Measurement of the Elastic Scattering of Neutrinos and Antineutrinos by Protons

Abstract

We have observed 217 (66) events of the process $\ensuremath{\nu}p\ensuremath{\rightarrow}\ensuremath{\nu}p$ ($\overline{\ensuremath{\nu}}p\ensuremath{\rightarrow}\overline{\ensuremath{\nu}}p$) with an estimated background of 82 (28). The neutral-to-charged-current ratios are $\frac{\ensuremath{\sigma}(\ensuremath{\nu}p\ensuremath{\rightarrow}\ensuremath{\nu}p)}{\ensuremath{\sigma}(\ensuremath{\nu}n\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ensuremath{-}}p)}=0.11\ifmmode\pm\else\textpm\fi{}0.02$ and $\frac{\ensuremath{\sigma}(\overline{\ensuremath{\nu}}p\ensuremath{\rightarrow}\overline{\ensuremath{\nu}}p)}{\ensuremath{\sigma}(\overline{\ensuremath{\nu}}p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}n)}=0.19\ifmmode\pm\else\textpm\fi{}0.05$ for $0.40<{Q}^{2}<0.90$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, where -${Q}^{2}$ is the square of the momentum transfer to the nucleon. These yield $\frac{\ensuremath{\sigma}(\overline{\ensuremath{\nu}}p\ensuremath{\rightarrow}\overline{\ensuremath{\nu}}p)}{\ensuremath{\sigma}(\ensuremath{\nu}p\ensuremath{\rightarrow}\ensuremath{\nu}p)}=0.53\ifmmode\pm\else\textpm\fi{}0.17$. The neutral-current form factors at ${Q}^{2}=0$ are ${G}_{E}={0.5}_{\ensuremath{-}0.5}^{+0.25}$, ${G}_{M}={1.0}_{\ensuremath{-}0.04}^{+0.35}$, and ${g}_{A}={0.5}_{\ensuremath{-}0.15}^{+0.2}$.