Steve Biller

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.

Abstract:

A search has been made for sinusoidal periodic variations in the B8 solar neutrino flux using data collected by the Sudbury Neutrino Observatory over a 4-year time interval. The variation at a period of 1 yr is consistent with modulation of the B8 neutrino flux by the Earth's orbital eccentricity. No significant sinusoidal periodicities are found with periods between 1 d and 10 years with either an unbinned maximum likelihood analysis or a Lomb-Scargle periodogram analysis. The data are inconsistent with the hypothesis that the results of the recent analysis by Sturrock et al., based on elastic scattering events in Super-Kamiokande, can be attributed to a 7% sinusoidal modulation of the total B8 neutrino flux. © 2005 The American Physical Society.

Abstract:

Results are reported from the complete salt phase of the Sudbury Neutrino Observatory experiment in which NaCl was dissolved in the H22O ("D2O") target. The addition of salt enhanced the signal from neutron capture as compared to the pure D2O detector. By making a statistical separation of charged-current events from other types based on event-isotropy criteria, the effective electron recoil energy spectrum has been extracted. In units of 106cm-2s-1, the total flux of active-flavor neutrinos from B8 decay in the Sun is found to be 4.94-0.21+0.21(stat)-0.34+0.38(syst) and the integral flux of electron neutrinos for an undistorted B8 spectrum is 1.68-0.06+0.06(stat)-0. 09+0.08(syst); the signal from (νx,e) elastic scattering is equivalent to an electron-neutrino flux of 2.35-0.22+0.22(stat)-0.15+0.15(syst). These results are consistent with those expected for neutrino oscillations with the so-called large mixing angle parameters and also with an undistorted spectrum. A search for matter-enhancement effects in the Earth through a possible day-night asymmetry in the charged-current integral rate is consistent with no asymmetry. Including results from other experiments, the best-fit values for two-neutrino mixing parameters are Δm2=(8.0-0.4+0.6)×10-5 eV2 and θ=33.9-2.2+2.4 degrees. © 2005 The American Physical Society.