François Englert died on 18 June in Uccle, in the Brussels region, aged 93. Beyond his major contributions to fundamental physics, he had a profound, if discreet, influence on the Belgian scientific community.

He was born on 6 November 1932 in Etterbeek (Brussels), to a family of Jewish immigrants from Poland. During World War II, François and his older brother Marc became enfants cachés – hidden children – finding refuge in the countryside at great risk to those who sheltered them. For a child so young, it was a traumatic experience, which François long kept to himself. After the war, he enrolled at the Université Libre de Bruxelles (ULB) in the Faculty of Applied Sciences, a frequent choice at the time, as it guaranteed employment and claimed to offer the same training as a physics degree. After graduating in 1955 he switched to physics, quickly completing a licence in 1958 and a PhD, under the supervision of Jules Géhéniau, the following year.

A turning point in his career came with a postdoctoral stay at Cornell University, where Robert Brout, at first his adviser, became a lifelong colleague. He came back to ULB in 1961, as a lecturer in general physics, and Robert soon followed him. Only later, in 1980, would they formally found the Theoretical Physics group – a generic name chosen to avoid dissecting physics into separate specialities.

Open culture

From Cornell, they had brought back an informal culture: the door was always open to anyone who wanted to discuss physics. As students, we were completely immersed in the research, spending whole afternoons with the two leaders in a sort of musical-chairs brainstorming at the blackboard. They also made sure that a permanent position could be considered only after a postdoctoral stay abroad, an attitude that eventually spread to other departments, reversing a long tradition of internal recruitment.

In the early 1960s, François and Robert were looking for a way to formulate short-distance interactions in the formalism of quantum field theory (QFT). Gauge-invariant QFT was known to describe quantum electrodynamics, but dealt only with massless gauge bosons and hence long-distance interactions. The mechanism they found was submitted to Physical Review Letters in June 1964, in a paper that showed diagrammatically how gauge bosons could acquire mass. Independently, in July, Peter Higgs approached the problem focusing on the elimination of unwanted Goldstone bosons, and included the mass of the gauge bosons in a later paper.

That short paper by François and Robert was in fact remarkably complete: it included the basic spontaneous symmetry breaking by a fundamental scalar field, as is now standard, but also a dynamical approach assuming fermion condensates, and it covered the non-abelian case. The mechanism also opened the way to the proof of the renormalisability of the theory. At the time, both the strong and the weak interactions were candidates for such symmetry breaking, but a concrete realisation awaited a 1967 paper by Steven Weinberg. A different mechanism, confinement, was eventually shown to operate in strong interactions.

François and Robert soon turned their attention to cosmology, first joined by Edgard Gunzig, then by Philippe Spindel and eventually by the whole Brussels group – an exceptional case, as they had insisted that its members operate as independent individuals. One puzzle, in particular, drew them. In an expanding universe, regions thought never to have been in causal contact show almost the same temperature in the cosmic microwave background, the fossil radiation of the Big Bang. Their explanation relied on a fast initial expansion phase, a scenario they called the “causal universe”. Here, too, they were precursors. François’s curiosity extended to a wide variety of topics, with more interest in finding mechanisms than in a tedious zoology of nature. These ranged from generating the spacetime metric out of a fractal structure to the classification of monopoles and even the structure of viruses!

While François and Robert played a formative role in the Belgian physics community, François never mentioned his role in the student revolts at ULB in 1968, since the structures that emerged from them had fallen short of his hopes. In fact, he kept clear of institutional academic roles altogether. His influence was felt otherwise. Formal recognition, too, was long in coming. It began with the Gravity Research Foundation award (1978), followed by the Francqui Prize (1982), the European Physical Society Prize (1997), the Wolf Prize (2004) and the Sakurai Prize (2010). In 2013 came the Prince of Asturias Award and the Nobel Prize, awarded to François and Peter Higgs, Robert Brout having died in 2011. King Albert II made François a baron in the same year, and he was also appointed professor at Tel Aviv University.

A point of reference

It must be realised that, by the time of François’s and Robert’s seminal paper, QFT itself had fallen out of fashion. Despite its success in quantum electrodynamics, the framework could not be applied to short-distance interactions, and many preferred more holistic approaches, such as the unitary S-matrix. Interest returned progressively as spontaneous symmetry breaking gained acceptance, a shift that can be followed in the paper’s own citation curve, and François and Robert embarked on an inter-university series of lectures and seminars. Despite the philosophical and linguistic differences between the universities, this seeded or cemented the contacts between the theoretical physics groups of Brussels, Leuven and Louvain-la-Neuve. The effort made them a point of reference for Belgian physics.

Interestingly, this path had been trodden before them by Monsignor Georges Lemaître, father of the Big Bang, who visited ULB frequently. To celebrate these unifying efforts, the Belgian Senate, later joined by the Brussels Region, encouraged the formation of the Brout–Englert–Lemaître (BEL) Centre, common to ULB, the Vrije Universiteit Brussel (VUB), the Université Catholique de Louvain (UCLouvain) and the Katholieke Universiteit Leuven (KU Leuven).

Guenakh Mitselmakher, an experimental high-energy physicist of international stature, passed away on 28 January at the age of 80. He was born on 5 December 1945 in Vilnius, Lithuania. After graduating from Moscow State University in 1968, Guenakh started his professional career at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. He often recalled that his mentor Bruno Pontecorvo made the largest impact on his scientific vision and “physics taste”.

For his PhD, he joined a collaboration of four that was designing an experiment to search for the charged-lepton flavour violating decay μ → 3e. The result, published in 1976, improved on the best previous limit by two orders of magnitude. Next, he took part in the first measurement of the charged-pion radius at the Serpukhov accelerator, published in 1974. He then proposed and co-led an experiment that yielded the first measurements of the pion’s polarisability and the γ → 3π coupling in 1983 and 1986, respectively. In the mid-1980s, he and his group joined the DELPHI experiment at LEP. Guenakh co-led the construction of the DELPHI hadron calorimeter and made critical contributions to the measurement of the number of light neutrinos coupling to the Z boson. To this end, he co-initiated the collaboration of theorists and experimentalists that developed the analysis framework later known as ZFITTER.

Guenakh moved to the US in 1991, to join the Superconducting Super Collider (SSC) laboratory in Texas. After the closure of the SSC, in 1993, and having worked briefly at Fermilab, he joined the University of Florida (UF) physics department in 1995. There, he spearheaded a vigorous experimental hadron-collider programme, building a group that at its peak counted seven faculty and more than 40 members, including students, postdocs and engineers. Together they made major contributions to the CDF experiment at Fermilab and to the CMS experiment at CERN, where Guenakh led the design and construction of the endcap muon system.

In both experiments, the UF group held leading roles in the physics programme, most notably in the Higgs-boson discovery in 2012, in precision measurements of the new particle’s properties, and in many searches for new physics. Among them, the recent search for the charged-lepton flavour violating decay τ → 3μ echoes Guenakh’s research from the early years of his career. He was also the driving force behind UF joining the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 1996, where the group contributed prominently to the design and construction of the apparatus and to data analysis. Indeed, the first gravitational-wave event, in 2015, was initially identified by coherent WaveBurst, a real-time analysis algorithm conceived in a 2008 paper that Guenakh co-authored.

Guenakh Mitselmakher was a relentless advocate for the pursuit of physics of pivotal significance. His scientific legacy will persist through the many scientists he mentored during his career.

It is with great sadness that we learned George Kalmus passed away on 27 May, at the age of 91. George had a long and distinguished career in particle physics, which took him from the early days of bubble chambers to the LHC and beyond.

Born in Beočin, Yugoslavia, on 21 April 1935, George moved to London with his family in 1939. He obtained his physics degrees at University College London (UCL), gaining his PhD in 1959 with the pioneering study “Physical properties of bubble chambers”. As a research assistant at UCL, he was responsible for the design and specification of the magnet for the British Heavy Liquid Bubble Chamber. He also studied semileptonic decays of Λ hyperons with UCL colleagues and a group at the Lawrence Radiation Laboratory in Berkeley, later the Lawrence Berkeley Laboratory (LBL), using their 30-inch heavy liquid chamber.

From 1962 to 1967, apart from one year back at UCL, he worked at LBL as a research assistant, studying semileptonic Λ decays and all aspects of K⁺ meson decays, especially the rare semileptonic four-body K⁺_e4 channel. He became a tenured senior physicist at LBL in 1967, switching to the study of hadron resonances using K^– and π⁺ beams.

In 1972, George returned to Europe to lead the bubble-chamber group at the Rutherford Appleton Laboratory (RAL). His large group participated in various collaborations, with George himself proposing and working on K^–p and K⁰_Lp experiments in the 2 m hydrogen bubble chamber at CERN.

Following the discovery of open charm in 1976, he proposed and led a major experiment to investigate direct electron production by hadrons using a track-sensitive target in the Big European Bubble Chamber at CERN. He subsequently led a collaboration at the SLAC Hybrid Facility, where he instigated the addition of a high-resolution camera. This was crucial to the successful measurement, in 1982, of the decays of D mesons produced by 20 GeV photons in the 1 m hydrogen bubble chamber. His exploitation of bubble chambers and work on kaon and charm physics contributed to his election as fellow of the Royal Society in 1988.

George went on to establish the UK collaboration working on DELPHI at CERN’s LEP collider, where he applied his formidable expertise to all aspects of the experiment: design, realisation and analysis. He led RAL’s involvement in the construction of the superconducting solenoid – at the time the largest in the world – and pushed for the addition of a silicon microvertex detector, one of the first at LEP. He was elected deputy spokesman for DELPHI and chaired its collaboration board from 1986 to 1993.

George was director of RAL’s Particle Physics Department from 1986 to 1997, with wide-ranging responsibilities for the whole of the UK’s particle-physics programme, latterly including the preparation of the LHC experiments. He was appointed to CERN’s Scientific Policy Committee from 1990 to 1997 – a time that saw the approval of the LHC – and chaired it from 1999 to 2001.

In 1998 George returned to his earlier interest in ultra-rare kaon decays by joining the NA48 experiment at CERN. He retired from RAL in 2000, but not from physics, joining the ZEPLIN-III experiment to search for dark matter in the Boulby Underground Laboratory in Yorkshire, UK.

George had a special combination of scientific ability, integrity and human skills, all greatly appreciated by those who knew and worked with him. He helped many careers and led UK particle physics with a sure hand through sometimes tempestuous waters for more than a decade. We owe him a great deal. He was survived by his brother, Peter, professor at Queen Mary University of London, his three daughters and his grandchildren. Our deepest sympathy goes to the whole family.

• We are very saddened to have learned that Peter Kalmus passed away on 2 August. A full obituary will appear in a later edition of CERN Courier.

To the shock of family, colleagues and friends, Norman McCubbin died suddenly at his home in Oxford on 22 June. His long and distinguished career included vital roles in UK particle physics and at CERN.

Norman was born in north London on 27 June 1948, the eldest of three sons. His family later left Leicester for Kenya, where Norman attended Kenton College in Nairobi. He then boarded at the prestigious Repton School in Derbyshire, to which he jokingly ascribed his success in winning ballot tickets to England test cricket matches. He attended New College, University of Oxford, achieving a first-class honours degree and a doctorate. His thesis contained an analysis of K^–p interactions in the CERN 2 m bubble chamber.

Norman moved to CERN as a Lancaster postdoc, working on the CHLM experiment at the Intersecting Storage Rings. After joining the Rutherford Appleton Laboratory (RAL) as a postdoc in 1976, he moved to the British–French–Scandinavian collaboration on the Wide-Angle Spectrometer and then the Axial Field Spectrometer, where he worked on the world’s first uranium compensating calorimeter. After getting tenure at RAL, Norman joined the HELIOS fixed-target heavy-ion experiment, of which he became spokesperson.

He was involved in the early stages of the ZEUS experiment at DESY, becoming leader of the RAL ZEUS group in 1990, and managed a large group of capable technical staff and research associates who worked on the construction and commissioning of the central tracking detector. Norman also played an important role in developing the experiment’s software and held senior positions, including simulation coordinator. He remained closely involved throughout ZEUS’s running.

As ZEUS matured, he began to work on ATLAS, again leading the development of the software. He was computing coordinator from 1999 to 2003, steering the decision on computing language with typically consummate tact. His advice was greatly valued by successive ATLAS spokespersons, who gave him numerous important responsibilities, including chairing the committee that in 2007 recommended task-sharing algorithms and criteria for ATLAS membership, authorship and financial contributions. He was assiduous in employing his exceptional command of English to correct and polish ATLAS papers, and maintained his keen interest in heavy ions as an expert within ATLAS.

Norman was a leader of UK particle physics, becoming first division leader and, from 2007, director of RAL’s Particle Physics Department, while gaining the admiration and respect of all who worked with him. After officially retiring from RAL in 2012, Norman continued to contribute to ATLAS and taught physics to undergraduates at St Anne’s College, Oxford. He inspired many generations of students and was an extremely popular tutor, relishing the core subjects of thermodynamics, statistical mechanics, relativity and symmetries.

Norman McCubbin was a Renaissance man, learned but never pedantic, broad in interests and expertise. He loved cricket and golf, music and current affairs. He was an exceptional physicist, publishing both cutting-edge particle-physics papers and articles on the history of physics. He will be greatly missed by his family and his many colleagues and friends.

• A fund has been set up in Norman’s memory to endow an annual prize for the best physics student at the college at which he taught, St. Anne’s Oxford.