Precision Measurement of the B→X_sγ Photon Energy Spectrum, Branching Fraction, and Direct CP Asymmetry A_{CP}(B→X_{s+d}γ)

The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B→X_sγ plus B→X_dγ, is studied using a data sample of (382.8 ± 4.2)×10⁶Υ(4S) →BB̄ decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction ℬ(B→X_sγ)=(3. 21 ± 0.33) ×10⁻⁴ for E_γ > 1.8 GeV and the direct CP asymmetry A_{CP} (B→X_{s+d}γ)=0. 057 ± 0.063. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame.