An effective chiral Hadron-Quark Equation of State

TL;DR

This paper develops an effective chiral Hadron-Quark model for the QCD equation of state, capturing phase transitions and matching lattice data qualitatively, with implications for understanding the QCD phase diagram.

Contribution

It introduces a unified model incorporating chiral symmetry restoration and deconfinement, including asymptotic degrees of freedom, and analyzes phase transition characteristics at finite baryon densities.

Findings

Model reproduces a rapid crossover for order parameters.

Thermodynamic properties align qualitatively with lattice data.

The phase diagram shows a wide crossover with no first-order deconfinement or chiral transition.

Abstract

We construct an effective model for the QCD equation of state, taking into account chiral symmetry restoration as well as the deconfinement phase transition. The correct asymptotic degrees of freedom at the high and low temperature limits are included (quarks $\leftrightarrow$ hadrons). The model shows a rapid crossover for both order parameters, as is expected from lattice calculations. We then compare the thermodynamic properties of the model at $\mu_B=0$ which turn out to be in qualitative agreement with lattice data, while apparent quantitative differences can be attributed to hadronic contributions and excluded volume corrections. Furthermore we discuss the effects of a repulsive vector type quark interaction at finite baryon number densities on the resulting phase diagram of the model. Our current model is able to reproduce a first-order liquid gas phase transition as expected, but does not show any signs of a first order deconfinement or chiral phase transition. Both transitions rather appear as a very wide crossover in which heavily medium modified hadron coexist with free quarks.