We study the relaxation time required for the alignment between the spin of a finite-mass quark/antiquark and the thermal vorticity, at finite temperature and baryon chemical potential, in the context of relativistic heavy-ion collisions. The relaxation time is computed as the inverse of the total reaction rate that in turn is obtained from the imaginary part of the quark/antiquark self-energy. We model the interaction between spin and thermal vorticity within the medium by means of a vertex coupling quarks and thermal gluons that, for a uniform temperature, is proportional to the global angular velocity and inversely proportional to the temperature. We use realistic estimates for the angular velocities for different collision energies and show that the effect of the quark mass is to reduce the relaxation times as compared to the massless quark case. Using these relaxation times we estimate the intrinsic quark and antiquark polarizations produced by the thermal vorticity. We conclude by pointing out that, in spite of the former being larger than the latter, it is still possible to understand recent results from the STAR Beam Energy Scan when accounting for the fact that only a portion of quarks/antiquarks come from the denser and thus thermalized region in the collision.
Dilepton Production in a Rotating Thermal Medium: The Rigid Rotation Approximation
Universidad del Valle（德利瓦列大学）；Pontificia Universidad Católica de Chile（智利天主教Pontificia大学）；Center for Nanotechnology and Advanced Materials CIEN-UC（纳米技术与先进材料中心CIEN-UC）
Longitudinal $Λ$ polarization as a competition between freeze-out geometry and elliptic flow in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36\,\mathrm{TeV}$
School of Mathematics and Physics, China University of Geosciences (Wuhan)（中国地质大学（武汉）数学与物理学院）；Institute of Physics and Technology, University of Bergen（卑尔根大学物理与技术研究所）
本研究通过 (3+1) 维流体动力学分析 48 个 Pb-Pb 初始态，发现纵向超子极化与冻结出射偏心率相关，提出紧凑关系描述其变化，并利用 ALICE 数据反演验证，表明纵向极化可约束解耦时的空间各向异性。
