Asking for an extra photon in Higgs production at the LHC and beyond

We study the inclusive production of a Higgs boson in association with a high-p_T photon at the LHC, detailing the leading-order features of the main processes contributing to the Hγ final state. Requiring an extra hard photon in Higgs production upsets the cross-section hierarchy for the dominant channels. The Hγ inclusive production comes mainly from photons radiated in vector-boson fusion (VBF), which accounts for about 2/3 of the total rate, for p_T^γ,j>30 GeV, at leading order. On the other hand, radiating a high-p_T photon in the main top-loop Higgs channel implies an extra parton in the final state, which suppresses the production rate by a further α_S power. As a result, the Hγ production via top loops at the LHC has rates comparable with the ones arising from either the Htt̄ production or the HW(Z)γ associated production. Then, in order of decreasing cross section, comes the single-top-plus-Higgs channel, followed in turn by the heavy-flavor fusion processes bb̄→Hγ and cc̄→Hγ. The Hγ production via electroweak loops has just a minor role. At larger c.m. energies, the Htt̄γ channel surpasses the total contribution of top-loop processes. In particular, requiring p_T^γ,j>30 GeV at √S≃100 TeV, Htt̄γ accounts for about 1/4 of the inclusive Hγ production at leading order, about half of the total being due to VBF production.