This carefully crafted edition highlights the scientific life of 2004 Nobel laureate Frank Anthony Wilczek, and the developments of theoretical physics related to his research. Frank Wilczek: 50 Years of Theoretical Physics is a collection of essays, original research papers and the reminiscences of Wilczek’s friends, students and followers. Wilczek is an exceptional physicist with an extraordinary mathematical talent. The 23 articles represent his vivid research journey from pure particle physics to cosmology, quantum black holes, gravitation, dark matter, applications of field theory to condensed matter physics, quantum mechanics, quantum computing and beyond.
In 1973 Wilczek discovered, together with his doctoral advisor David Gross, asymptotic freedom through which the field theory of the strong interaction, quantum chromodynamics (QCD), was firmly established. Independently that year, the same work was done by David Politzer, and all three shared the Nobel prize in 2004. Wilczek’s major work includes the solution of the strong-CP problem by predicting the hypothetical axion, a result of the spontaneously broken Peccei–Quinn symmetry. In 1982 he predicted the quasiparticle “anyon”, for which evidence was found in a 2D electronic system in 2020. This satisfies the need for a new variant for 2D systems as the properties of fermions and bosons are not transferable.
Original research papers included in this book were written by pioneering scientists, such as Roman Jackiw and Edward Witten, who are either co-inventors or followers of Wilczek’s work. The articles cover recent developments of QCD, quantum-Hall liquids, gravitational waves, dark energy, superfluidity, the Standard Model, symmetry breaking, quantum time-crystals, quantum gravity and more. Many colour photographs, musical tributes to anyons, memories of quantum-connection workshops and his contribution to the Tsung-Dao Lee Institute in Shanghai complement the volume. The book ends with Wilczek’s publication list, which documents the most significant developments in theoretical particle physics during the past 50 years.
Wilczek is an exceptional physicist with an extraordinary mathematical talent
Though this book is not an easy read in places, and the connections between articles are not always clear, a patient and careful reader will be rewarded. The collection combines rigorous scientific discussions with an admixture of Wilczek’s life, wit, scientific thoughts and teaching – a precious and timely tribute to an exceptional physicist.
SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East) is the Middle East’s first major international research centre. It is a regional third-generation synchrotron X-ray source situated in Allan, Jordan, which broke ground on 6 January 2003 and officially opened on 16 May 2017. The current members of SESAME are Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, Palestine and Turkey. Active current observers include, among others: the European Union, France, Germany, Greece, Italy, Japan, Kuwait, Portugal, Spain, Sweden, Switzerland, the UK and the US. The common vision driving SESAME is the belief that human beings can work together for a cause that furthers the interests of their own nations and that of humanity as a whole.
The story of SESAME started at CERN 30 years ago. One day in 1993, shortly after the signature of the Oslo Accords by Israel and the Palestine Liberation Organization, the late Sergio Fubini, an outstanding scientist and a close friend and collaborator, approached me in the corridor of the CERN theory group. He told me that now was the time to test what he called “your idealism”, referring to future joint Arab–Israeli scientific projects.
CERN is a very appropriate venue for the inception of such a project. It was built after World War II to help heal Europe and European science in particular. Abdus Salam, as far back as the 1950s, identified the light source as a tool that could help thrust what were then considered “third-world” countries directly to the forefront of scientific research. The very same Salam joined our efforts in 1993 as a member of the Middle Eastern Science Committee (MESC), founded by Sergio, myself and many others to forge meaningful scientific contacts in the region. By joining our scientific committee, Salam made public his belief in the value of Arab–Israeli scientific collaborations, something the Nobel laureate had expressed several times in private.
To focus our vision, that year I gave a talk on the status of Arab–Israeli collaborations at a meeting in Torino held on the occasion of Sergio’s 65th birthday. Afterwards we travelled to Cairo to meet Venice Gouda, the Egyptian minister for higher education, and other Egyptian officials. At that stage we were just self-appointed entrepreneurs. We were told that president Hosni Mubarak had made a decision to take politics out of scientific collaborations with Israel, so together we organized a high-quality scientific meeting in Dahab, in the Sinai desert. The meeting, held in a large Bedouin tent on 19-26 November 1995, brought together about 100 young and senior scientists from the region and beyond. It took place in the weeks after the murder of the Israeli prime minister Yitzhak Rabin, for whom, at the request of Venice Gouda, all of us stood for a moment of silence in respect. The silence echoes in my ears to this day. The first day of the meeting was attended by Jacob Ziv, president of the Israeli Academy of Sciences and Humanities, which had been supporting such efforts in general. It was thanks to the additional financial help of Miguel Virasoro, director-general of ICTP at the time, and also Daniele Amati, director of SISSA, that the meeting was held. All three decisions of support were made at watershed moments and on the spur of the moment. The meeting was followed by a very successful effort to identify concrete projects in which Arab–Israeli collaboration could be beneficial to both sides.
But attempts to continue the project were blocked by a turn for the worse in the political situation. MESC decided to retreat to Torino, where, during a meeting in November 1996, there was a session devoted to studying the possibilities of cooperation via experimental activities in high-energy physics and light-source science. During that session, the late German scientist Gus Voss suggested (on behalf of himself and Hermann Winnick from SLAC) to bring the parts of a German light source situated in Berlin, called BESSY, which was about to be dismantled, to the Middle East. Former Director-General of CERN Herwig Schopper also attended the workshop. MESC had built sufficient trust among the parties to provide an appropriate infrastructure to turn such an idea into something concrete.
Targeting excellent science
A light source was very attractive thanks to the rich diversity of fields that can make use of such a facility, from biology through chemistry, physics and many more to archaeology and environmental sciences. Such a diversity would also allow the formation of a critical mass of real users in the region. The major drawback of the BESSY-based proposal was that there was no way a reconstructed dismantled “old” machine would be able to attract first-class scientists and science.
Around that time, Fubini asked Schopper, who had a rich experience in managing complex experimental projects, to take a leadership position. The focus of possible collaborations was narrowed down to the construction of a large light source, and it was decided to use the German machine as a nucleus around which to build the administrative structure of the project. The non-relations among several of the members presented a serious challenge. At the suggestion of Schopper, following the example of the way CERN was assembled in the 1950s, the impasse was overcome by using the auspices of UNESCO to deposit the instruments for joining the project. The statutes of SESAME were to a large extent copied from those of CERN. A band of self-appointed entrepreneurs had evolved into a self-declared interim Council of SESAME, with Schopper as its president. The next major challenge was to choose a site.
On 15 March 2000 I flew to Amman for a meeting on the subject. I met Khaled Toukan (the current director-general of SESAME) and, after studying a map sold at the hotel where we met, we discussed which site Israel would support. We also asked that a Palestinian be the director general. Due to various developments, none of which depended on Israel, this was not to happen. The decision on the site venue was taken at a meeting at CERN on 11 April 2000. Jordan, which had and has diplomatic relations with all the parties involved, was selected as the host state. BESSY was dismantled by Russian scientists, placed in boxes and shipped with assembly instructions to the Jordanian desert to be kept until the appropriate moment would arise. This was made possible thanks to a direct contribution by Koichiro Matsuura, director-general of UNESCO at the time, and to the efforts of Khaled Toukan who has served in several ministerial capacities in Jordan.
With the administrative structure in place, it was time to address the engineering and scientific aspects of the project. Technical committees had designed a totally new machine, with BESSY serving as a boosting component. Many scientists in the region were introduced via workshops to the scientific possibilities that SESAME could offer. Scientific committees considered appropriate “day-one” beamlines, yet that day seemed very far in the future. Technical and scientific directors from abroad helped define the parameters of a new machine and identified appropriate beamlines to be constructed. Administrators and civil servants from the members started meeting regularly in the finance committee. Jordan began to build the facility to host the light source and made major additional financial contributions.
Transformative agreements
At this stage it was time for the SESAME interim council to transform into a permanent body and in the process cut its umbilical cord from UNESCO. This transformation presented new hurdles because it was required of every member that wished to become a member of the permanent council that its head of state, or someone authorised by the head of state, sign an official document sent to UNESCO stating this wish.
By 2008 the host building had been constructed. But it remained essentially empty. SESAME had received support from leading light-source labs all over the world – a spiritual source of strength to members to continue with the project. However, attempts to get significant funding failed time and again. It was agreed that the running costs of the project should be borne by the members, but the one-time large cost needed to construct a new machine was outside the budget parameters of most of the members, many of whom did not have a tradition of significant support for basic science. The European Union (EU) supported us in that stage only through its bilateral agreement with Jordan. In the end, several million Euros from those projects did find their way to SESAME, but the coffers of SESAME and its infrastructure remained skeletal.
Changing perceptions
In 2008 Herwig Schopper was succeeded by Chris Llewellyn Smith, another former Director-General of CERN, as president of the SESAME Council. His main challenge was to get the funding needed to construct a new light source and to remove from SESAME the perception that it was simply a reassembled old light source of little potential attraction to top scientists. In addition to searching for sources of significant financial support, there was an enormous amount of work still to be done in formulating detailed and realistic plans for the following years. A grinding systematic effort began to endow SESAME with the structure needed for a modern working accelerator, and to create associated information materials.
Llewellyn Smith, like his predecessor, also needed to deal with political issues. For the most part the meetings of the SESAME Council were totally devoid of politics. In fact, they felt to me like a parallel universe where administrators and scientists from the region get to work together in a common project, each bringing her or his own scars and prejudices and each willing to learn. That said, there were moments when politics did contaminate the spirit forming in SESAME. In some cases, this was isolated and removed from the agenda and in others a bitter taste remains. But these are just at the very margins of the main thrust of SESAME.
The empty SESAME building started to be filled with radiation shields, giving the appearance of a full building. But the absence of the light-source itself created a void. The morale of the local staff was in steady decline, and it seemed to me that the project was in some danger. I decided to approach the ministry of finance in Israel. When I asked if Israel would make a voluntary contribution to SESAME of $5 million, I was not shown the door. Instead they requested to come and see SESAME, after which they discussed the proposal with Israel’s budget and planning committee and agreed to contribute the requested funds on the condition that others join them.
Each member of the unlikely coalition – consisting of Iran, Israel, Jordan and Turkey – pledged an extra $5 million for the project in an agreement signed in Amman. Since then, Israel, Jordan and Turkey have stood up to their commitment, and Iran claims that it recognises its commitment but is obstructed by sanctions. The support from members encouraged the EU to dedicate $5 million to the project, in addition to the approximately $3 million directed earlier from a bilateral EU–Jordan agreement. In 2015 the INFN, under director Fernando Ferroni, gave almost $2 million. This made it possible to build a hostel, as offered by most light sources, which was named appropriately after Sergio Fubini. Many leading world labs, in a heartwarming expression of support, have donated equipment for future beam lines as well as fellowships for the training of young people.
Point of no return
With their help, SESAME crossed the point of no return. The undefined stuff dreams are made of turned into magnets and girdles made of real hard steel, which I was able to touch as they were being assembled at CERN. The pace of events had finally accelerated, and a star-studded inauguration including attendance by the king of Jordan took place on 16 May 2017. During the ceremony, amazingly, the political delegates of different member states listened to each other without leaving the room (as is the standard practice in other international organisations). Even more unique was that each member-state delegate taking the podium gave essentially the same speech: “We are trying here to achieve understanding via collaboration.”
At that moment the SESAME Council presidency passed from Chris Llewellyn Smith to a third former CERN Director-General, Rolf Heuer. The high-quality 2.5 GeV electron storage ring at the heart of SESAME started operation later that year, driving two X-ray beamlines: one dedicated to X-ray absorption fine structure/X-ray fluorescence (XAFS/XRF) spectroscopy, and another to infrared spectro-microscopy. A third powder-diffraction beamline is presently being added, while a soft X-ray beamline “HESEB” designed and constructed by five Helmholtz research centres is being commissioned. In 2023 the BEAmline for Tomography at SESAME (BEATS) will also be completed, with the construction and commissioning of a beamline for hard X-ray full-field tomography.
The unique SESAME facility started operating with uncanny normality. Well over 100 proposals for experiments were submitted and refereed, and beam time was allocated to the chosen experiments. Data was gathered, analysed and the results were and are being published in first-rate journals. Given the richness of archaeological and cultural heritage in the region, SESAME’s beamlines offer a highly versatile tool for researchers, conservators and cultural-heritage specialists to work together on common projects. The first SESAME Cultural Heritage Day took place online on 16 February 2022 with more than 240 registrants in 39 countries (CERN Courier July/August 2022 p19).
Thanks to the help of the EU, SESAME has also become the world’s first “green” light source, its energy entirely generated by solar power, which also has the bonus of stabilising the energy bill of the machine. There is, however, concern that the only component used from BESSY, the “Microtron” radio-frequency system, may eventually break down, thus endangering the operation of the whole machine.
SESAME continues to operate on a shoe-string budget. The current approved 2022 budget is about $5.3 million, much smaller than that of any modern light source. I marvel at the ingenuity of the SESAME staff allowing the facility to operate, and am sad to sense indifference to the budget among many of the parties involved. The world’s media has been less indifferent: the BBC, The New York Times, Le Monde, The Washington Post, Brussels Libre, The Arab Weekly, as well as regional newspapers and TV stations, have all covered various aspects of SESAME. In 2019 the AAAS highlighted the significance of SESAME by awarding five of its founders (Chris Llewellyn Smith, Eliezer Rabinovici, Zehra Sayers, Herwig Schopper and Khaled Toukan) with its 2019 Award for Science Diplomacy.
SESAME was inspired by CERN, yet it was a much more challenging task to construct. CERN was built after the Second World War was over, and it was clear who had won and who had lost. In the Middle East the conflicts are not over, and there are different narratives on who is winning and who is losing, as well as what win or lose means. For CERN it took less than 10 years to set up the original construct; for SESAME it took about 25 years. Thus, SESAME now should be thought of as CERN was in around 1960.
On a personal note, it brings immense happiness that for the first time ever, Israeli scientists have carried out high-quality research at a facility established on the soil of an Arab country, Jordan. Many in the region and beyond have taken their people to a place their governments most likely never dreamt of or planned to reach. It is impossible to give due credit to the many people without whom SESAME would not be the success it is today.
The non-relations among several of the members presented a serious challenge
In many ways SESAME is a very special child of CERN, and often our children can teach us important lessons. As president of the CERN Council, I can say that the way in which the member states of SESAME conducted themselves during the decades of storms that affect our region serves as a benchmark for how to keep bridges for understanding under the most trying of circumstances. The SESAME spirit has so far been a lighthouse even to the CERN Council, in particular in light of the invasion of Ukraine (an associate member state of CERN) by the Russian Federation. Maintaining this attitude in a stormy political environment is very difficult.
However SESAME’s story ends, we have proved that the people of the Middle East have within them the capability to work together for a common cause. Thus, the very process of building SESAME has become a beacon of hope to many in our region. The responsibility of SESAME in the next years is to match this achievement with high-quality scientific research, but it requires appropriate funding and help. SESAME is continuing very successfully with its mission to train hundreds of engineers and scientists in the region. Requests for beam time continue to rise, as do the number of publications in top journals.
If one wants to embark on a scientific project to promote peaceful understanding, SESAME offers at least three important lessons: it should be one to which every country can contribute, learn and profit significantly from; its science should be of the highest quality; and it requires an unbounded optimism and an infinite amount of enthusiasm. My dream is that in the not-so-distant future, people will be able to point to a significant discovery and say “this happened at SESAME”.
The latest edition of the CERN Alumni Network’s “Moving out of academia” series, held on 21 October, focused on how to successfully manage a transition from academia to the big- tech industry. Six panellists who have started working in companies such as Google, Microsoft, Apple and Meta shared their advice and experience on how to successfully start a career in a large multinational company after having worked at large scale-research infrastructures such as CERN.
In addition to describing the nature of their work and the skills acquired at CERN that have helped them make the transition, the panellists explained which new skills they had to develop after CERN for a successful career move. The around 180 participants who attended the online event received tips for interviews and CV-writing and heard personal stories about how a PhD prepares you for a career outside academia.
The panellists agreed that metrics used in academia to qualify a person’s success, such as a PhD, the h-index, or the number of published papers, do not necessarily apply to roles outside of academia, except for research positions. “You don’t need to have a PhD or a certificate to demonstrate that you are a good problem solver or a good programmer – you should do a PhD because you are interested in the field,” said Cristina Bahamonde, who used to work in accelerator operations at CERN and now oversees and unblocks all Google’s network deployments as regional leader for its global network delivery team in Europe, the Middle East and Africa. She considers her project-management and communication skills, which she acquired during her time at CERN while designing solution and mitigation strategies for operational changes in the LHC, essential for her current role.
General skills needed for big-tech companies include the ability to learn and adapt fast, project and product-management skills, as well as communicating effectively to technical and non-technical audiences. Some participants were unaware that skills that they sharpened intuitively throughout their academic career are vital for a career outside.
“CERN taught me how to be a generalist,” says James Casey, now a group programme manager at Microsoft. “I was not working as a product manager at CERN, but you do very similar work at CERN because you write documents, build customer relationships and need to communicate your work in an understandable way as well as to communicate the work that needs to be done.” At CERN in 1994, Casey worked as a summer student alongside the original team that developed the web. After having worked in start-ups, he returned to CERN for a while and then moved back to industry in 2011.
Finding the narrative
Finding your own narrative and presenting it in the right way on a resumé is not always easy. “When I write my resumé, it looks really straight forward,” said Mariana Rihl, former LHCb experimentalist and now Meta’s product-system validation lead for verifying and validating Oculus VR products. “But only after a certain time, I realised that a common theme emerged — testing hardware and understanding users’ needs.” Working on the LHCb beam-gas vertex detector and especially ensuring the functionality of detector hardware prepared her well, she said.
Former CERN openlab intern Ritika Kanade, who now works as a software engineer at Apple, shared her experience of interviewing people applying for software engineering roles. “What I like to see during an interview is how the applicant approaches the tasks and how he or she interacts with me. It’s ok if someone needs help. That’s normal in our job,” she adds. “Time management is one thing I see many candidates struggle with.” Other skills needed in industry as well as in academia are tenacity and persistence. Often, candidates need to apply more than three times to land a job at their favourite company. “I applied six or seven times before I was invited for an interview at Google,” emphasised Bahamonde.
The Moving out of academia series provides a rich source of advice for those seeking to make a career change, with the latest event followingothers dedicated to careers in finance, industrial engineering, big data, entrepreneurship, the environment and medical technologies. “This CERN Alumni event demonstrated once more the impact of high-energy physics on society and that people transitioning from academia to industry bring fresh insights from another field,” said Rachel Bray, head of CERN Alumni relations.
Experimentalist Volker Soergel passed away on 5 October at the age of 91. Born in Breslau in March 1931, Soergel was a brilliant experimental physicist and an outstanding leader, shaping particle physics for many years.
Receiving a doctorate from the University of Freiburg in 1956 under the tutelage of Wolfgang Gentner, Soergel remained at Freiburg until 1961, with a year at Caltech in 1957–1958. He then joined CERN as a research associate, working with Joachim Heintze on the beta decay of elementary particles, especially very rare decays of mesons and hyperons. Their results became milestones in the development of the Standard Model, resulting in the award of the German Physical Society’s highest honour in 1963.
In 1965 Soergel became a professor at the University of Heidelberg. He continued his research at CERN while taking on important roles at the university: as director of the Institute of Physics, as dean and as a member of the university’s administrative council. With vision and skill, he played a major role in shaping the university.
Important tasks outside Heidelberg followed. From 1976–1979 he chaired the DESY Scientific Council through a period that saw work begin on the electron–positron collider, PETRA. Under his leadership, the council played an important role in DESY’s transition from national to international laboratory. In 1979 and 1980 he served as research director at CERN, helping pave the way for the collider experiments of the 1980s.
From 1981–1993 Soergel headed DESY, overseeing construction of the electron–proton storage ring, HERA, together with Björn Wiik and Gustav-Adolph Voss. HERA and its experiments benefited from large international contributions, mainly in the form of components and manpower: an approach that became known as the HERA model. Soergel’s powers of persuasion, his reputation, and his negotiating skills led to support from institutes in Western Europe, Israel and Canada, as well as from Poland, Russia and China. From 1996–2000 he headed the Max Planck Institute for Physics in Munich. Under his guidance, photon science became an important pillar of DESY research, first as a by-product of accelerators used for particle physics, then, with the inauguration of HASYLAB in 1981 and the conversion of DORIS, as an established research field that continues strongly to this day.
Soergel’s time at DESY coincided with German reunification. He enabled the merger of the Institute for High Energy Physics in Zeuthen, near Berlin, with DESY and, together with Paul Söding, made Zeuthen a centre for astroparticle physics. Even before the Iron Curtain fell, Soergel personally ensured that Zeuthen scientists could work at DESY.
Volker Soergel received many honours. He was awarded the Federal Cross of Merit, 1st class, and honorary doctorates from the universities of Glasgow and Hamburg. He has left a lasting legacy. His love for physics was similar in intensity to his love for music. A gifted violin and viola player, he enjoyed making music with his wife and children, friends and colleagues. All who worked with him remain grateful for all they learned from him and will not forget his support and guidance.
Renowned high-energy theorist Nicola Najib Khuri died on 4 August 2022 in New York City. Born in 1933 in Beirut, Lebanon he was the eldest of four siblings and a precocious student. He graduated from the American University of Beirut (AUB) in 1952 at the age of 19, then travelled to the US for his graduate studies in physics. He received his MA and PhD from Princeton University and was a fellow of Princeton’s Institute for Advanced Study. While in graduate school, he met Elizabeth Tyson, the love of his life and wife of over 60 years. Upon receiving his doctorate in 1957, Nicola returned to Lebanon and joined the faculty at AUB. In 1964 he went back to the US and accepted a position at The Rockefeller University, New York, where he founded a lab and remained for the rest of his career.
Nicola was a leading authority on the use of mathematics in high-energy theoretical physics. At Rockefeller, his research focused on the mathematical description of elementary-particle collisions. Among his most notable achievements were the introduction of a new method to study the Riemann hypothesis, one of the last unsolved problems in mathematics, and the foundation of the field of potential scattering theory, which led to the development of important concepts such as Regge poles and strings.
In addition to his post at Rockefeller, he held visiting appointments and consulting roles at CERN, Stanford University, Columbia University, Lawrence Livermore National Laboratory, Brookhaven National Laboratory and Los Alamos National Laboratory. He was also a member of the panel on national security and arms control of the Carnegie Endowment for International Peace and a fellow of the American Physical Society.
Nicola and Liz, along with their two children, built a beautiful life in New York. Their homes had a revolving door for friends, family, colleagues and mentees who came from far and wide to hear Nicola’s remarkable stories, take in his sage advice, and enjoy his timeless, occasionally risqué jokes. A true cosmopolitan, he relished the vibrancy and possibility of New York. When not at home, he could be found ordering mezze for the table at one of his favourite Lebanese restaurants, exploring his interest in international politics at the Council on Foreign Relations, or making a toast at the Century Association. He retained an enduring love for, and a fundamental commitment to, Lebanon. He was a passionate supporter of his alma mater, a mentor to generations of young scientists from the Middle East, and was instrumental in establishing the university’s Center for Advanced Mathematical Sciences, among many other contributions.
There are many things we will miss about Nicola: his character; the way he commanded a room; his childlike sense of humour; the happy gleam in his eye when he told a story from his adventurous life; and his sneaky determination in old age to satisfy a lifelong appetite for good wine, good cheese and excellent chocolate over the protests of doctors, caregivers and his daughter, Suzanne. Above all, we will miss the way he treated others.
“Reality is not what it seems: Drawing links between fine art and particle physics” was the title of the art–science exhibit set up by the Laboratoire d’Annecy de Physique des Particules (LAPP) on the occasion of the 2022 Fête de la Science. The installation was part of an ongoing collaboration between UK fine artist Ian Andrews and ATLAS physicist Kostas Nikolopoulos called “The Sketchbook and the Collider”, which was initiated in 2018 while Andrews was an artist in residence at the University of Birmingham. The project takes viewers on a journey where the artist’s sketchbook and the experimental physicist’s collider can both be seen as arenas where the invisible is made visible, “sometimes violently”, by bringing elements together and examining the traces of hidden interactions. It also comprises performative pieces that involve “live” drawing and the cooperation, participation and interaction of artists, scientists and members of the public.
“About 900 visitors spanning all ages, professions and cultural backgrounds engaged and interacted with the exhibition, either attracted by the arts and the science, or caught by surprise on their way to Lake Annecy, in a very special Higgs and LHC celebration year,” said organiser Claire Adam-Bourdarios of LAPP.
After one-year delay due to the COVID pandemic, the 8th edition of the International Symposium on Subatomic Physics (SSP2022) took place in Vienna from 29 August to 2 September. Organised by the Stefan Meyer Institute for subatomic physics (SMI) of the Austrian Academy of Sciences and hosted at the University of Applied Arts, the in-person conference attracted 74 participants.
The conference programme began with a warm welcome from Eberhard Widmann (Austrian Academy of Sciences) who was delighted to resume the SSP series, the last one held in Aachen in spring 2018. As proposed by the International Advisory Committee, the scientific programme this year focused more on fundamental symmetries and interactions in theory and laboratory experiments compared to previous editions and included topics such as dark matter and cosmology. 51 invited and contributed talks, as well as 17 posters were presented, highlighting scientific achievements worldwide.
These included topics on searches for lepton-flavour violation and symmetries in heavy quark decays at BELLE in Japan, BESIII in Beijing, muon-decay experiments at the Paul Scherrer Institute, and the first direct test of T and CPT symmetries in Φ decays at DAΦNE in Frascati. Prospects to discover physics beyond the Standard Model, such as the g-2 measurement at Fermilab, or at high-energy colliders were also presented, as well as searches for the electric dipole moments (EDM) of the neutron, deuteron, muon and in atoms and molecules. Double β-decay experiments, sterile-neutrino searches and flavour oscillations were also discussed. Results and upper limits on CPT tests with antihydrogen, muonium and positronium were reported.
The meeting ended with presentations on advanced instrumentation and on upcoming future facilities at PSI, DESY, Mainz university and J-PARC. Many participants from regions such as China attended the conference online. Discussions on various subjects followed during the poster session, where master and PhD students presented their work and results. Stefan Paul (TU Munich) gave a public lecture in the picturesque Festsaal of the Austrian Academy of Sciences about the shortest length scales that humankind has explored so far and how laboratory experiments test theoretical models describing the beginning of the universe.
SSP2022 was a successful and enjoyable conference, which created many fruitful and at times lively discussions in the field of symmetries in subatomic physics. The many contributions together with the social events around the conference programme provided an inspiring environment for animated discussions. SSP2022 benefited from being a relatively small-scale conference and the natural lightness it brings when meeting new colleagues and carrying out in-depth conversations on physics topics that we are passionate about.
Kurt Gottfried, professor emeritus at Cornell University and co-founder of the Union of Concerned Scientists (UCS), passed away on 25 August 2022 at the age of 93. Throughout his career, he encouraged fellow scientists to hold their leaders to account on topics ranging from nuclear arms control to human rights and scientific integrity.
Gottfried was born in Vienna, Austria in 1929, fleeing the country with his family when he was nine years old after their home was raided on Kristallnacht, and eventually immigrating to Montreal, Canada. He graduated from McGill University, earned a PhD in theoretical physics from MIT in 1955 and was a junior fellow at Harvard. In 1964 he became a physics professor at Cornell and remained affiliated with the university until his death. He also served on the senior staff of CERN, as a chair of the division of particles and fields of the American Physical Society, and as a member of the American Academy of Arts and Sciences, and the Council on Foreign Relations.
Well known for his work in high-energy theoretical physics and the foundations of quantum mechanics, Gottfried worked with David Jackson in the 1960s on the production and decay of unstable resonances in hadronic collisions using the density-matrix approach. He proposed the Gottfried sum rule for deep inelastic scattering and is also known for his work in the 1970s on charmonium. Along with Tung-Mow Yan, he authored the classic work Quantum Mechanics: Fundamentals, originally published in 1966.
In 1969, deeply concerned about what he saw as the growing threat to civilisation from the unchecked exploitation of scientific knowledge for military purposes, Gottfried co-founded UCS with his friend and future Nobel laureate Henry Kendall. His many years of leadership and guidance helped expand the scope of the organisation’s work from research on nuclear power and weaponry, to climate change, agriculture, transportation and renewable energy. Even in retirement, Gottfried continued to advise UCS scientists on policy and strategy, and to inspire the organisation with his passionate sense of urgency about its work.
In the 1980s, working with Hans Bethe and Richard Garwin, Gottfried drew attention and acclaim to UCS by demonstrating the infeasibility of the “Star Wars” missile defence programme. He authored numerous scholarly articles on missile defence, space weapons, nuclear weapons and cooperative security, and reached an even wider audience with his articles and op-eds on these topics. He also authored or co-authored three books – The Fallacy of Star Wars (1984), Crisis Stability and Nuclear War (1988) and Reforging European Security: From Confrontation to Cooperation (1990) – and contributed chapters to several others.
Throughout his life, Gottfried also used his standing to advocate for the free practice of science. In addition to his work with UCS, he was deeply engaged in campaigns in support of scientists in the former Soviet Union and South America who were imprisoned for expressing views in conflict with the dogmas of authoritarian rulers. In 2016, citing his long and distinguished career as a “civic scientist”, the American Association for the Advancement of Science awarded Gottfried its Scientific Freedom and Responsibility Award.
As current UCS board chair Anne Kapuscinski noted, Kurt was the epitome of a concerned scientist and an inspiration to all of us. We will miss his passion, kindness, dedication and integrity, and we will strive to honour his lifelong dedication to building a safer world.
UK experimental particle physicist Don Perkins, who played a significant role in shaping the field from the 1940s onwards, passed away on 30 October at the age of 97.
After graduating from Imperial College, London, Perkins obtained a PhD under the supervision of George Paget Thomson, recipient of the 1937 Nobel Prize in Physics. As part of his thesis work, he took a photographic emulsion – a new medium for particle detection at the time – onto a Royal Air Force transport plane to record cosmic rays at altitude. This resulted in what was later recognised to be the first observation of the pion, published in Nature in 1947.
In 1951 Perkins joined another Nobel laureate, Cecil Powell, in Bristol where, working with Peter Fowler, he discovered some of the decay properties of pions. This involved touring some of the world’s mountain tops with photographic emulsions, as well as sending them into the stratosphere on balloons. As a result of their studies, Perkins and Fowler were the first to suggest that irradiation with negatively charged pions might be used to treat cancer. In 1965 Perkins moved to the University of Oxford where, under the overall leadership of Denys Wilkinson, he established a world-leading particle-physics group. One year later he was elected a Fellow of the Royal Society. In 1991 he received the Royal Medal of the Royal Society, among many honours that would crown his long career.
As modern electronic counters and bubble chambers began to replace emulsion techniques, Perkins worked at CERN, where in 1973 he contributed to the seminal discovery of neutral currents with the Gargamelle bubble chamber. Thirty years later, in characteristic style and peppered with anecdotes, Perkins recounted the story of the neutral-current discovery in this magazine (CERN Courier Commemorative Issue Willibald Jentschke June 2003 p15).
In the late 1960s, when the scattering of electrons off protons in experiments at SLAC had established that the proton is not elementary, Perkins realised that neutrino scattering could give complementary information that helped prove the existence of fractionally charged quarks. He was also an early supporter of quantum chromodynamics, which explained why quarks are confined inside hadrons.
As the 1970s progressed, Perkins became increasingly interested in proton decay, and was a leading advocate of the Soudan-II experiment in the US. Although Soudan-II never saw evidence of proton decay, the experiment made important contributions to advancing the field of neutrino physics.
Over his long career, Perkins’ brilliance benefitted generations of physics students, many of whom were drawn to particle physics through his textbook Introduction to High Energy Physics, first published in 1972 based on his undergraduate lectures and now in its fourth edition. Besides his experimental and theoretical contributions, Perkins was active in the governance of particle physics, having chaired both the nuclear physics board of the UK’s former Science and Engineering Research Council and CERN’s Scientific Policy Committee. He was a member of many international advisory committees and strategy meetings, including one in 1979 that led to the construction of the HERA electron–proton collider at DESY.
A charismatic and influential figure, his wisdom, delivered in a northern English accent and accompanied by his distinctive laugh, will be greatly missed by his many friends and colleagues.
After two online editions during the Covid pandemic, this year the annual TOP conference returned to an in-person format. The 2022 edition took place in the historic city of Durham in the UK from 4 to 9 September and attracted more than 100 participants.
The LHC collaborations that study the top quark presented a wealth of recent results based on Run 2 data, many of which were shown for the first time, and even included a measurement with the very first data collected in Run 3. CMS and ATLAS presented new top-quark mass results, new measurements of top-quark production asymmetries, new cross-section measurements as well as searches for new production and decay modes, both within and beyond the Standard Model (SM). These included ttW and four top-quark production, and processes involving flavour-changing-neutral-current interactions that could produce sizable rates beyond the SM prediction.
Earlier this year, CMS released a preliminary mass measurement that profiles all uncertainties, including a finely split set of signal-modelling uncertainties based on variations of Monte Carlo generators. To account for the limited statistical power for some of these variations, this precision analysis implements a fully consistent treatment of the resulting fluctuations leading to a 380 MeV uncertainty. ATLAS presented a top-quark mass measurement of 172.63 ± 0.20 (stat) ± 0.67 (syst) ± 0.37 (recoil) GeV. The last uncertainty represents the ambiguity in assigning the recoil of gluon emissions in the top-quark decay chain that was neither considered in Run 1 analyses nor in the CMS measurement and requires further studies. The large difference in the modelling uncertainties assigned by both collaborations underlines the importance to overcome the limitations of Monte Carlo generators for these precision measurements.
Run 2 of the LHC opens up new production processes that could not be probed at the Tevatron or in Run 1. Recently, ATLAS announced the observation of the rare production process of a single top quark and a photon, thus completing the list of associated top-quark production processes with SM gauge bosons. CMS followed with a brand-new analysis of the four top-quark production process, the rarest process accessible by the LHC to date. Together with combined ATLAS analyses, there is now very strong evidence that this elusive process exists. While most results in the classical top-quark pair and single-top production modes agree very well with the SM predictions, slight excesses are seen in several rare production modes, such as ttW and four-top production. None of these excesses are statistically significant, but they form an interesting pattern that requires experimental results and theory predictions to be considered extra carefully, while keeping an eye open for more exotic explanations.
Theory ahead
Theory contributions at TOP 2022 revolved around two major themes: precision calculations and beyond-SM models. For the former, several groups presented new calculations that enable a more precise comparison of measurements with SM predictions. These calculations provide an integrated treatment of the top-quark and boson decays, including off-shell effects, which are small in the total cross section, but which can be significantly enhanced locally in some corners of phase space. Including these effects is therefore relevant for the highest-precision differential measurements at the LHC. For the second theme, the most popular approach is to expand around the SM with minimal model dependence using effective field theory. This is complemented by more focussed efforts in concrete new-physics scenarios, including composite Higgs (and top) models as well as leptoquarks. A dedicated theory mini-workshop discussed the interplay of top-quark measurements with results in flavour physics.
Perhaps the most exciting result, the first at Run 3, was presented by CMS. On 5 July, just two months before the conference, the LHC switched back on after a three-year shutdown and started to produce the first proton-proton collisions at a record centre-of-mass energy of 13.6 TeV. Stretching over the next few years, Run 3 will increase the size of available datasets involving top quarks by a factor of three to four. Both ATLAS and CMS made a tremendous effort to prepare the detectors, to collect and check the quality of the data, and to provide preliminary calibrations for leptons and jets. In a race against the clock, CMS isolated the top-quark pair production process in the data collected in July and August in time for the conference. Even at this very early stage, the data are understood well enough that a cross-section measurement with a total uncertainty below 8% was possible by making use of the top-quark events themselves to calibrate most of the relevant experimental uncertainties in situ.
With these first results showing that the LHC and the experiments are smoothly operating, TOP22 kicks off the Run 3 top-quark physics programme. We can look back on a very exciting edition of the TOP conference and look forward to meeting again in Michigan in 2023.
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