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Nobel Prize in Physics honors discovery of neutrino oscillations

Takaaki Kajita and Arthur B. McDonald share award for work that changed the way scientists see the universe

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The Nobel Prize in Physics has been jointly awarded to Takaaki Kajita and Arthur B. McDonald, for discoveries that proved that neutrinos have mass. The Royal Swedish Academy of Sciences announced the decision at a press conference Tuesday morning. Kajita and McDonald will share an award of 8 million Swedish Krona ($964,000).

Kajita, a professor at the University of Tokyo, and McDonald, of Queen's University in Canada, each led experiments that showed that neutrinos — subatomic particles created from decayed radioactive elements — can change identities and must therefore carry mass. Neutrinos had long been considered to be massless, under the Standard Model of particle physics, but Kajita and McDonald's discoveries showed that the Standard Model alone cannot explain the laws governing how fundamental particles behave.

"crucial to our view of the universe."

"The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe," the Nobel Prize committee said in a statement Tuesday.

Working at the Super-Kamiokande observatory in Japan, Kajita showed that neutrinos from the atmosphere switch between two identities — a phenomenon known as neutrino oscillations. At the Sudbury Neutrino Observatory in Canada, McDonald led research that showed that neutrinos produced by the sun changed identity by the time they reached the observatory. Scientists had previously believed that neutrinos produced in the sun simply disappeared on their way to Earth.

The discovery of neutrino oscillations has spawned a new field of neutrino research that may yield further insights into how the universe works. "New discoveries about their deepest secrets are expected to change our current understanding of the history, structure and future fate of the universe," the Nobel Prize committee added.

Following the announcement, the committee published a brief phone interview with Kajita. It is embedded below.