Contacts:
Cheryl Ernst, 808 956-8856, ernst@hawaii.edu, University Relations
John Learned, 808 956-2964, jgl@uhheph.phys.hawaii.edu, Department of Physics and Astronomy


Mass and Oscillations Discovered for Elusive Neutrino

A team of Japanese and American physicists have produced evidence of mass and oscillations in neutrinos, elementary particles that individually have the smallest mass yet collectively may account for much of the mass of the universe. In a paper to be presented at the Neutrino '98 Conference in Japan on June 5 and submitted to the leading physics journal, the scientists present evidence that the ghostly elementary particles called neutrinos do possess mass and that they alternately change their identities in time as they travel.
The results come from the first two years of data from Super-Kamiokande, a $100 million experiment in a 12.5-million-gallon, stainless steel-lined cavity carved out beneath the Japanese alps, filled with ultra pure water and observed by 13,000 large area light detectors.

One of the three kinds of neutrinos, the muon flavor, has been found to disappear and reappear as it travels hundreds of kilometers through the earth. The energy and flight distance, from neutrino production in the atmosphere by cosmic radiation to the underground instrument, provide a measure of the difference between neutrino masses. This mass, while the smallest yet observed for elementary particles, is still sufficient that the relic neutrinos made in staggering numbers at the time of the Big Bang, account for much of the mass of the universe.

"These new results could prove to be the key to finding the holy grail of physics, the unified theory," observes University of Hawaii Professor of Physics and Astronomy John Learned, one of the authors. "Neutrinos cannot now be neglected in the bookkeeping of the mass of the universe. One only gets such great data once or twice in a professional lifetime, maybe never."

The Super-Kamiokande Collaboration will make a major statement June 5 at the Neutrino '98 Conference in Takayama, Japan. (See the XVIII International Conference on Neutrino Astrophysics and Astrophysics web site at www-sk.icrr.u-tokyo.ac.jp). A paper is being submitted at the time of this release to Physical Review Letters, the premier journal of physics.

The collaboration is led by University of Tokyo's Institute for Cosmic Ray Research and includes six U.S. groups (Boston University; University of California, Irvine; University of Hawai'i; Louisiana State University; State University of New York at Stony Brook; and the University of Washington) and eight from Japan (Gifu University, High Energy Research Organization (KEK), Kobe University, Niigata University, Osaka University, Tohoku University, Tokai University and Tokyo Institute of Technology) as well as other collaborators from both countries.

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