Abstract

Two-particle correlations are powerful tools for studying the medium produced in heavy-ion collisions. In particular, two-particle transverse momentum correlations enable measurements of the collision dynamics sensitive to momentum currents. Their evolution with collision centrality, which is related to the system lifetime, provides information about the shear viscosity, \(\eta {\text{/}}s\), and the system relaxation time, \({{\tau }_{\pi }}\). We report on measurements of two-particle transverse momentum correlations as a function of centrality in Pb‒Pb collisions using the ALICE detector at the LHC. The centrality dependence of the near side peak of the correlation function, particularly its longitudinal width, provides information about the shear viscosity of the produced medium. The data are compared to predictions from selected Monte Carlo models. The charge independent momentum correlator exhibits a longitudinal broadening from peripheral to central collisions that is qualitatively consistent with expectations from a model with viscous effects. An interpretation of the observed broadening in the context of this model will be discussed.

中文翻译：

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$$ \ sqrt {{{{\ text {s}}} _ {{{\ text {NN}}}}}}的Pb–Pb碰撞中的两部分横向动量相关= 2.76 $$ TeV

摘要

两粒子关联是研究重离子碰撞产生的介质的强大工具。特别地，两粒子横向动量相关性使得能够测量对动量电流敏感的碰撞动力学。它们以碰撞中心为中心的演变与系统寿命有关，提供了有关剪切粘度\（\ eta {\ text {/}} s \）和系统弛豫时间\（{{\ tau} _ {\ pi}} \）。我们报告了在大型强子对撞机使用ALICE检测器测量作为Pb‒Pb碰撞中心性的两个粒子的横向动量相关性。相关函数近侧峰的中心性相关性，特别是其纵向宽度，提供了有关所生产介质的剪切粘度的信息。将数据与所选蒙特卡洛模型的预测结果进行比较。与电荷无关的动量相关器显示出从外围碰撞到中心碰撞的纵向加宽，其在质量上与具有粘性效应的模型的预期一致。将讨论在此模型的背景下观察到的扩展的解释。