Beam energy and system size dependence of heavy flavor production at STAR

We report the measurements of quarkonia (J/ψ and ψ(2S)) in heavyion collisions via the e+e− decay channel at midrapidity (|y| < 1) by the STAR experiment. The centrality and transverse momentum dependence of the yield ratio of ψ(2S) to J/ψ is measured for the first time in heavy-ion collisions at RHIC. These results, together with the new measurement of collision energy dependence of inclusive J/ψ suppression in Au+Au collisions, allow for a systematic study of the quarkonium production in the medium. In addition, we present the first measurement of J/ψ polarization in heavy-ion collisions at RHIC in both the Helicity and the Collins-Soper frames, which provides a new insight for studying the properties of the Quark-Gluon Plasma created in heavy-ion collisions.

我们报告了STAR实验通过正负电子衰变通道在中快度（|y| < 1）下对重离子碰撞中夸克偶素（J/ψ和ψ(2S)）的测量结果。在RHIC的重离子碰撞中首次测量了ψ(2S)与J/ψ产额比的中心度和横动量依赖性。这些结果，连同对金 - 金碰撞中包含性J/ψ压低的碰撞能量依赖性的新测量，使得能够对介质中夸克偶素的产生进行系统研究。此外，我们给出了在RHIC的重离子碰撞中J/ψ在螺旋度框架和柯林斯 - 索珀框架下极化的首次测量结果，这为研究重离子碰撞中产生的夸克 - 胶子等离子体的性质提供了新的视角。