Vorticity-induced modifications of chemical freeze-out in heavy-ion collisions

TL;DR

This study explores how global rotation affects chemical freeze-out conditions and observables in heavy-ion collisions, revealing systematic shifts in freeze-out parameters and varying sensitivities of experimental measures.

Contribution

It introduces the first systematic analysis of rotational effects on freeze-out parameters and observables within the hadron resonance gas model.

Findings

Rotation shifts the freeze-out curve toward lower temperatures.

Particle yield ratios are sensitive to rotational effects.

Cumulant ratios are less affected by rotation.

Abstract

We investigate the influence of global rotation on the chemical freeze-out parameters in ultra-relativistic heavy-ion collisions. Within the framework of the hadron resonance gas (HRG) model, the freeze-out parameters are determined using commonly employed freeze-out criteria, namely the fixed energy per particle and the scaled entropy density, extended here to include rotational effects. We find that the presence of rotation leads to a systematic shift of the chemical freeze-out curve toward lower temperatures in the $T\text{--}\mu_B$ phase diagram. The behavior of the electric charge and strangeness chemical potentials in the presence of rotation is also analyzed, providing the first systematic study of their rotational dependence within the HRG framework. Furthermore, we examine the impact of rotation on experimentally relevant observables, including hadron yield ratios and susceptibility ratios of conserved charges. Our results show that while particle yield ratios exhibit noticeable sensitivity to rotation, the conventional cumulant ratios remain comparatively less affected. This indicates that hadronic yield ratios may provide a more suitable observable for estimating the magnitude of rotational effects generated in heavy-ion collisions.