Probing nuclear liquid-gas phase transition with isospin correlations

TL;DR

This paper explores the behavior of isospin correlations and fluctuations of net-baryon numbers near the nuclear liquid-gas phase transition, revealing complex proton-neutron interactions and their impact on observable fluctuations.

Contribution

It introduces a detailed analysis of isospin correlations and higher-order susceptibilities near the nuclear liquid-gas critical point using the parity doublet model.

Findings

Net-proton fluctuations do not mirror total net-baryon fluctuations.

Proton-neutron correlations are significant and non-trivial.

Higher-order susceptibilities exhibit characteristic systematics near the critical point.

Abstract

We investigate the fluctuations of the net-baryon number near the critical point of the liquid-gas phase transition. We use the parity doublet model in the mean-field approximation fixed to the zero-temperature properties of nuclear matter to account for critical behavior. We explicitly calculate the fluctuations of the net-proton and net-neutron numbers as well as their correlations in the isospin-symmetric matter. We focus on the qualitative properties and systematics of the first- to fourth-order susceptibilities and their ratios. We demonstrate that the fluctuations of net-proton number do not reflect the total net-baryon number fluctuations in the vicinity of the nuclear liquid-gas phase transition. We also study the behavior of the baryon and proton number factorial cumulants. We highlight the importance of the non-trivial correlations between protons and neutrons.