Exclusive $B\to V\gamma$ decays in the T2HDM

Abstract

By employing the QCD factorization approach for the exclusive $B\to V\gamma$ decays, we calculated the new physics contributions to the branching ratios, CP asymmetries, isospin and U-spin symmetry breaking of $B\to K^{\ast }\gamma$ and $B\to \rho \gamma$ decays, induced by the charged Higgs penguin diagrams appeared in the top-quark two-Higgs-doublet model(T2HDM). Within the considered parameter space, we found that (a) a charged-Higgs boson with a mass larger than 300 GeV are always allowed by the date of $B\to V\gamma$ decay, and such lower limit on $\text{mhp}$ are comparable with those obtained from the inclusive $B\to X_s\gamma$ decay; (b) the CP asymmetry of $B\to \rho \gamma$ in the T2HDM can be as large as 10% in magnitude and has a strong dependence on the angle $\theta$ and the CKM angle $\gamma$; (c) the isospin symmetry breakings of $B\to V\gamma$ decays in the T2HDM are generally small in size: around 6% for $B\to K^{\ast }\gamma$ decay and less than 20% for $B\to \rho \gamma$ decay; and (d) the U-spin symmetry breaking $\Delta U(K^{\ast },\rho )$ in the T2HDM is also small in size, only about 8% of the branching ratio $\text{calb}(B\to {\rho }^0\gamma )$.

Comments: RevTex file, 25 pages, 12 eps figures