基于RHIC-STAR集体流纵向涨落的能量依赖性研究

集体流作为表征相对论重离子碰撞中夸克胶子等离子体(QGP)物质产生的重要探针，一直被广泛研究。以往的集体流测量更多局限于横平面，并假定集体流是洛伦兹不变量。近来的实验测量与理论计算均表明集体流的纵向涨落会导致集体流在长程关联中会发生退关联效应。这种集体流退关联效应清晰表明了集体流不再是洛伦兹不变量。最近提出的因式分解系数比这一实验可观测量，可以具体量化集体流退关联的强度大小。本项目将依托RHIC-STAR实验精确测量金核-金核54.4GeV能区的集体流退关联，通过系统比较200GeV，54.4GeV和27GeV这三个能区的集体流退关联来研究其能量依赖性。这有助于全面理解集体流退关联的能量依赖性，对于更好地理解集体流退关联的产生机制和相对论重离子碰撞的三维时空演化有重要科学意义。

Collective flow has been widely studied as an important probe to characterize the production of quark gluon plasma in relativistic heavy ion collisions. The previous flow measurements are mostly focusing on the transverse plane, which assumes flow is Lorentz boost-invariant. It is until recently both experimental measurements and theoretical calculations suggest longitudinal flow fluctuation will cause flow decorrelation in the long range correlation. Such flow decorrelation implies flow is non-boost-invariant. An experiment observable, factorization ratio rn, is proposed to quantify the flow decorrelation effect. In this project, we will have a precise measurement of flow decorrelation in Au+Au 54.4GeV from RHIC-STAR. The results will compared with Au+Au 200GeV and 27GeV with beam rapidity scaling, which will help us better understand the energy dependence mechanism of flow decorrelation. It will also help to constrain the initial condition along longitudinal direction and help understand the longitudinal evolution of the fireball.