# ICHEP 2014

2-9 July 2014
Valencia, Spain

## Measurements of electroweak properties of $\tau$ lepton at the Belle experiment

5 Jul 2014, 15:30
15m
Sala 1 ()

### Sala 1

Oral presentation Top-quark and ElectroWeak Physics

### Speaker

Dr. Hisaki Hayashii (Nara　Women's University)

### Description

We present preliminary result of the measurement of Michel parameters in leptonic $\tau$ decays and search for the Electric Dipole Moment of the $\tau$ lepton using the world-largest $\tau$ data sample collected by the Belle detector at the KEKB collider. Michel parameters are extracted from $(\tau^{\mp}\to\ell^{\mp}\nu\nu$, $\tau^{\pm}\to\pi^{\pm}\pi^0\nu)$ and $(\tau^{\mp}\to\pi^{\mp}\pi^0\nu$, $\tau^{\pm}\to\pi^{\pm}\pi^0\nu)$ events in Belle's full $\tau$ data sample, where $\tau^{\pm}\to\pi^{\pm}\pi^0\nu$ is used as a spin analyzer since $\tau$ spin information is necessary to evaluate Michel parameters. The Electric Dipole Moment of the $\tau$ lepton is one of the fundamental parameters and useful to discuss the new physics as a signal of it through CP violating loop effect. We have analyzed $\tau^+\tau^-\gamma"$ vertex effect from the $e^+ e^- \to \tau^+ \tau^-$ reaction in Belle's full $\tau$ data sample which is about 30 times larger than that used at the previous measurement.

### Primary author

Prof. Youngjoon Kwon (Yonsei University)

 Slides

### Paper

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