Neutral-current effects in e + e − → τ + τ − on a ψ -like resonance

We suggest that the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ on a $\ensuremath{\psi}$-like resonance may provide a method for testing theories of the weak neutral current. The method is based on the observation that the $\ensuremath{\tau}$ decay products from this reaction will have a forward-backward asymmetry induced by the polarization sensitivity of the $\ensuremath{\tau}$ decays. We point out that, to the extent that the $\ensuremath{\psi}$-like resonance stands above background, this reaction provides not only an improved counting rate but also relief from the radiative asymmetries that trouble proposals to measure neutral-current asymmetries in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$.