QCD CORRECTIONS TO HIGGS BOSON DECAYS

Abstract

The two--loop $\mathcal{O}({\alpha }_s{G}_F{m}_t^2)$ corrections to the $b\bar{b}$ decay rate of the Standard Model Higgs boson as well as its production via $e^{+}{e}^{-}\to ZH$ will be presented. These QCD corrections are obtained by using a low-energy theorem for light Higgs bosons compared to the top quark mass. The results yield strong screening effects of the $\mathcal{O}(G_F{m}_t^2)$ contributions. After that the two-loop QCD corrections to the $\gamma \gamma$ and gluonic decays of the Higgs bosons of the Standard Model and its minimal supersymmetric extension are discussed. While the corrections to the $\gamma \gamma$ decays remain small of $\mathcal{O}({\alpha }_s)$ they are huge $\sim$ 50 -- 70 \% in the case of the gluonic decays.

16 pages, latex, 9 figures appended as uuencoded file