Techniques for one-loop tensor integrals in many-particle processes

Abstract

We briefly sketch the methods for a numerically stable evaluation of tensor one-loop integrals that have been used in the calculation of the complete electroweak one-loop corrections to \Pep\Pem\to4 fermions. In particular, the improvement of the new methods over the conventional Passarino--Veltman reduction is illustrated for some 4-point integrals in the delicate limits of small Gram (and other kinematical) determinants.Comment: 5 pages, latex, 2 postscript figures, to appear in the proceedings of the "7th International Symposium on Radiative Corrections (RADCOR2005)", Shonan Village, 200