Two-loop electroweak heavy-fermion corrections to Higgs-boson production and decay

Abstract

The dominant electroweak corrections to the production cross sections and partial decay widths of a light Standard Model Higgs boson, with mass M H ⪡ 2 m t , are due to top-quark loops. By means of a low-energy theorem, we study at the two-loop level the leading shifts in the Higgsboson couplings to pairs of light fermions and gauge bosons induced by a sequential isodoublet of high-mass fermions. For tree-level and loop-induced Higgs-boson couplings, these corrections are of relative order O( G μ 2 m F 4)) and O( G μ m F 2), respectively, where m F represents a generic heavy-fermion mass, with m F ⪢ M W , M H . Except for the Hbb coupling, all results carry over to the case of the top-quark-induced corrections. We discuss possible phenomenological consequences of our results.