Measurement of the mass of the $τ$-lepton and an upper limit on the mass difference between $τ^+$ and $τ^-$

Abstract

The mass of the $τ$-lepton has been measured in the decay modes $τ\to 3πν_τ$ and $τ\to 3ππ^0ν_τ$ using a pseudomass technique. The preliminary result is $1776.71\pm 0.25 {(stat)} \pm 0.62 {(syst)}$ MeV. The preliminary value of an upper limit on the relative mass difference between positive and negative $τ$ leptons is $|(M_{τ^+}-M_{τ^-})|/M_{\mathrm{average}}$ is $5.0 \times 10^{-4}$ at 90% CL.