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Impact of Vector-Current Interactions on the qcd phase diagram

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Journal of Modern Physics 2013年第5期4卷 644-650页

作者： Thomas Hell Kouji Kashiwa Wolfram Weise Physik Department Technische Universitat MünchenGarchingGermany ECT* Strada delle Tabarelle 286VillazzanoTrentoItaly RIKEN/BNL Research Center Brookhaven National LaboratoryUptonUSA

Using a nonlocal version of the Polyakov-loop-extended Nambu-Jona-Lasinio model, we investigate effects of a nonderivative vector-current interaction (relating to the quark-number density) at both real and imaginary chemical potentials. This repulsive vector interaction between quarks has the following impact on the chiral first-order phase transition: at imaginary chemical potential it sharpens the transition at the Roberge-Weiss (RW) end point and moves this critical point toward lower temperatures;at real chemical potential, the critical end point moves on a trajectory towards larger chemical potentials and lower temperatures with increasing vector coupling strength. The conditions are discussed at which the first-order phase transition disappears and turns into a smooth crossover.

关键词： qcd phase diagram PNJL Model

Nonextensive effects on qcd chiral phase diagram and baryon-number fluctuations within Polyakov-Nambu-Jona-Lasinio model

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Chinese Physics C 2023年第5期47卷 66-72页

作者：赵亚鹏王朝勇左淑毓李程明 School of Mathematics and Physics Henan University of Urban ConstructionPingdingshan 467036China Henan Provincial Engineering Laboratory of Building-Photovoltaics Pingdingshan 467036China College of Science Henan University of TechnologyZhengzhou 450000China School of Physics and Microelectronics Zhengzhou UniversityZhengzhou 450001China

In this paper,a version of the Polyakov-Nambu-Jona-Lasinio(PNJL)model based on nonextensive statistical mechanics is *** new statistics summarizes all possible factors that violate the assumptions of the Boltzmann-Gibbs(BG)statistics to a dimensionless nonextensivity parameter ***,when q tends to 1,it returns to the BG *** the nonextensive PNJL model,we found that as q increases,the location of the critical end point(CEP)exhibits non-monotonic *** is,for q1.15,CEP turns to move in the direction of lower temperature and lower quark chemical *** addition,we studied the moments of the net-baryon number distribution,that is,variance(σ^(2)),skewness(S),and kurtosis(k).Our results are generally consistent with the latest experimental data reported,especially for√SNN>19.6 GeV,when q is set to 1.07.

关键词： nonextensive statistics Polyakov-Nambu-Jona-Lasinio model qcd phase diagram baryonnumber fluctuations

Thermodynamic properties and phase diagram of quark matter within non-extensive Polyakov chiral SU(3)quark mean field model

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Chinese Physics C 2024年第5期48卷 60-71页

作者： Dhananjay Singh Arvind Kumar Department of Physics Dr.B R Ambedkar National Institute of Technology JalandharJalandhar–144008PunjabIndia

In the present study,we applied Tsallis non-extensive statistics to investigate the thermodynamic properties and phase diagram of quark matter in the Polyakov chiral SU(3)quark mean field *** this model,the properties of the quark matter were modified through the scalar fieldsσ,ζ,δ,χ,vector fieldsω,ρ,ϕ,and Polyakov fieldsΦandΦ¯at finite temperature and chemical ***-extensive effects were introduced through a dimensionless parameter q,and the results were compared to those of the extensive case(q→1).In the non-extensive case,the exponential in the Fermi-Dirac(FD)function was modified to a q-exponential *** influence of the q parameter on the thermodynamic properties,pressure,energy,and entropy density,as well as trace anomaly,was *** speed of sound and specific heat with non-extensive effects were also ***,the effect of non-extensivity on the deconfinement phase transition as well as the chiral phase transition of u,d,and s quarks was *** found that the critical end point(CEP),which defines the point in the(T−μ)phase diagram where the order of the phase transition changes,shifts to a lower value of temperature,TCEP,and a higher value of chemical potential,μCEP,as the non-extensivity is increased,that is,q>1.

关键词： quark matter quark mean field model qcd phase diagram non-extensive statistics

Anisotropic flow in high baryon density region

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Nuclear Science and Techniques 2022年第2期33卷 79-86页

作者： Shao-Wei Lan Shu-Su Shi Key Laboratory of Quark and Lepton Physics(MOE)and Institute of Particle Physics Central China Normal UniversityWuhan 430079China

Collective flow is a powerful tool used to analyze the properties of a medium created during high-energy nuclear ***,we report a systematic study of the first two Fourier coefficients v_(1)and v_(2)of the proton andπ^(+)from Au+Au collisions in the energy range√sNN=2.11-4.9 GeV within the framework of a hadronic transport model(UrQMD).Recent results from the STAR experiment were used to test the model calculations.A meanfield mode with strong repulsive interaction is needed to reproduce the 10-40%data at 3 *** implies that hadronic interactions play an important role in the collective flow development in the high baryon density *** mean values of the freeze-out time for protons andπ^(+)are shifted earlier owing to the additional repulsive *** predict the energy dependence of the mean values of the transverse momentum,v_(1),and v_(2)for both protons andπ^(+)from the Au+Au collisions.

关键词： Heavy-ion collisions qcd phase diagram UrQMD Collective flow Mean-field potential

Effect of non-uniform efficiency on higher-order cumulants in heavy-ion collisions

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Chinese Physics C 2021年第12期45卷 62-79页

作者： Fan Si Yifei Zhang Xiaofeng Luo State Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China Key Laboratory of Quark&Lepton Physics(MOE)and Institute of Particle Physics Central China Normal UniversityWuhan 430079China

We perform a systematic study on the effect of non-uniform track efficiency correction in higher-order cumulant analysis in heavy-ion *** analytical derivation,we find that the true values of cumulants can be successfully reproduced by the efficiency correction with an average of the realistic detector efficiency for particles with the same charges within each single phase *** theoretical conclusions are supported by a toy model simulation by tuning the non-uniformity of the efficiency employed in the track-by-track efficiency correction *** valid averaged efficiency is found to suppress the statistical uncertainties of the reproduced cumulants ***,usage of the averaged efficiency requires a careful study of phase space *** study is important for carrying out precision measurements of higher-order cumulants in heavy-ion collision experiments at present and in future.

关键词： heavy ion collisions qcd phase diagram higher-order cumulants net-proton fluctuation Beam Energy Scan at RHIC

Nonextensive effects on qcd chiral phase transition with a chiral chemical potential

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Chinese Physics C 2022年第10期46卷 98-106页

作者： Ya-Peng Zhao Shu-Yu Zuo Cheng-Ming Li School of Mathematics and Physics Henan Urban Construction UniversityPingdingshan 467036China College of Science Henan University of TechnologyZhengzhou 450000China School of Physics and Microelectronics Zhengzhou UniversityZhengzhou 450001China

In this study,we investigate the qcd chiral phase diagram in the presence of a chiral chemical potential μ based on nonextensive statistical mechanics.A feature of this new statistic is a dimensionless nonextensivity parameter q,which summarizes all possible effects violating the assumptions of Boltzmann-Gibbs(BG)statistics(when q→1,it returns to the BG case).Within the nonextensive Polyakov-Nambu-Jona-Lasinio model,we find that as μ increases,the critical end point(CEP)in the T-μ plane continues to CEP_(5)in the T-μ plane,and nonextensive effects have a significant impact on the evolution from the CEP to CEP_(5).Generally,with an increase in q,both the CEP and CEP_(5)move in the direction of a lower temperature T and larger chemical potentialμ(μ_(5)).In addition,we find that chiral charge density ngenerally increases with T,μ,μ_(5),and *** study may provide useful hints about lattice qcd and relativistic heavy-ion collision experiments.

关键词： nonextensive statistics Polyakov-Nambu-Jona-Lasinio model qcd phase diagram chiral chemical potential

Search for qcd critical point by transverse velocity dependence of anti-deuteron to deuteron ratio

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Chinese Physics C 2020年第1期44卷 53-57页

作者： Ning Yu Dingwei Zhang Xiaofeng Luo School of Physics&Electronic Engineering Xinyang Normal UniversityXinyang 464000China Key Laboratory of Quark&Lepton Physics(MOE)and Institute of Particle Physics Central China Normal UniversityWuhan 430079China

We propose the transverse velocity(β_T) dependence of the anti-deuteron to deuteron ratio as a new observable to search for the qcd critical point in heavy-ion *** qcd critical point can attract the system evolution trajectory in the qcd phase diagram,which is known as the focusing *** quantify this effect,we employ the thermal and hadronic transport model to simulate the dynamical particle emission along a hypothetical focusing trajectory near the critical *** found that the focusing effect can lead to anomalous β_T dependence on ■/p,■/d and ■/~3 He *** examined the β_T dependence of ■/p and ■/d ratios of central Au+Au collisions at ■=7.7 to 200 GeV measured by the STAR experiment at ***,we only observe a negative slope in β_T dependence of ■/d ratio at ■=19.6 GeV,which indicates the trajectory evolution has passed through the critical *** the future,we could constrain the location of the critical point and/or width of the critical region by conducting precise measurements on the β_T dependence of the ■/d ratio at different energies and rapidity.

关键词： qcd critical point light nuclei heavy-ion collisions qcd phase diagram quark-gluon plasma

Chiral symmetry restoration and deconfinement in the contact interaction model of quarks with parallel electric and magnetic fields

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Chinese Physics C 2021年第7期45卷 111-121页

作者： Aftab Ahmad Institute of Physics Gomal University29220D.I.KhanKhyber PakhtunkhawPakistan

We study the impact of steady,homogeneous,and external parallel electric and magnetic field strengths(eE||eB)on the chiral symmetry breaking-restoration and confinement-deconfinement phase *** also sketch the phase diagram of quantum chromodynamics(qcd)at a finite temperature T and in the presence of background *** unified formalism for this study is based on the Schwinger-Dyson equations,symmetry preserving vector-vector contact interaction model of quarks,and an optimal time regularization *** T=0,in the purely magnetic case(i.e.,eE→0),we observe the well-known magnetic catalysis ***,in a pure electric field background(eB→0),the electric field tends to restore the chiral symmetry and deconfinement above the pseudo-critical electric field eE^(x,C)_(c).In the presence of both eE and eB,we determine the magnetic catalysis effect in the particular region where eB dominates over eE,whereas we observe the chiral inhibition(or electric chiral rotation)effect when eE overshadows *** finite T,in the pure electric field case,the phenomenon of inverse electric catalysis appears to exist in the proposed ***,for a pure magnetic field background,we observe the magnetic catalysis effect in the mean-field approximation and inverse magnetic catalysis with eB-dependent *** combined effects of eE and eB on the pseudo-critical T^(x,C)_(c)yields an inverse electromagnetic catalysis,with and without an eB-dependent effective coupling of the *** findings of this study agree well with the already predicted results obtained via lattice simulations and other reliable effective models of qcd.

关键词： chiral symmetry breaking confinement electric and magnetic fields schwinger-dyson equations qcd phase diagram

Event-by-event efficiency fluctuations and efficiency correction for cumulants of superposed multiplicity distributions in relativistic heavy-ion collision experiments

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Chinese Physics C 2018年第10期42卷 79-94页

作者： Shu He Xiaofeng Luo Key Laboratory of Quark ＆ Lepton Physics（MOE）and Institute of Particle Physics Central China Normal University Wuhan 430079China

We performed systematic studies on the effects of event-by-event efficiency fluctuations on efficiency correction for cumulant analysis in relativistic heavy-ion collision experiments. Experimentally, particle eficiencies of events measured under different experimental conditions should be different. For fluctuation measurements, the final event-by-event multiplicity distributions should be the superposed distributions of various type of events measured under different conditions. We demonstrate efficiency fluctuation effects using numerical simulation, in which we construct an event ensemble consisting of events with two different efficiencies. By using the mean particle efficiencies, we find that the efficiency corrected cumulants show large deviations from the original inputs when the discrepancy between the two efficiencies is large. We further studied the effects of efficiency fluctuations for the cumulants of net-proton distributions by implementing the UrQMD events of Au＋Au collisions at √SNN=7.7 GeV in a realistic STAR detector acceptance. We consider the unequal efficiency in two sides of the Time Projection Chamber （TPC）, multiplicity dependent efficiency, and the event-by-event variations of the collision vertex position along the longitudinal direction （Vz）. When the efficiencies fluctuate dramatically within the studied event sample, the effects of efficiency fluctuations have significant impacts on the efficiency corrections of cumulants with the mean efficiencies. We find that this effect can be effectively suppressed by binning the entire event ensemble into various sub-event samples, in which the efficiency variations are relatively small. The final efficiency corrected cumulants can be calculated from the weighted average of the corrected factorial moments of the sub-event samples with the mean efficiencies.

关键词： qcd critical point qcd phase diagram heavy-ion collisions higher moments