Two-loop leading-color helicity amplitudes for three-photon production at the LHC

Understand

We calculate all planar contributions to the two-loop massless helicity amplitudes for the process $q\bar q\to \gamma\gamma\gamma$.

• 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 $pp\to \gamma\gamma\gamma$ [Chawdhry et al.
• (2019)].