Photon pair production in gluon fusion: Top quark effects around threshold

TL;DR

This paper calculates next-to-leading order QCD corrections to gluon fusion producing photon pairs, including top quark effects, providing detailed insights into the diphoton mass spectrum near the top quark pair production threshold.

Contribution

It presents the first two-loop calculation of massive top quark effects in gluon fusion photon pair production, combining fixed order and resummation techniques.

Findings

Enhanced understanding of diphoton spectrum near top threshold

Quantitative impact of top quark loops on photon pair production

Improved theoretical predictions for collider experiments

Abstract

We present a calculation of the NLO QCD corrections to the loop-induced production of a photon pair through gluon fusion, including massive top quarks at two loops. The two-loop virtual amplitudes are computed via projecting onto a set of Lorentz structures related to linear polarisation states of external gauge bosons. All two-loop master integrals dependent on the top quark mass are evaluated numerically. Matching the fixed order NLO result to a calculation with threshold resummation, we obtain an accurate description of the diphoton invariant mass spectrum around the threshold of top quark pair production. We analyse how the distribution of the diphoton invariant mass is affected by the top quark loop-induced corrections, especially around the top quark pair production threshold.