Two-loop O( alpha sGFmt2) corrections to the fermionic decay rates of the standard-model Higgs boson.

Abstract

Low- and intermediate-mass Higgs bosons decay preferably into fermion pairs. The one-loop electroweak corrections to the respective decay rates are dominated by a flavor-independent term of O(${\mathit{G}}_{\mathit{F}}$${\mathit{m}}_{\mathit{t}}^{2}$). We calculate the two-loop gluon correction to this term. It turns out that this correction screens the leading high-${\mathit{m}}_{\mathit{t}}$ behavior of the one-loop result by roughly 10%. We also present the two-loop QCD correction to the contribution induced by a pair of fourth-generation quarks with arbitrary masses. As expected, the inclusion of the QCD correction considerably reduces the renormalization-scheme dependence of the prediction.