His own investigations, throughout his long career, contributed broadly and seminally to our understanding of the neutrino. For the first detection of the neutrino, accomplished with his Los Alamos Scientific Laboratory colleague Clyde L. Cowan Jnr in 1956, Reines shared the 1995 Nobel Prize in Physics with Martin Perl.
The neutrino was postulated by Wolfgang Pauli in 1930 to solve the problem of the apparent violation of conservation laws in nuclear decays. It was then thought by most physicists to be undetectable. This was philosophically intolerable to Reines; he felt the neutrino would have to be directly observed to achieve the status of a real particle.
Following the neutrino's direct observation, Reines vigorously pursued its study, achieving many "firsts" in the exploration of the neutrino's properties, and eventually saw "neutrino physics" mature into a field of its own.
Reines was born in Paterson, New Jersey in 1918, of parents who had emigrated to the United States from Russia. In his early years he had a strong interest in literature, music and theatre. While in college, he performed major solo roles in the Messiah and other oratorios. His vocal abilities were so highly promising that he was encouraged to consider a career in singing. Although he focused his attention and considerable energies on science, he retained a lifelong interest in the arts, performing in later years with the chorus of the Cleveland Symphony Orchestra.
After receiving an undergraduate degree in Engineering and a Master of Science in Mathematical Physics from Stevens Institute of Technology, Reines undertook graduate study in physics at New York University. There he wrote a theoretical PhD thesis on nuclear fission. The topic was timely and in 1944 he was recruited to work on the Manhattan Project in the Theoretical Division of the Los Alamos Scientific Laboratory under Richard Feynman. A year later he was a group leader and embarked on a career at LASL which spanned 15 years and included direction of the Atomic Energy Commission's Operation Greenhouse experiments on Eniwetok Atoll, and the study of bomb tests on Bikini and in Nevada.
While Reines had begun to think about detecting the neutrino as early as 1947, it was not until 1951 that ideas for the experiment began to crystallise. His first idea was to use a nuclear explosion as a neutrino source. Soon, however, Reines and Cowan conceived the key idea of using a unique time "signature" of the particles produced by the neutrino's capture. This now common technique reduced interfering backgrounds and made possible the use of a fission reactor as the neutrino source. Success was achieved at the then newly constructed reactor at the Savannah River Plant in South Carolina.
In 1959, Reines became Professor of Physics and Head of the Physics Department of the Case Institute of Technology in Cleveland, Ohio. The productive research group he built there embarked on several series of experiments studying reactor neutrinos, searching for solar neutrinos, and pursuing underground detection of neutrinos produced by high-energy cosmic rays in the atmosphere. He also pursued his interest in studying conservation laws. His achievements during this period included the first detection of neutrinos produced in the earth's atmosphere, studies leading to the first observation of neutrino-electron elastic scattering, and ever more sensitive studies of the stability of the proton.
In 1966, Reines moved, and brought the core of his Neutrino Group to the newly built University of California campus at Irvine, where he became the founding Dean of the School of Physical Sciences and where he remained for the rest of his professional career. He became Distinguished Professor in 1987 and Professor Emeritus in 1988. While at UCI, he continued his relentless pursuit of the neutrino, and the study of conservation laws.
A major programme of the era was the IMB (Irvine-Michigan-Brookhaven) experiment, conducted with an 8,000-metric-ton water "Cherenkov" detector built 600 metres deep in a salt mine near Cleveland. This experiment put the then most restrictive limits on proton decay, obtained evidence for an atmospheric neutrino anomaly (recently shown to demonstrate the existence of mass for the neutrino), and made (together with the Kamiokande Experiment in Japan) the serendipitous detection of a burst of neutrinos from Supernova 1987A. This latter observation is seen by many as the birth of Neutrino Astronomy.
In his contacts with colleagues, students and co-workers, Reines was a constant source of ideas, stimulation and motivation. He was very generous in extending resources to colleagues to pursue their own ideas. This led to some outstanding research and advances in musical acoustics, in accelerator and underground neutrino physics, and in the first observation of the rare phenomenon double beta decay.
Reines's physical stature, booming voice and natural, imposing stage presence invariably commanded attention. However, his interactions with people, especially undergraduates, were warmed by his penchant for the lighthearted use of quips, puns, riddles and the poems he was so fond of fashioning and reciting.
William R. Kropp Jonas Schultz and Henry W. Sobel
Frederick Reines, physicist: born Paterson, New Jersey 16 March 1918; Staff member and Group Leader, Theoretical Division, Los Alamos Science Laboratory 1944-59; Professor of Physics and Head of Physics Department, Case Institute of Technology 1959-66; Professor of Physics, University of California, Irvine 1966-88 (Emeritus), Founding Dean, Physical Sciences 1966-74; married 1940 Sylvia Samuels (one son, one daughter); died Orange, California 26 August 1998.