Corrections of O(α_s^2) to the Decay of an Intermediate-Mass Higgs Boson into Two Photons

Abstract

The QCD correction of $O(α_s^2)$ to the decay of the Standard Model Higgs boson into two photons is presented. We consider the contribution coming from diagrams with a heavy top quark as virtual particle. The first three terms of the expansion in the inverse top mass is calculated. Expressing the result through the on-shell top mass M_t, we find large coefficients for the power-suppressed terms whereas in the $\overline{MS}$ scheme the coefficients are tiny.

Figures (4)

• Figure 1: One- and two-loop corrections to the amplitude $A_t$. Successively higher orders in $\tau_t$ are included. Dotted line: leading order result, dashed line: on-shell scheme; dash-dotted line: $\overline{\hbox{MS}}$ scheme, full line: exact result. The two vertical lines indicate $M_H=M_W$ and $M_H=2M_W$, respectively.
• Figure 2: Tadpole diagrams relevant for the method based on the Fock-Schwinger gauge. The diagram with a second light quark loop and the one containing the ghost particle are not displayed.
• Figure 3: Typical Feynman diagrams contributing to $H\to\gamma\gamma$.
• Figure 4: ${\cal O}(\alpha_s^2)$ corrections to $H\to\gamma\gamma$. The same notation is adopted as in Fig. \ref{['fig12']}.