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Latest Belle results on Tau decays

by Y. Jin; D. Epifanov; H. Aihara

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Submission summary

Authors (as registered SciPost users): Yifan Jin
Submission information
Preprint Link: scipost_201810_00006v1  (pdf)
Date submitted: 2018-10-31 01:00
Submitted by: Jin, Yifan
Submitted to: SciPost Physics Proceedings
Proceedings issue: The 15th International Workshop on Tau Lepton Physics (TAU2018)
Ontological classification
Academic field: Physics
  • High-Energy Physics - Experiment
Approach: Experimental


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 $\mathcal{B}(\tau^-\rightarrow \pi^- e^+ e^- \nu_\tau) = (2.11 \pm 0.19 \pm 0.30) \times 10^{-5}$, where the first uncertainty is statistical and the second is systematic. An upper limit is set on the branching fraction of $\tau^- \rightarrow \pi^- \mu^+ \mu^- \nu_\tau$, $\mathcal{B}(\tau^-\rightarrow \pi^- \mu^+ \mu^- \nu_\tau) < 1.06 \times 10^{-5}$, at 90\% CL.

Current status:
Has been resubmitted

Reports on this Submission

Anonymous Report 1 on 2018-12-2 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:scipost_201810_00006v1, delivered 2018-12-02, doi: 10.21468/SciPost.Report.687


The proceeding reports the preliminary result of the rare tau decay of $\tau^-\to\pi^-\nu_{\tau}l^+l^-$ from the Belle experiment. The $\pi^-\nu_{\tau}e^+e^-$ mode has been observed for the first time, the branching fraction is consistent with the Standard Model calculation, while the upper limit has been measured for the $\mu^+\mu^-$ mode. The measurements provide important information for the understanding of $\pi W\gamma^*$ vertex, as well as constrain to physics beyond Standard Model.

This proceeding is an important contribution to the field of tau physics and I recommend it for publication.

Requested changes

It would also be interest to show the central value of the branching fraction of
$\tau^{-}\to\pi^-\nu_{\tau}\mu^{+}\mu^{-}$, besides the upper limit.

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