Influence of pions on the hadron-quark phase transition

TL;DR

This paper investigates how pions influence the hadron-quark phase transition diagrams using different models for hadronic and quark sectors, showing that pions shift the critical end point depending on model parameters.

Contribution

It introduces the inclusion of pions into hadron-quark transition models and analyzes their effect on the phase diagram's critical end point using two PNJL parametrizations.

Findings

Pions shift the critical end point of the phase transition.

The effect depends on the critical temperature T_0 used in the models.

Different T_0 values alter the phase diagram features.

Abstract

In this work we present the features of the hadron-quark phase transition diagrams in which the pions are included in the system. To construct such diagrams we use two different models in the description of the hadronic and quark sectors. At the quark level, we consider two distinct parametrizations of the Polyakov-Nambu-Jona-Lasinio (PNJL) models. In the hadronic side, we use a well known relativistic mean-field (RMF) nonlinear Walecka model. We show that the effect of the pions on the hadron-quark phase diagrams is to move the critical end point (CEP) of the transitions lines. Such an effect also depends on the value of the critical temperature (T_0) in the pure gauge sector used to parametrize the PNJL models. Here we treat the phase transitions using two values for T_0, namely, T_0 = 270 MeV and T_0 = 190 MeV. The last value is used to reproduce lattice QCD data for the transition temperature at zero chemical potential.