Heavy quark drag and diffusion coefficients in the pre-hydrodynamic QCD plasma

TL;DR

This paper calculates heavy quark drag and diffusion coefficients in the early-stage QCD plasma using advanced kinetic theory, revealing their dependencies and providing estimations relevant for understanding quark thermalization in heavy-ion collisions.

Contribution

It introduces a comprehensive calculation of heavy quark transport coefficients in pre-hydrodynamic QCD plasma using state-of-the-art kinetic theory, including simple estimation formulas.

Findings

Time, momentum, and angular dependencies of coefficients are characterized.

Effects of isotropization and chemical equilibration are demonstrated.

Simple formulas for estimating coefficients at different couplings are provided.

Abstract

Kinetic and chemical equilibrations play important roles in the formation of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions (HICs). These processes further influence the production of hard and electromagnetic probes in HICs, in particular, the thermalization of heavy quarks, which are produced at an extremely early time before the formation of the QGP. We calculate the drag and diffusion coefficients of heavy quarks in the pre-hydrodynamic quantum chromodynamic (QCD) plasma with the state-of-the-art QCD effective kinetic theory (EKT) solver. We present the time, momentum, and angular dependencies of these coefficients for gluon and quark contributions separately, showing the effects of isotropization and chemical equilibration from the QCD plasma. We also provide a simple formula to estimate the heavy quark drag and diffusion coefficients, as well as its energy loss, within the pre-hydrodynamic plasma at different coupling strengths based on the attractor theory. We then discuss the validity of these estimations with leading-order calculations and leading-logarithmic rescaling factors.