Posted on: Saturday, December 7, 2002

UH team expands big-bang theory

By Beverly Creamer
Advertiser Education Writer

An international team of scientists, including seven from the University of Hawai'i, has taken a giant step forward in understanding the big-bang theory and the evolution of life.

Their work involves new insight into neutrinos, the smallest building blocks of all matter.

After six months of research at a new underground neutrino detector near the central Japan city of Toyama, the team announced yesterday that neutrinos have mass and are capable of morphing from one type to another.

"It would be like a lion running along and slowly morphing into a tiger, and then into a leopard and back again," said John Learned, a UH professor of physics and astronomy and a member of the Hawai'i team that joined more than 90 U.S. and Japanese scientists in experiments at KamLAND in Japan.

"We don't know of anything else that has this peculiar property of changing into one another as they fly along. No other particles in the universe go through this bizarre business."

The discoveries mean a major shakeup in the Standard Model of Particle Physics, a foundation for the last 30 years. And they mean science can begin to explain why there was excess matter left over after the big bang — which became life. Current theory has the universe expanding after the big bang, but that, too, may be in for revision.

"People suspect neutrinos may have been involved in generating the excess of matter after the big bang," said Learned. "Neutrinos may have been essential in the process of our creation."

UH has long been involved in neutrino research, playing a prominent role in the 1987 discovery of neutrinos from Supernova 1987A, which heralded the birth of neutrino astronomy.

The Hawai'i researchers also took part in the announcement four years ago from the Super-Kamiokande Experiment research team — predecessor to KamLAND — that gave the first clear indication neutrinos have mass and can oscillate, or change type.

The new research verifies and expands upon that earlier work.

"The importance of this has to do with completing a picture," Learned said. "We know what's there, and now we have to get in and do the details. It's like the Hawaiians showing up in their canoes and first making a quick tour of the islands: They have the lay of the land but they haven't explored it yet."

Stuart Freedman, a nuclear physicist at the Lawrence Berkeley National Laboratory, one of many partners in the research, agreed.

"While the results from earlier neutrino experiments such as those at Sudbury Neutrino Observatory and Super-Kamiokande offered compelling evidence of neutrino oscillation, there were some escape clauses. Our results close the door on those clauses."

Neutrinos — the three types include electron, muon and tau — are three of the six fundamental constituents of matter. "Up until recently they were thought to have zero mass," Learned said, "and now we find that they do have some mass."

While their mass is small, he said, it contributes significantly to the total mass of the universe. "There is as much mass in neutrinos as in all the stars you see in the sky at night," he said.

In more detail, neutrinos are sub-atomic particles produced during nuclear fusion, the reaction that lights the sun and stars. Anti-neutrinos are created in fission

reactions, such as those that drive nuclear power plants. Since anti-neutrinos are also produced during the decay of radioactive uranium in the Earth's crust, the new findings may point the way to the first direct measurements of the total radioactivity of the planet.

Participating UH scientists from the departments of physics and astronomy include Peter Gorham, Gene Guillian, Jelena Maricic, Shigenobu Matsuno and Sandip Pakvasa. Stephen Olsen of UH is principal investigator of a U.S. Department of Energy high energy physics grant awarded to UH, from which the project is supported.

KamLAND, or Kamioka Liquid Scintillator Anti-Neutrino Detector, is the world's largest low-energy anti-neutrino detector. It is deep in a cavern beneath the mountains on Honshu, and was built in a 1998 collaboration between the Japanese and U.S. governments. The international scientific collaboration is led by Atsuto Suzuki of Tohuku University's Research Center for Neutrino Science.

Reach Beverly Creamer at bcreamer@honoluluadvertiser.com or 525-8013.