Limits on Strength of Neutral Currents frome+e−→μ+μ−

Abstract

The reaction $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ has been measured in the center-of-mass energy range 5.8-7.4 GeV. The polar-angle asymmetry agrees with second-order quantum electrodynamics. From this a 95% confidence limit of $M_Z>\frac{53g_a}{e}$ GeV is placed on the mass to coupling constant ratio for a neutral vector boson.