First Results and Prospects for $\tau$ Lepton Physics at Belle~II

TL;DR

Belle II is exploring tau lepton properties and violations with a large dataset, providing initial measurements and future prospects for tau physics in a low-background electron-positron collision environment.

Contribution

This paper presents the first tau mass measurement at Belle II and discusses future prospects for tau lifetime and physics studies using the collected data.

Findings

Initial tau mass measurement reported.

Prospects for tau lifetime measurement outlined.

Tau physics program at Belle II reviewed.

Abstract

Belle II has a broad $\tau$ physics program, in particular in searches for lepton flavour and lepton number violations. Belle II profits from the relatively large $\tau$-pair production rate in the low background environment of $e^+e^-$ -collisions at 10.58 GeV. Up to mid-2021 Belle II collected a sample corresponding to $214~\text{fb}^{-1}$ of data. We present a first measurement of the $\tau$ mass, the prospects for the $\tau$-lifetime measurement, and review the overall $\tau$ lepton physics program of Belle II.