PNNL

PNNL scientists contribute to Nobel-winning research

Arthur McDonald, a professor emeritus at Queen’s University. He and Takaaki Kajita of Japan are co-winners of the 2015 Nobel Prize in Physics for showing that particles called neutrinos spontaneously change from one type to another.
Arthur McDonald, a professor emeritus at Queen’s University. He and Takaaki Kajita of Japan are co-winners of the 2015 Nobel Prize in Physics for showing that particles called neutrinos spontaneously change from one type to another. Associated Press

Several researchers at Pacific Northwest National Laboratory played a role in the scientific work that led to the award Tuesday of the Nobel Prize for Physics.

The national lab in Richland is continuing work to learn more about neutrinos, a cosmic particle that whizzes through space at nearly the speed of light, passing easily through Earth and even your body.

Arthur McDonald of Canada and Takaaki Kajita of Japan were honored for showing that the tiny particles have mass. That’s the quality we 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.

McDonald conducted the work that won the Nobel Prize at the Sudbury Neutrino Observatory in Canada, where he oversaw hundreds of researchers from many other institutions.

One of them was PNNL physicist Brent VanDevender, who worked as a post-doctoral researcher with McDonald on the experiment that won McDonald the prize.

“I remember he had a superhuman ability to connect and engage with every member of that large collaboration,” VanDevender said in a statement.

He called McDonald “the epitome of scientific leadership. I can’t think of a better person for a Nobel Prize.”

Other PNNL employees who have worked with McDonald include Andrew Hime, a laboratory fellow, who has been working on the Sudbury neutrino experiment for 25 years, first at Los Alamos National Laboratory and now at PNNL.

“I couldn’t be more excited for Art,” Hime said.

Dick Kouzes, also a PNNL laboratory fellow, worked on the neutrino research while he was at Princeton University. Physicist John Orrell worked on it as a doctoral graduate student and physicist Bryan Fulsom worked on it for his master’s degree.

McDonald’s and Kajita’s work dispelled the long-held notion that neutrinos have no mass.

Neutrinos come in three types, or “flavors,” and what the scientists actually 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.

“A major discovery cannot be achieved in a day or two,” Kajita said. “It takes a lot of people and a long time.”

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

The existence of neutrinos was first proven 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 your 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 Sudbury, McDonald found that neutrinos coming from the sun also switched identities.

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 they weigh?

That’s the question scientists at PNNL are working to answer.

“The universe is full of neutrinos,” VanDevender said this spring when explaining one project. “There are so many of them that it matters how much they weigh.”

Scientists know that neutrinos, at most, weigh two-billionths of a proton. At that mass, they would outweigh all of the other normal matter in the universe like stars, planets and dust, and would affect the formation of large-scale structures like galaxy clusters, VanDevender said.

PNNL researchers are working on several projects to determine neutrino mass, with VanDevender the PNNL lead scientist on a project with other research institutions to infer the mass of the neutrino by measuring radiation from electrons.

This spring, scientists had a breakthrough toward that project, detecting radiation from individual electrons as they whirled around in a circle while while trapped in a magnetic field. Cyclotron radiation had been predicted in 1904 but never before measured at the level of individual fundamental particles.

The Associated Press contributed to this story.

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Information on VanDevender’s research on neutrino mass.

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