{
  "abstract": "We test lepton flavor universality with a measurement of the branching-fraction ratios $R(D^{(*)}) \\equiv \\mathcal{B}(\\bar{B} \\rightarrow D^{(*)} τ^{-} \\barν_τ)/\\mathcal{B}(\\bar{B} \\rightarrow D^{(*)} \\ell^{-} \\barν_{\\ell})$, where $\\ell$ denotes an electron or muon. The analysis uses $387\\times 10^6$ $Υ(\\mathrm{4S})$ decays collected with the Belle II detector in energy-asymmetric $e^+e^-$ collisions. One $B$ meson is fully reconstructed in a hadronic decay mode, while the other is reconstructed either in $\\bar{B}\\rightarrow D^{(*)}τ^{-}\\barν_τ$, with $τ^- \\rightarrow \\ell^- \\barν_{\\ell}ν_τ$, or in $\\bar{B}\\rightarrow D^{(*)}\\ell^{-}\\barν_{\\ell}$. We extract the signal from the distributions of the residual calorimeter energy and the squared mass of the undetected particles, obtaining $R(D^{*}) = 0.242 \\pm0.019(\\mathrm{stat}) \\pm0.016(\\mathrm{syst})$ and $R(D) = 0.439 \\pm 0.055(\\mathrm{stat}) \\pm 0.046(\\mathrm{syst})$. These results are consistent with both the standard model predictions and previous measurements, and constitute the most precise determination of $R(D^{(*)})$ with hadronic tagging.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.21947",
  "author_total": 498,
  "authors": [
    {
      "name": "Belle II Collaboration"
    },
    {
      "name": "M. Abumusabh"
    },
    {
      "name": "I. Adachi"
    },
    {
      "name": "K. Adamczyk"
    },
    {
      "name": "A. Aggarwal"
    },
    {
      "name": "L. Aggarwal"
    },
    {
      "name": "H. Ahmed"
    },
    {
      "name": "Y. Ahn"
    },
    {
      "name": "H. Aihara"
    },
    {
      "name": "M. Akdag"
    },
    {
      "name": "N. Akopov"
    },
    {
      "name": "A. Akram"
    },
    {
      "name": "S. Alghamdi"
    },
    {
      "name": "M. Alhakami"
    },
    {
      "name": "A. Aloisio"
    },
    {
      "name": "N. Althubiti"
    },
    {
      "name": "K. Amos"
    },
    {
      "name": "M. Angelsmark"
    },
    {
      "name": "N. Anh Ky"
    },
    {
      "name": "C. Antonioli"
    },
    {
      "name": "K. Arai"
    },
    {
      "name": "D. M. Asner"
    },
    {
      "name": "H. Atmacan"
    },
    {
      "name": "T. Aushev"
    },
    {
      "name": "V. Aushev"
    },
    {
      "name": "R. Ayad"
    },
    {
      "name": "V. Babu"
    },
    {
      "name": "H. Bae"
    },
    {
      "name": "N. K. Baghel"
    },
    {
      "name": "S. Bahinipati"
    },
    {
      "name": "P. Bambade"
    },
    {
      "name": "Sw. Banerjee"
    },
    {
      "name": "S. Bansal"
    },
    {
      "name": "M. Barrett"
    },
    {
      "name": "M. Bartl"
    },
    {
      "name": "J. Baudot"
    },
    {
      "name": "A. Baur"
    },
    {
      "name": "A. Beaubien"
    },
    {
      "name": "F. Becherer"
    },
    {
      "name": "J. Becker"
    },
    {
      "name": "J. V. Bennett"
    },
    {
      "name": "F. U. Bernlochner"
    },
    {
      "name": "V. Bertacchi"
    },
    {
      "name": "M. Bertemes"
    },
    {
      "name": "E. Bertholet"
    },
    {
      "name": "M. Bessner"
    },
    {
      "name": "S. Bettarini"
    },
    {
      "name": "V. Bhardwaj"
    },
    {
      "name": "B. Bhuyan"
    },
    {
      "name": "F. Bianchi"
    },
    {
      "name": "T. Bilka"
    },
    {
      "name": "A. Biswas"
    },
    {
      "name": "D. Biswas"
    },
    {
      "name": "A. Bobrov"
    },
    {
      "name": "D. Bodrov"
    },
    {
      "name": "A. Bondar"
    },
    {
      "name": "G. Bonvicini"
    },
    {
      "name": "J. Borah"
    },
    {
      "name": "A. Boschetti"
    },
    {
      "name": "A. Bozek"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3khpdb4hgemtz.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.21947",
  "fulltext_url": null,
  "id": "3khpdb4hgemtz",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.21947",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "hep-ex"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.21947",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3khpdb4hgemtz.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:03Z",
      "native_id": "2609.21947",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.21947"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "Test of lepton flavor universality with $\\bar{B} \\rightarrow D^{(*)} τ^{-} \\barν_τ$ and $\\bar{B} \\rightarrow D^{(*)} \\ell^{-} \\barν_{\\ell}$ decays at Belle II",
  "title_text": "Test of lepton flavor universality with B̅ → D^(*) τ^− ν̅_τ and B̅ → D^(*) ℓ^− ν̅_ℓ decays at Belle II",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:03Z",
  "url": "https://research.draconitic.com/paper/3khpdb4hgemtz",
  "venue": "arXiv",
  "versions": []
}