Experimental Measurement of the Mass of the τ Lepton at the Beijing Electron Positron Collider (BEPC)

Abstract：

The τ lepton mass was measured with the data taken by the Beijing spectrometer (BES) at the BEPC at the Institute of High Energy Physics in Beijing. Approximately 5000 nb^-1 integrated luminosity was accumulated. Pairs of τ lepton produced near the threshold have been studied in eμ final states. The maximum likelihood method was used for both of predicting a sequence of experimental energies to approach the threshold and data fitting. The measurement yields the τ mass of 1776.9_-0.5^+0.4 ±02 MeV.