SNO
Past IPP Scientist: Richard Hemingway
Laboratory: SNOLAB
The Sudbury Neutrino Observatory (SNO) was a neutrino oscillation appearance experiment that demonstrated the conversion of electron flavored solar neutrinos to other active flavors. This observation explains the long-standing solar neutrino problem in which too few electron neutrinos were observed in experiments primarily or solely sensitive to those neutrinos. The SNO results also precisely confirm the understanding of the solar model for neutrino production. A global analysis of these and other solar and reactor neutrino results yields the neutrino mass difference Delta m^2 = 8.0 (+0.6-0.4) X10^-3 eV^2 and mixing angle theta = 33.9 (+2.4-2.2) degrees. Via the neutrino mass-difference constraints, a fairly stringent laboratory limit is placed on the contribution of neutrino mass to the density of the universe.
First physics data were taken in November of 1999. Phase I of SNO consisted of 306 live days of neutrino data with pure heavy water (D20). Phase II consisted of 391 live days of D20 + 0.2% NaCl. The next phase consists of running with 40 strings of He3/He4 neutron detectors (NCD). Data taking of this phase began in December 2004 and ran through November 2006. With these data, an improved measurement of the total active neutrino flux to a precision comparable to or better than the present has been achieved. Day-night variations in the charged-current flux are a feature of matter-enhancement, and the NCDs will improve the ability to measure them by separating the neutron component from the Cherenkov spectrum.
The SNO collaboration consisted of approximately 130 physicists from 14 insitutions based in 3 countries. The Canadian group comes from UBC, TRIUMF, Carleton, Guelph, Laurentian, Queen's.