Screening masses of positive- and negative-parity hadron ground-states, including those with strangeness

TL;DR

This study uses a symmetry-preserving contact interaction model to compute the temperature-dependent screening masses of various hadrons, revealing parity degeneracy above the critical temperature and insights into diquark correlations within baryons.

Contribution

It provides a novel calculation of hadron screening masses at finite temperature using a contact interaction approach, aligning qualitatively with lattice QCD results and exploring chiral symmetry restoration effects.

Findings

Parity-partner degeneracy occurs above T_c.

Negative parity meson masses increase monotonously with temperature.

Positive parity meson masses are nearly invariant below T_c/2, then degenerate with negative parity partners near T_c.

Abstract

Using a symmetry-preserving treatment of a vector $\times$ vector contact interaction (SCI) at nonzero temperature, we compute the screening masses of flavour-SU(3) ground-state $J^P=0^\pm$, $1^\pm$ mesons, and $J^P=1/2^\pm$, $3/2^\pm$ baryons. We find that all correlation channels allowed at $T=0$ persist when the temperature increases, even above the QCD phase transition. The results for mesons qualitatively agree with those obtained from the contemporary lattice-regularised quantum chromodynamics (lQCD) simulations. One of the most remarkable features is that each parity-partner-pair degenerates when $T>T_c$, with $T_c$ being the critical temperature. For each pair, the screening mass of the negative parity meson increases monotonously with temperature. In contrast, the screening mass of the meson with positive parity is almost invariant on the domain $T\lesssim T_c/2$; when $T$ gets close to $T_c$, it decreases but soon increases again and finally degenerates with its parity partner, which signals the restoration of chiral symmetry. We also find that the $T$-dependent behaviours of baryon screening masses are quite similar to those of the mesons. For baryons, the dynamical, nonpointlike diquark correlations play a crucial role in the screening mass evolution. We further calculate the evolution of the fraction of each kind of diquark within baryons respective to temperature. We observe that, at high temperatures, only $J=0$ scalar and pseudoscalar diquark correlations can survive within $J^P=1/2^\pm$ baryons.