Two-loop electroweak correction of O(GFMt2) to the Higgs-boson decay into photons

We compute the dominant two-loop electroweak correction, of O(G(F)M(t)(2)), to the partial width of the decay of an intermediate-mass Higgs boson into a pair of photons. We use the asymptotic-expansion technique in order to extract the leading dependence on the top-quark mass plus four expansion terms that describe the dependence on the W- and Higgs-boson masses. This correction reduces the Born result by approximately 2.5%. As a by-product of our analysis, we also recover the O(G(F)M(t)(2)) correction to the partial width of the Higgs-boson decay to two gluon jets. (C) 2004 Elsevier B.V. All rights reserved.