Higgs-photon resonances

Abstract

We study models that produce a Higgs boson plus photon ($h^0\gamma$) resonance at the LHC. When the resonance is a $Z^{\prime }$ boson, decays to $h^0\gamma$ occur at one loop. If the $Z^{\prime }$ boson couples at tree-level to quarks, then the $h^0\gamma$ branching fraction is typically of order $10^{-5}$ or smaller. Nevertheless, there are models that would allow the observation of $Z^{\prime }\to h^0\gamma$ at $\sqrt{s}=13$ TeV with a cross section times branching fraction larger than 1 fb for a $Z^{\prime }$ mass in the 200--450 GeV range, and larger than 0.1 fb for a mass up to 800 GeV. The 1-loop decay of the $Z^{\prime }$ into lepton pairs competes with $h^0\gamma$, even if the $Z^{\prime }$ couplings to leptons vanish at tree level. We also present a model in which a $Z^{\prime }$ boson decays into a Higgs boson and a pair of collimated photons, mimicking an $h^0\gamma$ resonance. In this model, the $h^0\gamma$ resonance search would be the discovery mode for a $Z^{\prime }$ as heavy as 2 TeV. When the resonance is a scalar, although decay to $h^0\gamma$ is forbidden by angular momentum conservation, the $h^0$ plus collimated photons channel is allowed. We comment on prospects of observing an $h^0\gamma$ resonance through different Higgs decays, on constraints from related searches, and on models where $h^0$ is replaced by a nonstandard Higgs boson.

22 pages

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