• Siegmund Brandt 1936–2016 • James Cronin 1931–2016 • Erwin Gabathuler 1933–2016 • Werner Kienzle 1936–2016 • Stanley Mandelstam 1928–2016

Siegmund Brandt 1936–2016

Siegmund Brandt was born on 17 July 1936 in Berlin and studied physics at Bonn University in Germany. In his diploma work, which was carried out under the supervision of Wolfgang Paul, he constructed a small bubble chamber for experiments at the Bonn 500 MeV electron synchrotron. As early as 1961, Brandt worked at CERN on bubble-chamber physics studying pion–proton interactions, which became the topic of his PhD thesis.

After his habilitation in 1966, he became associate professor at Heidelberg University, and in 1972 he became professor, founding senator of physics and vice rector at the newly founded University of Siegen. At Siegen, Brandt’s interest turned to electronic detectors and he worked at DESY on the PLUTO experiment at DORIS and PETRA. He contributed to the three-jet analysis with the “triplicity” method, which led to the discovery of gluons in 1979. After PLUTO, Brandt continued with the PETRA experiments by joining TASSO. During this time, Brandt was also member of the Scientific Council of DESY, which he chaired from 1990 to 1993, and he was later elected to the Polish Academy of Arts and Sciences.

Brandt left DESY for CERN in the late 1980s, where he joined the ALEPH experiment at LEP and contributed to the ALEPH forward detectors and the analysis of Bhabha scattering and jet production. Brandt was an extremely creative author – his books include Data Analysis: Statistical and Computational Methods for Scientists and Engineers (1975) and The Harvest of a Century: Discoveries of Modern Physics (2013). He is also well known by many students as one of the authors of the general-physics textbook series he wrote with his theory colleague Hans Dieter Dahmen.

Brandt was a versatile physicist. His work spanned the operation of now-historic detectors such as bubble chambers and the construction and analysis of modern electronic high-resolution instruments, and his successes will live on in his books on basic science. Brandt passed away peacefully in Munich on 28 August after a long period of illness, leaving behind his son and his grandchildren. He will be dearly missed by his friends and colleagues.

• Hans Dieter Dahmen, Claus Grupen and Thomas Mannel, Siegen University.

James Cronin 1931–2016

Jim Cronin, who shared the 1980 Nobel Prize in Physics with Val Fitch for the discovery of CP violation, died on 25 August 2016. He was a brilliant experimentalist and data analyst who had remarkable careers in both particle and cosmic-ray physics.

Jim was a man of extraordinary drive. Born in Chicago, he was raised in Dallas where his father was a classics professor. In 1953 he moved to Brookhaven and then Princeton, where he honed the spark-chamber technique before returning to the University of Chicago in 1971. He was appointed to head the colliding-beams division at Fermilab in 1977, but he soon resigned: a largely administrative role was not for him. In 1982, while on leave at CERN, he led a small team to make the best direct measurement of the lifetime of the π0.

In 1986, to the surprise of many, Jim turned to cosmic rays and started to discuss his design for an air-shower array that could search for PeV gamma rays from the binary source Cygnus X-3. His visit to Leeds, UK, in November 1986 led to a lasting friendship, and in 1991 we embarked on an effort to build a collaboration and raise money to construct an instrument of unprecedented size to study cosmic rays with energies up to 1020 eV. Thirteen years later, the Pierre Auger Observatory, which covers 3000 km2 of Western Argentina, began data-taking, and continues to do so with a team of more than 400 scientists from 16 countries.

The route to this achievement was strewn with difficulties, which were largely overcome through Jim’s formidable drive and his discrete and modest use of his status. He obtained $100,000 from UNESCO to bring scientists from developing countries to Fermilab for a six-month-long design study, won support for us to tour the Far East to raise interest, and prised $1 million from the University of Chicago to build a new centre at the site. Evaluation of our plans by an international body proved impossible, so Jim invited a panel of experts, including CERN’s Jack Steinberger, to assess us. Their report helped to raise $50 million, although one agency commented “Of course it is a favourable report: you chose the committee.”

The success of the Auger project has greatly enhanced the profile of fundamental physics in Argentina, Brazil, Mexico and Vietnam, while the host town of Malargüe is home to the James Cronin School. Despite the large size of the collaboration, Jim stimulated young people while carrying out key analyses alone using FORTRAN 77 and “TopDrawer” – an ancient graphics package hosted on a dedicated Chicago computer.

Jim will be sorely missed by all who knew him. Without his strong sense of direction and his persuasive skills, the Pierre Auger Observatory and many other projects would never have succeeded. He is survived by his second wife, Carol, and by a daughter, a son and six grandchildren. His first wife, Annette, and an older daughter pre-deceased him.

• Alan Watson, University of Leeds, UK.

Erwin Gabathuler 1933–2016

Erwin Gabathuler, a highly respected experimental physicist and former CERN research director, passed away on 29 August 2016. Gabathuler was born in 1933 in Maghera, Northern Ireland, the son of the manager of an embroidery factory. He graduated in physics from Queen’s University Belfast in 1956 and was awarded his PhD from the University of Glasgow in 1961. After a postdoc at Cornell University he returned to the UK in 1964 to work on the NINA electron synchrotron at the Daresbury Laboratory, where, among a number of experiments, he made a pivotal measurement of “ρ–ω interference” in wide-angle electron–positron pair production.

In 1974, Gabathuler moved to CERN and led the European Muon collaboration, which was aimed at understanding the quark structure of nucleons and nuclei. He became head of the CERN experimental division in 1978 and CERN research director in 1981, guiding CERN’s programme in the years leading to the discovery of the W and Z bosons.

In 1983, Gabathuler was appointed to a chair at the University of Liverpool and to the position of head of the particle-physics group, taking charge of the leadership of the group’s programme as it entered the collider era. He initiated major Liverpool involvement in the H1 and HERMES experiments at the HERA electron–proton collider at DESY, while also nurturing Liverpool’s contribution to the DELPHI experiment at LEP. At the same time, his interest in the role of fundamental symmetries in physics led him to also conceive and establish CERN’s unique CPLEAR experiment to study kaon decay. While continuing his interest in deeply inelastic lepton–hadron physics with colleagues on H1, and following the completion of CPLEAR, Gabathuler took Liverpool into the BaBar experiment at SLAC, California.

His appointment to Liverpool led Gabathuler to have a substantial influence on the development of high-energy physics in the UK, at a time when the then UK government was considering possible withdrawal from CERN. His commitment contributed greatly to the success of his colleagues in physics and in other fields. He helped to secure funding for the Liverpool Surface Science Centre, and initiated new undergraduate courses with the Astrophysics Research Institute at Liverpool John Moores University.

In 1990, Gabathuler was elected to the fellowship of the Royal Society. He was also a fellow of the UK Institute of Physics, received the institute’s Rutherford Medal and Prize in 1992, and was awarded the Order of the British Empire in 2001 for services to physics. He received two honorary doctorates in science, and during his emeritus years continued to contribute as a member of national and international scientific advisory committees.

As a colleague in Liverpool, he was widely admired and respected. He was a friend and mentor who exhibited unswerving support and concern for his colleagues’ individual well-being and career advancement, while demanding in return delivery of physics of the very highest standard.

• John Dainton and Themis Bowcock, University of Liverpool.

Werner Kienzle 1936–2016

Experimental particle-physicist Werner Kienzle was born in Wiernsheim, a small town in Baden-Württemberg close to Stuttgart. His childhood was profoundly marked by the war and the death of his father on the German eastern front. Despite life after the war being difficult for his family, he was very successful in his academic studies and earned a fellowship at the University of Göttingen, where he did his PhD in solid-state physics.

Werner joined CERN in 1964 as a postdoc fellow and he remained at the Organization for his entire career. Concerned and eager for peace in the tense context of the Cold War, he was deeply involved in collaboration with Russian colleagues and participated in experiments in Serpukhov from 1968 to 1972. Back at CERN, his work concentrated on searching for evidence of the presence of quarks in hadrons. He was among the main initiators of the NA3 experiment at the Super Proton Synchrotron (SPS), which allowed measurements of the structure functions of pions. The results indicated a cross-section about twice as high as anticipated, corresponding to QCD high-order corrections, and this enhancement was named the “K” factor by the collaboration, as recognition of Werner’s contribution.

Werner was appointed SPS co-ordinator at the beginning of the 1980s and participated in the discovery of the W and Z bosons. In parallel, he became involved in new outreach programmes: in particular, he was promoter of the Microcosm in 1988 and editor of the Hadrons for Health reference booklet in 1996. While reaching his retirement age, Werner participated in the development of the total cross-section measurement set-ups that initiated the TOTEM experiment at the LHC.

Werner was a fantastic and enthusiastic storyteller, an adventurer and an innovator. His wife, Maria, and his sons, Francesco and Marco, can be proud of everything he did for CERN.

• His colleagues and friends.

Stanley Mandelstam 1928–2016

The great theoretician Stanley Mandelstam passed away in June, aged 87. He was born in Johannesburg, South Africa, from a Jewish family originating in Latvia, and studied in the UK under doctoral adviser Richard Dalitz. He became a professor at the University of Birmingham in 1960, then at the University of California at Berkeley in 1963.

His initial reputation came from his 1958 proposal of what is called the Mandelstam representation, which implies that the scattering amplitude is the boundary value of an analytic function in a 2D domain in which the only singularities are cuts. Some people could say, now that we have the Standard Model of particle physics, that all this was useless. This is not the case historically, however, since it supported the idea that interesting results could be obtained from the combination of analyticity and unitarity.

The main example is the “Froissart Bound” obtained in 1961, which says that the cross-section cannot increase faster than the square of the logarithm of the energy. In 1966, a proof of the Froissart bound was obtained without the Mandelstam representation. Around that time, V N Gribov also used the Mandelstam representation to predict that the scattering amplitude does not behave as was expected at high energies. It is also clear that the Veneziano amplitude, which was proposed in 1968 and led to dual models in which particles interact via “strings”, was inspired by the Mandelstam representation. The surprise was that theoreticians proposed that particles themselves be strings or superstrings. It is precisely in this domain that Mandelstam made further fundamental contributions.

It’s not possible to list all of his papers here, but let me single out his proof that N = 4 supersymmetry is finite, an important result for which he sought absolutely no publicity. Mandelstam was a fellow of the Royal Society and of the American Academy of Arts and Sciences. He received the Dirac Medal in1991 and the Dannie Heineman Prize in 1992. Testimonies from students say that he was an excellent lecturer, including in undergraduate courses. Stanley Mandelstam was an affable person and incredibly modest. We shall miss him.

• André Martin, CERN.