Abstract
We reconsider the QCD predictions for the radiative decay B → γℓνℓ with an energetic photon in the final state by taking into account the 1/Eγ, 1/mb power-suppressed hard-collinear and soft corrections from higher-twist B-meson light-cone distribution amplitudes (LCDAs). The soft contribution is estimated through a dispersion relation and light-cone QCD sum rules. The analysis of theoretical uncertainties and the dependence of the decay form factors on the leading-twist LCDA ϕ+(ω) shows that the latter dominates. The radiative leptonic decay is therefore well suited to constrain the parameters of ϕ+(ω), including the first inverse moment, 1/λB, from the expected high-statistics data of the BELLE II experiment.
Highlights
JHEP07(2018)154 where the spectator partons in the B meson carry an anomalously small momentum fraction ω Λ
We resort to the light-cone sum rule technique [11], which expresses the contribution of the endpoint region in the partonic calculation through a dispersion relation in terms of hadronic resonance parameters and B-meson light-cone distribution amplitudes (LCDAs)
This technique was originally applied to the analogous problem for the γγ∗ → π0 form factor [12, 13] and for the problem at hand in [14] in the tree-level and leading-twist approximation for the B-meson LCDAs
Summary
JHEP07(2018)154 where the spectator partons in the B meson carry an anomalously small momentum fraction ω Λ. We perform an extensive analysis of the model dependence by quantifying the uncertainty through different families of B-meson LCDA models with a consistent implementation of the equation-of-motion constraints. Taken together, this results in a more reliable assessment of the potential of radiative leptonic decay for determining the inverse-moment parameter λB than in previous work [9, 15]. The terms proportional to pμ contract to zero with the photon polarization vector, see [9] for more details
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