Speaker
Description
Rates of lepton-flavor violation in charged lepton decays are enhanced in many beyond-the-standard-model theories. The low-background samples of $e^+e^- \to \tau^+\tau^-$ events collected by Belle and Belle II allow world-leading searches for such decays with tau leptons. We present Belle II results for the decays $\tau \to \ell V^0$, where $V^0$ is a neutral vector meson, $\tau \to 3\mu$, $\tau \to \Lambda \pi$ and $\tau \to \bar\Lambda \pi$ (which violates both baryon and lepton number conservation) using data samples up to 424 fb$^{−1}$. We also present Belle searches for the charged lepton-flavor-violating (CLFV) decays $B_s \to \ell \tau$ and $\Upsilon(2S) \to \ell \tau$. We present searches for the for the baryon and lepton number violating decays $D \to p \ell$ by analyzing 921 fb$^{−1}$ of data collected by Belle at and 60 MeV below the $\Upsilon(4S)$ resonance, and at the $\Upsilon(5S)$ resonance. Finally, we present a search for $B^0 \to K^0_S \tau \ell$ using a combined Belle and Belle II data set.
| Working Group | WG 4: Muon Physics |
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