Pre-Equilibrium Evolution of Conserved Charges with ICCING Initial Conditions

TL;DR

This paper extends a pre-equilibrium model to include conserved charges using Green's functions, improving initial state modeling in heavy-ion collision simulations.

Contribution

It introduces a method to incorporate conserved charges into the ICCING initial condition algorithm via Green's functions in the relaxation time approximation.

Findings

Charge geometries are altered by the new method.

The approach is applicable to central and mid-central collisions.

Green's functions effectively propagate conserved charges in pre-equilibrium phase.

Abstract

Heavy-ion collisions can be well described through relativistic viscous hydrodynamics, but questions still remain when hydrodynamics is applicable because the initial state may begin very far-from-equilibrium. Thus, a pre-equilibrium evolution phase is used to bridge the gap between the initial state and hydrodynamics. K$\phi$MP$\phi$ST is one such pre-equilibrium model that propagates the energy-momentum tensor by decomposing it into the background and fluctuations around that background, whose evolution is captured by Green's functions. We extend this formalism to include conserved charges and calculate the corresponding non-equilibrium Green's functions in the relaxation time approximation. The ICCING algorithm initializes conserved charges in the initial state by sampling $g \rightarrow q\bar{q}$ splitting probabilities and is, thus, perfectly positioned to implement Green's functions for charge propagation. We show that this method alters the initial state charge geometries and is applicable in central to mid-central collisions.