We reconsider the QCD predictions for the radiative decay B → γ ν with an energetic photon in the final state by taking into account the 1/E γ , 1/m b 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/λ B , from the expected high-statistics data of the BELLE II experiment.

We present a systematic study of higher-twist distribution amplitudes (DAs) of the B-meson which give rise to power-suppressed 1/m B contributions to B-decays in final states with energetic light particles in the framework of QCD factorization. As the main result, we find that the renormalization group equations for the three-particle distributions are completely integrable in the large N c limit and can be solved exactly. General properties of the solutions are studied. We propose simple models for higher-twist DAs which satify all existing constraints and can be used in phenomenological studies.

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We address the question of interpolation of the virtual Compton scattering process off a polarized nucleon target between the deeply virtual regime for the initial-state photon and its near on-shell kinematics making use of the photon helicity-dependent Compton Form Factors (CFFs) as a main ingredient of the formalism. The five-fold differential cross section 1 for the reaction with all possible polarization options for the lepton and nucleon spins is evaluated in terms of CFFs in the rest reference frame of the initial-state nucleon. We suggest a rather simple parametrization of the Compton hadronic tensor in terms of CFFs which are free from kinematical singularities and are directly related, at large photon virtualities, to Generalized Parton Distributions. We also provide a relation of our basis spanned by a minimal number of Dirac bilinears to the one introduced by Tarrach for the parametrization of the virtual Compton tensor and utilize the former to establish a set of equalities among our CFFs and Generalized Polarizabilities. As a complementary result, we express Compton scattering in the Born approximation in terms of CFFs as well.