Photon-pair jet production via gluon fusion at the LHC

TL;DR

This paper investigates the gluon-fusion process gg -> gamma gamma g at the LHC, confirming previous calculations, updating results for 7 and 14 TeV energies, and analyzing the impact of quark mass effects on photon-pair production.

Contribution

It provides detailed calculations of the gluon-fusion contribution to photon-pair production, including quark mass effects and updates for current LHC energies, using a Feynman diagram approach.

Findings

Gluon-fusion contributes about 10% of the Born result at small M_{γγ} and P_{T_{γγ}}.

Top quark loops are significant near or above the 2m_t threshold.

Results increase the understanding of scale uncertainties in photon-pair production.

Abstract

Photon-pair direct or jet-associated productions are important for relevant standard model measurement, Higgs and new physics searches at the LHC. The loop-induced gluon-fusion process gg -> \gamma\gamma g, which although formally contributes only at the next-to-next-to-leading order to \gamma\gamma j productions, may get enhanced by the large gluon flux at the LHC. We have checked and confirmed previous results on gg -> \gamma\gamma, \gamma\gamma g at one loop, using now the traditional Feynman diagram based approach and taking into account the quark mass effects, and further updated them for the 7 and 14 TeV LHC with new inputs and settings. We provide the details and results of the calculations, which involves manipulation of rank-5 pentagon integrals. Our results show that the gluon-fusion process can contribute about 10% of the Born result, especially at small M_{\gamma\gamma} and PT_{\gamma\gamma}, and increase further the overall scale uncertainty. Top quark loop effects are examined in detail, which shows importance near or above the threshold M_{\gamma\gamma} \gsim 2m_t.