Search for lepton-flavor-violating $\tau$ decays to a lepton and an invisible boson at Belle II

Sumitted to PubDB: 2022-06-22

Category: Physics / performance paper

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Principal Authors Eduard Cruz Burelo, Alejandro De Yta Hernandez, Marcela Garcia Hernandez, Ivan Heredia de la Cruz, Thomas Kraetzschmar, Petar Rados, Armine Rostomyan, Francesco Tenchini
Date 2023-05-02
Working group Tau
Belle II Number BELLE2-PUB-PH-2022-009
Abstract We search for lepton-flavor-violating $\tau^-\to e^-\alpha$ and $\tau^-\to\mu^-\alpha$ decays, where $\alpha$ is an invisible spin-0 boson. The search uses electron-positron collisions at $10.58$ GeV center-of-mass energy with an integrated luminosity of $62.8$ fb$^{-1}$, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known $\tau^-\to e^-\bar\nu_e \nu_\tau$ and $\tau^-\to \mu^-\bar\nu_\mu \nu_\tau$ decays. We report 95% confidence-level upper limits on the branching-fraction ratio ${\mathcal B}(\tau^-\to e^- \alpha) / {\mathcal B}(\tau^- \to e^- \bar\nu_e \nu_\tau)$ in the range $(1.1-9.7) \times 10^{-3}$ and on ${\mathcal B}(\tau^-\to \mu^- \alpha) / {\mathcal B}(\tau^- \to \mu^- \bar\nu_\mu \nu_\tau)$ in the range $(0.7-12.2) \times 10^{-3}$ for $\alpha$ masses between 0 and 1.6 GeV/c$^2$. These results provide the most stringent bounds on invisible boson production from $\tau$ decays.
ArXiv https://arxiv.org/abs/2212.03634
Inspire https://inspirehep.net/literature/2611490
DOI 10.1103/PhysRevLett.130.181803
Reference Phys.Rev.Lett. 130, 181803 (2023)
Bibtex 
@article{Belle-II:2022heu,
    author = "Adachi, I. and others",
    collaboration = "Belle-II",
    title = "{Search for Lepton-Flavor-Violating {\ensuremath{\tau}} Decays to a Lepton and an Invisible Boson at Belle II}",
    eprint = "2212.03634",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2022-007, KEK Preprint 2022-39",
    doi = "10.1103/PhysRevLett.130.181803",
    journal = "Phys. Rev. Lett.",
    volume = "130",
    number = "18",
    pages = "181803",
    year = "2023"
}
Journal Phys.Rev.Lett.

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