Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory

Abstract

Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and un-oscillated portion of the neutrino flux. A total of 514 muon-like events are measured between -1 ≤ cos Θ zenith ≤ 0:4 in a total exposure of 2.30 x 1014 cm^2 s. The measured flux normalization is 1.22±0.09 times the Bartol three-dimensional flux prediction. This is the fi rst measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle cos Θ zenith > 0:4 is measured to be (3.31±0.01 (stat:) 0:09 (sys:)) x 10^-10 μ/s/cm^2.