Γ(H→bb¯) to order ααs

We compute the decay rate of the Standard Model Higgs boson to bottom quarks to order ααsααs. We apply the optical theorem and calculate the imaginary part of three-loop corrections to the Higgs boson propagator using asymptotic expansions in appropriately chosen mass ratios. The corrections of order ααsααs are of the same order of magnitude as the O(αs3) QCD corrections but have the opposite sign.