Neutral-current effects in the decayψ→μ+μ−

We calculate the angular distribution and polarization of muon pairs from the decay of a $\psi$ particle produced in $e^{+}{e}^{-}$ collisions. We show, among other things, that weak neutral-current effects do not produce a forward-backward asymmetry but do give the muons a net helicity which is a sensitive test of both neutral current theories and models of the $\psi$ particles. The possibility of measuring the resulting net helicity in the near future is briefly discussed.