Electroweak Effects ine+e−→τ+τ−at 29 GeV

Abstract

A high-statistics measurement is presented of the cross section for the process $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ at $\sqrt{s}=29\mathrm{}$ GeV from the MAC detector at PEP. A fit to the angular distribution of our sample of 10 153 events with $\left|cos\theta \right|<\mathrm{}0.9\mathrm{}$ gives an asymmetry $A_{\tau \tau }=-0.055\mathrm{}\pm 0.012\pm 0.005$ from which we find the product of electron and tau axial-vector weak neutral couplings $g_A^e{g}_A^{\tau }=0.22\mathrm{}\pm 0.05$.