Gerson Goldhaber died at his home in Berkeley, California, on 19 July 2010 after a long struggle with pneumo-nia. His research accomplishments stretched from the first observation of antiproton annihilation to participation more than 50 years later in the discovery that the universe’s expansion is accelerating.
Gerson was born 20 February 1924 in Chemnitz, Germany. His parents fled from Germany in the 1930s to Cairo, Egypt. After completing high school there in 1942, Gerson attended the Hebrew University in Jerusalem, from which he received an MS in physics in 1947. He married Sulamith (Sula) Low in the same year. From Jerusalem they moved to the University of Wisconsin, where they obtained their PhDs, his in 1950 under the supervision of Hugh Richards. In his thesis, he measured nuclear gamma-ray emission using photographic emulsions. Following an instructorship at Columbia University, Gerson moved to the University of California, Berkeley, in 1953, where he remained for the rest of his career.
Working with Sula and other collaborators, including Gösta Ekspong, in 1955 Gerson found an event in which an antiproton interaction in an emulsion released more energy than was carried in by the projectile. The finding demonstrated that the negatively charged particle discovered by the team led by Emilio Segrè and Owen Chamberlain not only had the mass expected for an antiproton but had the special characteristic expected for antimatter: It annihilated when it came into contact with ordinary matter. Antiproton annihilations produced pions prolifically, and correlations between like-sign and unlike-sign pion pairs showed different patterns. Gerson and Sula, working with Wonyong Lee and Abraham Pais in 1960, explained that the correlation was a Bose–Einstein effect.
Gerson’s interests also included the study of kaons. With William Chinowsky and other collaborators, Gerson determined that the spin of the K* resonance was 1 and helped confirm SU(3) as a classification of the hadronic spectrum. In 1963 the Goldhabers joined one of us (Trilling) to form Berkeley’s Trilling–Goldhaber group, which continued for more than 25 years. Tragically, Sula died suddenly in 1965. Four years later Gerson married Judith Margoshes Golwyn, a science writer, playwright, and poet.
When the dominance of the Bevatron waned, Gerson continued bubble chamber investigations at SLAC, where he participated in the observation of ρ–ω interference and of the first anti-Ω. At Gerson’s urging, the Trilling–Goldhaber group joined forces with Berkeley colleague Chinowsky and the SLAC groups led by Burton Richter and Martin Perl to form the SLAC−LBL (Lawrence Berkeley National Laboratory) collaboration and build the Mark I detector for installation at the SPEAR electron–positron collider. The discovery of the J/ψ by the collaboration and by Samuel Ting’s group at Brookhaven National Laboratory in November 1974 was the most dramatic event in particle physics since the discovery of parity violation. While evidence mounted that the J/ψ was a resonance of a charmed quark and an anticharmed quark, a conclusive result required the discovery of actual charmed particles with the anticipated decay pattern. Gerson and François Pierre accomplished that in 1976, an achievement for which they were jointly awarded the American Physical Society’s W. K. H. Panofsky Prize in Experimental Physics in 1991.
Gerson knew the development of contemporary particle physics from his participation in many important experiments, and he conceived of a book that would introduce the subject through descriptions of the fundamental experimental discoveries. He proposed such an undertaking to the other of us (Cahn), set out the structure of the book, and identified the articles to be reprinted. Gerson’s experience and insights guided the development of the text as well. The book, The Experimental Foundations of Particle Physics, originally published in 1989, is now in its second edition.
For Gerson, physics was at once concrete, visual, beautiful, and intuitive. It was part of his intuition to know where the groundbreaking physics was, and in the 1990s it led him to cosmology. He joined a group with Richard Muller, Carl Pennypacker, and a more junior researcher, Saul Perlmutter, who were looking for supernovae. Physicists had long known that the observation of distant type Ia supernovae, including measurements of brightness and redshift, could, in principle, map the expansion history of the universe and determine how much it was being slowed by gravity. The Berkeley-led team, then headed by Perlmutter, demonstrated that significant numbers of type Ia supernovae could indeed be discovered. By 1998 the team had found 42 supernovae, and Gerson helped show that the expansion, contrary to expectations, was not slowing but accelerating, a phenomenon now ascribed to “dark energy.” That astonishing result was found independently by the competing High-z Supernova Search Team.
Gerson’s creativity never diminished. In his last five years, he and Judith produced two delightful books of poetry and art. Gerson’s watercolors illustrated Judith’s renditions in verse of Aesop’s fables and stories from Genesis. His watercolors and ink-line drawings also grace the walls of his friends’ and collaborators’ homes. They display the same joy and inventiveness that characterized his work as a scientist.
