We present the results of a search for charged-lepton-flavor violating decays, where ℓ− is either an electron or a muon. We combine e+e− data samples recorded by the Belle II experiment at the SuperKEKB collider (428 fb−1) with samples recorded by the Belle experiment at the KEKB collider (980 fb−1) to obtain a sample of 1.3 billion e+e− → τ+τ− events. We observe 0 and 1 events and set 90% confidence level upper limits of 0.8 × 10−8 and 1.2 × 10−8 on the branching fractions of the decay modes and, respectively. These are the most stringent upper limits to date.

Search for lepton-flavor-violating decays at Belle and Belle II / Adachi, I., Aggarwal, L., Ahmed, H., Ahn, Y., Aihara, H., Akopov, N., Alghamdi, S., Alhakami, M., Aloisio, A., Althubiti, N., Amos, K., Angelsmark, M., Anh Ky, N., Antonioli, C., Asner, D.M., Atmacan, H., Aushev, V., Aversano, M., Ayad, R., Babu, V., et al.. - In: JOURNAL OF HIGH ENERGY PHYSICS. - ISSN 1029-8479. - 2025:8(2025). [10.1007/JHEP08(2025)092]

Search for lepton-flavor-violating decays at Belle and Belle II

Aloisio A.;Campajola M.;De Nardo G.;Gaudino G.;Giordano R.;Merola M.;Mirra M.;Pardi S.;
2025

Abstract

We present the results of a search for charged-lepton-flavor violating decays, where ℓ− is either an electron or a muon. We combine e+e− data samples recorded by the Belle II experiment at the SuperKEKB collider (428 fb−1) with samples recorded by the Belle experiment at the KEKB collider (980 fb−1) to obtain a sample of 1.3 billion e+e− → τ+τ− events. We observe 0 and 1 events and set 90% confidence level upper limits of 0.8 × 10−8 and 1.2 × 10−8 on the branching fractions of the decay modes and, respectively. These are the most stringent upper limits to date.
2025
Search for lepton-flavor-violating decays at Belle and Belle II / Adachi, I., Aggarwal, L., Ahmed, H., Ahn, Y., Aihara, H., Akopov, N., Alghamdi, S., Alhakami, M., Aloisio, A., Althubiti, N., Amos, K., Angelsmark, M., Anh Ky, N., Antonioli, C., Asner, D.M., Atmacan, H., Aushev, V., Aversano, M., Ayad, R., Babu, V., et al.. - In: JOURNAL OF HIGH ENERGY PHYSICS. - ISSN 1029-8479. - 2025:8(2025). [10.1007/JHEP08(2025)092]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/1012035
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