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A<sc>bstract</sc> We report a search for the lepton-flavor-violating decaysτ±→ℓ±α(ℓ=e,μ), whereαis an undetected spin-0 particle, such as an axion-like particle using 736 × 106tau lepton pairs collected by the Belle detector at the KEKB asymmetric-energye+e−collider. We find no evidence of signal and obtain the most stringent upper limits on the branching fractions at 95% confidence level:$$\mathcal{B}$$(τ±→ e±α) < (0.4–6.4)×10−4and$$\mathcal{B}$$(τ±→ μ±α) < (0.2–3.5)×10−4at 95% confidence level for anαmass in the range 0.0≤ mα≤1.6 GeV/c2.
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This content will become publicly available on December 1, 2026
Search for an axion-like particle in B → K(*)a(→ γγ) decays at Belle
A<sc>bstract</sc> We report a search for an axion-like particleainB→K(*)adecays using data collected with the Belle detector at the KEKB asymmetric-energy electron-positron collider. The search is based on a 711 fb−1data sample collected at the Υ(4S) resonance energy, corresponding to a sample of 772 × 106Υ(4S) events. In this study, we search for the decay of the axion-like particle into a pair of photons,a→γγ. We scan the two-photon invariant mass in the range 0.16 GeV–4.50 GeV for theKmodes and 0.16 GeV–4.20 GeV for theK*modes. No significant signal is observed in any of the modes, and 90% confidence level upper limits are established on the coupling to theWboson,gaW, as a function ofamass. The limits range from 3×10−6GeV−1to 3×10−5GeV−1, improving the current constraints ongaWby a factor of two over the most stringent previous experimental results.
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- Award ID(s):
- 2209481
- PAR ID:
- 10698779
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2025
- Issue:
- 12
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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