Medium effects and parity doubling of hyperons across the deconfinement phase transition

TL;DR

This paper investigates how hyperons' masses and parity properties change across the deconfinement phase transition, revealing parity doubling near the transition and its implications for heavy-ion physics.

Contribution

It provides the first lattice QCD analysis of hyperon parity doubling across the deconfinement transition, highlighting temperature-dependent mass degeneracies.

Findings

Negative-parity hyperon masses decrease with temperature.

Parity doubling occurs near the deconfinement temperature.

Parity doubling strength varies with strangeness content.

Abstract

We analyse the behaviour of hyperons with strangeness $S=-1$,$-2$,$-3$ in the hadronic and quark gluon plasma phases, with particular interest in parity doubling and its emergence as the temperature grows. This study uses our FASTSUM anisotropic $N_f\!\!=$~2+1 ensembles, with four temperatures below and four above the deconfinement transition temperature, $T_c$. The positive-parity groundstate masses are found to be largely temperature independent below $T_c$, whereas the negative-parity ones decrease considerably as the temperature increases. Close to the transition, the masses are almost degenerate, in line with the expectation from chiral symmetry restoration. This may be of interest for heavy-ion phenomenology. In particular we show an application of this effect to the Hadron Resonance Gas model. A clear signal of parity doubling is found above $T_c$ in all hyperon channels, with the strength of the effect depending on the number of $s$-quarks in the baryons.