Jet quenching parameter in QCD kinetic theory

Abstract

We study the jet quenching parameter $\hat{q}$ in a non-equilibrium plasma using the QCD effective kinetic theory. We discuss subleading terms at large jet momentum p, show that our expression for $\hat{q}$ reproduces thermal results at small and large transverse momentum cutoffs for infinite p and construct an interpolation between these limits to be used in phenomenological applications. Using simple non-equilibrium distributions that model pertinent features of the bottom-up thermalization scenario, we analytically assess how anisotropy, under- or overoccupation affect the jet quenching parameter. Our work provides more details on the $\hat{q}$ formula used in our preceding work [arXiv:2303.12595] and sets the stage for further numerical studies of jet momentum broadening in the initial stages of heavy-ion collisions from QCD kinetic theory.

Comments: 34 pages, 10 figures, accepted for publication in PRD