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 $${\tau }^{-}\to {{\ell}}^{-}{K}_{s}^{0}$$ decays at Belle and Belle II
Dorigo, M.;Gabrielli, A.;Ghosh, D.;Lanceri, L.;Manfredi, R.;Mantovano, M.;Raiz, S.;Vitale, L.;
2025-01-01
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.File in questo prodotto:
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