Equation of state of hadron resonance gas and the phase diagram of strongly interacting matter

TL;DR

This paper models the equation of state for hadron resonance gas at finite temperature and density, exploring phase transitions and strangeness effects, to better understand the phase diagram of strongly interacting matter.

Contribution

It introduces a comprehensive model including finite-size effects, strange hadrons, and a density-dependent mean field to analyze the QCD phase diagram and strangeness phenomena.

Findings

The phase transition boundary is determined using Gibbs conditions with strangeness neutrality.

Strangeness-antistrangeness separation in the mixed phase is possible under certain conditions.

Nonmonotonous strangeness fugacity behavior explains peaks in particle multiplicity ratios.

Abstract

The equation of state of hadron resonance gas at finite temperature and baryon density is calculated taking into account finite-size effects within the excluded volume model. Contributions of known hadrons with masses up to 2 GeV are included in the zero-width approximation. Special attention is paid to the role of strange hadrons in the system with zero total strangeness. A density- dependent mean field is added to guarantee that the nuclear matter has a saturation point and a liquid-gas phase transition. The deconfined phase is described by the bag model with lowest order perturbative corrections. The phase transition boundary is found by using the Gibbs conditions with the strangeness neutrality constraint. The sensitivity of the phase diagram to the hadronic excluded volume and to the parametrization of the mean-field is investigated. The possibility of strangeness-antistrangeness separation in the mixed phase is analyzed. It is demonstrated that the peaks in the kaon to pion and lambda to pion multiplicity ratios can be explained by a nonmonotonous behavior of the strangeness fugacity along the chemical freeze-out line.