Independent Measurement of the Total Active 8B Solar Neutrino Flux Using an Array of 3He Proportional Counters at the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54(+0.33/-0.31 stat, +0.36/-0.34 syst) x 10^6 cm^-2 s^-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Delta m^2 = 7.59(+0.19/-0.21) x 10^-5 eV^2 and theta = 34.4(+1.3/-1.2) degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.