NLO corrections to double Higgs boson production in the Higgs singlet model

Higgs pair production at the LHC from gluon fusion is small in the Standard Model but can be enhanced in models where a resonant enhancement is allowed. We examine the effect of a resonant contribution from a second scalar arising in a model with a gauge singlet scalar field in addition to the usual SU(2) scalar doublet, with mass up to MH~600 GeV, and discuss the interference effects in double Higgs production. The interference effects distort the double Higgs invariant mass distributions and, depending on MH, can enhance the total cross section by up to ~20% or decrease by ~30% for viable mixing parameters. We compute the next-to-leading-order QCD corrections in the large mt limit. The corrections are large and can also significantly distort kinematic distributions near the resonance peak.