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Neutrino discovery earns Noble Prizes

Scientists found that particles have mass
Scientists found that particles have mass

STOCKHOLM – Japanese and Canadian scientists won the Nobel Prize in physics Tuesday for discovering a basic fact about tiny cosmic particles that whiz through your body by the trillions every second: They have mass.

Takaaki Kajita and Arthur McDonald were honored for showing that the particles, called neutrinos, spontaneously change from one type to another. That shows that they have mass, the quality we typically experience as weight.

By uncovering this “chameleon-like” nature of neutrinos, the laureates solved a long-standing puzzle in particle physics that could alter our grasp of the cosmos, the Royal Swedish Academy of Sciences said.

“The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe,” the academy said.

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, Canada.

“Neutrinos are among the fundamental particles (which) we do not know how to subdivide any further,” McDonald told reporters in Stockholm by phone. “Therefore, their position within the models of physics at the most fundamental level is very important,” he said.

“When you do not know whether they have mass, it’s otherwise difficult to understand how to incorporate them into those theories that give us a more complete understanding of the world of physics at the most fundamental level. Discovering this property helps us tremendously in this regard.”

Kajita seemed flummoxed at a news conference organized by his university. “My mind has gone completely blank. I don’t know what to say,” he said after taking the stage.

After getting his composure back, he stressed that many people had contributed to his work, and that there was much work still to do.

“The universe where we live in is still full of unknowns. A major discovery cannot be achieved in a day or two. It takes a lot of people and a long time. I would like to see young people try to join our pursuit of mystery solving,” he said.

Neutrinos come from a variety of sources in the cosmos and on Earth. Most that reach Earth from elsewhere were created by nuclear reactions inside the sun. Their existence was first proven in 1956.

They come in three kinds, or flavors, and the laureates showed they oscillate from one flavor to another. That dispelled the long-held notion that they were massless.

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

Three years later, while working at the Sudbury Neutrino Observatory in Canada, McDonald found that neutrinos coming from the sun also switched identities.

Each form of neutrino has a different mass. The masses haven’t been measured precisely.

Neutrinos are the second most abundant particles in the universe after photons, “so any property of neutrinos can have dramatic repercussions on the life of the universe and on its evolution,” said Antonio Ereditato, director of the Albert Einstein Center for Fundamental Physics at the University of Bern, Switzerland. “This is really one of the milestones in our understanding of nature.”

Joseph Lykken, deputy director of the Fermi National Accelerator Laboratory near Batavia, Illinois, said the Nobel laureate’s discoveries “put the neutrinos front and center as one of the big mysteries of physics.”

The work “really inspired a whole global community of scientists to drop what they were doing and try to understand the neutrino,” he said. “That really launched neutrinos as a major activity in particle physics.”

The winners will split the $960,000 prize money. Each winner also gets a diploma and a gold medal at the prize ceremony on 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 on Wednesday, literature on Thursday, the Nobel Peace Prize on Friday and the economics award next Monday.

Malcolm Ritter reported from New York. Malin Rising in Stockholm, Mari Yamaguchi in Tokyo and Frank Jordans in Berlin contributed to this report.



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