Determination of $|V_{cb}|$ using $overline{B}^0to D^{*+}ell^-barĪ½_ell$ decays with Belle II

Kavli Affiliate: T. Higuchi

| First 5 Authors: Belle II Collaboration, I. Adachi, K. Adamczyk, L. Aggarwal, H. Aihara

| Summary:

We determine the CKM matrix-element magnitude $|V_{cb}|$ using
$overline{B}^0to D^{*+}ell^-barnu_ell$ decays reconstructed in $189 ,
mathrm{fb}^{-1}$ of collision data collected by the Belle II experiment,
located at the SuperKEKB $e^+e^-$ collider. Partial decay rates are reported as
functions of the recoil parameter $w$ and three decay angles separately for
electron and muon final states. We obtain $|V_{cb}|$ using the
Boyd-Grinstein-Lebed and Caprini-Lellouch-Neubert parametrizations, and find
$|V_{cb}|_mathrm{BGL}=(40.57pm 0.31 pm 0.95pm 0.58)times 10^{-3}$ and
$|V_{cb}|_mathrm{CLN}=(40.13 pm 0.27 pm 0.93pm 0.58 )times 10^{-3}$ with
the uncertainties denoting statistical components, systematic components, and
components from the lattice QCD input, respectively. The branching fraction is
measured to be ${cal B}(overline{B}^0to D^{*+}ell^-barnu_ell)=(4.922 pm
0.023 pm 0.220)%$. The ratio of branching fractions for electron and muon
final states is found to be $0.998 pm 0.009 pm 0.020$. In addition, we
determine the forward-backward angular asymmetry and the $D^{*+}$ longitudinal
polarization fractions. All results are compatible with lepton-flavor
universality in the Standard Model.

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