The winners were announced by a committee at the Royal Swedish Academy of Sciences in Stockholm on Tuesday. McDonald and Kajita will split the 8 million Swedish kronor (almost $1.3 million Cdn) prize.

The academy said the two men won the prize for their contributions to experiments demonstrating that subatomic particles called neutrinos change identities, also known as "flavours." The neutrinos transform themselves between three types: electron-type, muon-type and tau-type.

The metamorphosis requires that neutrinos have mass, dispelling the long-held notion that they were massless. The academy said the discovery "has changed our understanding of the innermost workings of matter."

Kajita said his work was important because it showed there must be a new kind of physics beyond the so-called Standard Model of fundamental particles, which requires neutrinos to be massless.

Working at the Super-Kamiokande detector in Japan, Kajita, in 1998, showed that neutrinos captured at the detector underwent a metamorphosis in the atmosphere.

Meanwhile, researchers at the Sudbury Neutrino Observatory, as also known as SNOLAB, were looking at neutrinos that come from the sun. McDonald, who has been director of the observatory since 1989, discovered in 2001 that those neutrinos from the sun also changed their identities.

Read the full article on the CBC news website:
http://www.cbc.ca/news/technology/nobel-prize-physics-2015-1.3258178