Measurement of the B→Xsγ branching fraction and photon energy spectrum using the recoil method

Abstract

We present a measurement of the branching fraction and photon-energy spectrum for the decay B→Xsγ using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of 210fb-1, from which approximately 680000 BB̄ events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high-energy photon is identified. We measure B(B→Xsγ)=(3. 66±0.85stat±0.60syst)×10-4 for photon energies Eγ above 1.9GeV in the B rest frame. From the measured spectrum we calculate the first and second moments for different minimum photon energies, which are used to extract the heavy-quark parameters mb and μπ2. In addition, measurements of the direct CP asymmetry and isospin asymmetry are presented. © 2008 The American Physical Society.