The photon energy spectrum in B ? X s + ? in perturbative QCD through O ( a s 2 )

Abstract We derive the dominant part of the O ( α s 2 ) correction to the photon energy spectrum in the inclusive decay B → X s + γ . The detailed knowledge of the spectrum is important for relating the theoretical calculations of the B → X s + γ decay rate and the experimental measurements where a cut on the photon energy is applied. In addition, moments of the photon energy spectrum are used for the determination of the b-quark mass and other fundamental parameters of heavy quark physics. Our calculation reduces the theoretical uncertainty associated with uncalculated higher orders effects and shows that, for B → X s + γ , QCD radiative corrections to the photon energy spectrum are under theoretical control.

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