$B\to X_s\gamma$ and $B\to K^{\ast }\gamma$ in the standard and 2H models

Abstract

Theoretical predictions for the branching ratios of the $B\to X_s\gamma$ and $B\to K^{\ast }\gamma$ decays are calculated in the Standard Model and in the (type II) two-Higgs-doublet model. Both the complete leading and the partially known next-to-leading order QCD corrections are included. The uncertainties due to the regularization scheme dependence introduced by the incomplete NLO terms are discussed. The results are compared with the recent CLEO II measurements and a new lower limit on the charged Higgs boson mass, $M_{H^{\pm }}>\sim 200$ GeV, is obtained.

Comments: (talk given at ICHEP '94), 2 pp (figures not included), LaTeX, INFN-ISS 94/9 (October 1994)