摘要：
We study the sign distribution of generalized magnetic susceptibilities in the temperature-external magnetic field plane using the three-dimensional three-state Potts model. We find that the sign of odd-order susceptibility is opposite in the symmetric (disorder) and broken (order) phases,but that of the even-order one remains positive when it is far away from the phase boundary. When the critical point is approached from the crossover side, negative fourth-order magnetic susceptibility is observable. It is also demonstrated that non-monotonic behavior occurs in the temperature dependence of the generalized susceptibilities of the energy. The finite-size scaling behavior of the specific heat in this model is mainly controlled by the critical exponent of the magnetic susceptibility in the three-dimensional Ising universality class.
关键词：
High cumulants;statistical uncertainty;statistics;QCD phase transition
摘要：
We study the influence of measured high cumulants of conserved charges on their associated statistical uncertainties in relativistic heavy-ion collisions. With a given number of events, the measured cumulants randomly fluctuate with an approximately normal distribution, while the estimated statistical uncertainties are found to be correlated with corresponding values of the obtained cumulants. Generally, with a given number of events, the larger the cumulants we measure, the larger the statistical uncertainties that are estimated. The error-weighted averaged cumulants are dependent on statistics. Despite this effect, however, it is found that the three sigma rule of thumb is still applicable when the statistics are above one million.
作者机构：
[Chen, Lizhu; Cui, Fenping] Nanjing Univ Informat Sci & Technol, Sch Phys & Optoelect Engn, Nanjing 210044, Jiangsu, Peoples R China.;[Chen, Lizhu; Wu, Yuanfang; Li, Zhiming] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Chen, Lizhu; Wu, Yuanfang; Li, Zhiming] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Chen, Lizhu] N;[Chen, Lizhu] C;Nanjing Univ Informat Sci & Technol, Sch Phys & Optoelect Engn, Nanjing 210044, Jiangsu, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
关键词：
The sixth order cumulant;Statistics;Non-critical contributions;Heavy-ion collisions
摘要：
We investigate the measurement of the sixth order cumulant and its ratio to the second order cumulant (C-6/C-2) in relativistic heavy-ion collisions. The influence of statistics and different methods of centrality bin width correction on C-6/C-2 of net-proton multiplicity distributions is demonstrated. There is no satisfactory method to extract C-6/C-2 with the current statistics recorded at lower energies by STAR at RHIC. With statistics comparable to the expected statistics at the planned future RHIC Beam Energy Scan II (BES II), no energy dependence of C-6/C-2 is observed in central collisions using the UrQMD model. We find that if the transition signal is as strong as predicted by the PQM model, then it is hopefully observed at the upcoming RHIC BES II. (C) 2016 Elsevier B.V. All rights reserved.
摘要：
Using a multi-phase transport model (AMPT) that includes both initial partonic and hadronic interactions, we study neighboring bin multiplicity correlations as a function of pseudorapidity in Au+Au collisions at √SNN = 7.7 — 62.4 GeV. It is observed that for √SNN <19.6 GeV Au+Au collisions, the short-range correlations of final particles have a trough at central pseudorapidity, while for √SNN >19.6 GeV AuAu collisions,the short-range correlations of final particles have a peak at central pseudorapidity. Our findings indicate that the pseudorapidity dependence of short-range correlations should contain some new physical information, and are not a simple result of the pseudorapidity distribution of final particles. The AMPT results with and without hadronic scattering are compared. It is found that hadron scattering can only increase the short-range correlations to some level, but is not responsible for the different correlation shapes for different energies. Further study shows that the different pseudorapidity dependence of short-range correlations are mainly due to partonic evolution and the following hadronization scheme.
关键词：
critical point;the sixth order cumulant;Ising model
摘要：
The high-order cumulants of conserved charges are suggested to be sensitive observables to search for the critical point of Quantum Chromodynamics (QCD). This has been calculated to the sixth order in experiments. Corresponding theoretical studies on the sixth order cumulant are necessary. Based on the universality of the critical behavior, we study the temperature dependence of the sixth order cumulant of the order parameter using the parametric representation of the three-dimensional Ising model, which is expected to be in the same universality class as QCD. The density plot of the sign of the sixth order cumulant is shown on the temperature and external magnetic field plane. We found that at non-zero external magnetic field, when the critical point is approached from the crossover side, the sixth order cumulant has a negative valley. The width of the negative valley narrows with decreasing external field. Qualitatively, the trend is similar to the result of Monte Carlo simulation on a finite-size system. Quantitatively, the temperature of the sign change is different. Through Monte Carlo simulation of the Ising model, we calculated the sixth order cumulant of different sizes of systems. We discuss the finite-size effects on the temperature at which the cumulant changes sign.
作者机构：
[Wu, Yuan-Fang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wu, Yuan-Fang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Wu, Yuan-Fang] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
摘要：
Using the CGC formalism, we calculate the two-gluon rapidity correlations of strong colour fields in pp, pA and AA collisions, respectively. If one trigger gluon is fixed at central rapidity, a ridge-like correlation pattern is obtained in symmetry pp and AA collisions, and a huge bump-like correlation pattern is presented in asymmetry pA collisions. It is demonstrated that long-range ridge-like rapidity correlations are caused by the stronger correlation with the gluon of colour source. These features are independent of the azimuthal angular of two selected gluon. They are qualitatively consistent with current observed data at LHC. The transverse momentum and incident energy dependence of the ridge and bump-like correlations are also systematically studied. The ridge is more likely observed at higher incident energy and lower transverse momentum of trigger gluon. (C) 2016 Elsevier B.V. All rights reserved.
期刊：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2015年42(1):015104- ISSN：0954-3899
通讯作者：
Pan, Xue
作者机构：
[Pan, Xue] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Pan, Xue] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
关键词：
Finite-size scaling;Generalized susceptibility;QCD phase transition;Three-dimensional three-state potts model
摘要：
It is pointed out that the finite-size effect is not negligible in locating the critical point of quantum colordynamics (QCD) phase transitions at current relativistic heavy ion collisions. The finite-size scaling form of the critical related observable is suggested. Its fixed point behavior at critical incident energy can be served as a reliable identification of a critical point and nearby boundary of QCD phase transition. How to experimentally find the fixed point behavior is demonstrated by using 3D-Ising model as an example. The validity of the method at finite detector acceptances at RHIC is also discussed.
作者机构：
[Xu, Mingmei] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Xu, Mingmei] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
关键词：
Heavy ion collisions;Quark deconfinement;QCD critical point;Inflection point;High cumulant
摘要：
In the universality class of the critical point of QCD, the appearance of the inflection point in the equation of state (EoS) is associated with the second order phase transition. The high cumulants of conserved quantities near the critical point are corresponding to the high derivatives of the EoS near the inflection point. The critical behavior of high cumulants of conserved charge near the QCD critical point, in particular, the sign change, is closely related to the appearance of inflection point. We show in general how the times of sign change of high cumulants relate to the order of derivative. We also demonstrate that the character of inflection point of EoS is as visible as the sign change of high cumulants in 3 systems, i.e., the van der Waals equation of fluid, the energy of spin model and the baryon number density of QCD matter. Therefore, we propose that the EoS, or the mean of baryon number density, should be measured and studied together with its higher cumulants in exploring the QCD critical point in heavy ion collisions. (C) 2014 Elsevier B.V. All rights reserved.
作者机构：
[Wu, Yuanfang; Xu, Mingmei; Pan, Xue; Zhang, Fan; Li, Zhiming] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wu, Yuanfang; Xu, Mingmei; Pan, Xue; Zhang, Fan; Li, Zhiming] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Chen, Lizhu] Nanjing Univ Informat Sci & Technol, Sch Phys & Optoelect Engn, Nanjing 210044, Jiangsu, Peoples R China.
通讯机构：
[Pan, Xue] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
摘要：
Poisson-like statistical fluctuations, which are caused by the finite number of produced particles, are estimated for the cumulants of conserved charges, i.e., net baryon, net electric, and net strangeness. They turn out to be the same as those baselines derived from the hadron resonance gas model. The energy and centrality dependence of net-proton cumulants at the Relativistic Heavy-Ion Collider (RHIC) are demonstrated to be mainly caused by statistical fluctuations. By subtracting the statistical fluctuations, the dynamical kurtosis of net- and total-proton cumulants from two versions of a multi-phase transport model and the ultra-relativistic quantum molecular dynamics model at current RHIC collision energies are presented. It is found that the observed sign change of the dynamical kurtosis of the net-proton cumulant cannot be reproduced by these three transport models. There is no significant difference between the net- and total-proton kurtosis in model calculations, in contrast to the data at RHIC.
作者：
Agakishiev, H.*;Aggarwal, M. M.;Ahammed, Z.;Alakhverdyants, A. V.;Alekseev, I.;...
期刊：
PHYSICAL REVIEW C,2014年89(4) ISSN：2469-9985
通讯作者：
Agakishiev, H.
作者机构：
[Kechechyan, A.; Kizka, V.; Agakishiev, H.; Averichev, G. S.; Bunzarov, I.; Efimov, L. G.; Panebratsev, Y.; Alakhverdyants, A. V.; Shahaliev, E.; Rogachevskiy, O. V.; Fedorisin, J.; Zoulkarneev, R.; Zoulkarneeva, Y.; Tokarev, M.; Filip, P.; Lednicky, R.; Dedovich, T. G.; Heppelmann, S.; Vokal, S.] Joint Inst Nucl Res, Dubna 141980, Russia.;[Underwood, D. G.; Krueger, K.; Bridgeman, A.; Spinka, H. M.] Argonne Natl Lab, Argonne, IL 60439 USA.;[Ullrich, T.; Pile, P.; Lamont, M. A. C.; LeVine, M. J.; Ljubicic, T.; Xu, Z.; Ogawa, A.; Ruan, L.; Tang, A. H.; Videbaek, F.; Fine, V.; Fisyak, Y.; Beavis, D. R.; Lauret, J.; Bland, L. C.; Longacre, R. S.; Webb, J. C.; Christie, W.; Arkhipkin, D.; Debbe, R. R.; Lebedev, A.; Burton, T. P.; Dunlop, J. C.; Gordon, A.; Landgraf, J. M.; Love, W. A.; Yip, K.; Didenko, L.; Guryn, W.; Van Buren, G.; Lee, J. H.] Brookhaven Natl Lab, Upton, NY 11973 USA.;[Perkins, C.; Crawford, H. J.; Engelage, J.; Alford, J.; Judd, E. G.] Univ Calif Berkeley, Berkeley, CA 94720 USA.;[Draper, J. E.; Cebra, D.; Brovko, S. G.; Beavis, D. R.; Sangaline, E.; Reed, R.; de la Barca Sanchez, M. Calderon; Romero, J. L.; Salur, S.; Haag, B.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Agakishiev, H.] J;Joint Inst Nucl Res, Dubna 141980, Russia.
摘要：
STAR measurements of dihadron azimuthal correlations (Lambda phi) are reported in midcentral (20-60%) Au + Au collisions at v root sNN = 200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, phi(s) = | phi(1) -psi(EP)|. The elliptic (v(2)), triangular (v(3)), and quadratic (v(4)) flow harmonic backgrounds are subtracted using the zero yield at mini + Au collisions. It is found that a finite near-side (| Delta phi | < pi/2) long-range pseudorapidity correlation (ridge) is present in the in-plane direction (phi(s) similar to 0). The away-side (| Delta phi | > pi/2) correlation shows a modification from d+ Au data, varying with fs. The modification may be a consequence of path-length-dependent jet quenching and may lead to a better understanding of high-density QCD.
摘要：
Considering different universality classes of the QCD phase transitions, we perform the Monte Carlo simulations of the 3-dimensional O(1, 2, 4) models at vanishing and non-vanishing external field, respectively. Interesting high-order cumulants of the order parameter and energy from O(1) (Ising) spin model, and the cumulants of the energy from O(2) and O(4) spin models are presented. The generic features of the cumulants are discussed. They are instructive to the high-order cumulants of the net baryon number in the QCD phase transitions. (C) 2013 Elsevier B.V. All rights reserved.
作者机构：
[Wu Yuan-Fang; Li Lin] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wu Yuan-Fang; Li Lin] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang Mei-Juan] China Univ Geosci, Dept Phys, Wuhan 430074, Peoples R China.
通讯机构：
[Li Lin] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
关键词：
neighboring azimuthal bin-bin multiplicity correlation;shear viscosity;relativistic heavy ion collision
摘要：
Neighboring azimuthal bin-bin multiplicity correlation is suggested to be a good measure for internal layer-to-layer interactions of the formed matter in relativistic heavy ion collisions. It is shown to be directly related to the shear viscosity of the formed matter. As an application of this method, the shear viscosity in the samples generated by a multi-phase transport model (AMPT) is estimated. The results are in qualitative agreement with the theoretical calculation from microscopic interactions, i.e., the larger the scattering cross section, the smaller the shear viscosity.
关键词：
at a fixed centrality;elliptic flow;initial eccentricity;local equilibrium
摘要：
In this paper, elliptic flow is studied at a fixed centrality in Au+Au collisions at root s(NN)=200 GeV in the AMPT model. It is observed that as the participants increase, elliptic flow either increases or decreases at a different fixed impact parameter, but it does not have a trivial fluctuation. It is analyzed that the initial space anisotropy dominates the participant dependence of elliptic flow in near-central collisions(b=5 fm) and mid-central collisions(b=8 fm), while the interaction between particles can mainly answer for the elliptic flow behavior with the participant in peripheral collisions (b=12 fm). To distinguish the pure geometrical effect, elliptic flow scaled by initial eccentricity is studied. It is found that the ratio v(2)/epsilon increases with the participant and reaches a saturation when the participant is large enough, indicating that the collision system may reach a local equilibrium.
摘要：
Based on the universal properties of a critical point in different systems and that the QCD phase transitions fall into the same universality classes as the 3-dimensional Ising, O(2) or O(4) spin models, the critical behavior of cumulants and higher cumulant ratios of the order parameter from the three kinds of spin models is studied. We found that all higher cumulant ratios change dramatically the sign near the critical temperature. The qualitative critical behavior of the same order cumulant ratio is consistent in these three models.
期刊：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2013年40(7):075104 ISSN：0954-3899
通讯作者：
Li, Lin
作者机构：
[Li, Lin; Wu, Yuanfang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Li, Lin; Wu, Yuanfang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Li, Na] Huazhong Univ Sci & Technol, Wuhan 430074, Peoples R China.
通讯机构：
[Li, Lin] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
摘要：
We suggest using the azimuthal distribution of mean transverse (radial) rapidity of final state particles, rather than the standard azimuthal multiplicity distribution, as a more direct measure of the transverse motion of the source. Using a sample generated by the AMPT model with string melting, we demonstrate that the azimuthal amplitude of the suggested distribution characterizes the anisotropic radial flow and coincides with the parameter of anisotropic radial rapidity extracted from a generalized blast-wave parametrization.
