Initialization of hydrodynamics in relativistic heavy ion collisions with an energy-momentum transport model

TL;DR

This paper investigates how different pre-thermal initial conditions, modeled via an energy-momentum transport approach, influence the early hydrodynamic evolution in relativistic heavy ion collisions, affecting flow and energy density distributions.

Contribution

It introduces a novel application of an energy-momentum transport model to study the impact of various initial states on hydrodynamic starting conditions in nuclear collisions.

Findings

Longitudinally squeezed initial states increase transverse flow and maximum energy density.

Results depend on relaxation time, equation of state, and initial energy density profile.

The model reliably generates both average and fluctuating initial conditions for simulations.

Abstract

A key ingredient of hydrodynamical modeling of relativistic heavy ion collisions is thermal initial conditions, an input that is the consequence of a pre-thermal dynamics which is not completely understood yet. In the paper we employ a recently developed energy-momentum transport model of the pre-thermal stage to study influence of the alternative initial states in nucleus-nucleus collisions on flow and energy density distributions of the matter at the starting time of hydrodynamics. In particular, the dependence of the results on isotropic and anisotropic initial states is analyzed. It is found that at the thermalization time the transverse flow is larger and the maximal energy density is higher for the longitudinally squeezed initial momentum distributions. The results are also sensitive to the relaxation time parameter, equation of state at the thermalization time, and transverse profile of initial energy density distribution: Gaussian approximation, Glauber Monte Carlo profiles, etc. Also, test results ensure that the numerical code based on the energy-momentum transport model is capable of providing both averaged and fluctuating initial conditions for the hydrodynamic simulations of relativistic nuclear collisions.