Art McDonald

Queen's University

Arthur Bruce McDonald is a Canadian astrophysicist and Director Emeritus of SNOLAB at Queen's University. He led the Sudbury Neutrino Observatory (SNO) experiment in Ontario, Canada, which solved the longstanding solar neutrino problem — the observed deficit of electron neutrinos from the sun. SNO demonstrated that neutrinos change flavour as they travel, a phenomenon called neutrino oscillation, which conclusively proved that neutrinos have nonzero mass. This discovery fundamentally altered the Standard Model of particle physics and opened new questions about the nature of dark matter. McDonald shared the 2015 Nobel Prize in Physics with Takaaki Kajita of the University of Tokyo. His experimental techniques — deploying 1000 tonnes of heavy water 2 km underground — set a new standard for low-background physics and are directly applied in rare-event searches relevant to nuclear energy, neutrino-based geology, and fundamental physics research programs.