Two-loop QCD corrections for real and off-shell diphoton and triphoton production via quark loops

TL;DR

This paper presents a comprehensive method for calculating next-to-next-to-leading order QCD corrections to diphoton and triphoton production via quark loops, enabling precise numerical predictions for these processes.

Contribution

It introduces a unified framework for handling all cases of photon production with quark loops at NNLO, including a novel subtraction method for singularities and new numerical results.

Findings

Confirmed agreement with existing analytic benchmarks.

Provided new numerical results for off-shell diphoton and triphoton production.

Computed double-virtual corrections for relevant processes.

Abstract

We compute squared matrix elements at next-to-next-to-leading order in perturbative quantum chromodynamics for the production of two or three (on- or off-shell) photons mediated via (light or heavy) quark loops. Our method handles all cases in a unified framework, using simultaneous subtraction of infrared, ultraviolet, and threshold singularities in loop momentum space to produce a locally finite integrand suitable for numerical integration. We confirm agreement with available analytic benchmarks at fixed phase-space points and provide new results otherwise. We also compute the double-virtual corrections to the cross section for on- and off-shell diphoton and on-shell triphoton production by combining the Monte Carlo integration over loop and phase space.