Neutrino observations from the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) is a water imaging Cherenkov detector. Its usage of 1000 metric tons of $D2O$ as target allows the SNO detector to make a solar-model independent test of the neutrino oscillation hypothesis by simultaneously measuring the solar $νe$ flux and the total flux of all active neutrino species. Solar neutrinos from the decay of $8B$ have been detected at SNO by the charged-current (CC) interaction on the deuteron and by the elastic scattering (ES) of electrons. While the CC reaction is sensitive exclusively to $νe,$ the ES reaction also has a small sensitivity to $νμ$ and $ντ.$ In this paper, recent solar neutrino results from the SNO experiment are presented. It is demonstrated that the solar flux from $8B$ decay as measured from the ES reaction rate under the no-oscillation assumption is consistent with the high precision ES measurement by the Super-Kamiokande experiment. The $νe$ flux deduced from the CC reaction rate in SNO differs from the Super-Kamiokande ES results by 3.3σ. This is evidence for an active neutrino component, in additional to $νe,$ in the solar neutrino flux. These results also allow the first experimental determination of the total active $8B$ neutrino flux from the Sun, and is found to be in good agreement with solar model predictions.