Radiative corrections for H→W+W-(γ) in the standard model

The HW+W- three-point function with all external particles being off-mass-shell is calculated in the one-loop approximation of the minimal standard model of electroweak interaction. The effect of radiative corrections on the Higgs-boson decay mode H → W+W-(γ) is examined. The soft-photon bremsstrahlung is resummed using Yennie-Frautschi-Suura exponentiation and the hard-photon spectrum is integrated analytically. The impact of a fourth generation of heavy fermions is investigated. Approximation formulae are presented for the light-fermion contribution and for the case that the Higgs boson is heavy as compared to the weak vector bosons. In the modified on-mass-shell scheme the partial decay width may be enhanced by up to 15% if the masses of both the Higgs boson and the top quark assume values close to their theoretical upper bounds. (orig.)