Final Technical Report

Over the past year, our group here at the University of Texas has continued to focus primarily on analysis of data from the Sudbury Neutrino Observatory (SNO), in particular on a push to lower the energy threshold used in solar neutrino analyses and on a search for short time-scale astrophysical phenomena in the neutrino data set. We have in addition begun R and D and simulation work on a new direct search for dark matter as part of the DEAP/CLEAN collaboration, as well as an effort associated with work on a new experiment using the existing SNO detector (SNO+). Lastly, we have also been doing some very early studies of an experiment to measure the neutrino mass using the beta decay of cold tritium atoms. Our work on SNO has focused primarily on making a low-threshold spectral measurement of the flux of {sup 8}B solar neutrinos. The work forms the bulk of graduate student Stan Seibert's PhD thesis. Nearly all systematic uncertainties associated with the analysis have now been measured, in particular the dominant uncertainties such as energy scale and resolution, and the uncertainty on SNO's 'isotropy' parameter used to distinguish electrons, neutrons, and radioactive backgrounds. It is now clear that we will be able to fit the {sup 8}B energy spectrum to a threshold of 4 MeV or below, with uncertainties in the 4 MeV bin somewhere between 15-20%. This will be the lowest threshold measurement ever made using the water Cherenkov technique, and will provide a test of the MSW-predicted distortion of the {sup 8}B energy spectrum. As an additional benefit of the low threshold analysis, we expect to get total uncertainties on the NC flux in the neighborhood of 4%, nearly a factor of 2 better than any of SNO's previous measurements of the total {sup 8}B flux