  Thermal perturbation theory based on the resummation scheme by Braaten and
Pisarski suffers from unscreened collinear singularities whenever outer momenta
become light-like. A recently proposed improvement of the hard thermal loops by
an additional resummation of an asymptotic mass promises to solve this problem.
Here we present a detailed investigation of the next-to-leading order plasmon
self-energy. It demonstrates the applicability and consistency of the improved
scheme.
