Improved measurement of $\psi (2S)$ decays into $\tau ^{+}\tau ^{-}$

TL;DR

This paper reports a precise measurement of the branching fraction of the $ ext{psi}(2S)$ particle decaying into tau lepton pairs, using a large dataset from BESII, improving the understanding of charmonium decay modes.

Contribution

The study provides the first high-precision measurement of $ ext{psi}(2S) o au^+ au^-$ decay branching fraction with systematic and statistical uncertainties.

Findings

Branching fraction measured as (3.10 ± 0.21 ± 0.38)×10^{-3}

Results are consistent with theoretical predictions

Enhances understanding of charmonium decay channels

Abstract

Using 14M $\psi (2S)$ events collected at BESII, the branching fraction of $\psi (2S)\to \tau ^{+}\tau ^{-}$ is measured to be $Br_{\tau \tau}=(3.10\pm 0.21\pm 0.38)\times 10^{-3}$, where the first error is statistical and the second is systematic.