Light-by-light scattering in SANC

TL;DR

This paper details the implementation of light-by-light scattering via fermion loops in the SANC system, including massive fermion effects, amplitude calculations, and comparisons with existing literature.

Contribution

It introduces a new implementation of the $ ext{γγ→γγ}$ process in SANC, accounting for fermion mass effects and providing detailed amplitude calculations.

Findings

Covariant and helicity amplitudes computed

Inclusion of non-zero fermion mass effects

Comparison with existing literature results

Abstract

In this paper we describe the implementation of the QED process $\gamma\gamma\to\gamma\gamma$ 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 $D_0$ and $C_0$ Passarino-Veltman functions. Whenever possible, we compare the results with those existing in the literature.