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 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 > 30 GeV, at leading order. On the other hand, radiating a high- p 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 power. As a result, the Hγ production via top loops at the LHC has rates comparable with the ones arising from either the $$ Ht\overline{t} $$ 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 $$ b\overline{b}\to H\gamma $$ and $$ c\overline{c}\to H\gamma $$. The Hγ production via electroweak loops has just a minor role. At larger c.m. energies, the $$ Ht\overline{t}\gamma $$ channel surpasses the total contribution of top-loop processes. In particular, requiring p > 30 GeV at $$ \sqrt{S}\simeq 100 $$ TeV, $$ Ht\overline{t}\gamma $$ accounts for about 1 /4 of the inclusive Hγ production at leading order, about half of the total being due to VBF production. [ABSTRACT FROM AUTHOR]