The Fermion Boson Interaction Within the Linear Sigma Model at Finite Temperature

We reinvestigate the interaction of massless fermions with massless bosons at finite temperature. Specifically, we calculate the self-energy of massless fermions due the interaction with massless bosons at high temperature, which is the region where thermal effects are maximal. The calculations are concentrated in the limit of vanishing fermion three momentum and after considering the effective fermion and boson dressed masses, we obtain the damping rate of the fermion up to order $g^3$. It is shown that in the limit $k_0 \ll T$ the fermion acquire a thermal mass of order $gT$ and the leading term of the fermion damping rate is of order $g^2T+g^3T$.