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

The mass of the τ-lepton has been measured in the decay mode τ→3πντ using a pseudomass technique. The preliminary result is 1776.71±0.25(stat)±0.62(syst) MeV. The preliminary value of an upper limit on the relative mass difference between positive and negative τ leptons is |(Mτ+−Mτ−)|/Maverage is 5.0×10−4 at 90% CL.