Measuring neutrino interactions with nucleons at the Fermilab Tevatron, the NuTeV collaboration has reported a tantalizing three-standard-deviation discrepancy with the Standard Model of particle theory. The group directed intense beams of high-energy muon neutrinos and antineutrinos at the 700-ton NuTeV target-detector and measured the ratios of neutral-current to charged-current interactions. The result translates into a value of 0.2277 ± 0.0016 for sin2 θ W, the key mixing parameter of electroweak unification. By contrast, the world average of sin2 θ W from measurements of the masses and decays of the heavy Z0 and W± bosons that mediate the weak interactions is 0.2227 ± 0.0004. The discrepancy, hinted at in earlier CERN data on Z0 decay to neutrinos, may be telling us of new particles or interactions that might guide particle theory beyond the confines of the Standard Model. (G. P. Zeller et al. ,...
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1 January 2002
January 01 2002