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February 4, 2000

Brookhaven Lab Chemist Shares the 2000 Wolf Prize in Physics
With University of Tokyo Scientist For Research on Neutrinos

UPTON, NY - Raymond Davis Jr., whose career as a chemist spans 52 years at the U.S. Department of Energy's Brookhaven National Laboratory, will share the 2000 Wolf Prize in Physics with Masatoshi Koshiba, University of Tokyo, Japan. The Wolf Foundation has recognized the scientists "for their pioneering observations of astronomical phenomena by detection of neutrinos, which created the emerging field of neutrino astronomy." The $100,000 prize, to be shared by the two scientists, will be conferred by the President of Israel, Ezer Weizman, at a special ceremony in Jerusalem on May 21.

Davis was notified that he won the Wolf Prize while he was in Russia to receive the 1999 Bruno Pontecorvo Prize. Issued by the Joint Institute for Nuclear Research, the $1,000 Pontecorvo Prize was awarded to Davis "for the outstanding achievement in development of the chlorine-argon method for detection of solar neutrinos." This method was invented by Pontecorvo and Davis further developed it.

"I have been interested in studying neutrinos since 1948, when I first read about them in a review article by H.R. Crane, a physicist at the University of Michigan," Davis said. "Back then, it was a brand new field of study. It has captivated me for more than half a century."

Neutrinos, ghostlike particles that, until recently, have been thought to have zero mass, are produced in the nuclear reactions that provide the sun's energy. They rain down on each square inch of the earth at the rate of 65 billion per second. Davis first started investigating neutrinos that were produced in Brookhaven's Graphite Research Reactor and in a reactor at the Savannah River Technology Center in South Carolina in the 1950s. The particles remained elusive until the 1960s, when Davis achieved success in detecting solar neutrinos in a new experiment.

At the time, theorists believed that a solar neutrino produces radioactive argon when it interacts with a nucleus of chlorine. Davis developed an experiment based on this theory by placing a 100,000-gallon tank of perchloroethylene - a chemical commonly used by dry cleaners and a good source of chlorine - 4,800 feet underground in the Homestake Gold Mine in South Dakota. The chlorine target was located deep underground to protect it from cosmic rays, and the target had to be very big because the probability of capturing a neutrino in chlorine was ten quadrillion times smaller than detecting it in a nuclear reactor.

Despite these odds, Davis's experiment confirmed that the sun produces neutrinos, but only about one-third of the number of neutrinos predicted by theory. This extraordinary finding gave birth to a series of investigations by scientists around the world that confirmed the solar neutrino deficit, with a maximum of 60 percent of the expected number ever detected. To this day, experiments are ongoing to determine the cause of the deficit.

Wolf Prize co-recipient Masatoshi Koshiba led the design and construction of the Kamiokande detectors in Japan, which recorded the time of arrival, energy and direction of incoming neutrinos. Experiments that used these attributes provided strong hints that neutrinos have mass.

Raymond Davis Jr. earned a B.S. in 1937, and an M.S. in 1940, from the University of Maryland, and a Ph.D. in physical chemistry from Yale University in 1942. He served in the U.S. Air Force from 1942-46, and, from 1946-48, he worked as a chemist at Monsanto Chemical Company.

Davis started his career at Brookhaven Lab in 1948 as a scientist, then was promoted to chemist in 1953, received tenure in 1956, and became a senior chemist in 1964. He retired from Brookhaven in 1984, and he then became a research professor at the University of Pennsylvania. In addition, he has remained an active research collaborator at Brookhaven Lab. A member of the National Academy of Sciences, Davis has won numerous scientific awards, including the Tom W. Bonner Prize in 1988 and the W.K.H. Panofsky Prize in 1992.

The Wolf Foundation in Israel has awarded five Wolf Prizes annually since 1978 to outstanding scientists and artists "for achievements in the interest of mankind and friendly relations among peoples, irrespective of nationality, race, color, religion, sex, or political view." Davis will be the second honoree from Brookhaven Lab; Maurice Goldhaber, Brookhaven's former director and current distinguished scientist, shared the 1991 Wolf Prize in Physics with Valentine L. Telegdi of the Swiss Institute of Technology.

The U.S. Department of Energy's Brookhaven National Laboratory creates and operates major facilities available to university, industrial and government personnel for basic and applied research in the physical, biomedical and environmental sciences, and in selected energy technologies. The Laboratory is operated by Brookhaven Science Associates, a not-for-profit research management company, under contract with the U.S. Department of Energy.

NOTE TO LOCAL EDITORS: Raymond Davis is a resident of Blue Point, N.Y..

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