Fluctuations near the liquid-gas and chiral phase transitions in hadronic matter

TL;DR

This paper studies fluctuations in net-baryon density near phase transitions in hadronic matter, revealing that negative susceptibilities signal proximity to the chiral critical point, with implications for heavy-ion collision experiments.

Contribution

It introduces a model using parity doublet Lagrangian to analyze baryon number fluctuations near chiral phase transitions, highlighting the behavior of susceptibilities.

Findings

Second-order susceptibility of positive-parity nucleons can become negative at chiral restoration.

Negative fluctuations indicate approaching the chiral critical point.

Results may help interpret net-proton fluctuation data in heavy-ion collisions.

Abstract

We investigate the fluctuations of the net-baryon number density in dense hadronic matter. Chiral dynamics is modeled via the parity doublet Lagrangian, and the mean-field approximation is employed to account for chiral criticality. We focus on the qualitative properties and systematics of the second-order susceptibility of the net-baryon number density for individual positive- and negative-parity nucleons whose masses become degenerate at the chiral restoration. It is shown that the second-order susceptibility of the positive-parity state can become negative when the chiral symmetry is restored, as a natural consequence of the unique relationship of the mass to the order parameter. Moreover, we find that such negative fluctuations are indicative of approaching the critical point on the chiral phase boundary. Our results may have consequences for the interpretation of the experimental data on net-proton fluctuations in heavy-ion collisions.