Measurements of tau decay modes and a precise determination of the mass

Abstract

The cross sections for e +e − → e +( μ + + non showering track + any photons have been measured for cm energies between 3.1 GeV and 5.2 GeV. We observe τ-pair production below the thresholdfor charm production and determine the τ mass to be 1.807 ± 0.020 GeV from a fit to the energy dependence of the cross section. The ration of the leptonic branching ratios B μ / B e = 0.92 ± 0.32 is consistent with eμ-universality. The following branching ratios are determined for a V-A coupling: B(τ → ν τ e ν) = B(τ → ν τμ ν) = 0.182 + 0.028 . B( τ → ν τ + charged hadron + any photons) = 0.29 ± 0.11, B( τ → ν τ + three or more charged hadrons + any photons) = 0.35 ± 0.11.