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Arthur B. McDonald
The Nobel Prize in Physics 2015
Born: 29 August 1943, Sydney, Canada
Affiliation at the time of the award: Queen's University, Kingston, Canada
Prize motivation: "for the discovery of neutrino oscillations, which shows that neutrinos have mass."
Prize share: 1/2
Arthur McDonald was born in Sydney, Nova Scotia, Canada. He studied at Dalhousie University, Nova Scotia and then at the California Institute of Technology, Pasadena, United States, where he earned his doctorate in 1969. His doctoral advisor was future Nobel Laureate William Fowler. He worked at the Chalk River Nuclear Laboratories near Ottawa until 1982 when he became a professor at Princeton University. Since 1989 he is affiliated with Queen's University at Kingston, Ontario. Arthur McDonald is married with four children.
The Standard Model used by modern physics has three types of a very small and elusive particle called the neutrino. In an experimental facility in a mine in Canada in 2000, Arthur McDonald studied neutrinos created in nuclear reactions in the sun. Measurements showed deviations, which were explained by the neutrinos switching between the different types. This means that they must have mass. The Standard Model, however, is based on neutrinos lacking mass and the model must be revised.