Subject Grouping: Praxis

Former CERN director Horst Wenninger, who played key roles in the approval of the LHC and in establishing knowledge transfer at CERN, passed away on 16 July. Horst was universally trusted and his advice was sought regularly by colleagues. He knew his way around CERN like no one else, and knew whom to contact to get things done (and, crucially, how to get them to do it). Before becoming a physicist, Horst had considered becoming a diplomat. Somehow, he managed to combine the two professions, all in the interest of CERN. He cultivated the art of connecting scientists, engineers and administrators – always with the aim of achieving a clear goal.

Born in Wilhelmshaven, Germany in 1938, the third child of a naval officer, Horst earned his PhD in nuclear physics from Heidelberg University in 1966. Two years later he joined CERN to participate in the Big European Bubble Chamber (BEBC). From the outset Horst was inspired by CERN. Early on he saw the importance of the Laboratory for establishing peaceful worldwide collaboration and relished participating in the adventure.

He was soon identified as a leader, first as physics coordinator for the BEBC in 1974. In 1980 he went to DESY to work on electron–positron collider physics in preparation for LEP, returning to CERN in 1982 to lead the BEBC group. In 1984 he became head of the experimental facilities division, providing support for Omega, UA1 and UA2. For the R&D and construction of the LEP detectors Horst needed to implement a new style of collaboration: for the first time, major parts of the detectors had to be financed, developed and provided by outside groups with central CERN coordination. In 1990 he became leader of the accelerator technologies division, and in 1993 he was appointed LHC deputy project leader, where his profound knowledge of CERN was vital for the reassessment of the LHC project.

The wider community also benefited immensely from his contributions in advisory roles throughout his active life

Horst’s five-year term as CERN research and technical director began in 1994 – the year LHC approval was expected. The day before the crucial vote by the CERN Council in December of that year, the German delegation was still not authorised to vote in support of the project. In a latenight action Horst managed to arrange contact with the office of the German chancellor, with the mission to sway the minister responsible for the CERN decision. His cryptic reaction was conveniently interpreted by the supportive German delegate as a green light, a determined move for the good of CERN. Horst was later awarded the Order of Merit (First Class) of the German Republic.

In 2000 Horst helped launch the CERN technology transfer division and chaired the technology advisory board. Also, thanks largely to his drive, the 2017 book Technology Meets Research – 60 Years of CERN Technology: Selected Highlights was published. Horst retired from CERN in 2003, but continued to make major contributions. He was asked to provide guidance for the FAIR project at GSI Darmstadt, where he was instrumental in arranging the involvement of CERN accelerator experts and later steered the complex and delicate organisation of major international “in-kind” contributions. When, in 2019 the EU approved the “South-East European International Institute for Sustainable Technologies” (SEEIIST), Horst was appointed to coordinate the projects first phase.

Horst left his mark on CERN. The wider community also benefited immensely from his contributions in advisory roles throughout his active life. We have lost an outstanding colleague and a good friend from whose enthusiasm, advice and wisdom we all benefited tremendously.

Leading member of the UK particle-physics community, Paul Murphy, passed away on 26 August. Paul was a keen and brilliant physicist who was head of the particle-physics group at the University of Manchester from 1965 until his retirement in 1990. He started his PhD as a Fulbright Scholar theoretician in Fermi’s group in Chicago, but later discovered that his real talent lay in experimentation. Styling himself as a “gas and glue” man, Paul was one of the few physicists at the time who could design and make spark chambers that worked.

He then went to Liverpool to work on the 400 MeV cyclotron before joining the Rutherford Laboratory and going to UC Berkeley to study hyperons at the 6 GeV Bevatron. On returning in the early 1960s, he and John Thresher carried out a series of experiments to determine the spin-parity of pion-nucleon resonances, for which they were awarded the Rutherford medal and prize by the UK Institute of Physics.

Aged only 34, Paul moved to Manchester to become a professor, heading up the newly formed high-energy physics group. As well as leading the group into two experiments at the new electron synchrotron, NINA, at the Daresbury Laboratory, he spearheaded the development of particle detectors at Manchester and built the group’s strong reputation in this area. First were the wire spark chambers with digital instead of photographic readout, a version of which was then used in the CERN, Holland, Lancaster, Manchester (CHLM) experiment that concentrated on proton–proton diffraction scattering at the CERN ISR facility. Paul then led the group developing (quieter) large-area drift chambers that were used to detect muons, first at the JADE experiment at DESY, which helped to discover the gluon, and then at LEP’s OPAL experiment at CERN. His sharp physics mind led him to be a pioneer at the start of each new accelerator facility, for instance realising the potential for NINA to produce a useable beam of neutral kaons.

Paul was a firm believer in making the most of wherever he found himself. He played a major role in national and international particle physics, chairing and contributing to many strategic decision-making bodies. He was also an engaging educator at all levels, often livening up his lectures with many anecdotes.

Paul was a passionate humanitarian and loved people; he wanted to show everyone he met that he valued them, for example, by learning how to welcome them in their own language. His insight into people and physics alike was extraordinary, and his penchant for making a little friendly mischief never far from the surface.

Max Samuilovich Zolotorev, a pioneer of experimental studies of atomic parity violation, passed away on 1 April in his home in Oregon, US.

Max was born in Petrovsk, a small town not far from the Russian city of Saratov, where his mother found herself evacuated from the advancing German army. Upon graduating from secondary school, despite showing unusual talent and ability from an early age, he was not admitted to an institute or even a vocational school because he was Jewish. After eventually securing a position with the Novosibirsk Electro Technical Institute in Siberia, where he demonstrated outstanding academic performance, he was able to transfer to the newly founded Novosibirsk State University. He graduated in 1966, before obtaining his first and second doctoral degrees in 1974 and 1979 at the Institute of Nuclear Physics in Novosibirsk Academgorodok.

Max started out by working on measurements of the hyperon magnetic moments. However, in the early 1970s he was drawn into studying fundamental physics using the methods of atomic, molecular and optical physics. Together with his mentor and colleague Lev Barkov, he was the first to discover parity violation in atoms by observing optical rotation of the plane of polarisation of light propagating through a bismuth vapour.

The 1978 measurement came at a crucial time in the development of the Standard Model. While observations of high-energy neutrino scattering on nuclei at CERN in 1973 provided evidence of neutral weak currents, there was no evidence that the neutral weak current violated parity as predicted by the Glashow–Weinberg–Salam (GWS) model. Furthermore, earlier atomic parity violation experiments had produced null results, in contradiction with theoretical predictions. The observation of parity violation in bismuth, followed later by measurements of parity violating electron scattering at SLAC, was crucial evidence that the GWS model was indeed the correct description of the weak interaction.

Max Zolotorev was an inspiring mentor and teacher who always set the highest expectations for his students

Max and his colleagues also established the foundation for some of today’s most sensitive magnetometers with their measurements in the late 1980s of nonlinear Faraday rotation, clearly identifying the crucial role of quantum coherences. In 1989 Max emigrated to the US and took up a research position at SLAC, later moving to Lawrence Berkeley National Laboratory, where he worked until his retirement in 2018. At SLAC, Max and colleagues proposed using lasers to cool hadrons in colliders as a variation on van der Meer’s stochastic cooling method. The “optical stochastic cooling” concept will soon be tested at Fermilab by a group led by a former student of Max’s. Another of his co-inventions is the so-called “slicing method” to produce ultrashort pulses of X-rays essential for time-resolved studies of the properties of condensed matter.

Max Zolotorev was an inspiring mentor and teacher who always set the highest expectations for his students. His ability to find “weak spots” in one’s scientific logic was legendary. One of Max’s great insights was that, as physicists, we should never design our experiments around what was sitting in our labs or in our heads. Instead, we should choose deep and important problems, think hard about them and develop the cleverest way to approach them that we can, learn new subjects, build new apparatus, and push our boundaries and limits. Max’s work exemplified the curiosity, creativity and rigour of physics at its best.