First measurement of $R(X_{\tau/\ell})$ as an inclusive test of the $b \to c \tau \nu$ anomaly

Sumitted to PubDB: 2023-08-11

Category: Physics / performance paper

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Principal Authors Florian Bernlochner, Jochen Dingfelder, Henrik Junkerkalefeld, Peter Lewis, Marco Milesi, Paolo Rocchetti, Phillip Urquijo
Date 2024-05-23
Working group Semileptonic and Missing Energy Decay
Belle II Number BELLE2-PUB-PH-2023-008
Abstract We measure the tau-to-light-lepton ratio of inclusive $B$-meson branching fractions $R(X_{\tau/\ell}) \equiv \mathcal{B}(B\to X \tau \nu)/\mathcal{B}(B \to X \ell \nu)$, where $\ell$ indicates an electron or muon, and thereby test the universality of charged-current weak interactions. We select events that have one fully reconstructed $B$ meson and a charged lepton candidate from $189~\mathrm{fb}^{-1}$ of electron-positron collision data collected with the Belle II detector. We find $R(X_{\tau/\ell}) = 0.228 \pm 0.016~(\mathrm{stat}) \pm 0.036~(\mathrm{syst})$, in agreement with standard-model expectations. This is the first direct measurement of $R(X_{\tau/\ell})$.
ArXiv https://arxiv.org/abs/2311.07248
Inspire https://inspirehep.net/literature/2721845
DOI 10.1103/PhysRevLett.132.211804
Reference Phys.Rev.Lett. 132, 211804 (2024)
Bibtex 
@article{Belle-II:2023aih,
    author = "Adachi, I. and others",
    collaboration = "Belle-II",
    title = "{First Measurement of R(X{\ensuremath{\tau}}/{\ensuremath{\ell}}) as an Inclusive Test of the b{\textrightarrow}c{\ensuremath{\tau}}{\ensuremath{\nu}} Anomaly}",
    eprint = "2311.07248",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2023-016, KEK Preprint 2023-34",
    doi = "10.1103/PhysRevLett.132.211804",
    journal = "Phys. Rev. Lett.",
    volume = "132",
    number = "21",
    pages = "211804",
    year = "2024"
}
Journal Phys.Rev.Lett.

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