# Hyperons in thermal QCD: A lattice view

## TL;DR

This paper investigates how hyperon masses and parity properties change with temperature in QCD using lattice simulations, leading to an improved in-medium hadron resonance gas model that accounts for in-medium effects.

## Contribution

It introduces a lattice-based analysis of hyperon in-medium effects, providing a parametrization of negative-parity mass dependence and an enhanced HRG model for hot QCD matter.

## Key findings

- Positive-parity hyperon masses are temperature independent within errors.
- Negative-parity hyperon masses show strong temperature dependence.
- Parity doubling occurs in the deconfined phase, influenced by the s quark mass.

## Abstract

The hadron resonance gas (HRG) is a widely used description of matter under extreme conditions, e.g. in the context of heavy-ion phenomenology. Commonly used implementations of the HRG employ vacuum hadron masses throughout the hadronic phase and hence do not include possible in-medium effects. Here we investigate this issue, using nonperturbative lattice simulations employing the FASTSUM anisotropic Nf=2+1 ensembles. We study the fate of octet and decuplet baryons as the temperature increases, focussing in particular on the positive- and negative-parity groundstates. While the positive-parity groundstate masses are indeed seen to be temperature independent, within the error, a strong temperature dependence is observed in the negative-parity channels. We give a simple parametrisation of this and formulate an in-medium HRG, which is particularly effective for hyperons. Parity doubling is seen to emerge in the deconfined phase at the level of correlators, with a noticeable effect of the heavier s quark. Channel dependence of this transition is analysed.