A Precise Determination of the Electroweak Mixing Angle from Semileptonic Neutrino Scattering

The cross-section ratio of neutral-current and charged-current semileptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result:R v =0.3093±0.0031 for hadronic energy larger than 4 GeV. From this ratio we determined the electroweak mixing angle sin2θ W , wherem c is the charm-quark mass in GeV/c2. Comparison with direct measurements ofm w andm z determines the radiative shift of the intermediate boson mass Δr=0.077±0.025(exp.)±0.038(syst.), in agreement with the prediction. Assuming the validity of the electroweak standard theory we determined ϱ=0.990−0.013(m c −1.5)±0.009(exp.)±0.003(theor.).