Non-perturbative effects in Higgs boson decays to electroweak vector bosons and photons

We estimate the magnitude of the leading non-perturbative QCD corrections to the decays of the Higgs boson to the γZ and γγ final states. These corrections originate from the light-quark contributions to such decays. We show that the non-perturbative effects are suppressed by the small Yukawa couplings of light quarks, but that there is no further quark-mass suppression. This is at variance with what is found in the standard perturbative calculations of the light-quark contributions. We demonstrate that the non-perturbative corrections modify the H → γZ and H → γγ decay rates by O(10−5), well below the expected precision with which such decays can be studied both at the high-luminosity LHC and at future colliders.