Pair production of Higgs bosons at the Large Hadron Collider (LHC) is known to be important for the determination of the Higgs boson self-coupling and as a probe of new physics beyond the Standard Model (SM), especially the existence of new fundamental scalar bosons. In this paper we study in detail the pair production of Higgs bosons at the LHC in a well-motivated model—the gauged two-Higgs-doublet model—in which the two Higgs doublets are properly embedded into a gauged $SU(2{)}_H$ and a dark matter candidate emerges naturally due to the gauge symmetry. Besides the deviations of the Higgs couplings from the SM predictions, the existence of new scalars could significantly enhance the production cross section of Higgs boson pairs at the LHC. However, when we take into account the relic density of dark matter and the null results of direct detection experiments, only a moderate enhancement can be obtained. We also comment on the capability of the LHC to distinguish the Higgs pair signal due to a generic 400 GeV scalar resonance in the $\gamma \gamma b\overline{b}$ final state from the SM prediction, assuming that their Higgs pair production cross sections are the same.

• Received 31 October 2018

DOI:https://doi.org/10.1103/PhysRevD.99.075027

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Published by the American Physical Society