Strength of the antineutrino-proton neutral-current interaction

Using the Fermilab 15-foot hydrogen bubble chamber exposed to a broad-band $\overline{\ensuremath{\nu}}$ and $\ensuremath{\nu}$ beam, we have studied the neutral-to-charged-current cross-section ratio $R$ for interactions on protons. The ratio ${R}^{\overline{\ensuremath{\nu}}p}$ is found assuming various forms of the neutral-current couplings. The data are consistent with the predictions of the Weinberg-Salam model and, assuming this model, we obtain ${R}^{\overline{\ensuremath{\nu}}p}=0.42\ifmmode\pm\else\textpm\fi{}0.13$.