Search for lepton flavor violating decay $B^0 \rightarrow K^{*0} \tau \ell$ using the Belle and Belle II data sample

Sumitted to PubDB: 2025-03-03

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

Authors	Valerio Bertacchi, Clotilde Lemettais, Giampiero Mancinelli, Justine Serrano
Date	2025-08-22
Working group	Radiative and Electroweak Penguin
Belle II Number	BELLE2-PUB-PH-2025-012
Abstract	We present the results of a search for the charged-lepton-flavor violating decays $B^{0} \to K^{0} \tau^{\pm}\ell^{\mp}$, where $\ell^{\mp}$ is either an electron or a muon. The results are based on 365 fb$^{−1}$ and 711 fb$^{−1}$ datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic $B$-tagging technique, and search for the signal decay in the system recoiling against the fully reconstructed $B$ meson. We find no evidence for $B^{0} \to K^{0} \tau^{\pm}\ell^{\mp}$ decays and set upper limits on the branching fractions in the range of (2.9–6.4)$\times 10^{-5}$ at 90% confidence level.
ArXiv	https://arxiv.org/abs/2505.08418
Journal	JHEP
Authorship confirmation page	https://authors.belle2.org/#82
Analysis	Search for lepton flavor violating decay $B^{0} \to K^{*0} \tau \ell$ using the Belle and Belle II data sample