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1.
The centrality and energy dependence of rapidity correlation patterns are studied in Au+Au collisions by using AMPT with string melting, RQMD and UrQMD models. The behaviors of the short-range correlation (SRC) and the long-range correlation (LRC) are presented clearly by two spatial-position dependent correlation patterns. For centrality dependence, UrQMD and RQMD give similar results as those in AMPT, i.e., in most central collisions, the correlation structure is flatter and the correlation range is larger, which indicates a long range rapidity correlation. A long range rapidity correlation showing up in RQMD and UrQMD implies that parton interaction is not the only source of long range rapidity correlations. For energy dependence, AMPT with string melting and RQMD show quite different results. The correlation patterns in RQMD at low collision energies and those in AMPT at high collision energies have similar structures, i.e. a convex curve, while the correlation patterns in RQMD at high collision energies and those in AMPT at low collision energies show flat structures, having no position dependence. Long range rapidity correlation presents itself at high energy and disappears at low energy in RQMD, which also indicates that long range rapidity correlations may come from some trivial effects, rather than the parton interactions. 相似文献
2.
In order to trace azimuthal angle dependence of the initial interaction in ultra-relativistic heavy ion collision,two azimuthal multiplicity-correlation patterns - neighboring and fixed-to-arbitrary angularbin correlation patterns - are suggested.From the simulation of Au + Au collisions at √SNN = 200 GeV by using the Monte Carlo models RQMD with hadron re-scattering and AMPT with and without string melting,we observe that the correlation patterns change gradually from out-of-plane preferential one to inplane preferential one when the centrality of collision shifts from the central collision to peripheral collision,meanwhile the anisotropic collective flow v2 keeps positive in all cases.This regularity is found to be collision energy independent.The physics behind the two opposite trends of correlation patterns,in particular,the presence of out-of-plane correlation patterns at RHIC energy,are discussed. 相似文献
3.
In order to trace the initial interaction in ultra-relativistic heavy ion collision in all azimuthal directions, neighboring
angular-bin multiplicity correlation pattern is suggested. From the simulation of Au+Au collisions at ?{sNN }\sqrt {s_{NN} } = 200 GeV by using the Monte Carlo models RQMD with hadron re-scattering and AMPT with and without string melting, we observe
that the correlation pattern changes gradually from out-of-plane preferential one to inplane preferential one when the centrality
of collision shifts from central to peripheral. This regularity is found to be model and collision energy independent. The
physics behind the two opposite trends of correlation pattern is discussed. 相似文献
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5.
Partonic interactions and two particle transverse momentum correlations in Au + Au collisions at √sNN=130GeV 下载免费PDF全文
Partonic effects on two-particle transverse momentum correlations are studied for Au+Au collisions at \sqrt{s_{_{\rm NN}}}=130GeV in the Monte Carlo model, AMPT. This study demonstrates that in these collisions partonic interactions contribute significantly to the correlations. Additionally, model calculations are compared with data of the two-particle transverse momentum correlations measured by the STAR Collaboration at RHIC, and it is found that AMPT with string melting can well reproduce the measured centrality dependence of the two-particle transverse momentum correlations in Au+Au collisions at \sqrt{s_{_{\rm NN}}}=130GeV. 相似文献
6.
高能重离子碰撞中正负荷电粒子比单事例起伏研究 总被引:2,自引:0,他引:2
用强子和弦级联模型,JPCIAE及相应的Monte Carlo事例产生器,研究相对论性核–核碰撞中有限快度区间内正负荷电粒子比单事例起伏与能量、中心度、共振态衰变及快度间隔的关系.JPCIAE模型能够较好地符合CERN/SPS能区Pb+Pb碰撞的实验结果.本文还用此模型预言了RHIC能区Au+Au碰撞和ALICE能区Pb+Pb碰撞中的正负荷电粒子比单事例起伏.可以看出碰撞能量、中心度、共振态衰变及快度间隔对正负荷电粒子比单事例起伏的影响都不大. 相似文献
7.
The centrality, azimuthal and rapidity dependence of two-particle transverse-momentum correlations are studied for Au-Au collision at 200 GeV using RQMD (relativistic quantum molecular dynamics) with and without final hadron re-scattering models. The influences of the re-scattering effects on the measured correlations are discussed. The results are compared with those from current heavy ion experiments. 相似文献
8.
The centrality, azimuthal and rapidity dependence of two-particle transverse-momentum correlations are studied for Au-Au collision at 200 GeV using RQMD (relativistic quantum molecular dynamics) with and without final hadron re-scattering models. The influences of the re-scattering effects on the measured correlations are discussed. The results are compared with those from current heavy ion experiments. 相似文献
9.
For high-energy nucleus-nucleus collisions, we show that a combination of space-momentum correlations characteristic of radial expansion, together with the correlation between the position of a nucleon in the nucleus and its stopping, results in a very specific rapidity dependence of directed flow: a reversal of sign in the midrapidity region. We support our argument by RQMD model calculations for Au+Au collisions at sqrt[s] = 200A GeV. 相似文献
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Back BB Baker MD Barton DS Betts RR Ballintijn M Bickley AA Bindel R Budzanowski A Busza W Carroll A Decowski MP García E George N Gulbrandsen K Gushue S Halliwell C Hamblen J Heintzelman GA Henderson C Hofman DJ Hollis RS Hołyński R Holzman B Iordanova A Johnson E Kane JL Katzy J Khan N Kucewicz W Kulinich P Kuo CM Lin WT Manly S McLeod D Michałowski J Mignerey AC Nouicer R Olszewski A Pak R Park IC Pernegger H Reed C Remsberg LP Reuter M Roland C Roland G Rosenberg L Sagerer J Sarin P 《Physical review letters》2003,91(5):052303
We present measurements of the pseudorapidity distribution of primary charged particles produced in Au+Au collisions at three energies, sqrt[s(NN)]=19.6, 130, and 200 GeV, for a range of collision centrali-ties. The distribution narrows for more central collisions and excess particles are produced at high pseudorapidity in peripheral collisions. For a given centrality, however, the distributions are found to scale with energy according to the "limiting fragmentation" hypothesis. The universal fragmentation region described by this scaling grows in pseudorapidity with increasing collision energy, extending well away from the beam rapidity and covering more than half of the pseudorapidity range over which particles are produced. This approach to a universal limiting curve appears to be a dominant feature of the pseudorapidity distribution and therefore of the total particle production in these collisions. 相似文献
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Inam-ul Bashir 《Journal of Experimental and Theoretical Physics》2017,125(1):65-72
The collision centrality dependence of the yields per unit rapidity dN/dy along with their ratios for various hadrons produced in Au+Au collisions at different collision energies have been studied within the framework of unified statistical thermal freeze-out model (USTFM) taking into account both longitudinal and transverse hydrodynamic flows. Bulk freeze-out properties in terms of the thermal parameters, temperature and mid-rapidity baryon chemical potential at chemical freeze-out, obtained within the proposed model, which are in agreement with experimental data. The extracted chemical freeze-out temperature is found to depend weakly on the collision centrality. It is also found that this temperature is almost independent of the collision energies considered in this work. The closeness of the freeze-out temperature to the predicted phase-transition temperature suggests that the chemical freeze-out happens near hadronization. Furthermore, the dependence of the mid-rapidity chemical potential on the collision energy at different centralities, as well as the centrality dependence of the mid-rapidity size of the system in terms of the transverse size of the system, has been studied at the RHIC. The effect of resonance decay contributions has also been taken into account. 相似文献
14.
J.X. Zuo J.Y. Chen X.Z. Cai Y.G. Ma F. Liu P. Sorensen A.H. Tang H.Z. Huang J.H. Chen G.L. Ma C. Zhong 《The European Physical Journal C - Particles and Fields》2008,55(3):463-467
The elliptic flow v2 and the fourth order anisotropic flow v4 of (Ω+Ω̄) have been studied in the framework a parton–hadronic transport model, namely a multi-phase transport (AMPT) model,
for 197Au+197Au collisions at = 200 GeV and 62.4 GeV. The transverse momentum (pT) and the transverse kinetic energy (mT-m0) dependence of v2 and v4 are presented. The calculation in the AMPT model seems consistent with the STAR data. The results show that the v2 of (Ω+Ω̄) in 200 GeV obeys the constituent quark number scaling that has been observed for other mesons and baryons. Comparison
of (Ω+Ω̄) elliptic flow v2 in the default version of AMPT, the melting version of AMPT and the RQMD model calculation, shows that the parton cascade
process is important to reproduce the sizeable v2, and the string melting AMPT model preferably reproduces (Ω+Ω̄) elliptic flow v2 in 197Au+197Au collisions at = 200 GeV. The v2 of (Ω+Ω̄) in the 62.4 and 200 GeV collisions seem similar, and the pT dependence of (Ω+Ω̄) baryons’ v4 in 62.4 GeV and 200 GeV looks also similar in the string melting AMPT model, which indicates that a similar partonic matter
phase has been reached in both energies. 相似文献
15.
The φ meson productions in Au+Au and/or Pb+Pb collisions at AGS, SPS,
RHIC, and LHC energies have been studied systematically with a hadron and
string cascade model LUCIAE. After considering the energy dependence of the
model parameter α in string fragmentation function and adjusting it
to the experimental data of charged multiplicity to a certain extent,
the model predictions for φ meson yield, rapidity, and
transverse mass distributions are compatible with the experimental data at
AGS, SPS and RHIC energies. A calculation for Pb+Pb collisions at LHC energy
is given as well. The obtained fractional variable in string fragmentation
function shows a saturation in energy dependence. It is discussed that the
saturation of fractional variable in string fragmentation function might be a
qualitative representation of the energy dependence of nuclear transparency. 相似文献
16.
《Nuclear Physics A》1997,622(3):391-403
The production of pions, protons and deuterons is studied at a laboratory angle of 144° in 28Si+Pb collisions at 14.6 GeV/c per nucleon. The centrality dependence of the pion yields is studied over the full impact parameter range using a zero degree calorimeter. The results are compared with the hadronic cascade model RQMD. These calculations are generally in agreement with the experimental results. According to these calculations, the pion yield in our acceptance is completely dominated by Δ-decay at freeze-out. Our measurements thus support the importance of baryon resonance production as one of the central features of relativistic heavy ion collisions at AGS energies. Although the strength of the pion spectrum is adequately described for kinetic energies above 50 MeV, an additional very soft component is observed in the pion spectra which is not predicted by RQMD. This very soft component accounts for a significant fraction of the total pion yield in this rapidity range but remains unexplained. 相似文献
17.
Charged particle pseudorapidity distributions have been measured in Au+ Au collisions using the BRAHMS detector at RHIC. The
results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions
of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed. Keywords.
Relativistic heavy-ion collisions; charged hadron production; pseudorapidity distributions; centrality dependence; hard scattering
processes. 相似文献
18.
《中国物理C(英文版)》2016,(3)
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)~(1/2) = 7.7- 62.4 GeV.It is observed that for (sNN)~(1/2) 19.6 GeV Au+Au collisions, the short-range correlations of final particles have a trough at central pseudorapidity, while for (sNN)~(1/2) 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. 相似文献
19.
Transverse momentum and transverse mass distributions of charged hadrons produced in Au--Au collisions at high energies 下载免费PDF全文
The transverse momentum distribution and the transverse mass distribution of charged hadrons produced in nucleus nucleus collisions at high energies are described by using a two-cylinder model. The results calculated by the model are compared and found to be in agreement with the experimental data of the STAR and E895 Collaborations, measured in A~Au collisions at the relativistic heavy ion collider (RHIC) and alternating-gradient synchrotron (AGS) energies, respectively. In the energy range concerned, the excitation degree of emission source close to the central axis of cylinders increases obviously with the collision centrality and incident energy increasing, but it does not show any obvious change with the increase of the (pseudo)rapidity in central collisions. The excitation degree of emission source close to the side-surface of cylinders does not show any obvious change with the collision centrality, the (pseudo)rapidity, and the incident energy increasing. 相似文献
20.
Effects of centrality fluctuation and deuteron formation on the proton number cumulant in Au+Au collisions at s_(NN)~(1/2)=3 GeV from the JAM model 下载免费PDF全文
《中国物理C(英文版)》2021,(6)
We studied the effects of centrality fluctuation and deuteron formation on the cumulant(C_n) and correlation functions(k_n) of protons up to the sixth order in the most central(b3 fm) Au+Au collisions at s_(NN)~(1/2)=3 GeV in a microscopic transport model(JAM).The results are presented as a function of rapidity acceptance within the transverse momentum 0.4 p_T 2 GeV/c.We compared the results obtained by the centrality bin width correction(CBWC) using charged reference particle multiplicities with the CBWC using impact parameter bins.It was found that,at low energies,the centrality resolution for determining the collision centrality using charged particle multiplicities is not sufficient to reduce the initial volume fluctuation effect for higher-order cumulant analysis.New methods need to be developed to classify events with high centrality resolution for heavy-ion collisions at low energies.Finally,we observed that the formation of deuterons suppresses the higher-order cumulants and correlation functions of protons and found it to be similar to the efficiency effect.This work can serve as a noncritical baseline for the QCD critical point search in the high baryon density region. 相似文献