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Reines, Frederick

REINES, FREDERICK

Frederick Reins was born in Patterson, New Jersey, on March 16, 1918. His parents, Israel Reines and Gussie (Cohen) Reines, met and married in New York City after emigrating from Russia. Israel worked as a weaver, started a silk mill after World War I, and later ran a country store in Hillburn, New York, where Fred spent much of his childhood. Fred, the youngest of four children, attended Union Hill (New Jersey) High School and the Stevens Institute of Technology (SIT; Hoboken, New Jersey). While at SIT he developed a lifelong love of vocal and dramatic performance and received a B.S. in Engineering in 1939 and an M.S. in Mathematical Physics in 1941. Reines continued his graduate studies at New York University and earned a Ph.D. in theoretical physics in 1944. He married Sylvia Samuels in 1950; they had two children.

Following completion of his Ph.D. program, Reines joined the Manhattan Project in the Theoretical Division of the Los Alamos Scientific Laboratory. He continued in the weapons testing program after the end of World War II. This work took him to Eniwetok Atoll, as director of the Operation Greenhouse experiments and included research on the effects of nuclear blasts at that location and at the Bikini and Nevada test sites.

While on a sabbatical-in-residence at Los Alamos in 1951, Reines pondered the possibility of detecting the neutrino, a particle postulated by Wolfgang Pauli in 1930. Although the neutrino postulate proved to be consistent with beta-decay observations, the neutrino itself, which carries no electrical charge, has zero or tiny mass, and interacts only weakly with matter, had never been detected and seemed to be well beyond the limits of detection. Shortly thereafter Reines and Clyde L. Cowan, Jr., who was also a Los Alamos physicist, joined forces in planning an effort to detect neutrinos following the detonation of a nuclear bomb. They set out to exploit a new technology, a large liquid scintillation detector, to distinguish neutrino-induced inverse-beta-decay events from the large background of other products of nuclear fission. In the fall of 1952 they realized that a nuclear fission reactor would also provide an abundant source of neutrinos. Their first attempt to detect neutrinos, with their detector adjacent to a reactor at the Hanford Engineering Works near Richland, Washington, in 1953, was inconclusive due to factors such as a large cosmic-ray muon background that mimicked inverse beta-decay reactions. They subsequently redesigned their detector and installed it in an underground location adjacent to a reactor at the Savannah River (South Carolina) Plant of the U.S. Atomic Energy Commission. The Reines-Cowen detector was separated by 11 meters of concrete from the reactor core and by 12 meters of overhead shielding from cosmicray muons. There, between February and June 1956, Reines and coworkers obtained unequivocal evidence that identified the neutrino as a free particle. Additional measurements at Savannah River later in 1956 and in 1963–1964 provided more evidence and secured a definitive value for the cross section for the inverse-beta-decay reaction.

In 1959, Reines left Los Alamos to become professor and head of the Physics Department at Case Institute of Technology in Cleveland, Ohio, where he undertook new neutrino research while continuing work previously begun at Los Alamos. Fission reactors continued to be an important tool in this work. For example, a twenty-year effort using reactor neutrinos to observe the direct elastic-scattering of neutrinos by electrons finally was brought to culmination in 1976 with the successful measurement of the tiny cross section for this reaction. In other reactor experiments that began at Los Alamos and bridged his time at Case, Reines and his coworkers observed both the "charged current" and the "neutral current" interactions of neutrinos with deuterons, completing these measurements in 1969 and 1979, respectively. The first studies of neutrino stability and of neutrino oscillations also employed reactor neutrinos.

Part of the experimental program begun at Case took Reines to deep underground locations, in the Morton Salt Company mine 600 meters beneath the shores of Lake Erie near Cleveland, and in a 3,200-meter-deep

gold mine near Johannesburg, South Africa, where reduced cosmic ray muon fluxes made it possible to study additional neutrino properties, to search for solar neutrinos, or to probe the limits of fundamental conservation laws such as conservation of charge and of baryon number. In 1964–1965 at the South African site, Reines and his coworkers were the first to observe muons produced in their detector by neutrinos generated in the earth's atmosphere by high-energy cosmic rays.

In 1966, Reines left Case to become founding dean of the School of Physical Sciences at the University of California, Irvine (UCI) campus, a position he held until he returned to full-time teaching and research in 1974. While at Irvine Reines served as spokesman for the Irvine Michigan Brookhaven (IMB) collaboration which operated a Cerenkov detector containing 8,000 tons of water in the aforementioned salt mine beginning in 1982. The primary motivation for this effort was to extend the measured lower limit on the lifetime of the proton. This experiment ran until 1991 without observing a proton decay. The lower limits determined for lifetimes of several proton decay channels provided a significant test of particle theories. In addition, this detector, along with a similar detector in Kamiokande, Japan, detected a burst of neutrinos from the supernova 1987A, confirming the role of neutrinos in stellar collapse.

Reines was appointed Distinguished Professor of Physics at UCI in 1987 and retired in 1988. He received many honors during his lifetime, among them the 1981 Oppenheimer Memorial Prize, the National Medal of Science, the 1992 Franklin Medal, the 1992W. K. H. Panofsky Prize of the American Physical Society, and the 1995 Nobel Prize in Physics ("for the detection of the neutrino"), which he shared with Martin Perl, discoverer of the tau lepton. His fame rests not only on the discoveries made by him and his coworkers and the experimental techniques that they pioneered but also on demonstrating that neutrino physics is both doable and immensely fruitful. Reines died in Orange, California, on August 26, 1998.

See also:Fermi, Enrico; Neutrino, Discovery of; Pauli, Wolfgang

Bibliography

Kropp, W.; Moe, M.; Price, L.; Schultz, J.; and Sobel, H.; eds. Neutrinos and Other Matters: Selected Works of Frederick Reines (World Scientific, Singapore, 1991).

Kropp, W. R.; Schultz, J.; and Sobel, H. W. "Obituary: Frederick Reines." Physics Today52 , 78–80 (1999).

Reines, F. "The Neutrino: From Poltergeist to Particle." Reviews of Modern Physics68 , 317–327 (1996).

Sutton, C. Spaceship Neutrino (Cambridge University Press, Cambridge, UK, 1992).

Robert G. Arns

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