Precision Measurement of the B to X_s γPhoton Energy Spectrum, Branching Fraction, and Direct CP Asymmetry A_{CP}(B to X_{s+d}γ

Abstract

The photon spectrum in the inclusive electromagnetic radiative decays of the $B$ meson, $B\to X_s\gamma$ plus $B\to X_d\gamma$, is studied using a data sample of $(382.8\pm 4.2)\times 10^6$ $Υ(4S) \to B\overli\ ne{B}$ decays collected by the \babar\ experiment at SLAC. The spectrum is used to extract the branching fraction $\mathcal{B}(B\to X_s\gamma )=(3.21\pm 0.33)\times 10^{-4}$ for $E_γ>1.8 \gev$ and the direct CP asymmetry $A_{CP}(B\to X_{s+d}\gamma )=0.057\pm 0.063$. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the $B$ meson rest frame.

8 pages, 2 figures, submitted to PRL