Cosmic-particle work earns Nobel

2 scientists prove neutrinos have mass, share physics prize

Takaaki Kajita of Japan, director of the Institute for Cosmic Ray Research and professor at the University of Tokyo, speaks Tuesday after learning he won the Nobel Prize in physics for the discovery of neutrino oscillations.
Takaaki Kajita of Japan, director of the Institute for Cosmic Ray Research and professor at the University of Tokyo, speaks Tuesday after learning he won the Nobel Prize in physics for the discovery of neutrino oscillations.

STOCKHOLM -- Two scientists won the Nobel Prize in physics Tuesday for discoveries about a cosmic particle that whizzes through space at nearly the speed of light, passing easily through Earth and even human bodies.

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AP/The Canadian Press

This April 11, 2008 photo shows scientist Arthur McDonald during his investiture as Officer to the Order of Canada at Rideau Hall in Ottawa, Ontario. McDonald, a professor emeritus at Queen's University in Kingston, Ontario, and the director of the Sudbury Neutrino Observatory in northern Ontario, is a co-winner of this year's 2015 Nobel Prize for Physics.

Takaaki Kajita of Japan and Arthur McDonald of Canada were honored for showing that these tiny particles, called neutrinos, have mass. That's the quality people typically experience as weight.

"The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe," the Royal Swedish Academy of Sciences said in awarding the prize.

The work dispelled the long-held notion that neutrinos had no mass.

Neutrinos come in three types, or "flavors," and what the scientists showed is that neutrinos spontaneously shift between types. That, in turn, means they must have mass.

Kajita, 56, is director of the Institute for Cosmic Ray Research and professor at the University of Tokyo. McDonald, 72, is a professor emeritus at Queen's University in Kingston, Ontario.

McDonald told reporters in Stockholm by phone that the discovery helped scientists fit neutrinos into theories of fundamental physics.

Kajita -- who initially told a news conference at his university that "my mind has gone completely blank. I don't know what to say" -- went on to stress that many people had contributed to his work.

"The universe where we live in is still full of unknowns," he said. "A major discovery cannot be achieved in a day or two. It takes a lot of people and a long time."

The existence of neutrinos was first proved in 1956. They come from a variety of sources in the cosmos, on Earth and in Earth's atmosphere. Most that reach Earth were created by nuclear reactions inside the sun. Trillions pass through a human body every second.

Kajita showed in 1998 that neutrinos created in Earth's atmosphere and captured at the Super-Kamiokande detector in Japan had changed flavors. Three years later, while working at Canada's Sudbury Neutrino Observatory, McDonald found that neutrinos coming from the sun also switched identities.

"It changes our understanding of the fundamentals of particle physics, and particles make up everything in the universe," said Robert Brown, chief executive officer of the American Institute of Physics.

Antonio Ereditato, director of the Albert Einstein Center for Fundamental Physics at the University of Bern, Switzerland, declared, "This is really one of the milestones in our understanding of nature."

The findings "really inspired a whole global community of scientists to drop what they were doing and try to understand the neutrino," said Joseph Lykken, deputy director of the Fermi National Accelerator Laboratory in Batavia, Ill.

Still unknown: Just how much do neutrinos weigh?

"Neutrinos are a million times lighter than an electron, which is a charged version of a neutrino," said Guido Drexlin, a neutrino expert at the Karlsruhe Institute of Technology in Germany.

Determining their weight is something his team hopes to start working on next year.

The Nobel winners will split the prize money, about $960,000. Each winner also gets a diploma and a gold medal at the prize ceremony Dec. 10.

On Monday, the Nobel Prize in medicine went to scientists from Japan, the U.S. and China who discovered drugs that are now used to fight malaria and other tropical diseases.

The prize announcements continue with chemistry today, literature Thursday, the Nobel Peace Prize on Friday and the economics award Monday.

Information for this article was contributed by Malin Rising, Mari Yamaguchi and Frank Jordans of The Assocaited Press.

A Section on 10/07/2015

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