REDUCTION OF GENERAL 2-LOOP SELF-ENERGIES TO STANDARD SCALAR INTEGRALS

A method is presented for reducing general two-loop self-energies to s tandard scalar integrals in massive gauge theories with special emphas is on the electroweak Standard Model (SM). We develop a technique for treating the tensor structure of two-loop integrals appearing in self- energy calculations. It is used together with the symmetry properties of the integrals to obtain a result in terms of a small number of stan dard scalar integrals. The results are valid for arbitrary values of t he invariant momentum p2, all particle masses, the space-time dimensio n D and the gauge parameters xi(i) (i = gamma, Z, W). The algebraic st ructure of the results clearly displays the gauge dependence of the co nsidered quantities and allows us to perform very stringent checks. We explicitly verify Slavnov-Taylor identities by calculating several th ousand Feynman diagrams and adding them up algebraically. As an applic ation of our algorithm we calculate the light fermion contributions to the two-loop gauge boson self-energies of the electroweak SM. We stud y their gauge dependence and discuss the occurring standard integrals.