Pion masses at finite temperature

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.