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.
作者：
Agakishiev, G.*;Aggarwal, M. M.;Ahammed, Z.;Alakhverdyants, A. V.;Alekseev, I.;...
期刊：
PHYSICAL REVIEW C,2012年85(1) ISSN：2469-9985
通讯作者：
Agakishiev, G.
作者机构：
[Kechechyan, A.; Kizka, V.; Agakishiev, G.; Averichev, G. S.; Bunzarov, I.; Efimov, L. G.; Panebratsev, Y.; Alakhverdyants, A. V.; Shahaliev, E.; Rogachevskiy, O. V.; Fedorisin, J.; Zoulkarneeva, Y.; Tokarev, M.; Filip, P.; Lednicky, R.; Dedovich, T. G.; 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.; Fine, V.; Fisyak, Y.; Videbk, F.; Beavis, D. R.; Lauret, J.; Bland, L. C.; Longacre, R. S.; Webb, J. C.; Sorensen, P.; Christie, W.; Arkhipkin, D.; Debbe, R. R.; Lebedev, A.; Burton, T. P.; Dunlop, J. C.; Gordon, A.; Landgraf, J. M.; Yip, K.; Didenko, L.; Guryn, W.; Mitrovski, M. K.; Van Buren, G.; Lee, J. H.] Brookhaven Natl Lab, Upton, NY 11973 USA.;[Perkins, C.; Crawford, H. J.; Engelage, J.; Judd, E. G.] Univ Calif Berkeley, Berkeley, CA 94720 USA.;[Sanchez, M. Calderon de la Barca; Mall, O. I.; Draper, J. E.; Cebra, D.; Brovko, S. G.; Sangaline, E.; Reed, R.; Romero, J. L.; Salur, S.; Haag, B.; Liu, H.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Agakishiev, G.] J;Joint Inst Nucl Res, Dubna 141980, Russia.
摘要：
This paper reports results for directed flow v(1) and elliptic flow v(2) of charged particles in Cu + Cu collisions at root s(NN) = 22.4 GeV at the Relativistic Heavy Ion Collider. The measurements are for the 0-60% most central collisions, using charged particles observed in the STAR detector. Our measurements extend to 22.4-GeV Cu + Cu collisions the prior observation that v1 is independent of the system size at 62.4 and 200 GeV and also extend the scaling of v(1) with eta/y(beam) to this system. The measured v(2)(p(T)) in Cu + Cu collisions is similar for root s(NN) throughout the range 22.4 to 200 GeV. We also report a comparison with results from transport model (ultrarelativistic quantum molecular dynamics and multiphase transport model) calculations. The model results do not agree quantitatively with the measured v(1)(eta), v(2)(p(T)), and v(2)(eta).
作者：
Agakishiev, G.*;Aggarwal, M. M.;Ahammed, Z.;Alakhverdyants, A. V.;Alekseev, I.;...
期刊：
PHYSICAL REVIEW C,2012年85(1) ISSN：2469-9985
通讯作者：
Agakishiev, G.
作者机构：
[Kechechyan, A.; Kizka, V.; Agakishiev, G.; Averichev, G. S.; Bunzarov, I.; Efimov, L. G.; Panebratsev, Y.; Alakhverdyants, A. V.; Shahaliev, E.; Rogachevskiy, O. V.; Fedorisin, J.; Zoulkarneeva, Y.; Tokarev, M.; Filip, P.; Lednicky, R.; Dedovich, T. G.; Vokal, S.] Joint Inst Nucl Res, Dubna 141980, Russia.;[Gliske, S.; Underwood, D. G.; Krueger, K.; 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.; Fisyak, Y.; Beavis, D. R.; Lauret, J.; Bland, L. C.; Longacre, R. S.; Webb, J. C.; Sorensen, P.; Christie, W.; Arkhipkin, D.; Debbe, R. R.; Lebedev, A.; Burton, T. P.; Dunlop, J. C.; Landgraf, J. M.; Yip, K.; Didenko, L.; Guryn, W.; Mitrovski, M. K.; Van Buren, G.; Lee, J. H.] Brookhaven Natl Lab, Upton, NY 11973 USA.;[Perkins, C.; Crawford, H. J.; Engelage, J.; Judd, E. G.] Univ Calif Berkeley, Berkeley, CA 94720 USA.;[Sanchez, M. Calderon de la Barca; Mall, O. I.; Draper, J. E.; Cebra, D.; Brovko, S. G.; Sangaline, E.; Reed, R.; Romero, J. L.; Haag, B.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Agakishiev, G.] J;Joint Inst Nucl Res, Dubna 141980, Russia.
摘要：
Two-particle azimuthal (Delta phi) and pseudorapidity (Delta eta) correlations using a trigger particle with large transverse momentum (p(T)) in d+Au, Cu+Cu, and Au+Au collisions at root s(NN) = 62.4 GeV and 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider are presented. The near-side correlation is separated into a jet-like component, narrow in both Delta phi and Delta eta, and the ridge, narrow in Delta phi but broad in Delta eta. Both components are studied as a function of collision centrality, and the jet-like correlation is studied as a function of the trigger and associated p(T). The behavior of the jet-like component is remarkably consistent for different collision systems, suggesting it is produced by fragmentation. The width of the jet-like correlation is found to increase with the system size. The ridge, previously observed in Au+Au collisions at root s(NN) = 200 GeV, is also found in Cu+Cu collisions and in collisions at root s(NN) = 62.4 GeV, but is found to be substantially smaller at root s(NN) = 62.4 GeV than at root s(NN) = 200 GeV for the same average number of participants (< N-part >). Measurements of the ridge are compared to models.
摘要：
Azimuthal distributions of radial (transverse) momentum, mean radial momentum, and mean radial velocity of final-state particles are suggested for relativistic heavy ion collisions. Using the AMPT transport model with string melting, the distributions of Au+Au collisions at 200 GeV are presented and studied. It is demonstrated that the distribution of total radial momentum is more sensitive to the anisotropic expansion, as the anisotropies of final-state particles and their associated transverse momentums are both counted in the measurement. The mean radial velocity distribution is compared with the radial flow velocity. The thermal motion contributes an isotropic constant to the mean radial velocity.
摘要：
Accounting for the influence of system size in relativistic heavy ion collisions, the finite-size form of a critical related observable is suggested. The fixed-point and straight line methods are proposed in exploring the QCD critical point and phase boundary in relativistic heavy ion collisions. As an application, the finitesize behaviour of the ratios of higher net-proton cumulants, dynamical electric charge fluctuations, and transverse momentum correlations in Au + Au collisions at RHIC are examined.
作者：
Agakishiev, G.*;Aggarwal, M. M.;Ahammed, Z.;Alakhverdyants, A. V.;Alekseev, I.;...
期刊：
PHYSICAL REVIEW C,2012年86(6) ISSN：2469-9985
通讯作者：
Agakishiev, G.
作者机构：
[Kechechyan, A.; Kizka, V.; Agakishiev, G.; Averichev, G. S.; Bunzarov, I.; Efimov, L. G.; Panebratsev, Y.; Alakhverdyants, A. V.; Shahaliev, E.; Rogachevskiy, O. V.; Fedorisin, J.; Zoulkarneeva, Y.; Tokarev, M.; Filip, P.; Lednicky, R.; Dedovich, T. G.; Vokal, S.] Joint Inst Nucl Res, Dubna 141980, Russia.;[Underwood, D. G.; Krueger, K.; 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.; Sorensen, P.; Christie, W.; Arkhipkin, D.; Debbe, R. R.; Lebedev, A.; Burton, T. P.; Dunlop, J. C.; Gordon, A.; Landgraf, J. M.; Yip, K.; Didenko, L.; Mitrovski, M. K.; Van Buren, G.; Lee, J. H.] Brookhaven Natl Lab, Upton, NY 11973 USA.;[Perkins, C.; Crawford, H. J.; Engelage, J.; Judd, E. G.] Univ Calif Berkeley, Berkeley, CA 94720 USA.;[Sanchez, M. Calderon de la Barca; Mall, O. I.; Draper, J. E.; Cebra, D.; Brovko, S. G.; Sangaline, E.; Reed, R.; Romero, J. L.; Salur, S.; Haag, B.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Agakishiev, G.] J;Joint Inst Nucl Res, Dubna 141980, Russia.
摘要：
We present two-dimensional (2D) two-particle angular correlations measured with the STAR detector on relative pseudorapidity eta and azimuth phi for charged particles from Au-Au collisions at root s(NN) = 62 and 200 GeV with transverse momentum p(t) >= 0.15 GeV/c, vertical bar eta vertical bar <= 1, and 2 pi in azimuth. Observed correlations include a same-side (relative azimuth <pi/2) 2D peak, a closely related away-side azimuth dipole, and an azimuth quadrupole conventionally associated with elliptic flow. The same-side 2D peak and away-side dipole are explained by semihard parton scattering and fragmentation (minijets) in proton-proton and peripheral nucleus-nucleus collisions. Those structures follow N-N binary-collision scaling in Au-Au collisions until midcentrality, where a transition to a qualitatively different centrality trend occurs within one 10% centrality bin. Above the transition point the number of same-side and away-side correlated pairs increases rapidly relative to binary-collision scaling, the eta width of the same-side 2D peak also increases rapidly (eta elongation), and the phi width actually decreases significantly. Those centrality trends are in marked contrast with conventional expectations for jet quenching in a dense medium. The observed centrality trends are compared to perturbative QCD predictions computed in HIJING, which serve as a theoretical baseline, and to the expected trends for semihard parton scattering and fragmentation in a thermalized opaque medium predicted by theoretical calculations and phenomenological models. We are unable to reconcile a semihard parton scattering and fragmentation origin for the observed correlation structure and centrality trends with heavy-ion collision scenarios that invoke rapid parton thermalization. If the collision system turns out to be effectively opaque to few-GeV partons the present observations would be inconsistent with the minijet picture discussed here. DOI: 10.1103/PhysRevC.86.064902
作者机构：
[Kechechyan, A.; Kizka, V.; Agakishiev, G.; Averichev, G. S.; Bunzarov, I.; Efimov, L. G.; Panebratsev, Y.; Alakhverdyants, A. V.; Shahaliev, E.; Rogachevskiy, O. V.; Fedorisin, J.; Zoulkarneeva, Y.; Tokarev, M.; Filip, P.; Lednicky, R.; Dedovich, T. G.; 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.;[Jones, P. G.; Nelson, J. M.; Barnby, L. S.] Univ Birmingham, Birmingham, W Midlands, England.;[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.; Sorensen, P.; Christie, W.; Arkhipkin, D.; Debbe, R. R.; Lebedev, A.; Burton, T. P.; Dunlop, J. C.; Gordon, A.; Landgraf, J. M.; Yip, K.; Didenko, L.; Guryn, W.; Mitrovski, M. K.; Van Buren, G.; Lee, J. H.] Brookhaven Natl Lab, Upton, NY 11973 USA.;[Mall, O. I.; Draper, J. E.; Cebra, D.; Brovko, S. G.; Sangaline, E.; Reed, R.; de la Barca Sanchez, M. Calderon; Romero, J. L.; Salur, S.; Haag, B.; Liu, H.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Agakishiev, G.] J;Joint Inst Nucl Res, Dubna 141980, Russia.
作者：
Agakishiev, G.*;Aggarwal, M. M.;Ahammed, Z.;Alakhverdyants, A. V.;Alekseev, I.;...
期刊：
PHYSICAL REVIEW C,2012年86(1) ISSN：2469-9985
通讯作者：
Agakishiev, G.
作者机构：
[Kechechyan, A.; Kizka, V.; Agakishiev, G.; Averichev, G. S.; Bunzarov, I.; Efimov, L. G.; Panebratsev, Y.; Alakhverdyants, A. V.; Shahaliev, E.; Rogachevskiy, O. V.; Fedorisin, J.; Zoulkarneeva, Y.; Tokarev, M.; Filip, P.; Lednicky, R.; Dedovich, T. G.; 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.; Sorensen, P.; Christie, W.; Arkhipkin, D.; Debbe, R. R.; Lebedev, A.; Burton, T. P.; Dunlop, J. C.; Gordon, A.; Landgraf, J. M.; Yip, K.; Didenko, L.; Guryn, W.; Mitrovski, M. K.; Van Buren, G.; Lee, J. H.] Brookhaven Natl Lab, Upton, NY 11973 USA.;[Perkins, C.; Crawford, H. J.; Engelage, J.; Judd, E. G.] Univ Calif Berkeley, Berkeley, CA 94720 USA.;[Sanchez, M. Calderon de la Barca; Mall, O. I.; Draper, J. E.; Cebra, D.; Brovko, S. G.; Sangaline, E.; Reed, R.; Romero, J. L.; Salur, S.; Haag, B.; Liu, H.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Agakishiev, G.] J;Joint Inst Nucl Res, Dubna 141980, Russia.
摘要：
We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants nu(2) (nu(2){2} and nu(2){4}) for Au + Au and Cu + Cu collisions at center-of-mass energies root S-NN = 62.4 and 200 GeV. The difference between nu(2){2}(2) and nu(2){4}(2) is related to nu(2) fluctuations (sigma(nu 2)) and nonflow (delta(2)). We present an upper limit to sigma(nu 2)/nu 2. Following the assumption that eccentricity fluctuations sigma(epsilon) dominate nu(2) fluctuations nu(2)/sigma nu(2) approximate to epsilon/sigma epsilon we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with nu(2){2} and nu(2){4}. We also present results on the ratio of nu(2) to eccentricity.
摘要：
QCD deconfinement phase transition is supposed to be the same universality class as the 3D-Ising model. According to the universality of critical behavior, the Binder-like ratios and ratios of higher cumulants of order parameter near the critical temperature in the 3D-Ising model are studied. The Binder-like ratio is shown to be a step function of temperature. The critical point is the intersection of the ratios of different system sizes between two platforms. The normalized cumulant ratios, like the Skewness and Kurtosis, do not diverge with correlation length, contrary to the corresponding cumulants. Possible applications of these characters in locating critical point in relativistic heavy ion collisions are discussed.
作者机构：
[Pruthi, N. K.; Bhati, A. K.; Aggarwal, M. M.] Panjab Univ, Chandigarh 160014, India.;[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.; Fine, V.; Fisyak, Y.; Videbk, F.; Beavis, D. R.; Lauret, J.; Bland, L. C.; Longacre, R. S.; Webb, J. C.; Sorensen, P.; 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.; Judd, E. G.; Ng, M. J.] Univ Calif Berkeley, Berkeley, CA 94720 USA.;[Mall, O. I.; Draper, J. E.; Cebra, D.; Brovko, S. G.; Sangaline, E.; Reed, R.; de la Barca Sanchez, M. Calderon; Romero, J. L.; Salur, S.; Haag, B.; Liu, H.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Aggarwal, M. M.] P;Panjab Univ, Chandigarh 160014, India.
作者：
Agakishiev, H.*;Aggarwal, M. M.;Ahammed, Z.;Alakhverdyants, A. V.;Alekseev, I.;...
期刊：
Nature,2011年473(7347):353-356 ISSN：1476-4687
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.; Vokal, S.] Joint Inst Nucl Res, Dubna 141980, Russia.;[Bhati, A. K.; K. Pruthi, N.; Aggarwal, M. M.] Panjab Univ, Chandigarh 160014, India.;[Sakrejda, I.; Wieman, H.; Masui, H.; Schmah, A. M.; Porter, J.; Sichtermann, E. P.; Naglis, M.; Grebenyuk, O. G.; Sun, X. M.; Ploskon, M. A.; Thomas, J. H.; Poskanzer, A. M.; Ritter, H. G.; Zhang, Y.; Powell, C. B.; Hjort, E.; Jacobs, P.; Kiryluk, J.; Klein, S. R.; Olson, D.; Odyniec, G.; Matis, H. S.; Symons, T. J. M.; Ahammed, Z.; Dong, X.] Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA.;[Koroleva, L.; Svirida, D. N.; Morozov, B.; Bordyuzhin, I. G.; Alekseev, I.] Alikhanov Inst Theoret & Expt Phys, Moscow 117218, Russia.;[Joseph, J.; Vanfossen, J. A., Jr.; Pandit, Y.; Zhang, W. M.; Kumar, L.; Anderson, B. D.; Margetis, S.; Alford, J.; Keane, D.; Bouchet, J.; Subba, N. L.] Kent State Univ, Kent, OH 44242 USA.
通讯机构：
Joint Institute for Nuclear Research, Russian Federation
摘要：
High-energy nuclear collisions create an energy density similar to that of the Universe microseconds after the Big Bang(1); in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high-energy accelerator of heavy nuclei provides an efficient means of producing and studying antimatter. The antimatter helium-4 nucleus ((4)(He) over bar), also known as the anti-alpha ((alpha) over bar), consists of two antiprotons and two antineutrons (baryon number B = -4). It has not been observed previously, although the alpha-particle was identified a century ago by Rutherford and is present in cosmic radiation at the ten per cent level(2). Antimatter nuclei with B -1 have been observed only as rare products of interactions at particle accelerators, where the rate of antinucleus production in high-energy collisions decreases by a factor of about 1,000 with each additional antinucleon(3-5). Here we report the observation of (4)<(He) over bar, the heaviest observed antinucleus to date. In total, 18 (4)(He) over bar counts were detected at the STAR experiment at the Relativistic Heavy Ion Collider (RHIC; ref. 6) in 10(9) recorded gold-on-gold (Au+Au) collisions at centre-of-mass energies of 200 GeV and 62 GeV per nucleon-nucleon pair. The yield is consistent with expectations from thermodynamic(7) and coalescent nucleosynthesis(8) models, providing an indication of the production rate of even heavier antimatter nuclei and a benchmark for possible future observations of (4)(He) over bar in cosmic radiation.
