I will discuss the calculation of the complete two-loop QCD corrections for the production of three photons at the LHC, including subleading colour contributions. The two-loop numerical unitarity approach used previously for the planar contributions is extended to handle five-point non-planar topologies. Analytic expressions for the two-loop remainders are reconstructed and simplified using spinor-helicity variables. The analytic results we obtain are found to be numerically stable and rarely require muti-precision recovery strategies. Finally, we explore the numerical size of the subleading-color contribution to the two-loop hard functions, and find them to be potentially relevant to achieve theoretical predictions at the 1% precision level.
Hybrid event
Robert Szafron