We study the diffusion of charm quarks in the early stage of high energy nuclear collisions at the RHIC and the LHC. The main novelty of the present study is the introduction of the color current carried by the heavy quarks that propagate in the evolving glasma (EG), which is responsible of the energy loss via polarization of the medium. We compute the transverse momentum broadening, ${\sigma }_p$, of charm in the prethermalization stage, and the impact of the diffusion on the nuclear modification factor in nucleus-nucleus collisions. The net effect of energy loss is marginal in the prethermalization stage. The study is completed by the calculation of coordinate spreading, ${\sigma }_x$, and by a comparison with Langevin dynamics. ${\sigma }_p$ in EG overshoots the result of standard Langevin dynamics at the end of the prehydro regime. We interpret this as a result of memory of the color force acting on the charm quarks that implies ${\sigma }_p\propto t^2$. Moreover, ${\sigma }_x\propto t^2$ in the prehydro stage shows that the charm quark in the EG is in the regime of ballistic diffusion.

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相对论重离子碰撞在RHIC和LHC早期的重夸克弹道扩散

我们研究了RHIC和LHC在高能核碰撞早期的魅力夸克的扩散。本研究的主要新颖之处是引入了重夸克所携带的色电流，这些夸克在不断发展的玻璃质（EG）中传播，这是通过介质极化导致能量损失的原因。我们计算横向动量展宽，${\sigma }_p$，预热阶段的魅力，扩散对核-核碰撞中核修饰因子的影响。能量损失的净效应在预热阶段是微不足道的。该研究是通过计算坐标展开来完成的，${\sigma }_X$，并与Langevin动力学进行比较。 ${\sigma }_p$EG在预加氢过程结束时超过了标准Langevin动力学的结果。我们将其解释为记忆作用在夸克上的色力的结果，这暗示了${\sigma }_p\propto {Ť}^{\mathrm{2个}}$。而且，${\sigma }_X\propto {Ť}^{\mathrm{2个}}$ 在预加氢阶段，表明EG中的夸克处于弹道扩散状态。