Precision Measurement of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mrow><mml:mo>sin</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>θ</mml:mi></mml:mrow><mml:mrow><mml:mi>W</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>from Semileptonic Neutrino Scattering

The ratio ${R}_{\ensuremath{\nu}}$ of the neutral- to charged-current cross sections of neutrinos in iron has been measured in an exposure of the CERN-Dortmund-Heidelberg-Saclay neutrino detector to a 160-GeV/c neutrino narrow-band beam at the CERN Super Proton Synchrotron. The result is ${R}_{\ensuremath{\nu}}=0.3072\ifmmode\pm\else\textpm\fi{}0.0025(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.0020(\mathrm{syst})$, for hadronic energy greater than 10 GeV. The electroweak mixing parameter is ${sin}^{2}{\ensuremath{\theta}}_{W}=0.225\ifmmode\pm\else\textpm\fi{}0.005(\mathrm{expt})\ifmmode\pm\else\textpm\fi{}0.003(\mathrm{theor})+0.013({m}_{c}\ensuremath{-}1.5 \frac{\mathrm{GeV}}{{c}^{2}})$, where ${m}_{c}$ is the charm-quark mass.