Factorizing one-loop contributions to two-loop Bhabha scattering and automatization of Feynman diagram calculations

Abstract

In higher order calculations a number of new technical problems arise: one needs diagrams in arbitrary dimension in order to obtain their needed $ϵ$-expansion, zero Gram determinants appear, renormalization produces diagrams with `dots' on the lines, i.e. higher order powers of scalar propagators. All these problems cannot be accessed by the `standard' Passarino-Veltman approach: there is not available what is needed for higher loops. We demonstrate our method of how to solve these problems.

Comments: 2 pages, Latex using espcrc2.sty, 1 figure using 1 eps file. Contribution to ACAT 2002, Moscow, Russia, June 24-28, 2002