J_AW,WA functions in Passarino-Veltman reduction

Understand

In this paper we continue to study a special class of Passarino-Veltman functions J arising at the reduction of infrared divergent box diagrams.

• We describe a procedure of separation of two types of singularities, infrared and mass singularities, which are absorbed in simple C0 functions.
• The infrared divergences of C0's can be regularized then by any method: photon mass, dimensionally or by the width of an unstable particle.
• Functions J, in turn, are represented as certain linear combinations of the standard D0 and C0 Passarino-Veltman functions.