We present the results of a search for charged-lepton-flavor violating tau- -> ℓ− KS 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.

Adachi, I., Aggarwal, L., Ahmed, H., Ahn, Y., Aihara, H., Akopov, N., et al. (2025). Search for lepton-flavor-violating tau- -> ℓ− KS decays at Belle and Belle II. JOURNAL OF HIGH ENERGY PHYSICS, 2025(8), 1-26 [10.1007/JHEP08(2025)092].

Search for lepton-flavor-violating tau- -> ℓ− KS decays at Belle and Belle II

Di Canto A.;
2025

Abstract

We present the results of a search for charged-lepton-flavor violating tau- -> ℓ− KS 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
Adachi, I., Aggarwal, L., Ahmed, H., Ahn, Y., Aihara, H., Akopov, N., et al. (2025). Search for lepton-flavor-violating tau- -> ℓ− KS decays at Belle and Belle II. JOURNAL OF HIGH ENERGY PHYSICS, 2025(8), 1-26 [10.1007/JHEP08(2025)092].
Adachi, I.; Aggarwal, L.; Ahmed, H.; Ahn, Y.; Aihara, H.; Akopov, N.; Alghamdi, S.; Alhakami, M.; Aloisio, A.; Althubiti, N.; Amos, K.; Angelsmark, M....espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/1084160
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