On The Expected Photon Spectrum in B -> X_s + gamma and Its Uses

Abstract

Measuring the photon energy spectrum in radiative B decays provides essential help for gaining theoretical control over semileptonic B transitions. The hadronic recoil mass distribution in B -> X_u \ellνpromises the best environment for determining |V_ub|. The theoretical uncertainties are largest in the domain of low values of the lepton pair mass q^2. Universality relations allow to describe this domain reliably in terms of the photon spectrum in B -> X_s + γ. A method is proposed to incorporate 1/m_b corrections into this relation. The low-E_γtail in radiative decays is important in the context of extracting |V_ub|. We argue that CLEO's recent fit to the spectrum underestimates the fraction of the photon spectrum below 2 GeV. Potentially significant uncertainties enter in the theoretical evaluation of the integrated end-point lepton spectrum or the B -> X_u \ellνwidth with a too high value of the lower cut on q^2 in alternative approaches to |V_ub|.

24 pages, 6 figures, LaTeX. Revised: Complete version. Numerical predictions are improved and the estimate for the decay fraction revised. The theoretical expectations for the decay fraction and the spectrum itself are given on the plots

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Cited by in corpus (14)

• Factorization and Shape-Function Effects in Inclusive B-Meson Decays
• An inclusive measurement of the photon energy spectrum in b->s gamma decays
• Renormalization-Group Improved Calculation of the B->Xs+gamma Branching Ratio
• Inclusive semileptonic B decays and the determination of |V_ub|
• B, D and K decays
• Measurements of the B -> X_s gamma Branching Fraction and Photon Spectrum from a Sum of Exclusive Final States
• Measurement of Inclusive Radiative B-meson Decays with a Photon Energy Threshold of 1.7 GeV
• The photon energy spectrum in B-> X_s + γin perturbative QCD through O(α_s^2)
• On the photon energy moments and their `bias' corrections in B -> X_s+γ
• Radiative and semi-leptonic B-meson decay spectra: Sudakov resummation beyond logarithmic accuracy and the pole mass
• Experimental Limits on Weak Annihilation Contributions to b -->u ell nu Decay
• Status of SM calculations of b > s transitions
• On Extracting Heavy Quark Parameters from Moments with Cuts
• Electro-Weak Penguin and Leptonic Decays in BaBar