Electron energy spectra, fluxes, and day-night asymmetries of 8 B solar neutrinos from measurements with NaCl dissolved in the heavy-water detector at the Sudbury Neutrino Observatory

Results are reported from the complete salt phase of the Sudbury Neutrino Observatory experiment in which NaCl was dissolved in the $^{2}mathrm{H}$${}_{2}text{O}$ (“${text{D}}_{2}text{O}$”) target. The addition of salt enhanced the signal from neutron capture as compared to the pure ${text{D}}_{2}text{O}$ 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 ${10}^{6}{text{cm}}^{ensuremath{-}2}{text{s}}^{ensuremath{-}1}$, the total flux of active-flavor neutrinos from $^{8}mathrm{B}$ decay in the Sun is found to be ${4.94}_{ensuremath{-}0.21}^{+0.21}{text{(stat)}}_{ensuremath{-}0.34}^{+0.38}text{(syst)}$ and the integral flux of electron neutrinos for an undistorted $^{8}mathrm{B}$ spectrum is ${1.68}_{ensuremath{-}0.06}^{+0.06}{text{(stat)}}_{ensuremath{-}0.09}^{+0.08}text{(syst)}$; the signal from (${ensuremath{nu}}_{x},e$) elastic scattering is equivalent to an electron-neutrino flux of ${2.35}_{ensuremath{-}0.22}^{+0.22}{text{(stat)}}_{ensuremath{-}0.15}^{+0.15}text{(syst)}$. 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 $ensuremath{Delta}{m}^{2}=({8.0}_{ensuremath{-}0.4}^{+0.6})ifmmodetimeselsetexttimesfi{}{10}^{ensuremath{-}5}$ eV${}^{2}$ and $ensuremath{theta}=33.{9}_{ensuremath{-}2.2}^{+2.4}$ degrees.