Jack Steinberger, a giant of the field who contributed so much to the experimental development of the Standard Model, passed away on 12 December 2020 aged 99. Born in the Bavarian town of Bad Kissingen in 1921, he left Germany at the age of 13 to escape rising antisemitism and settled in the United States. After receiving a degree in chemistry from the University of Chicago, he turned his attention to physics, working at the MIT radiation laboratory through the war years before returning to Chicago to embark on a career in theoretical physics. Under the guidance of Enrico Fermi, however, he switched to the experimental side of the field, conducting mountaintop investigations into cosmic rays. This marked the beginning of his interest in neutrino physics, which would be rewarded with the 1988 Nobel Prize in Physics, shared with Melvin Schwartz and Leon Lederman, for their 1962 discovery of the muon neutrino at Brookhaven National Laboratory.
In 1968, Jack joined CERN to work on CP violation experiments. In the 1970s, he went on to become a founding member of the CERN-Dortmund-Heidelberg-Saclay (CDHS) collaboration, which was later joined by a group from Warsaw and conducted neutrino scattering experiments in the West Experimental Area. Running from 1976 to 1984, CDHS produced a string of important results using neutrino beams to probe the structure of protons and neutrons. When the Large Electron-Positron Collider (LEP) was first proposed, a core group from CDHS joined with physicists from other institutions to develop a detector for CERN’s new flagship facility. This initiative grew into the ALEPH experiment, and Jack, with his great scientific curiosity and remarkable rigour, was the natural choice to become its first spokesperson in 1980, a position he held until 1990. The detector as a whole benefited from Jack’s charismatic leadership and clarity of mind. From the outset, he stipulated that standard solutions should be adopted across the whole detector as far as possible. Jack was also insistent that all solutions considered for the detector first had to be completely understood. As the LEP era got underway, this level of discipline paid dividends and was reflected in the results.
In retirement, Jack continued to be a regular presence at CERN, contributing to the intellectual life of the Laboratory until well into his 90s, notably by returning to his interest in CP violation as an adviser to the NA31, NA48 and NA62 experiments. A full obituary will appear in the CERN Courier.