Far From Equilibrium Hydrodynamics and the Beam Energy Scan

TL;DR

This paper investigates how out-of-equilibrium effects in relativistic hydrodynamics influence the evolution of systems near the QCD critical point, highlighting the importance of initial conditions in heavy-ion collision modeling.

Contribution

It introduces a study of out-of-equilibrium initial conditions in hydrodynamic models with finite chemical potential, revealing their impact on the trajectory towards the QCD critical point.

Findings

Initial conditions are not unique for a given freeze-out point.

Initial baryon chemical potential can vary by about 350 MeV due to out-of-equilibrium effects.

Out-of-equilibrium effects significantly influence the search for the QCD critical point.

Abstract

The existence of hydrodynamic attractors in rapidly expanding relativistic systems has shed light on the success of relativistic hydrodynamics in describing heavy-ion collisions at zero chemical potential. As the search for the QCD critical point continues, it is important to investigate how out of equilibrium effects influence the trajectories on the QCD phase diagram. In this proceedings, we study a Bjorken expanding hydrodynamic system based on DMNR equations of motion with initial out of equilibrium effects and finite chemical potential in a system with a critical point. We find that the initial conditions are not unique for a specific freeze-out point, but rather the system can evolve to the same final state freeze-out point with a wide range of initial baryon chemical potential, $\mu_B$. For the same initial energy density and baryon density, depending on how far out of equilibrium the system begins, the initial $\mu_B$ can vary by $\Delta \mu_B\sim 350$ MeV. Our results indicate that knowledge of the out-of-equilibrium effects in the initial state provide vital information that influences the search for the QCD critical point.