Production cross section and topological decay branching fractions of theτlepton

We report new measurements of the production cross section for the reaction $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ at $\sqrt{s}=29\mathrm{}$ GeV, as well as the topological decay branching fractions of the $\tau$ lepton. The data were taken with the High Resolution Spectrometer at the SLAC $e^{+}{e}^{-}$ colliding-beam facility PEP. The measured cross section yields $R_{\tau \tau }=1.044\mathrm{}\pm 0.014\pm 0.030$ [where the first (second) error is statistical (systematic)], consistent with QED and corresponding to QED cutoff parameters of ${\Lambda }_{+}>129\mathrm{}$ GeV and ${\Lambda }_{-}>284\mathrm{}$ GeV at the 95% C.L. The fractions of $\tau$ decays into one and three charged particles are $B_1=0.864\mathrm{}\pm 0.003\pm 0.003$ and $B_3=0.135\mathrm{}\pm 0.003\pm 0.003$.