# Latest Belle results on Tau decays

### Submission summary

 As Contributors: Yifan Jin Preprint link: scipost_201810_00006v2 Date accepted: 2019-01-15 Date submitted: 2018-12-03 01:00 Submitted by: Jin, Yifan Submitted to: SciPost Physics Proceedings Proceedings issue: The 15th International Workshop on Tau Lepton Physics (Amsterdam, 2018-09) Academic field: Physics Specialties: High-Energy Physics - Experiment Approach: Experimental

### Abstract

We present preliminary results of a latest measurement at Belle, the branching fraction of rare tau decay, $\tau^- \rightarrow \pi^- \nu_{\tau} \ell^+ \ell^-$ ($\ell = e$ or $\mu$), using a 562 $\rm fb^{-1}$\ data set. The branching fraction of $\tau^- \rightarrow \pi^- e^+ e^- \nu_\tau$ is measured to be $\mathbf{ \mathcal{B}(\tau^-\rightarrow \pi^- e^+ e^- \nu_\tau) = (2.11 \pm 0.19 \pm 0.30) \times 10^{-5}}$, where the first uncertainty is statistical and the second is systematic. An upper limit is set on the branching fraction of $\tau^- \rightarrow \pi^- \mu^+ \mu^- \nu_\tau$, $\mathbf{\mathcal{B}(\tau^-\rightarrow \pi^- \mu^+ \mu^- \nu_\tau) < 1.06 \times 10^{-5}}$, at 90\% confidence level.

Published as SciPost Phys. Proc. 1, 002 (2019)