Photon pair production in gluon fusion: Top quark effects at NLO with threshold matching

TL;DR

This paper calculates next-to-leading order QCD corrections to gluon fusion producing photon pairs, incorporating top quark effects at two loops, and explores implications for top quark mass measurements.

Contribution

It provides the first numerical two-loop calculation of top quark effects in photon pair production via gluon fusion at NLO, including threshold matching.

Findings

Top quark threshold corrections significantly influence diphoton invariant mass distributions.

Matching fixed-order results with threshold expansion improves accuracy near top pair production threshold.

Potential to extract top quark mass from diphoton spectrum measurements.

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, where the two-loop integrals are calculated numerically. Matching the fixed-order NLO results to a threshold expansion, we obtain accurate results around the top quark pair production threshold. We analyse how the top quark threshold corrections affect distributions of the photon pair invariant mass and comment on the possibility of determining the top quark mass from precision measurements of the diphoton invariant mass spectrum.