Abstract
Future precision measurements of Higgs boson decays will determine the branching fraction for the decay into two photons with a precision at the one percent level. To fully exploit such measurements, equally precise theoretical predictions need to be available. To this end we compute four-loop QCD corrections in the large top quark mass expansion to the Higgs boson--photon form factor, which enter the two-photon decay width at next-to-next-to-next-to-leading order. Furthermore we obtain corrections to the two-photon decay width stemming from the emission of additional gluons, which contribute for the first time at next-to-next-to-leading order. Finally, we combine our results with other available perturbative corrections and estimate the residual uncertainty due to missing higher-order contributions.
Highlights
The decay of the Higgs boson into two photons was among the main discovery channels at the Large Hadron Collider (LHC) [1,2] and plays a crucial role in precision studies of its properties
Future colliders will allow the measurement of ratios of branching fractions at the subpercent level, demanding theoretical predictions of partial decay widths at the same level of precision
While the next-to-next-to-leading order (NNLO) top quark–induced corrections amount to less than one percent of the full decay width, it is possible that their smallness is accidental and higher order corrections are of the same size
Summary
The decay of the Higgs boson into two photons was among the main discovery channels at the Large Hadron Collider (LHC) [1,2] and plays a crucial role in precision studies of its properties Among these are measurements of its mass, see, e.g., [3], as well as the study of the interference between the diphoton signal with the continuum background, which leads to a shift in the diphoton mass spectrum and in production rates, allowing for studies of the total Higgs boson width [4,5,6,7,8,9]. These real-radiation contributions should be considered since in principle the emission of additional, possibly soft, gluons leads to a shift in the measured diphoton mass spectrum due to the energy carried by the gluons.
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