Measurement of differential distributions of B→D*ℓν¯ℓ and implications on |Vcb|

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Abstract

We present a measurement of the differential shapes of exclusive $B\ensuremath{\rightarrow}{D}^{*}\ensuremath{\ell}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ ($B={B}^{\ensuremath{-}},{\overline{B}}^{0}$ and $\ensuremath{\ell}=e$, $\ensuremath{\mu}$) decays with hadronic tag-side reconstruction for the full $711\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ Belle dataset. We extract the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor parameters and use an external input for the absolute branching fractions to determine the Cabibbo-Kobayashi-Maskawa matrix element and find $|{V}_{cb}{|}_{\mathrm{CLN}}=(40.2\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $|{V}_{cb}{|}_{\mathrm{BGL}}=(40.7\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ with the zero-recoil lattice QCD point $\mathcal{F}(1)=0.906\ifmmode\pm\else\textpm\fi{}0.013$. We also perform a study of the impact of beyond zero-recoil lattice QCD calculations on the $|{V}_{cb}|$ determinations. Additionally, we present the lepton-flavor universality ratio ${R}_{e\ensuremath{\mu}}=\mathcal{B}(B\ensuremath{\rightarrow}{D}^{*}e{\overline{\ensuremath{\nu}}}_{e})/\mathcal{B}(B\ensuremath{\rightarrow}{D}^{*}\ensuremath{\mu}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}})=0.993\ifmmode\pm\else\textpm\fi{}0.023\ifmmode\pm\else\textpm\fi{}0.023$, the electron and muon forward-backward asymmetry and their difference $\mathrm{\ensuremath{\Delta}}{A}_{FB}=0.028\ifmmode\pm\else\textpm\fi{}0.028\ifmmode\pm\else\textpm\fi{}0.008$, and the electron and muon ${D}^{*}$ longitudinal polarization fraction and their difference $\mathrm{\ensuremath{\Delta}}{F}_{L}^{{D}^{*}}=0.030\ifmmode\pm\else\textpm\fi{}0.025\ifmmode\pm\else\textpm\fi{}0.007$. The uncertainties quoted correspond to the statistical and systematic uncertainties, respectively.

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