Precision measurement of the mass of the \tau$ lepton
An energy scan near the tau pair production threshold has been performed using the BESIII detector. About 24 pb( 1) of data, distributed over four scan points, were collected. This analysis is based on t pair decays to ee, e mu, eh, h, hh, e. and p. final states, where h denotes a charged p or K. The mass of the t lepton is measured from a maximum likelihood fit to the t pair production cross section data to be m(tau) 1776.91 0.12_0.10 0.13 _ MeV/c(2) which is currently the most precise value in a single measurement.