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

SNO Collaboration

Submitted on 25 February 2005


Results are reported from the complete salt phase of the Sudbury Neutrino Observatory experiment in which NaCl was dissolved in the 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 106 cm2 s1, the total flux of active-flavor neutrinos from 8B decay in the Sun is found to be 4.940.21+0.21(stat)0.34+0.38(syst) and the integral flux of electron neutrinos for an undistorted 8B spectrum is 1.680.06+0.06(stat)0.09+0.08(syst); the signal from (νx,e) elastic scattering is equivalent to an electron-neutrino flux of 2.350.22+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=(8.00.4+0.6)×105 eV2 and θ=33.92.2+2.4 degrees.


Comment: 45 pages, 36 figures in 49 eps files

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