Quark and lepton couplings in the weak interactions

We present a comprehensive study of the weak neutral-current interactions of $u$ and $d$ quarks and of the electron. A model-independent analysis using data from deep-inelastic, inclusive-pion, elastic, and exclusive-pion neutrino processes provides a unique determination of the $u$- and $d$-quark couplings. For electron couplings, neutrino-electron-scattering, atomic-parity-violation, and new polarized-electron-scattering data are discussed. With the assumption of a single $Z^0$ boson, we show that the electron couplings are almost uniquely determined. The predictions of the Weinberg-Salam model (for ${{sin}^2\theta }_W=0.20-0.30\mathrm{}$) are in remarkably good agreement with our results.