Measurement of ℬ(B → Χ_sγ), the B → Χ_sγ Photon Energy Spectrum, and the Direct CP Asymmetry in B → Χ_{s+d}γ Decays.

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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 ± 4.2) x 10⁶ e⁺e⁻ → Υ(4S) → BB̅ 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 ± 0.15 ± 0.29 ± 0.08) x 10⁻⁴ and the first, second, and third moments E{γ} = 2.267 ± 0. 019 ± 0.032 ± 0.003 GeV, <(E{γ}) -- <E{γ}}>)² = 0.0484 ± 0.0053 ± 0.0077 ± 0.0005 GeV², and <(E{γ}) -- <E{γ}}>)³ = -0.0048 ± 0.0011 ± 0.0011± 0.0004 GeV3, 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 ± 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.

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Keywords

Standard model (Nuclear physics), Quantum chromodynamics, Supersymmetry

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Rights

©2012 American Physical Society

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