Sensitivity of Two-Loop Corrections to Muon Decay to the Higgs-Boson Mass

The Higgs-mass dependence of the two-loop contributions to muon decay is analyzed at the two-loop level. Exact results are given for the Higgs-dependent two-loop corrections associated with the fermions, i.e. no expansion in the top-quark and the Higgs-boson mass is made. The remaining theoretical uncertainties in the Higgs-mass dependence of $\mathrm{\Delta }r$ are discussed.