Radiative corrections to the semileptonic and hadronic Higgs-boson decays H→WW/ZZ→4 fermions

The radiative corrections of the strong and electroweak interactions arecalculated for the Higgs-boson decays H -> WW/ZZ -> 4f with semileptonic orhadronic four-fermion final states in next-to-leading order. This calculationis improved by higher-order corrections originating from heavy-Higgs-bosoneffects and photonic final-state radiation off charged leptons. The W- andZ-boson resonances are treated within the complex-mass scheme, i.e. without anyresonance expansion or on-shell approximation. The calculation essentiallyfollows our previous study of purely leptonic final states. The electroweakcorrections are similar for all four-fermion final states; for integratedquantities they amount to some per cent and increase with growing Higgs-bosonmass M_H, reaching 7-8% at M_H \sim 500 GeV. For distributions, the correctionsare somewhat larger and, in general, distort the shapes. Among the QCDcorrections, which include corrections to interference contributions of theBorn diagrams, only the corrections to the squared Born diagrams turn out to berelevant. These contributions can be attributed to the gauge-boson decays, i.e.they approximately amount to \alpha_s/\pi for semileptonic final states and2\alpha_s/\pi for hadronic final states. The discussed corrections have beenimplemented in the Monte Carlo event generator PROPHECY4F.Comment: 29 pages, LaTeX, 30 postscript figure