Competition between diffusion and rapid expansion and its impact on critical fluctuations in heavy-ion collisions

TL;DR

This paper investigates how the interplay between medium expansion and diffusion affects critical net-baryon density fluctuations in heavy-ion collisions, influencing the interpretation of experimental data.

Contribution

It introduces a detailed analysis of the competition between diffusion and expansion and its effects on fluctuation observables during fireball evolution.

Findings

Diffusion and expansion competition alters fluctuation signals.

Different scenarios lead to varied cumulant behaviors.

Implications for interpreting heavy-ion collision data.

Abstract

We study the impact of the competition between the expansion of the medium created in heavy-ion collisions and its diffusive properties on the critical fluctuations of the net-baryon density. As the relaxation time of the fluctuations is connected with the diffusive properties, the latter determine the in- or out-of-equilibrium nature of the net-baryon density fluctuations during the fireball evolution. This may result in important consequences for the phenomenological interpretation of heavy-ion collision data. We study three possible situations that can occur as a result of the competition between diffusion and expansion and discuss the impact of this competition on the integrated second and fourth order cumulants of net-baryon density fluctuations at freeze-out in these situations.