Joachim Heintze 1926–2012

Joachim Heintze, emeritus professor of physics at the University of Heidelberg and eminent particle physicist, passed away unexpectedly on 31 March at the age of 85. An outstanding scientist and inspiring teacher, he made a lasting impact on particle physics.

Born in Berlin on 20 July 1926, Heintze began to study electrical engineering immediately after the Second World War, but soon switched to study physics in Berlin and Göttingen, where his interest in particle physics and in building experiments began. In 1951 he followed his teacher, Otto Haxel, to Heidelberg where he finished his PhD thesis in 1953. Shortly after the discovery of parity violation in weak interactions, in 1957, he conceived of and performed an extremely elegant experiment showing that electrons emitted in beta decay are polarized, providing another proof of parity violation.

In 1959 Heintze moved to CERN, where the recently completed Synchrocyclotron and Proton Synchrotron offered exciting opportunities for research in the emerging field of particle physics. After studying muon scattering on carbon to understand possible differences between muons and electrons, he focused on studies of the weak interaction, starting with the challenging experiment of pion beta decay (with a 10–8 branching ratio), which showed the conservation of vector currents.

In November 1964 he returned to Heidelberg as professor and director of the institute of physics, where he began establishing particle physics as one of the main research fields. For the next few years, he and his group continued experiments at CERN, studying key properties of weak interactions in hyperon beta decays and rare decays of K mesons. Around 1972 he became increasingly interested in electron–positron physics, as a result of an observed excess in hadron production at the Frascati laboratory. He therefore shifted his research to the DORIS storage ring under construction at DESY, where he initiated one of the first experiments – a nonmagnetic detector consisting of cylindrical drift chambers surrounded by a sodium-iodide and lead-glass calorimeter – which was ready in time to measure properties of the recently discovered J/ψ meson and τ lepton.

Inspired by the construction of PETRA, Heintze joined forces with other teams from Germany, Japan and the UK to build the JADE experiment. His team took on the responsibility for designing and building the central tracking detector, based on a new concept of the drift chamber, the so-called jet chamber. JADE was one of the experiments that provided clear experimental evidence for the existence of gluons, by observing three-jet and four-jet events, as well as a wealth of other results. Later Heintze considered JADE to be the best and most interesting experiment of his career. With the plans for the Large Electron–Positron collider taking shape at CERN, he and many other colleagues from JADE became a nucleus for the OPAL experiment there, building on all of the know-how gained at PETRA.

Heintze was a truly gifted and imaginative experimental physicist. When coming to Heidelberg, he put emphasis on establishing and continuously improving a modern technical infrastructure. This was of vital importance for a field in which he excelled – detector development – where he was motivated by new questions in physics and the challenge to make them accessible through novel detectors. In this respect, the concept of multiwire drift chambers, proposed by his student Albert Heinrich Walenta, became a new standard for modern tracking detectors. Based on this concept, Heintze and his group developed and built powerful detector systems for precision measurements of particle tracks. The first experiment in which these chambers were used was performed in 1972 at CERN to study rare K-decays. At electron–positron colliders, Heintze and Walenta pioneered cylindrical drift chambers, which later, in the form of jet chambers, became a core element of the JADE and OPAL experiments and a model for many other tracking detectors at colliders.

Heintze shaped physics at Heidelberg in a major way. As dean of the physics department in the early 1970s he had the foresight to initiate a chair in environmental physics, the first of its kind at a German university. He developed a new concept for teaching physics to first-year science students, which included modern developments in physics. His lectures were full of original insights and demonstrated his love for and deep understanding of physics. These insights were to be published as a textbook, which unfortunately he was not able to finalize completely.

As a teacher he shared his enthusiasm with his students, inspiring them and teaching them the essence of physics and the skills of an experimenter. It is no surprise that a number of them later became leaders in the field of particle physics. Working as his research student was not only inspiring but also highly demanding, as no idea or result remained unchallenged until proven correct.

His scientific achievements were honoured by two major distinctions: the Physikpreis of the German Physical Society in 1963 and the Max-Born Prize of the German Physical Society and the UK Institute of Physics in 1992.

Joachim Heintze was motivated and inspired by a deep love for physics, and was open to new insights while remaining critical and not inclined to reach hasty conclusions. Scientific truth was essential for him. Late in life, severe personal losses led him to start playing the cello, which he loved and played with friends. He was a great personality, an unconventional scientist and an enthusiastic teacher. Nobody could escape his spell. His friends and colleagues will always remember him thankfully and with great admiration.

Volker Soergel, University of Heidelberg, and Albrecht Wagner, DESY.

Dieter Möhl 1936–2012

Dieter Möhl, an accelerator physicist of world renown who made essential contributions to many projects both at CERN and elsewhere, passed away on 24 May. His theoretical work was unique in terms of the understanding, improvement and extension of beam-cooling techniques to many accelerators and storage rings. At CERN his name will be tied forever to the success from the beginning of the antiproton programme, but he also made substantial contributions to the project for the upcoming Facility for Antiproton and Ion Research (FAIR) in Germany and to many storage rings where beam cooling was an essential ingredient.

Dieter was one of the pioneers at CERN who demonstrated with the Initial Cooling Experiment (ICE) that stochastic cooling was a viable proposition. This was essential for the approval of CERN’s antiproton programme and its subsequent success. He then became a leading member of the team that initiated and designed the Low Energy Antiproton Ring (LEAR) where the first ultraslow beam extraction to the experiments, extending for hours, was performed. Following the decision to stop LEAR, he actively participated in the study and design of a simplified antiproton source, which later became the Antiproton Decelerator ring (AD), after the SUPERLEAR project – of which he was one of the prominent promoters – was not approved. In 1982 he initiated the concept of the Extra-Low ENergy Antiproton ring (ELENA) at the AD and was extremely happy to see that this project to provide antiprotons with a kinetic energy as low as 100 keV was finally approved in 2011.

In addition, Dieter made important contributions to electron cooling. A token of this work is found in the AD and in the modification of the LEAR machine to become the Low Energy Ion Ring (LEIR), which acts as a buffer and accumulation ring between the fast-cycling ion linac, Linac 3, and the slow-cycling Proton Synchrotron. LEIR is an essential element in the LHC’s ion injector chain.

Dieter was not only a renowned accelerator physicist. He also played an important role in human rights issues, in particular as a founding father of the Orlov Committee, which was created at CERN to provide efficient help to Soviet dissidents in the 1970s and 1980s.

Although he retired in 2001, he was at work nearly every day to help with our projects and give us advice. Even the day before his untimely death he was at CERN to discuss the ELENA project with us. He was one of the kindest and gentlest people we have ever known, with an infinite patience and a proverbial generosity. We gratefully remember Dieter’s human quality and miss his wise counsel.

His friends and colleagues.

Hans Henrik Andersen 1937–2012

Hans Henrik Andersen, physicist and founder of Nuclear Instruments and Methods in Physics Research B, passed away on 3 November.

Born in Frederiksberg, Denmark, Hans Henrik qualified in engineering at the Technical University of Copenhagen, before gaining a PhD from the University of Aarhus in 1972. He then worked at the Risø research centre and Aarhus University and as visiting professor at IBM Research, Yorktown Heights, and Fudan University, Shanghai. In 1982 he became a professor in experimental solid-state physics at the Niels Bohr Institute. He was professor emeritus from 2004 and was often at the institute.

Hans Henrik made important contributions to atomic and solid-state physics, especially in the field of the stopping power of matter for fast charged particles, where the accuracy of his measurements remains unsurpassed. His results were achieved by measuring the amount of heat deposited in foils at the temperature of liquid helium (4 K). Together with collaborators, he succeeded in showing that the stopping power for fast α particles is more than four times larger than for protons. This showed that the stopping power is not exactly proportional to the square of the atomic number, Z, as the simple Bethe formula predicts, and provided additional proof of the existence of the Barkas effect. His scientific career ended with participation from 1986 onwards in the ASACUSA experiment at CERN, where he compared the scattering of protons with that of antiprotons at the Antiproton Decelerator.

In addition to his scientific work, Hans Henrik was a member of many committees, for example in the Danish Physical Society. He was a member of the board of the Natural Science Faculty at Aarhus University, later becoming dean there, and of the board of the university itself. After moving to Copenhagen, he became a board member of the Natural Science Faculty of Copenhagen and for a few years he was on the board of the Niels Bohr Institute.

Hans Henrik held many positions in the administration of science in Denmark. He was chair of the Danish Natural Science Research Council and later a member of the Planning Commission for Research. He was also a council delegate at CERN in 1985 and the Danish member of the Scientific Council of the EU Research Centre in the years 1985–1987. In addition, he was the founder, and subsequently co-editor, of Nuclear Instruments and Methods in Physics Research B, an activity he followed until the end.

Always kind and interested in what we were doing in high-energy physics, Hans Henrik participated in many of our meetings. He had a profound knowledge of experimental physics and often asked precise, much appreciated questions about particle physics. He is missed by all of us and by his family for whom he was a much loved husband, father and grandfather.

His friends and colleagues in high-energy physics.