Sudbury Neutrino Observatory - Queen's

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The Sudbury Neutrino Observatory (SNO) is a large international project to study neutrinos from the sun and supernova. The observatory has already made a major contribution to the understanding of neutrinos by demonstrating that neutrinos have mass and that they oscillate between different neutrino types. The most common neutrino is called an electron neutrino, and has properties that are very similar to those of an electron- except that the neutrino has no charge and a much smaller mass. Electrons and electron neutrinos are part of a group of particles called leptons; the other leptons are muons and taus, and muon and tau neutrinos. When neutrinos travel through matter they interact only very rarely- only a tiny fraction stop in passing through the entire sun or earth. Electron neutrinos are produced in copious quantities in the sun- about 2% of the energy produced in the sun is emitted in the form of electron neutrinos. Because it uses heavy water as a detection medium, SNO is able to separately measure the flux of electron neutrinos and the total flux of all neutrinos. The detector is based on 1000 tonnes of heavy water, which is located 2 km underground in the Creighton mine near Sudbury. The underground location is necessary to filter out other high energy cosmic radiation. A large part of the research effort has been to minimize the amount of naturally occurring radioactivity in the heavy water and the other materials that make up and surround the detector, so that we can clearly see the relatively rare neutrino events (about 10/day). Queen's is participating in several ways. The administration of the project is Queen's. We are responsible for the calibration of the detector, for the photomultiplier tubes, and for parts of the high purity water system, electronics, data acquisition software, and for analysis of the data. We have taken a major role in understanding the detector performance, calibration and data analysis.