Professor Jocelyn Monroe

Abstract:

A significant advance in the detection of neutrons and determination of their energy and direction of motion in a simple, compact device has been reported. The new detector can be used to determine the neutron flux, the energy distribution, and the direction of motion neutron for both fast and thermal neutrons. The detector is free of backgrounds from X-rays, gamma rays, beta particles, relativistic singly charged particles, and cosmic ray neutrons. It is capable of determining the location of a source of fission neutrons based on the characteristics of elastic scattering of neutrons by helium nuclei. The light collecting system included an ultraviolet lens and an image intensifier that was followed by a phosphor screen. Image analysis software to automate data analysis has also been developed.

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 unoscillated portion of the neutrino flux. A total of 514 muonlike events are measured between -1≤cos θzenith≤0.4 in a total exposure of 2.30×1014cm2s. The measured flux normalization is 1.22±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 θzenith>0.4 is measured to be (3.31±0.01(stat)±0.09(sys))×10-10μ/s/cm2. © 2009 The American Physical Society.