Abstract
The extension of the standard model predicts the existence of a lepton-flavor-universality-violating boson that couples only to the heavier lepton families. We search for such a through its invisible decay in the process . We use a sample of electron-positron collisions at a center-of-mass energy of 10.58 GeV collected by the Belle II experiment in 2019–2020, corresponding to an integrated luminosity of . We find no excess over the expected standard-model background. We set 90%-confidence-level upper limits on the cross section for this process as well as on the coupling of the model, which ranges from at low masses to 1 at masses of .
- Received 7 December 2022
- Accepted 19 April 2023
DOI:https://doi.org/10.1103/PhysRevLett.130.231801
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society