Viscosities of the Baryon-Rich Quark-Gluon Plasma from Beam Energy Scan Data

TL;DR

This study uses Bayesian inference with (3+1)D hydrodynamics and hadronic transport to analyze RHIC Beam Energy Scan data, constraining QGP viscosities and initial state properties in baryon-rich conditions.

Contribution

First Bayesian inference analysis of (3+1)D heavy-ion collision dynamics and QGP viscosities using event-by-event simulations and RHIC data.

Findings

Baryon chemical potential-dependent shear viscosity constrained.

Bulk viscosity peaks around 19.6 GeV collision energy.

Insights into the speed of sound variations in QCD matter.

Abstract

This work presents the first Bayesian inference study of the (3+1)D dynamics of relativistic heavy-ion collisions and Quark-Gluon Plasma (QGP) viscosities using an event-by-event (3+1)D hydrodynamics + hadronic transport theoretical framework and data from the Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan program. Robust constraints on initial state nuclear stopping and the baryon chemical potential-dependent shear viscosity of the produced quantum chromodynamic (QCD) matter are obtained. The specific bulk viscosity of the QCD matter is found to exhibit a preferred maximum around $\sqrt{s_\mathrm{NN}} = 19.6$ GeV. This result allows for the alternative interpretation of a reduction (and/or increase) of the speed of sound relative to that of the employed lattice-QCD based equation of state (EOS) for net baryon chemical potential $\mu_B \sim 0.2\, (0.4)$ GeV.