Pions in the quark matter phase diagram

TL;DR

This paper investigates mesonic correlations and quantum condensates in the quark matter phase diagram using a NJL-type quantum field theoretical approach, revealing conditions under which pions behave as quasi-bound states.

Contribution

It introduces a detailed analysis of scalar and pseudoscalar meson excitations in the quark matter phase diagram, highlighting regions where pions are quasi-bound states.

Findings

Pions are zero-width bound states outside chiral symmetry breaking regions.

Pions can be quasi-bound states in high-temperature crossover and color superconducting phases.

Pion lifetime exceeds that of typical heavy-ion collision fireballs in identified regions.

Abstract

The relationship between mesonic correlations and quantum condensates in the quark matter phase diagram is explored within a quantum field theoretical approach of the Nambu and Jona-Lasinio (NJL) type. Mean-field values in the scalar meson and diquark channels are order parameters signalling the occurrence of quark condensates, entailing chiral symmetry breaking (chi SB) and color superconductivity (2SC) in quark matter. We investigate the spectral properties of scalar and pseudoscalar meson excitations in the phase diagram in Gaussian approximation and show that outside the chi SB region where the pion is a zero-width bound state, there are two regions where it can be considered as a quasi-bound state with a lifetime exceeding that of a typical heavy-ion collision fireball: (A) the high-temperature chi SB crossover region at low densities and (B) the high-density color superconducting phase at temperatures below 100 MeV.