paper

Measurement of B(B-->X_s γ), the B-->X_s γ photon energy spectrum, and the direct CP asymmetry in B-->X_{s+d} γ decays

arXiv:1207.5772 · doi:10.1103/PhysRevD.86.112008

Abstract

The photon spectrum in B --> X_s γ decay, where X_s is any strange hadronic state, is studied using a data sample of (382.8\pm 4.2) \times 10^6 e^+ e^- --> Υ(4S) --> BBbar events collected by the BABAR experiment at the PEP-II collider. The spectrum is used to measure the branching fraction B(B --> X_s γ) = (3.21 \pm 0.15 \pm 0.29 \pm 0.08)\times 10^{-4} and the first, second, and third moments <E_γ> = 2.267 \pm 0.019 \pm 0.032 \pm 0.003 GeV,, <(E_γ- <E_γ>)^2> = 0.0484 \pm 0.0053 \pm 0.0077 \pm 0.0005 GeV^2, and <(E_γ- <E_γ>)^3> = -0.0048 \pm 0.0011 \pm 0.0011 \pm 0.0004 GeV^3, for the range E_γ> 1.8 GeV, where E_γ is the photon energy in the B-meson rest frame. Results are also presented for narrower E_γ ranges. In addition, the direct CP asymmetry A_{CP}(B --> X_{s+d} γ) is measured to be 0.057 \pm 0.063. The spectrum itself is also unfolded to the B-meson rest frame; that is the frame in which theoretical predictions for its shape are made.

37 pages, 19 postscript figures, submitted to Phys. Rev. D. No analysis or results have changed from previous version. Some changes to improve clarity based on interactions with Phys. Rev. D referees, including one new Figure (Fig. 13), and some minor wording/punctuation/spelling mistakes fixed

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