Jet Momentum Broadening in Viscous QCD Matter: A Moment Expansion Approach

TL;DR

This paper develops a moment expansion method within QCD kinetic theory to connect jet momentum broadening with viscous hydrodynamics, enabling more accurate modeling of jet-medium interactions in heavy-ion collisions.

Contribution

It introduces a moment expansion approach to relate jet broadening to shear-stress tensors, bridging kinetic theory and viscous hydrodynamics in QCD.

Findings

Computed the leading near-equilibrium contribution to jet broadening tensor.

Established a direct mapping from shear-stress to jet broadening corrections.

Demonstrated the method's potential for event-by-event heavy-ion collision simulations.

Abstract

We formulate out-of-equilibrium jet momentum broadening in QCD effective kinetic theory through a moment expansion of the medium distribution function, a method traditionally used to derive relativistic viscous hydrodynamics from kinetic theory. We explicitly compute the leading near-equilibrium contribution to the spatial jet broadening tensor $\hat q^{ij}$ within the 14-moment approximation, and show that it is controlled by the medium shear-stress tensor. This provides a direct map from QCD effective kinetic theory to event-by-event viscous hydrodynamic simulations, converting local shear-stress fields into anisotropic corrections to jet broadening in heavy-ion collisions.