“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.
This year, SLAC celebrates its remarkable past while continuing its quest for a bright future. This presentation takes a look at how it all started with the lab’s two-mile-long linear accelerator and accompanying groundbreaking discoveries in particle physics; explores how the lab’s scientific mission has evolved over time to include many disciplines ranging from X-ray science to cosmology; and discusses the most exciting perspectives for future research, from developing new quantum technology to pushing the frontiers of our understanding of the universe on its largest scales.
JoAnne Hewett is a world-class theoretical physicist with well over 100 publications in theoretical high-energy physics. Her research probes the fundamental nature of space, matter and energy, where she most enjoys devising experimental tests for preposterous theoretical ideas. She is best known for her work on the possible existence of extra spatial dimensions. She has twice been a member of the HEPAP advisory panel and made major contribution to the recent Particle Physics Project Prioritization Panel (“P5”) plan, which defines US high-energy physics research priorities for the next 10 years.
Since joining the SLAC faculty in 1994, JoAnne has served in key leadership roles here at SLAC, including head of the theoretical physics group, deputy director of the Science Directorate and Director of SLAC’s Elementary Particle Physics (EPP) Division. During her tenure as EPP Division director, JoAnne aligned the program with the highest P5 priorities by establishing a neutrino theory program and extending SLAC’s experimental efforts work in accelerator-based neutrino physics and neutrinoless double-beta decay. She was elected a fellow of the American Physical Society in 2008 and named a fellow of the American Association for the Advancement of Science in 2009, and served as chair of the American Physical Society’s Division of Particles & Fields in 2016.
The worldwide interest in axions and other weakly interacting slim particles (WISPs) as constituents of a dark sector of nature has strongly increased over the last years. A vibrant community is developing, constructing and operating corresponding experiments, so that most promising parameter regions will be probed within the next 15 years.
Many of these approaches rely on WISPs converting to photons. At DESY in Hamburg, larger-scale projects are pursued: the “light-shining-through-a-wall” experiment, ALPS II in the HERA tunnel, will start data taking soon. The solar helioscope BabyIAXO is nearly ready to start construction, while the dark matter haloscope MADMAX is in the prototyping phase.
This webinar will introduce the physics cases and focus on the axion search activities ongoing at DESY.
Axel Lindner was working in accelerator-based particle physics, astroparticle physics and management before he engaged in WISP searches in 2007 as the spokesperson of the ALPS I experiment. Since 2018 he has been leading a new experimental group at DESY in Hamburg in charge of realizing non-accelerator-based particle physics experiments on-site. Axel has been a member of the MADMAX and IAXO collaborations and spokesperson of ALPS II since 2012.
The 2022 edition of the yearly workshop “Implications of LHCb measurements and future prospects” from 19 to 21 October at CERN was already the 12th instance in a series of meetings between LHCb and the theory community. The large attendance, with 294 people registered, reflects the excitement of both the experimental and theory community for the physics case of LHCb. In several plenary streams the newest experimental and theoretical developments were presented in mixing and CP violation, flavour changing neutral and charged currents, QCD spectroscopy and exotic hadrons, electroweak physics (now yearly rotating with the stream on fixed target and heavy ion physics) as well as in the newly established stream on model building for flavour physics. The workshop was preceded by “Theory Lectures” about CP violation. This is a new initiative that will henceforth be held yearly in conjunction with the Implications Workshop on various topics of interest.
The conference opened with an overview of the LHCb experiment, where the first milestones of the Upgrade I commissioning were presented. The new fully software trigger scheme of LHCb, with the highest data processing scheme of any LHC experiment, has been successfully implemented for the full LHCb detector.
The hot-off-the-press result on the simultaneous determination of the ratios R(D*)= BR(B→D*τ–ντ)/BR(B→D*μ–νμ) and R(D)= BR(B–→D0τ–ντ)/BR(B–→D0μ–νμ) was shown. This result, which superseded the previous LHCb measurement, is 1.9 σ away from the Standard Model (SM) expectation. Another highlight was the first observation of the decay Λ0b→Λ+cτ–ντ, and its use to test lepton flavour universality using the ratio of the tauonic to muonic decay, R(Λ+c), which is yet in agreement with the SM. The newest precision extractions of the moduli of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |Vcb| and |Vub| were discussed, showing that the long-standing puzzle of inclusive versus exclusive measurements keeps being a hot topic with many upcoming developments in the near future.
Within the mixing and CP violation (CPV) stream, a major highlight was the measurement of the time-integrated CP asymmetry in Do→K+K– decays, leading to the first determination of the direct CP asymmetries in both Do→K+K– and Do→π+π– in the latter case constituting the first evidence for CPV in a single charm decay. These results led to exciting discussions about the size of U-spin breaking and possible underlying mechanisms. A new theoretical methodology for the derivation of amplitude U-spin sum rules was presented, making sum rules feasible for any system at any order in the expansion in the symmetry-breaking terms.
Further major results were the determination of the charm mixing parameters
yCP-yKπCP, very large local CP asymmetries seen in B+→h+h’– h’+ (with h,h’=π,K), as well as a new simultaneous determination of the weak phase γ together with charm mixing and decay parameters. On the theory side, it was also presented the completion of the next-to-next-to-leading order (NNLO) QCD calculation of the width difference of Bos mesons, allowing for an improved comparison with the corresponding experimental results.
The versatility of LHCb was showcased by covering rare beauty, kaon and charm decays, along with new tests on lepton-flavor universality violation
The rare decays session again showcased the versatility of LHCb by covering rare beauty, kaon and charm decays, including the most recent results on lepton-flavor universality violation. Recent progress on handling QCD corrections of b→sℓ+ℓ–, which are important for the interpretation of the B anomalies, were presented, and it was shown a new method for the extraction of CKM matrix elements using time-dependent kaon decays. Lots of future opportunities lie in the measurements of rare charmed baryon decays which are very little probed so far.
New exciting results were shown in the spectroscopy stream, where one new pentaquark and three new tetraquark states were presented, showing the leading contribution of LHCb to the discovery of exotics and yet-not-understood states. Progress on QCD predictions along with new data-driven and machine-learning based methods were discussed.
The BSM session gave a great overview of a diverse range of beyond-the-SM models including leptoquarks, Z’ models, axion-like particles (ALPs) as well as models with extra dimensions. Importantly, these models induce correlations between the B anomalies and other anomalies like g-2 or the Cabibbo angle anomaly. Complementary and partially competitive constraints on the viable model space come from direct searches and high-pT observables.
Interesting discussions took place in the electroweak precision-measurements session, where the LHCb W-boson mass measurement was presented, which is in line with the world average and in tension with the recent precise CDF measurement at the 4σ level. This measurement will soon be complemented with the full Run 2 dataset.
The workshop closed with a grand overview given in the keynote talk by Alexander Lenz. The next instance of the Implications Workshop will take place at CERN in October 2023.
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.
The Superconducting Detector Magnets Workshop, co-organised by CERN and KEK, was held at CERN from 12 to 14 September in a hybrid format. Joining were 90 participants from 36 different institutes and companies, with 57 on-site and 33 taking part remotely.
The workshop aimed to bring together the physics community, detector magnet designers and industry to exchange ideas and concepts, foster collaboration, and to discuss the needs and R&D development goals for future superconducting detector magnets. A key goal was to address the issue of the commercial availability of aluminium-stabilised Nb-Ti/Cu conductor technology.
Fifteen physics-experiment projects, which had either been approved or are in the design phase, presented their needs and plans for superconducting detector magnets. These experiments covered a wide range of physics programmes for existing and future colliders, non-colliders and a space-based experiment. The presented projects showed a strong demand for aluminium-stabilised Nb-Ti/Cu conductor technology. Other conductor technologies that were featured during the workshop included cable-in-conduit technology (CICC) and aluminium-stabilised high-temperature-superconducting (HTS) technology.
Presentations by leading industrial partners showed that the industrial capability to produce superconducting detector magnets does exist, as long as a suitable conductor is available. It was also shown that aluminium-stabilised Nb-Ti/Cu conductors are currently not commercially available, although an R&D effort is currently on-going with IHEP in China. In particular, the co-extrusion process needed to clad the Nb-Ti/Cu Rutherford cable with aluminium is a key missing ingredient in industry. At the same time, the presentations showed that other ingredients, such as Nb-Ti/Cu wire production, the cabling of strands into a Rutherford cable, the high-purity aluminium stabiliser itself and the technique for welding-on of aluminium-alloy reinforcements for high-strength conductors, are still available.
The main conclusion of the workshop was that, given the need for aluminium-stabilised Nb-Ti/Cu conductors for future superconducting detector magnet projects, it is important that the commercial availability of this conductor is re-established, which would require a leading effort from international institutes through collaboration and cooperation with industry. This world-leading effort will advance technologies to be transferred openly to industry and other laboratories. Of particular importance is the co-extrusion technology needed to bond the aluminium stabiliser to the Rutherford cable. Hybrid-structure technology through electron- beam welding or other approaches to maximise the performance of an Al-stabilised superconductor combined with high-strength Al-alloy is needed for high-stress detector magnets. Back-up solutions such as copper-coated and soldered aluminium stabilisers, copper-based stabilisers and CICC should also be considered. In the long term, aluminium-stabilised HTS technology will be important for specific detector-magnet applications.
The workshop was received with strong interest and enthusiasm, and it is expected that another will be organised in one to two years, depending on the progress being made.
The FCC-ee, a proposed 91 km future circular collider at CERN foreseen to begin operations in the 2040s, would deliver enormous samples of collision data at a wide range of energies, allowing for ultra-precise studies of the Higgs, W and Z bosons, and the top quark. For example, when running at the Z resonance the FCC-ee will produce – in little more than one minute – a data set the same size as that the LEP collider accumulated in the 1990s during its entire period of operation. For this reason, unlocking the full potential of FCC-ee data will require exquisite systematic control at a level far beyond that achieved at previous colliders.
A beautiful and unique attribute of circular e+e– colliders is that the beams can naturally acquire transverse polarisation, and the precession frequency of the polarisation vector divided by the circulation frequency around the ring is directly proportional to the beam energy. This property allows the energy to be determined with very high precision through applying an oscillating magnetic field which, when in phase with the precession, depolarises the beams. This technique of resonant depolarisation underpins the precise knowledge of the mass and other properties of many particles that now serve as “standard candles”.
A key example is the measurement of the mass and width of the Z boson, and associated electroweak observables, which was the major achievement of the LEP programme. FCC-ee offers the possibility of improving the precision of these measurements by a factor of around 500 – a gigantic advance in precision that will allow for ultra-sensitive tests of the self-consistency of the Standard Model, and provide excellent sensitivity to new heavy particles that may affect the measurements through quantum corrections or mixing. Achieving the best possible knowledge of the collision energy is essential to accomplish this programme, and was the focus of the second FCC Energy Calibration, Polarization and Mono-chromatisation (EPOL) workshop held at CERN from 19 to 30 September, which was a follow-up to the first workshop that took place in 2017.
The two-week workshop was attended by more than 100 accelerator physicists, particle physicists and engineers from around the world; some remote and others participating in person. Presentations focused not only on the challenges at the FCC-ee, but also encompassed activities and initiatives at other facilities. The first week highlighted the plans for polarimetry measurements at the future Electron Ion Collider in the US. Complementary projects were presented from SuperKEKb in Japan, where the accelerator is stress-testing many aspects of the FCC-ee design, CEPC in China and other machines around the world.
Earth tides
The collision-energy calibration is a central consideration in the design and proposed operation strategy of the FCC-ee, in contrast to LEP where it was essentially an afterthought. At LEP, resonant depolarisation measurements were performed in dedicated calibration periods a few times per year. At FCC-ee these measurements will take place continually. This is essential, as a hard-learned lesson from LEP is that the beam energy is not constant, but varies throughout a fill, and also evolves over longer timescales. The gravitational pull of the moon distorts the tunnel in “Earth tides”, and modifies the relative trajectory of the beam through the quadrupole magnets, leading to energy changes that at LEP were around 10 MeV over a few hours during Z running, but will be 20 times larger at FCC-ee. Seasonal changes in the water level of Lac Leman lead to similar effects. At FCC-ee these distortions will be combatted by continuous adjustment of the radio frequency (RF) cavities, as is now routinely done in the LHC.
Additional challenges that were discussed in the workshop included the requirements on the laser polarimeters that will monitor the polarisation levels of the e+ and e– beams, the shifts in collision energy that will occur at each interaction point through the combined effect of synchrotron radiation and the boost provided by the RF system, as well as spurious dispersions folded with collision offsets. Here the project will benefit from the considerable progress achieved since LEP in both the reliability and precision of beam position and dispersion measurements. A particular highlight of the discussions was an agreement that it will be feasible to perform resonant depolarisation measurements at higher energies for use in the determination of the mass of the W boson, which was not possible at LEP, allowing this important parameter of nature to be measured around a factor 20–40 times better than at present.
The workshop concluded with a list of future tasks to be tackled and open questions. These questions will be addressed as part of the ongoing FCC Feasibility Study, with updates planned for the mid-term review, scheduled for the middle of 2023, and the final report in 2025.
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.
Axel Lindner was working in accelerator-based particle physics, astroparticle physics and management before he engaged in WISP searches in 2007 as the spokesperson of the ALPS I experiment. Since 2018 he has been leading a new experimental group at DESY in Hamburg in charge of realizing non-accelerator-based particle physics experiments on-site. Axel has been a member of the MADMAX and IAXO collaborations and spokesperson of ALPS II since 2012.
