Precision measurement of the mass of theτlepton

An energy scan near the $\ensuremath{\tau}$ pair production threshold has been performed using the BESIII detector. About $24\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of data, distributed over four scan points, were collected. This analysis is based on $\ensuremath{\tau}$ pair decays to $ee$, $e\ensuremath{\mu}$, $eh$, $\ensuremath{\mu}\ensuremath{\mu}$, $\ensuremath{\mu}h$, $hh$, $e\ensuremath{\rho}$, $\ensuremath{\mu}\ensuremath{\rho}$ and $\ensuremath{\pi}\ensuremath{\rho}$ final states, where $h$ denotes a charged $\ensuremath{\pi}$ or $K$. The mass of the $\ensuremath{\tau}$ lepton is measured from a maximum likelihood fit to the $\ensuremath{\tau}$ pair production cross-section data to be ${m}_{\ensuremath{\tau}}=(1776.91\ifmmode\pm\else\textpm\fi{}{0.12}_{\ensuremath{-}0.13}^{+0.10})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, which is currently the most precise value in a single measurement.