Jet quenching in glasma

TL;DR

This paper investigates how hard probes gain transverse momentum in the early glasma phase of heavy-ion collisions, calculating the jet quenching parameter and showing rapid growth of momentum broadening during pre-equilibrium.

Contribution

It introduces a method to compute the jet quenching parameter in an evolving glasma using a fifth-order expansion in proper time, highlighting the significance of pre-equilibrium effects.

Findings

Momentum broadening reaches several GeV^2/fm rapidly.

Pre-equilibrium phase contributes significantly to energy loss.

The calculated $\hat q$ evolves with proper time in the glasma.

Abstract

We discuss the transverse momentum broadening of hard probes traversing an evolving glasma, which is the earliest phase of the matter produced in relativistic heavy-ion collisions. The coefficient $\hat q$ is calculated using the Fokker-Planck equation, and an expansion in the proper time $\tau$ which is applied to describe the temporal evolution of the glasma. The correlators of the chromodynamic fields that determine the Fokker-Planck collision term, which in turn provides $\hat q$, are computed to fifth order in $\tau$. The momentum broadening is shown to rapidly grow in time and reach a magnitude of several ${\rm GeV^2/fm}$. We show that the transient pre-equilibrium phase provides a contribution to the energy loss of hard probes which is comparable to that of the long lasting, hydrodynamically evolving, equilibrium phase.