HEAVY HIGGS-BOSON LIFETIME AT 2 LOOPS

The standard-model Higgs boson with a mass M(H) much greater than 2M(Z ) decays almost exclusively to pairs of W and Z bosons. We calculate t he dominant two-loop corrections, of O(G(F)(2) M(H)(4)), to the partia l widths of these decays. In the on-mass-shell renormalization scheme, the correction factor is found to be 1 + 14.6%(M(H)/TeV)(2) + 16.9%(M (H)/TeV)(4), where the second term is the one-loop correction. We give full analytic results for all divergent two-loop Feynman diagrams. A subset of finite two-loop vertex diagrams is computed to high precisio n using numerical techniques. We find agreement with a previous numeri cal analysis. The above correction factor is also in line with a recen t lattice calculation.