Light-by-light scattering in SANC

In this paper we describe the implementation of the QED process γγ → γγ through a fermion loop into the framework of SANC system. The computations of this process takes into account non-zero mass of loop-fermion. We briefly describe additional precomputation modules used for calculation of massive fermion-box diagrams. We present the covariant and helicity amplitudes for this process and also some particular cases of D0 and C0 Passarino–Veltman functions. Whenever possible, we compare the results with those existing in the literature. Talk presented at the International School–Seminar CALC2006, Dubna, 15-25 July 2006 E-mails: [email protected], [email protected], [email protected], [email protected]