Probing the Higgs portal at the LHC through resonant di-Higgs production

We investigate resonant di-Higgs production as a means of probing extended scalar sectors that include a 125 GeV Standard Model-like Higgs boson. For concreteness, we consider a gauge singlet Higgs portal scenario leading to two mixed doublet-singlet states, h(1,2). For m(h2) > 2m(h1), the resonant di-Higgs production process p p -> h(2) -> h(1) h(1) will lead to final states associated with the decaying pair of Standard Model-like Higgs scalars. We focus on h(2) production via gluon fusion and on the b (b) over bar tau(+)tau(-) final state. We find that discovery of the h(2) at the LHC may be achieved with <= 100 fb(-1) of integrated luminosity for benchmark parameter choices relevant to cosmology. Our analysis directly maps onto the decoupling limit of the next-to-minimal supersymmetric Standard Model and more generically onto extensions of the Standard Model Higgs sector in which a heavy scalar produced through gluon-fusion decays to a pair of Standard Model-like Higgs bosons.