We calculate all planar contributions to the two-loop massless helicity amplitudes for the process qqˉ→γγγ. The results are presented in fully analytic form in terms of the functional basis proposed recently by Chicherin and Sotnikov. With this publication we provide the two-loop contributions already used by us in the NNLO QCD calculation of the LHC process pp→γγγ [Chawdhry et al. (2019)]. Our results agree with a recent calculation of the same amplitude [Abreu et al. (2020)] which was performed using different techniques. We combine several modern computational techniques, notably, analytic solutions for the IBP identities, finite-field reconstruction techniques as well as the recent approach [Chen (2019)] for efficiently projecting helicity amplitudes. Our framework appears well-suited for the calculation of two-loop multileg amplitudes for which complete sets of master integrals exist.
@article{arxiv.2012.13553,
title = {Two-loop leading-color helicity amplitudes for three-photon production at the LHC},
author = {Herschel A. Chawdhry and Michal Czakon and Alexander Mitov and Rene Poncelet},
journal= {arXiv preprint arXiv:2012.13553},
year = {2021}
}