Proton-neutron correlations in baryon-number fluctuations near the liquid-gas transition

TL;DR

This paper investigates how proton-neutron correlations influence baryon-number fluctuations near the nuclear liquid-gas transition, revealing their significant role in interpreting fluctuation measurements in isospin-symmetric matter.

Contribution

It introduces a detailed analysis of proton-neutron correlations affecting net-baryon and net-proton fluctuations near the liquid-gas phase transition using the parity doublet model.

Findings

Proton-neutron correlations cause qualitative differences between net-proton and net-baryon fluctuations.

Differences in factorial cumulants are governed by proton-neutron correlations.

Interaction-driven correlations are crucial for interpreting fluctuation measurements near the critical endpoint.

Abstract

We study net-baryon number density fluctuations in isospin-symmetric matter near the nuclear liquid-gas phase transition using the parity doublet model. We analyze second-order susceptibilities of net-proton and net-neutron numbers and their correlations. We show that proton-neutron correlations are nontrivial and lead to qualitative differences between net-proton and net-baryon fluctuations. We further investigate factorial cumulants and demonstrate that the differences between baryon- and proton-number factorial cumulants are governed by proton-neutron correlations. Our results highlight the importance of interaction-driven correlations for interpreting fluctuation measurements near the liquid-gas critical endpoint.