McDonald, Arthur Bruce, 1943–, Canadian astrophysicist, Ph.D. California Institute of Technology, 1969. McDonald was a researcher at the Chalk River Nuclear Laboratories in Ottawa, Canada, from 1970 to 1982, when he joined the faculty at Princeton. In 1989, he left Princeton to join Queen's Univ. in Kingston, Ontario, where he is now research chair. McDonald was the joint recipient, with Takaaki Kajita, of the 2015 Nobel Prize in Physics for the discovery of neutrino flavor oscillation, which shows that neutrinos have mass. In 2002, McDonald and his team, using the underground detector at the Sudbury Neutrino Observatory, confirmed Kajita's discovery that neutrinos oscillated among their three different types by comparing the number of electron neutrinos detected to the total number of neutrinos detected. The discovery that neutrinos have mass provided the foundation for a better understanding of the evolution of the universe, the workings of the sun, and the mechanism of supernova explosions, and showed that the Standard Model of particle physics, in which neutrinos had no mass, was flawed.
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