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15 Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA

98195 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 com- pared to the pure D2O detector. By making a statistical separation of charged-current events from other types based on event-isotropy criteria, the e?ective electron recoil energy spectrum has been extracted. In units of

106 cm?2 s?1 , the total ?ux of active-?avor neutrinos from

8 B decay in the Sun is found to be 4.94+0.21 ?0.21(stat)+0.38 ?0.34(syst) and the integral ?ux of electron neutrinos for an undistorted

8 B spectrum is 1.68+0.06 ?0.06(stat)+0.08 ?0.09(syst);

the signal from (νx,e) elastic scattering is equivalent to an electron-neutrino ?ux 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 e?ects 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-?t values for two-neutrino mixing parameters are ?m2 = (8.0+0.6 ?0.4) * 10?5 eV2 and θ = 33.9+2.4 ?2.2 degrees. PACS numbers: 26.65.+t, 14.60.Pq, 13.15.+g, 95.85.Ry I. INTRODUCTION Results from the completed second phase of the Sudbury Neutrino Observatory (SNO) [1] are presented in this paper. The second phase began in June of

2001 with the addition of ?2000 kg of NaCl [2] to SNO'

s ?1000 tonnes of D2O, and ended in October

2003 when the NaCl was removed. The ad- dition of the salt enhanced SNO'

s ability to detect solar

8 B neutrinos in three ways. First, the neutron capture e?ciency increased by nearly three-fold, allowing a statistically pre-

2 cise measurement of the neutral-current (NC) disintegration of deuterons by solar neutrinos. Second, the total energy of the γ-rays from the neutron capture on

35 Cl is 2.32 MeV above the energy of the single γ from the capture on deuterons. This higher γ-ray energy approximately corresponds to a

1 MeV upward shift in the observed energy peak for neutrons and al- lows a precise measurement that is well above the low energy radioactive backgrounds to be made. Lastly, and perhaps most importantly, the isotropy of the photomultiplier tube (PMT) hit distribution on the geodesic array from multiple γ-rays emitted after neutron capture on

35 Cl is signi?cantly di?erent from that produced by Cherenkov light emitted by a single relativistic electron. Hence, neutrons from the NC reaction and electrons from the charged-current (CC) interaction can be separated statistically without any assumptions about the underlying neutrino energy spectrum. Results from the ?rst SNO phase [3C5], using pure D2O in the target volume, con?rmed earlier measurements [6C9] of an observed de?cit of solar electron-type neutrino ?ux compared to solar model expectations [10, 11] but additionally demon- strated, through measurement of the total active

8 B solar ?ux, that neutrinos undergo ?avor transformation in transit to ter- restrial detectors. Initial measurements of the total active

8 B solar ?ux, based on the ?rst 254.2 live days of the salt data set, have been published [12] and con?rm and improve on results from the ?rst D2O phase measurements [3C5]. In particular, the sta- tistical discrimination of CC and NC events with salt enabled an independent measure of the total active