Kinetic equilibration from a radiative transport

TL;DR

This paper investigates how kinetic equilibration occurs in the early stages of relativistic heavy ion collisions using a radiative transport model, highlighting the roles of thermalization, pressure anisotropy, and viscosity.

Contribution

It introduces a radiative transport model to study early kinetic equilibration, revealing the dominance of thermalization and the significance of viscosity during expansion.

Findings

Thermalization dominates over expansion with medium regulated cross sections.

Pressure anisotropy shows approximate alpha_s scaling with radiative processes.

Energy density approaches an asymptotic evolution slower than ideal hydro.

Abstract

Kinetic equilibration during the early stage of a relativistic heavy ion collision is studied using a radiative transport model. Thermalization is found to dominate over expansion with medium regulated cross sections. Pressure anisotropy shows an approximate alpha_s scaling when radiative processes are included. It approaches an asymptotic time evolution on a time scale of 1 to 2 fm/c. Energy density is also found to approach an asymptotic time evolution that decreases slower than the ideal hydro evolution. These observations indicate that viscosity is important during the early longitudinal expansion phase of a relativistic heavy ion collision.