The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass".  Art McDonald led the Sudbury Neutrino Observatory Project that solved the long-standing solar neutrino problem by showing that it was caused by an unexpected property of neutrinos: they have mass. CENPA physicists contributed to this experiment, in particular designing and building an array of neutron detectors to make SNO sensitive to all flavors of neutrinos.