S. Patra, V. Bhardwaj, K. Trabelsi, et al. (Belle Collaboration)
Journal of High Energy Physics, 95 (2022)
We present a search for the charged lepton-flavor-violating decays ϒ(1S) → ℓ±ℓ′∓ and radiative charged lepton-flavour-violating decays ϒ(1S) → γℓ±ℓ′∓ [ℓ,ℓ′ = e, μ, τ] using the 158 million ϒ(2S) sample collected by the Belle detector at the KEKB collider. This search uses ϒ(1S) mesons produced in ϒ(2S) → π+π− ϒ(1S) transitions. We do not find any significant signal, so we provide upper limits on the branching fractions at the 90% confidence level.
Preprint : https://arxiv.org/abs/2201.09620