# Measurement of the Branching Fraction and Photon Energy Moments of $B \to X_s \gamma$ and $A_{cp}(B \to X_{s+d} \gamma)$

Abstract : The photon spectrum in B -> X_s gamma decay, where X_s 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 -> X_s gamma)=(3.67 +- 0.29(stat.) +- 0.34(sys.) +- 0.29(model)) times 10^-4, the first moment =2.288 +- 0.025 +- 0.017 +- 0.015 GeV and the second moment - ^2 =0.0328 +- 0.0040 +- 0.0023 +- 0.0036 GeV^2 are measured for the photon energy range 1.9 GeV < E_gamma < 2.7 GeV. They are also measured for narrower E_gamma ranges. The moments are then fit to recent theoretical calculations to extract the Heavy Quark Expansion parameters, m_b and mu_pi^2, and to extrapolate the partial branching fraction to E_gamma>1.6 GeV. In addition, the direct CP asymmetry A_CP(B -> X_(s+d) gamma) is measured to be -0.110 +- 0.115(stat.) +- 0.017(sys.).
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Submitted on : Tuesday, January 16, 2007 - 3:58:28 PM
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### Citation

B. Aubert, R. Barate, M. Bona, D. Boutigny, F. Couderc, et al.. Measurement of the Branching Fraction and Photon Energy Moments of $B \to X_s \gamma$ and $A_{cp}(B \to X_{s+d} \gamma)$. Physical Review Letters, American Physical Society, 2006, 97, pp.171803. ⟨10.1103/PhysRevLett.97.171803⟩. ⟨in2p3-00113845⟩

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