The differential cross sections for lepton pair production in $e^{+}{e}^{-}$ annihilation at 29 GeV have been measured and found to be in good agreement with the standard model of the electroweak interaction. With the assumption of $e-\mu -\tau$ universality, the weak neutral-current couplings are determined to be ${g_a}^2=0.23\mathrm{}\pm 0.05$ and ${g_v}^2=0.03\mathrm{}\pm 0.04$.

• Received 29 August 1983

DOI:https://doi.org/10.1103/PhysRevLett.51.1941