Calculation of screening in a hot plasma

Tree-level calculations of thermal processes involving the exchange of massless gauge bosons give rise to infrared divergences which are screened by thermal loop corrections. For gauge theories at high temperatures or densities, a resummation method for the complete calculation of the effects of screening to leading order in the coupling constant is developed. The method is applied to calculte the rate of energy loss of a hot plasma from the Primakoff production of axions. Previous ad hoc prescriptions for screening significantly underestimate the contribution from magnetic scattering.