Determination of $|V_{cb}|$ using $\bar{B}{}^0 \to D^{*+} \ell^{\mathstrut -} \bar{\nu}{}_{\ell}$ decays with Belle II

Abstract We determine the CKM matrix-element magnitude $|V_{cb}|$ using $\overline{B}^0\to D^{*+}\ell^-\bar\nu_\ell$ 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 $|V_{cb}|_\mathrm{BGL}=(40.57\pm 0.31 \pm 0.95\pm 0.58)\times 10^{-3}$ and $|V_{cb}|_\mathrm{CLN}=(40.13 \pm 0.27 \pm 0.93\pm 0.58 )\times 10^{-3}$ with the uncertainties denoting statistical components, systematic components, and components from the lattice QCD input, respectively. The branching fraction is measured to be ${\cal B}(\overline{B}^0\to D^{*+}\ell^-\bar\nu_\ell)=(4.922 \pm 0.023 \pm 0.220)\%$. 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.
Tags
Working group Semileptonic and Missing Energy Decay
Principal authors @  Florian Bernlochner, Lu Cao, Chaoyi Lyu, Christoph Schwanda
Reference Phys.Rev.D 108, 092013 (2023), DOI: 10.1103/PhysRevD.108.092013
Document BELLE2-PUB-PH-2023-024
Links arXiv:2310.01170, Inspire, PRD
Bibtex 
@article{Belle-II:2023okj,
    author = "Adachi, I. and others",
    collaboration = "Belle-II",
    title = "{Determination of |Vcb| using B{\textasciimacron}0{\textrightarrow}D*+{\ensuremath{\ell}}{\ensuremath{-}}{\ensuremath{\nu}}{\textasciimacron}{\ensuremath{\ell}} decays with Belle II}",
    eprint = "2310.01170",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2023-014, KEK Preprint 2023-28",
    doi = "10.1103/PhysRevD.108.092013",
    journal = "Phys. Rev. D",
    volume = "108",
    number = "9",
    pages = "092013",
    year = "2023"
}