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Search for lepton-flavor-violating tau-lepton decays to ℓγ at Belle

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Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays τ±±γ ( = e, μ) are predicted to have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via τ±±γ using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb1, is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, \( \mathcal{B} \)(τ±μ±γ) ≤ 4.2 × 108 and \( \mathcal{B} \)(τ±e±γ) ≤ 5.6 × 108, are set at 90% confidence level.


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The BELLE collaboration., Uno, K., Hayasaka, K. et al. Search for lepton-flavor-violating tau-lepton decays to ℓγ at Belle. J. High Energ. Phys. 2021, 19 (2021).

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