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We need to talk about the Higgs

The LHC’s discovery of the Higgs boson in 2012 captured the world’s attention, but is too often said to have closed the door to new physics. Image credit: P Chappatte/Globe Cartoon

It is just over five years ago that the discovery of the Higgs boson was announced, to great fanfare in the world’s media, as a crowning success of CERN’s Large Hadron Collider (LHC). The excitement of those days now seems a distant memory, replaced by a growing sense of disappointment at the lack of any major discovery thereafter.

While there are valid reasons to feel less than delighted by the null results of searches for physics beyond the Standard Model (SM), this does not justify a mood of despondency. A particular concern is that, in today’s hyper-connected world, apparently harmless academic discussions risk evolving into a negative outlook for the field in broader society. For example, a recent news article in Nature led on the LHC’s “failure to detect new particles beyond the Higgs”, while The Economist reported that “Fundamental physics is frustrating physicists”. Equally worryingly, the situation in particle physics is sometimes negatively contrasted with that for gravitational waves: while the latter is, quite rightly, heralded as the start of a new era of exploration, the discovery of the Higgs is often described as the end of a long effort to complete the SM.

Let’s look at things more positively. The Higgs boson is a totally new type of fundamental particle that allows unprecedented tests of electroweak symmetry breaking. It thus provides us with a novel microscope with which to probe the universe at the smallest scales, in analogy with the prospects for new gravitational-wave telescopes that will study the largest scales. There is a clear need to measure its couplings to other particles – especially its coupling with itself – and to explore potential connections between the Higgs and hidden or dark sectors. These arguments alone provide ample motivation for the next generation of colliders including and beyond the high-luminosity LHC upgrade.

So far the Higgs boson indeed looks SM-like, but some perspective is necessary. It took more than 40 years from the discovery of the neutrino to the realisation that it is not massless and therefore not SM-like; addressing this mystery is now a key component of the global particle-physics programme. Turning to my own main research area, the beauty quark – which reached its 40th birthday last year – is another example of a long-established particle that is now providing exciting hints of new phenomena (see Beauty quarks test lepton universality ). One thrilling scenario, if these deviations from the SM are confirmed, is that the new physics landscape can be explored through both the b and Higgs microscopes. Let’s call it “multi-messenger particle physics”.

Tim Gershon

How the results of our research are communicated to the public has never been more important. We must be honest about the lack of new physics that we all hoped would be found in early LHC data, yet to characterise this as a “failure” is absurd. If anything, the LHC has been more successful than expected, leaving its experiments struggling to keep up with the astonishing rates of delivered data. Particle physics is, after all, about exploring the unknown; the analysis of LHC data has led to thousands of publications and a wealth of new knowledge, and there is every possibility that there are big discoveries waiting to be made with further data and more innovative analyses. We also should not overlook the returns to society that the LHC has brought, from technology developments with associated spin-offs to the training of thousands of highly skilled young researchers.

The level of expectation that has been heaped on the LHC seems unprecedented in the history of physics. Has any other facility been considered to have produced disappointing results because only one Nobel-prize winning discovery was made in its first few years of operation? Perhaps this reflects that the LHC is simply the right machine at the right time, but that time is not over: our new microscope is set to run for the next two decades and bring physics at the TeV scale into clear focus. The more we talk about that, the better our long-term chances of success.

To explore all our coverage marking the 10th anniversary of the discovery of the Higgs boson ...

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Aharon Casher 1941–2018

Aharon Casher’s work included spontaneous chiral symmetry breaking in QCD.

Aharon (Rony) Casher was born in Haifa, Israel, and graduated from the Technion where he performed his thesis work on condensed bosonic systems under Micha Revzen. He then went to Yeshiva University in New York, where he wrote a well-known paper with Joel Lebowitz on heat flow in random harmonic chains. This is also where his longstanding collaborations with Yakir Aharonov and Lenny Susskind began.

The Aharonov–Casher effect, which is dual to the Aharonov–Bohm effect, is textbook material and also led to a beautiful result on the number of zero modes in 2D magnetic fields. With Lev Vaidman, Casher and Aharonov developed the mathematics underpinning weak measurements; and in a separate work with Shimon Yankielowicz they introduced the mechanism of magnetic vacuum condensation for confinement in QCD. The early suggestion by Aharon, Susskind and John Kogut that a vacuum polarisation mechanism can account for quark confinement was extremely influential. Additional, important joint papers on strong interactions, partons and spontaneous chiral symmetry breaking appeared in the early 1970s. The collaboration with Susskind also led to Aharons’ familiarity with string theories and to the early paper with Aharonov of a dual string model for spinning particles.

In the high-energy physics community, Aharon is best known for his work on spontaneous chiral symmetry breaking in QCD. In a singly authored paper he provided a beautiful insight into this subject, followed by a famous paper with Tom Banks that related such breaking to the enhanced density of the low eigenvalues of the Dirac operator. These topics dominated Aharon’s interest throughout the 1970s and early 1980s. His deep knowledge of topological field theory and understanding of non-perturbative effects enabled him to make key and long-lasting contributions.

Aharon often visited Brussels, where he worked with François Englert and others on supergravity, quantum gravity and studies of the early universe. Englert, in turn, became a frequent visitor at Tel Aviv University, and non-perturbative effects in quantum gravity and possible connections to the physics of black holes became a shared passion of both. Although Aharon gave a series of influential lectures on string theory at Tel Aviv shortly after the 1984 “string revolution”, and published with Englert, Nicolai and Taormina a paper showing that all superstring theories are contained in the bosonic string, he was critical of strings as the ultimate theory of nature. He was an independent thinker, uncompromisingly honest when analysing novel ideas in theoretical physics.

Aharon stayed at Tel Aviv for almost 50 years, his knowledge and remarkable talents enabling him to teach any subject in theoretical physics from memory alone. He was accessible to students and attracted many who subsequently had independent academic careers, including Neuberger, Nissan Itzhaki and Yigal Shamir. Aharon was an avid reader, interested in literature, history, science fiction, sports and politics. One could have an interesting conversation with him on any topic.

Aharon was highly negligent as a self- promoter and was in science for the sheer pleasure of doing it. He rarely gave talks about his work, preferring to think and calculate at his desk, and his collaborators and many others had the deepest respect for him. His ability to keep challenging us and to relentlessly pursue the subtleties that could harbour fatal flaws helped maintain our own scientific integrity. Aharon will be deeply missed.

Physics of Atomic Nuclei

By Vladimir Zelevinsky and Alexander Volya Wiley

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Physics of Atomic Nuclei

This new textbook of nuclear physics aims to provide a review of the foundations of this branch of physics as well as to present more modern topics, including the important developments of the last 20 years. Even though well-established textbooks exist in this field, the authors propose a more comprehensive essay for students who want to go deeper both in understanding the basic principles of nuclear physics and in learning about the problems that researchers are currently addressing. Indeed, a renewed interest has lately revitalised this field, following the availability of new experimental facilities and increased computational resources.

Another objective of this book, which is based on the lectures and teaching experience of the authors, is to clarify, at each step, the relationship between theoretical equations and experimental observables, as well as to highlight useful methods and algorithms from computational physics.

The last few chapters cover topics not normally included in standard courses of nuclear physics, and reflect the scientific interests – and occasionally the point of view – of the authors. Many problems are also provided at the end of each chapter, and some of them are fully solved.

Compiled by Virginia Greco, CERN.

String Theory Methods for Condensed Matter Physics

By Horatiu Nastase
Cambridge University Press

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String Theory Methods for Condensed Matter Physics

This book provides an introduction to various methods developed in string theory to tackle problems in condensed-matter physics. This is the field where string theory has been most largely applied, thanks to the use of the correspondence between anti-de Sitter spaces (AdS) and conformal field theories (CFT). Formulated as a conjecture 20 years ago by Juan Maldacena of the Institute for Advanced Study, the AdS/CFT correspondence relates string theory, usually in its low-energy version of supergravity and in a curved background space–time, to field theory in a flat space–time of fewer dimensions. This correspondence is holographic, which means in some sense that the physics in the higher dimension is projected onto a flat surface without losing information.

The book is articulated in four parts. In the first, the author introduces modern topics in condensed-matter physics from the perspective of a string theorist. Part two gives a basic review of general relativity and string theory, in an attempt to make the book as self-consistent as possible. The other two parts focus on the applications of string theory to condensed-matter problems, with the aim of providing the reader with the tools and methods available in the field. Going into more detail, part three is dedicated to methods already considered as standard – such as the pp-wave correspondence, spin chains and integrability, AdS/CFT phenomenology and the fluid-gravity correspondence – while part four deals with more advanced topics that are still in development, including Fermi and non-Fermi liquids, the quantum Hall effect and non-standard statistics.

Aimed at graduate students, this book assumes a good knowledge of quantum field theory and solid-state physics, as well as familiarity with general relativity.

The Standard Theory of Particle Physics: Essays to Celebrate CERN’s 60th Anniversary

By Luciano Maiani and Luigi Rolandi (eds.)
World Scientific

Also available at the CERN bookshop

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The Standard Theory of Particle Physics: Essays to Celebrate CERN’s 60th Anniversary

This book is a collection of articles dedicated to topics within the field of Standard Model physics, authored by some of the main players in both its theory and experimental development. It is edited by Luciano Maiani and Luigi Rolandi, two well-known figures in high-energy physics.

The volume has 21 chapters, most of them devoted to very specific subjects. The first chapters take the reader through a fascinating tour of the history of the field, starting from the earliest days, around the time when CERN was established. I particularly enjoyed reading some recollections of Gerard ’t Hooft, such as: “Asymptotic freedom was discovered three times before 1973 (when Politzer, Gross and Wilczek published their results), but not recognised as a new discovery. This is just one of those cases of miscommunication. The ‘experts’ were so sure that asymptotic freedom was impossible, that signals to the contrary were not heard, let alone believed. In turn, when I did the calculation, I found it difficult to believe that the result was still not known.”

In chapter three, K Ellis reviews the evolution of our understanding of quantum chromodynamics (QCD) and deep-inelastic scattering. Among many things, he shows how the beta function depends on the strong coupling constant, αS, and explains why many perturbative calculations can be made in QCD, when the interactions take place at high-enough energies. At the hadronic scale, however, αS is too large and the perturbative expansion tool no longer works, so alternative methods have to be used. Many non-perturbative effects can be studied with the lattice QCD approach, which is addressed in chapter five. The experimental status regarding αS is reviewed in the following chapter, where G Dissertori shows the remarkable progress in measurement precision (with LHC values reaching per-cent level uncertainties and covering an unprecedented energy range), and how the data is in excellent agreement with the theoretical expectations.

Through the other chapters we can find a large diversity of topics, including a review of global fits of electroweak observables, presently aimed at probing the internal consistency of the Standard Model and constraining its possible extensions given the measured masses of the Higgs boson and of the top quark. Two chapters focus specifically on the W-boson and top-quark masses. Also discussed in detail are flavour physics, rare decays, neutrino masses and oscillations, as is the production of W and Z bosons, in particular in a chapter by M Mangano.

The Higgs boson is featured in many pages: after a chapter by J Ellis, M Gaillard and D Nanopoulos covering its history (and pre-history), its experimental discovery and the measurement of its properties fill two further chapters. An impressive amount of information is condensed in these pages, which are packed with many numbers and (multi-panel) figures. Unfortunately, the figures are printed in black and white (with only two exceptions), which severely affects the clarity of many of them. A book of this importance deserved a more colourful destiny.

The editors make a good point in claiming the time has come to upgrade the Standard Model into the “Standard Theory” of particle physics, and I think this book deserves a place in the bookshelves of a broad community, from the scientists and engineers who contributed to the progress of high-energy physics to younger physicists, eager to learn and enjoy the corresponding inside stories.

Relativity Matters: From Einstein’s EMC2 to Laser Particle Acceleration and Quark-Gluon Plasma

By Johann Rafelski
Springer

Also available at the CERN bookshop

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Relativity Matters: From Einstein’s EMC2 to Laser Particle Acceleration and Quark-Gluon Plasma

This monograph on special relativity (SR) is presented in a form accessible to a broad readership, from pre-university level to undergraduate and graduate students. At the same time, it will also be of great interest to professional physicists.

Relativity Matters has all the hallmarks of becoming a classic with further editions, and appears to have no counterpart in the literature. It is particularly useful because at present SR has become a basic part not only of particle and space physics, but also of many other branches of physics and technology, such as lasers. The book has 29 chapters organised in 11 parts, which cover topics from the basics of four-vectors, space–time, Lorentz transformations, mass, energy and momentum, to particle collisions and decay, the motion of charged particles, covariance and dynamics.

The first half of the book derives basic consequences of the SR assumptions with a minimum of mathematical tools. It concentrates on the explanation of apparently paradoxical results, presenting and refuting counterarguments as well as debunking various incorrect statements in elementary textbooks. This is done by cleverly exploiting the Galilean method of a dialogue between a professor, his assistant and a student, to bring out questions and objections.

The importance of correctly analysing the consequences for extended and accelerating bodies is clearly presented. Among the many “paradoxes”, one notes the accelerating rocket problem that the late John Bell used to tease many of the world’s most prominent physicists with. Few of them provided a perfectly satisfactory answer.

The second half of the book, starting from part VII, covers the usual textbook material and techniques at graduate level, illustrated with examples from the research frontier. The introductions to the various chapters and subsections are still enjoyable for a broader readership, requiring little mathematics. The author does not avoid technicalities such as vector and matrix algebra and symmetries, but keeps them to a minimum. However, in the parts dealing with electromagnetism, the reader is assumed to be reasonably familiar with Maxwell’s equations.

There are copious concrete exercises and solutions. Throughout the book, indeed, every chapter is complemented by a rich variety of problems that are fully worked out. These are often used to illustrate quantitatively intriguing topics, from space travel to the laser acceleration of charged particles.

An interesting afterword concluding the book discusses how very strong acceleration becomes a modern limiting frontier, beyond which SR in classical physics becomes invalid. The magnitude of the critical accelerations and critical electric and magnetic fields are qualitatively discussed. It also briefly analyses attempts by well-known physicists to side-step the problems that arise as a consequence.

Relativity Matters is excellent as an undergraduate and graduate textbook, and should be a useful reference for professional physicists and technical engineers. The many non-specialist sections will also be enjoyed by the general, science-interested public.Torleif Ericson, CERN

CLIC workshop focuses on strategy

The participants of the 2018 CLIC workshop outside CERN’s main building. Image credit: M Volpi

The Compact Linear Collider (CLIC) workshop is the main annual gathering of the CLIC accelerator and detector communities, and this year attracted more than 220 participants to CERN on 22–26 January. CLIC is a proposed electron-positron linear collider envisaged for the era beyond the high-luminosity LHC (HL-LHC), that would operate a staged programme over a period of 25 years with collision energies at 0.38, 1.5, and 3 TeV. This year the CLIC workshop focused on preparations for the update of the European Strategy for Particle Physics in 2019–2020.

The initial CLIC energy stage is optimised to provide high-precision Higgs boson and top-quark measurements, with the higher-energy stages enhancing sensitivity to effects from beyond-Standard Model (BSM) physics (CERN Courier November 2016 p20). Following a 2017 publication on Higgs physics, the workshop heard reports on recent developments in top-quark physics and the BSM potential at CLIC, both of which are attracting significant interest from the theory community.

Speakers also reported extensive progress in the validation and performance of the new detector model. To ensure that its performance meets the challenging specifications, a new approach to tracking has been commissioned, and the particle flow analysis and flavour-tagging capabilities have been consolidated. Updates were presented on the broad and active R&D programme on the vertex and tracking detectors, which aims to find technologies that simultaneously fulfil all the CLIC requirements. Reports were given on test-beam campaigns with both hybrid and monolithic assemblies, and on ideas for future developments. Many of the tracking and calorimeter technologies under study for the CLIC detector are also of interest to the HL-LHC, where the high granularity and time-resolution needed for CLIC are equally crucial.

For the accelerator, studies with the aim of reducing the cost and power have particular priority, presenting the initial CLIC stage as a project requiring resources comparable to what was needed for LHC. Key activities in this context are high-efficiency RF systems, permanent magnet studies, optimised accelerator structures and overall implementation studies related to civil engineering, infrastructure, schedules and tunnel layout.

A key aspect of the ongoing accelerator development is moving towards industrialisation of the component manufacture, by fostering wider applications of the CLIC 12 GHz X-band technology with external partners. In this respect, the CLIC workshop coincided with the kick-off meeting for the CompactLight project recently funded by the Horizon 2020 programme, which aims to design an optimised X-ray free-electron laser based on X-band technology for more compact and efficient accelerators (CERN Courier December 2017 p8).

Last year also saw the realisation of the CERN Linear Electron Accelerator for Research (CLEAR), a new user facility for accelerator R&D whose programme includes CLIC high-gradient and instrumentation studies (CERN Courier November 2017 p8). Presentations at the workshop addressed the programmes for instrumentation and radiation studies, plasma-lensing, wakefield monitors and high-energy electrons for cancer therapy.

During 2018 the CLIC accelerator and detector and physics collaborations will prepare summary reports focusing on the 380 GeV initial CLIC project implementation as inputs for the update of the European Strategy for Particle Physics, including plans for the project preparation phase in 2020–2025.

Physics fest for a future circular collider

The LHC would be part of the injection system for a future circular collider. Image credit: CERN

The second Future Circular Collider (FCC) physics workshop was held at CERN on 15–19 January, gathering particle physicists from around the world for talks and detailed discussions on the physics capabilities of future electron–positron, electron–proton, and proton–proton colliders.

The FCC study, which emerged following the 2013 European Strategy for Particle Physics, is a five-year project led by CERN to investigate a circular collider built in a new 100 km-circumference tunnel in the Geneva region. Such a tunnel could host an e+e– collider (called FCC-ee), a 100 TeV proton–proton collider (FCC-hh) or an electron–proton collider (FCC-eh). Further opportunities include the collision of heavy ions in FCC-hh and FCC-eh, and fixed-target experiments using the injector complex.

Last year saw a significant evolution in the maturity of the physics studies for these machines, with many detailed results presented. These results include new techniques to determine the properties of the Higgs boson, such as the all-important Higgs potential, and how these relate to fundamental questions at the smallest distance scales. New ideas about how to search for new particles interacting very weakly with normal matter – such as new species of neutrinos, dark photons or other new light scalar particles – were also studied in depth.

The January workshop was preceded by a dedicated meeting to determine whether the unprecedented precision of physics measurements provided by FCC machines could be compared against equally high-precision theoretical predictions.

The results of this study were affirmative, as reported on the first day of the FCC physics workshop.

A major theme that emerged during the workshop was the depth of complementarity between the capacities of the different FCC modes in exploring the questions that will remain open after the completion of the LHC programme. Combining their individual strengths will enable comprehensive exploration in search of answers to the pending questions in particle physics.

Europe defines astroparticle strategy

The APPEC report makes 21 recommendations for the astroparticle-physics community.

Multi-messenger astronomy, neutrino physics and dark matter are among several topics in astroparticle physics set to take priority in Europe in the coming years, according to a report by the Astroparticle Physics European Consortium (APPEC).

The APPEC strategy for 2017–2026, launched at an event in Brussels on 9 January, is the climax of two years of talks with the astroparticle and related communities. 20 agencies in 16 countries are involved and includes representation from the European Committee for Future Accelerators, CERN and the European Southern Observatory (ESO).

Lying at the intersection of astronomy, particle physics and cosmology, astroparticle physics is well placed to search for signs of physics beyond the standard models of particle physics and cosmology. As a relatively new field, however, European astroparticle physics does not have dedicated intergovernmental organisations such as CERN or ESO to help drive it. In 2001, European scientific agencies founded APPEC to promote cooperation and coordination, and specifically to formulate a strategy for the field.

Building on earlier strategies released in 2008 and 2011, APPEC’s latest roadmap presents 21 recommendations spanning scientific issues, organisational aspects and societal factors such as education and industry, helping Europe to exploit tantalising potential for new discoveries in the field.

There are plans to join forces with experiments in the US to build the next generation of NDBD detectors.

The recent detection of gravitational waves from the merger of two neutron stars (CERN Courier December 2017 p16) opens a new line of exploration based on the complementary power of charged cosmic rays, electromagnetic waves, neutrinos and gravitational waves for the study of extreme events such as supernovae, black-hole mergers and the Big Bang itself. “We need to look at cross-fertilisation between these modes to maximise the investment in facilities,” says APPEC chair Antonio Masiero of the INFN and the University of Padova. “This is really going to become big.”

APPEC strongly supports Europe’s next-generation ground-based gravitational interferometer, the Einstein Telescope, and the space-based LISA detector. In the neutrino sector, KM3NeT is being completed for high-energy cosmic neutrinos at its site in Sicily, as well as for precision studies of atmospheric neutrinos at its French site near Toulon. Europe is also heavily involved in the upgrade of the leading cosmic-ray facility the Pierre Auger Observatory in Argentina. Significant R&D work is taking place at CERN’s neutrino platform for the benefit of long- and short-baseline neutrino experiments in Japan and the US (CERN Courier July/August 2016 p21), and Europe is host to several important neutrino experiments. Among them are KATRIN at KIT in Germany, which is about to begin measurements of the neutrino absolute mass scale, and experiments searching for neutrinoless double-beta decay (NDBD) such as GERDA and CUORE at INFN’s Gran Sasso National Laboratory (CERN Courier December 2017 p8).

There are plans to join forces with experiments in the US to build the next generation of NDBD detectors. APPEC has a similar vision for dark matter, aiming to converge next year on plans for an “ultimate” 100-tonne scale detector based on xenon and argon via the DARWIN and Argo projects. APPEC also supports ESA’s Euclid mission, which will establish European leadership in dark-energy research, and encourages continued European participation in the US-led DES and LSST ground-based projects. Following from ESA’s successful Planck mission, APPEC strongly endorses a European-led satellite mission, such as COrE, to map the cosmic-microwave background and the consortium plans to enhance its interactions with its present observers ESO and CERN in areas of mutual interest.

“It is important at this time to put together the human forces,” says Masiero. “APPEC will exercise influence in the European Strategy for Particle Physics, and has a significant role to play in the next European Commission Framework Project, FP9.”

A substantial investment is needed to build the next generation of astroparticle-physics research, the report concedes. According to Masiero, European agencies within APPEC currently invest around €80 million per year in astroparticle-related activities, in addition to funding large research infrastructures. A major effort in Europe is necessary for it to keep its leading position. “Many young people are drawn into science by challenges like dark matter and, together with Europe’s existing research infrastructures in the field, we have a high technological level and are pushing industries to develop new technologies,” continues Masiero. “There are great opportunities ahead in European astroparticle physics.”

• View the full report at www.appec.org.

Neutrons cooled for interrogation

A proton beamline at TRIUMF branches off to a tungsten spallation target, producing neutrons that are slowed to ultracold speeds in cryostats and directed to the UCN experimental area (right). The EDM cell is magnetically shielded by cylindrical layers. Image credit: TRIUMF

Researchers at TRIUMF in Canada have reported the first production of ultracold neutrons (UCN), marking an important step towards a future neutron electric dipole moment (nEDM) experiment at the Vancouver laboratory. Precision measurements of the nEDM are a sensitive probe of physics beyond the Standard Model: if a nonzero value were to be measured, it would suggest a new source of CP violation, possibly related to the baryon asymmetry of the universe.

The TUCAN collaboration (TRIUMF UltraCold Advanced Neutron source) aims to measure nEDM a factor 30 better than the present best measurement, which has a precision of 3 × 10–26 e cm and is consistent with zero. For this to be possible, physicists need to provide the world’s highest density of ultracold neutrons. In 2010 a collaboration between Canada and Japan was established to realise such a facility and a prototype UCN source was shipped to Canada and installed at TRIUMF in early 2017.

The setup uses a unique combination of proton-induced spallation and a superfluid helium UCN source that was pioneered in Japan. A tungsten block stops a beam of protons, producing a stream of fast neutrons that are then slowed in moderators and converted to ultracold speeds (less than around 7 ms–1) by phonon scattering in superfluid helium. The source is based on a non-thermal down-scattering process in superfluid helium below 1 K, which gives the neutrons an effective temperature of a few mK. The ultracold temperature is below the neutron optical potential for many materials, which means the neutrons are totally reflected for all angles of incidence and can be stored in bottles for periods of up to hundreds of seconds.

Tests late last year demonstrated the highest current operation of this particular source, resulting in the most UCNs it has ever produced (> 300,000) in a single 60-second-long irradiation at a 10 µA proton beam current. This is a record for TRIUMF, but the UCN source intensity is still two orders of magnitude below what is needed for the nEDM experiment.

Funding of C$15.7 million to upgrade the UCN facility, a large proportion of which was granted by the Canada Foundation for Innovation in October 2017, will enable the TUCAN team to increase the production of neutrons at higher beam current to levels competitive with other planned nEDM experiments worldwide. These include proposals at the Paul Scherrer Institute in Switzerland, Los Alamos National Laboratory in the US, the Institut Laue–Langevin in France and others in Germany and Russia. The neutron EDM is experiencing intense competition, with most projects differing principally in the way they propose to produce the ultracold neutrons (CERN Courier September 2016 p27).

The nEDM experimental campaign at TRIUMF is scheduled to start in 2021. “The TRIUMF UCN source is the only one combining a spallation source of neutrons with a superfluid helium production volume, providing the project its uniqueness and competitive edge,” says team member Beatrice Franke.

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