Physical Society Colloquium

Neutrino and Astro-Physics Measurements with the Sudbury Neutrino Observatory

Art McDonald

Queen's University

The Sudbury Neutrino Observatory (SNO) is a 1,000 tonne heavy-water-based neutrino detector in an ultra-clean environment created 2 km underground in a mine near Sudbury, Canada. Past measurements of the numbers of neutrinos from the Sun have been smaller than predicted by solar model calculations. This implied that the calculations of neutrinos produced by nuclear reactions in the Sun are incomplete or that some of the electron neutrinos produced in the Sun change to another flavor en route to earth. SNO has used neutrinos from ⁸B decay in the Sun to observe one neutrino reaction sensitive only to solar electron neutrinos and others sensitive to all active neutrino flavors and has found clear evidence for neutrino flavor change. This requires modification of the Standard Model for Elementary Particles and confirms solar model calculations with great accuracy. The implications of the SNO results to date and other recent neutrino results for particle physics and solar physics will be discussed. The SNO detector has now completed its operation and final data analysis is in progress. The subjects of that analysis and plans for future use of the SNO detector for the SNO+ experiment will be described. The expansion of the underground facility to create a long-term international laboratory (SNOLAB) with a broad future experimental capability for the detection of dark matter, double beta decay, lower energy solar neutrinos and geo-neutrinos will also be described.