New precise determination of the \tau lepton mass at KEDR detector

TL;DR

This paper reports a new precise measurement of the tau lepton mass using data from the KEDR detector at VEPP-4M, achieving improved accuracy through threshold cross section analysis.

Contribution

The study presents the first precise determination of the tau lepton mass at the KEDR detector, utilizing threshold behavior of the cross section and new data analysis techniques.

Findings

Tau lepton mass measured as 1776.80^{+0.25}_{-0.23} ext{ MeV}

Preliminary measurement of \\Gamma_{ee}B_{\\tau\\tau}(\\psi') = 7.2 \\pm 2.1 ext{ eV}

Enhanced precision in tau mass measurement compared to previous results.

Abstract

The status of the experiment on the precise $\tau$ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the $\tau^+\tau^-$ cross section behaviour around the production threshold. The preliminary result based on 6.7 pb$^{-1}$ of data is $m_{\tau}=1776.80^{+0.25}_{-0.23} \pm 0.15$ MeV. Using 0.8 pb$^{-1}$ of data collected at the $\psi'$ peak the preliminary result is also obtained: $\Gamma_{ee}B_{\tau\tau}(\psi') = 7.2 \pm 2.1$ eV.