Thermal Meson properties within Chiral Perturbation Theory

We report on our recent work about the description of a meson gas below thechiral phase transition within the framework of Chiral Perturbation Theory. Asan alternative to the standard treatment, we present a calculation of the quarkcondensate which combines the virial expansion and the meson-meson scatteringdata. We have also calculated the full one-loop elastic pion scatteringamplitude at finite temperature and we have unitarized the amplitude using theInverse Amplitude Method in order to reproduce the temperature effects on themass and width of the $\rho$ and $\sigma$ resonances. Our results show a clearincrease of the thermal $\rho$ width, as expected from previous analysis. Theresults for the $\sigma$ are consistent with Chiral Symmetry Restoration. Wecomment on the relevance of our results within the context of RelativisticHeavy Ion Collisions.Comment: 14 pages, 7 figures. To appear in the Proceedings of the "2nd International Workshop on Hadron Physics: Effective Theories of Low Energy QCD