Evidence for electron neutrino flavor change through measurement of the (8)B solar neutrino flux at the Sudbury Neutrino Observatory

Mark Stephen Neubauer, University of Pennsylvania


The Sudbury Neutrino Observatory (SNO) is a water Cerenkov detector designed to study solar neutrinos. Using 1 kiloton of heavy water as the target and detection medium, SNO is able to separately determine the flux of electron neutrinos (νe) and the flux of all active neutrinos from the Sun by measuring the rate of charged current (CC) and neutral current (NC) interactions with deuterons. A comparison of these interaction rates allows for direct observation of solar neutrino oscillations. SNO can also search for oscillations by comparing the rate of CC and neutrino-electron elastic scattering (ES) events, since ES has both charged current and neutral current sensitivity. In this thesis, we present measurement of the 8B solar ν e flux of [special characters omitted] (stat+syst) × 106cm−2s −1 (35% BP2000 SSM) through measurement of the CC rate over 169.3 days of livetime. We have also measured the 8B flux from the ES reaction to be [special characters omitted] (stat+syst), consistent with measurements by previous water Cerenkov experiments. A flavor analysis comparing the CC measured flux with that determined through ES by SuperKamiokande yields a non-νe active neutrino flux from 8B of [special characters omitted] × 106cm−2s−1 , providing evidence for νe → ν μ,τ oscillations as a solution to the solar neutrino problem. This result excludes pure solar νe → ν s oscillations at greater than the 99.7% C.I. The total active 8B neutrino flux has been measured to be [special characters omitted] × 106cm−2s−1 , consistent with BP2000 SSM predictions. First analyses of the CC (NHit) spectrum and hep flux in SNO are presented. The CC spectrum is found to be a good fit to expectations from an undistorted 8B spectrum, and global best fit vacuum oscillation solutions are disfavored over the other solutions by the data. Through observations near the 8B endpoint with consideration of energy systematics, hep flux limits of 4.1 (90% C.I.) and 6.9 (99% C.I.) times SSM expectations are obtained. A statistical fit for the hep flux signal yields a 3σ upper limit of 3.2 times the SSM expected flux.

Subject Area

Particle physics|Astronomy|Astrophysics

Recommended Citation

Neubauer, Mark Stephen, "Evidence for electron neutrino flavor change through measurement of the (8)B solar neutrino flux at the Sudbury Neutrino Observatory" (2001). Dissertations available from ProQuest. AAI3015349.