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

TL;DR

This paper reports the measurement of atmospheric neutrino-induced muon flux at the Sudbury Neutrino Observatory, providing insights into neutrino oscillations and cosmic ray muon flux at a deep underground site.

Contribution

First measurement of neutrino-induced muon flux where neutrino oscillations are minimized, confirming consistency with previous oscillation parameters.

Findings

Measured muon flux normalization is 1.22 times the Bartol prediction.

Zenith distribution aligns with known atmospheric neutrino oscillation parameters.

Cosmic ray muon flux at SNO is quantified at a specific zenith angle.

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 $-1 \le \cos{\theta}_{\rm zenith} \le 0.4$ in a total exposure of 2.30\times 10^{14}$ cm$^{2}$ s. The measured flux normalization is $1.22 \pm 0.09$ times the Bartol three-dimensional flux prediction. This is the first 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 $\cos{\theta}_{\rm zenith} > 0.4$ is measured to be $(3.31 \pm 0.01 {\rm (stat.)} \pm 0.09 {\rm (sys.)}) \times 10^{-10}~\mu$/s/cm$^{2}$.