$O({\alpha }^2{G}_F{m}_t^2)$ Contributions to $H\to \gamma \gamma$

Abstract

The rare decay $H\to \gamma \gamma$ is a promising detection channel for an intermediate mass Higgs boson. We compute its two-loop $O({\alpha }^2{G}_F{m}_t^2)$ correction in the standard model and find that the relative correction to the decay rate runs between $0.7$ and $0.5$ for $M_H=80-150$ GeV. The analogous correction to the amplitude for $gg\to H$ is recovered as a special case. The generalization of our result to other models is also briefly indicated.

Comments: latex, 2 figures using axodraw style. Revised version corrects for calculational errors and incudes some details