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Measurement of B (B→Xsγ), the B→X sγ photon energy spectrum, and the direct CP asymmetry in B→Xs+dγ decays

Abstract

The photon spectrum in B→Xs γ decay, where X s is any strange hadronic state, is studied using a data sample of (382.8±4.2)×106 e+e-→Υ(4S)→BB events collected by the BABAR experiment at the PEP-II collider. The spectrum is used to measure the branching fraction B(B→Xsγ)=(3. 21±0.15±0.29±0.08)×10-4 and the first, second, and third moments YEγ Ÿ ;=2.267±0. 019±0.032±0.003 GeV, Y(Eγ-YEγ Ÿ) 2Ÿ=0.0484±0.0053±0.0077±0.0005 GeV2, and Y(Eγ-YEγ Ÿ) 3Ÿ=-0.0048±0. 0011±0.0011±0.0004 GeV3, for the range Eγ>1.8 GeV, where Eγ is the photon energy in the B-meson rest frame. Results are also presented for narrower Eγ ranges. In addition, the direct CP asymmetry ACP(B→Xs+dγ) is measured to be 0.057±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. © 2012 American Physical Society.

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