Observations of neutral-current ν interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current, elastic scattering, and charged current reactions and assuming the standard 8 B shape, the

The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates. For charged current events, assuming an undistorted 8B spectrum, the night minus day rate is 14.0%+/-6.3%(+1.5%)(-1.4%) of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the nu(e) asymmetry is found to be 7.0%+/-4.9%(+1.3%)(-1.2%). A global solar neutrino analysis in terms of matter-enhanced oscillations of two active flavors strongly favors the large mixing angle solution.

Solar neutrinos from (8)B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of nu(e)'s is measured by the CC reaction rate to be straight phi(CC)(nu(e)) = 1.75 +/- 0.07(stat)(+0.12)(-0.11)(syst) +/- 0.05(theor) x 10(6) cm(-2) s(-1). Comparison of straight phi(CC)(nu(e)) to the Super-Kamiokande Collaboration's precision value of the flux inferred from the ES reaction yields a 3.3 sigma difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non- nu(e) component in the solar flux. The total flux of active 8B neutrinos is determined to be 5.44+/-0.99 x 10(6) cm(-2) s(-1).

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2A search for neutron-antineutron (n −n) oscillation was undertaken in Super-Kamiokande using the 1,489 day livetime or 2.45 × 10 34 neutron-year exposure data. This process violates both baryon and (baryon−lepton) numbers by two units and is predicted by a large class of hypothetical models where the seesaw mechanism is incorporated to explain the observed tiny neutrino masses and the matter-antimatter asymmetry in the universe. No evidence for n −n oscillation was found, the lower limit of the lifetime for neutrons bound in 16 O, in an analysis that included all of the significant sources of experimental uncertainties, was determined to be 1.9 × 10 32 years at the 90% confidence level. The corresponding lower limit for the oscillation time of free neutrons was calculated to be 2.7 × 10 8 s using a theoretical value of the nuclear suppression factor of 0.517 × 10 23 s −1 and its uncertainty.