Photon-pair jet production via gluon fusion at the LHC

Abstract

Photon-pair direct or jet-associated production is important for relevant standard model measurement, Higgs and new physics searches at the Large Hadron Collider (LHC). The loop-induced gluon-fusion process gg → γγg, which formally contributes only at the next-to-next-to-leading order to γγj productions, may get enhanced by the large gluon flux at the LHC. We have checked and confirmed previous results on gg → γγ (Dicus and Willenbrock 1988 Phys. Rev. D 37 1801), γγg (de Florian and Kunszt 1999 Phys. Lett. B 460 184) at one loop, using the traditional Feynman diagram based approach, taking into account the quark mass effects, and updated them further for the 7 and 14 TeV LHC with new inputs and settings. We provide the details and results of the calculations, which involve 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 Mγγ and PTγγ, and increase further the overall scale uncertainty. Top quark loop effects are examined in detail, which become important near or above the threshold Mγγ ≳ 2mt.