Direct Evidence for Neutrino Flavor Transformation from Neutral-Current Interactions in the Sudbury Neutrino Observatory

Abstract

Observations of neutral-current n interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current (NC), elastic scattering, and charged current reactions and assuming the standard 8B shape, the ne component of the 8B solar flux is Φe = 1.76 +0.05 -0.05 (stat)+0.09 -0.09(syst) x 10^6 cm^-2 s^-1 for a kinetic energy threshold of 5 MeV. The non-ve component is Φe = 3.41 +0.45 -0.45(stat) +0.48 -0.45(syst) x 10^6 cm^-2 s^-1, 5.3o greater than zero, providing strong evidence for solar ve flavor transformation. The total flux measured with the NC reaction is ΦNC = 5.09 +0.44 -0.43(stat) =0.46 -0.43(syst) x 10^6 cm^-2 s^-1, consistent with solar models.