O(GF2mt4) two-loop electroweak correction to Higgs-boson decay to bottom quarks

We analytically calculate the dominant two-loop electroweak correction, of O(GF2mt4), to the partial width of the decay of a Higgs boson, with mass MH<<mt, into a bottom-quark pair, and describe the most important conceptual and technical details of our calculation. As a by-product of our analysis, we also recover the O(αsGFmt2) correction. Relative to the Born result, the O(GF2mt4) correction turns out to be approximately +0.047% and, thus, more than compensates the O(αsGFmt2) one, which amounts to approximately -0.022%