Interplay between chiral dynamics and repulsive interactions

TL;DR

This paper explores how chiral dynamics and repulsive interactions influence net-baryon number fluctuations near the chiral crossover, highlighting the importance of self-consistent modeling for accurate predictions.

Contribution

It demonstrates that higher-order cumulants near the chiral transition are primarily driven by chiral criticality, not just repulsive interactions, emphasizing the need for combined modeling approaches.

Findings

Higher-order cumulants are suppressed near the chiral transition due to repulsive interactions.

Chiral criticality dominates the properties of cumulants near the crossover.

Simple phenomenological models cannot fully reproduce lattice QCD results for cumulants.

Abstract

We investigate fluctuations of the net-baryon number density in hot hadronic matter. We discuss the interplay between chiral dynamics and repulsive interactions and their influence on the properties of these fluctuations near the chiral crossover. The chiral dynamics is modeled by the parity doublet Lagrangian that incorporates the attractive and repulsive interactions mediated via the exchange of scalar and vector mesons, respectively. The mean-field approximation is employed to account for chiral criticality. We focus on the properties and systematics of the cumulants of the net-baryon number density up to the sixth order. It is shown that the higher-order cumulants exhibit a substantial suppression in the vicinity of the chiral phase transition due to the presence of repulsive interactions. We find, however, that the characteristic properties of cumulants near the chiral crossover observed in lattice QCD results are entirely linked to the critical chiral dynamics and, in general, cannot be reproduced in phenomenological models, which account only for effective repulsive interactions via excluded-volume corrections or van-der-Waals type interactions. Consequently, a description of the higher-order cumulants of the net-baryon density in the chiral crossover requires a self-consistent treatment of the chiral in-medium effects and repulsive interactions.