Critical lensing and kurtosis near a critical point in the QCD phase diagram in and out-of-equilibrium

TL;DR

This paper investigates how the QCD critical point influences hydrodynamic trajectories and net-proton kurtosis, considering both equilibrium and out-of-equilibrium scenarios, revealing the impact of the critical region's size and shape on observable signals.

Contribution

It introduces a comprehensive analysis of the QCD critical point's lensing effect on hydrodynamics and kurtosis, incorporating critical behavior via the BEST EoS in both equilibrium and dynamical models.

Findings

Critical region's size and shape affect signal survival.

Both equilibrium and out-of-equilibrium conditions show lensing effects.

Hydrodynamic evolution influences net-proton kurtosis near the critical point.

Abstract

In this work, we study the lensing effect of the QCD critical point on hydrodynamic trajectories, and its consequences on the net-proton kurtosis $\kappa_4$. Including critical behavior by means of the BEST Collaboration equation of state (EoS), we first consider a scenario in equilibrium, then compare with hydrodynamic 0+1D simulations with Bjorken expansion, including both shear and bulk viscous terms. We find that, both in and out-of-equilibrium, the size and shape of the critical region directly affect if the signal will survive through the dynamical evolution.