SNO + expanded R&D

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The Sudbury Neutrino Observatory (SNO) uses heavy water as the medium for detecting solar neutrinos.  After current measurements with this heavy water are completed in 2007, it would be possible to replace the heavy water in SNO with a liquid scintillator - an organic hydrocarbon liquid that emits light when subatomic particles interact in it.  A liquid scintillator would boost the light produced by neutrino interactions in SNO by more than a factor of fifty over the present configuration, allowing lower energy neutrinos to be studied.  SNO with liquid scintillator (called SNO+) would be a multipurpose neutrino detector with unique physics capabilities.  These include the ability to make precision measurements of the low energy "pep" solar neutrinos that probe the details of the neutrino-matter interaction.  Testing the neutrino-matter potential is sensitive to new physics and improves the precision of our knowledge of the new neutrino properties recently discovered by SNO.  A deeper understanding of the nuclear energy generation mechanisms in stars would also be achieved.  At lower energies it would also be possible to detect geo-neutrinos, the neutrinos emitted by natural radioactivity in the Earth.  By studying geo-neutrinos one can survey the whole Earth at once to directly determine the total amount of radioactivity deep in the Earth and its role in Earth's heat generation, an important and fundamental aspect of geophysics that is currently not well determined.  A liquid scintillator detector would also serve as an excellent monitor for detecting and studying supernova neutrinos.  This is a proposal to expand the R&D for the SNO+ project in order to develop a full proposal by September 2006.  The submission of a full proposal next year aims at a funding profile that would start in April 2007, allowing for a seamless transition to the SNO+ detector after the heavy water is removed.