B → Dℓν ℓ form factors beyond leading power and extraction of |V cb | and R(D)

Abstract

Abstract We investigate the subleading-power corrections to the exclusive B → Dℓν ℓ form factors at O $$ \mathcal{O} $$ ( α s 0 $$ {\alpha}_s^0 $$ ) 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 → Dℓν ℓ decay. We extract V cb = 40.2 − 0.5 + 0.6 th − 1.4 + 1.4 exp × 10 − 3 V cb = 40.9 − 0.5 + 0.6 th − 1.0 + 1.0 exp × 10 − 3 $$ \left|{V}_{cb}\right|=\left({40.2}_{-0.5}^{+0.6}{\left|{{}_{\mathrm{th}}}_{-1.4}^{+1.4}\right|}_{\mathrm{exp}}\right)\times {10}^{-3}\left(\left|{V}_{cb}\right|=\left({40.9}_{-0.5}^{+0.6}{\left|{{}_{\mathrm{th}}}_{-1.0}^{+1.0}\right|}_{\mathrm{exp}}\right)\times {10}^{-3}\right) $$ using the BaBar (Belle) experimental data, and particularly obtain for the gold-plated ratio R(D) = 0.302 ± 0.003.

Keywords

• NLO Computations
• QCD Phenomenology