Two-loop electroweak corrections to the Higgs-boson decay H → γγ

The complete set of two-loop electroweak corrections to the decay width of the Higgs boson into two photons is presented. Two-loop contributions involving weak bosons and the top quark are computed in terms of an expansion in the Higgs external momentum. Adding these results to the previously known light fermion contributions, we find that the total electroweak corrections for a Higgs boson with 100 less than or similar to m(H) less than or similar to 150 GeV are moderate and negative, between -4% less than or similar to delta(EW) less than or similar to 0%. Combination with the QCD corrections, which are small and positive, gives a total correction to the one-loop results of vertical bar delta(EW+QCD)vertical bar less than or similar to 1.5%. (c) 2005 Elsevier B.V. All rights reserved.