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Solar neutrinos from 8B 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 νe’s is measured by the CC reaction rate to be φCC(ve) = 1.75 ± 0.07(stat)+0.12−0.11(syst) ± 0.05(theor) × 106 cm−2s−1. Comparison of φCC(ve) to the Super-Kamiokande Collaboration’s precision value of the flux inferred from the ES reaction yields a 3.3σ difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non-ve component in the solar flux. The total flux of active 8B neutrinos is determined to be 5.44 ± 0.99 × 106 cm−2s−1. © 2001 The American Physical Society.

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Physical Review Letters

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