Tomography of the Quark-Gluon-Plasma by Charm Quarks
Tomography of the Quark-Gluon-Plasma by Charm Quarks
复制标题
DOI：
10.1103/physrevc.92.014910
复制
发表时间：
2015-03
影响因子：
3.1
通讯作者：
T. Song;H. Berrehrah;D. Cabrera;J. Torres-Rincon;L. Tolos;W. Cassing;E. Bratkovskaya
中科院分区：
文献类型：
--
作者：
T. Song;H. Berrehrah;D. Cabrera;J. Torres-Rincon;L. Tolos;W. Cassing;E. Bratkovskaya
我们使用帕顿-强子-弦动力学 (PHSD) 输运方法研究超相对论重离子碰撞中的粲产生。初始粲夸克由 Pythia 事件生成器生成，该生成器经过调整以适应定序次前对数 (FONLL) 计算中粲夸克的横向动量谱和快速度分布。产生的粲夸克与离壳部分子一起散射在夸克-胶子等离子体 (QGP) 中，其质量和宽度由动态准粒子模型 (DQPM) 给出，该模型再现了热平衡中的晶格 QCD 状态方程。通过使用 DQPM 中的有效传播器和耦合器，以一致的方式计算相关横截面。接近相变的临界能量密度时，粲夸克根据横向动量通过聚结和/或分裂被强子化为 $D$ 介子。然后，强子化的 $D$ 介子与强子相中的各种强子相互作用，其横截面是通过具有重夸克自旋对称性的有效拉格朗日方法计算的。最后，将 PHSD 的核修正因子 $\rm R_{AA}$ 和 $D^0$ 介子的椭圆流 $v_2$ 与 STAR Collaboration 在 $\sqrt{s_{\rm NN}}$ =200 GeV 下 Au+Au 碰撞的实验数据进行比较。我们发现，在 PHSD 中，$D$ 介子在高 $p_T$ 时的能量损失主要归因于部分子散射，而 $\rm R_{AA}$ 与 $p_T$ 的实际形状反映了重夸克强子化场景，即聚结与碎裂。此外，强子重散射对于低 $p_T$ 处的 $\rm R_{AA}$ 很重要，并增强了 $D$-介子椭圆流 $v_2$。
We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM) which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross section are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into $D$ mesons through coalescence and/or fragmentation depending on transverse momentum. The hadronized $D$ mesons then interact with the various hadrons in the hadronic phase with cross sections calculated in an effective lagrangian approach with heavy-quark spin symmetry. Finally, the nuclear modification factor $\rm R_{AA}$ and the elliptic flow $v_2$ of $D^0$ mesons from PHSD are compared with the experimental data from the STAR Collaboration for Au+Au collisions at $\sqrt{s_{\rm NN}}$ =200 GeV. We find that in the PHSD the energy loss of $D$ mesons at high $p_T$ can be dominantly attributed to partonic scattering while the actual shape of $\rm R_{AA}$ versus $p_T$ reflects the heavy quark hadronization scenario, i.e. coalescence versus fragmentation. Also the hadronic rescattering is important for the $\rm R_{AA}$ at low $p_T$ and enhances the $D$-meson elliptic flow $v_2$.