Two-loop $O(N_f��_s^2)$ correction to the decay width of the Higgs boson to two massive fermions

We present an analytical calculation of additional real or virtual radiation of the light fermion pair in the fermionic decay of the Higgs boson $ H \to f_1\bar f_1$ for arbitrary ratios of the Higgs boson mass to the $f_1$ fermion mass. This result gives us a value of the $O(N_f ��_s^2)$ radiative correction to the inclusive decay rate $ H \to f_1\bar f_1$. Using this result in the framework of the Brodsky-Mackenzie-Lepage scheme, we discuss the scale setting in the one-loop QCD correction to the decay width $ H \to f_1\bar f_1$ for arbitrary relation between the Higgs boson and fermion masses.
Latex, 18 pages, 4 uuencoded figures, some misprints in formulas are corrected