From SNO to SNO+

Dr. Christine Kraus
Department of Physics, Engineering Physics, and Astronomy
Queens University, Kingston, Canada

The Sudbury Neutrino Observatory (SNO) is a 1000 tonne heavy water Cherenkov detector, that has just recently (November 2006) finished taking data with an array of 36 3He and 4 4He (third phase) detectors.  Neutron capture in these counters (Neutral-Current Detection Array, NCDs) detects neutrons from  -deuteron neutral-current interactions of solar neutrinos.  Cherenkov light signals from  e deuteron charged-current interactions and  e elastic scattering are detected by the heavy water Cherenkov detector.  The results for solar neutrino flux of 8B neutrinos and their spectrum derived from the second phase of SNO will be presented.  Also, the calibration methods for this most recent third phase of the SNO experiments are described.

The calibration of the optical properties of the SNO experiment is essential for the Cherenkov signals and the calibration with neutron sources is crucial for understanding of the NCD side of the data.  The addition of the NCDs complicates the vertex and energy reconstruction of Cherenkov events, which resulted in an extended and intensive calibration program for the third phase.

SNO+ investigates the possibility to fill the acrylic vessel (that has been used for SNO) with liquid scintillator after the physics program and decommissioning with heavy water is completed.  Located in the deepest underground site for neutrino physics (SNOLAB), SNO+ has unique capabilities, including detection of pep and CNO solar neutrinos.  SNO+ could also detect geo-neutrinos originating from radioactivity in the earth.  Furthermore, a second phase is under study, where in addition a double beta decay isotope (150Nd, may be enriched) is deployed in the liquid scintillator, resulting in a competitive next-generation search.  SNOLAB and the proposed physics program for SNO+ will be discussed.