New precise determination of the τlepton mass at KEDR detector

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 $m_{\tau }=1776.80_{-0.23}^{+0.25}\pm 0.15$ MeV. Using 0.8 pb${}^{-1}$ of data collected at the ${\psi }^{\prime }$ peak the preliminary result is also obtained: ${\Gamma }_{ee}{B}_{\tau \tau }({\psi }^{\prime })=7.2\pm 2.1$ eV.

6 pages, 8 figures; The 9th International Workshop on Tau-Lepton Physics, Tau06