ANALYTICAL AND NUMERICAL-METHODS FOR MASSIVE 2-LOOP SELF-ENERGY DIAGRAMS

Motivated by the precision results in the electroweak theory studies o f two-loop Feynman diagrams are performed. Specifically this paper giv es a contribution to the knowledge of massive two-loop self-energy dia grams in arbitrary and especially four dimensions, This is done in thr ee respects: firstly results in terms of generalized, multivariable hy pergeometric functions are presented giving explicit series for small and large momenta. Secondly the imaginary parts of these integrals are expressed as complete elliptic integrals. Finally one-dimensional int egral representations with elementary functions are derived. They are very well suited for the numerical evaluations.