Opacity dependence of transverse flow, pre-equilibrium and applicability of hydrodynamics in heavy-ion collisions

TL;DR

This paper investigates how opacity influences collective flow in heavy-ion collisions using kinetic theory, highlighting limitations of hydrodynamic models and proposing improvements for better accuracy.

Contribution

It provides a detailed analysis of opacity effects on flow and introduces modified simulation setups to enhance hydrodynamic model reliability.

Findings

Hydrodynamic models have shortcomings in describing opacity dependence.

Modified simulation setups improve hydrodynamic accuracy.

Kinetic theory offers a comprehensive understanding of flow in heavy-ion collisions.

Abstract

We evaluate the full opacity dependence of collective flow in high-energy heavy-ion collisions within a microscopic kinetic description based on the Boltzmann equation in the conformal relaxation time approximation. By comparing kinetic theory calculations to hydrodynamic and hybrid simulations for an average initial state, we point out shortcomings and inaccuracies of hydrodynamic models and present modified simulation setups to improve them.