B → Dℓνℓ form factors beyond leading power and extraction of |Vcb| and R(D)

Abstract

We investigate the subleading-power corrections to the exclusive B → Dℓνℓ form factors at mathcal{O} ( {alpha}_s^0 ) in the light-cone sum rules (LCSR) framework by including the two- and three-particle higher-twist contributions from the B-meson light-cone distribution amplitudes up to the twist-six accuracy, by taking into account the subleading terms in expanding the hard-collinear charm-quark propagator, and by evaluating the hadronic matrix element of the subleading effective current . Employing further the available leading-power results for the semileptonic B → D form factors at the next-to- leading-logarithmic level and combining our improved LCSR predictions with the recent lattice determinations, we then carry out a comprehensive phenomenological analysis on the semi-leptonic B → Dℓνℓ decay. We extract left|{V}_{cb}right|=left({40.2}_{-0.5}^{+0.6}{left|{{}_{mathrm{th}}}_{-1.4}^{+1.4}right|}_{mathrm{exp}}right)times {10}^{-3}left(left|{V}_{cb}right|=left({40.9}_{-0.5}^{+0.6}{left|{{}_{mathrm{th}}}_{-1.0}^{+1.0}right|}_{mathrm{exp}}right)times {10}^{-3}right) using the BaBar (Belle) experimental data, and particularly obtain for the gold-plated ratio R(D) = 0.302 ± 0.003.