Observations of neutral-current ν interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current, elastic scattering, and charged current reactions and assuming the standard 8 B shape, the

The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates. For charged current events, assuming an undistorted 8B spectrum, the night minus day rate is 14.0%+/-6.3%(+1.5%)(-1.4%) of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the nu(e) asymmetry is found to be 7.0%+/-4.9%(+1.3%)(-1.2%). A global solar neutrino analysis in terms of matter-enhanced oscillations of two active flavors strongly favors the large mixing angle solution.

Solar neutrinos from (8)B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of nu(e)'s is measured by the CC reaction rate to be straight phi(CC)(nu(e)) = 1.75 +/- 0.07(stat)(+0.12)(-0.11)(syst) +/- 0.05(theor) x 10(6) cm(-2) s(-1). Comparison of straight phi(CC)(nu(e)) to the Super-Kamiokande Collaboration's precision value of the flux inferred from the ES reaction yields a 3.3 sigma difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non- nu(e) component in the solar flux. The total flux of active 8B neutrinos is determined to be 5.44+/-0.99 x 10(6) cm(-2) s(-1).

The Sudbury Neutrino Observatory (SNO) used an array of 3 He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (ν x ) 8 B solar neutrino flux. This technique is independent of previous methods employed by SNO The Sudbury Neutrino Observatory [1] detects 8 B solar neutrinos through three reactions: charged-current interactions (CC) on deuterons, in which only electron neutrinos participate; neutrino-electron elastic scattering (ES), which are dominated by contributions from electron neutrinos; and neutral-current (NC) disintegration of the deuteron by neutri-

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The Sudbury Neutrino Observatory (SNO) has precisely determined the total active (ν x ) 8 B solar neutrino flux without assumptions about the energy dependence of the ν e survival probability. The measurements were made with dissolved NaCl in the heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21 ± 0.27 (stat) ± 0.38 (syst) × 10 6 cm −2 s −1 , in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields ∆m 2 = 7.1 +1.2 −0.6 × 10 −5 eV 2 and θ = 32.5 +2. ES).Only electron neutrinos produce charged-current interactions (CC), while the neutral-current (NC) and elastic scattering (ES) reactions have sensitivity to non-electron flavors. The NC reaction measures the total flux of all active neutrino flavors above a threshold of 2.2 MeV. SNO previously measured the NC rate by observing neutron captures on deuterons, and found that a Standard-Model description with an undistorted 8 B neutrino spectrum and CC, ES, and NC rates due solely to ν e interactions was rejected [2, 3]. This Letter presents measurements of the CC, NC, and ES rates from SNO's dissolved salt phase.The addition of 2 tonnes of NaCl to the kilotonne of heavy water increased the neutron capture efficiency and the associated Cherenkov light. The solution was thoroughly mixed and

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B. AHARMIM et al.PHYSICAL REVIEW C 75, 045502 (2007) This article provides the complete description of results from the Phase I data set of the Sudbury Neutrino Observatory (SNO). The Phase I data set is based on a 0.65 kiloton-year exposure of 2 H 2 O (in the following denoted as D 2 O) to the solar 8 B neutrino flux. Included here are details of the SNO physics and detector model, evaluations of systematic uncertainties, and estimates of backgrounds. Also discussed are SNO's approach to statistical extraction of the signals from the three neutrino reactions (charged current, neutral current, and elastic scattering) and the results of a search for a day-night asymmetry in the ν e flux. Under the assumption that the 8 B spectrum is undistorted, the measurements from this phase yield a solar ν e flux of φ(ν e ) = 1.76 6 cm −2 s −1 . The sum of these components provides a total flux in excellent agreement with the predictions of standard solar models. The day-night asymmetry in the ν e flux is found to be A e = 7.0 ± 4.9 (stat.) +1.3 −1.2 % (syst.), when the asymmetry in the total flux is constrained to be zero.