Jobs – Page 80 of 527

BASE breaks new ground in matter–antimatter tests

The BASE collaboration at the CERN Antiproton Decelerator (AD) has made the most precise comparison yet between the properties of matter and antimatter. Reporting in Nature in January, following a 1.5 year-long measurement campaign, the collaboration finds the charge-to-mass ratios of protons and antiprotons to be identical within an experimental uncertainty of just 16 parts per trillion. The result is four times more precise than the previous BASE comparison in 2015 and places strong constraints on possible violations of CPT invariance in the Standard Model.

The charge-to-mass ratio is now the most precisely measured property of the antiproton
Stefan Ulmer

Invariance under the simultaneous operations of charge conjugation, parity transformation and time reversal is a pillar of quantum field theories such as the Standard Model. Direct, high-precision tests of CPT invariance are therefore powerful probes of new physics, and of the possible mechanisms through which the universe came to be matter-dominated.

“The charge-to-mass ratio is now the most precisely measured property of the antiproton,” says BASE spokesperson Stefan Ulmer of RIKEN in Japan. “To reach this precision, we made considerable upgrades to the experiment and carried out the measurements when the antimatter factory was closed down, so that they would not be affected by disturbances from the experiment’s magnetic field.” The upgrades include a rigorous re-design of the cryostage of the experiment and the development of a multi-layer shielding-coil system, which considerably reduced magnetic-field fluctuations in the central measurement trap, explains Ulmer. “Another important ingredient is the implementation of a superconducting image-current detection system with tunable resonance frequency and ultra-high non-destructive detection efficiency, which eliminates the dominant systematic shift of the previous charge-to-mass ratio comparison.”

The BASE team confined antiprotons and negatively charged hydrogen ions in a state-of-the-art Penning trap, in which charged particles follow a cyclical trajectory with a frequency that scales with the trap’s magnetic-field strength and the particle’s charge-to-mass ratio.

By alternately feeding antiprotons and hydrogen ions one at a time into the trap, the team was able to measure their cyclotron frequencies under the same conditions. Performed over four campaigns between December 2017 and May 2019, the measurements involved more than 24,000 cyclotron-frequency comparisons, each lasting 260 seconds. Within the experimental uncertainty, the result, –(q/m)_p/(q/m)_p̄= 1.000000000003(16), demonstrates that the Standard Model respects CPT invariance at an energy scale of 1.96×10^–27 GeV at 68% confidence. It also improves knowledge of 10 coefficients in the Standard Model extension – a generalised, observer-independent effective field theory used for investigations of Lorentz violation.

Weak equivalence principle

The BASE team also used their data to test the weak equivalence principle, which states that different bodies in the same gravitational field undergo the same acceleration. Any difference between the gravitational interaction of protons and antiprotons, for example due to anomalous gravitational scalar or tensor couplings to antimatter, would result in a difference in the proton and antiproton cyclotron frequencies. Sampling the varying gravitational field of Earth as it orbits the Sun, BASE found no such difference, constraining the strength of anomalous antimatter/gravitational interactions to less than 1.8×10^–7 and enabling the first differential test of the weak equivalence principle (WEP) using antiprotons.

“From this interpretation we constrain the differential matter–antimatter WEP-violating coefficient to less than 0.03, which is comparable to the initial precision goals of other AD experiments that aim to drop antihydrogen in the Earth’s gravitational field,” explains Ulmer. “BASE did not directly drop antimatter, but our measurement of the influence of gravity on a baryonic antimatter particle is, according to our understanding, conceptually very similar, indicating no anomalous interaction between antimatter and gravity at the achieved level of uncertainty.”

The collaboration expects to reach even higher sensitivities on both the WEP test and the proton–antiproton charge-to- mass ratio comparison by increasing the experiment’s magnetic-field strength, stability and homogeneity. Further improvements are anticipated from the use of transportable antiproton traps, such as BASE-STEP, which allow precision antiproton experiments to be moved from the fluctuating accelerator environment to a calm laboratory space.

Have you got what it takes to teach?

**LHC lessons** A 2017 ICTP Physics Without Frontiers event saw students analyse LHC data via the CEVALE2VE project, one of several ways teachers can inspire students with the world of research. Credit: A Sanchez/ICTP

Particle physicists are no strangers to outreach, be it giving public talks, writing popular books or taking part in science shows. But how many are brave enough to enter a career in teaching, arguably the most important science-communication activity of all? CERN alumni who have returned to the classroom reveal teaching to be one of the hardest but most rewarding things they have ever done.

“I love my job,” exclaims Octavio Dominguez, who completed his PhD in 2013 studying the appearance of electron-cloud build-up in the LHC before deciding to switch to teaching. Having personally benefitted from some excellent teachers who sparked an “unquenchable curiosity”, he says, the idea of being a teacher had been on his mind ever since he was at secondary school. “The profession is definitely not exempt of challenges. Well, in fact I can say it’s the most difficult thing I’ve ever done… But if I keep doing it, it’s because the feedback from students is absolutely priceless. It’s truly amazing seeing my students evolve into the best version of themselves.”

Job satisfaction

Despite giving as many as 25 lessons per week, including presentations and practicals, and spending long hours outside school preparing materials and marking assignments, happiness and personal satisfaction are cited as the main rewards of working as a teacher. “I particularly enjoy seeing the enthusiasm in students’ eyes – it is something that cannot be explained with words,” says Eleni Ntomari, who was a summer student at CERN in 2006, then a PhD student and postdoc working on the CMS experiment. “From the outside, teaching might not appear difficult, but in reality it is not just a profession but a ‘project’ with no timetable and a continuation of trying to learn new things in order to become more efficient and helpful for your students.” Ntomari took advantage of every teaching opportunity that academic life offered, from being a lab instructor, becoming a CERN guide and giving talks at local schools when a teaching opportunity in Greece arose during her postdoctoral fellowship at DESY. “I realised teaching was highly gratifying, so I decided to continue my career as a physics teacher in secondary and high schools.”

I particularly enjoy seeing the enthusiasm in students’ eyes
Eleni Ntomari

Teachers of STEM subjects are in acute demand. In the US, physics has the most severe teacher shortage followed by mathematics and chemistry, with large surpluses of biology and earth-science teachers, according to the Cornell physics teacher education coalition. Furthermore, around two thirds of US high-school physics teachers do not have a degree in physics or physics education. The picture is similar in Europe, with a brief teacher survey carried out by the European Physical Society in 2020 revealing the overwhelming opinion that a serious problem exists: 81% of respondents believed there is a shortage of specialist teachers in their country, of which 87% thought that physics is being taught by non-specialists.

Initiatives such as the UN International Day of Education on 24 January help to bring visibility and recognition to the profession, says Dominguez: “Education is one of the principal means to change the world for the better, but I feel that the teaching profession is frequently disregarded by many people in our society,” he says. “I’ve spent most of my career as a teacher in schools in deprived areas of the UK, and now I’m doing my second year in one of the most affluent schools in the country. This has given me a new perspective on society and has helped me understand better why some behaviour patterns appear.”

The CERN effect

The fascinating machines and thought-provoking concepts underpinning particle physics make a research background at CERN a major bonus in the classroom, explains Alexandra Galloni, a CERN summer student in 1995 who completed her PhD at the DELPHI experiment in 1998, spent a decade in IT consultancy, and is now head of science and technology at one of the UK’s top-performing secondary schools. “I milked my PhD as much as I could – I promised a visit from Brian Cox to my first school at interview, and although I didn’t pull that one off, contacts at CERN have enriched life both at school and on many of the CERN trips I inevitably ended up running. The Liverpool LHCb team have hosted incredible ‘Particle Schools’ at CERN for students and staff from many schools almost every year since then, leading to gushing feedback from all involved.”

I love the variety, the unexpected moments and the human interaction in the classroom
Alexandra Sheridan

Keeping in touch with events at CERN has also led to exciting moments for the students, she adds, such as watching the Higgs-discovery announcement in 2012, applying for Beamline for Schools in 2014, taking part in the ATLAS Open Data project and participating in Zoom calls with CERN contacts about future colliders and antimatter. “The surrounding tasks to teaching can be gruelling, and I would be lying if I said I didn’t resent the never-ending to-do list and lack of being able to plan much personal time during term-time. But I love the variety, the unexpected moments and the human interaction in the classroom.”

CERN offers many professional-development programmes for teachers to keep up-to-date with developments in particle physics and related areas, as well as dedicated experiment sessions at “S’Cool LAB”, the coordination of the highly popular Beamline for Schools competition and internships for high-school students. These efforts are also underpinned by an education-research programme that has seen five PhD theses produced during the past five years as well as 67 published articles since the programme began in 2009. “We are reaching out to all our member states and beyond to enthuse the next generations of STEM professionals and contribute to their science education,” says Sascha Schmeling, who leads the CERN teacher and student programmes. “Engaging the public with fundamental research is a vital part of CERN’s mission.”

LHC Run 3: the final countdown

LHC run 3 starts — **All systems go** Commissioning the Linac4 beam on 8 February. Credit: CERN-PHOTO-202202-028-1

The successful restart of Linac4 on 9 February marked the start of the final countdown to LHC Run 3. Inaugurated in May 2017 after two decades of design and construction, Linac4 was connected to the next link in the accelerator chain, the Proton Synchrotron Booster (PSB), in 2019 at the beginning of Long Shutdown 2 and operated for physics last year. The 86 m-long accelerator now replaces the long-serving Linac2 as the source of all proton beams for CERN experiments.

On 14 February, H^–ions accelerated to 160 MeV in Linac4 were sent to the PSB, with beam commissioning and physics to start in ISOLDE on 7 and 28 March. Beams will be sent to the PS on 28 February, to serve, after set-up, experiments in the East Area, the Antiproton Decelerator and n_TOF. The SPS will be commissioned with beam during the week beginning 7 March, after which beams will be supplied to the AWAKE facility and to the North Area experiments, where physics operations are due to begin on 25 April.

Meanwhile, preparations for some of the protons’ final destination, the LHC, are under way. Powering tests and magnet training in the last of the LHC’s eight sectors are scheduled to start in the week of 28 February and to last for four weeks, after which the TI12 and TI18 transfer tunnels and the LHC experiments will be closed and machine checkout will begin. LHC beam commissioning with 450 GeV protons is scheduled to start on 11 April, with collisions at 450 GeV per beam expected around 10 May. Stable beams with collisions at 6.8 TeV per beam and nominal bunch population are scheduled for 15 June. An intensity ramp-up will follow, producing collisions with 1200 bunches per beam in the week beginning 18 July on the way to over double this number of bunches. High-energy proton-proton operations will continue for 3–4 months, before the start of a month-long run with heavy ions on 14 November. All dates are subject to change as the teams grapple with LHC operations at higher luminosities and energies than those during Run 2, following significant upgrade and consolidation work completed during LS2.

Among the highlights of Run 3 are the first runs of the neutrino experiments FASERν and SND@LHC

Among the highlights of Run 3 are the first runs of the neutrino experiments FASERν and SND@LHC, as well as the greater integrated luminosities and physics capabilities resulting from upgrades of the four main LHC experiments. A special request was made by LHCb for a SMOG2 proton-helium run in 2023 to measure the antiproton production rate and thus improve understanding of the cosmic antiproton excess reported by AMS-02. Ion runs with oxygen, including proton-oxygen and oxygen-oxygen, will commence in 2023 or 2024. The former is also long-awaited by the cosmic-ray community, to help improve models of high-energy air showers, while high-energy oxygen-oxygen collisions allow studies of the emergence of collective effects in small systems. High β* runs to maximise the interaction rate will be available for the forward experiments TOTEM and LHCf in late 2022 and early 2023.

On 28 January, CERN announced a change to the LHC schedule to allow necessary work for the High-Luminosity LHC (HL-LHC) both in the machine and in the ATLAS and CMS experiments. The new schedule foresees Long Shutdown 3 to start in 2026, one year later than in the previous schedule, and to last for three instead of 2.5 years. “Although the HL-LHC upgrade is not yet completed, a gradual intensity increase from 1.2 × 10¹¹ to 1.8 × 10¹¹ protons per bunch is foreseen for 2023,” says Rende Steerenberg, head of the operations group. “This promises exciting times and a huge amount of data for the experiments.”

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Standing up for sustainability

Logo of the International Year of Basic Sciences for Sustainable Development 2022. Credit: IYBSSD.

The COVID-19 pandemic has cost more than five million lives and disrupted countless more. Without the results of decades of curiosity-driven research, however, the situation would have been much worse. The pandemic therefore serves as a stark and brutal reminder of the links between basic science and the balanced, sustainable and inclusive development of our planet.

The International Year of Basic Sciences for Sustainable Development (IYBSSD), proclaimed by the United Nations (UN) general assembly on 2 December 2021, is a key moment of mobilisation to convince economic and political leaders, as well as the public, of the critical links between basic research and the 2030 Agenda for Sustainable Development adopted by all UN member states in 2015. Due to their evidence-based nature, universality and openness, basic sciences not only contribute to expanding knowledge and improving societal welfare, but also help to reduce societal inequality, improve inclusion and foster intercultural dialogue and peace. They are thus central in achieving the UN Agenda’s 17 Sustainable Development Goals.

Virtuous circle

Many examples of basic sciences’ transformative contribution to society are so widespread that they are taken for granted. The web was born at CERN from the needs of global particle physics; general relativity underpins the global positioning system; search engines and artificial intelligence rely on brilliant mathematics and statistical methods; mobile phones derive from the discovery of transistors; and Wi-Fi from developments in astronomy. The discovery of DNA, positron emission tomography, magnetic resonance imaging and radiotherapy have transformed medical diagnostics and treatments, while advances in basic physics, chemistry and materials science are reducing pollution and revolutionising the generation and storage of renewable energy.

Basic science, together with applied scientific research and technological applications, is thus one of the key elements of the virtuous circle that allows the sustainable development of society. Yet, basic sciences are often not as prominent as they should be in discussions concerning societal, environmental and economic development. The aims of the IYBSSD are to focus global attention on the enabling role of basic science and to improve the collaboration between basic sciences and policy-making.

Particle physics has a major role to play in making the IYBSSD a success

The IYBSSD, led by the International Union of Pure and Applied Physics – which will celebrate its centenary in 2022 – has received strong support from around 30 international science unions and organisations active in physics, mathematics, chemistry, life science and social science, along with 70 national and international academies of sciences, and 30 Nobel laureates and Fields medallists. A series of specific activities coordinated at local, national and international levels will aim to promote inclusive collaboration (with special attention paid to gender balance), enhance basic-science training and education, and encourage the full implementation of open-access publishing and open data in the basic sciences.

The IYBSSD inauguration ceremony will take place at UNESCO on 8 July, and a closing ceremony is planned to take place at CERN in 2023, hopefully timed with the completion of the Science Gateway building. Events of all sorts proposed by countries, territories, scientific unions, organisations and academies endorsed by the steering committee will occur throughout the year.

The role of particle physics

As one of the most basic sciences of all, particle physics has a major role in making the IYBSSD a success. The high-energy physics community should use all the available opportunities in 2022 and 2023, be it through conferences, workshops, collaboration meetings or other activities, to place our field under the auspices of the IYBSSD. We need to show how this community advances science for the benefit of society, how much it re-enchants our world and therefore makes it worth sustaining, how much it contributes in its practice to openness, equity, diversity and inclusion, and to multicultural dialogue and peace. The CERN model is emblematic of these contributions. Many of the programmes of the CERN & Society foundation also promote these values in line with the IYBSSD objectives.

The need for humanity to maintain and develop high levels of interest and participation in basic sciences makes awareness-raising initiatives such as the IYBSSD critical. Following the recent international years of physics, chemistry, mathematics and astronomy, it is now time for us to get behind this unprecedented, global interdisciplinary initiative

Luciano Girardello 1937–2022

Luciano_Girardello_2022 — Luciano was interested in all aspects of fundamental physics, from quantum field theory to gravity. Credit: Family photograph

Italian theoretical physicist Luciano Girardello passed away in January, aged 84. He made important contributions to quantum field theory, supersymmetry and supergravity, and will always be remembered by friends and colleagues for his irony, vision and great humanity.

Born on 10 September 1937, Luciano graduated at the University of Milano. After a first postdoctoral fellowship at Boulder, Colorado, he worked at many institutions across the world, including Harvard University, the École normale supérieure in Paris and CERN. Upon his return to Italy, he became professor at the University of Milano, where he spent several years, and in 2000 he moved to the new University of Milano-Bicocca, contributing to the creation of its physics department, where he remained for the rest of his career.

Luciano was one of the first to study the mechanisms of supersymmetry breaking, rooting the theory in reality

Luciano was interested in all aspects of fundamental physics, from quantum field theory to gravity, and made seminal contributions to the foundations of supersymmetry and supergravity in their early days. In a fruitful collaboration with other pioneers of the subjects, including Eugène Cremmer, Sergio Ferrara and Antoine Van Proeyen, he investigated the coupling of matter in supergravity, which is fundamental for the experimental search for supersymmetry, the modern theory of gravitation and the effective theories of string compactifications. Luciano was one of the first to study the mechanisms of supersymmetry breaking, rooting the theory in reality. In the final part of his career, he applied the AdS/CFT correspondence, or gauge/gravity duality, to the understanding of fundamental problems in quantum field theory. He was not interested in theoretical speculations or mathematical tricks but rather in understanding the nature of things and in the cross-fertilisation of fields and ideas. Many of his contributions to physics were born in the corridors of the CERN theory division, in long days and endless nights spent with friends and collaborators.

Luciano’s wide and original lectures on different topics at the universities of Milano and Milano-Bicocca inspired students for more than 30 years. His deep thoughts, vision and culture also informed and educated many generations of talented young physicists who are now active in the international arena. Greatly admired as a physicist, he will be remembered by those who had the good fortune to know him well as a great human being, a cultivated and refined person, and an old-time gentleman.

Patricia McBride elected next CMS spokesperson

patty-mcbride-08-0297-11D — Patricia McBride. Credit: Fermilab

Patricia McBride, distinguished scientist at Fermilab, has been elected as the next spokesperson of the CMS collaboration. She will take over from current spokesperson Luca Malgeri in the autumn, becoming the first woman to lead the 3000-strong collaboration.

McBride graduated in physics at Carnegie Mellon University, and completed a PhD at Yale analysing charm decays at Fermilab’s E630 experiment. After a postdoc at Harvard working on the Crystal Ball experiment at DESY and the L3 experiment at CERN, she joined Fermilab in 1994, later becoming head of its scientific computing programmes and head of the Particle Physics Division. Since joining CMS in 2005, she has served as deputy head of CMS Computing, head of the CMS Center at Fermilab and as US CMS Operations programme manager. She was deputy CMS spokesperson from 2018 to 2020.

It will be a challenging, but exciting time for the collaboration
Patricia McBride

Among other appointments, McBride was chair of the American Physical Society (APS) Division of Particles and Fields, the US Liaison Committee of the International Union of Pure and Applied Physics (IUPAP) and the IUPAP Commission for Particles and Fields. In 2009 she was elected as an APS fellow for her original contributions to flavour physics at LEP and the Tevatron, and for the development of major new initiatives in B physics and collider physics.

McBride’s love for particle physics started at the end of middle school when her mother gave her a book about particle accelerators. She will take up the leadership of CMS soon after LHC Run 3 gets under way, and is therefore looking forward to exciting times ahead: “CMS is looking forward to the Run-3 physics programme and at the same time will be pushing to keep the detector upgrades for the HL-LHC on track,” she says. “It will be a challenging, but exciting time for the collaboration.”

David Saxon 1945–2022

Experimental particle physicist David Saxon passed away on 23 January. A native of Stockport, south of Manchester, where his father was a parish minister, he attended the University of Oxford and obtained his doctorate measuring pion–nucleon scattering at the Rutherford Laboratory, followed by a short postdoc there. His doctoral research took him to Paris and Berkeley, where in both cases he reported that his arrival was marked by the onset of student riots.

After a period at Columbia University, he moved to Illinois to work in Leon Ledermann’s group at the newly built Fermilab. Here he helped to develop electron and muon identification techniques, which would prove fruitful in future electroweak experiments. The group did not discover the W and Z, but did find a signal that was later associated with charm mesons. Returning to Rutherford, soon to be Rutherford Appleton Laboratory (RAL), in 1974 David was quickly promoted to senior researcher. Realising that the future lay in “counter” physics, rather than bubble chambers, he worked on hadron–proton scattering in the resonance region. With the PETRA collider at DESY announced soon afterwards, David helped to form the UK contribution to the TASSO experiment, which made important measurements of electron–positron scattering. The PETRA experiments would go on to discover the gluon, enabling the Standard Model to be constructed with confidence.

After PETRA came HERA, which remains the world’s only high-energy electron–proton collider. David first led the RAL team working on the central tracking detector for the ZEUS experiment, but it was not long before he was invited to the newly reinstituted Kelvin professorship at the University of Glasgow, where he arrived in 1990 and spent the remainder of his academic career. He built the group significantly, its present healthy state founded on what he achieved. In addition to taking Glasgow into ZEUS, he nurtured many other activities – in particular involvement in the ALEPH experiment at LEP – and was instrumental in the design of central tracking systems for projects that eventually combined to become ATLAS.

David was instrumental in the design of central tracking systems for projects that eventually combined to become ATLAS

He was hardly installed in Glasgow before being appointed for several years as chair to the UK’s former Particle Physics Committee. There was no more important position to hold at the time, and David’s good sense, insight and intelligence helped to enable the subject to survive and prosper during a time when funding was tight and the UK funding system was being reorganised. Undaunted, he convinced the group in Glasgow that now was an excellent opportunity to host the 1994 edition of ICHEP.

David was one of the most sociable of people, always a good team player and invariably provocative and stimulating in conversation. Inevitably, the call came to move higher up in the university, first as a highly regarded head of department and later as dean of the science faculty – a post he occupied until shortly before his retirement. Meanwhile, he served on numerous local, national and international committees, including the UK CERN delegation and CERN policy committees, where his perceptiveness was always in demand. The UK recognised his distinguished and important contributions to science with the award of an OBE.

It was a sadness that his final years were marked by Parkinson’s disease, but he still participated in CERN Council meetings. He was at all times supported by his wife Margaret, with whom he had a son and a daughter, and found strength and comfort in his church membership. Those who were fortunate enough to know and work with David will never forget his positive and energetic character, always fair-minded, competitive without being aggressive, and caring. He will be much missed, and inspirational memories will remain.

Commemorating Bruno Touschek’s centenary

touschek_featured_img — Bruno Touschek, pictured here in the 1950s, was one of the first physicists in Europe who was
skilled in elementary particle theory and in functioning of accelerators. Credit: F Touschek

Bruno Touschek was born in Vienna on 3 February 1921. His mother came from a well-to-do Jewish family and his father was a major in the Austrian Army. Bruno witnessed the tragic consequences of racial discrimination that prevented him from both completing his high school and university studies in Austria. But he also experienced the hopes of the post-war era and played a role in the post-war reconstruction. With the help of his friends, he continued his studies in Hamburg, where he worked on the 15 MeV German betatron proposed by Rolf Widerøe and learnt about electron accelerators. After the war he obtained his PhD at the University of Glasgow in 1949 , where he was involved in theoretical studies and in the building of a 300 MeV electron synchrotron. Touschek emerged from the early-post war years as one of the first physicists in Europe endowed with a unique expertise in the theory and functioning of accelerators. His genius was nurtured by close exchanges with Arnold Sommerfeld, Werner Heisenberg, Max Born and Wolfgang Pauli, among others, and flourished in Italy, where he arrived in 1953 called by Edoardo Amaldi, his first biographer and first Secretary-General of CERN.

In 1960 he proposed and built the first electron-positron storage ring, Anello di Accumulazione (AdA), which started operating in Frascati in February 1961. The following year, in order to improve the injection efficiency, a Franco-Italian collaboration was born that brought AdA to Orsay. It was here that the “Touschek effect“, describing the loss and scattering of charged particles in storage rings, was discovered and the proof of collisions in an electron-positron ring was obtained.

AdA paved the way to the electron-positron colliders ADONE in Italy, ACO in France, VEPP-2 in the USSR and SPEAR in the US. Bruno spent the last year of his life at CERN, from where – already quite ill – he was brought to Innsbruck, Austria, where he passed away on 25 May 1978 aged just 57.

touschek_sketch — Bruno Touschek’s playful portrayal of T D Lee and parity violation. Credit: F Touschek

Bruno Touschek’s life and scientific contributions were celebrated at a memorial symposium from 2 to 4 December, held in the three institutions where Touschek has left a lasting legacy: Sapienza University of Rome, INFN Frascati National Laboratories and Accademia Nazionale dei Lincei. Contributions also came from the Irène Joliot-Curie Laboratoire, and sponsorship from the Austrian Embassy in Italy.

In addition to Touschek’s impact on the physics of particle colliders, the three-day symposium addressed the present-day landscape. Carlo Rubbia and Ugo Amaldi gave a comprehensive overview of the past and future of particle colliders, followed by talks about physics at ADONE and LEP, and future machines, such as a muon collider, the proposed Future Circular Collider at CERN and the Circular Electron Positron Collider in China, as well as new developments in accelerator techniques. ADONE’s construction challenges were remembered. Developments in particle physics since the 1960s – including the quark model, dual models and string theory, spontaneous symmetry breaking and statistical physics – were described in testimonies from the universities of Rome, Frascati, Nordita and Collège de France.

Touschek’s direct influence was captured in talks by his former students, from Rome and the Frascati theory group, which he founded in the mid 1960s. His famous lectures on statistical mechanics, given from 1959 to 1960, were remembered by many speakers. Giorgio Parisi, who graduated with Nicola Cabibbo, recollected the years in Frascati after the observation of a large hadron multiplicity in e⁺ e^– annihilations made by ADONE, and the ideas leading to QCD.

The final day of the symposium, which took place at the Accademia dei Lincei where Touschek had been a foreign member since 1972, turned to future strategies in high-energy physics, including neutrinos and other messengers from the universe. Also prominent were the many benefits brought to society by particle accelerators, reaffirming the intrinsic broader value of fundamental research.

Touschek’s life and scientific accomplishments have been graphically illustrated in the three locations of the symposium, including displays of his famous drawings on academic life in Roma and Frascati. LNF’s visitor center was dedicated to Touschek, in the presence of his son Francis Touschek.

Celebrating 20 years of n_TOF

The Neutron Time Of Flight (n_TOF) facility at CERN, a project proposed by former Director General Carlo Rubbia in the late 1990s, started operations in 2001. Its many achievements during the past two decades, and future plans in neutron science worldwide, were the subject of a one-day hybrid event NSTAPP – Neutrons in Science, Technology and Applications organised by the n_TOF collaboration at CERN on 22 November.

At n_TOF, a 20 GeV/c proton beam from the Proton Synchrotron (PS) strikes an actively cooled pure-lead neutron spallation target. The generated neutrons are water-moderated to produce a spectrum that covers 11 orders of magnitude in energy from GeV down to meV. At the beginning, n_TOF was equipped with a single experimental station, located 185 m downstream from the spallation target. In 2014, a major upgrade saw the construction and operation of a new experimental test area located 20 m above the production target to allow measurements of very low-mass samples. Last year, during Long Shutdown 2, a new third-generation, nitrogen-cooled spallation target was installed and successfully commissioned to prolong the experiment’s lifetime by ten years. At the same time, a new close-to-target irradiation and experimental station called NEAR was added to perform activation measurements relevant nuclear astrophysics and measurements in collaboration with the R2E (Radiation to Electronics) project that are difficult at other facilities.

Advancing technology

During 20 years of activities, the n_TOF collaboration has carried out more than 100 experiments with considerable impact on nuclear astrophysics, advanced nuclear technologies and applied nuclear sciences, including novel medical applications. Understanding the origin of the chemical elements through the slow-neutron-capture process has been a particular highlight. The high instantaneous neutron flux, which is only available at n_TOF thanks to the short proton pulse delivered by the PS, provided key reaction rates relevant to big-bang nucleosynthesis and stellar evolution (the former attempting to explain the discrepancy between the predicted and existing amount of lithium by investigating ⁷Be creation and destruction, and the latter determining the chemical history of our galaxy).

Basic nuclear data are also essential for the development of nuclear-energy technology. It was this consideration that motivated Rubbia to propose a spallation neutron source at CERN in the first place, prompting a series of accurate neutron cross-section measurements on minor actinides and fission products. Neutron reaction processes on thorium, neptunium, americium, curium, in addition to minor isotopes of uranium and plutonium, have been all measured at n_TOF. These measurements provide the nuclear data necessary for the development of advanced nuclear systems, such as the increase of safety margins in existing nuclear plants as well as to enable generation-IV reactors and accelerator-driven systems, or even enabling new fuel cycles which reduce the amount of long-lived nuclear species.

Basic nuclear data are also essential for the development of nuclear-energy technology

Contributions from external laboratories, such as J-PARC (Japan), the Chinese Spallation Neutron Source (China), SARAF (Israel), GELINA (Belgium), GANIL (France) and Los Alamos (US), highlighted synergies in the measurement of neutron-induced capture, fission and light-charged-particle reactions for nuclear astrophysics, advanced nuclear technologies, and medical applications. Moreover, technologies developed at CERN have also influenced the creation of two startups, Transmutex and Newcleo. The former focuses on accelerator-driven systems for energy production, for which the first physics validation was executed at the FEAT and TARC experiments at the CERN PS in 1999, while the latter plans to develop critical reactors based on liquid lead.

With the recent technical upgrades and the exciting physics programme in different fields, such as experiments focusing on the breaking of isospin symmetry in neutron-neutron scattering and pursuing its core experimental activities, the n_TOF facility has a bright future ahead.

Costas Kounnas 1952–2022

Renowned Cypriot–French theoretical physicist Costas Kounnas passed away suddenly on 21 January, two days before his 70th birthday. Born in Famagusta, Cyprus, Costas did his undergraduate studies at the National and Kapodistrian University of Athens before moving to Paris for his advanced degree. His studies were interrupted by military service during the events in Cyprus in 1974, after which he completed his PhD at the École polytechnique, carrying out important calculations of QCD effects in deep inelastic scattering and jets. He joined the CNRS in 1980, and later took up a postdoctoral fellowship at CERN, where he made seminal contributions to models of supersymmetry and supergravity. In particular, he helped develop supergravity models in which supersymmetry was broken spontaneously without generating any vacuum energy – a bugbear of globally supersymmetric theories. Working with Costas on these models was one of our most exhilarating collaborations.

Costas then moved to Berkeley where he became a world expert in the construction of string models, showing in particular how they could be formulated directly in four dimensions, without invoking the compactification of extra dimensions. In 1987 he took up a position at the École normale supérieure in Paris, where he remained for the rest of his career, apart from a CERN staff position between 1993 and 1998. Many of his best-known papers during these periods concerned cosmological aspects of string models, loop corrections and the breaking of supersymmetry – topics in which he was a world leader. He was also director of the theoretical physics group at the École normale supérieure between 2009 and 2013.

Costas showed how string models could be formulated directly in four dimensions

Among his accolades, Costas was awarded the Paul Langevin Prize of the French Physical Society in 1995 and the Gay-Lussac Humboldt Prize in 2013 for outstanding scientific contributions, especially to cooperation between Germany and France. In addition, he received a prestigious Research Award from the Adolf von Humboldt Foundation in 2014.

His many friends mourn the passing, not just of a distinguished theoretical physicist, but also of a warm colleague with a great heart that he was not shy of wearing on his sleeve. Costas enjoyed participating exuberantly in scientific discussions, always with the overriding aim of uncovering the truth. We remember a joyful and energetic friend who was passionate about many other aspects of life beyond science, including his many friendships and his home island of Cyprus. He was active in efforts to develop its relations with CERN, where it is now an Associate Member on its way towards full membership.

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