Roger Anthoine 1925–2015

Roger Anthoine, who was involved with public relations at CERN for more than 25 years, passed away on 26 October. The first editor of the CERN Courier, he had celebrated his 90th birthday in March (CERN Courier April 2015 p41).

A graduate in engineering and journalism, Roger came to CERN from the electrical industry in May 1959. He was hired to start a "house publication" for the laboratory, a role that placed him in the Public Information Office (PIO), which dealt with all of the laboratory’s public-relations activities under the direct supervision of the Director-General. In mid-August, the first issue of the publication appeared in two editions – English and French – under the unifying name Roger had proposed: CERN Courier/Courrier CERN (CERN Courier July/August 2009 p30).

In 1960, following the sudden death of John MacCabe, Roger became head of the PIO, a position that he was to hold until he retired in 1986, dealing with the whole gamut of CERN’s public relations – from press releases and relations with journalists to the organisation of visits, including those of important dignitaries. It was within these operations that he introduced the concept of in-house guides to explain the organisation to visitors, at the time mostly on Saturdays. His years as head of the PIO were studded with numerous highlights including, as he was later to recall, the comic strips about CERN’s deeds published by La Tribune de Genève in the 1970s, the naming of CERN streets, the preservation of Roman vestiges and large "erratic" stones unearthed on the site, the organisation’s first films and, last but not least, the coining of the words "Cernois/Cernite". With his new responsibilities, Roger had to pass the CERN Courier on to others, and in 1965 he oversaw the birth of CERN’s Weekly Bulletin for the internal audience, allowing the Courier to become more clearly focussed on news in particle physics for the international scientific community.

After retirement, Roger reverted to his first love, aviation, and he remained active for many years in technical writing. A pilot since 1944, he wrote numerous articles and books on the subject in French and English, and often acted as consultant on historical events connected with aviation. Most recently, one book in particular – Aviateurs-Piétons vers la Suisse 1940-1945 (Editions Sécavia) – led to interviews with Radio Télévision Suisse for its "Living History" series, broadcast, sadly, only after Roger’s death.

During his time with the PIO, Roger had developed good contacts with members of CERN Council, management and staff. Often seen at CERN until his last days, he was particularly proud, decades after retirement, to be still addressed by name by former CERN colleagues of all walks of life. No doubt they will continue to notice his presence around the site – and in the continuing legacy of the Courier and Bulletin. He is survived by his daughter, France, and son Didier.

• His friends at CERN. This text takes inspiration from an obituary that Roger – ever the professional – prepared himself some years before he died.

Marcel Froissart 1934–2015

With great sadness, we announce the death of theoretical physicist Marcel Froissart on 21 October, at the age of 81.

Marcel was extremely bright. As a teenager, he won the "concours général", a competition for high-schools students in France. He went on to study at Ecole Polythecnique and Ecole des Mines. I first met him in 1956 when, with Jacques Mandelbrojt, he wrote the notes of the lectures given by Chen Ning Yang in Paris on parity violation. This showed his incredible scientific precocity – he was just 22. Until he became professor at Collège de France in 1974, he was mostly in Saclay, interspersed with periods at CERN, Berkeley and Princeton.

At CERN, he collaborated with Vladimir Glaser and Wolfgang Pauli, trying to make sense of Heisenberg’s non-linear theory and ending up with the conclusion that this was impossible. Back at Saclay, he became interested in the proof of Mandelstam’s representation for Yukawa-like potentials. I remember he thought that the proof I proposed with John Bowcock was not rigorous (he was right, although the issues could be fixed). His major contribution then was the discovery, with Raymond Stora (also recently deceased, CERN Courier November 2015 p40) of the way a polarised beam can be depolarised in an accelerator. This work is still being used by accelerator engineers worldwide.

Froissart’s greatest period was when he was at Berkeley, where Goeff Chew was preaching the S-matrix theory, as opposed to field theory. In this atmosphere, Froissart tried to produce a non-trivial result, and he succeeded marvellously. At the "La jolla" conference in 1961, he presented what is now known as the "Froissart bound" – that total cross-sections cannot increase faster than the square of the logarithm of the energy. The proof was based on a non-trivial combination of unitarity and analyticity. For analyticity, Froissart used the postulate of Mandelstam representation. I was present and, for me, it was a real turning point in my life. Previously, I had been working mostly on potential scattering, but after that I decided to work on high-energy behaviour of scattering amplitudes. In 1966, I succeeded to prove the Froissart bound without the postulate of Mandelstam representation, and Froissart presented my results very fairly at the 1966 Berkeley conference. It must be said that the "Froissart bound" seems to be qualitatively saturated experimentally. The first indications came from the ISR, and they were confirmed by the SppS collider and now by the LHC (we are anxiously awaiting the results of the experiments at 13 TeV).

Back at Saclay, Froissart collaborated with Lascoux and Photiadi on attempts to prove Mandelstam representation in perturbation; he also worked on improving numerical programmes because he was impressed by Daniel Bessis’s attempts to use Padé approximants to calculate scattering amplitudes. He also spent two years at Princeton, where his great critical sense made Sam Treiman call him "Mr Guillotine". At that point, he decided to leave theoretical physics. His experience in computing turned out to be very useful in 1972 when he became head of Saclay’s bubble-chamber group, where big simulations were needed. In 1973, he was ready to accept a chair at Collège de France, where he inherited the directorship of the laboratories of Louis Leprince-Ringuet and Francis Perrin. He retired in 2004.

Marcel Froissart was certainly an excellent laboratory director, but he was above all a great theoretician, to whom, personally, I owe a lot, as I’ve explained. Besides being a great scientist, Marcel Froissart was a charming person. We shall miss him.

• André Martin.

Vadim Kuzmin 1937–2015

Vadim Alekseevich Kuzmin, a prominent Russian theoretician, passed away on 17 September at the age of 78. He will be remembered for groundbreaking contributions to particle physics, cosmic-ray physics, neutrino physics and cosmology.

Vadim Kuzmin was born in Moscow on 16 April 1937. Finishing school in 1955, he began his physics studies at the Moscow State University the same year. He obtained his PhD in physics in 1964 in the Lebedev Physical Institute, where he was employed from 1961 after graduating from the university. From 1971, he worked in the Theory Division of the Institute for Nuclear Research (INR), Moscow. In 2000, he was elected to the Russian Academy of Sciences.

Vadim is possibly best known for the Greisen–Zatsepin–Kuzmin effect. In 1966, he and Georgiy Zatsepin and, independently, Kenneth Greisen, predicted that the spectrum of cosmic rays should be suppressed at the highest energies as a result of scattering off the cosmic microwave background. Observation of this cut-off would imply that the highest-energy cosmic rays originate in the nearby universe, opening up the experimental search for sources, while the absence of the cut-off would signify new physics. Studies of the GZK effect went on to determine the direction of research in cosmic-ray physics for decades, and while the GZK suppression has since been observed, the identification of powerful cosmic accelerators is still a priority in astroparticle physics.

Less well known is that Vadim suggested the gallium–germanium method for detecting solar neutrinos – an ambitious idea that was successfully implemented by the SAGE and GALLEX collaborations. The results played a key role in proving that the solar neutrino puzzle cannot be solved by modifications of the solar model, and pointed instead to the real culprit: neutrino oscillations.

Vadim also made many fundamental contributions to the cosmology of the early universe. In pioneering papers, independently of Andrei Sakharov but at about the same time, he realised that the baryon asymmetry of the universe could be explained by particle physics. He also proposed that the necessary baryon-number non-conservation could be observed in laboratory experiments on neutron–antineutron oscillations. One of his best-known papers, written with Valery Rubakov and Mikhail Shaposhnikov, later pointed out that the necessary condition for baryogenesis – rapid-baryon-number non-conservation – is already satisfied in the Standard Model of elementary particles and does not require any new hypothetical interactions.

In recent years, Vadim worked on the cosmological puzzles of dark matter and dark energy. He suggested that dark matter and baryon asymmetry can appear together, in one process, therefore explaining the balance of dark and visible matter in the universe. Together with Rubakov and Igor Tkachev, he introduced superheavy dark matter, which opens the window to trans-Planckian physics and has deep connections to the inflationary birth of the universe.

Vadim had great sense of humour – his friends loved being victims of his innocent spoofs. He was fond of camping and trout fishing at the lakes of Karelia, and mushroom hunting in the forests near Moscow. He was a spirited painter, and many of his friends possess his artworks, preserving memories of Vadim as he was at the time. Our thoughts go to his family and friends, and the many others who shared important parts of their professional lives with Vadim.

• His friends and colleagues.

Lev Okun 1929–2015

Lev Borisovich Okun passed away on 23 November.

His death is a great loss to the global particle-physics community and to Russian science. Okun was one of the world’s distinguished theoretical physicists, and a person with genuine passion and drive for science.

He was inseparably linked with the Institute of Theoretical and Experimental Physics (ITEP) where he arrived as a postgraduate student in 1954 and worked there until his last day. He was head of the Theoretical Physics Laboratory at ITEP for 30 years, and also professor at the Moscow Institute for Physics and Technology for many years.

Okun was a student of Pomeranchuk (who was a student of Lev Landau), and Landau once said about him: "He is my grandson."

Okun’s contribution to particle physics is remarkable. In the field of strong interactions, the famous Okun–Pomeranchuk theorem on the equality of cross-sections for scattering particles from the same isomultiplet at asymptotically high energies was proved in 1956. A year later, he proposed a composite model, known as the Sakata–Okun model, in which hadrons (the term that Okun had coined) were constructed from "pre-particles", the predecessors of quarks. Within this model, he predicted the new η and ηf mesons, which were discovered several years later.

The physics of weak interactions was his favourite subject. His early paper written in collaboration with Ioffe and Rudik in 1957 observed that the P-parity violation in beta decay also means a violation of the C parity. He was the first to understand the important role of CP symmetry in the decays of neutral K mesons, and suggested an experiment to look for CP violation.

Okun also conceived a new field of research at the intersection of particle physics, cosmology and astrophysics. The first paper in this field was written by Lev Borisovich (in collaboration with Zel’dovich and Pikel’ner) in 1965. They developed a method for calculating the relic abundance of elementary particles during the expansion of the universe. They performed a calculation of free-quark concentration. Non-observation of free quarks was one of the arguments for quark confinement. The approach that emerged from this paper now plays a crucial role in searches for solutions to the origin of dark matter in the universe. In 1964, in a paper written together with Pomeranchuk and Kobzarev, the idea of a "mirror world" came into existence. "Mirror matter" is still a possible candidate for dark matter. Vacuum-domain walls investigated by Okun in 1974 were the first macroscopic objects of QFT that could determine the evolution of the universe. In the same year, Okun, Voloshin and Kobzarev published a pioneering paper on the decay of the false vacuum – a subject that unexpectedly became relevant to the physical vacuum in our universe after the discovery of the Higgs boson with 125 GeV mass.

Okun had an extraordinary pedagogical talent. Due to his deep understanding of physics, he had the unique ability to put even the most intricate theoretical constructions in simple terms. Many generations of physicists studied particle physics with his textbooks Weak Interactions of Elementary Particles (1963) and Leptons and Quarks (1980, 1990).

He was absolutely devoted to physics and embodied the quest for truth that is at the heart of physics. He attracted young talent and was a founder of one of the world’s great schools of particle physics.

Okun was the first Soviet physicist elected to the Scientific Policy Committee of CERN. He was awarded prestigious international prizes.

He was an extraordinary person of outstanding integrity, a friend of great warmth and a source of deep knowledge and wisdom. He will be remembered by his family, friends and colleagues.

• His friends and colleagues.