Heavy Higgs-boson lifetime at two loops

The standard-model Higgs boson with a mass MH>2MZ decays almost exclusively to pairs of W and Z bosons. We calculate the dominant two-loop corrections, of O(G2FM4H), to the partial widths of these decays. In the on-mass-shell renormalization scheme, the correction factor is found to be 1+14.6%(MH/TeV)2+16.9%(MH/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 precision using numerical techniques. We find agreement with a previous numerical analysis. The above correction factor is also in line with a recent lattice calculation. copyright 1996 The American Physical Society