Steve Biller

Abstract:

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54_-0.31;+0.33(stat)-0.34+0.36(syst)x10(6) cm(-2) s(-1), in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Deltam2=7.59_-0.21;+0.19x10(-5) eV2 and theta=34.4_-1.2;+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.

Abstract:

This article provides the complete description of results from the Phase I data set of the Sudbury Neutrino Observatory (SNO). The Phase I data set is based on a 0.65 kiloton-year exposure of 2H2O (in the following denoted as D2O) to the solar B8 neutrino flux. Included here are details of the SNO physics and detector model, evaluations of systematic uncertainties, and estimates of backgrounds. Also discussed are SNO's approach to statistical extraction of the signals from the three neutrino reactions (charged current, neutral current, and elastic scattering) and the results of a search for a day-night asymmetry in the νe flux. Under the assumption that the B8 spectrum is undistorted, the measurements from this phase yield a solar νe flux of (νe)=1.76-0.05+0. 05(stat.)-0.09+0.09(syst.)×106 cm-2 s-1 and a non-νe component of (νμτ)=3.41-0.45+0.45(stat.)-0.45+0.48(syst.)×106 cm-2 s-1. The sum of these components provides a total flux in excellent agreement with the predictions of standard solar models. The day-night asymmetry in the νe flux is found to be Ae=7.0±4.9(stat.)-1.2+1.3%(syst.), when the asymmetry in the total flux is constrained to be zero. © 2007 The American Physical Society.

Abstract:

A search has been made for neutrinos from the hep reaction in the Sun and from the diffuse supernova neutrino background (DSNB) using data collected during the first operational phase of the Sudbury Neutrino Observatory, with an exposure of 0.65 ktons yr. For the hep neutrino search, two events are observed in the effective electron energy range of 14.3 MeV < Teff < 20 MeV, where 3.1 background events are expected. After accounting for neutrino oscillations, an upper limit of 2.3 × 104 cm-2 s-1 at the 90% confidence level is inferred on the integral total flux of hep neutrinos. For DSNB neutrinos, no events are observed in the effective electron energy range of 21 MeV < Teff < 35 MeV, and, consequently, an upper limit on the νe component of the DSNB flux in the neutrino energy range of 22.9 MeV < Eν < 36.9 MeVof 70 cm-2 s-1 is inferred at the 90% confidence level. This is an improvement by a factor of 6.5 on the previous best upper limit on the hep neutrino flux and by 2 orders of magnitude on the previous upper limit on the νe component of the DSNB flux. © 2006. The American Astronomical Society. All rights reserved.