Herbert Steiner

Herbert Steiner, professor of physics emeritus at the University of California, Berkeley, and faculty senior scientist at Lawrence Berkeley National Laboratory, passed away on 15 January 2025 at the age of 97.

Herb was an accomplished experimental particle physicist with diverse interests. He was born in Göppingen, Germany, in 1927. He and his family immigrated to the US in 1938, settling in San Francisco. In 1947, he entered UC Berkeley as an undergraduate; he began his graduate studies there in 1951. In 1956, with his PhD in hand, he became a research physicist at the UC Radiation Laboratory (now the Lawrence Berkeley National Laboratory) and a lecturer in the UC Berkeley Department of Physics. In 1961, he joined the Berkeley physics faculty and, from 1992 to 1995, served as the chair of the department. In 2000, he became professor emeritus.

Under the guidance of Emilio Segrè, Herb studied the fission of heavy elements in high-energy collisions for his PhD dissertation. As a graduate student, he was recognized for his important contributions to the Chamberlain–Segrè experiment at the Bevatron that discovered the antiproton in 1955.

In the 1960s, Herb studied the intrinsic spins and parities of strange baryons. His effort provided crucial support for the eightfold way that led to the quark picture, now a basic ingredient of the standard model of particle physics. Toward the end of the decade, Herb spent his sabbatical leave at CERN, working with Georges Charpak on developing multiwire proportional chambers. This Nobel Prize–winning invention revolutionized the tracking of charged particles in astrophysics, nuclear, and particle-physics experiments. In addition, he and Owen Chamberlain launched a series of experiments with polarized targets pioneered by them. Polarization was an interest that endured with Herb for the next three decades.

In the 1970s, the group’s exploration of spin physics moved to Fermilab. In parallel, when the Bevatron began accelerating heavy ions, a new collaboration for studying heavy-ion physics grew in Berkeley. Besides Herb’s involvement, this joint venture included Shoji Nagamiya, Isao Tanihata, and their colleagues from the University of Tokyo and Osaka University.

In the early 1980s, Herb joined a small group led by Mark Strovink to carry out a search for the right-handed currents using the decay of stopped polarized muons at TRIUMF, in Vancouver, Canada. The limit on the right-handed current that they obtained remained for many years the definitive result.

In the modern era of particle physics, with the standard model firmly established, Herb was actively involved in experiments at the Stanford Linear Collider. Using the SLD detector, Herb studied the production asymmetry of the Z boson in polarized electron–positron collisions and obtained a precise measurement of the weak mixing angle, one of the fundamental parameters of the standard model.

Following the success of the deep inelastic scattering experiment at SLAC, Herb became interested in high-energy electron–proton collisions. He contributed to the publications of the H1 collaboration at the electron–proton collider HERA and was instrumental in understanding the H1 calorimeters. These instruments played an important role in the flurry of publications in the mid and late 1990s that led to the precise measurement of high-Q² events in neutral- and charged-current reactions.

After the discovery of an atmospheric neutrino deficit, Herb turned his attention to neutrino physics. By determining the rate and energy spectrum of the electron antineutrinos coming from all the Japanese nuclear reactors with the KamLAND detector, Herb and his collaborators observed neutrino oscillation using artificial antineutrino sources for the first time. This compelling finding validated the concepts of neutrino mixing and thus massive neutrinos. Herb then joined Kam-Biu Luk to work on the Daya Bay reactor neutrino experiment in China, which discovered a surprisingly large value for the smallest of the neutrino mixing angles. He played a crucial role in the installation and testing of the detectors.

From his active involvement in the discovery of the antiproton in the 1950s to the recent participation in Daya Bay, Herb always brought his unique expertise at the critical time to an experiment. Moreover, he had a profound impact on training students, postdoctoral fellows, and the junior staff on the experiments. Herb engaged with students as a true mentor and contributed to many physics discussions, often with his characteristic smile.

Herb was at Berkeley for 77 years. For his contributions to the physics department, to the “Rad Lab,” and to the broader physics community, he will be remembered for many more.

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