Photon Energy Spectrum in B → Xs + γ and comparison with Data
Abstract A comparison of the inclusive photon energy spectrum in the radiative decay B → X S + γ , measured recently by the CLEO Collaboration, with the standard model is presented, using a B -meson wave function model and improving earlier perturbative QCD-based computations of the same. The dependence of the photon energy spectrum on the non-perturbative model parameters, p F , the b -quark Fermi momentum in the B hadron, and m q , the spectator quark mass, is explicitly shown, allowing a comparison of these parameters with the ones obtained from the analysis of the lepton energy spectrum in semileptonic B decays. Taking into account present uncertainties, we estimate BR( B → X s + γ ) = (2.55 ± 1.28) × 10 −4 in the standard model, assuming |V ts | |V cb | = 1.0 . Comparing this with the CLEO measurement BR( B → X s + γ ) = (2.32±0.67) × 10 −4 implies |V ts | |V cb | = 1.1 ± 0.43 , in agreement with the CKM unitarity.