Perturbative corrections to B [right arrow] D form factors in QCD

Abstract

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We compute perturbative QCD corrections to B [right arrow] D form factors at leading power in [Lambda]/m ^sub b ^, at large hadronic recoil, from the light-cone sum rules (LCSR) with B-meson distribution amplitudes in HQET. QCD factorization for the vacuum-to-B-meson correlation function with an interpolating current for the D-meson is demonstrated explicitly at one loop with the power counting scheme ....... The jet functions encoding information of the hard-collinear dynamics in the above-mentioned correlation function are complicated by the appearance of an additional hard-collinear scale m ^sub c ^, compared to the counterparts entering the factorization formula of the vacuum-to-B-meson correction function for the construction of B [right arrow] [pi] from factors. Inspecting the next-to-leading-logarithmic sum rules for the form factors of B [right arrow] Dν indicates that perturbative corrections to the hard-collinear functions are more profound than that for the hard functions, with the default theory inputs, in the physical kinematic region. We further compute the subleading power correction induced by the three-particle quark-gluon distribution amplitudes of the B-meson at tree level employing the background gluon field approach. The LCSR predictions for the semileptonic B [right arrow] Dν form factors are then extrapolated to the entire kinematic region with the z-series parametrization. Phenomenological implications of our determinations for the form factors f ^sub BD ^ ^sup +,0^ (q ^sup 2^) are explored by investigating the (differential) branching fractions and the R(D) ratio of B [right arrow] Dν and by determining the CKM matrix element |V ^sub cb ^ | from the total decay rate of B [right arrow] D[mu]ν ^sub [mu] ^.