1/mQcorrections to form factors and extraction of|Vcb|

Abstract

Form factors for ${0}^{\ensuremath{-}}\ensuremath{\rightarrow}{0}^{\ensuremath{-}}$ and ${0}^{\ensuremath{-}}\ensuremath{\rightarrow}{1}^{\ensuremath{-}}$ mesonic transitions in the heavy quark limit and the ${1/m}_{Q}$ corrections are analyzed model independently within the Bethe-Salpeter (BS) formalism. The analysis shows that the BS formalism has spin-flavor symmetry in the heavy quark limit and respects Luke's theorem when the ${1/m}_{Q}$ corrections are taken into account. All form factors for $B\ensuremath{\rightarrow}{D}^{(*)}$ transitions beyond the zero recoil point are estimated in a relativistic constituent quark model based on the BS formalism. Using these form factors we calculate the branching ratios for the semileptonic decays $B\ensuremath{\rightarrow}{D}^{(*)}{l}^{+}{\ensuremath{\nu}}_{l}$ and extract the Cabibbo-Kobayashi-Maskawa matrix element ${|V}_{\mathrm{cb}}|.$ We get ${|V}_{\mathrm{cb}}|=0.042\ifmmode\pm\else\textpm\fi{}0.003$ which is consistent with the current world average.