Radiative heavy quark energy loss in an expanding viscous QCD plasma

TL;DR

This paper investigates how viscosity and expansion in a quark-gluon plasma affect the radiative energy loss of heavy quarks, using hydrodynamic models and nonequilibrium distribution functions.

Contribution

It introduces viscous corrections into the calculation of heavy quark energy loss in an expanding QCD plasma using relativistic hydrodynamics and compares different nonequilibrium models.

Findings

Viscous effects slightly increase heavy quark energy loss.

Expansion reduces energy loss compared to static medium.

The pattern of energy loss enhancement depends on the viscous correction model.

Abstract

We study viscous effects on heavy quark radiative energy loss in a dynamically screened medium with boost-invariant longitudinal expansion. We calculate, to first order in opacity, the energy loss by incorporating viscous corrections in the single-particle phase-space distribution function within relativistic dissipative hydrodynamics. We consider the Grad's 14-moment and the Chapman-Enskog-like methods for the nonequilibrium distribution functions. Our numerical results for the charm quark radiative energy loss show that, as compared to static fluid, an expanding ideal (nonviscous) fluid causes a much smaller energy loss. Viscosity in the evolution lead to somewhat enhanced energy loss which is insensitive to the underlying viscous hydrodynamic models used. Further inclusion of viscous correction induces larger energy loss, the magnitude and pattern of this enhancement crucially depend on the form of viscous corrections used.