论文标题
相对于PB-PB和XE-XE碰撞中的观众平面，带电颗粒的椭圆流动的椭圆流
Elliptic flow of charged particles at midrapidity relative to the spectator plane in Pb-Pb and Xe-Xe collisions
论文作者
论文摘要
椭圆流系数相对于观众中子定义的碰撞平面$ v_2 $ {$ v_2 $ {$ n {\ rm sp} $}的碰撞碰撞中的PB离子碰撞中的碰撞中心，每核核心 - 核子 - nucleon对中心能量$ \ sqrt $ \ sqrt { $ \ sqrt {s _ {\ rm nn}} $ = 5.44 TEV。结果是针对中心和横向动量的函数在中期产生的带电颗粒的结果。 $ v_2 $ {$ψ_{\ rm sp} $}之间的比率与使用四粒子相关性估计的椭圆流系数相对于参与者平面$ v_2 $ {4}，偏离统一的比率。该观察结果与Trento预测的相应偏心率比和初始状态波动的椭圆功率模型的相应偏心率的大小有很大不同，这些模型被调整为描述参与者平面各向异性。这些差异可以解释为中子观众平面和反应平面的去相关，这是由于碰撞核的残余物的破碎，这表明了初始状态波动的当前模型的不完整。除了最中心的碰撞外，所有比率$ v_2 $ {$ v_2 $ {$ v_2 $ {\ rm sp} $}/$ v_2 $ {4}的显着横向动量依赖性在除最中心的碰撞中都可以观察到，这可能有助于了解低和中间横向动量在最初的状态上有共同的起源。 The ratios of $v_2${$Ψ_{\rm SP}$} and $v_2${4} to the corresponding initial state eccentricities for Xe-Xe and Pb-Pb collisions at similar initial entropy density show a difference of $(7.0 \pm 0.9)$% with an additional variation of +1.8% when including RHIC data in the TRENTo parameter extraction.这些观察结果为扩展的夸克 - 杜伦等离子体的流体动力模型中的粘性效应提供了新的实验约束。
Measurements of the elliptic flow coefficient relative to the collision plane defined by the spectator neutrons $v_2${$Ψ_{\rm SP}$} in collisions of Pb ions at center-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}$=2.76 TeV and Xe ions at $\sqrt{s_{\rm NN}}$=5.44 TeV are reported. The results are presented for charged particles produced at midrapidity as a function of centrality and transverse momentum. The ratio between $v_2${$Ψ_{\rm SP}$} and the elliptic flow coefficient relative to the participant plane $v_2${4}, estimated using four-particle correlations, deviates by up to 20% from unity depending on centrality. This observation differs strongly from the magnitude of the corresponding eccentricity ratios predicted by the TRENTo and the elliptic power models of initial state fluctuations that are tuned to describe the participant plane anisotropies. The differences can be interpreted as a decorrelation of the neutron spectator plane and the reaction plane because of fragmentation of the remnants from the colliding nuclei, which points to an incompleteness of current models of initial state fluctuations. A significant transverse momentum dependence of the ratio $v_2${$Ψ_{\rm SP}$}/$v_2${4} is observed in all but the most central collisions, which may help to understand whether momentum anisotropies at low and intermediate transverse momentum have a common origin in initial state fluctuations. The ratios of $v_2${$Ψ_{\rm SP}$} and $v_2${4} to the corresponding initial state eccentricities for Xe-Xe and Pb-Pb collisions at similar initial entropy density show a difference of $(7.0 \pm 0.9)$% with an additional variation of +1.8% when including RHIC data in the TRENTo parameter extraction. These observations provide new experimental constraints for viscous effects in the hydrodynamic modeling of the expanding quark-gluon plasma.
