Benjamin W. Lee
Chris Quigg and Steven Weinberg

Benjamin W. Lee, head of the theoretical physics department at the Fermi National Accelerator Laboratory and professor of physics at the University of Chicago, was tragically killed in an automobile accident near Kewanee, Illinois on 16 June. He was travelling to the summer meeting of the Fermilab Program Advisory Committee in Aspen, Colorado. The other members of his family who were accompanying him were not seriously injured. Lee was widely regarded as one of the world's leading physicists working on the theory of elementary particles.

Born in Seoul, Korea in 1935, Lee came to the United States as a student, receiving his BS degree from Miami University of Ohio in 1956. His graduate work was at the University of Pittsburgh, where he received the MS degree in 1958, and at the University of Pennsylvania, where he worked under the direction of Abraham Klein, receiving the PhD degree in 1960. He became a naturalized US citizen in 1968. After several years at Pennsylvania and at the Institute for Advanced Study in Princeton, N.J.; in 1966 Lee accepted a professorship at the Institute for Theoretical Physics at the State University of New York, Stony Brook, which is directed by C. N. Yang. He served there until his move to Fermilab in 1973.

Lee had one of the broadest ranges of interests and research of any physicist of his generation, but he returned again and again to the study of symmetry principles and the weak interactions. He was one of the first of the physicists working on SU(6) and related symmetries in the mid-1960s to propose that these symmetries would find their natural expression through the algebra of currents. He then played a leading role in the development and applications of current algebra and phenomenological Lagrangians, culminating in the publication in 1972 of his monograph on Chiral Dynamics. Lee turned in the early 1970s to the fundamental problem of the renormalization of theories with spontaneously broken symmetry, such as the σ model, and developed ideas and techniques that were to serve him well in his later work on gauge theories.

Lee's involvement with gauge theories dated back to 1964. He was concerned about the fact that superconductors appear to provide a counterexample to the general theorem, which requires that spontaneous symmetry breaking is always accompanied with massless spin-zero bosons. With Klein, he wrote an article suggesting that the same might occur in relativistic theories. It was soon realized that this is indeed the case, provided the broken symmetry is a gauge symmetry, as it is in a superconductor. Lee continued to work on the quantization of spontaneously broken gauge theories. In 1971, after it had been shown by functional methods that these theories are renormalizable, Lee developed a proof of this result (for Abelian gauge theories) by operator methods. For theorists who were unfamiliar with the functional formalism, it was Lee's proof that really settIed the matter. In the following year, Lee and Jean Zinn-Justin completed the demonstration that renormalization does not spoil the cancellation of unphysical singularities in these theories.

Lee also made a major contribution to the application of this formalism to unified theories of the weak and electromagnetic interactions. His talk at the "Rochester" conference at Fermilab in 1972 and his review article with Ernest Abers have been instrumental in introducing physicists to this subject. Spurred by the discovery of neutral currents in 1973, Lee along with Mary K. Gaillard and Jonathan L. Rosner undertook a systematic survey of the experimental signatures of charmed mesons and baryons. Their report was circulated shortly before the discovery in November 1974 of the J/ψ particle, and immediately became the bible that guided subsequent experimental work. Even before the discovery of the J/ψ, Lee and Gaillard had used gauge-theory calculations of the KL - KS mass difference and the KL → γ&gamma decay rate to argue that the c-quark mass would have to be about 1.5 GeV or less, a prediction that appears to have been strikingly confirmed by the observed mass of the J/ψ. Lee and his Fermilab colleagues were among those who most actively elaborated and sharpened the theoretical understanding of the new hadrons.

Lee's decision to move permanently to Fermilab was a declaration of his faith in the laboratory and of his recognition of unity of theory and experiment. His brilliance, dedication, and deep understanding — not only of physics but of human nature — added immeasurably to the style and standards of a young laboratory. He attracted other outstanding people to the laboratory, and made of it a world center of theory as well as of experiment. He was a wise and trusted counselor to many experimentalists.

At the time of his death, Lee was in the midst of a period of enormous creativity. In the last six months of life he had explored the problems of CP violation, of lepton-number nonconservation, and of the high-energy limit of weak interactions in gauge theories, and had formulated a theory based on the enlarged gauge group SU(3)⊗U(1). He was just beginning a program of research on cosmology and was delighted with this opportunity to move into yet another field.

Lee felt a strong sense of gratitude to older physicists who had helped to advance his career, and he in turn took every possible opportunity to help the young physicists of the next generation to make their way in research. To him, the advance of physics was a common enterprise, in which the contributions of all deserved respect and encouragement. He will be keenly missed by the large number of physicists who learned so much from his work, and most poignantly, by those of us who had the privilege to know him and work with him.

Chris Quigg, Fermi National Accelerator Laboratory
Steven Weinberg, Harvard University

Published in Physics Today 30, 76 (September 1977).