部分子相互作用与√sNN=130GeV Au+Au碰撞中两粒子的横向动量关联

采用蒙特卡罗模型AMPT研究了\sqrt{s_{_{\rm NN}}}=130GeV Au+Au碰撞中部分子相互作用对两粒子横向动量关联的影响, 结果表明部分子相互作用 对两粒子的横向动量关联有重要的贡献. 还计算了AMPT模型中\sqrt{s_{_{\rm NN}}}=130GeV Au+Au碰撞的两粒子横向动量关联与碰撞对心性的依赖关系并与来自STAR的实验数据进行了比较,发现AMPT的理论预言很好地符合实验数据.     

部分子相互作用与√SNN=130GeV Au+Au碰撞中两粒子的横向动量关联

采用蒙特卡罗模型AMPT研究了√SNN=130GeV Au Au碰撞中部分子相互作用对两粒子横向动量关联的影响,结果表明部分子相互作用对两粒子的横向动量关联有重要的贡献.还计算了AMPT模型中√SNN=130GeV Au Au碰撞的两粒子横向动量关联与碰撞对心性的依赖关系并与来自STAR的实验数据进行了比较,发现AMPT的理论预言很好地符合实验数据.     

Pseudorapidity distribution of multiplicity in Au Au collisions at (S_(NN))~(1/2)=200 GeV

Using the Glauber model,we discuss the number of binary nucleon-nucleon collisions in heavy-ion collisions.Based on the latter,after considering the effect of energy loss of the nucleons in multiple colli- sions,we derive the pseudorapidity distribution of the multiplicity as a function of the impact parameter in nucleus-nucleus collisions.Using this,we analyze the experimental measurements carried out by the BRAHMS Collaboration in Au Au collisions at Pseudorapidity distribution of multiplicity in Au Au collisions at (S_(NN))~(1/2)=200 GeV)=200 GeV.The results are in good agreement with the experi- mental observations.     

RHIC能区Au+Au碰撞中HBT关联参数分析

利用相对论量子分子动力学模型RQMD,对RHIC能区s=200GeV/u Au+Au碰撞进行了2π干涉学分析,并讨论了HBT半径参数对横动量的依赖关系.研究表明,两粒子关联函数能够给出碰撞源在冻结时刻的时空拓扑信息,HBT半径参数能够较好地反映源的尺度和形状,但其对横动量的依赖关系并不能直接反映源的压缩性质,而是对粒子产生时源的空间–动量关联程度更为敏感.     

ee0A GeV S+Au反应中光子产生的低横动量增强

用建立在LUND弦模型特别是PYTHIA事件产生器基础上的描写极端相对论性核一核碰撞的强子和弦级联模型—JPCIAE研究了入射能量为200A GeV的S+ Au中心碰撞中光子产生.模型同时考虑了部分子QCD散射过程、强子末态相互作用以及强子衰变等光子产生反应道并作了协调处理.JPCIAE模型计算结果很好再现了WA93实验数据所呈现的低横动量增强效应.     

200A GeV S+Au反应中光子产生的低横动量增强

用建立在LUND弦模型特别是PYTHIA事件产生器基础上的描写极端相对论性核-核碰撞的强子和弦级联模型--JPCIAE研究了入射能量为200A GeV的S+Au中心碰撞中光子产生.模型同时考虑了部分子QCD散射过程、强子末态相互作用以及强子衰变等光子产生反应道并作了协调处理.JPCIAE模型计算结果很好再现了WA93实验数据所呈现的低横动量增强效应.     

基于关联度的高阶集合流关联分析方法

基于关联度概念,建立了可以分别检测高阶集合流的方位角关联、横向动量模关联和横向关联的新方法.采用新方法分别分析了1.2A GeV Ar+BaI₂碰撞的Bevalac流光室4π实验事件中末态粒子分布的方位角关联与粒子横向动量模的关联对高阶集合流关联的贡献.研究表明:对于这组碰撞实验,末态粒子分布的方位角关联相对横向动量模的关联在高阶集合流关联中起主要作用;末态粒子横向动量模的关联不但可以使粒子群高阶关联的强度有所增加,而且还为在更为狭窄的区间上确定集合流集体性的范围提供了重要信息.     

UrQMD模型中对质心能量7.7～62.4GeV下正反粒子椭圆流的差异研究（英文）

利用UrQMD-3.3p1模型模拟了在质心能量(~sNN)~(1/2)=7.7,11.5,19.6,27,39和62.4GeV的Au+Au碰撞,在中心快度区域分析了质子,π+,K+以及它们相应的反粒子的椭圆流。分析了粒子与相应的反粒子的v2差值随横动量pT的变化。分析结果表明,在UrQMD模型中在整个BES能区K-的v2值大于K+的。在能区7.7～62.4GeVπ+和π-的v2(pT)值几乎相同。然而实验上在低能区7.7,11.5和19.6GeV,在所考察的pT值范围内v2(π-)大于v2(π+)。能清楚看到在UrQMD模型中在整个BES能区反质子的v2大于质子的,这与实验结果相反。理论结果与实验数据相反,表明我们还需要不断深化对重离子碰撞的强耦合性和输运过程的非平衡性的理解。     

相对论重离子碰撞中集合流的横向运动关联

本文对1.2AGeV Ar+BaI₂和2.1 AGeV Ne+NaF碰撞的Bevalac流光室4π实验数据进行了集合流横向运动关联特性的研究.研究表明,末态粒子的横向运动不仅存在粒子分布的方位角关联,而且还存在横向动量模的关联;Ar+BaI₂碰撞实验中粒子分布的方位角关联、横向动量模关联和横向运动关联都分别强于Ne+NaF碰撞实验中相对应的各种关联;对于这两组碰撞实验,粒子分布的方位角关联相对横向动量模关联在横向运动关联中起着主要作用.     

Partonic interactions and two particle transverse momentum correlations in Au + Au collisions at √sNN=130GeV

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.     

Simulation of energy scan of pion interferometry in central Au+Au collisions at relativistic energies

We present a systematic analysis of two-pion interferometry for the central Au+Au collisions at √s_NN=3, 5, 7, 11, 17, 27, 39, 62, 130 and 200 GeV/c with the help of a multiphase transport (AMPT) model. Emission source-size radius parameters R_long, R_out, R_side and the chaotic parameter λ are extracted and compared with the experimental data. Transverse momentum and azimuthal angle dependencies of the HBT radii are also discussed for central Au+Au collisions at 200 GeV/c. The results show that the HBT radii in central collisions do not change much above 7 GeV/c. For central collisions at 200 GeV/c, the radii decrease with the increasing of transverse momentum p_T but are not sensitive to the azimuthal angle. These results provide a theoretical reference for the energy scan program of the RHIC-STAR experiment.     

Evidence from d+Au measurements for final-state suppression of high-p(T) hadrons in Au+Au collisions at RHIC

We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au collisions at sqrt[s(NN)]=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.     

System size and centrality dependence of charged hadron transverse momentum spectra in Au + Au and Cu + Cu collisions at square root of SNN = 62.4 and 200 GeV

We present transverse momentum distributions of charged hadrons produced in Cu + Cu collisions at square root of SNN = 62.4 and 200 GeV. The spectra are measured for transverse momenta of 0.25 < pT < 5.0 GeV/c at square root of SNN = 62.4 GeV and 0.25 < pT < 7.0 GeV/c at square root of SNN = 200 GeV, in a pseudorapidity range of 0.2 < eta < 1.4. The nuclear modification factor R(AA) is calculated relative to p + p data at both collision energies as a function of collision centrality. At a given collision energy and fractional cross section, R(AA) is observed to be systematically larger in Cu + Cu collisions compared to Au + Au. However, for the same number of participating nucleons, R(AA) is essentially the same in both systems over the measured range of pT, in spite of the significantly different geometries of the Cu + Cu and Au + Au systems.     

Transverse-mass dependence of two-pion correlations in Au+Au collisions at square root[s(NN)] = 130 GeV

Two-pion correlations in square root[s(NN)] = 130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k(T) by the PHENIX experiment at RHIC. The k(T) dependent transverse radii are similar to results from heavy-ion collisions at square root[s(NN)] = 4.1, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R(out)/R(side)) is consistent with unity and independent of k(T).     

Centrality dependence of pT spectra for identified hadrons in Au+Au and Cu+Cu collisions at √SNN=200 GeV

The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at √SNN=200GeV is systematically studied in a quark combination model.The pT spectra of π±,K±,P(p-)and A(A)in different centrality bins and the nuclear modification factors(Rcp)for these hadrons are calculated.The centrality dependence of the average collective transverse velocity(β(r)) for the hot and dense quark matter is obtained in Au+An collisions,and it is applied to a relative smaller Cu+Cu collision system.The centrality dependence of pT spectra and the Rcp for π0,K0/s and A in Cu+Cu collisions at √SNN=200 GeV are well described.The results show that(β(r))is only a function of the number of participants Npart and it is independent of the collision system.     

Pseudorapidity dependence of short-range correlations from a multi-phase transport model

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.     

Azimuthal anisotropy and correlations in the hard scattering regime at RHIC

Azimuthal anisotropy (v(2)) and two-particle angular correlations of high p(T) charged hadrons have been measured in Au+Au collisions at sqrt[s(NN)]=130 GeV for transverse momenta up to 6 GeV/c, where hard processes are expected to contribute significantly. The two-particle angular correlations exhibit elliptic flow and a structure suggestive of fragmentation of high p(T) partons. The monotonic rise of v(2)(p(T)) for p(T)<2 GeV/c is consistent with collective hydrodynamical flow calculations. At p(T)>3 GeV/c, a saturation of v(2) is observed which persists up to p(T)=6 GeV/c.     

Centrality dependence of high-p(T) hadron suppression in Au+Au collisions at sqrt[s(NN)]=130 GeV

Inclusive transverse momentum distributions of charged hadrons within 0.2相似文献   

在RHIC-PHENIX中、(√SNN)=200GeV Au+Au碰撞中直接光子的椭圆流测量

Azimuthal anisotropy of direct photon is measured in (√SNN)=200GeV Au Au collisions at RHICPHENIX. Direct photon is one of the most effective probes to study properties of hot dence medium at initial state (also QGP state) of heavy ion collisions because photons almost do not interact strongly with any other particles caused by its long mean free path and they keep their conditions when they are created. Within statistical and systematic errors, the elliptic flow parameter (v2) of direct photon is consistent with zero.Direct photon v2 is estimated by hadron decay photon contamination are subtracted from inclusive photon v2 in intermediate to high transverse momentum (pT) region (0 to 10GeV/c) for 3 centrality selections (20% steps) and minimum bias.