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 $M_H\sim 600\mathrm{GeV}$, and discuss the interference effects in double Higgs production. The interference effects distort the double Higgs invariant mass distributions and, depending on $M_H$, can enhance the total cross section by up to $\sim 20\%$ or decrease by $\sim 30\%$ for viable mixing parameters. We compute the next-to-leading-order QCD corrections in the large $m_t$ limit. The corrections are large and can also significantly distort kinematic distributions near the resonance peak.

• Received 4 September 2015

DOI:https://doi.org/10.1103/PhysRevD.92.094023