Arthur M (Art) Poskanzer, distinguished senior scientist emeritus at Lawrence Berkeley National Laboratory (LBNL), passed away peacefully on 30 June 2021, two days after his 90th birthday. Art had a distinguished career in nuclear physics and chemistry. He made important discoveries of the properties of unstable nuclei and was a pioneer in the study of nuclear collisions at very high energies.
Born in New York City, Art received his degree in physics and chemistry from Harvard in 1953, an MA from Columbia in 1954, and a PhD in Chemistry from MIT in 1957 under Charles D Coryell. He spent the first part of his career studying the properties of nuclei far from stability produced in high-energy proton collisions. After graduating from MIT, he joined Gerhard Friedlander’s group at Brookhaven National Laboratory (BNL), which was using the Cosmotron to produce beta-delayed proton emitters and neutron-rich light nuclei. In 1966 he moved to the Lawrence Radiation Laboratory (now LBNL) and continued to study nuclei far from stability at the Bevatron in collaboration with Earl Hyde, Joe Cerny and others. He also began his long connection to research in Europe as a Guggenheim fellow at Orsay in 1970–1971, during which he worked with Robert Klapisch’s group on a ground-breaking experiment at the CERN Proton Synchrotron measuring the masses of sodium isotopes.
Soon after Art’s return to Berkeley, beams from the SuperHILAC were injected into the Bevatron, creating the Bevalac, the world’s first high-energy nuclear accelerator. Together with Hans Gutbrod he led the Plastic Ball Project. Analysis of its data in 1984 by Art and Hans Georg Ritter identified directed flow, the first definitive demonstration of the collective behaviour of nuclear matter in nuclear collisions. In 1986 the experiment was moved to CERN and the collaboration with GSI continued with a series of experiments at the Super Proton Synchrotron. During these years, Art made two more extended visits to CERN as a Senior Alexander von Humbold Fellow: first in 1986–1987 working on the WA80 experiment, and then in 1995–1996 on NA49.
From 1990 to 1995 Art was the founding head of LBNL’s relativistic nuclear collisions programme, bringing together local groups to plan an experiment at the Relativistic Heavy Ion Collider (RHIC) under construction at BNL. This resulted in the proposal for STAR, one of the two large multi-purpose RHIC detectors. Art stepped down as programme head in 1995 and returned to research, authoring a seminal paper with Sergey Voloshin on methods for flow analysis and leading the measurement of elliptic flow by STAR. After his retirement in 2002, he remained active for a further decade, leading the successful search for higher order flow components at STAR, and enthusiastically mentoring many postdocs and young scientists.
Art was a well-known and well-loved member of the heavy-ion community. For his work on nuclei far from stability, he was awarded the Nuclear Chemistry Prize of the American Chemical Society in 1980. For the discovery of collective flow, he was awarded the Tom Bonner Prize of the American Physical Society in 2008. This rare “double” is a lasting tribute to his half-century career at the frontiers of nuclear science.