Pion masses at finite temperature

TL;DR

This paper investigates how charged and neutral pion masses vary with temperature using Chiral Perturbation Theory and resonance models, revealing an increase in mass difference at certain temperatures and effects of axial-vector mixing.

Contribution

It provides the first analysis of thermal pion mass differences incorporating both Chiral Perturbation Theory and resonance models, including axial-vector mixing effects.

Findings

Pion mass difference increases at low and intermediate temperatures.

Axial-vector mixing from chiral restoration affects temperature dependence.

Resonance corrections do not significantly alter ChPT predictions.

Abstract

We present preliminary results on a study about the thermal variation of the charged and neutral pion masses to one loop, analyzing their electromagnetic difference, in the context of Chiral Perturbation Theory with two flavours, as well as using a light resonance model. We find that the pion mass difference increases for, at least, low and intermediate temperatures, unlike the chiral limit decreasing result. The axial-vector mixing arising from chiral restoration smooths the Debye-screening temperature increase. Taking into account further corrections due to axial and vector resonances, dominated by a1 and rho particles respectively, does not change significantly the ChPT prediction.