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1.
It is demonstrated that with Heinz's collective flow model charged particle distributions at AGS and lower SPS energies (less than 20 GeV/n) ,can successfully be analyzed,but that the model fails for the RHIC data.Heinz's model calculation underestimates the tails of the charged particle distributions from RHIC,the discrepancy becoming bigger as the energy increases.To study the multiplicity distributions at RHIC we develop the so-cailed"Thermalization Component Model",which is based on Heinz's collective flow model.It is realized that the limitation of phase space of collective flow can be reflected in that of the thermalization region.By comparing the contributions of particle production from the thermalization regions at different energies and different centralities,we can deepen our understanding of the features of collective motion at RHIC. 相似文献
2.
首先利用相对论纵向非均匀集体流模型讨论RHIC能区的净质子分布特征,并分别与AGS,SPS的实验结果比较,发现,RHIC能区所产生的粒子系统具有很强的非均匀分布特征,表现为很强的核透明性,并分析了非均匀集体流模型与实验中的核阻止特性的紧密联系,接着分别研究了RHIC能区所产生质子、反质子和净质子的分布,这些研究可以帮助我们深入了解最新的RHIC能区的粒子分布和核阻止特征. 相似文献
3.
Back BB Baker MD Barton DS Betts RR Bindel R Budzanowski A Busza W Carroll A Decowski MP Garcia E George N Gulbrandsen K Gushue S Halliwell C Hamblen J Henderson C Hofman D Hollis RS Hołyński R Holzman B Iordanova A Johnson E Kane J Katzy J Khan N Kucewicz W Kulinich P Kuo CM Lin WT Manly S McLeod D Michałowski J Mignerey A 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 Sawicki P Skulski W Steadman SG Steinberg P 《Physical review letters》2002,89(22):222301
This paper describes the measurement of collective flow for charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal hit anisotropy is presented over a wide range of pseudorapidity (-5.0相似文献
4.
在总结双柱模型计算结果的基础上, 用该模型对交变梯度同步加速器(AGS)和相对论性重离子对撞机(RHIC)能区核-核碰撞中的领头粒子效应进行了统一分析. 结果表明:在AGS和RHIC能区, 不同中心性核-核碰撞中带电粒子(赝)快度分布的不同, 主要由领头粒子的贡献影响; 如果扣除领头粒子的贡献, 不同中心性核-核碰撞中带电粒子的(赝)快度分布有相同的形状. 相似文献
5.
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
6.
A. Ya. Berdnikov D. A. Ivanishchev D. O. Kotov V. G. Riabov Yu. G. Riabov B. M. Samsonov 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(10):1179-1180
It has long been believed that small colliding systems (p+Au, d+Au, 3He + Au) are can only be used to study the collective effects of cold nuclear matter. However, recent studies on the RHIC and LHC accelerators indicate there are flowlike collective effects characterized by the high multiplicity of charged particles produced in these collisions. Whether these effects result from the hydrodynamic expansion of a dense and hot thermalized medium or are caused by the initial state remains an open question. This work reports the results from measuring flow characteristics in d + Au and 3He + Au collisions at an energy of 200 GeV in the PHENIX experiment on the RHIC collider. Attempts to describe the results theoretically are discussed. 相似文献
7.
We analyze elliptic flow from SIS to RHIC energies systematically in a realistic dynamical cascade model. We compare our results
with the recent data from STAR and PHOBOS collaborations on elliptic flow of charged particles at midrapidity in Au+ Au collisions
at RHIC. In the analysis of elliptic flow at RHIC energy, we find a good fitting with data at 1.5 times a scaling factor to
our model, which characterizes that the model is required to have extra pressure generated from the subsequent parton scattering
after the initial minijet production. In energy dependence of elliptic flow, we notice re-hardening nature at RHIC energies.
Both these two observations would probably imply the possible formation of quark-gluon plasma. 相似文献
8.
9.
Elena Bruna 《The European Physical Journal C - Particles and Fields》2009,62(1):133-137
The measurement of jet fragmentation functions in p+p collisions at 200 GeV is of great interest because it provides a baseline
to study jet quenching in heavy-ion collisions. It is expected that jet quenching in nuclear matter modifies the jet energy
and multiplicity distributions, as well as the jet hadrochemical composition. Therefore, a systematic study of the fragmentation
functions for charged hadrons and identified particles is a goal both in p+p and Au+Au collisions at RHIC. Studying fragmentation
functions for identified particles is interesting in p+p by itself because it provides a test of NLO calculations at RHIC
energies. We present a systematic comparison of jet energy spectra and fragment distributions using different jet-finding
algorithms in p+p collisions in STAR. Fragmentation functions of charged and neutral strange particles are also reported for
different jet energies. 相似文献
10.
We compare the dispersion of the charges in a central rapidity box according to the dual parton model with the predictions
of statistical models. Significant deviations are found in heavy ion collisions at RHIC and LHC energies. Hence the charged
particle fluctuations should provide a clear signal of the dynamics of heavy ion processes. They should allow one to directly
measure the degree of thermalization in a quantitative way.
Received: 7 November 2000 / Revised version: 4 September 2001 / Published online: 5 October 2001 相似文献
11.
《Physical review letters》2004,92(11):112301
Transverse mass and rapidity distributions for charged pions, charged kaons, protons, and antiprotons are reported for square root of [sNN]=200 GeV pp and Au+Au collisions at Relativistic Heary Ion Collider (RHIC). Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and long duration from chemical to kinetic freeze-out in central Au+Au collisions. The chemical freeze-out temperature appears to be independent of initial conditions at RHIC energies. 相似文献
12.
First observations of elliptic flow in Au-Au collisions at RHIC have been interpreted as evidence that the colliding system
reaches thermal equilibrium. We discuss some of the arguments leading to this conclusion and show that a more accurate analysis
is needed, which the standard flow analysis may not provide. We then present a new method of flow analysis, based on a systematic
study of multiparticle azimuthal correlations. This method allows one to test quantitatively the collective behaviour of the
interacting system. It has recently been applied by the STAR Collaboration at RHIC. 相似文献
13.
14.
The energy and centrality dependencies of charged particle pseudorapidity density in relativistic nuclearcollisions were studied using a hadron and string cascade model, JPCIAE. Both the relativistic p+p experimental dataand the PHOBOS and PHENIX Au+Au data at RHIC energy could be fairly reproduced within the framework ofJPCIAE model and without retuning the model parameters. The predictions for Pb + Pb collisions at the LHC energywere also given. We computed the participant nucleon distributions using different methods. It was found that thenumber of participant nucleons is not a well defined variable both experimentally and theoretically. Thus it may beinappropriate to use the charged particle pseudorapidity density per participant pair .as a function of the number ofparticipant nucleons for distinguishing various theoretical models. 相似文献
15.
N. Borghini 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):27-31
The large elliptic flow observed in Au- Au collisions at RHIC is often put forward as a compelling evidence for the formation
of a strongly interacting quark-gluon plasma. The main argument is that the measured elliptic flow is as large as the value
given by fluid dynamics models that assume complete thermalization. It is argued that this claim may not be justified, since
a detailed examination of experimental data rather suggests that the system created is not fully equilibrated at the time
when anisotropic flow develops. 相似文献
16.
Anisotropic transverse flow is studied in Pb+Pb and Au+Au collisions at SPS and RHIC energies. The centrality and transverse momentum dependence at midrapidity of the elliptic flow coefficient v2 is calculated in the hydrodynamic and low density limits. Hydrodynamics is found to agree well with the RHIC data for semicentral collisions up to transverse momenta of 1–1.5 GeV/c, but it considerably overestimates the measured elliptic flow at SPS energies. The low density limit LDL is inconsistent with the measured magnitude of v2 at RHIC energies and with the shape of its pt-dependence at both RHIC and SPS energies. The success of the hydrodynamic model points to very rapid thermalization in Au+Au collisions at RHIC and provides a serious challenge for kinetic approaches based on classical scattering of on-shell particles. 相似文献
17.
大入射能量范围内重离子输运过程的动力学性质研究 总被引:1,自引:0,他引:1
基于一个改进的微观动力学输运模型——极端相对论量子分子动力学(UrQMD), 较为系统地研究了从SIS能区到AGS和SPS能区, 再到RHIC能区, 入射能量跨5个数量级的重离子核反应及多个人们感兴趣的实验观测量, 如粒子产额、 集体流、 核阻止以及两粒子HBT关联等。研究表明, 不论单粒子观测量, 还是两粒子关联观测量, 都能自洽地由同一个输运模型加以描述。Based on one updated microscopic transport model Ultra relativistic Quantum Molecular Dynamics (UrQMD) with modifications of both potentials and two body scattering cross sections, quite a few interesting observables, such as yields, collective flows, the nuclear stopping, and the HBT two particle interferometry, are systematically investigated for heavy ion collisions within a large beam energy regime of five orders of magnitude (from SIS, AGS, SPS up to RHIC). It is shown that a consistent explanation can be received from both single particle and two particle related observables. 相似文献
18.
We compare elliptic flow evolution from ideal hydrodynamics and covariant parton transport theory, and show that, for conditions expected at RHIC, dissipation significantly reduces elliptic flow even for extreme parton cross sections and/or densities sigma(gg) x dN/d eta(b=0) approximately 45 mb x 1000. The difference between transport and hydrodynamic elliptic flow is established rather early during the evolution of the system, but the buildup of elliptic flow is insensitive to the choice of the initial (formation or thermalization) time in both models. 相似文献
19.
S. Shi 《Indian Journal of Physics》2011,85(7):1137-1141
Elliptic flow allows us to probe early dynamics in high energy nuclear collisions. The υ
2 result of charged hadrons and identified hadrons [1,2] from 200 GeV Au+Au collisions at RHIC suggest that the matter with
partonic collectivity and thermalization has been formed in central collisions. In this analysis, we present preliminary results
of υ
2 for K
S
0 and Λ from 200 GeV Cu+Cu collisions. The partonic collectivity and thermalization assumption are tested in smaller Cu+Cu system
comparing with those from Au+Au collisions. 相似文献
20.
A. Shabetai 《The European Physical Journal C - Particles and Fields》2007,49(1):169-175
Determining the degree of termalisation of the medium created in heavy ion collisions at RHIC remains highly debated. Elliptic
flow (v2) measurements at RHIC have already suggested the development of collectivity among partons before hadronization. If heavy
flavor hadrons flow with the light flavor hadrons, this indicates frequent interactions between the light (u, d ,s) and heavy
(c, b) quarks. Thus, thermalization of light quarks is likely to have been reached through partonic re-scattering. Experimentally
this can be probed by making a direct measurement of D-mesons v2 with sufficient precision at low transverse momentum. Using the Heavy Flavor Tracker (HFT) detector, the STAR experiment
at RHIC is proposing to both study this process and also to directly reconstruct charmed hadrons (D0, D+, Ds, ΛC, ...), using the displaced vertices of their decay products. The HFT is the first vertex detector to use a new and promising
CMOS active pixel sensor technology. It will allow to build a relatively fast, accurate and radiation tolerant detector, while
keeping the material budget low (∼0.3%X0 per layer). Detector design and physics performance simulations are presented. 相似文献