PREPRINT

Electron Energy Spectra, Fluxes, and Day-Night Asymmetries of ${}^{8}$B Solar Neutrinos from the 391-Day Salt Phase SNO Data Set

SNO Collaboration
arXiv:nucl-ex/0502021

Submitted on 25 February 2005

Abstract

Results are reported from the complete salt phase of the Sudbury Neutrino Observatory experiment in which NaCl was dissolved in the D${}_{2}$O target. The addition of salt enhanced the signal from neutron capture, as compared to the pure D${}_{2}$O 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 ${10}^{6}$ cm${}^{-2}$ s${}^{-1}$, the total flux of active-flavor neutrinos from ${}^{8}$B decay in the Sun is found to be ${4.94}_{-0.21}^{+0.21}{\left(stat\right)}_{-0.34}^{+0.38}\left(syst\right)$ and the integral flux of electron neutrinos for an undistorted ${}^{8}$B spectrum is ${1.68}_{-0.06}^{+0.06}{\left(stat\right)}_{-0.09}^{+0.08}\left(syst\right)$; the signal from (${\nu }_{x}$,e) elastic scattering is equivalent to an electron-neutrino flux of ${2.35}_{-0.22}^{+0.22}{\left(stat\right)}_{-0.15}^{+0.15}\left(syst\right)$. 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 $\mathrm{\Delta }{m}^{2}=\left({8.0}_{-0.4}^{+0.6}\right)×{10}^{-5}$ eV${}^{2}$ and $\theta ={33.9}_{-2.2}^{+2.4}$ degrees.

Preprint

Comment: 45 pages, 36 figures in 49 eps files

Subjects: Nuclear Experiment; Astrophysics; High Energy Physics - Experiment