Initial energy density and gluon distribution from the Glasma in heavy-ion collisions

TL;DR

This paper estimates the initial energy density and gluon distribution in heavy-ion collisions using classical field models, providing insights into early-time dynamics and matching experimental data at RHIC energies.

Contribution

It introduces a method to decompose energy density in the McLerran-Venugopalan model and explores free-field and nonlinear evolution effects on the gluon distribution.

Findings

Numerical results align with empirical values at RHIC energies.

Free-field evolution is justified by ultraviolet mode dominance.

Inclusion of nonlinear terms improves the model accuracy.

Abstract

We estimate the energy density and the gluon distribution associated with the classical fields describing the early-time dynamics of the heavy-ion collisions. We first decompose the energy density into the momentum components exactly in the McLerran-Venugopalan model, with the use of the Wilson line correlators. Then we evolve the energy density with the free-field equation, which is justified by the dominance of the ultraviolet modes near the collision point. We also discuss the improvement with inclusion of nonlinear terms into the time evolution. Our numerical results at RHIC energy are fairly consistent with the empirical values.