Search for lepton-flavor-violating $τ^- \to l^- K_S^0$ decays at Belle and Belle II

Sumitted to PubDB: 2024-11-27

Category: Physics / performance paper, Visibility: Latest Version Public

Authors	Klemens Lautenbach, Justine Serrano, Laura Zani
Date	2025-10-01
Working group	Tau
Belle II Number	BELLE2-PUB-DRAFT-2024-006
Abstract	We present the results of a search for charged-lepton-flavor violating decays $\tau^{\pm} \rightarrow l^{\pm}K_{S}^{0}$, where $l^{\pm}$ is either an electron or a muon produced in association with a neutral $K_S^0$ meson. We use a data set of $e^+e^-$ collisions composed of a 424\invfb sample of data recorded by the Belle II experiment and a $980~$fb$^{-1}$ sample of data recorded by the Belle experiment. We observe XX events and set a $90\%$ confidence level upper limit of $XX \times 10^{-8}$ and $YY \times 10^{-8}$ on the branching fraction of $\tau^{\pm} \rightarrow e^{\pm}K_{S}^{0}$ and $\tau^{\pm} \rightarrow \mu^{\pm}K_{S}^{0}$ decays, respectively.
Journal	JHEP
Authorship confirmation page	https://authors.belle2.org/#74
Analysis	LFV search for $\tau \rightarrow K_S^0 \ell$