APS : Ballistic diffusion of heavy quarks in the early stage of relativistic heavy ion collisions at RHIC and the LHC

Liu, Jun-Hong; Ruggieri, Marco; Das, Santosh K.; Greco, Vincenzo

doi:10.1103/PhysRevD.103.034029

Article
Report number	arXiv:2011.05818
Title	Ballistic diffusion of heavy quarks in the early stage of relativistic heavy ion collisions at RHIC and the LHC
Author(s)	Liu, Jun-Hong (Lanzhou U. (main)) ; Das, Santosh K. (Indian Inst. Tech. Goa) ; Greco, Vincenzo (Catania U. ; INFN, Catania) ; Ruggieri, Marco (Lanzhou U. (main))
Publication	2021-02-27
Imprint	2020-11-11
Number of pages	12
Note	12 pages, 5 figures. In V2 we have corrected the presentation on how color charges are initialized in the code. A few clarifying comments have been added, to justify the use of the SU(2) color group, and to improve the presentation of the Langevin equation with the nonlocal dissipative kernel. V2 is the version accepted for publication on Phys. Rev. D
In:	Phys. Rev. D 103, 3 (2021) pp.034029
DOI	10.1103/PhysRevD.103.034029 10.1103/PhysRevD.103.034029 (publication)
Subject category	nucl-th ; Nuclear Physics - Theory ; hep-ph ; Particle Physics - Phenomenology
Accelerator/Facility, Experiment	BNL RHIC CERN LHC
Abstract	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 (Ev-Glasma), that is responsible of the energy loss via polarization of the medium. We compute the transverse momentum broadening, $\sigma_p$, of charm in the pre-thermalization 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 pre-thermalization stage. The study is completed by the calculation of coordinate spreading, $\sigma_x$, and by a comparison with Langevin dynamics. $\sigma_p$ in Ev-Glasma overshoots the result of standard Langevin dynamics at the end of the pre-hydro 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 pre-hydro stage shows that the charm quark in the Ev-Glasma is in the regime of ballistic diffusion.
Copyright/License	preprint: (License: CC0 1.0) publication: © 2021-2024 authors CC-BY-4.0

$Color online. Distribution function, at $t=0.2$ fm/c (blue lines), $t=0.6$ fm/c (orange lines) and at $t=1$ fm/c (green lines); the solid lines correspond to calculations with the color current while the dashed line to those without the current. Initial momentum is $p_0=0.5$ GeV in the upper panel and $p_0=5$ GeV in the lower panel. Calculations correspond to $\alpha_s=0.3$.$ $Color online. Distribution function, at $t=0.2$ fm/c (blue lines), $t=0.6$ fm/c (orange lines) and at $t=1$ fm/c (green lines); the solid lines correspond to calculations with the color current while the dashed line to those without the current. Initial momentum is $p_0=0.5$ GeV in the upper panel and $p_0=5$ GeV in the lower panel. Calculations correspond to $\alpha_s=0.3$.$ $Color online. Time evolution of $\sigma_p$ of charm quarks with different initial momenta. Solid lines correspond to the calculations with the color current, dashed lines stand for the results without color current. In the lower panel we zoom in the early time region for the case $p_0=0.5$ GeV to remark the nonlinear behavior of $\sigma_p(t)$.$ Show more plots

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