Measurement of the Branching Fraction and Photon Energy Moments of B->Xs gamma and Acp(B->X(s+d) gamma)
Abstract
The photon spectrum in B -> Xs gamma decay, where Xs is any strange hadronic state, is studied using a data sample of 88.5 million e+e- -> Upsilon(4S) -> BBbar decays collected by the BaBar experiment at SLAC. The partial branching fraction, Delta B(B -> Xs gamma)=(3.67 +- 0.29(stat.) +- 0.34(sys.) +- 0.29(model)) times 10-4, the first moment <Egamma>=2.288 +- 0.025 +- 0.017 +- 0.015 GeV and the second moment <Egamma2> - <Egamma>2 =0.0328 +- 0.0040 +- 0.0023 +- 0.0036 GeV2 are measured for the photon energy range 1.9 GeV < Egamma < 2.7 GeV. They are also measured for narrower Egamma ranges. The moments are then fit to recent theoretical calculations to extract the Heavy Quark Expansion parameters, mb and mupi2, and to extrapolate the partial branching fraction to Egamma>1.6 GeV. In addition, the direct CP asymmetry ACP(B -> X(s+d) gamma) is measured to be -0.110 +- 0.115(stat.) +- 0.017(sys.).
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