Wolfgang (Pief) Panofsky, one of the outstanding contributors to the remarkable progress in the field of particle physics, passed away on 24 September, aged 88.

Pief's family emigrated from Germany to the US in 1934 to escape the Nazi regime, which came to power in 1933. His father, Erwin Panofsky, a world-renowned art historian who had previously served in the US as visiting professor, had accepted a professorship at Princeton University. Pief, then 15, never entered US high school, but immediately went to the university, where he graduated with a Bachelor's degree in 1938. In a spirit of adventure, and attracted by a letter from Robert Millikan, he went on to Caltech and worked on his PhD in the X-ray laboratory of Jesse DuMond, who had been impressed with his know-how in electronics. Pief also taught, and, together with Carl Anderson, even wrote a textbook on electricity and optics. In 1942 he obtained his PhD with DuMond and also married his mentor's daughter Adele. By this time the US was at war, and Pief worked on various military projects, one on the detection and localization of targets, another, in collaboration with Los Alamos, on the measurement of the yield of a nuclear explosion. He observed "Trinity", the first nuclear explosion, from a B-29 bomber at a distance of 3 km.

After the war, Pief went to Berkeley at the invitation of Luis Alvarez, and collaborated with him in the design of proton linear accelerators. He also participated in some very interesting experiments. In 1947 the π-meson was discovered, and Berkeley, with Ernest Lawrence's 340 MeV proton synchrocyclotron and the 300 MeV electron synchrotron invented by Edwin McMillan, was the only laboratory in the world in which these interesting particles could be produced. I had the privilege of collaborating with Pief in one of the experiments with pions, the first observation of the decay of the π0 into two gamma rays. The π0 had been anticipated for theoretical reasons, and clear indications of gamma rays that could be attributed to its decay had been observed, but this experiment demonstrated the existence of the particle and also permitted a measurement of its mass, which is close to that of its charged partner. Another, very beautiful experiment showed that when negative pions are captured in hydrogen, about half of the time (this "half" was called the "Panofsky ratio") π0-mesons are produced. This permitted a more accurate measurement of the π0 mass, and turned out to be a very useful means of producing π0-mesons in future studies of their properties. During this period Pief also taught, and together with Melba Phillips, wrote a widely used textbook on classical electrodynamics.

In 1951, the Regents of the University of California required of its faculties that they sign the politically repressive "non-communist oath". Pief signed it although he disapproved of it, but then left Berkeley to join the physics faculty of Stanford University, across the San Francisco Bay. W W Hansen had started an electron linear accelerator project at Stanford some years previously and the "Mark III" had begun to work. Unfortunately, Hansen had died prematurely, and in 1949, with the help of his experience in linear accelerator design, Pief was able to inject new life into a somewhat faltering programme. Together with Edward Ginzton he took over the direction of the project. By 1953, Mark III was 70 m long, with an energy of 400 MeV, and it served Robert Hofstadter in the very important first measurements of the nucleon form factors.

In 1956, Panofsky and Ginzton began to develop plans for Project M – M for monster – a two-mile electron linear accelerator, with 30 times the energy of Mark III. Because of its size, the project required federal funding by the Atomic Energy Commission (AEC), and Pief was instrumental not only in getting AEC support, but also in getting it to agree that, contrary to its policies at other national laboratories, it would not require any security clearances at the new laboratory. He also needed to convince the Stanford faculty that physicists from other laboratories would be equally welcome. In 1961 agreement and approval for the construction of the Stanford Linear Accelerator Centre, SLAC, had been reached and Panofsky became its director. In the meantime Ginzton had left to become director of the microwave development company, Varian Associates. Ground for SLAC was "broken" in 1962, and the first full-length beams were achieved in 1966. The qualities of Pief's leadership in this very large and successful effort were universally admired and acknowledged: his patience and energy, his ability to resolve conflict constructively, and his creative contributions to both the accelerator design and experimental physics questions.

Pief remained director of SLAC until 1983, and the laboratory's contributions to progress in particle physics in these 23 years were truly remarkable. He led in the conception and design of the spectrometers of the deep inelastic-scattering experiments of Jerome Friedman, Henry Kendall and Richard Taylor, which in 1968–69 discovered the composite nature of the nucleons, that is, they are made of "partons", later shown to be the quarks and gluons of the Standard Model. In 1973 the newly built SPEAR electron–positron storage ring at SLAC discovered the charm quark as the constituent of the Ψ resonance, called the J by Sam Ting et al., who saw the resonance simultaneously at Brookhaven Laboratory. A few months later, in the same SPEAR data, Martin Perl discovered the τ, and hence the existence of a third family of particles. Analysing the shapes of the hadronic events in SPEAR, Gail Hanson discovered the jet nature of the hadronic materialization of the partons. In 1989, SLAC anticipated the more powerful LEP collider at CERN. With collisions of electrons and positrons accelerated in the two-mile linac, it was the first to see the shape of the Z resonance, and so catch a glimpse of the number of neutrino families. These remarkable successes all profited very much from Pief's technical vision and his ability to foster productive collaboration in the experimental teams.

Pief was also motivated by a deep consciousness of the responsibility of the scientist to society, as well as concern about the danger posed by the arsenals of nuclear weapons. He served over many years as advisor to the US government. He was member of the Scientific Policy Committees in the Eisenhower, Kennedy, Johnson and Carter administrations, and contributed to the achievement of two very important US–USSR nuclear weapons treaties: the atmospheric test-ban treaty of 1963 as well as the antiballistic missile treaty of 1972. He also served as consultant to the Defence Department in the context of the Jason group of scientists. In 1970, Pief and Sidney Drell founded the Stanford Center for International Security and Arms Control, and for several years Pief served as chair of the Committee on International Security and Arms Control of the National Academy of Science.

In summary, Pief made beautiful experimental contributions to our understanding of particles, was instrumental in the conception and leadership of highly successful laboratories in this field, and gave much of his energy and wisdom to help our society to try to rid itself of the menace of nuclear weapons. His list of awards, prizes and degrees is the longest ever. Thank you for what you have done in one lifetime, Pief.

Jack Steinberger, CERN.