Arthur B. McDonald
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
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.