Weakly Coupled Neutral Currents

A general analysis of interactions of the current-current form involving neutral vector and axial-vector hadron and lepton currents is given and compared with present experimental information. While the restrictions placed upon such neutral current interactions by existing data are found to be rather severe, a number of theoretically attractive possibilities remain. Still consistent with experiment are models obeying the $\Delta I<\mathrm{}\frac{3}{2}$, $\Delta Y<\mathrm{}2\mathrm{}$ rule, a universal model based on the $\mathrm{SU}\left(2\right)\mathrm{}$ algebra of charges, a model with a strangeness-conserving isovector neutral hadron current and symmetrically coupled lepton currents, and models in which the neutral currents couple only in a superweak fashion. In contrast, a model which incorporates the octet rule as a built-in symmetry appears to be ruled out on the basis of present information.