hernandez, E.; Verde-Velasco, J. M.; Nieves, J.
2007-02-27
The semileptonic decay B {yields} {pi}l{nu}-barl is studied starting from a simple quark model and taking into account the effect of the B* resonance. A novel, multiply subtracted, Omnes dispersion relation has been implemented to extend the predictions of the quark model to all physical q2 values. We find |Vub| = 0.0034 {+-} 0.0003(exp.) {+-} 0.0007(theory), in good agreement with experiment.
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.
Dissipative vibrational model for chiral recognition in olfaction.
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. PMID:26465515
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.
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.
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.
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.
Stable hybrid stars within a SU(3) quark-meson-model
NASA Astrophysics Data System (ADS)
Zacchi, Andreas; Hanauske, Matthias; Schaffner-Bielich, Jürgen
2016-03-01
The inner regions of the most massive compact stellar objects might be occupied by a phase of quarks. Since the observations of the massive pulsars PSR J1614-2230 and PSR J 0348 +0432 with about two solar masses, the equations of state constructing relativistic stellar models have to be constrained respecting these new limits. We discuss stable hybrid stars, i.e. compact objects with an outer layer composed of nuclear matter and with a core consisting of quark matter (QM). For the outer nuclear layer we utilize a density dependent nuclear equation of state and we use a chiral SU(3) quark-meson model with a vacuum energy pressure to describe the object's core. The appearance of a disconnected mass-radius branch emerging from the hybrid star branch implies the existence of a third family of compact stars, so-called twin stars. Twin stars did not emerge as the transition pressure has to be relatively small with a large jump in energy density, which could not be satisfied within our approach. This is, among other reasons, due to the fact that the speed of sound in QM has to be relatively high, which can be accomplished by an increase of the repulsive coupling. This increase on the other hand yields transition pressures that are too high for twins stars to appear.
Quark and pion effective couplings from polarization effects
NASA Astrophysics Data System (ADS)
Braghin, Fábio L.
2016-05-01
A flavor SU(2) effective model for pions and quarks is derived by considering polarization effects departing from the usual quark-quark effective interaction induced by dressed gluon exchange, i.e. a global color model for QCD. For that, the quark field is decomposed into a component that yields light mesons and the quark-antiquark condensate, being integrated out by means of the auxiliary field method, and another component which yields constituent quarks, which is basically a background quark field. Within a long-wavelength and weak quark field expansion (or large quark effective mass expansion) of a quark determinant, the leading terms are found up to the second order in a zero-order derivative expansion, by neglecting vector mesons that are considerably heavier than the pion. Pions are considered in the structureless limit and, besides the chiral invariant terms that reproduce previously derived expressions, symmetry breaking terms are also presented. The leading chiral quark-quark effective couplings are also found corresponding to a NJL and a vector-NJL couplings. All the resulting effective coupling constants and parameters are expressed in terms of the current and constituent quark masses and of the coupling g.
Chiral U(1) flavor models and flavored Higgs doublets: the top FB asymmetry and the W jj
Ko, P.; Omura, Yuji; Yu, Chaehyun
2012-01-01
We present U(1) flavor models for leptophobic Z' with flavor dependent couplings to the right-handed up-type quarks in the Standard Model (SM), which can accommodate the recent data on the top forward-backward (FB) asymmetry and the dijet resonance associated with a W boson reported by CDF Collaboration. Such flavor-dependent leptophobic charge assignments generally require extra chiral fermions for anomaly cancellation. Also the chiral nature of U(1)' flavor symmetry calls for new U(1)'-charged Higgs doublets in order for the SM fermions to have realistic renormalizable Yukawa couplings. The stringent constraints from the top FB asymmetry at the Tevatron and the same sign top pair production at the LHC can be evaded due to contributions of the extra Higgs doublets. We also show that the extension could realize cold dark matter candidates.
Nucleon-antinucleon annihilation in chiral soliton model
Musakhanov, M.M. . Inst. for Nuclear Theory Tashkentskij Gosudarstvennyj Univ., Tashkent . Dept. of Theoretical Physics); Musatov, I.V. . Research Inst. of Applied Physics)
1991-09-07
We investigate annihilation process of nucleons in the chiral soliton model by the path integral method. A soliton-antisoliton pair is shown to decay into mesons at range of about 1fm, defined by the S{bar S} potential. Contribution of the annihilation channel to the elastic scattering is discussed.
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)
Domain growth and ordering kinetics in dense quark matter
Singh, A.; Puri, S.; Mishra, H.
2012-06-15
The kinetics of chiral transitions in quark matter is studied in a two-flavor Nambu-Jona-Lasinio model. We focus on the phase-ordering dynamics subsequent to a temperature quench from the massless quark phase to the massive quark phase. We study the dynamics by considering a phenomenological model (Ginzburg-Landau free-energy functional). The morphology of the ordering system is characterized by the scaling of the order-parameter correlation function.
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.
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.
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.
Phenomenology of the three-flavor PNJL model and thermal strange quark production
NASA Astrophysics Data System (ADS)
Tsai, Hung-Ming; Müller, Berndt
2009-07-01
We study the temperature dependence of the adjoint Polyakov loop and its implication for the momentum spectrum of gluons in the mean-field approximation. This allows us to calculate the contribution of the thermal (transverse) gluons to the thermodynamic pressure. As an application, we evaluate the rates for the strange quark pair-production processes q\\barq \\tos\\bars and gg \\tos\\bars as functions of temperature including thermal effects on quark deconfinement and chiral symmetry breaking.
The Baryon Number Two System in the Chiral Soliton Model
NASA Astrophysics Data System (ADS)
Mantovani-Sarti, Valentina; Drago, Alessandro; Vento, Vicente; Park, Byung-Yoon
2013-03-01
We study the interaction between two B = 1 states in a chiral soliton model where baryons are described as non-topological solitons. By using the hedgehog solution for the B = 1 states we construct three possible B = 2 configurations to analyze the role of the relative orientation of the hedgehog quills in the dynamics. The strong dependence of the intersoliton interaction on these relative orientations reveals that studies of dense hadronic matter using this model should take into account their implications.
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.
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.
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.
Multiplicity fluctuations at the quark-hadron phase transition from a fluid dynamical model
NASA Astrophysics Data System (ADS)
Herold, Christoph; Nahrgang, Marlene; Yan, Yupeng; Kobdaj, Chinorat
2015-04-01
The region of large net-baryon densities in the QCD phase diagram is expected to exhibit a first-order phase transition. Experimentally, its study will be one of the primary objectives for the upcoming FAIR accelerator. We model the transition between quarks and hadrons in a heavy-ion collision using a fluid which is coupled to the explicit dynamics of the chiral order parameter and a dilaton field. This allows us to investigate signals stemming from the nonequilibrium evolution during the expansion of the hot plasma. Special emphasis is put on an event-by-event analysis of baryon number fluctuations which have long since been claimed to be sensitive to a critical point.
NN interaction from bag-model quark interchange
NASA Astrophysics Data System (ADS)
Bakker, B. L. G.; Bozoian, M.; Maslow, J. N.; Weber, H. J.
1982-03-01
A partial-wave helicity-state analysis of elastic nucleon-nuclon 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 ~350 MeV. NUCLEAR REACTIONS NN elastic scattering, Elab<=350 MeV. Coupling constants, form factors of renormalized OBE calculated from bag-model quark interchange. Phase shifts, deuteron parameters calculated from covariant partial-wave analysis.
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 .
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.
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.
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.
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.
Nucleation of quark matter in the PQM model
NASA Astrophysics Data System (ADS)
Mintz, Bruno W.; Stiele, Rainer; Ramos, Rudnei O.; Schaffner-Bielich, Jürgen
2013-03-01
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, Σ ≲ 15MeV/fm2. 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.
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.
Quark-meson coupling model with the cloudy bag
Nagai, S.; Miyatsu, T.; Saito, Kenji; Tsushima, Kazuo
2008-07-01
Using the volume coupling version of the cloudy bag model, the quark-meson coupling model is extended to study the role of pion field and the properties of nuclear matter. The extended model includes the effect of gluon exchange as well as the pion-cloud effect, and provides a good description of the nuclear matter properties. The relationship between the extended model and the EFT approach to nuclear matter is also discussed.
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.
Extended Chiral ({sigma},{pi},{omega}) Mean-Field Model with Vacuum Fluctuation Corrections
Uechi, Schun T.; Uechi, Hiroshi
2011-10-21
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}) mean-field theory. The chiral nonlinear ({sigma},{pi},{omega}) mean-field theory is an extension of the conserving nonlinear (nonchiral){sigma}-{omega} mean-field theory, which is thermodynamically consistent, relativistic and Lorentz-covariant. In the extended chiral ({sigma},{pi},{omega}) mean-field model, all the masses of hadrons are produced by the spontaneous chiral symmetry breaking, which is different from 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.
An economic subcomponent model of quarks and leptons
NASA Astrophysics Data System (ADS)
Dong, Fang-Xiao; Tu, Tung-Sheng; Xue, Pei-You
1981-04-01
The Casalbuoni-Gatto subcomponent model of quarks and leptons in generalized to extend SU(5) of Georgi and Glashow to the high rank group SU(m) to solve the family problem. It is shown that there is an unique solution with an integral number of families, viz. SU(10) × SU(3)sc.
NASA Astrophysics Data System (ADS)
Fok, R.; Kribs, Graham D.
2011-08-01
We calculate the two-body decay rates of quirkonium states formed from quirks that acquire mass solely through electroweak symmetry breaking. We consider SU(N)ic infracolor with two flavors of quirks transforming under the electroweak group (but not QCD) of the standard model. In one case, the quirks are in a chiral representation of the electroweak group, while in the other case, a vectorlike representation. The differences in the dominant decay channels between “chiral quirkonia” versus “vectorlike quirkonia” are striking. Several chiral quirkonia states can decay into the unique two-body resonance channels WH, ZH, tt¯, tb¯/bt¯, and γH, which never dominate for vectorlike quirkonia. Additionally, the channels WW, WZ, ZZ, and Wγ, are shared among both chiral and vectorlike quirkonia. Resonances of dileptons or light quarks (dijets) can dominate for some vectorlike quirkonia states throughout their mass range, while these modes never dominate for chiral quirkonia unless the decays into pairs of gauge or Higgs bosons are kinematically forbidden.
Fok, R.; Kribs, Graham D.; /Fermilab
2011-06-01
We calculate the two-body decay rates of quirkonium states formed from quirks that acquire mass solely through electroweak symmetry breaking. We consider SU(N){sub ic} infracolor with two flavors of quirks transforming under the electroweak group (but not QCD) of the standard model. In one case, the quirks are in a chiral representation of the electroweak group, while in the other case, a vectorlike representation. The differences in the dominant decay channels between 'chiral quirkonia' versus 'vectorlike quirkonia' are striking. Several chiral quirkonia states can decay into the unique two-body resonance channels WH, ZH, t{bar t}, t{bar b}/b{bar t}, and {gamma}H, which never dominate for vectorlike quirkonia. Additionally, the channels WW, WZ, ZZ, and W{gamma}, are shared among both chiral and vectorlike quirkonia. Resonances of dileptons or light quarks (dijets) can dominate for some vectorlike quirkonia states throughout their mass range, while these modes never dominate for chiral quirkonia unless the decays into pairs of gauge or Higgs bosons are kinematically forbidden.
Quark susceptibility in a generalized dynamical quasiparticle model
NASA Astrophysics Data System (ADS)
Berrehrah, H.; Cassing, W.; Bratkovskaya, E.; Steinert, Th.
2016-04-01
The quark susceptibility χq at zero and finite quark chemical potential provides a critical benchmark to determine the quark-gluon-plasma (QGP) degrees of freedom in relation to the results from lattice QCD (lQCD) in addition to the equation of state and transport coefficients. Here we extend the familiar dynamical quasiparticle model (DQPM) to partonic propagators that explicitly depend on the three-momentum with respect to the partonic medium at rest in order to match perturbative QCD (pQCD) at high momenta. Within the extended dynamical quasiparticle model (DQPM*) we reproduce simultaneously the lQCD results for the quark number density and susceptibility and the QGP pressure at zero and finite (but small) chemical potential μq. The shear viscosity η and the electric conductivity σe from the extended quasiparticle model (DQPM*) also turn out to be in close agreement with lattice results for μq=0 . The DQPM*, furthermore, allows one to evaluate the momentum p , temperature T , and chemical potential μq dependencies of the partonic degrees of freedom also for larger μq, which are mandatory for transport studies of heavy-ion collisions in the regime 5 <√{sN N}<10 GeV.
Two potential quark models for double heavy baryons
NASA Astrophysics Data System (ADS)
Puchkov, A. M.; Kozhedub, A. V.
2016-01-01
Baryons containing two heavy quarks (QQ' q) are treated in the Born-Oppenheimer approximation. Two non-relativistic potential models are proposed, in which the Schrödinger equation admits a separation of variables in prolate and oblate spheroidal coordinates, respectively. In the first model, the potential is equal to the sum of Coulomb potentials of the two heavy quarks, separated from each other by a distance - R and linear potential of confinement. In the second model the center distance parameter R is assumed to be purely imaginary. In this case, the potential is defined by the two-sheeted mapping with singularities being concentrated on a circle rather than at separate points. Thus, in the first model diquark appears as a segment, and in the second - as a circle. In this paper we calculate the mass spectrum of double heavy baryons in both models, and compare it with previous results.
Quark and gluon decay functions in QCD and recombination model
Change, V.; Hwa, R.C.
1980-04-01
Inclusive longitudinal-momentum distributions of pions in jets initiated by quarks and gluons are determined in perturbative QCD and recombination model. The quark and antiquark joint distributions in jets are first calculated in the leading-order approximation at high Q/sup 2/. Gluons in the jets are completely converted to quark pairs. From the overall distribution q anti q pairs with definite quantum numbers then recombine to form pions. The recombination function for the process is well determined in the valon model. No adjustable parameters are involved in these calculations, and no data at low Q/sup 2/ are used as phenomenological input. The result for the quark decay functions can be compared with data on e/sup +/e/sup -/ annihilation, and the agreement is very good in both shape and normalization. Predictions for the gluon decay functions are presented, but they cannot yet be checked by experiments. The x and Q/sup 2/ dependences of both types of decay functions have been parametrized in simple form suitable for use in theoretical and experimental applications. 17 figures, 1 table.
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.
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.
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.
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.
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.
A composite supersymmetric model of quarks and leptons
NASA Astrophysics Data System (ADS)
Barbieri, R.
1983-01-01
A supersymmetric model is presented in which quarks and leptons (and perhaps weak vector bosons) are composite of fermions and scalars. It may be considered as the supersymmetric extension of a model previously discussed (by Barbieri, Mohapatra and Masiero, and Casalbuoni and Gatto), based on the weak group SU(2) L × SU(2) R × U(1). A speculative interpretation of the families emerges.
Decay constants of pseudoscalar mesons in a relativistic quark model
Micu, L.
1997-04-01
The decay constants of pseudoscalar mesons are calculated in a relativistic quark model which assumes that mesons are made of a valence quark-antiquark pair and of an effective vacuumlike component. The results are given as functions of quark masses and of some free parameters entering the expression of the internal wave functions of the mesons. Using F{sub {pi}{sup +}}=130.7 MeV, F{sub K{sup +}}=159.8 MeV to fix the parameters of the model, we predict 60MeV{le}F{sub D{sup +}}{le}185 MeV, 95MeV{le}F{sub D{sub s}}{le}230 MeV, 80MeV{le}F{sub B{sup +}}{le}205 MeV, 90MeV{le}F{sub B{sub s}}{le}235 MeV for the light quark masses m{sub u}=5.1 MeV, m{sub d}=9.3 MeV, m{sub s}=175 MeV and the heavy quark masses in the range 1GeV{le}m{sub c}{le}1.6 GeV, 4.1GeV{le}m{sub b}{le}4.5 GeV. In the case of light neutral mesons one obtains with the same set of parameters F{sub {pi}{sup 0}}{approx}138 MeV, F{sub {eta}}{approx}130 MeV, F{sub {eta}{sup {prime}}}{approx}78 MeV. The values are in agreement with the experimental data and other theoretical results. {copyright} {ital 1997} {ital The American Physical Society}
Quark-gluon plasma (Selected Topics)
Zakharov, V. I.
2012-09-15
Introductory lectures to the theory of (strongly interacting) quark-gluon plasma given at the Winter School of Physics of ITEP (Moscow, February 2010). We emphasize theoretical issues highlighted by the discovery of the low viscosity of the plasma. The topics include relativistic hydrodynamics, manifestations of chiral anomaly in hydrodynamics, superfluidity, relativistic superfluid hydrodynamics, effective stringy scalars, holographic models of Yang-Mills theories.
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.
Chiral Spin Liquid in a Frustrated Anisotropic Kagome Heisenberg Model
NASA Astrophysics Data System (ADS)
He, Yin-Chen; Sheng, D. N.; Chen, Yan
2014-04-01
Kalmeyer-Laughlin (KL) chiral spin liquid (CSL) is a type of quantum spin liquid without time-reversal symmetry, and it is considered as the parent state of an exotic type of superconductor—anyon superconductor. Such an exotic state has been sought for more than twenty years; however, it remains unclear whether it can exist in a realistic system where time-reversal symmetry is breaking (T breaking) spontaneously. By using the density matrix renormalization group, we show that KL CSL exists in a frustrated anisotropic kagome Heisenberg model, which has spontaneous T breaking. We find that our model has two topological degenerate ground states, which exhibit nonvanishing scalar chirality order and are protected by finite excitation gap. Furthermore, we identify this state as KL CSL by the characteristic edge conformal field theory from the entanglement spectrum and the quasiparticles braiding statistics extracted from the modular matrix. We also study how this CSL phase evolves as the system approaches the nearest-neighbor kagome Heisenberg model.
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.
Spin Structure Functions in a Covariant Spectator Quark Model
G. Ramalho, Franz Gross and M. T. Peña
2010-12-01
We apply the covariant spectator quark–diquark model, already probed in the description of the nucleon elastic form factors, to the calculation of the deep inelastic scattering (DIS) spin-independent and spin-dependent structure functions of the nucleon. The nucleon wave function is given by a combination of quark–diquark orbital states, corresponding to S, D and P-waves. A simple form for the quark distribution function associated to the P and D waves is tested.
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 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.
Quark-gluon vertex model and lattice-QCD data
Bhagwat, M.S.; Tandy, P.C.
2004-11-01
A model for the dressed-quark-gluon vertex, at zero gluon momentum, is formed from a nonperturbative extension of the two Feynman diagrams that contribute at one loop in perturbation theory. The required input is an existing ladder-rainbow model Bethe-Salpeter kernel from an approach based on the Dyson-Schwinger equations; no new parameters are introduced. The model includes an Ansatz for the triple-gluon vertex. Two of the three vertex amplitudes from the model provide a pointwise description of the recent quenched-lattice-QCD data. An estimate of the effects of quenching is made.
Lattice Schwinger model: Confinement, anomalies, chiral fermions, and all that
Melnikov, Kirill; Weinstein, Marvin
2000-11-01
In order to better understand what to expect from numerical CORE computations for two-dimensional massless QED (the Schwinger model) we wish to obtain some analytic control over the approach to the continuum limit for various choices of fermion derivative. To this end we study the Hamiltonian formulation of the lattice Schwinger model (i.e., the theory defined on the spatial lattice with continuous time) in A{sub 0}=0 gauge. We begin with a discussion of the solution of the Hamilton equations of motion in the continuum; we then parallel the derivation of the continuum solution within the lattice framework for a range of fermion derivatives. The equations of motion for the Fourier transform of the lattice charge density operator show explicitly why it is a regulated version of this operator which corresponds to the point-split operator of the continuum theory and the sense in which the regulated lattice operator can be treated as a Bose field. The same formulas explicitly exhibit operators whose matrix elements measure the lack of approach to the continuum physics. We show that both chirality violating Wilson-type and chirality preserving SLAC-type derivatives correctly reproduce the continuum theory and show that there is a clear connection between the strong and weak coupling limits of a theory based upon a generalized SLAC-type derivative.
Two flavor superconductivity in non-local models
Duhau, R.; Grunfeld, A.G.; Scoccola, N.N.
2004-12-02
In the present work we study a relativistic quark model at finite temperature and density with non-local quark-antiquark and quark-quark interactions with SU(2) flavour and SU(3) color symmetries. After proper bosonization, we analyze the structure of the corresponding phase diagram and discuss the competition between the chiral and 2SC phases.
Models of quark-hadron matter and compact stars
NASA Astrophysics Data System (ADS)
Schramm, S.; Dexheimer, V.; Negreiros, R.; Steinheimer, J.
2016-01-01
Phenomenological approaches to Quantum Chromodynamics covering the whole region of low and high temperatures and/or densities must address the problem that the effective degrees of freedom change from hadrons to quarks and gluons. We approach this task with a unified description of hadronic and quark matter allowing for cross-over as well as first or second-order phase transitions. As a further benefit of such an approach, a quantitatively satisfactory description of nuclear ground state matter as well as nuclear and hypernuclear properties can be achieved. We apply this model to neutron stars and consider potential constraints on star properties arising from lattice gauge results in relation with the observation of 2 solar mass stars.
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
Nontopological soliton in the Polyakov quark-meson model
NASA Astrophysics Data System (ADS)
Jin, Jinshuang; Mao, Hong
2016-01-01
Within a mean-field approximation, we study a nontopological soliton solution of the Polyakov quark-meson model in the presence of a fermionic vacuum term with two flavors at finite temperature and density. The profile of the effective potential exhibits a stable soliton solution below a critical temperature T ≤Tχc for both the crossover and the first-order phase transitions, and these solutions are calculated here with appropriate boundary conditions. However, it is found that only if T ≤Tdc is the energy of the soliton MN less than the energy of the three free constituent quarks 3 Mq . As T >Tdc , there is an instant delocalization phase transition from hadron matter to quark matter. The phase diagram together with the location of a critical end point has been obtained in the T and μ plane. We notice that two critical temperatures always satisfy Tdc≤Tχc . Finally, we present and compare the result of thermodynamic pressure at zero chemical potential with lattice data.
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.
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.
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.
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.
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.
Top Quark Phenomenology in CP-Violating Supersymmetric Models
NASA Astrophysics Data System (ADS)
Moreno Briceno, Alexander
The Standard Model (SM) of particle physics so far has successfully described all measurements of phenomena at the subatomic level of ordinary matter at very high precision. The theoretical developments and experimental observations during the last 50 years, including the long sought and recently observed SM Higgs-like boson at the Large Hadron Collider (LHC), have provided us with a framework to understand the strong and the electroweak interactions between fermions, gauge bosons and the scalar boson, the Higgs boson, which is called the SM. However, the SM is considered to be incomplete. It does not provide a framework to include gravity and it does not provide an explanation for a number of observations such as the baryon asymmetry of the Universe (BAU), neutrino oscillations and dark matter. One possible extension of the SM is Supersymmetry, which provides for instance a dark matter candidate. No direct or indirect evidence of Supersymmetry has been observed so far. Searches for supersymmetric particles at high energy collider experiments, for instance, have set limits on parameters of the minimal supersymmetric extension of the SM (MSSM). Supersymmetry may also affect the properties of SM particles through their virtual presence in higher order corrections in perturbation theory. Here we study indirect, i.e. virtual effects, of Supersymmetry in the production of top quark pairs at the LHC. In particular, we investigate possible CP violating effects due to one loop corrections to top-quark pair production at the Large Hadron Collider (LHC) in the context of the complex (MSSM) with minimal flavor violation (MFV). We include the complete supersymmetric QCD as well as supersymmetric electroweak contributions to the two main top-quark pair production mechanisms at the LHC, namely quark-antiquark annihilation, qq → tt, and gluon fusion, gg → tt. At the level of the top quarks, we study in detail spin-spin correlating observables that are sensitive to CP
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.
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.
Constituent-quark model for production of forward hyperons in proton-nucleus collisions
Takagi, F.
1983-04-01
Cross sections for the inclusive reactions p+A..--> lambda.. or ..xi../sup 0/+anything in the proton fragmentation region are analyzed in terms of the constituent-quark model. Contributions from the leading single quarks and leading diquarks are determined separately and the results are interpreted in terms of the quark-fragmentation-recombination picture. It is strongly suggested that recombination of leading quarks with a heavy (anti)quark (s,s-bar,c,c-bar, . . .) or a pair of (anti)quarks from the central sea is strongly suppressed compared to recombination with a single light (anti)quark (u, u-bar, d, or d-bar) from the sea.
Parton distribution in pseudoscalar mesons with a light-front constituent quark model
NASA Astrophysics Data System (ADS)
de Melo, J. P. B. C.; Ahmed, Isthiaq; Tsushima, Kazuo
2016-05-01
We compute the distribution amplitudes of the pion and kaon in the light-front constituent quark model with the symmetric quark-bound state vertex function [1, 2, 3]. In the calculation we explicitly include the flavor-SU(3) symmetry breaking effect in terms of the constituent quark masses of the up (down) and strange quarks. To calculate the kaon parton distribution functions (PDFs), we use both the conditions in the light-cone wave function, i.e., when s ¯ quark is on-shell, and when u quark is on-shell, and make a comparison between them. The kaon PDFs calculated in the two different conditions clearly show asymmetric behaviour due to the flavor SU(3)-symmetry breaking implemented by the quark masses [4, 5].
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.
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.
Hypernuclei in the quark-meson coupling model
K. Tsushima, P. A. M. Guichon
2010-07-01
We present results of hypernuclei calculated in the latest quark-meson coupling (QMC) model, where the effect of the mean scalar field in-medium on the one-gluon exchange hyperfine interaction, is also included self-consistently. The extra repulsion associated with this increased hyperfine interaction in-medium completely changes the predictions for {\\Sigma} hypernuclei. Whereas in the earlier version of QMC they were bound by an amount similar to {\\Lambda} hypernuclei, they are unbound in the latest version of QMC, in qualitative agreement with the experimental absence of such states.
Proper time regularization at finite quark chemical potential
NASA Astrophysics Data System (ADS)
Zhang, Jin-Li; Shi, Yuan-Mei; Xu, Shu-Sheng; Zong, Hong-Shi
2016-04-01
In this paper, we use the two-flavor Nambu-Jona-Lasinio (NJL) model to study the quantum chromodynamics (QCD) chiral phase transition. To deal with the ultraviolet (UV) issue, we adopt the popular proper time regularization (PTR), which is commonly used not only for hadron physics but also for the studies with magnetic fields. This regularization scheme can introduce the infrared (IR) cutoff to include quark confinement. We generalize the PTR to zero temperature and finite chemical potential case use a completely new method, and then study the chiral susceptibility, both in the chiral limit case and with finite current quark mass. The chiral phase transition is second-order in μ = 0 and T = 0 and crossover at μ≠0 and T = 0. Three sets of parameters are used to make sure that the results do not depend on the parameter choice.
Chiral density wave in nuclear matter
NASA Astrophysics Data System (ADS)
Heinz, Achim; Giacosa, Francesco; Rischke, Dirk H.
2015-01-01
Inspired by recent work on inhomogeneous chiral condensation in cold, dense quark matter within models featuring quark degrees of freedom, we investigate the chiral density-wave solution in nuclear matter at zero temperature and nonvanishing baryon number density in the framework of the so-called extended linear sigma model (eLSM). The eLSM is an effective model for the strong interaction based on the global chiral symmetry of quantum chromodynamics (QCD). It contains scalar, pseudoscalar, vector, and axial-vector mesons as well as baryons. In the latter sector, the nucleon and its chiral partner are introduced as parity doublets in the mirror assignment. The eLSM simultaneously provides a good description of hadrons in vacuum as well as nuclear matter ground-state properties. We find that an inhomogeneous phase in the form of a chiral density wave is realized, but only for densities larger than 2.4ρ0, where ρ0 is the nuclear matter ground-state density.
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.
Particle production within the quark meson coupling model
Panda, P. K.; Menezes, D. P.; Providencia, C.
2009-07-15
Quark-meson coupling (QMC) models can be successfully applied to the description of compact star properties in nuclear astrophysics as well as to nuclear matter. In the regime of hot hadronic matter very few calculations exist using the QMC model, in particular when applied to particle yields in heavy ion collisions. In the present work, we identify the free energy of the bag with the effective mass of the baryons and we calculate the particle production yields on a Au+Au collision at the BNL Relativistic Heavy Ion Collider (RHIC) with the QMC model and compare them with results obtained previously with other relativistic models. A smaller temperature for the fireball, T=132 MeV, is obtained because of the smaller effective baryon masses predicted by QMC. QMC was also applied to the description of particle yields at the CERN Super Proton Synchrotron (SPS) in Pb+Pb collisions.
Finite Nuclei in the Quark-Meson Coupling Model
NASA Astrophysics Data System (ADS)
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
Charm quark energy loss in infinite QCD matter using a parton cascade model
NASA Astrophysics Data System (ADS)
Younus, Mohammed; Coleman-Smith, Christopher E.; Bass, Steffen A.; Srivastava, Dinesh K.
2015-02-01
We utilize the parton cascade model to study the evolution of charm quarks propagating through a thermal brick of QCD matter. We determine the energy loss and the transport coefficient q ̂ for charm quarks. The calculations are done at a constant temperature of 350 MeV and the results are compared to analytical calculations of heavy-quark energy loss in order to validate the applicability of using a parton cascade model for the study of heavy-quark dynamics in hot and dense QCD matter.
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.
Inhomogeneous condensates in the thermodynamics of the chiral NJL{sub 2} model
Basar, Goekce; Dunne, Gerald V.; Thies, Michael
2009-05-15
We analyze the thermodynamical properties, at finite density and nonzero temperature, of the (1+1) dimensional chiral Gross-Neveu model (the NJL{sub 2} model), using the exact inhomogeneous (crystalline) condensate solutions to the gap equation. The continuous chiral symmetry of the model plays a crucial role, and the thermodynamics leads to a broken phase with a periodic spiral condensate, the ''chiral spiral,'' as a thermodynamically preferred limit of the more general ''twisted kink crystal'' solution of the gap equation. This situation should be contrasted with the Gross-Neveu model, which has a discrete chiral symmetry, and for which the phase diagram has a crystalline phase with a periodic kink crystal. We use a combination of analytic, numerical, and Ginzburg-Landau techniques to study various parts of the phase diagram.
Quark matter in an SU(3) Nambu-Jona-Lasinio model with two types of vector interactions
NASA Astrophysics Data System (ADS)
Chu, Peng-Cheng; Wang, Bin; Ma, Hong-Yang; Dong, Yu-Min; Chang, Su-Ling; Zheng, Chun-Hong; Liu, Jun-Ting; Zhang, Xiao-Min
2016-05-01
We investigate the properties of asymmetric quark matter and strange quark matter in the framework of the SU(3) Nambu-Jona-Lasinio (NJL) model with two types of vector interactions: (1) the flavor-dependent repulsion among different flavors of quarks with the coupling constant GV , and (2) the universal repulsion and the vector-isovector interaction among different flavors of quarks with the coupling constants gV and GI V. Using these two types of vector interactions in the NJL model, we study the quark symmetry energy in asymmetric quark matter, the constituent quark mass, the quark fraction, the equation of state in strange quark matter, the maximum mass of a quark star, and the properties of the QCD phase diagram. We find that including the two types of vector interactions in the SU(3) NJL model can significantly influence the quark matter symmetry energy as well as the properties of strange quark matter and quark stars. In particular, our results indicate that we can describe PSR J 1614 -2230 and PSR J 0348 +0432 as quark stars by considering the universal repulsion and the vector-isovector interaction among quark matter in the SU(3) NJL model.
Orthosymplectic Chern-Simons matrix model and chirality projection
NASA Astrophysics Data System (ADS)
Moriyama, Sanefumi; Suyama, Takao
2016-04-01
Recently it was found that the density matrix for a certain orthosymplectic Chern-Simons theory matches with that for the ABJM theory with the odd chiral projection. We prove this fact for a general case with the inclusion of fractional branes. We also identify the first few diagonal Gopakumar-Vafa invariants for the grand potential constructed from the chirally projected density matrix. [Figure not available: see fulltext.
Exclusive versus inclusive semileptonic {anti B} decays in the quark model
Nathan Isgur
1996-10-01
Some emerging difficulties in the theoretical description of exclusive semileptonic {anti B} decays are discussed in the context of the quark model. While there are no unambiguous problems at this time, the author discusses physics beyond the valence quark model which should eventually be probed by precision measurements of B semileptonic decays.
Chiral magnetic effect in the soft-wall AdS/QCD model
Gorsky, A.; Kopnin, P. N.; Zayakin, A. V.
2011-01-01
The essence of the chiral magnetic effect is generation of an electric current along an external magnetic field. Recently it has been studied by Rebhan, Schmitt, and Stricker within the Sakai-Sugimoto model, where it was shown to be zero. As an alternative, we calculate the chiral magnetic effect in soft-wall AdS/QCD and find a nonzero result with the natural boundary conditions. The mechanism of the dynamical neutralization of the chiral chemical potential via the string production is discussed in the dual two-form representation.
Chiral supersymmetric Standard Model spectra from orientifolds of Gepner models [rapid communication
NASA Astrophysics Data System (ADS)
Dijkstra, T. P. T.; Huiszoon, L. R.; Schellekens, A. N.
2005-03-01
We construct d = 4, N = 1 orientifolds of Gepner models with just the chiral spectrum of the Standard Model. We consider all simple current modular invariants of c = 9 tensor products of N = 2 minimal models. For some very specific tensor combinations, and very specific modular invariants and orientifold projections, we find a large number of such spectra. We allow for Standard Model singlet (dark) matter and non-chiral exotics. The Chan-Paton gauge group is either U (3) × Sp (2) × U (1) × U (1) or U (3) × U (2) × U (1) × U (1). In many cases the Standard Model hypercharge U (1) has no coupling to RR 2-forms and hence remains massless; in some of those models the B-L gauge boson does acquire a mass.
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.
Chiral symmetry of heavy-light scalar mesons with UA(1) symmetry breaking
NASA Astrophysics Data System (ADS)
Dmitrašinović, V.
2012-07-01
In a previous paper, based on a calculation in the nonrelativistic quark model, we advanced the hypothesis that the Ds(2317), D0(2308) mesons are predominantly four-quark states lowered in mass by the flavor-dependent Kobayashi-Kubo-Maskawa ’t Hooft UA(1) symmetry breaking effective interaction. Here we show similar results and conclusions in a relativistic effective chiral model calculation, based on three-light-quark (i.e., two q plus one q¯) local interpolators. To this end we classify the four-quark (three light plus one heavy quark) local interpolators according to their chiral transformation properties and then construct chiral invariant interactions. We evaluate the diagonal matrix elements of the Kobayashi-Kubo-Maskawa ’t Hooft interaction between different interpolating fields and show that the lowest-lying one is always the (antisymmetric) SU(3)F antitriplet belonging to the chiral (3, 3) multiplet. We predict bottom-strange Bs0 and the bottom-nonstrange B0 scalar mesons with equal masses at 5720 MeV, the strange meson being some 100 MeV lower than in most of the quark potential models. We also predict the JP=1+ bottom-nonstrange B1 and the bottom-strange Bs1 meson masses as 5732 MeV and 5765 MeV, respectively, using the Bardeen-Hill-Nowak-Rho-Zahed scalar-vector mass relation.
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.
Baryon spectroscopy in a three-quark model
NASA Astrophysics Data System (ADS)
Aslanzadeh, M.; Rajabi, A. A.
2016-04-01
In this paper, we present a three-body quark model for investigating the internal structure of baryons as well as baryon spectroscopy. In order to describe the SU(6) -invariant part of the spectrum, we assumed the spin-independent part of the interaction hypercentral, and treated using the hyperspherical formalism. For SU(6) -invariant potential, we used a generalized version of the popular "Coulomb-plus-linear" potential which contains "linear-plus-logarithmic" terms as confinement part and some inverse power terms. To obtain an analytical solution, we applied some approximations for dealing with problematic linear and logarithmic terms, leading to a qualitative reproducing of the spectrum. Then, to describe the hyperfine structure of the baryon and the splittings within the SU(6) -multiplets, we used the generalized Gürsey-Radicati Mass Formula as a SU(6) breaking interaction. Our calculations lead to a generally fair description of the baryon spectrum.
Finite Hypernuclei in the Latest Quark-Meson Coupling Model
Pierre A. M. Guichon; Anthony W. Thomas; Kazuo Tsushima
2007-12-12
The most recent development of the quark-meson coupling (QMC) model, in which the effect of the mean scalar field in-medium on the hyperfine interaction is also included self-consistently, is used to compute the properties of finite hypernuclei. The calculations for $\\Lambda$ and $\\Xi$ hypernuclei are of comparable quality to earlier QMC results without the additional parameter needed there. Even more significantly, the additional repulsion associated with the increased hyperfine interaction in-medium completely changes the predictions for $\\Sigma$ hypernuclei. Whereas in the earlier work they were bound by an amount similar to $\\Lambda$ hypernuclei, here they are unbound, in qualitative agreement with the experimental absence of such states. The equivalent non-relativistic potential felt by the $\\Sigma$ is repulsive inside the nuclear interior and weakly attractive in the nuclear surface, as suggested by the analysis of $\\Sigma$-atoms.
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.
TMDs and Azimuthal Spin Asymmetries in a Light-Cone Quark Model
Pasquini, B.; Boffi, S.; Efremov, A. V.; Schweitzer, P.
2009-08-04
The main properties of the leading-twist transverse momentum dependent parton distributions in a light-cone constituent quark model of the nucleon are reviewed, with focus on the role of the spin-spin and spin-orbit correlations of quarks. Results for azimuthal single spin asymmetries in semi-inclusive deep inelastic scattering are also discussed.
Numerical modelling of chirality-induced bi-directional swimming of artificial flagella.
Namdeo, S; Khaderi, S N; Onck, P R
2014-02-01
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.
Akamatsu, Yukinao; Yamamoto, Naoki
2013-08-01
We study the collective modes in relativistic electromagnetic or quark-gluon plasmas with an asymmetry between left- and right-handed chiral fermions, based on the recently formulated kinetic theory with Berry curvature corrections. We find that there exists an unstable mode, signaling the presence of a plasma instability. We argue the fate of this "chiral plasma instability" including the effect of collisions, and briefly discuss its relevance in heavy ion collisions and compact stars. PMID:23952387
Gershun, V. D.
2010-02-15
We used the invariant local chiral currents of principal chiral models for SU(n), SO(n), SP(n) groups to construct new integrable string equations of hydrodynamic type on the Riemann space of the chiral primitive invariant currents and on the chiral nonprimitive Casimir operators as Hamiltonians.
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
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.
The chiral phase transition and the role of vacuum fluctuations
NASA Astrophysics Data System (ADS)
Khan, Rashid; Andersen, Jens O.; Kyllingstad, Lars T.; Khan, Majid
2016-03-01
We apply optimized perturbation theory to the quark-meson model at finite temperature T and quark chemical potential μ. The effective potential is calculated to one loop both in the chiral limit and at the physical point and used to study the chiral dynamics of two-flavor QCD. The critical temperature and the order of the phase transition depend heavily on whether or not one includes the bosonic and fermionic vacuum fluctuations in the effective potential. A full one-loop calculation in the chiral limit predicts a first-order transition for all values of μ. At the physical point, one finds a crossover in the whole μ-T plane.
Dual quark condensate in the Polyakov-loop extended Nambu-Jona-Lasinio model
Kashiwa, Kouji; Yahiro, Masanobu; Kouno, Hiroaki
2009-12-01
The dual quark condensate {sigma}{sup (n)} proposed recently as a new order parameter of the spontaneous breaking of the Z{sub 3} symmetry are evaluated by the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model, where n are winding numbers. The Polyakov-loop extended Nambu-Jona-Lasinio model well reproduces lattice QCD data on {sigma}{sup (1)} measured very lately. The dual quark condensate {sigma}{sup (n)} at higher temperatures is sensitive to the strength of the vector-type four-quark interaction in the Polyakov-loop extended Nambu-Jona-Lasinio model and hence a good quantity to determine the strength.
The Top Quark as a Window to Beyond the Standard Model Physics
NASA Astrophysics Data System (ADS)
Yu, Chiu-Tien
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) x SU(2) x SU'(2) with couplings g' 1,g'2; and g' associated with the fields B',W,W', respectively, and show how this model can explain the top forwardbackward 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 chargeconjugation. 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.
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.