B→Xsγγdecay in the standard model and the general two-Higgs-doublet model

Abstract

Based on the low-energy effective Hamiltonian, we calculate the new physics corrections to the branching ratio and the differential distributions of the rare decay $B \to X_s \gamma \gamma$ induced by the new gluonic and electroweak charged-Higgs penguin diagrams in the general two-Higgs-doublet model with the restriction $\lambda_{ij}^{U,D}=0$ for $i\neq j$. Within the considered parameter space, we see the following: (a) the standard model predictions of ${\cal B}(B \to X_s \gamma \gamma)$ and $A_{FB}$ have a moderate $m_s$ dependence; (b) in model III, the prediction of the branching ratio ${\cal B}(B \to X_s \gamma \gamma)$ ranges from one third to three times of the standard model prediction, but is highly correlated with that of ${\cal}(B \to X_s \gamma)$; (c) the new physics enhancement to the branching ratio ${\cal B}(B \to X_s \gamma \gamma)$ in model II can be as large as $(30-50)%$; (d) the contribution from 1PR diagrams is dominant and hence four normalized differential distributions are insensitive to the variation of scale $\mu$ and possible new physics corrections; (e) due to the smallness of its decay rate and the long-distance background, the $B \to X_s \gamma \gamma$ decay is not a better process in detecting new physics than the $B \to X_s \gamma$ decay.