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 s_NN=200GeV Au+Au collisions at RHIC-PHENIX. 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 (p_T) region (0 to 10GeV/c) for 3 centrality selections (20% steps) and minimum bias.     

在RHIC-PHENIX中(s_(NN))~(1/2)=200GeV Au Au碰撞中直接光子的椭圆流测量(英文)

Azimuthal anisotropy of direct photon is measured in S_(NN)~(1/2)=200GeV Au Au collisions at RHIC- PHENIX.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 axe created.Within statistical and systematic errors,the elliptic flow parameter(v_2)of direct photon is consistent with zero. Direct photon v_2 is estimated by hadron decay photon contamination are subtracted from inclusive photon v_2 in intermediate to high transverse momentum(p_T)region(0 to 10GeV/c)for 3 centrality selections(20% steps)and minimum bias.     

超相对论Au+Au碰撞中椭圆流的时间依赖

用相对论量子分子动力学(RQMD)模型模拟了质心系束能量为s_NN=200GeV的Au+Au非对心碰撞, 研究了椭圆流对末态粒子冻出时间的关系. 研究了在不同的阶段, 椭圆流对末态粒子位置的关系. 结果表明椭圆流随冻出时间的单调递减, 椭圆流对横向半径的关系随冻出时间发生变化. 用压力梯度对所得结果进行了分析. 径向速度用来表征压力梯度.     

200GeV AuAu碰撞中前快度区的微分椭圆流

Identified particle elliptic flow results are presented for the Au+Au reaction at s_NN=200GeV as a function of transverse momentum and pseudorapidity. Data at pseudorapidities η≈0,1, and 3.4 were obtained using the two BRAHMS spectrometers. Differential v₂ (η,p_t) values for a given particle type are found to be essentially constant over the covered pseudorapidity range, in contrast to the integral v₂ values which have previously been observed to decrease at forward rapidities. A softening of the particle spectra at forward angles is found to account for at least part of the integral v₂ falloff. The data are found to be consistent with existing constituent quark scaling systematics.     

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.     

RHIC能区Au+Au碰撞中椭圆流的横半径依赖

用RQMD模型模拟了质心系束能量为s_NN=200GeV的Au+Au非对心碰撞, 研究了椭圆流对末态粒子冻出位置的关系. 研究表明, 随着冻出半径的增加, 椭圆流逐渐增强, 在源的初始表面处达到最大值, 随着冻出半径的继续增加, 椭圆流逐渐减小. 椭圆流的这种变化趋势反映了随着半径的增加, 压力梯度在各个方向上不同的变化. 本文提出了利用平均径向速度分析压力梯度的方法.     

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.     

Au+Au重离子碰撞中5~200 GeV碰撞能量下的温度涨落与比热(英文)

使用多相输运（AMPT）模型来研究相对论重离子碰撞中强子物质的比热（C_V）与对撞能量的关系以及温度的高阶涨落,并将之与文献[PhysRevC.94.044901]实验数据的比热结果进行了比较。对经历相变的系统,比热（C_V）作为表征系统状态方程的热力学量,其值预期在临界点发散。而温度的高阶涨落对相变敏感,比热（CV）和温度的高阶涨落都是适于探测QCD相变和临界点的敏感探针。通过逐个事例的平均横动量（<p_T>）来提取有效温度T_eff,再通过粒子的有效温度T_eff的分布提取出了相应粒子的热容。通过有效温度（T_eff）的分布的高阶矩来计算温度的高阶涨落。发现AMPT模型中比热和温度的高阶矩都随温度单调递减。同时还发现在低碰撞能量时,实验数据的比热结果有随能量增加而有一个急速下降,与AMPT模型的走势显著不同。AMPT模型中没有QCD临界点,提供了一个无临界点的参考背景。AMPT模型的计算结果可与实验结果比较作为实验上寻找QCD临界点的参考。     

Measurements of higher order flow harmonics in Au+Au collisions at √s(NN)=200 GeV

Flow coefficients ν(n) for n=2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at √s(NN)=200 GeV, are measured relative to event planes Ψ(n), determined at large rapidity. We report ν(n) as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The ν(n) are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted shear viscosity to entropy density ratio η/s.     

RHIC能区Au+Au碰撞中集合径向流的研究

利用相对论量子分子动力学模型RQMD,对RHIC能区s=200A GeV Au+Au碰撞的集体膨胀效应进行了研究,对散射粒子的横质量谱进行了分析.研究表明,在RHIC能区的重离子反应中存在有强的集合径向流.对单粒子谱的拟合结果给出Au+Au的源冻结温度为160MeV,平均径向流速度为0.6c.     

Identified hadron compositions in p+p and Au+Au collisions at high transverse momenta at √S(NN)=200 GeV

We report transverse momentum (p(T)≤15 GeV/c) spectra of π(±), K(±), p, p[over ˉ], K(S)(0), and ρ(0) at midrapidity in p+p and Au+Au collisions at √S(NN)=200 GeV. Perturbative QCD calculations are consistent with π(±) spectra in p+p collisions but do not reproduce K and p(p[over ˉ]) spectra. The observed decreasing antiparticle-to-particle ratios with increasing p(T) provide experimental evidence for varying quark and gluon jet contributions to high-p(T) hadron yields. The relative hadron abundances in Au+Au at p(T)?8 GeV/c are measured to be similar to the p+p results, despite the expected Casimir effect for parton energy loss.     

RHIC能区Au+Au碰撞中带电粒子直接流与超子整体极化的计算与分析

非对心的相对论重离子碰撞中,不参与碰撞的核子会对参与碰撞的核子产生纵向拖拽,形成一个相对于纵向倾斜的夸克胶子等离子体(QGP)火球.同时,对撞的原子核可将巨大的轨道角动量沉积于QGP中,使其中的部分子沿系统总角动量方向发生自旋极化.在光学Glauber模型基础上,本文构建了倾斜的三维QGP初态条件,并结合3+1维黏滞流体力学模型CLVisc,研究了重离子碰撞的末态带电粒子的直接流和Λ/■超子的整体极化.计算表明,倾斜的初态条件与流体力学模型的结合能够较好地描述RHIC-STAR实验上观测到的直接流与超子整体自旋极化的数据.这为人们利用这些观测量进一步约束重离子碰撞产生的核物质的初始几何与运动学状态提供了理论依据.     

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.     

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.     

Suppression of back-to-back hadron pairs at forward rapidity in d+Au collisions at √s(NN)=200 GeV

Back-to-back hadron pair yields in d+Au and p+p collisions at √s(NN)=200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p(T), and η points to cold nuclear matter effects arising at high parton densities.     

Λ-超子在RHIC的Au+Au碰撞中的整体极化

We present the Λ-hyperon global polarization in Au+Au collisions at s_NN=62GeV and 200GeV measured with the STAR detector at RHIC. The observed Λ-hyperon global polarization is consistent with zero, what is in agreement with recent measurements of Λ global polarization, as well as φ(1020) and K^*0(892) vector mesons spin alignment with respect to the reaction plane. The possible dependence of the global polarization on relative azimuthal angle between the orbital momentum of the system and the hyperon 3-momentum is discussed. The corresponding systematic uncertainty due to detector acceptance is found to be less than 20%.     

s~(1/2)=630GeV pp碰撞中微喷注的新分析

根据喷注判定的圆锥法来判断喷注，重新分析了ＵＡ１－１９８５年的６３０ＧｅＶ非单衍ｐｐ碰撞实验数据。分析发现对事件样本，单事件平均横动量ｐ与多重数ｎ是正关联的，而对喷注事件子样本则是负关联的；分析了微喷注产生嵉墓亓屯斯亓砻魑⑴缱⒉丛从诜侨砉毯透呓仔вΓ徊⑹状未邮笛樯瞎鄄獾轿⑴缱⒓浯嬖诖罂於燃涓裟谖蘖Ｗ拥氖吕治隽宋⑴缱⒉贝嬖诖罂於龋纾幔鸬募Ｏ蟆     

100MeV/uAu+Au对心碰撞中心集体流的发展

用量子分子动力学(QMD)模型研究了100MeV/u Au+Au对心碰撞的时间演化过程,着重研究了各种物理量随时间的发展如何趋向平衡及freeze-out的条件. 计算结果表明,对于100MeV/uAu+Au的对心碰撞,中心区的最高密度可以达到1.6ρ_0,在达到最大压缩后,体系开始膨胀,并发展成一个与粒子位置相关的中心集体流. 通过计算两粒子相对动量谱,可以将中心集体流与随机的热运动区分开来. 研究了中心集体流与状态方程的依赖关系.     

Azimuthal anisotropy of π⁰ production in Au+Au collisions at sqrt((s)NN)=200 GeV: path-length dependence of jet quenching and the role of initial geometry

We have measured the azimuthal anisotropy of π? production for 1相似文献