Hydrodynamic Attractors, Initial State Energy, and Particle Production in Relativistic Nuclear Collisions.

Giuliano Giacalone,Sören Schlichting,Aleksas Mazeliauskas

doi:10.1103/physrevlett.123.262301

Abstract

We exploit the concept of hydrodynamic attractors to establish a macroscopic description of the early time out-of-equilibrium dynamics of high energy heavy-ion collisions. One direct consequence is a general relation between the initial state energy and the produced particle multiplicities measured in experiments. When combined with an abinitio model of energy deposition, the entropy production during the preequilibrium phase naturally explains the universal centrality dependence of the measured charged particle yields in nucleus-nucleus collisions. Further, we estimate the energy density of the far-from-equilibrium initial state and discuss how our results can be used to constrain nonequilibrium properties of the quark-gluon plasma.

Highlights

Theoretical Physics Department, CERN, CH-1211 Geneve 23, Switzerland and Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D-69120 Heidelberg, Germany
One outstanding discovery made in the field of heavy-ion collisions is that the system created about 1 fm=c (≈3 × 10−24 s) after the impact of two relativistic nuclei can be described as a deconfined plasma of quarks and gluons (QGP) with macroscopic properties of temperature and velocity [5,6,7,8]. Such “unreasonable effectiveness of hydrodynamics” in describing the violent expansion of the QGP droplets triggered a new research area in mathematical physics devoted to the study of hydrodynamic attractors that emerge in out-of-equilibrium systems experiencing very fast memory loss of initial conditions and exhibiting a universal approach toward thermal equilibrium [9,10]
In this Letter, we show that hydrodynamic attractors can be used to describe entropy production in relativistic nuclear collisions and to make robust estimates of initial

Summary

Introduction

Theoretical Physics Department, CERN, CH-1211 Geneve 23, Switzerland and Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D-69120 Heidelberg, Germany. When combined with an ab initio model of energy deposition, the entropy production during the preequilibrium phase naturally explains the universal centrality dependence of the measured charged particle yields in nucleus-nucleus collisions.

Results

Conclusion