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Sachio Komamiya 1952–2024

Sachio Komamiya

Sachio Komamiya, a prominent figure in the Japanese and International Linear Collider communities, passed away on 5 June 2024 at the age of 71.

Born in Yokohama, Japan in 1952, Komamiya graduated from the University of Tokyo in 1976. He remained there as a graduate student, under the mentorship of Masatoshi Koshiba. Komamiya began his diverse international career by proposing an experiment using the PETRA electron–positron collider at DESY in collaboration with Heidelberg University and the University of Manchester. This collaboration led to the JADE experiment. Koshiba’s laboratory took charge of developing the lead–glass electromagnetic shower detector, which operated reliably and contributed to the discovery of gluons.

After obtaining his PhD for his work at DESY, Komamiya took up a postdoc position at the University of Heidelberg, joining the group of Joachim Heintze. He quickly integrated himself into the group and to the JADE collaboration in general, and was one of the first to perform searches for supersymmetric particles – his enthusiasm for this type of analysis earning him the nickname “SachiNo”.

In 1986 Komamiya’s interest in the highest-energy experiments led him to SLAC as a staff physicist. The construction of the SLAC Linear Collider (SLC) – the first linear collider – was underway. The SLC was a single-pass collider that used a linac to accelerate both electrons and positrons, a design that was highly complex. Komamiya worked on developing the arcs that bent the beams at the end of the linac, which was one of the most complicated parts of the machine. Physics measurements at the SLC started in 1988 with the Mark II detector, and in 1990 Komamiya moved to Europe to join the OPAL experiment at the Large Electron Positron Collider.

Komamiya returned to Japan in 1999 and became a director of the International Center for Elementary Particle Physics at the University of Tokyo in 2000. While leading research and experiments there, he led Japan’s high-energy physics community, serving four terms as the chairman of the Japan Association of High Energy Physics and as a Japanese representative for the International Committee for Future Accelerators from 2000. His leadership and extensive international experience have been precious in advancing the International Linear Collider (ILC) project. In December 2012, a technical design report for the ILC was completed. Shortly afterwards, the ILC project was reorganised under the umbrellas of the Linear Collider Collaboration (LCC), led by Lyn Evans for project development, and the Linear Collider Board, which oversaw the LCC’s activity and was chaired by Komamiya.

Komamiya was eager to see the ILC become Japan’s first globally hosted project. He served as a diplomat to advance this vision, and was calm and patient when explaining to others the often-complex relations involved. Sachio thus fulfilled a critical and essential role bridging science and politics – a talent that, alongside his physics expertise, will be sorely missed.

Hans Joachim Specht 1936–2024

Hans Joachim Specht, one of the founders of ultra-relativistic heavy-ion physics and a pioneering figure in hadron cancer therapy, passed away on 20 May 2024 at the age of 87. A graduate of the University of Munich and ETH Zurich, and full professor at the University of Heidelberg for more than 30 years, his career was distinguished by important contributions across a spectrum of scientific domains.

Hans started his academic career in atomic and nuclear physics in Munich, under the guidance of Heinz Maier-Leibnitz. A highlight was the discovery and precise measurement of shape isomerism in heavy nuclei. His observation of distinct rotational bands in plutonium-240 showed, for the first time, that nuclei can be in a strongly deformed cigar-shaped state shortly before fission, confirming the concept of a “double-humped” fission barrier. In Munich, and later in Heidelberg, he developed several innovative large-scale detectors for fission fragments and reaction products of heavy-ion collisions, becoming one of the leading experimentalists in the new field of heavy-ion physics, with experiments at the MPI for Nuclear Physics in Heidelberg and at the newly founded GSI in Darmstadt.

In the early 1980s, Hans reoriented his research towards the higher energies available at CERN. His contributions and advocacy, alongside a handful of other enthusiastic proponents, were instrumental in establishing CERN’s ultra-relativistic heavy-ion programme at the SPS, which was approved in 1984. He became the spokesperson of a first-generation heavy-ion experiment (Helios/NA34-2), initiator and spokesperson of a second-generation experiment (CERES/NA45), and a crucial supporter of the third-generation ALICE experiment at the LHC.

Hans was a brilliant experimentalist with a keen eye for cutting-edge detector concepts and how to apply them in a minimalistic approach. This was apparent in his masterpiece, the dilepton experiment CERES, which used a “hadron blind” double Cherenkov detector and a specially crafted magnetic field configuration to pick out and measure the rare electrons from the haystack of hadrons.

Initially with CERES, and later as a leading force within NA60, Hans succeeded in detecting, for the first time, thermally produced lepton pairs in heavy-ion collisions; the original discovery with NA45 remains one of the most cited papers from the SPS heavy-ion programme. The high-precision measurements at NA60 of what is arguably one of the most challenging signals (the Planck-like spectrum of thermal radiation at higher masses), and the precise characterisation of the in-medium modification of the ρ meson at lower masses, proved to be crucial in establishing the existence and properties of quark–gluon plasma. The enduring quality and relevance of these measurements remain unsurpassed almost two decades later.

Throughout his career, Hans held numerous positions in the realm of science policy at a variety of German and international research institutes. At CERN, he served as chair of the PSCC committee and as a member of the SPC. He was also a founding member of the first board of directors of the theory institute ECT* in Trento, a place that held special significance for him.

Hans was a brilliant experimentalist with a keen eye for cutting-edge detector concepts

As scientific director of GSI from 1992 to 1999, Hans set the course for the development and application of a groundbreaking innovation in radiation medicine: ion-beam cancer therapy. A pilot project at GSI for the irradiation of tumours with carbon-12 ions successfully treated 450 patients and led to the establishment of the Heidelberg Ion-Beam Therapy Center, the first European ion-beam therapy facility. Reflecting on his achievements, he was most proud of his contributions to ion-beam therapy. Additionally, Hans initiated discussions on the long-term future of GSI, which eventually led to the proposal for the international FAIR facility.

Hans also had a profound interest in the intersection of physics, music and neuroscience, collaborating with Hans-Günter Dosch on understanding perception of music and its physiological bases. This transdisciplinary approach produced highly cited publications on the differences in the auditory cortex between musicians and non-musicians, expanding the boundaries of how we understand the brain and its response to music.

Hans was an outstanding teacher, a prolific mentor, a successful science manager, but foremost, he was someone who profoundly loved physics, with a relentless drive to follow wherever his interests and research would lead him. His frequent and spirited commutes between Heidel­berg and CERN in his iconic green Lotus Elan will be fondly remembered. His critical guidance and profound questions will be deeply missed by all who had the privilege of knowing him.

Werner Beusch 1930–2024

Werner Beusch, who played a pioneering role in the OMEGA spectrometer at CERN, passed away after a short illness on 4 May 2024.

A student of Paul Scherrer at ETH Zurich, Werner obtained his PhD in 1960 with a thesis on two-photon transitions in barium-137 and moved to CERN, joining the “Groupe Chambre Wilson” (a collaboration of teams from CERN, ETH Zurich and Imperial College London). Around that time, cloud chambers were being replaced with spark chambers. Werner, already very experienced in electronics despite his young age, designed and built the entire trigger system for spark chambers from scratch using discrete components (NIM modules were not yet available at the time!).

In the late 1960s Werner started working on the OMEGA project – a high-aperture electronic spectrometer to be installed on a PS beam line in the West Area. The spectrometer was envisioned to operate as a facility, with a standard suite of detectors that could be complemented by experiment-specific apparatus provided by the individual collaborations. This was achieved by a large (3 m diameter) superconducting magnet equipped with spark chambers, a triggering system and data acquisition. The original programme included missing-mass experiments, the study of baryon-exchange processes and leptonic hyperon decays, and experiments with hyperon beams and with polarised targets. After a few years, interest moved to new topics, such as photoproduction, charm production and QCD studies.

In 1976 the OMEGA spectrometer was moved to its final position in the West Area on a beam line from the newly built SPS. In 1979, under Werner’s supervision, the spectrometer – until then equipped with spark chambers and plumbicon cameras – was instrumented with the new, much faster and higher resolution multi-wire proportional chambers. The refurbished OMEGA quickly became the go-to facility for a wide range of experiments. Over the years, under Werner’s stewardship, the facility was continuously upgraded with new equipment such as drift chambers, ring-imaging Cherenkov detectors, silicon microstrips and silicon pixel detectors (which were deployed at OMEGA for the first time). Triggering and data acquisition were also continuously updated such that, throughout its 25-year lifetime, OMEGA remained at the forefront of technology. It hosted some 50 experiments, with achievements ranging from its essential role in the establishment of non-qq mesons, to the detection of a (so-far unexplained) excess in the production of soft photons, to the observation of clear violations of factorisation in charm hadroproduction. The OMEGA scientific programme culminated in a key contribution to the discovery of quark–gluon plasma (QGP), with the detection of the signature enhancement pattern of strange and multi-strange hadrons in lead–lead collisions.

Werner retired from CERN in 1995, one year before OMEGA was closed, not because it had reached its time (QGP studies, then in full blossom, had to be hastily moved to the North Area), but to make room for an assembly and test facility for the LHC magnets. Throughout its lifetime, Werner truly was the “soul” of the OMEGA experiment, always present and ready to help. Swapping from one layout to the next (and from one experimental group to the next) was the standard way of operating, and Werner and his team had the heavy responsibility of keeping the spectrometer in good shape and guaranteeing a prompt and efficient restart of the experiments. Werner’s kind and thoughtful attitude was key to this and the many other OMEGA successes. His impassioned, matter-of-fact and selfless way of doing science influenced generations of physicists whose careers were forged at OMEGA. Werner coming into the control room and offering a basket of fruits from his garden remains vivid in the memory. We miss him dearly.

Olav Ullaland 1944–2024

Olav Ullaland

Olav Ullaland, a brilliant detector physicist who spent his career at CERN, passed away on 16 June 2024.

Olav obtained his degree in particle physics at the University of Bergen in 1971. After a short period at Rutherford Appleton Laboratory in the UK, he went to CERN as a fellow in 1973, following which he was awarded a staff contract. He worked as a detector physicist at CERN until he retired in 2009, remaining active for several years as an emeritus. One of his last scientific articles dates from 2020.

Alongside detector R&D, Olav participated in several key CERN experiments. For the Split Field Magnet Detector, located at CERN’s Intersecting Storage Rings, he was in charge of the multi-wire proportional chambers and worked on the prototype of a novel electromagnetic calorimeter that was later adopted by the DELPHI experiment.

After contributing to the UA1 upgrade, he was asked to take a leading role in the complex barrel ring-imaging Cherenkov (RICH) project of DELPHI, which was the first attempt to integrate an imaging Cherenkov detector into a cylindrical collider experiment. The challenges were immense, as it was necessary to operate a gas and liquid radiator, together with a photo­sensitive gas, at different temperatures in a confined space. Thanks to Olav’s perseverance and the loyalty he inspired in his team, he was able to bring the apparatus to a level where it could be used in physics analysis, for example in the tagging of strange jets from Z and W decays. This was a critical milestone in the history of RICH detectors.

Around 1997 Olav joined LHCb and became a leader in the international effort to make its two RICH detectors a reality. Thanks to his deep knowledge of the many facets of detector physics and techniques, and his ability to remain calm, he and his team managed to find solutions to potential showstoppers. It is testament to Olav’s efforts that the particle identification system of LHCb works so impressively in the study of CP violation and heavy-flavour rare decays. In addition, Olav was the LHCb resource coordinator for several years, taking impeccable control of delicate LHCb financial matters at the beginning of the experiment operations. His expertise in leading many project reviews and trouble-shooting several wide-ranging detector subsystems was also in high demand both within and outside LHCb.

Olav was a wonderful collaborator. He was passionate in his support of students and fellows, and encouraged young people to give presentations and international talks, always graciously stepping away from the limelight himself. His dedication to student training was highlighted by his running of the CERN summer student programme, with both lectures and laboratory courses.

For Olav, work did not finish at CERN, but would be continued in any possible meeting place. These unconventional settings provided a conducive atmosphere to explore, discuss and challenge new projects and ideas, with the goal of promoting cohesion in a critical, constructive and friendly fashion.

Olav Ullaland was not only an outstanding researcher, but also a unique human being who left a deep impression on all those with whom he came into contact. We will never forget him.

Arnau Brossa Gonzalo 1993–2024

Arnau Brossa Gonzalo

Arnau Brossa Gonzalo, a postdoctoral researcher at the Galician Institute of High Energy Physics (IGFAE) working on the LHCb experiment, died in Santiago on 21 July 2024 following complications from a climbing accident.

Arnau obtained his degree in physics at the University of Barcelona in 2016, specialising in theoretical physics. He continued there for his master’s in astrophysics, particle physics and cosmology, with a thesis on the LHCb experiment.

In 2017 he embarked on his PhD studies in particle physics at the University of Warwick. His thesis, entitled “First observation of B0 D*(2007)0K+π and B0s D*(2007)0Kπ+ decays in LHCb”, won the Springer Thesis Prize for outstanding PhD research. This was the first LHCb measurement of B decays involving fully reconstructed neutral D*mesons, which are particularly challenging due to the soft neutral particles emitted in the D* Dπ0 and D* Dγ decays. These modes are nonetheless extremely important to understand as they are backgrounds to a wide range of other studies, including those used for precision measurements of the CKM angle γ.

Following the completion of his PhD, Arnau joined the LHCb group at IGFAE in 2022 to work further on the LHCb experiment, first as a postdoctoral researcher and later as a Juan de la Cierva researcher. He then joined the lepton-flavour-universality group at IGFAE, taking on a leading role in the measurement of the ratios of semileptonic-decay branching fractions to final states with tau leptons relative to muons, denoted R(D) and R(D*). Arnau had rapidly established himself as an expert in this area, and in early 2024 he had taken on convenership of the LHCb subgroup that was dedicated to this and to similar charged-current lepton-flavour-universality tests.

Arnau’s warmth, kindness, dedication, intelligence and competence will be deeply missed by his many friends at the institute in Santiago and in the LHCb collaboration.

Robert Aymar 1936-2024

Robert Aymar, CERN Director General from January 2004 to December 2008, passed away on 23 September at the age of 88. An inspirational leader in big-science projects for several decades, including the International Thermonuclear Experimental Reactor (ITER), his term of office at CERN was marked by the completion of construction and the first commissioning of the Large Hadron Collider (LHC). His experience of complex industrial projects proved to be crucial, as the CERN teams had to overcome numerous challenges linked to the LHC’s innovative technologies and their industrial production.

Robert Aymar was educated at Ecole Polytechnique in Paris. He started his career in plasma physics at Commissariat à l’Energie Atomique (CEA), since renamed Commissariat à l’Energie Atomique et aux Energies Alternatives, at the time when thermonuclear fusion was declassified and research started on its application to energy production. After being involved in several studies at CEA, Aymar contributed to the design of the Joint European Torus, the European tokamak project based on conventional magnet technology, built in Culham, UK in the late 1970s. In the same period, CEA was considering a compact tokamak project based on superconducting magnet technology, for which Aymar decided to use pressurised superfluid helium cooling — a technology then recently developed by Gérard Claudet and his team at CEA Grenoble. Aymar was naturally appointed head of the TORE SUPRA tokamak project, built at CEA Cadarache from 1977 to 1988. The successful project served inter alia as an industrial-size demonstrator of superfluid helium cryogenics, which became a key technology of the LHC.

Robert Aymar set out to bring together the physics of the infinitely large and the infinitely small

As head of the Département des Sciences de la Matière at CEA from 1990 to 1994, Robert Aymar set out to bring together the physics of the infinitely large and the infinitely small, as well as the associated instrumentation, in a department that has now become the Institut de Recherche sur les Lois Fondamentales de l’Univers. In that position, he actively supported CEA-CERN collaboration agreements on R&D for the LHC and served on many national and international committees. In 1993 he chaired the LHC external review committee, whose recommendation proved decisive in the project’s approval. From 1994 to 2003, he led the ITER engineering design activities under the auspices of the International Atomic Energy Agency, establishing the basic design and validity of the project that would be approved for construction in 2006. In 2001, the CERN Council called on his expertise once again by entrusting him to chair the external review committee for CERN’s activities.

When Robert Aymar took over as Director General of CERN in 2004, the construction of the LHC was well under way. But there were many industrial and financial challenges, and a few production crises still to overcome. During his tenure, which saw the ramp-up, series production and installation of major components, the machine was completed and the first beams circulated. That first start-up in 2008 was followed by a major technical problem that led to a shutdown lasting several months. But the LHC had demonstrated that it could run, and in 2009 the machine was successfully restarted. Robert Aymar’s term of office also saw a simplification of CERN’s structure and procedures, aimed at making the laboratory more efficient. He also set about reducing costs and secured additional funding to complete the construction and optimise the operation of the LHC. After retirement, he remained active as scientific advisor to the head of the CEA, occasionally visiting CERN and the ITER construction site in Cadarache.

Robert Aymar was a dedicated and demanding leader, with a strong drive and search for pragmatic solutions in the activities he undertook or supervised. CERN and the LHC project own much to his efforts. He was also a man of culture with a marked interest in history. It was a privilege to serve under his direction.

A decider for CERN’s next collider

The third update of the European strategy for particle physics, launched by the CERN Council on 21 March, is getting into its stride. At its June session, the Council elected former ATLAS spokesperson Karl Jakobs (University of Freiburg) as strategy secretary and established a European Strategy Group (ESG), which is responsible for submitting final recommendations to Council for approval in early 2026. The aim of the strategy update, states the ESG remit, is to develop “a visionary and concrete plan that greatly advances human knowledge in fundamental physics through the realisation of the next flagship project at CERN”.

“Given the long timescales involved in building large colliders, it is vital that the community reaches a consensus to enable Council to take a decision on the next collider at CERN in 2027/2028,” Jakobs told the Courier. To reach that consensus it is important that the whole community is involved, he says, emphasising that, compared to previous strategy updates, there will be more opportunities to provide input at different stages. “There is excellent progress with the LHC and no new indication that would change our physics priorities: understanding the Higgs boson much better and exploring further the energy frontier are key to the next project.”

The European strategy for particle physics is the cornerstone of Europe’s decision-making process for the long-term future of the field. It was initiated by the CERN Council in 2005, when completing the LHC was listed as the top scientific priority, and has been updated twice. The first strategy update, adopted in 2013, continued to prioritise the LHC and its high-luminosity upgrade, and stated that Europe needed to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next strategy update. The second strategy update, completed in 2020, recommended an electron–positron Higgs factory as the highest priority, and that a technical and financial feasibility study for a next-generation hadron collider should be pursued in parallel.

Significant progress has been made since then. A feasibility study for the proposed Future Circular Collider (FCC) at CERN presented a mid-term report in March 2024, with a final report expected in spring 2025 (CERN Courier March/April 2024 pp25–38). There is also a clearer view of the international landscape. In December 2023 the US “P5” prioritisation process stated that the US would support a Higgs factory in the form of an FCC-ee at CERN or an International Linear Collider (ILC) in Japan, while also exploring the feasibility of a high-energy muon collider at Fermilab (CERN Courier January/February 2024 p7). Shortly afterwards, a technical design report for the proposed Circular Electron Positron Collider (CEPC) in China was released (CERN Courier March/April 2024 p39). The ILC project has meanwhile established an international technology network in a bid to increase global support.

Alternative scenarios

In addition to identifying the preferred option for the next collider at CERN, the strategy update is expected to prioritise alternative options to be pursued if the chosen preferred plan turns out not to be feasible or competitive. “That we should discuss alternatives to the chosen baseline is important to this strategy update,” says Jakobs. “If the FCC were chosen, for example, a lower-energy hadron collider, a linear collider and a muon collider are among the options that would likely be considered. However, in addition to differences in the physics potential we have to understand the technical feasibility and the timelines. Some of these alternatives may also require an extension of the physics exploitation at the HL-LHC.”

Given the long timescales involved in building large colliders, it is vital that the community reaches a consensus

The third strategy update will also indicate physics areas of priority for exploration complementary to colliders and add other relevant items, including accelerator, detector and computing R&D, theory developments, actions to minimise environmental impact and improve the sustainability of accelerator-based particle physics, initiatives to attract, train and retain early-career researchers, and public engagement.

The particle-physics community is invited to submit written inputs by 31 March 2025 via an online portal that will appear on the strategy secretariat’s web page. This will be followed by a scientific open symposium from 23 to 27 June 2025, where researchers will be invited to debate the future orientation of European particle physics. A “briefing book” based on the input and discussions will then be prepared by the physics preparatory group, the makeup of which was to be established by the Council in September before the Courier went to press. The briefing book will be submitted to the ESG by the end of September 2025 for consideration during a five-day-long drafting session, which is scheduled to take place from 1 to 5 December 2025. To allow the national communities to react to the submissions collected by March 2025 and to the content of the briefing book, they are offered further opportunities for input both ahead of the open symposium (with a deadline of 26 May 2025) and ahead of the drafting session (with a deadline of 14 November 2025). The ESG is expected to submit the proposed strategy update to the CERN Council by the end of January 2026.

“The timing is well chosen because at the end of 2025 we will have a lot of the relevant information, namely the final outcome of the FCC feasibility study plus, on the international scale, an update about what is going to happen in China,” says Jakobs. “The national inputs, whereby national communities are also invited to discuss their priorities, are considered very important and ECFA has produced guidelines to make the input more coherent. Early-career researchers are encouraged to contribute to all submissions, and we have restructured the physics preparatory group such that each working group has a scientific secretary who is an early-career researcher. We look forward to a very fruitful process over the forthcoming one and a half years.”

Voices from a new generation

Seventy years of CERN

In January 1962, CERN was for the first time moving from machine construction to scientific research with the machines. Director-General Victor Weisskopf took up the pen in the first CERN Courier after a brief hiatus. “This institution is remarkable in two ways,” he wrote. “It is a place where the most fantastic experiments are carried out. It is a place where international co-operation actually exists.”

A new generation of early-career researchers (ECRs) shares his convictions. Now, as then, they do much of the heavy lifting that builds the future of the field. Now, as then, they need resilience and vision. As Weisskopf wrote in these pages, the everyday work of high-energy physics (HEP) can hide its real importance – its romantic glory, as the renowned theorist put it. “All our work is for an idealistic aim, for pure science without commercial or any other interests. Our effort is a symbol of what science really means.”

As CERN turns 70, the Courier now hands the pen to the field’s next generation of leaders. All are new post-docs. Each has already made a tangible contribution and earned recognition from their colleagues. All, in short, are among the most recent winners of the four big LHC collaborations’ thesis prizes. Each was offered carte blanche to write about a subject of their choosing, which they believe will be strategically crucial to the future of the field. Almost all responded. These are their viewpoints.

Invest in accelerator innovation

Nicole Hartman

I come from Dallas, Texas, so the Superconducting Super Collider should have been in my backyard as I was growing up. By the late 1990s, its 87 km ring could have delivered 20 TeV per proton beam. The Future Circular Collider could deliver 50 TeV per proton beam in a 91 km ring by the 2070s. I’d be retired before first collisions. Clearly, we need an intermediate-term project to keep expertise in our community. Among the options proposed so far, I’m most excited by linear electron–positron colliders, as they would offer sufficient energy to study the Higgs self-coupling via di-Higgs production. This could be decisive in understanding electroweak symmetry breaking and unveiling possible Higgs portals.

A paradigm shift for accelerators might achieve our physics goals without a collider’s cost scaling with its energy. A strong investment in collider R&D could therefore offer hope for my generation of scientists to push back the energy frontier. Muon colliders avoid synchrotron radiation. Plasma wakefields offer a 100-fold increase in electric field gradient. Though both represent enormous challenges, psychologists have noted an “end of history” phenomenon, whereby as humans we appreciate how much we have changed in the past, but under­estimate how much we will change in the future. Reflecting on the past physics breakthroughs galvanises me to optimism: unlocking the next chapter of physics has always been within the reach of technological innovation. CERN has been a mecca for accelerator applications in the last 70 years. I’d argue that a strong increase in support for novel collider R&D is the best way to carry this legacy forwards.

Nicole Hartman is a post-doc at the Technical University of Munich and Origins Data Science Lab. She was awarded a PhD by Stanford University for her thesis “A search for non-resonant HH  4b at s = 13 TeV with the ATLAS detector – or – 2b, and then another 2b… now that’s the thesis question”.

Reward technical work with career opportunities

Alessandro Scarabotto

This job is a passion and a privilege, and ECRs devote nights and weekends to our research. But this energy should be handled in a more productive way. In particular, technical work on hardware and software is not valued and rewarded as it should be. ECRs who focus on technical aspects are often forced to divide their focus with theoretical work and data analysis, or suffer reduced opportunities to pursue an academic career. Is this correct? Why shouldn’t technical and scientific work be valued in the same way?

I am very hopeful for the future. In recent years, I have seen improvements in this direction, with many supervisors increasingly pushing their students towards technical work. I expect senior leadership to make organisational adjustments to reward and value these two aspects of research in exactly the same way. This cultural shift would greatly benefit our physics community by more efficiently transforming the enthusiasm and hard work of ECRs into skilled contributions to the field that are sustained over the decades.

Alessandro Scarabotto is a postdoctoral researcher at Technische Universität Dortmund. He was awarded a PhD by Sorbonne Université, Paris, for his thesis “Search for rare four-body charm decays with electrons in the final state and long track reconstruction for the LHCb trigger”.

A revolving door to industry

Christopher Brown

Big companies’ energy usage is currently skyrocketing to fuel their artificial intelligence (AI) systems. There is a clear business adaptation of my research on fast, energy-saving AI triggers, but I feel completely unable to make this happen. Why, as a field, are we unable to transfer our research to industry in an effective way?

While there are obvious milestones for taking data to publication, there is no equivalent for starting a business or getting our research into major industry players. Our collaborations are incubators for ideas and people. They should implement dedicated strategies to help ECRs obtain the funding, professional connections and business skills they need to get their ideas into the wider world. We should be presenting at industry conferences – both to offer solutions to industry and to obtain them for our own research – and industry sessions within our own conferences could bring links to every part of our field.

Most importantly, the field should encourage a revolving door between academia and industry to optimise the transfer of knowledge and skills. Unfortunately, when physicists leave for industry, slow, single-track physics career progressions and our focus on publication count rather than skills make a return unrealistic. There also needs to be a way of attracting talent from industry into physics without the requirement of a PhD so that experienced people can start or return to research in high-profile positions suitable for their level of work and life experience.

Christopher Brown is a CERN fellow working on next-generation triggers. He was awarded a PhD by Imperial College London for his thesis “Fast machine learning in the CMS Level-1 trigger for the High-Luminosity LHC”.

Collaboration, retention and support

Prajita Bhattarai

I feel a strong sense of agency regarding the future of our field. The upcoming High-Luminosity LHC (HL-LHC) will provide a wealth of data beyond what the LHC has offered, and we should be extremely excited about the increased discovery potential. Looking further ahead, I share the vision of a future Higgs factory as the next logical step for the field. The proposed Future Circular Collider is currently the most feasible option. However, the high cost and evolving geopolitical landscape are causes for concern. One of the greatest challenges we face is retaining talent and expertise. In the US, it has become increasingly difficult for researchers to find permanent positions after completing postdocs, leading to a loss of valuable technical and operational expertise. On a positive note, our field has made significant strides in providing opportunities for students from under­represented nationalities and socioeconomic backgrounds – I am a beneficiary of these efforts. Still, I believe we should intensify our focus on supporting individuals as they transition through different career stages to ensure a vibrant and diverse future workforce.

Prajita Bhattarai is a research associate at SLAC National Accelerator Laboratory in the US. She was awarded her PhD by Brandeis University in the US for her thesis “Standard Model electroweak precision measurements with two Z bosons and two jets in ATLAS”.

Redesign collaborations for equitable opportunity

Spandan Mondal

Particle physics and cosmology capture the attention of nearly every inquisitive child. Though large collaborations and expensive machines have produced some of humankind’s most spectacular achievements, they have also made the field inaccessible to many young students. Making a meaningful contribution is contingent upon being associated with an institution or university that is a member of an experimental collaboration. One typically also has to study in a country that has a cooperation agreement with an international organisation like CERN.

If future experiments want to attract diverse talent, they should consider new collaborative models that allow participation irrespective of a person’s institution or country of origin. Scientific and financial responsibilities could be defined based on expertise and the research grants of individual research groups. Remote operations centres across the globe, such as those trialled by CERN experiments, could enable participants to fulfil their responsibilities without being constrained by international borders and travel budgets; the worldwide revolution in connectivity infrastructure could provide an opportunity to make this the norm rather than the exception. These measures could provide equitable opportunities to everyone while simultaneously maximising the scientific output of our field.

Spandan Mondal is a postdoctoral fellow at Brown University in the US. He was awarded a PhD by RWTH Aachen in Germany for his thesis on the CMS experiment “Charming decays of the Higgs, Z, and W bosons: development and deployment of a new calibration method for charm jet identification”.

Reward risk taking

Francesca Ercolessi

Young scientists often navigate complex career paths, where the pressure to produce consistent publishable results can stifle creativity and discourage risk taking. Traditionally, young researchers are evaluated almost solely on achieved results, often leading to a culture of risk aversion. To foster a culture of innovation we must shift our approach to research and evaluation. To encourage bold and innovative thinking among ECRs, the fuel of scientific progress, we need to broaden our definition of success. European funding and grants have made strides in recognising innovative ideas, but more is needed. Mentorship and peer-review systems must also evolve, creating an environment open to innovative thinking, with a calculated approach to risk, guided by experienced scientists. Concrete actions include establishing mentorship programmes during scientific events, such as workshops and conferences. To maximise the impact, these programmes should prioritise diversity among mentors and mentees, ensuring that a wide range of perspectives and experiences are shared. Equally important is recognising and rewarding innovation. This can be achieved by dedicated awards that value originality and potential impact over guaranteed success. Celebrating attempts, even failed ones, can shift the focus from the outcome to the process of discovery, inspiring a new generation of scientists to push the boundaries of knowledge.

Francesca Ercolessi is a post-doc at the University of Bologna. She was awarded a PhD by the University of Bologna for her thesis “The interplay of multiplicity and effective energy for (multi) strange hadron production in pp collisions at the LHC”.

Our employment model stifles creativity

Florian Jonas

ECR colleagues are deeply passionate about the science they do and wish to pursue a career in our field – “if possible”. Is there anything one can do to better support this new generation of physicists? In my opinion, we have to address the scarcity of permanent positions in our field. Short-term contracts lead to risk aversion, and short-term projects with a high chance of publication increase your employment prospects. This is in direct contrast to what is needed to successfully complete ambitious future projects this century – projects that require innovation and out-of-the-box thinking by bright young minds.

In addition, employment in fundamental science is more than ever in direct competition with permanent jobs in industry. For example, machine learning and computing experts innovate our field with novel analysis techniques, but end up ultimately leaving our field to apply their skills in permanent employment elsewhere. If we want to keep talent in our field we must create a funding structure that allows realistic prospects for long-term employment and commitment to future projects.

Florian Jonas is a postdoctoral scholar at UC Berkeley and LBNL. He was awarded a PhD by the University of Münster for his thesis on the ALICE experiment “Probing the initial state of heavy-ion collisions with isolated prompt photons”.

Embrace private expertise and investment

Jona Motta

The two great challenges of our time are data taking and data analysis. Rare processes like the production of Higgs-boson pairs have cross sections 10 orders of magnitude smaller than their backgrounds – and during HL-LHC operation the CMS trigger will have to analyse about 50 TB/s and take decisions with a latency of 12.5 μs. In recent years, we have made big steps forward with machine learning, but our techniques are not always up to speed with the current state-of-the-art in the private sector.

To sustain and accelerate our progress, the HEP community must be more open to new sources of funding, particularly from private investments. Collaborations with tech companies and private investors can provide not only financial support but also access to advanced technologies and expertise. Encouraging CERN–private partnerships can lead to the development of innovative tools and infrastructure, driving the field forward.

The recent establishment of the Next Generation Trigger Project, funded by the Eric and Wendy Schmidt Fund for Strategic Innovation, represents the first step toward this kind of collaboration. Thanks to overlapping R&D interests, this could be scaled up to direct partnerships with companies to introduce large and sustained streams of funds. This would not only push the boundaries of our knowledge but also inspire and support the next generation of physicists, opening new tenured positions thanks to private funding.

Jona Motta is a post-doc at Universität Zürich. He was awarded a PhD by Institut Polytechnique de Paris for his thesis “Development of machine learning based τ trigger algorithms and search for Higgs boson pair production in the bbττ decay channel with the CMS detector at the LHC”.

Stability would stop the brain drain

Hassnae El Jarrari

The proposed Future Circular Collider presents a formidable challenge. Every aspect of its design, construction, commissioning and operations would require extensive R&D to achieve the needed performance and stability, and fully exploit the machine’s potential. The vast experience acquired at the LHC will play a significant role. Knowledge must be preserved and transmitted between generations. But the loss of expertise is already a significant problem at the LHC.

The main reason for young scientists to leave the field is the lack of institutional support: it’s hard to count on a stable working environment, regardless of our expertise and performance. The difficulty in finding permanent academic or research positions and the lack of recognition and advancement are all viewed as serious obstacles to pursuing a career in HEP. In these conditions, a young physicist might find competitive sectors such as industry or finance more appealing given the highly stable future they offer.

It is crucial to address this problem now for the HL-LHC. Large HEP collaborations should be more supportive to ensure better recognition and career advancement towards permanent positions. This kind of policy could help to retain young physicists and ensure they continue to be involved in the current HEP projects that would then define the success of the FCC.

Hassnae El Jarrari is a CERN research fellow in experimental physics. She was awarded a PhD by Université Mohammed-V De Rabat for her thesis “Dark photon searches from Higgs boson and heavy boson decays using pp collisions recorded at s = 13 TeV with the ATLAS detector at the LHC and performance evaluation of the low gain avalanche detectors for the HL-LHC ATLAS high-granularity timing detector”.

Reduce environmental impacts

Luca Quaglia

The main challenge for the future of large-scale HEP experiments is reducing our environmental impact, and raising awareness is key to this. For example, before running a job, the ALICE computing grid provides an estimate of its CO2-equivalent carbon footprint, to encourage code optimisation and save power.

I believe that if we want to thrive in the future, we should adopt a new way of doing physics where we think critically about the environment. We should participate in more collaboration meetings and conferences remotely, and promote local conferences that are reachable by train.

I’m not saying that we should ban air travel tout court. It’s especially important for early-career scientists to get their name out there and to establish connections. But by attending just one major international conference in person every two years, and publicising alternative means of communication, we can save resources and travel time, which can be invested in our home institutions. This would also enable scientists from smaller groups with reduced travel budgets to attend more conferences and disseminate their findings.

Luca Quaglia is a postdoctoral fellow at the Istituto Nazionale di Fisica Nucleare, Sezione di Torino. He was awarded his PhD by the University of Torino for his thesis “Development of eco-friendly gas mixtures for resistive plate chambers”.

Invest in software and computing talent

Joshua Beirer

With both computing and human resources in short supply, funds must be invested wisely. While scaling up infrastructure is critical and often seems like the simplest remedy, the human factor is often overlooked. Innovative ideas and efficient software solutions require investment in training and the recruitment of skilled researchers.

This investment must start with a stronger integration of software education into physics degrees. As the boundaries between physics and computer science blur, universities must provide a solid foundation, raise awareness of the importance of software in HEP and physics in general, and promote best practices to equip the next generation for the challenges of the future. Continuous learning must be actively supported, and young researchers must be provided with sufficient resources and appropriate mentoring from experienced colleagues.

Software skills remain in high demand in industry, where financial incentives and better prospects often attract skilled people from academia. It is in the interest of the community to retain top talent by creating more attractive and secure career paths. After all, a continuous drain of talent and knowledge is detrimental to the field, hinders the development of efficient software and computing solutions, and is likely to prove more costly in the long run.

Joshua Beirer is a CERN research fellow in the offline software group of the ATLAS experiment and part of the lab’s strategic R&D programme on technologies for future experiments. He was awarded his PhD by the University of Göttingen for his thesis “Novel approaches to the fast simulation of the ATLAS calorimeter and performance studies of track-assisted reclustered jets for searches for resonant X  SH  bbWW* production with the ATLAS detector”.

Strengthen international science

Ezra D. Lesser

HEP is at an exciting yet critical inflection point. The coming years hold both unparalleled opportunities and growing challenges, including an expanding arena of international competition and the persistent issue of funding and resource allocation. In a swiftly evolving digital age, scientists must rededicate themselves to public service, engagement and education, informing diverse communities about the possible technological advancements of HEP research, and sharing with the world the excitement of discovering fundamental knowledge of the universe. Collaborations must be strengthened across international borders and political lines, pooling resources from multiple countries to traverse cultural gaps and open the doors of scientific diplomacy. With ever-increasing expenses and an uncertain political future, scientists must insist upon the importance of public research irrespective of any national agenda, and reinforce scientific veracity in a rapidly evolving world that is challenged by growing misinformation. Most importantly, the community must establish global priorities in a maturing age of precision, elevating not only new discoveries but the necessary scientific repetition to better understand what we discover.

The most difficult issues facing HEP research today are addressable and furthermore offer excellent opportunities to develop the scientific approach for the next several decades. By tackling these issues now, scientists can continue to focus on the mysteries of the universe, driving scientific and technological advancements for the betterment of all.

Ezra D. Lesser is a CERN research fellow working with the LHCb collaboration. He was awarded his PhD in physics by the University of California, Berkeley for his thesis: Measurements of jet substructure in pp and Pb–Pb collisions at sNN = 5.02 TeV with ALICE”.

Recognise R&D

Savannah Clawson

ECRs must drive the field’s direction by engaging in prospect studies for future experiments, but dedicating time to this essential work comes at the expense of analysing existing data – a trade-off that can jeopardise our careers. With most ECRs employed on precarious two-to-four year contracts, time spent on these studies can result in fewer high-profile publications, making it harder to secure our next academic position. Another important factor is the unprecedented timescales associated with many prospective futures. Those working on R&D today may never see the fruits of their labour.

Anxieties surrounding these issues are often misinterpreted as disengagement, but nothing could be further from the truth. In my experience, ECRs are passionate about research, bringing fresh perspectives and ideas that are crucial for advancing the field. However, we often struggle with institutional structures that fail to recognise the breadth of our contributions. By addressing longstanding issues surrounding attitudes toward work–life balance and long-term job stability – through measures such as establishing enforced minimum contract durations, as well as providing more transparent and diverse sets of criteria for transitioning to permanent positions – we can create a more supportive environment where HEP thrives, driven by the creativity and innovation of its next generation of leaders.

Savannah Clawson is a postdoctoral fellow at DESY Hamburg. She was awarded her PhD by the University of Manchester for her thesis “The light at the end of the tunnel gets weaker: observation and measurement of photon-induced W+W production at the ATLAS experiment”.

Steering the ship of member states

CERN turns 70 at the end of September. How would you sum up the contribution the laboratory has made to human culture over the past seven decades?

CERN’s experimental and theoretical research laid many of the building blocks of one of the most successful and impactful scientific theories in human history: the Standard Model of particle physics. Its contributions go beyond the best-known discoveries, such as of neutral currents and the seemingly fundamental W, Z and Higgs bosons, which have such far-reaching significance for our universe. I also wish to draw attention to the many dozens of new composite particles at the LHC and the incredibly high-precision agreement between theoretical calculation performed in quantum chromodynamics and the experimental results obtained at the LHC. These amazing discovering were made possible thanks to the many technological innovations made at CERN.

But knowledge creation and accumulation are only half the story. CERN’s human ecosystem is an oasis in which the words “collaboration among peoples for the good of humanity” can be uttered without grandstanding or hypocrisy.

What role does the CERN Council play?

CERN’s member states are each represented by two delegates to the CERN Council. Decisions are made democratically, with equal voting power for each national delegation. According to the convention approved in 1954, and last revised in 1971, Council determines scientific, technical and administrative policy, approves CERN’s programmes of activities, reviews its expenditures and approves the laboratory’s budget. The Director-General and her management team work closely with Council to develop the Organization’s policies, scientific activities and budget. Director-General Fabiola Gianotti and her management team are now collaborating with Council to forge CERN’s future scientific vision.

What’s your vision for CERN’s future?

As CERN Council president, I have a responsibility to be neutral and reflect the collective will of the member states. In early 2022, when I took up the presidency, Council delegates unanimously endorsed my evaluation of their vision: that CERN should continue to offer the world’s best experimental high-energy physics programme using the best technology possible. CERN now needs to successfully complete the High-Luminosity LHC (HL-LHC) project and agree on a future flagship project.

I strongly believe the format of the future flagship project needs to crystallise as soon as possible. As put to me recently in a letter from the ECFA early-career researchers panel: “While the HL-LHC constitutes a much-anticipated and necessary advance in the LHC programme, a clear path beyond it for our future in the field must be cemented with as little delay as possible.” It can be daunting for young people to speak out on strategy and the future of the field, given the career insecurities they face. I am very encouraged by their willingness to put out a statement calling for immediate action.

At its March 2024 session, Council agreed to ignite the process of selecting the next flagship project by going ahead with the fourth European Strategy for Particle Physics update. The strategy group are charged, among other things, with recommending what this flagship project should be to Council. As I laid down the gavel concluding the meeting I looked around and sensed genuine excitement in the Chambers – that of a passenger ship leaving port. Each passenger has their own vision for the future. Each is looking forward to seeing what the final destination will look like. Several big pieces had started falling into place, allowing us to turn on the engine.

What are these big pieces?

Acting upon the recommendation of the 2020 update of the European Strategy for Particle Physics, CERN in 2021 launched a technical and financial feasibility study for a Future Circular Collider (FCC) operating first as a Higgs, electroweak and top factory, with an eye to succeeding it with a high-energy proton–proton collider. The report will include the physics motivation, technological and geological feasibility, territorial implementation, financial aspects, and the environmental and sustainability challenges that are deeply important to CERN’s member states and the diverse communes of our host countries.

Fabiola Gianotti and Eliezer Rabinovici at CERN Council

It is also important to add that CERN has also invested, and continues to invest, in R&D for alternatives to FCC such as CLIC and the muon collider. CLIC is a mature design, developed over decades, which has already precipitated numerous impactful societal applications in industry and medicine; and to the best of my knowledge, at present no laboratory has invested as much as CERN in muon-collider R&D.

A mid-term report of FCC’s feasibility study was submitted to subordinate bodies to the CERN management mid-2023, and their resulting reports were presented to CERN’s finance and scientific-policy committees. Council received the outcomes with great appreciation for the work involved during an extraordinary session on 2 February, and looks forward to the completion of the feasibility study in March 2025. Timing the European strategy update to follow hot on its heels and use it as an input was the natural next step.

At the June Council session, we started dealing with the nitty gritty of the process. A secretariat for the European Strategy Group was established under the chairmanship of Karl Jakobs, and committees are being appointed. By January 2026 the Council could have at its disposal a large part of the knowledge needed to chart the future of the CERN vision.

How would you encourage early-career researchers (ECRs) to engage with the strategy process?

ECRs have a central role to play. One of the biggest challenges when attempting to build a major novel research infrastructure such as the proposed FCC – which I sometimes think of as a frontier circular collider – is to maintain high-quality expertise, enthusiasm and optimism for long periods in the face of what seem like insurmountable hurdles. Historically, the physicists who brought a new machine to fruition knew that they would get a chance to work on the data it produced or at least have a claim for credit for their efforts. This is not the case now. Success rests on the enthusiasm of those who are at the beginning of their careers today just as much as senior researchers. I hope ECRs will rise to the challenge and find ways to participate in the coming European Strategy Group-sponsored deliberations and become future leaders of the field. One way to engage is to participate in ECR-only strategy sessions like those held at the yearly FCC weeks. I’d also encourage other countries to join the UK in organising nationwide ECR-only forums for debating the future of the field, such as I initiated in Birmingham in 2022.

What’s the outlook for collaboration and competition between CERN and other regions on the future collider programme?

Over decades, CERN has managed to place itself as the leading example of true international scientific collaboration. For example, by far the largest national contingent of CERN users hails from the US. Estonia has completed the process of joining CERN as a new member state and Brazil has just become the first American associate member state. There is a global agreement among scientists in China, Europe, Japan and the US that the next collider should be an electron–positron Higgs factory, able to study the properties of the Higgs boson with high precision. I hope that – patiently, and step by step – ever more global integration will form.

Do member states receive a strong return on their investment in CERN?

Research suggests that fundamental exploration actively stimulates the economy, and more than pays for itself. Member states and associate member states have steadfastly supported CERN to the tune of CHF 53 billion (unadjusted for inflation) since 1954. They do this because their citizens take pride that their nation stands with fellow member states at the forefront of scientific excellence in the fundamental exploration of our universe. They also do this because they know that scientific excellence stimulates their economies through industrial innovation and the waves of highly skilled engineers, entrepreneurs and scientists who return home trained, inspired and better connected after interacting with CERN.

A bipartisan US report from 2005 called “Rising above the gathering storm” offered particular clarity, in my opinion. It asserted that investments in science and technology benefit the world’s economy, and it noted both the abruptness with which a lead in science and technology can be lost and the difficulty of recovering such a lead. One should not be shy to say that when CERN was established in 1954, it was part of a rather crowded third place in the field of experimental particle physics, with the Soviet Union and the United States at the fore. In 2024, CERN is the leader of the field – and with leadership comes a heavy responsibility to chart a path beneficial to a large community across the whole planet. As CERN Council president, I thank member states for their steadfast support and I applaud them for their economic and scientific foresight over the past seven decades. I hope it will persist long into the 21st century.

Is there a role for private funding for fundamental research?

In Europe, substantial private-sector support for knowledge creation and creativity dates back at least to the Medici. Though it is arguably less emphasised in our times, it plays an important role today in the US, the UK and Israel. Academic freedom is a sine qua non for worthwhile research. Within this limit, I don’t believe there is any serious controversy in Council on this matter. My sense is that Council fully supports the clear division between recognising generosity and keeping full academic and governance freedom.

What challenges has Council faced during your tenure as president?

In February 2022, the Russian Federation, an observer state, invaded Ukraine, which has been an associate member state since 2016. This was a situation with no precedent for Council. The shape of our decisions evolved for well over a year. Council members decided to cover from their own budgets the share of Ukraine’s contribution to CERN. Council also tried to address as much as possible the human issues resulting from the situation. It decided to suspend the observer status in the Council of the Russian Federation and the Joint Institute for Nuclear Research. Council also decided to not extend its International Collaboration Agreements with the Republic of Belarus and the Russian Federation. CERN departments also undertook initiatives to support the Ukrainian scientific community at CERN and in Ukraine.

A second major challenge was to mitigate the financial pressures being experienced around the world, such as inflation and rising costs for energy and materials. A package deal was agreed upon in Council that included significant contributions from the member states, a contribution from the CERN staff, and substantial savings from across CERN’s activities. So far, these measures seem to have addressed the issue.

I thank member states for their steadfast support and I applaud them for their economic and scientific foresight over the past seven decades

While these key challenges were tackled, management worked relentlessly on preparing an exhaustive FCC feasibility study, to ensure that CERN stays on course in developing its scientific and technological vision for the field of experimental high-energy physics.

The supportive reaction of Council to these challenges demonstrated its ability to stay on course during rough seas and strong side winds. This cohesion is very encouraging for me. Time and again, Council faced difficult decisions in recent years. Though convergence seemed difficult at first, thanks to a united will and the help of all Council members, a way forward emerged and decisions were taken. It’s important to bear in mind that no matter which flagship project CERN embarks on, it will be a project of another order of magnitude. Some of the methods that made the LHC such a success can continue to accompany us, some will need to evolve significantly, and some new ones will need to be created.

Has the ideal of Science for Peace been damaged?

Over the years CERN has developed the skills needed to construct bridges. CERN does not have much experience in dismantling bridges. This issue was very much on the mind of Council as it took its decisions.

Do you wish to make some unofficial personal remarks?

Thanks. Yes. I would like to mention several things I feel grateful for.

Nobody owes humanity a concise description of the laws of physics and the basic constituents of matter. I am grateful for being in an era where it seems possible, thanks to a large extent to the experiments performed at CERN. Scientists from innumerable countries, who can’t even form a consensus on the best 1970s rock band, have succeeded time and again to assemble the most sophisticated pieces of equipment, with each part built in a different country. And it works. I stand in awe in front of that.

The ecosystem of CERN, the experimental groups working at CERN and the CERN Council are how I dreamt as a child that the United Nations would work. The challenges facing humanity in the coming centuries are formidable. They require international collaboration among the best minds from all over the planet. CERN shows that this is possible. But it requires hard work to maintain this environment. Over the years serious challenges have presented themselves, and one should not take this situation for granted. We need to be vigilant to keep this precious space – the precious gift of CERN.

German community discusses future collider at CERN

German particle-physics community in Bonn

More than 150 German particle physicists gathered at Bonn University for a community event on a future collider at CERN. More precisely, the focus set for this meeting was to discuss the opportunities that the FCC-ee would offer should this collider be built at CERN. The event was organised by the German committee for particle physics, KET, and took place from 22 to 24 May. Representatives from almost all German institutes and groups active in particle physics were present, an attendance that shows the large interest in the collider to be built at CERN after the successful completion of the HL-LHC programme.

The main workshop was preceded by a dedicated session with more than 80 early-career scientists, organised by the Young High Energy Physicists Association, yHEP, to bring the generation that will benefit most from a future collider at CERN up to speed on the workshop topics. It included a presentation by former ECFA chair Karl Jakobs (Freiburg University) “From Strategy Discussions to Decision-Taking for Large Projects”, explaining the mechanisms and bodies involved in setting a project like the FCC-ee on track.

The opening session of the main workshop featured a fresh view on “The physics case for an e+e collider at CERN” by Margarete Mühlleitner (KIT Karlsruhe), who spread excitement about the strong and comprehensive physics case from super-precise measurements of the properties of the Z boson, the W boson and the top quark to what most people associate with a future e+e collider: precision measurements of the Higgs boson and insights about its connection to many of the still open questions of particle physics like dark matter or the matter–antimatter asymmetry. Markus Klute (KIT Karlsruhe) gave an in-depth review of the FCC-ee project. The midterm results of the FCC feasibility study indicate that no showstoppers were found in all the aspects studied so far and that the integrated FCC programme offers unparalleled exploration potential through precision measurements and direct searches. The picture was rounded off by a presentation from Jenny List (DESY, Hamburg) who talked about alternative options to realise an e+e Higgs factory at CERN, and the perspective of the early-career researchers was highlighted by Michael Lupberger (Bonn University). While all these presentations concentrated on the science and technology of the FCC-ee or alternatives, Eckart Lilienthal, representing the German Ministry of Education and Research, BMBF, reminded the audience that a future collider project at CERN needs an affordable financial plan and that – given the large uncertainties at present – this requires the community to prepare for different scenarios including one without the FCC-ee. Lilienthal confirmed that the future of CERN remains of the highest priority to BMBF.

The event was an important step in building consensus in the German community for a future collider project at CERN

The workshop went on to review many aspects of the FCC-ee and possible alternatives in more detail: accelerator R&D, detector concepts and technologies, computing and software, theory challenges as well as sustainability. The workshop witnessed the first meetings of the newly established German detector R&D consortia on silicon detectors, gaseous detectors and calorimetry. They will receive BMBF funding for the next three years and will allow German groups to strongly participate in the recently formed international DRD consortia in the context of the ECFA detector roadmap.

The path ahead

The workshop concluded with discussion sessions on the future collider scenarios for CERN, the engagement of the German community and a path to prepare the German input to the update of the European Strategy for Particle Physics. A series of three additional community workshops will be held in Germany before this input is due in March 2025.

The Bonn event was an important step in building consensus in the German community for a future collider project at CERN. The FCC-ee project generated a lot of interest and many groups plan to embark more strongly on this project. Contributions concerning the physics case, theory challenges, detector design and development, software, computing, and accelerator development were discussed. Alternative options for a future collider project at CERN need to be kept open to address the unanswered fundamental questions of particle physics in case the FCC-ee is not built at CERN. This event was clear evidence that a bright future for CERN remains of highest priority for the German particle-physics community and funding agency.

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