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CERNNovember/December 2020 cerncourier.com COURIERReporting on international high- WLCOMEE CERN Courier – digital edition ADVANCING Welcome to the digital edition of the November/December 2020 issue of CERN Courier. CAVITY

Superconducting radio-frequency (SRF) cavities drive accelerators around the world, transferring energy efficiently from high-power radio waves to beams of charged . Behind the march to higher SRF-cavity performance is the Technology for peace Collaboration (p35), which was established in 1990 to advance technology for a linear Feebly interacting particles – . Though the linear collider envisaged by TESLA is yet ALICE’s dark side to be built (p9), its cavity technology is already established at the European X-Ray Free-Electron at DESY (a cavity for which graces the cover of this edition) and is being applied at similar broad-user-base facilities in the US and China.

Accelerator technology developed for fundamental physics also continues to impact the medical arena. Normal-conducting RF technology developed for the proposed at CERN is now being applied to a first-of-a-kind “FLASH-therapy” facility that uses to destroy deep-seated tumours (p7), while beams are being used for novel non-invasive treatments of cardiac arrhythmias (p49). Meanwhile, GANIL’s innovative new SPIRAL2 linac will advance a wide range of applications in nuclear physics (p39).

Detector technology also continues to offer unpredictable benefits – a powerful example being the potential for detectors developed to search for sterile neutrinos to replace increasingly outmoded traditional approaches to nuclear nonproliferation (p30).

Elsewhere in the issue: hints of low-frequency gravitational waves (p12), feebly interacting particles to the fore (p21), PCs and the future of computing (p43), the latest from the LHC experiments (p17), and more – not least the Courier’s inaugural end-of-year cryptic crossword (p58).

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EDITOR: MATTHEW CHALMERS, CERN DIGITAL EDITION CREATED BY IOP PUBLISHING

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IN THIS ISSUE V o l u m e 60 N u m b e r 6 N o V e m b e r /D e c e m b e r 2 02 0 It’s for a New Generation of Power ! Observatory NSF/Green Bank Virginia Tech G Zanderighi

FOR RESISTIVE AND SUPERCONDUCTING

CT-BOX Hidden scope Pulsars hint at gravitational waves in Nuclear nonproliferation detectors Questions Giulia Zanderighi on All-In-One Current and Calibration System the nHz region. 12 may replace outdated protocols. 30 collider phenomenology. 45 Up to ±1.000 A, 1 ppm/K TC, 100 ksps Data-Logger and Oscilloscope CT-Viewer software included with Ethernet, Serial and USB NeWS PeoPle EASY-DRIVER ±5 A and ±10 A / ±20 V Bipolar Power Supply Series ANALYSIS ENERGY FRONTIERS FIELD NOTES CAREERS OBITUARIES FLASH radiotherapy Right-handed photons Strong interest in Horst Wenninger Full-Bipolar operation, Digital Control Loop, Ethernet Connectivity Beating cardiac CERN environmental Leptoquarks and feeble interactions John Thompson Max Device supported by Visual Easy-Driver software • • arrhythmia • • report • ILC’s next phase the third generation • Heavy-flavour EBAMed is pioneering Zolotorev • David Newton • SPS reimagined • Win • Cornering WIMPs highlights from the use of proton beams • Philippe Mermod FAST-PS-M for Weinberg • Black holes • Fragile light nuclei Beauty 2020. 21 to enable non-invasive • Ronald Fortune Digital Monopolar Power Supplies - up to 100 A attract Nobel prize flow.17 treatment of irregular • Eugène Cremmer. 54 Low-frequency GWs. 7 High-Precision Monopolar Power Converters with Gigabit Ethernet • beating of the heart. 49 Embedded Linux OS, device supported by Visual PS software FeATureS

FAST-PS CERN-PHOTO-202008-104-63 Digital Bipolar Power Supplies - up to ±30 A and ±80 V ANTINUCLEI DETECTORS SRF RESEARCH FACILITIES Full-Bipolar, Digital Control Loop, High-Bandwidth, 10/100/1000 Ethernet ALICE’s dark side Neutrinos for peace TESLA’s high- Spiralling into Embedded Linux OS, device supported by Visual PS software Precision Detectors could gradient march the femtoscale at the LHC’s ALICE help guard against The TESLA Technology GANIL’s SPIRAL2 facility experiment are the extraction of Collaboration has will address applications FAST-PS-1K5 sharpening the search plutonium-239 for played a major role in in fission and materials Digital Bipolar Power Supplies - up to ±100 A and ±100 V for . 25 nuclear weapons. 30 SRF cavities and related science using charged 1.500 W, Paralleling via SFP/SFP+, 1 ppm/K TC, 10/100/1000 Ethernet technologies. 35 and beams. 39 Embedded Linux OS, device supported by Visual PS software

NGPS oPINIoN DePArTmeNTS High-Stability 10-kW Power Supply - 200 A / 50 V Digital Control Loop, Paralleling via SFP/SFP+, 10/100/1000 Ethernet VIEWPOINT INTERVIEW REVIEWS FROM THE EDITOR 5 Embedded Linux OS, device supported by Visual PS software A unique period In pursuit of Weinberg on NEWS DIGEST 15 D Noelle/DESY for computing, the possible astrophysics APPOINTMENTS 50 but will it last? Giulia Zanderighi The foundations of & AWARDS Sverre Jarp looks at the discusses fundamental astrophysics How to • RECRUITMENT 51 impact and future of physics at the boundary find a Higgs .47 On the cover: Roll-out the PC in high-energy between theory and from a DESY cleanroom of a BACKGROUND 58 physics. 43 experiment. 45 3.9 GHz RF cavity string for the European XFEL. 35

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Accelerator applications shine

ens of thousands of accelerators are in oper- Unforeseen benefits ation worldwide – almost all of them in industry and Behind this march to higher SRF performance is the TESLA T clinical settings, with only a few percent used in Technology Collaboration (p35), which was established in 1990 research. In recent decades, particle have perfected to advance technology for a linear electron–positron collider. Its the art of superconducting radio-frequency (SRF) acceler- remit later expanded to cover the full diversity of applications, ation (the cover theme of this issue), whereby metallic cav- enabling the sharing of ideas, planning and testing across ities provide a pristine, resonant space in which to transfer associated projects, and all the major particle-physics labs are Matthew energy from high-power radio waves to a beam of charged members. Though the linear Chalmers particles. While both superconducting and normal-conduct- collider envisaged by TESLA Editor ing cavities still vie for inclusion in the biggest projects, as is yet to be built (p9), its cavity

evidenced by the designs of the proposed electron–positron D Noelle/DESY technology is already estab- Higgs factories ILC and CLIC, SRF cavities store energy with lished at the European XFEL in very low losses and offer a high conversion efficiency from Germany and for other X-ray “plug- to beam-” power. free-electron in the US SRF accelerator technology took hold in the mid-1980s with and China. It will be deployed bulk- cavities at Cornell’s CESR facility. JLab’s CEBAF in neutron sources such as followed suit, while CERN turned to niobium-coated copper the ESS and in ’s cavities to extend the energy reach of LEP from the Z to the PIP-II linac, serving short- WW threshold. These days, niobium-copper cavities ramp the and long-baseline neutrino LHC’s to 6.5 TeV and keep them tightly bunched, while experiments. SRF “crab cavities” built entirely from ultra-pure niobium are Advanced accelerator undergoing tests for the high-luminosity LHC, where they will technology also continues tilt proton bunches to ensure maximum collision intensity. to impact the medical arena. SRF underpins the ALPI and SPIRAL2 (p39) linacs at INFN Normal-conducting X- and GANIL, and drives advanced X-ray and neutron sources. High impact SRF cavities drive band RF technology devel- Though to the untrained eye the RF cavity might look like a accelerators for applied research. oped for CLIC is now being si mple me t a l she l l, subt le m ater i a l effe c t s, f abr ic at te c h- applied to a first-of-a-kind niques, surface smoothness and, above all, surface clean- “FLASH-therapy” facility that uses electrons to destroy liness have a dramatic effect on its performance. In recent tumours (p7), while proton beams are being used for novel years, bulk-niobium SRF technology has seen big increases non-invasive treatments of cardiac arrhythmias (p49). A further in attainable accelerating gradients and quality factors due to p o w e r f u l e x a m pl e o f t h e u n pr e d i c t e d b e n e fit s o f f u n d a m e nt al Advanced nitrogen-doping or nitrogen-infusion, while CERN has con- research is the role of state-of-the-art neutrino detectors in accelerator tinued its R&D on coated cavities. Seamless niobium-copper nuclear safeguarding (p30). technology cavities built using a sophisticated electrodeposition tech- Elsewhere in the issue: hints of low-frequency gravitational nique are the basis of the recent HIE-ISOLDE energy upgrade, waves (p12), feebly interacting particles to the fore (p21), PCs continues to extending ISOLDE’s reach to heavier isotopes. The CERN team and the future of computing (p43), the latest from the LHC impact the is also investigating SRF thin-film technology relevant for a experiments (p17), and more – not least the Courier’s inaugural medical arena possible future circular electron–positron collider. end-of-year cryptic crossword (p58).

Reporting on international high-energy physics

CERN Courier is distributed Editor Laboratory correspondents INFN Antonella Varaschin UK STFC Jane Binks Technical illustrator General distribution to governments, institutes Matthew Chalmers Argonne National Jefferson Laboratory SLAC National Accelerator Alison Tovey Courrier Adressage, CERN, and laboratories affiliated Associate editor Laboratory Tom LeCompte Kandice Carter Laboratory Melinda Baker Advertising sales 1211 Geneva 23, ; with CERN, and to Mark Rayner Brookhaven National JINR Dubna B Starchenko SNOLAB Samantha Kuula Tom Houlden e-mail courrier- individual subscribers. Editorial assistant Laboratory Achim Franz KEK National Laboratory TRIUMF Laboratory Recruitment sales adressage@.ch It is published six Craig Edwards Cornell University Hajime Hikino Marcello Pavan Chris Thomas per year. The views Archive contributor D G Cassel Lawrence Berkeley Advertisement Published by CERN, 1211 expressed are not Peggie Rimmer DESY Laboratory Laboratory Spencer Klein Produced for CERN by production Katie Graham Geneva 23, Switzerland necessarily those of the Astrowatch contributor Till Mundzeck Los Alamos National Lab IOP Publishing Ltd Marketing and Tel +41 (0) 22 767 61 11 CERN management. Merlin Kole Enrico Fermi Centre Rajan Gupta Temple Circus, Temple circulation Laura Gillham E-mail Guido Piragino NCSL Ken Kingery Way, Bristol BS1 6HG, UK Printed by Warners [email protected] Fermilab Kurt Nikhef Robert Fleischer Tel +44 (0)117 929 7481 Advertising (Midlands) plc, Bourne, Riesselmann Novosibirsk Institute Tel +44 (0)117 930 1026 Lincolnshire, UK Advisory board Forschungszentrum S Eidelman Head of Media Jo Allen (for UK/Europe display , Christine Jülich Markus Buescher Orsay Laboratory Head of Media advertising) or © 2020 CERN Sutton, Claude Amsler, GSI Darmstadt I Peter Anne-Marie Lutz Business Development +44 (0)117 930 1164 (for ISSN 0304-288X Philippe Bloch, Roger IHEP, Beijing Lijun Guo PSI Laboratory P-R Kettle Ed Jost recruitment advertising); Forty, Mike Lamont, IHEP, Serpukhov Saclay Laboratory Content and production e-mail sales@ Joachim Kopp Yu Ryabov Elisabeth Locci manager Ruth Leopold cerncourier.com

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A pplicAtions CLIC lights the way for FLASH therapy CERN Technology developed for the pro‑ ‑ posed Compact Linear Collider (CLIC) at PHOTO

CERN is poised to make a novel cancer ‑ 202008 radio‑therapy facility a reality. Building ‑ on recently revived research from the 108 ‑ 1970s, oncologists believe that ultrafast 10 bursts of electrons damage tumours more t h a n h e a lt h y t i s s u e. T h i s “F L A SH e ffe c t” could be realised by using high‑gradi‑ ent accelerator technology from CLIC to create a new facility at Switzerland’s Lausanne University Hospital (CHUV). Traditional radiotherapy scans photon beams from multiple angles to focus a radiation dose on tumours inside the body. More recently, therapy has offered a fur t her treatment modal‑ ity: by tuning the energy of a beam of protons or so that they stop in the tumour, the particles deposit most of the radiation dose there (the so‑called Bragg peak), while sparing the surrounding healthy tissue by comparison. Both of these treatments deliver small doses of radiation to a patient over an extended period, whereas FLASH radiotherapy is X-band A high-gradient accelerating structure at CERN’s CLEAR test facility, showing the waveguides thought to require a maximum of three that feed RF power in and out. doses, all lasting less than 100 ms. radio‑frequency cavity technology design report, funded by CHUV, being Look again developed for CLIC, CHUV has teamed created together by CERN and CHUV. The When the FLASH effect was first stud‑ up with CERN to develop a facility that development and construction of the first ied in the 1970s, it was assumed that can produce electron beams with ener‑ facility, which would be housed at CHUV, all tissues suffer less damage when a gies around 100 MeV, in order to reach is predicted to cost around €25 million, dose is ultrafast, regardless of whether tumour depths of up to 20 cm. The idea and CHUV aims to complete the facility Vacuum solutions they are healthy or tumorous. In 2014, came about three years ago when it within three years. however, CHUV researchers published was realised that CLIC technology was “The intention of CERN and the team a study in which 200 mice were given almost a perfect match for what CHUV is to be heavily involved in the process of a single dose of 4.5 MeV gamma rays were looking for: a high‑powered accel‑ getting the facility built and operating,” at a conventional therapy dose‑rate, erator, which uses X‑band technology to states Wuensch. “It really looks like it has from a single source while others were given an equivalent accelerate particles over a short distance, the potential to be an important comple‑ dose at the much faster FLASH‑therapy has a high luminosity, and utilises a high ment to e x ist ing radiat ion t herapies.” rate. The results showed explicitly that current that allows a higher volume of Cancer therapies have taken advantage Pfei er Vacuum is proud to have been a supplier of innovative and customized vacuum solutions to the while the normal tissue was damaged tumour to be targeted. of particle accelerators for many dec‑ community for more than 50 years. Our complete product portfolio for vacuum technology, our focus on competent and s i g n i fic a nt l y l e s s b y t h e u lt r a f a s t b u r sts, “CLIC has the ability to accelerate a ades, with proton radiotherapy entering specialized advice supported by robust and reliable service, makes Pfei er Vacuum the partner of choice for the analytical the damage to the tumour stayed con‑ large amount of charge to get enough the scene in the 1990s. The CERN‑based and research communities worldwide. sistent for both therapies. In 2019, CHUV It really looks luminosity for physics studies,” explains Proton‑Ion Medical Study, applied the first FLASH treatment to a like it has the Walter Wuensch of CERN, who heads the spawned by the TERA Foundation, ■ Pumps for vacuum generation down to UHV c a n c e r p a t ie nt, fi n d i n g s i m i l a rl y p o s it i ve potential to be FLASH project at CERN. “People tend to resulted in the National Centre for ■ Vacuum measurement and analysis equipment results: a 3.5 cm diameter skin tumour an important focus on the accelerating gradient, but as Cancer Hadron Therapy (CNAO) in Italy completely disappeared using electrons important, or arguably more important, and MedAustron in Austria, which have ■ Leak detectors and integrity test systems complement from a 5.6 MeV linear accelerator, “with is the ability to control high‑current, m a d e s i g n i fic a nt pr o g r e s s i n t h e fie l dof ■ Vacuum chambers and components n e a rl y n o s i d e e ffe c t s”. T h e c h a l l e n g e w as to existing low-emittance beams.” proton and ion therapy. FLASH radio‑ ■ Pumping stations and customized solutions to reach deeper tumours. radiation The first phase of the collaboration is therapy would add electrons to the grow‑ Now, using high-gradient “X-band” therapies nearing completion, with a conceptual ing modality of particle therapy. Are you looking for a perfect vacuum ? Please contact us: Pfeiffer Vacuum (Schweiz) AG · T +41 44 444 22 55 · F +41 44 444 22 66 · [email protected] www.pfeiffer-vacuum.com CERN COURIER NOVEMBER/DECEMBER 2020 7

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NEWS ANALYSIS NEWS ANALYSIS

En vironmEnt AccelerAtors CER N publishes first env ironmenta l report Preparatory ‘pre-lab’ proposed for ILC R Hori/KEK R “It is our vision for CERN to be a role CERN-PHOTO-201504-073-3 On 10 September the International Com- model for environmentally responsible mittee for Future Accelerators (ICFA) research,” writes CERN Director-General announced the structure and members in her introduction to a of a new organisational team to prepare landmark environmental report released a “pre-laboratory” for an International by the laboratory on 9 September. While Linear Collider (ILC) in Japan. The ILC CERN has a longstanding framework International Development Team (ILC- in place for environmental protection, IDT), which consists of an executive and has documented its environmental board and three working groups gov- i m p a c t for d e c a d e s, t h i s i s it s fi r s t p u bl ic erning the pre-lab setup, accelerator, and report. Two years in the making, and physics and detectors, aims to complete prepared according to the Global Report- the preparatory phase for the pre-lab on ing Initiative Sustainability Reporting a timescale of around 1.5 years. Standards, it details the status of CERN’s The aim of the pre-lab is to prepare Down the line prime minister at that time, Yoshihiko required further discussion in formal environmental footprint, along with the ILC project, should it be approved, for How an Noda, stressing the importance of estab- academic decision-making processes. objectives for the coming years. construction. It is based on a memoranda accelerating lishing an international framework. In February KEK submitted an applica- Given the energy consumption of large of understanding among participating module for the In 2018 ICFA backed the ILC as a Higgs tion for the ILC project to be considered particle accelerators, environmental national and regional laboratories, International factory operating at a centre-of- in the MEXT 2020 roadmap for large- impact is a topic of increasing importance rather than intergovernmental agree- Linear Collider energy of 250 GeV – half the energy set scale research projects. KEK withdrew for high-energy physics research world- ments, explains chair of the ILC-IDT (ILC) might look. out five years earlier in the ILC’s tech- the application the following month, wide. Among the recommendations of the executive board Tatsuya Nakada of École nical design report. announcing the move in September fol- 2020 update of the European strategy for Greener pastures Members of the CERN safety engineering and environment group at one of around Polytechnique Fédérale de Lausanne. An electron–positron Higgs factory is lowing the establishment of the ILC-IDT. was a strong emphasis 100 environment monitoring stations on and around the laboratory’s sites. “The ILC-IDT is preparing a proposal the highest-priority next collider, con- “The ministry will keep an eye on dis- on the need to continue with efforts to for the organisational and operational cluded the 2020 update of the European cussions by the international research minimise the environmental impact of is 87.9% carbon-free. In terms of direct versational speech). The organisation has framework of the pre-lab, which will strategy for particle physics (ESPPU). community while exchanging opinions accelerator facilities and maximise the greenhouse- emissions, the 192,000 also introduced approaches to preserve have a cent r a l office i n Japa n hosted by The ESPPU recommended that Europe, with government authorities in the energy efficiency of future projects. tonnes of carbon-dioxide equivalent the local landscape and protect flora, the KEK laboratory,” says Nakada. “In together with its international partners, US and Europe,” said Koichi Hagiuda, When the (LHC) emitted by CERN in 2018 is mainly due to including 15 species of orchid growing parallel to our activities, we hope that explore the feasibility of a future hadron Japanese minister of education, culture, is operating, CERN uses an average of flu or i n a t e d g a s e s u s e d i n t h e L HC detc- on CERN’s sites. the effort by our Japanese colleagues will collider at CERN at the energy frontier sports, science and technology, at a press 4300 TJ of every year (30–50% tors for cooling, particle detection, air result in a positive move by the Japanese with an electron–positron Higgs factory conference on 11 September. less when not in operation) – enough conditioning and electrical insulation. Waste not government that is equally essential for as a possible first stage, noting t hat t he Steinar Stapnes of CERN, who is energy to power just under half of the CERN has set a formal objective that, by Water consumption, mostly drawn from establishing the pre-laboratory.” timely realisation of the ILC in Japan a member of the ILC-IDT executive 200,000 homes in the canton of Geneva. 2024, direct greenhouse emissions will Lac Léman, has slowly decreased over In June the Linear Collider Board and “would be compatible with this strategy”. board representing Europe, says that “This is an inescapable fact, and one that be reduced by 28% by replacing fluori- the past 10 years, the report notes, and Linear Collider Collaboration, which Two further proposals exist: the Compact clear support from the Japanese gov- CERN has always taken into consider- nated – which were designed in the CERN commits to keeping the increase in were established by ICFA in 2013 to pro- Linear Collider at CERN and the Circu- ernment is needed for the ILC pre-lab. ation when designing new facilities,” 1990s to be ozone-friendly – with carbon water consumption below 5% to the end of mote the case for an electron–positron lar Electron–Positron Collider in China. “The overall project size is much larger states Frédérick Bordry, director for dioxide, which has a global-warming 2024, despite a growing demand for cool- linear collider and its detectors as a While the ILC is the most technically than the usual science projects being accelerators and technology. potential several thousand times lower. ing from upgraded facilities. CERN also worldwide collaborative project, reached ready Higgs-factory proposal (see p35), considered in these processes and it is O t h e r a r e a s o f e n v i r o n m e nt a l s i g n i fi- eliminates 100% of its waste, states the the end of their terms in view of ICFA’s physicists are still awaiting a concrete difficult to see how it could be funded Action plan cance studied in the report include radi- report, and has a recycling rate of 56% for decision to set up the ILC-IDT. decision about its future. within the normal MEXT budget for An energy-management panel estab- ation exposure, noise and waste. CERN non-hazardous waste (which comprises The ILC has been on the table for In March 2019 Japan’s Ministry of large-scale science,” he says. “During lished at CERN in 2015 has already led to commits to limit the emission of ionising 81% of the total). A major project under almost two decades. Shortly after the Education, Culture, Sports, Science and the pre-lab phase, intergovernmental actions, including free cooling and air- radiation to no more than 0.3 mSv per construction since last year will see waste discovery of the in 2012, Technology (MEXT) expressed “contin- discussions and negotiation about the flo w o p t i m i s a t i o n, b e t t e r o p t i m i s e d L HC year – less than a third of the annual hot water from the cooling system for LHC the Japanese high-energy physics ued interest” in the ILC, but announced share of funding and responsibilities for cryogenics, and the implementation of dose limit for public exposure set by the Point 8 (where the LHCb experiment is community proposed to host the esti- that it had “not yet reached declaration” the ILC construction need to take place SPS magnetic cycles and stand-by modes, European Council. The report states that located) channeled to a heating network in mated $7 billion project, with Japan’s for hosting the project, arguing that it and hopefully converge.” w h ic h sig n i fic a nt ly re duce e nerg y con- the actual dose to any member of the the nearby town of Ferney-Voltaire from sumption. The LHC delivered twice as public living in the immediate vicinity 2022, with LHC Points 2 and 5 being con- much data per in its second run of CERN due to the laboratory’s activities sidered for similar projects. (2015–2018) compared to its first (2010– is below 0.02 mSv per year, which is less CERN plans to release further environ- Electron makeover studied for the SPS 2013), states the new report. With the than the exposure received from cosmic ment reports every two years. “Today, High-Luminosity LHC due to deliver a radiation during a transatlantic flight. CERN has more than ever, science’s flag-bearers CERN’s Super erator R&D, dark-sector physics, and for The SPS is towards a potential electron–positron tenfold increase in luminosity towards A 2018 measurement campaign s et a for m a l need to demonstrate their relevance, (SPS) could be upgraded so that not electro-nuclear measurements for future one of Higgs factory. the end of the decade, CERN has made it showed that noise levels at CERN have objective that, their engagement, and their integration only protons have the possibility to be neutrino experiments. First proposed in CERN’s The SPS is one of CERN’s longest run- a priority to limit the increase in energy not changed since the early 1990s, and into society as a whole,” writes Gianotti. accelerated, but also electrons. A 173- 2018 by Torsten Åkesson of Lund Univer- ning accelerators, commissioned in June by 2024, direct longest consumption to 5% up to the end of 2024, are low by urban standards. Nevertheless, greenhouse “This report underlines our strong com- page conceptual design report for the sity and colleagues at CERN, the facility 1976 at an energy of 400 GeV and serv- with longer-term objectives to be set in CERN has have invested 0.7 million CHF mitment to environmental protection, “eSPS” posted on arXiv on 15 September would marry technology developed for running i n g nu m e r o u s fi x e d-t a r g e t e x p e r i m e nt s future reports. to reduce noise at its perimeters to below emissions will both in terms of minimising our impact describes the installation of a high- the proposed Compact Linear Collider accelerators ever since. It was later converted into CERN procures its electricity mainly 70 dB during the day and 60 dB at night be reduced and applying CERN technologies for envi- energy electron accelerator that could (CLIC) and the a proton– collider that was s from France, whose production capacity (which corresponds to the level of con- by 28% ronmental protection.” have the potential to be used for accel- (FCC), and could also provide a step used to discover the W and Z

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NEWS ANALYSIS NEWS ANALYSIS CERN-PHOTO-201902-032-12 in 1983. Then, in addition to its fi xed- r ne i lent Va M leaders of the Et-Wash group at the target programme, the SPS became part Weinberg ins niversity of Washington, “for precision of the injection chain for LEP, and most fundamental measurements that test recently, has been used to accelerate pro- reathrough rie our understanding of gravity, probe the tons for the LHC. nature of and establish limits Electrons would be injected into the ’s continuous leadership on couplings to dark matter”. Three New eSPS at an energy of 3.5 GeV by a new in particle physics, gravity and cosmol- Horizons in Physics Prizes, each worth compact high-gradient linac based on ogy was on 10 September rewarded with 100,000 and designed to recognise CLIC’s X-band radio-frequency (RF) cav- a Special in Funda- early-career researchers, were awarded it y t e c h n ol o g y, w h i c h w o u l d fi l l t h e c i r c u- mental Physics. While his contribution to Tracy Slatyer (IT) for major contri- lar machine with 200 ns-duration pulses to the genesis of the Standard odel has butions to particle astrophysics Rouven at a rate of 100 Hz. An additional 800 Hz undoubtedly been Weinberg’s greatest Essig (Stony Brook niversity), Javier superconducting RF system, similar to single achievement, stated the selection Tiff enberg (Fermilab), Tomer Volansky what is needed for FCC-ee, would then committee for the 3 million prize, he (Tel Aviv niversity) and Tien-Tien u accelerate the electron beam from 3.5 GeV would be recognised as a leader in the (niversity of Oregon) for advances in the to an extraction energy of 18 GeV. fi eld even if he had not made this par- detection of sub-GeV dark matter; and T h e r e q u i r e m e nt s o f t h e pr i m a r y e l e c- ticular contribution. oel says Weinberg, when invited to com- Ahmed Almheiri (IAS), Netta Engelhardt t r o n b e a m t o b e d e l i v e r e d b y t h e e SP S w e r e Worhorse Engineers in the tunnel during the urrent long shutdon of CERN’s aelerator omple. Weinberg’s 1967 paper “A odel of einberg is pare the awards, “but for me there was (M I T), He n r y M a x fi e l d (UC S a nt a B a r b a r a) determined by the needs of the proposed ” is one of the most pivotal in urrently the a special pleasure in being awarded the and Geoff Penington (UC Berkeley) for Light Dark Matter eXperiment (LDMX), ble second phase, complementing the r e s u lt o f w or k i n C E R N’s P h y s ic s B e y o n d theo retical physics. It applies the notion a oseyelh Breakthrough Prize because the selec- calculating the quantum information which would use missing- done by the AWAE collaboration. study. Were it to go ahead, the of spontaneous symmetry breaking to the oundation Chair tion committee is composed of a younger content of a and its radiation. techniques to explore potential cou- Positron production would be a crucial facility could be made operational in weak interaction, revealing that it is uni- in iene at the generation of outstanding physicists The Breakthrough Prize in Fundamen- plings between hidden-sector particles e l e m e nt for a n y f ut u r e H i g g s-f a c t or y a n d about fi ve years and would operate in fi e d w it h t h e e l e c t r o m a g n e t i c i nt e r a c t i o n niversity of eas who are today playing a leading role in tal Physics has been awarded annually and electrons. The facility could also it would also allow studies of the Low parallel and without interference with and predicts the existence of the W, and at ustin. research.” The prize committee also cited for the past nine years, while the Spe- provide multi-GeV drive beam bunches Emittance Accelerator (LEMMA) Run 4 of t he LHC, w rite t he aut hors. Higgs bosons (CERN Courier November Weinberg’s achievements in commu- cial Breakthrough Prize in Fundamental and electron witness bunches for – a novel scheme for obtaining a low- 2017 p25). The electroweak theory won nicating science and acknowledged his Physics has only been handed out on six wakefi eld . Positron witness emittance muon beam for a muon collider. urther reaing Weinberg, and Sheldon highly visible public role as a spokesman occasions. Last year, theorists Sergio bunches could be delivered in a possi- The eSPS proposal came about as a Aicheler et al. 2020 arXiv.org:2009.06938. Glashow the 1979 Nobel Prize in Physics. for science and rationality. Ferrara, Dan Freedman and Peter van “Of course, nothing compares with the Also worth 3 million, the 2021 Break- Nieuwenhuizen received a Special Break- Nobel Prize in prestige, if only because through Prize in Fundamental Physics through Prize for their 1976 invention of of the long history of great scientists to has been awarded to Eric Adelberger, . The 2021 prize ceremony whom it has been awarded in the past,” Jens H Gundlach and Blayne Heckel, the is due to take place in arch. How do you adapt lac holes attract Creative Commons 22 Nobel rie

the real world for The 2020 Nobel Prize in Physics, announced on 6 October, has recognised electromagnetics seminal achievements in the theoreti- cal and experimental understanding of black holes. One half of the SE 10 mil- ? lion (1.15 million) award went to Roger Penrose of the niversity of Oxford “for the discovery that black-hole forma- When the ultimate goal is to design more efficient tion is a robust prediction of the gen- Spacetie pioneers rom left Nobel inners Roger enrose ndrea he and Reinhard enel. and productive electronic devices, design engineers eral theory of relativity”. The other half need to run antenna measurements. If you know was awarded jointly to Andrea Ghez of But 50 years later, Penrose invented a matical physics with potential relevance what attributes of the real world are important, you t h e Un i v e r s it y o f C a l i for n i a, L o s A n g e l e s mathematical tool called a trapped sur- to the unifi cation of could instead test the designs with . and Reinhard Genzel of the ax Planck face to show that black holes are a natural and quantum mechanics, among many Institute for Extraterrestrial Physics “for consequence of general relativity, prov- other contributions. The COMSOL Multiphysics® software is used the discovery of a supermassive com- ing that they each hide a singularity. His “I really had to have a good idea of the for simulating designs, devices, and processes pact object at the centre of our galaxy”, groundbreaking article (hys. Rev. ett. space–time geometry. Not just 3D, you in all fields of engineering, manufacturing, and after the pair led separate research teams 57) is heralded as the fi rst post-Einstein- had to think of the whole 4D space–time during the 1990s to identify a black hole ian result in general relativity. I do most of my thinking in visual terms, scientific research. See how you can apply it to at the centre of the ilky Way. Penrose is also known for the “Penrose rather than writing down equations,” electromagnetics simulation. As soon as Einstein had completed his process”, whereby a particle–antiparticle said Penrose in an interview with the theory of general relativity in 1915, it was pair that forms close to the event horizon Nobel Foundation following the award. Visualization of the electric field comsol.blog/EM-simulations clear that solutions in the vicinity of a of a black hole can become separated, “Black holes have become more and more norm and far-field radiation pattern spherically symmetric, non-rotating with one of the two particles falling important, also in ways that people don’t of a biconical frame antenna. mass allow space–time to be “pinched” into the black hole and the other one normally appreciate. They are the basis of to a point, or singularity, where known escaping and carrying away energy and the second law of ou physics ceases to apply. Few people, angular momentum. He also proposed might ask where the greatest is in including Einstein himself, however, twistor theory, which has evolved into the universe – by an absolutely enormous thought that black holes really exist. a rich branch of theoretical and mathe- factor it is in black holes.”

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AstrowAtch OFF Pulsars hint at low-frequency gravitational waves

The direct detection of a gravitational mpion Cha D ALL ORDERS OF SHR AND NHR DEVICES wave (GW) in 2015 by the LIGO and Virgo FROM OCTOBER, 1ST TO DECEMBER, 31ST 2020* col labor at ions confir med t he e x istence of these long-sought-after events. How- ever, the kHz-regime GW events detected s o f a r c o n s t it ut e o n l y a s m a l l f r a c t i o n o f the vast GW spectrum. As a result, they only probe phenomena such as stellar mass black-hole and neutron-star mergers. On the opposite side of the spectrum to LIGO and Virgo are pulsar timing array (PTA) experiments, which search for nHz-frequency GWs. Such low-frequency signals can originate from supermassive black-hole binaries (SMBHBs), while in more exotic models t h e y c a n b e pr o o f o f c o s m i c s t r i n g s, p h a s e transitions or a primordial GW back- g r o u n d. T h e N A NO G r a v (Nor t h A m e r i c a n Nanohertz Observatory for Gravitational Waves) collaboration has now found pos- sible first hints of low-frequenc y GWs. PERFECT FOR USE Track and trace nHz waves NANOGrav uses variations in the arrival time of the signals from an array of very stable, quickly To detect such rumblings of space– rotating pulsars to detect potential distortions in space–time caused by low-frequency gravitational waves. WITH NHR – QUALITY time, which also have tiny amplitudes, NIM CRATES FROM researchers need to track subtle move- Researchers track spontaneously broken gauge symmetry ments of measurement points spread – that predict only a slightly different out over the galaxy. For this purpose, measurement points spread s p e c t r a l s h a p e. F u r t h e r m or e, a k e y i n g r e- the NANOGrav collaboration uses light dient is still missing: a spatial correla- from millisecond pulsars, several tens out over the galaxy tion between the pulsar variations, which of which have been detected in our gal- would confirm the quadrupole nature of a x y. P u l s a r s a r e q u ic k l y r o t a t i n g n e ut r o n GWs and provide clear proof of the nature s t a r s t h a t e m it c o n e s o f e l e c t r o m a g n e t i c the movement of Earth with respect to o f t h e s i g n a l. F i n d i n g t h i s “s m o k i n g g u n” DESIGNED FOR UNIVERSAL LABORATORY USE emission from their poles. When a pole t h e s o u r c e, a l l c h a n g e t h e a r r i v a l t i m e o f will require longer observation times, points towards Earth it is detected via a t h e p u l s e s. T h e c o m pl e x it y o f t h e m e a s- more pulsars and smaller systematic short pulse of electromagnetic radiation. u r e m e nt s l i e s m o s t l y i n c or r e c t i n g for a l l er rors – somet h i ng t he NA NOGr av team SHR Not only is the frequency of millisecond of these effects. The latest results from is now working towards. ALSO AVAILABLE pulsars high, making it easier to detect NANOGrav, for example, reduce system- AS NIM-DEVICE: ULTRA PRECISE small variations in arrival time, but it is atics by incorporating unprecedented Bright and beautiful very stable over periods of many years. precision (of the order of tens of km) in Several exotic interpretations have also C o m bi n e d w it h t h e i r g r e a t d i s t a n c e s f r o m the orbital parameters of Jupiter. been proposed, though the NANOGrav NHR SOURCE MEASURE UNIT Earth, this makes millisecond-pulsar Whereas previous results by NANOGrav collaboration remains cautious. The emissions sensitive to any small alter- a n d o t h e r P TA c ol l a b or a t i o n s o n l y a l l o w e d final sentences of their preprint sum- ations in their travel path – for exam- upper limits to be set on the amplitude of marise the status of the field well: “The 2 / 4 channels, 2 kV / 6 kV versions ple, those introduced by distortions of the GW background travelling through L IG O –V i r g o d i s c o v e r y o f h i g h-f r e q u e n c y, space–time by low-frequency gravita- our galax y, the new results show a clear transient GWs from stellar black-hole Electronically switchable polarity tional waves. Such waves would cause the sign of a common spectrum between binaries appeared meteorically, with pulses to arrive a few nanoseconds early the studied pulsars. Based on 12.5 years incontrovertible statistical signifi- 6 kV channel with electronically switchable modes: up to 2 kV/4 mA, 4 kV/3 mA or 6 kV/2 mA during January and a few nanoseconds of data and a total of 47 pulsars stud- cance. By contrast, the PTA discovery late in June, for instance. By observing ied using the ultra-sensitive Arecibo of very-low-frequency GWs from SMB- High-precision / very low ripple and noise / high resolution t h e r a d io e m i s s i o n o f t h e s e o bj e c t s o n c e a Observatory and Green Bank Telescope, HBs will emerge from the gradual and w e e k t h r o u g h o ut m a n y y e a r s, r e s e a r c h e r s the spectrum of variations in the pulsar not always monotonic accumulation of USB / Ethernet** interface can searc h for suc h effects. signal arrival time was found to agree evidence and arguments. Still, our GW The problem is that GWs are not the with theoretical predictions of the GW vista on the unseen universe continues Integrated (ARM Linux server hardware) with onboard scripting** only things that can cause a change in background produced by SMBHBs. The to get brighter.” the arrival time of the pulses. Changes u n c e r t a i nt i e s r e m a i n l a r g e, h o w e v e r. T h i s 4.3“ TFT capacitive touch display (SHR) i n t h e E a r t h’s a t m o s p h e r e i n t h e p o s it io n admits alternative interpretations such Further reading of the pulsar itself (which is usually part as cosmic strings – domain structures NANOGrav Collaboration 2020 *This offer is applicable through iseg and participating sales partners. Offer cannot be combined with other offers / quantity discounts o f a q u i c k l y r o t a t i n g bi n a r y s y s t e m), a n d in the universe predicted to arise from a arXiv.org:2009.04496. and not applicable for frame contracts. Only applicable to qualified SHR and NHR devices. Feel free to ask iseg support team or your participating local iseg sales partner for more information. **SHR-device only

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Unstable sterile neutrinos Green light for Science Gateway 37 205011). Einstein’s general with a mass of 10 MeV could Local authorities in Geneva theory of relativity allows for account for the needed 40% of in September approved the closed time-like curves (CTCs) C Chang/ArgonneC an effect ive neut rino flavour, construction of the Science wherein a worldline returns to they claim. Though potentially Gateway – a new education its star t ing point, provok ing oscillating far too fast to be and outreach facility at CERN possible logical headaches such seen by conventional sterile- designed by Renzo Piano’s as the grandfather paradox. The neut rino searc hes, t he aut hors arc hitect ure fir m to evoke pair serve up maths in support of suggest that simple models could the twin beam pipes of the the view that complex dynamics be within the reach of Japan’s LHC. Linked by a centrepiece is possible in the presence of Super-Kamiokande detector or CTCs, compat ible w it h t he

the NA62 experiment at CERN RPBW free choice of local operations (arXiv:1906.10136). without inconsistency. A prototype wafer for the CMB-S4 telescopes. Snowmass limbers up Brushing up on Raphael A virtual community planning Czech start-up InsightArt Berkeley to CMB-S4 meeting for the 2021 Snowmass has used photon detectors The US Department of Energy in exercise, which will plot a developed by CERN’s Medipix September selected Lawrence course for US particle physics An artist’s impression of the project to dismiss a century of Berkeley National Laboratory over the coming decade, took Science Gateway facility. tittle-tattle impugning Raphael to lead the proposed Cosmic place from 5 to 8 October. The as the true artist behind the Microwave Background Stage 4 meeting attracted some 3000 bridge, t he new spaces w ill painting of the Madonna and (CMB-S4) experiment. CMB-S4 participants and more than house exhibitions, laboratories Child commissioned by Leo X aims to survey the 1500 letters of intent across 10 and educational activities, in 1517. Since t he early 1990s, and polarisation of the CMB in “Snowmass frontiers”, from the surrounded by 400 newly planted Medipix collaborators have IOP - CERN.indd 1 24/02/2020 14:50 unprecedented detail using a mix energy frontier to community t rees. 80% of t he total budget, developed the “colour X-ray”

of large and small telescopes at engagement. First convened which will be entirely funded by InsightArt the South Pole and in the high in the eponymous Coloradoan donations, has been secured. Chilean desert. Researchers will mountain resort in 1982, The facility is due to be open at look for signs of inflation, seek to Snowmass studies have been the end of 2022. measure t he mass of t he neut r i no, produced on numerous occasions constrain dark-sector models t hroughout t he years, most APS recognises black history and aid in the detection and study recent ly in 2013. A final repor t Baltimore’s Morgan State of gamma-ray bursts and jet- will be published in October 2021. University (MSU) and the emitting blazars. If approved, Sanford Underground Research CMB-S4 will follow in the milestone Facility (SURF) have been footsteps of Penzias and Wilson’s Engineers at Energy designated historic sites by the ground-based measurements of have come within a whisker American Physical Society (APS). the CMB in 1964 and the COBE, (0.2 T) of the world-record field MSU was the birthplace in 1977 WMAP and Planck . The for a magnet based on high- of the National Society of Black first telescopes may be deployed temperature superconductors Physicists, and has worked to as early as 2027. (HTS). The UK company, which increase the representation of pursues “desktop” fusion African Americans in physics Sterile neutrinos to the rescue? reactors, teamed up with CERN’s and technology ever since. Raphael’s Madonna and Child. A University of California trio cryolab to cool a to 4 K SURF was home to Ray Davis’s points to sterile neutrinos as a and ramp it up to 26.2 T over the Homestake experiment, which for a w ide range of applicat ions, possible explanation for the ~5σ course of a few days in September. uncovered the solar-neutrino in t his case different iat ing discrepancy in measurements Similar technology could also be problem. The sites join 48 others brushstrokes and pigments. A of the Hubble constant at reconfigured for future particle on the APS list. group of independent experts small and large scales. The accelerators, potentially offering used eleven 50 μm-resolution presence of an additional fields up to 30 T, in excess of the Time travel without paradoxes scans at different w aveleng t hs

neutrino-like particle that 16 T Nb3Sn magnets envisaged University of Queensland to establish that the work was decayed just before Big-Bang by the baseline FCC-hh design. theorist Fabio Costa and student painted by Raphael personally, nucleosynthesis could explain CERN magnet engineers will Germain Tobar have delighted without the help of apprentices. why the microwave sky appears shortly use HTS to boost the field sci-fi fans worldw ide w it h The painting was stolen from Sn ,, ,.... to be expanding more slowly of the experimental 14.6 T Nb3 claims that free will can be the Holy See by Napoleon’s "' than suggested by observations FRESCA2 magnet to just maintained when travelling back ar mies in 1798, before being of Cepheid variables and Type-Ia under 20 T – a record field for a in time and interacting with sold into private property by supernovae, say the authors. dipole magnet. yourself (Class. Quantum Grav. Louis XVIII in 1813. -2 -1 0 1 2 3 Input Power {dBm)

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YOUR OPTICS, OUR FOCUS ENERGY At Inrad Optics, we make bent-crystal monochromator applications not just possible—but practical. FRONTIERS

Reports from the Large Hadron Collider experiments Thanks to our state-of-the-art optical manufacturing and testing methods, our bent-crystal monochromators LHCb are opening new doors in analytical chemistry micro- probes, hot plasma diagnostics, black-lighter imaging – In pursuit of right-handed photons and more. Grown from high quality crystalline material, On 17 January 1957, a few months after measurement using virtual photons our analyzers are designed to optimize the diffraction Chien-Shiung Wu’s discovery of parity 1.0 and the largest sample of the very rare efficiency of your imaging system. violation, Wolfgang Pauli wrote to Vic- B0 → K*0e+e– decay ever collected. First, Recirc-cryo-IOP 8/9/18 5:40 PM Page 1 tor Weisskopf: “Ich glaube aber nicht, daß the sub-sample of decays that come from • Toroids, ellipsoids, cylinders, and aspheres der Herrgott ein schwacher Linkshänder ist” B0 → K*0γ with a virtual photon that mat- 0.5 • Silicon, germanium, quartz, and KAP crystals (I cannot believe that God is a weak left- erialises in an electron–positron pair is hander). But maximal parity violation is isolated. The angular distributions of the • Crystal planes oriented to ±2 arc-sec 0 *0 + –

now well established within the Standard ) B → K e e decay products are then used 7 • High vacuum compatibility, no outgassing Model (SM). The weak interaction only SM as a polarimeter to measure the handed- /C ʹ

7 0.0 • Uniform performance from unit to unit couples to left-handed particles, as dra- ness of the photon. The number of decays

matically seen in the continuing absence Im (C with a virtual photon is small compared of experimental evidence for right-handed to the decays with a real photon, but these global neutrinos. In the same way, the polarisa- –0.5 latter decays cannot be used as the infor- tion of photons originating from transi- β(B → Xsγ) mation on the polarisation is lost. 0 0 0 tions that involve the weak interaction is B → Ksπ γ The size of the right-handed contribu- 0 expected to be completely left-handed. Bs → φγ tion to b → sγ is encoded in the magnitude B0 → K*0 e+e– The LHCb collaboration recently tested –1.0 of the complex parameter C′7/C7. This is To learn more, visit www.inradoptics.com/products/x-ray-imaging-crystals the handedness of photons emitted in –1.0 –0.5 0.0 0.5 1.0 a ratio of the right- and left-handed r a r e fl a v o u r- c h a n g i n g t r a n s it i o n s f r o ma Wilson coefficients that are used in the Re (C7ʹ/C7) b- to an s-quark. These are medi- e ffe c t i v e d e s c r i p t i o n o fb → s transitions. ated by the bosons of the weak interaction The new B0 → K*0e+e– analysis by the LHCb according to the SM – but what if new Fig. 1. 2σ constraints found to agree with the SM prediction, collaboration constrains the value of

virtual particles contribute too? Their on the ratio of which bears a similar theoretical uncer- C′7/C7, and thus the photon polarisation, presence could be clearly signalled by right- and tainty. A promising way to go further is w it h u n pr e c e d e nt e d pr e c i s i o n (fi g u r e 1). a right-handed contribution to the left-handed Wilson to study the polarisation of the emitted The measurement is compatible with the

photon polarisation. coefficients, 7C′/C7, photon. Measuring the b → sγ polari- SM prediction. Recirculating Cryocooler The b → sγ transition is rare. Fewer than using the flavio sation is not easy though. The emitted This result showcases the exceptional one in a thousand b- transform software package. photons are too energetic to be analysed capability of the LHCb experiment to

Eliminates the use of LHe for into an s-quark and a photon. This process C7 quantifies the by a polarimeter and physicists must find study b → sγ transitions. The uncertainty “Wet” Systems has been studied for almost 30 years at coupling strength to innovative ways to probe them indirectly. is currently dominated by the data sam- particle colliders around the world. By photons, and is fixed For example, a right-handed polarisation ple size, and thus more accurate studies precise measurements of its properties, to its SM value. Any contribution could induce a charge-par- are foreseen with the large data sample 0 0 physicists hope to detect hints of new deviation in C′7/C7, ity asymmetry in the B → K Sπ γ or expected in Run 3 of the LHC. More pre- 0 heavy particles that current colliders are from (0,0) would Bs → φ γ decays. It could also contribute cise measurements may yet unravel a not powerful enough to produce. signify new physics. to the total rate of radiative b → sγ decays, small right-handed polarisation.

The probability of this b-quark decay The new LHCb containing any strange meson, B → Xs γ. has been measured in previous experi- measurement is The LHCb collaboration has pio- Further reading Existing LHe cooled ments with a precision of about 5%, and shown in red. neered a new method to perform this LHCb Collab. 2020 arXiv:2010.06011. cryostats and probe s t a t i o n s can be CMS programme since the beginning, and The pursuit of gauge bosons are flavour independent. converted to cryogen-free operation with Leptoquarks and have received additional attention this promising This principle is built into the SM, but has recently in the light of hints of deviations recently been put under stress by a series the addition of an external cryocooler, the solution for Janis Recirculating Gas Cryocooler (RGC4). the third generation from the principle of universality of anomalies observed in precision meas- – t he so-called flavour anomalies. the unification urements of certain B-meson decays by Instead of using LHe from a storage The (SM) groups quarks In a recent CMS analysis, where the of quarks and the LHCb, Belle and BaBar collaborations vessel, the RGC4 delivers a stream of 4K and leptons separately to account for events collected in pp collisions during leptons must (CER N Courier May/June 2019 p33). A pos- helium to the cryostat or probe station. –1 their rather different observed proper- Run 2 (137 fb ) are analysed, researchers continue sible explanation for these anomalies, Contact Janis today for more information. ties, but might they be unified through have challenged the SM by investigating which are still under investigation and a new particle that couples to both and a previously unexplored leptoquark sig- not yet confirmed, lies in the existence turns one into the other? Such “lep- nature involving the third generation of of leptoquarks that preferentially couple ContactContact usus today: toquarks” emerge quite naturally in . The motivation for considering to the heaviest fermions. [email protected] [email protected] several theo ries that extend the SM. the third generation is to confront the The new CMS search looks for both sin- www.janis.com/RecirculatingCryocooler.aspx Searches for leptoquarks have been an principle of lepton universality, which gle and of leptoquarks. It www.lakeshore.com/RGC s www.facebook.com/JanisResearch important part of the LHC’s research asserts that the couplings of leptons with considers leptoquarks that decay to a

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ENERGY FRONTIERS ENERGY FRONTIERS

quark (top or bottom) and a lepton (tau or quark–lepton flavour pairs, for exam- any significant signal would indicate plementary to direct-detection exper- The art of new phenomena. ATLAS will continue –1 neutrino), targeting the signature with a CMS preliminary 137 fb (13 TeV) ple, in the case of a spin-1 leptoquark, to new physics. No deviation from the iments looking for relic WIMPs with to explore the parameter space of 2.5 this analysis , a tau lepton, missing transverse preferred by B-anomalies (95% CL) a top quark and a neutrino, or to a bot- SM was observed, allowing a 95% con- deep underground detectors, as they is in the dark-sector models such at ALPs, dark momentum due to a neutrino, and, in the Obs. (95% CL) LQ LQ + LQ = 1 tom quark and a tau lepton. CMS finds a fidence upper limit to be placed on plumb lower WIMP than photons, dark scalars and heavy neutral V V τ V κ precise case of double production, an additional Exp. (95% CL) LQV LQV + τLQV κ = 1 range of lower limits on the leptoquark the branching fraction for invisible direct-detection experiments can leptons, complementing the results of 2.0 bottom-quark jet. This is the first search Obs. (95% CL) LQV LQV κ = 1 mass between 0.98 and 1.73 TeV, at 95% Higgs-boson decays of 13% – a factor cur rent ly access (fig ure 2). modelling dedicated smaller-scale experiments. Exp. (95% CL) LQ LQ = 1 to simultaneously consider both produc- V V κ confidence, depending onλ and the spin. two improvement in sensitivity com- These results also translate into lim- of SM Obs. (95% CL) LQ = 1 tion mechanisms by categorising events τ V κ These results are the most stringent pared to the previous analysis, despite its on alternative dark-matter-related backgrounds Further reading Exp. (95% CL) τLQV κ = 1 with one or two jets originating from a 1.5 limits to date on the presence of lep- the increase in pileup – or 9% when com- theories such as axion-like-particles ATLAS Collab. 2020 ATLAS-CONF-2020-048. bottom quark. The analysis also includes toquarks that couple preferentially to bining with other ATLAS Higgs-boson (ALPs) and large extra-dimensions, ATLAS Collab. 2020 ATLAS-CONF-2020-008. λ a dedicated selection for the case of a large the third generation of fermions. They measurements. The results are com- and into model-independent limits on ATLAS Collab. 2020 ATLAS-CONF-2020-027. mass splitting between the leptoquark 1.0 also probe the parameter space preferred and the top quark, which would boost the by the B-physics anomalies in several ALICE top quark and could cause its decay prod- models, excluding relevant portions. As ucts to be inseparable given the spatial theories predict leptoquark masses as 0.5 Fragile light nuclei flow through freeze-out resolution of jets. high as many tens of TeV, the pursuit of The observations are found to be in t h i s pr o m i s i n g s olut i o n for t h e u n i fic a t i o n 0.6 0.6 agreement with the SM prediction, and of quarks and leptons must continue. The Pb–Pb √sNN = 5.02 TeV Pb–Pb √sNN = 5.02 TeV Pb–Pb √sNN = 5.02 TeV exclusion limits are derived in the plane 0 C M S c ol l a b or a t io n h a s a br o a d pr o g r a m m e 0.5 π± ALICE ALICE 0.4 ALICE ± 0.5 of the leptoquark–lepton–quark vertex 0.6 0.8 1.01.2 1.4 1.6 1.8 2.0 2.2 for further investigations that will exploit K 20–40% 20–40% 20–40% coupling λ and the leptoquark mass. m [TeV] the larger data samples from Run 3 and p + p LQ 0.4 0.4 d + d 0.3 d + d The results are derived separately for t h e h i g h-lu m i n o s it y L HC u n d e r d i ffe r e nt d + d coalescence coalescence 3 3 hypothetical spin-0 and spin-1 (figure Fig. 1. 95% confidence limits on the mass and coupling of a spin-1 hypotheses. If leptoquarks exist, they may 0.3 He + He blast-wave v 0.3 0.2 1) leptoquarks, reflecting the two types (vector) leptoquark (LQV), considering single (orange) and pair well be revealed in the coming data. 2 v2 v3 a l l o w e d b y t h e or e t ic a l m o d e l s. T h e a n a l y- (purple) production mechanisms, and their combination (blue), 0.2 0.2 sis assumes that the leptoquark decays compared to the region favoured by models seeking to explain the Further reading 0.1 half the time to each of the possible B-physics anomalies (yellow). The regions to the left are excluded. CMS Collab. 2020 CMS-PAS-EXO-19-015. 0.1 0.1 ATLAS Fig. 1. Monojet missing transverse 0 0 ATLAS preliminary data Standard Model w. unc. momentum compared to SM predictions, 0 –1 Cornering WIMPs √s = 13 TeV, 139 fb Z(→ νν) + jets 6 and the distributions of illustrative 10 signal region – post fit VBF Z(→ II/νν) + jets 01234 56 01234 56 012 34 56 W(→ Iν) + jets supersymmetric (purple dashed line), with ATLAS p (j ) > 150 GeV pT [GeV/c] pT [GeV/c] pT [GeV/c] T 1 VBF W(→ Iν) + jets _ WIMP (blue dashed line) and dark-energy 4 tt + single top 10 diboson (black dashed line) signals. Dark matter is estimated to account for multijet + NCB Ultra-relativistic heavy-ion collisions Fig. 1. The elliptic nuclei production with respect to the cence model predicts that light nuclei are m(t, χ~~ 0 ) = (600, 580) GeV an unseen 85% of matter in the universe, o t h e r b a c k g r o u n d s b e n e fit t e d f r o m s t a te- create a system of deconfined quarks flow of deuterons, symmetry plane of the collision are key formed by the coalescence of protons and events/GeV 2 10 m(χ, ZA ) = (1, 2000) GeV but its nature is unknown. One possi- DE, M2 = 1558 GeV of-the-art theoretical calculations, and known as the quark– compared with observables to study interactions in the that are close in phase space at ble explanation is weakly-interacting detailed groundwork on particle plasma (QGP). Among other particles, a other species hadron-gas phase, and can shed light on the kinetic freeze-out – the time at which massive particles, or WIMPs, which 1 reconstruction in ATLAS, and the use large number of light nuclei such as the (left) and the production mechanism of these frag- elastic interactions cease. The blast-wave could interact with ordinary matter 1.2 of data-control regions rich in W and Z deuteron, triton, helium-3, helium-4 and phenomenological ile objects. The ALICE collaboration has model, which is based on a simplified through the exchange of a Higgs boson b o s o n d e c a y s. No s i g n i fic a nt e x c e s s w as their corresponding antinuclei are pro- models (middle), recently reported the measurements of version of relativistic hydrodynamics, 1.0 (“Higgs-portal” models) or a new medi- observed with respect to the Standard duced, and can be measured with very and their triangular t w o h a r m o n ic c o e ffic ie nt s (v n) in a Fourier describes their transverse momentum stat. + syst. uncertainties a t or fie l d y e t t o b e d i s c o v e r e d. T h e AT LAS data/SM 0.8 Model (SM) (fig ure 1). good precision by the ALICE experiment flow (right), in decomposition of the azimuthal distri- spectra with just a few parameters, such collaboration has recently released two 200 400 600 800 1000 1200 A second “dijet” WIMP analysis at the LHC thanks to its excellent tracking Pb–Pb collisions at bution of deuterons in Pb–Pb collisions at as the kinetic freeze-out new investigations of WIMPs based on precoil [GeV] searches for invisible decays of Higgs and particle-identification capabilities via √sNN = 5.02 TeV in √sNN = 5.02 TeV: their elliptic flow, 2v , and and transverse velocity. the full Run-2 data set. T bosons produced via vector-boson specific energy loss and time-of-flight the centrality class t h e fi r s t m e a s u r e m e nt o f t h e i r t r i a n g u lar In the new ALICE results, the measured

At the LHC, a mediator may be pro- f u s ion. Thoug h a c c ou nt i n g for ju s t 10% measurements. Considering that the 20–40%. flo w, v 3. A clear mass ordering is observed elliptic flow of light nuclei is bracketed duced and decay into a pair of stable as many Higgs bosons as the dominant binding of light (anti)nuclei do in the elliptic flow of non-central Pb–Pb by the simple coalescence approach and WIMPs, which then escape the detec- B < 0.11 ATLAS preliminary gluon-fusion process at the LHC, the not exceed a few MeV, it is not clear how collisions at low p when the deuteron the blast-wave model, which describe the –39 inv T tor unseen – an undetectable process, 10 all limits at 90% CL √s = 13 TeV, 139 fb–1 topology’s clear signature, with two such fragile objects can survive the hadron results are compared with other particle data in different multiplicity regimes (fig- unless the mediator is produced, for Higgs portal widely separated jets in pseudorapid- gas phase created after the phase transi- species, as expected for an expanding ure 1, middle). The deuteron triangular

] other experiments 2 –41 scalar WIMP DarkSide-50 example, in association with a high-pT 10 ity, lends itself to searching for MET, tion from the QGP to , where par- hydrody namic system (fig ure 1, lef t). flow is consistent with the coalescence Majorana WIMP LUX gluon radiated from one of the incom- [cm as the jets tend to be close together in ticles rescatter with a typical momentum The results are often compared to three model predictions, but large uncertain- PandaX-II ing protons. This would provide a clear the transverse plane when recoiling transfer in excess of 100 MeV. The produc- phenomenological models, namely the ties do not allow a conclusive statement 10–43 Xenon1T signature: a high-pT jet and significant against a Higgs boson with pT > 200 G eV. tion mechanism of light (anti)nuclei in statistical hadronisation model, the (fig ure 1, right). This specific aspect w ill

missing transverse momentum (MET). WIMP- The art of this analysis is again in the these collisions is still not understood and coalescence model, and the blast-wave be addressed with the larger data sample σ –45 A fi r s t “m o n oj e t” a n a l y s i s s o u g ht e v e nts 10 precise modelling of SM backgrounds is under intense debate in the scientific model. In the statistical hadronisation that ALICE will record in Run 3, which with MET in excess of 200 G eV, r e c oi l i n g – a feat accomplished here with extrap- community. Constraining models of light model, light (anti)nuclei are assumed to be w ill also allow measurement of t he flow against a jet with pT > 150 GeV, with up 10–47 olations from control regions and the antinuclei production is also important emitted by a source of thermal and hydro- of heavier nuclei. These results will con- to three additional jets and no leptons 1 10 102 103 104 use of jet kinematics to separate signal for predicting the backgrounds to indirect chemical equilibrium, like other hadron tribute to shed light on their production or photons. The leading background events from Z-boson decays to neutri- dark-matter searches using cosmic rays, species, and their abundances fixed at the mechanism and to study the properties mWIMP [GeV] arises from events wherein a Z boson nos, and W decays with an undetected as performed by experiments in space and chemical freeze-out – the time at which of the hadron gas phase. decays to neutrinos – a process experi- Fig. 2. 90% confidence upper limits on the elastic WIMP-neutron c h a r g e d l e p t o n. A s i n v i s i bl e H i g g s-b o s o n in hot-air balloons, for which light anti- inelastic interactions cease. However, this mentally indistinguishable from WIMP scattering cross section as a function of the mass of a scalar decays in the SM (chiefly H → ZZ* → 4ν) nuclei are promising signals. model only describes their yields, and not Further reading s production. The predictions of this and (purple) or spin-½ Majorana (red) WIMP. have a branching fraction of just 10–3, Azimuthal anisotropies of light (anti) t h e i r flo w. O n t h e o t h e r h a n d, t h e c oales- ALICE Collab. 2020 arXiv:2005.14639.

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CCNovDec20_EnergyFrontiers_v2.indd 18 20/10/2020 16:28 CCNovDec20_EnergyFrontiers_v2.indd 19 20/10/2020 16:29 CERNCOURIER www. V o l u m e 6 0 N u m b e r 6 N o v e mber /D e c e m b e r 2 0 2 0 CERNCOURIER.COM SUPERCON, Inc. FIELD Superconducting Wire Products NOTES Standard and Specialty designs are available to meet your most demanding superconductor requirements. Reports from events, conferences and meetings SUPERCON, Inc. has been producing niobium-based superconducting wires and cables for 58 years. FIPs 2020 We are the original SUPERCON – the world’s first commercial producer of niobium-alloy based wire and cable for superconducting applications. Strong interest in feeble interactions

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Scaling the ALPs Searches for axion-like particles (ALPs) at helioscopes, haloscopes and accelerators span more than 18 orders of magnitude in mass and 16 orders of magnitude in the coupling of axions to photons (left image), with the accelerator experiments investigating high masses and stronger couplings (see zoom image, right). The regions excluded at 90% confidence are plotted alongside a strip favoured by mainstream theoretical models (gold) and a range of potential astrophysical sources. The estimated future sensitivities are indicated by the dashed regions.

Since the discovery of the Higgs boson Rayner G Lanfranchi/M in 2012, great progress has been made in strong CP problem our understanding of the Standard Model (SM) and the prospects for the discovery flavour puzzle axion/ALP DESY of new physics beyond it. Despite excel- lent advances in Higgs-sector measure- SNOLAB SLAC dark matter PSI ments, searches for WIMP dark matter Gran Sasso dark photon Mainz and exploration of very rare processes in Frascati JPARC (K) CERN neutrino masses JLAB t h e fl a v o u r r e a l m, h o w e v e r, n o u n a m big- Fermilab uous signals of new fundamental phys- dark scalar EW symmetry breaking ics have been seen. This is the reason behind the explosion of interest in feebly hierarchy of scales heavy neutral lepton JPARC (ν) interacting particles (FIPs) over the past decade or so. matter– asymmetry The inaugural FIPs 2020 workshop, hosted online by CERN from 31 August to 4 September, convened almost 200 Four portals A selection of open questions in particle physics, their possible links to FIPs, and a broad-brush physicists from around the world. Struc- overview of the research avenues being pursued at laboratories worldwide. tured around the four “portals” that may l i n k S M p a r t ic l e s a n d fie l d s t o a r ic h d ark e ffor t s a r e d r i v e n b y a r g u m e nt s b a s edon to a rich dark sector and answer many sector – axions, dark photons, dark the naturalness of the electroweak scale. open questions in particle physics (see scalars and heavy neutral leptons – the They result in searches for new parti- “Fo u r p or t a l s” fi g u r e). D i v e r s e s e a r c h es workshop highlighted the synergies and cles with sizeable couplings to the SM, using proton beams (CERN and Fermilab), complementarities among a great vari- and masses near the electroweak scale. beams (CERN and JPARC), neutrino ety of experimental facilities, and called FIPs represent an alternative paradigm beams (JPARC and Fermilab) and muon for close collaboration across different to the traditional beyond-the-SM physics beams (PSI) today join more idiosyncratic physics communities. explored at the LHC. With masses below experiments across the globe in a world- s Today, conventional experimental the electroweak scale, FIPs could belong wide search for FIPs.

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FIELD NOTES FIELD NOTES

FIPs can arise from the presence of Exotic Higgs be stabilised dynamically via the time microwave cavity placed inside a strong e x plain t he ot her flavour anomalies. studies. In the electron–positron domain, Recent these ongoing and future facilities to feeble couplings in the interactions of bosons could e v olut io n o f a s o - c a l l e d “r e l a x io n” fie l d. , will complement this R e c e nt i m pr e s s i v e r e s u l t s w e r e s h o w n Belle II will continue to accumulate data, impressive the maximum. Flavour studies have a new physics with SM particles and fields. They could also have been responsible for quest by increasing the sensitivity for i n t h e fie l d o f C P v i ol a t i o n. L HC b pr e s e nted also have been and there is the exciting possibility of results were br i g ht f ut u r e, a n d t h e y a r e s u r e t o r e t a i n These may be due to a dimensionless cosmological inflation. small couplings by six orders of mag- the first ever observation of time-de- a super-tau-charm factory, situated in a central role in our search for physics responsible for shown in or to a “dimension- Finally, consider right-handed neutri- nitude (down to the theoretically moti- p e n d e nt C P v i ol a t i o n i n t h e B s s y s t e m – a either China or Russia, which will collect beyond the SM. ful” scale, larger than that of the pro- cosmological nos, often referred to as sterile neutrinos vated gold band in a mass region where phenomenon that has eluded previous very large data sets at lower energies. the field of cess being studied, which is defined by a inflation or heavy neutral leptons, which could the axions can be a dark-matter candi- experiments on account of the very fast T h e s e pr o s p e c t s w e r e s u r v e y e d b y P h i l l i p CP violation Robert Fleischer Nikhef and Vrije 12 higher dimension operator that mediates account for the origin of the tiny, near- date). Accelerator-based experiments, (a rate of about 3 × 10 Hz) B s oscillations Ur q u ij o (Un i v e r s it y o f M e l b o u r n e) i n t h e Universiteit Amsterdam, Guy Wilkinson the interaction. The smallness of these ly-degenerate masses of the neutrinos of meanwhile, can probe the strongly moti- and inadequate sample sizes. In addi- summary talk of the conference, who and Takeo Higuchi Anz_spec_CERN_10-2020_sp 14.10.20 17:27 Seite 1 couplings can be due to the presence of the SM and their oscillations, as well as vated QCD scale (MeV–GeV) and beyond tion, new LHCb results were shown for stressed the importance of exploiting Kavli IPMU, University of Tokyo. an approximate symmetry that is only providing a mechanism for our universe’s for larger couplings. All these results the CP-violating phase γ. The most pre- slightly broken, or to the presence of a matter–antimatter asymmetry. will be complemented by a lively theo- cise of these comes from an analysis that large mass hierarchy between particles, retical activity aimed at interpreting isolates B → DK d e c a y s w h i c h a r e fol l o w e d + – as the absence of new-physics signals Scientific diversity astrophysical signals within axion and by D → KSπ π decays, and the distribu- Multi-channel from direct and indirect searches seems No single experimental approach can ALP models. tions of the final-state particles compared to suggest. cover the large parameter space of FIPs 2020 triggered lively discus- depending on whether they originate from AWG + Digitizer Take the axion, for example. This is masses and couplings that FIPs models sions that will continue in the coming B– or B + mesons. This analysis is based the particle that may be responsible allow. The interconnections between months via topical meetings on dif- on t he f ull Run 1 and Run 2 data sets and in one box! for the conservation of charge–parity open questions require that we con- ferent subjects. Topics that motivated constrains γ t o a pr e c i s io n o f fi v e d e g r e e s, s y m m e t r y i n s t r o n g i nt e r a c t i o n s. It m a y struct a diverse research programme particular interest between communi- which from this single analysis alone rep- also constitute a fraction or the entirety incorporating , ties included possible ways of comparing resents around a four-fold improvement of dark matter, or explain the hierarchical dark-matter direct detection, cosmol- results from direct-detection dark- c o m p a r e d t o w h e n t h e L HC b e g a n o p e r a- masses and mixings of the SM fermions ogy, astrophysics, and precision atomic matter experiments in the MeV– t i o n. F u r t h e r i m pr o v e m e nt s a r e e x p e c t e d – t he flavour puzzle. experiments, with a strong theoretical GeV range against those obtained over t he coming years. Model with 8+8 channels (DN2.80x-08) Or take dark photons or dark Z′ bos- i n v ol v e m e nt. T h e br e a d t h o f s e a r c h e s for at extracted beam line and collider Participants were eager to learn about ons, both examples of new vector gauge axions or axion-like particles (ALPs) is a experiments; the connection between t h e pr o g r e s s o f t h e S u p e rK E K B a c c e l e r a t or X bosons. Such particles are associated good indication of the growing interest right-handed neutrino properties and and Belle II experiment. SuperKEKB is now with extensions of the SM gauge group, i n F I P s (s e e “S c a l i n g t h e A L P s” fi g u r e). active neutrino parameters; and the operating at higher luminosity than any and, in addition to indicating new Experimental efforts here span particle interpretation of astrophysical and pr e v i o u s e l e c t r o n–p o s it r o n m a c h i n e, a n d beyond the four we know, could lead to a n d a s t r o p a r t i c l e p h y s i c s. I n t h e c o m i n g cosmological bounds, which often the data set collected by Belle II (of the order evidence of dark-matter candidates with years, helioscopes, which aim to detect overwhelm the interpretation of each 100 fb–1) is already sufficient to demon- thermal origins and masses in the MeV solar axions by their conversion into of t he four por tals. strate t he capabilit ies of t he detector and to GeV range. photons (X-rays) in a strong magnetic The next FIPs workshop will take place t o a l l o w for i m p or t a nt e a rl y p h y s ic s s t u d- NETBO Then there are exotic Higgs bosons. field, will improve the sensitivity by at CERN next year. ies, which were shown during the week. Light dark scalar or pseudoscalar parti- more than 10 orders of magnitude in Belle II has superior performance to the cles related to the SM Higgs may provide m a s s i n t h e s u b - eV r a n g e. H a l o s c o p e s, James Beacham Duke University, first-generation B-factory experiments, novel ways of addressing the hierarchy which work by converting axions Albert de Roeck CERN and BaBar and Belle, in areas such as flavour problem, in which the Higgs mass can into visible photons inside a resonant Gaia Lanfranchi INFN. tagging and proper-time resolution, and Model with 4+4 channels (DN2.81x-04) w i l l c ol l e c t a r o u n d 50 t i m e s t h e i nt e g r a t e d NEW! Beauty 2020 lu m i n o s it y. B y t h e e n d o f t h e d e c a d e B e l l e II hybrid w i l l h a v e a c c u m u l a t e d 50 ab–1 o f d a t a, f r o m wh ic h ma ny prec ise a nd e xc it i ng physics Heav y-f lavour high lights from Beaut y 2020 measurements are expected. Studies of kaon decays provide impor- Model with 2+2 channels (DN2.81x-02) The international conference devoted to into pairs of leptons and accompanying t a nt i n s i g ht s i nt o fl a v o u r p h y s i c s t h a t a re b-hadron physics at frontier , ATLAS, CMS, LHCb – summer 2020 hadrons are particularly tantalising, as complementary to those obtained from 0.6 Digitizer and AWG in one instrument Beauty 2020, took place from 21 to 24 preliminary 2011–2016 data they show significant deviations from the b-hadrons. The NA62 collaboration pre- September, hosted virtually by Kavli ATLAS/CMS/LHCb 0.5 SM in a manner that could be explained sented its updated branching ratio for For: Stimulus-Response, Record/Replay, ATE, MIMO etc. IPMU, University of Tokyo. This year’s by the existence of new particles such as the ultra-rare decay K+ → π+νν–, which is ) –10 2+2, 4+4 or 8+8 channels with 40 MS/s or 125 MS/s edition, the 19th in the series, attracted –9 0.4 leptoquarks or Z′ bosons. We will know predicted to be around 10 in the SM. around 350 registrants, significantly much more when LHCb releases measure- The data set is now sufficiently large to AWG: Output up to ±12 V into high impedance ) (10 more than have attended physical Beauty – ments from the updated analysis of the see a signal with a significance of more μ 0.3 Digitizer: Single-ended or differential inputs conferences in the past. Two days were + full Run-2 data set. In the meantime, the than three standard deviations. Future devoted to parallel sessions, a change in combined results from ATLAS, CMS and running is planned to allow a measure- → μ 0.2 approach necessitated by the online for- 0 LHCb for the branching ratio of the ultra- m e nt t o b e m a d e w it h a 10–20% pr e c i s i o n,

B(B SM + – mat, stimulating lively discussion. There 0.1 rare decay Bs → μ μ generated much dis- wh ic h w i l l prov ide a p ower f ul test of t he were 64 invited talks, of which 13 were c u s s i o n. T h i s fi n a l s t a t e i s pr o d u c e d o nly SM prediction (CERN Courier September/ SPECTRUM

over v iews g iven by t heorists. 0 a few times every billion Bs decays, but is October 2020 p9). INSTRUMENTATION Studies of beauty hadrons have great 1 2345now measured to a remarkable precision The concluding plenary session 0 + – –9 sensitivity to possible physics beyond the B(Bs → μ μ ) (10 ) of 13%. Intriguingly, the observed value focused on the future of flavour phys- Perfect fit – modular designed solutions Standard Model (SM), as was stressed by of the branching ratio lies two standard ics. The LHCb experiment is currently 0 0 Gino Isidori (University of Zurich) in the Ultra-rare A combination of results on B → μμ and B s → μμ deviations below the SM prediction (see being upgraded, and a further upgrade Europe / Asia: Phone +49 (4102) 695 60 | US: Phone (201) 562 1999 opening talk of the conference. Possi- from the ATLAS, CMS and LHCb experiments, showing the one “Ul t r a-r a r e” fi g u r e) – a n e ffe c t t h a t s ome is foreseen at the end of the decade. In ble lepton-universality anomalies that through to five standard-deviation contours, and the prediction commentators have noted could be driven p a r a l l e l, t h e u p g r a d e s o f AT L A S a n d C M S www.spectrum-instrumentation.com s have emerged from analyses of decays of the Standard Model. by the same new particles invoked to w i l l i n c r e a s e t h e i r c a p a bi l it i e s for b e a ut y

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Opening doors The ALICE experiment pictured in August, ready to welcome its upgraded TPC – a vital detector for studying the production and Supported features include: annihilation of antinuclei. (Credit: CERN-PHOTO-202008-104-63) • Up to 10 GSPS sampling rate with 14 bits resolution • Open FPGA for custom real-time signal processing • Multiple form factors including MTCA.4, PXIe, and PCIe ’ • Multi-channel synchronization capabilities ALICE S DARK SIDE • White Rabbit synchronization (MTCA.4 only) Precision measurements of the production and annihilation of light antinuclei • Peer-to-peer streaming to GPU (PCIe only) at the LHC’s ALICE experiment are sharpening the search for dark matter, • Application-specific firmware shortens design time explain Maximiliano Puccio and Ivan Vorobyev.

he nature of dark matter (DM) remains one of the hole in our understanding of the universe continues to most intriguing unsolved questions of modern drive multiple experimental searches for DM both in the THE AUTHORS physics. Astrophysical and cosmological obser- laboratory and in space. No clear evidence for DM has yet T Maximiliano vations suggest that DM accounts for roughly 27% of the been found, severely constraining the parameter space of Puccio CERN mass-energy of the universe, with dark energy comprising the most popular “thermal” DM models. and Ivan Vorobyev Learn more on our website 68% and ordinary baryonic matter as described by the Assuming DM is a material substance comprised of Technische www.spdevices.com Standard Model accounting for a paltry 5%. This massive particles – not an illusion resulting from an imperfect Universität München.

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FEATURE ANTINUCLEI FEATURE ANTINUCLEI

matter can be studied on Earth using large accelerators. Source: arXiv:2005.11122

88980 0.006 The m a i n c ont r i b ut ion s s o f a r h a ve c ome f rom t he L HC at ALICE ALICE ALICE CERN and from the Relativistic Heavy Ion Collider (RHIC) 6 6 p–Pb, √s NN = 5.02 TeV p–Pb √s NN = 5.02 TeV p–Pb √s NN = 5.02 TeV Eur. Phys.Eur. C J. at Brookhaven National Laboratory. Thanks to its unique 0.005 V0A multiplicity classes (Pb-side) 〈Z〉 = 8.5, 〈A〉 = 17.4, |η| < 0.8 〈Z〉 = 14.8, 〈A〉 = 31.8, |η| < 0.8 low-material-budget tracker, which provides excellent Source: Source: Pb–Pb, √s NN = 2.76 TeV _ tracking and particle-identification performance for _ pp, √s NN = 7 TeV σ (d + 〈A〉) Geant4 σ (d + 〈A〉) Geant4 0.004 inel inel pp, √s NN = 13 TeV low-momentum particles, ALICE is the only experiment 4 4 σ inel(d + 〈A〉) Geant4 σ inel(d + 〈A〉) Geant4 V0M multiplicity classes at the LHC that is able to study the production and anni- – (b) (b) data (ITS + TPC + TOF) data (ITS + TPC) _

inel _ 0.003 hilation of low-energy antinuclei. inel σ σ (d + 〈A〉) ± 1σ σ σ (d + 〈A〉) ± 1σ inel _ inel _

2d/(p + p) (d + A ) ± 2 Antinucleosynthesis in the lab 2 σ inel(d + 〈A〉) ± 2σ 2 σinel 〈 〉 σ 0.002 thermal-FIST CSM (PLB 785 (2018) 171–174) While antinuclei can also be produced at lower collision T = 155 MeV, V = 3 dV/dy ch c e ne r g ie s, on l y at t he L HC a re m at t e r a nd a nt i m at t e r ge n- T = 155 MeV, V = dV/dy 0.001 ch c erated in equal abundances in the region transverse to the 0 0 coalescence (PLB 792 (2019) 132–137) b e a m d i r e c t io n. T h e m o s t a b u n d a nt n o n-t r i v i a l a nt i nuc le u s 021 3 4 021 34 produced is the antideuteron, which consists of an anti- 0 p [GeV/c] p [GeV/c] neutron and an antiproton. At low momentum, deuterons 2 3 1 10 10 10 and antideuterons can be clearly identified thanks to their Interaction probability Antideuteron inelastic interaction cross section measured in different ALICE subdetectors. The dashed red line represents the 〈dN /dη 〉 ch lab |ηlab|< 0.5 high energy loss in the ALICE detector’s time-projection parameterisations used for antideuterons in the Geant4 toolkit, and the full grey line shows the parameterisations for deuterons. The full points chamber. At larger momenta, a clean identification of correspond to the experimental measurements, whereas the purple and orange bands are the one and two sigma uncertainty intervals, respectively. Competing models The ratio of (anti)deuterons to protons in p–p, p–Pb and antideuterons is possible using the ALICE time-of-flight Pb–Pb collisions as a function of the average number of charged particles detector. This information, combined with the measured the two collaborations. results will impact the antideuteron flux expectations produced. The purple line shows the expectation of the coalescence model while track length and the particle momentum, provide a precise Further helping clarify the results of indirect DM at low momentum for ongoing and future - and the solid and dashed black lines represent extreme parameter configurations for determination of the particle mass. Using these and other searches, ALICE has recently performed the first meas- balloon-borne experiments. the statistical hadronisation model. techniques, the ALICE collaboration has recently meas- urement of the antideuteron inelastic cross section in ured the production of (anti)deuterons in proton–proton the momentum range 0.3 < p < 4 GeV/c – significantly The heavier, the better understanding of gravity – there are three independent collisions, as well as in other colliding systems, and set extending our knowledge about this cross section from ALICE is studying the full range of antinuclei physics with ways to search for it. One is to directly measure the pro- tight constraints on the production models of (anti)nuclei. previous measurements at momenta of 13 and 25 GeV/c at unprecedented precision. These results, which have started duction of DM particles in a high-energy collider such There are two main ways to model the production mech- the Serpukhov accelerator complex in Russia in the early t o e m e r g e o n l y s i n c e 2015, a r e c o nt r i b ut i n g s i g n i fic a nt l y t o as the LHC. Another is to infer the presence of DM par- anism of (anti)nuclei. Coalescence models assume that 1970s. The collaboration took advantage of the ability of our understanding of antinuclei formation and annihilation ticles via their scattering off nuclei, as investigated by primary (anti)neutrons and (anti)protons can bind if they antideuterons produced at the LHC to interact inelastically pr o c e s s e s, w it h i m p or t a nt r a m i fic at io n s for DM s e a rc h e s. large underground detectors such as XENON1T and LUX. are close enough in phase space. Statistical hadronisation with the detector material. To quantify this process, ALICE Both the statistical hadronisation and coalescence models A third, similarly indirect, strategy is to search for the m o d e l s, o n t h e o t h e r h a n d, a s s u m e t h at h a d r o n s a n d (a nt i) has employed a novel approach based on the antideu- can describe antideuteron production annihilation or decay of DM particles into ordinary (anti) nuclei emerge when the collision system reaches thermo- teron-to-deuteron ratio reconstructed in collisions of at the LHC, while the detector material The momentum range particles such as or antinuclei – as employed dynamical equilibrium, making the temperature and the protons and heavy ions at a centre-of-mass energy per can be used as an absorber to study covered is of particular b y t h e A M S e x p e r i m e nt o n b o a rd t h e I nt e r n at io n a l S p a c e volume of the system the key parameters. Measurements nucleon–nucleon pair of 5.02 TeV. Such a ratio depends the antinuclei inelastic cross section Station and in balloon-borne experiments such as GAPS. of nuclei-to-proton ratios in various colliding systems on both of the inelastic cross sections of deuterons and at low energies relevant for the astro- importance to evaluate Low-energy light antinuclei, such as antideuterons and have recently enabled the ALICE collaboration to compare antideuterons. The former has been measured in various physical applications. the signal predictions antihelium, are particularly promising signals for such the two model approaches in detail (see “Competing mod- previous experiments at different momenta; the latter For the foreseeable future, ALICE will indirect DM searches, since the background stemming e l s” fi g u r e). A s c a n b e s e e n, t h e t wo m o d e l s g i v e d ifferent can be constrained from the ALICE data by comparing the continue to provide an essential refer- for indirect dark-matter from ordinary collisions between cosmic rays and the predictions for the evolution of the nuclei-to-proton ratio measured ratio with detailed Monte Carlo simulations. ence for the interpretation of astrophys- is expected to be low with respect versus particle multiplicity, with the latest ALICE meas- The resulting antideuteron inelastic cross section is ics measurements of antinuclei in space. searches to the DM signal. urements slightly favouring the coalescence approach. shown (see “Interaction probability” figure), where the With the increased integrated luminos- T h e a bi l it y t o i nt e r pr e t a n y f ut u r e o b s e r v at io n o f a nt i- Similar conclusions about the two models can be drawn two panels correspond to the different sub-detectors ity that will be acquired by ALICE during LHC Run 3 from — — nuc le i i n o u r g a l a x y – e s p e c i a l l y w h e n t r y i n g t o id e nt i f y using heavier antinuclei, like 3He and 4He, which were employed in the analysis and therefore to different average early 2022, it will be possible to extend the current analyses — — their creation in exotic processes like DM annihilations already measured by ALICE in p–Pb and Pb–Pb collisions. material crossed by (anti)deuterons – corresponding to a to heavier (anti)nuclei, such as 3He and 4He, with even better – requires a quantitative understanding of light anti- The achievable precision of the measurement is limited difference of about a factor two in average mass number. precision than the currently available measurements for nuclei production and annihilation mechanisms within by the available data: the antinuclei production rate in pp The inelastic cross sections include all possible inelastic (anti)deuterons. This will allow the collaboration to perform t h e i nt e r s t e l l a r m e d iu m. Ho w e v e r, t h e pr o d uc t io n o f l i g ht collisions goes down by a factor of about 1000 for every antideuteron processes such as break-up, annihilation or fundamental tests of the production and annihilation mech- ALICE is antinuclei in hadronic collisions between cosmic rays additional antinucleon in the antinucleus. charge exchange, and the analysis procedure was validated anisms with heavier, doubly-charged antinuclei, which are and the interstellar medium is still not fully understood: The precision of the measurements from proton–proton by demonstrating consistency with existing antiproton m or e e a s i l y id e nt i fie d b y s at e l l it e-b or n e e x p e r i m e nt s a n d the only different models compete to explain how these loosely collisions places strong constraints on the production results from traditional scattering experiments. thus expected to provide an even clearer DM signature.  experiment bound objects can be formed in such high-energy col- m o d e l s, w h ic h c a n t h e n b e u s e d t o pr e d ic t t h e a nt i nuc le i The momentum range covered in this latest analysis at the LHC lisions. Furthermore, the inelastic annihilation cross fluxes in space. Indeed, the ALICE measurements com- is of particular importance to evaluate the signal pre- Further reading that is able section of light antinuclei with matter is completely bined with different coalescence models have already dictions for indirect dark-matter searches. Additionally, ALICE Collab. 2020 Eur. Phys. J. C 80 889. to study the unknown in the kinematic region relevant for indirect been employed to estimate the antideuteron and anti- these measurements can help researchers to understand ALICE Collab. 2020 Phys. Rev. Lett. 125 162001. production and DM s e a rc h e s, forc i n g c u r r e nt e s t i m at e s t o r e l y o n e x t r a p- helium flux from cosmic-ray interactions measurable the low-energy antideuteron inelastic processes and to ALICE Collab. 2020 Phys. Rev. C 101 044906. annihilation olations and modelling. by the AMS and GAPS experiments. These predictions model better the inelastic antideuteron cross sections in K Blum et al. 2017 Phys. Rev. D 96 103021. of low-energy Fortunately, both the antinuclei production mechanism will allow correct interpretations of the eventual anti- widely-used toolkits such as Geant4. Together with the M Korsmeier et al. 2018 Phys. Rev. D 97 103011. antinuclei and the interactions between antinuclei and ordinary nuclei signal that might be observed in the future by proper modelling of antinuclei formation, the obtained A Shukla et al. 2020 Phys. Rev. D 102 063004.

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FEATURE DETECTOR TECHNOLOGY NEUTRINOS FOR PEACE Detectors similar to those used to hunt for sterile neutrinos could help guard against the extraction of plutonium-239 for nuclear weapons, writes Patrick Huber.

he first nuclear-weapons test shook the desert in Lavitt collaboration/M PROSPECT of the neutrino including oscillation searches continued New Mexico 75 years ago. Weeks later, Hiroshima there until 1988, when the P reactor was shut down. T and Nagasaki were obliterated. So far, these two Ne ut r i n o s a r e n o t pr o d uc e d i n nuc le a r fi s s io n it s e l f, b ut Japanese cities have been the only ones to suffer such a by the beta decays of neutron-rich fission fragments – on f at e. Ne ut r i n o s c a n h e l p t o e n s u r e t h at n o o t h e r c it y h a s t o average about six per fission. In a typical reactor fuelled be added to this dreadful list. by natural uranium or low-enriched uranium, the reactor At the height of the arms race between the US and the starts out with only uranium-235 as its . During oper- USSR, stockpiles of nuclear weapons exceeded 50,000 war- ation a significant number of neutrons are absorbed on heads, with the majority being thermonuclear designs uranium-238, which is far more abundant, leading to the vastly more destructive than the fission bombs used in formation of u r a n ium-239, which after two beta decays World War II. Significant reductions in global nuclear becomes plutonium-239. Plutonium-239 eventually con- stockpiles followed the end of the Cold War, but the US tributes to about 40% of the fissions, and hence energy a n d Ru s s i a s t i l l h a v e a b o ut 1 2,500 nuc le a r w e a p o n s i n t o t a l, production, in a commercial reactor. It is also the isotope and the other seven nuclear-armed nations have about used in nuclear weapons. 1500. To d a y, t h e p ol it ic s o f non-proliferation i s o n c e a g a i n The dual-use nature of reactors is at the crux of tense and unpredictable. New nuclear security challenges nuclear non-proliferation. What distinguishes a have appeared, often from unexpected actors, as a result plutonium-production reactor from a regular reactor of leadership changes on both sides of the table. Nuclear producing electricity is whether it is operated in such a arms races and the dissolution of arms-control treaties way that the plutonium can be taken out of the reactor have yet again become a real possibility. A regional nuclear core before it deteriorates and becomes difficult to use in war involving just 1% of the global arsenal would cause weapons applications. A reactor with a massive loss of life, trigger climate effects leading to a low content of plutonium-239 makes The story of the crop failures and jeopardise the food supply of a billion more and higher energy neutrinos than people. Until we achieve global disarmament, nuclear one rich in plutonium-239. neutrino is closely non-proliferation efforts and arms control are still the Lev Mikaelyan and Alexander tied to nuclear most effective tools for nuclear security. Borovoi, from the Kurchatov Institute Technology demonstration Technicians assemble the PROSPECT , which was installed a few metres from the in Moscow, realised that neutrino weapons Not a bang but a whimper High Flux Isotope Reactor at Oak Ridge National Laboratory in Tennessee. Similar technologies could be used to monitor nuclear reactors. emissions can be used to infer the

T h e s t or y o f t h e n e ut r i n o i s c lo s e l y t ie d t o nuc le a r w e a p o n s. F Reines power and plutonium content of a reactor. In a series of The first serious proposal to detect the particle hypothe- trailblazing experiments at the Rovno nuclear power plant F Rei nes sised by Pauli, put forward by Clyde Cowan and Frederick in the 1980s and early 1990s, their group demonstrated that Reines in the early 1950s, was to use a nuclear explosion a tonne-scale underground neutrino detector situated 10 as the source (see “Daring experiment” figure). Inverse to 20 metres from a reactor can indeed track its power and beta decay, whereby an electron-antineutrino s t r i k e s a f r e e plutonium content. proton and transforms it into a neutron and a positron, was The significant drawback of neutrino detectors in the to be the detection reaction. The proposal was approved 1980s was that they needed to be situated underground, in 1952 as an addition to an already planned atmospheric beneath a substantial overburden of rock, to shield them nuclear-weapons test. However, while preparing for this from cosmic rays. This greatly limited potential deployment e x p e r i m e nt, C o w a n a n d Re i n e s r e a l i s e d t h at b y c a p t u r i n g sites. There was a series of application-related experiments the neutron on a cadmium nucleus, and observing the – notably the successful SONGS experiment conducted by delayed coincidence between the positron and this neutron, researchers at Lawrence Livermore National Laboratory, they could use the lower, but steady flux of neutrinos from which aimed to reduce cost and improve the robustness a nuclear reactor instead (see “First detection” figure). and remote operation of neutrino detectors – but all of This technique is still used today, but with gadolinium or these detectors still needed shielding. lit hium in place of cadmium. The P reactor at the Savannah River site at Oak Ridge Daring experiment Before observing neutrinos streaming from From cadmium to gadolinium Nat io n a l L a b or at or y, w h ic h h a d b e e n b u i lt a n d u s e d t o m a k e a nuclear reactor, Fred Reines and Clyde Cowan initially proposed First detection Reines and Cowan’s “delayed coincidence” Synergies with fundamental physics grew in the 1990s, THE AUTHOR plutonium and tritium for nuclear weapons, eventually to discover the particles using a nuclear explosion. A detector would detection scheme. The neutron is captured on a cadmium nucleus when the evidence for neutrino oscillations was becoming Patrick Huber hos te d t he suc c e ss f u l e x p e r i me nt to fi r s t de te c t t he neu- be suspended in a vertical vacuum tank and allowed to free-fall about 10 microseconds after the prompt event caused by the positron impossible to ignore. With the range of potential oscil- Virginia Tech. t r i n o i n 1956. Ne ut r i n o e x p e r i m e nt s t e s t i n g t h e pr o p e r t ie s until the shock wave had passed. annihilation, and the subsequent nuclear de-excitation tagged. lations frequencies narrowing, the Palo Verde and

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FEATURE DETECTOR TECHNOLOGY FEATURE DETECTOR TECHNOLOGY

To directly observe the high-frequency oscillations of IR-40 was planned to be a 40 MW reactor fuelled by natural Virginia Tech an eV-scale you need to get within about uranium and moderated with heavy water, with a stated CEA Saclay CEA Saclay 10 m of the reactor. At this distance, backgrounds from the purpose of isotope production for medical and scientific operation of the reactor are often non-negligible, and no use. The choice of fuel and moderator is interesting, as overburden is possible – the same conditions a detector it meshes with Iranian capabilities and would serve the on a safeguards mission would encounter. stated purpose well and be cost effective, since no ura- nium enrichment is needed. Equally, however, if one were From gadolinium to lithium to design a plutonium-production reactor for a nascent Around half a dozen experimental groups are chasing weapons programme, this combination would be one of the sterile neutrinos using small detectors close to reactors. top choices: it does not require uranium enrichment, and Some of the most advanced designs use fine spatial seg- with the stated reactor power would result in the annual mentation to reject backgrounds, and replace gadolinium production of about 10 kg of rather pure plutonium-239. with lithium-6 as the nucleus to capture and tag neutrons. This matches the critical mass of a bare plutonium-239 Lithium has the advantage that upon neutron capture it sphere, and it is known that as little as 4 kg can be used to produces an alpha particle and a triton rather than a hand- make an effective nuclear explosive. Within the JCPOA it ful of photons, resulting in a very well localised tag. In a was eventually agreed that the IR-40 could be redesigned, Purpose driven reactor experiments placed multi-tonne detectors about small detector this improves event containment and thus down-rated in power to 20 MW and the new core fuelled A spin off from 1 km from nuclear reactors, and sought to measure the rel- efficiency, and also helps constrain event topology. with 3.7% enriched fuel, reducing the annual plutonium

Double Chooz, atively small θ13 parameter of the neutrino mixing matrix, Following the lithium and finely segmented technical production by a factor of six. the Nucifer which expresses the mixing between electron neutrinos paths, the PROSPECT collaboration and the CHANDLER A 10 t o 20 t o n n e n e ut r i n o d e t e c t or 20 m from the reactor Rapid deployment The prototype “MiniCHANDLER” detector at Virginia Tech. detector was small and the third neutrino mass eigenstate. Both experiments collaboration (see “Rapid deployment” figure), in which would be able to measure its plutonium content with a Made from plastic rather than , a robust CHANDLER-type detector and efficient at used large amounts of liquid organic scintillator doped I participate, independently reported the detection of a precision of 1 to 2 kg. This would be particularly relevant could be rapidly deployed at a nuclear reactor. detecting with gadolinium. The goal was to tag antineutrino events neutrino spectrum with minimal overburden and high in the so-called N-th month scenario, which models a neutrinos, by capturing the neutrons on gadolinium, rather than the detection efficiency in 2018. This is a major milestone in potential crisis in Iran based on events in North Korea in months at the very least, creating dangerous ambiguity but required a cadmium used by Reines and Cowan. Gadolinium produces making non-proliferation applications a reality, since it June 1994. During the 1994 crisis, which risked precipi- in the interim and giving hardliners on both sides time significant 8 MeV of gamma rays upon de-excitation after a neutron is the first demonstration of the technology needed for tating war with the US, the nuclear reactor at Yongbyon to push for an escalation of the crisis. The conventional overburden capture. As it has an enormous neutron-capture cross sec- tonne-scale detectors capable of monitoring the pluto- was shut down, and enough spent fuel rods removed to approach would also be significantly more expensive than of rock. tion, even small amounts greatly enhance an experiment’s nium content of a nuclear reactor that could be universally make several bombs. IAEA protocols were sternly tested. a neutrino detector. ability to identify neutrons. deployed without the need for special site preparation. The organisation’s conventional safeguards for operating Eventually, neutrino oscillations became an accepted fact, The main difference between the two detectors is that reactors consist of containment and surveillance – seals, New negotiating gambit

redoubling the interest in measuring θ13. This resulted in three PROSPECT, which reported its near-final sterile neutrino for e x a m ple, t o pr e v e nt t h e u n n o t ic e d o p e n i n g o f t h e r e a c- T h e Ju n e 1994 c r i s i s at Yo n g b yo n s t i l l o v e r s h a d o w s n e g o t i- new experiments: in France, RENO in South limit at the Neutrino 2020 conference, uses a traditional tor, and cameras to record the movement of fuel, most ations with North Korea, since, as far as North Korea is con- Korea, and Daya Bay in China. Learning lessons from Palo approach with liquid scintillator, whereas CHANDLER, cur- crucially during reactor shutdowns. In the N-th month cerned, it discredited the IAEA. Both during the crisis, and

Verde and Chooz, the experiments successfully measured θ13 rently an R&D project, uses plastic scintillator. The use of scenario, the IR-40 reactor, in its pre-JCPOA configuration subsequently, international attempts at non-proliferation more precisely than any other neutrino mixing parameter. A plastic scintillator allows the deployment time-frame to be (40 MW, rather than the renegotiated power of 20 MW), failed to prevent North Korea from acquiring nuclear weap- spin-off from the Double Chooz experiment was the Nucifer shortened to less than 24 hours. On the other hand, liquid runs under full safeguards for N–1 months. In month N, ons – its firstnuclear-weapons test took place in 2006 detector (see “Purpose driven” figure), which demonstrated scintillator allows the exploitation of pulse-shape discrim- a planned reactor shutdown takes place. At this point the – or even to constrain its progress towards a small-scale the operation of a robust sub-tonne-scale detector designed ination to reject cosmic-ray neutron backgrounds, allowing reactor would contain 8 kg of weapons-grade plutonium. For operational nuclear . New approaches are therefore with missions to monitor reactors in mind, in alignment PROSPECT to achieve a much better signal-to-background unspecified reasons the safeguards are then interrupted. needed, and recent attempts by the US to achieve progress with requirements formulated at a 2008 workshop held by ratio than any plastic detector to date. Active R&D is seeking In month N+1, the reactor is restarted and full safeguards on this issue prompted an international group of about 20 the International Atomic Energy Agency (IAEA). However, to improve topological reconstruction in plastic detectors are restored. The question is: are the 8 kg of plutonium still n e ut r i n o e x p e r t s f r o m E u r o p e, t h e US, Ru s s i a, S o ut h Kor e a, Nucifer st ill needed a sig nificant overburden. and imbue them with pulse-shape discrimination. In addi- in the reactor core, or has the core been replaced with fresh China and Japan to develop specific deployment scenarios In 2011, however, shortly before the experiments estab- tion, a number of safeguard-specific detector R&D exper- fuel and the 8 kg of plutonium illicitly diverted? for neutrino detectors at the Yongbyon nuclear complex.

lished that θ13 is not zero, fundamental research once again iments have successfully detected reactor neutrinos using The disruption of safeguards could either be due to The main concern is the 5 MWe reactor, which, though galvanised the development of detector technology for reac- plastic scintillator in conjunction with gadolinium. In the equipment failure – a more frequent event than one might named for its electrical power, has a thermal power of tor monitoring. In the run-up to the Double Chooz experi- UK, the VIDARR collaboration has seen neutrinos from the assume – or due to events in the political realm ranging 20 MW. This gas-cooled graphite-moderated reactor, ment, a group at Saclay started to re-evaluate the predictions Wylfa reactor, and in Japan the PANDA collaboration suc- from a minor unpleasantness to a full-throttle dash for a fuelled with natural uranium, has been the source of all for reactor neutrino fluxes – then and now based on meas- cessfully operated a truck-mounted detector. nuclear weapon. Distinguishing the two scenarios would of North Korea’s plutonium. The specifics of this reactor, urements at the Institut Laue-Langevin i n t h e 1980 s – a n d In parallel to detector development, studies are being be a matter of utmost urgency. According to an analysis and in particular its fuel cladding, which makes prolonged To directly fo u n d t o t h e i r s u r pr i s e t h at t h e r e a c t or flu x pr e d ic t io n c a me undertaken to understand how reactor monitoring with including realistic backgrounds extrapolated from the wet-storage of irradiated fuel impossible, represent such a observe out 6% higher than before. Given that all prior experiments neutrinos would impact nuclear security and support PROSPECT results, this could be done in 8 to 12 weeks proliferation risk that anything but a monitored shutdown the high- were in agreement with the old flux predictions, neutri- non-proliferation objectives. Two very relevant situations with a neutrino detector. prior to a complete dismantling appears inappropriate. To frequency nos were missing. This “reactor-antineutrino ” being studied are the 2015 Iran Deal – the Joint Compre- No conventional non-neutrino technologies can match safeguard against the regime reneging on such a deal, were oscillations persists to this day. A sterile neutrino with a mass of about h e n s i v e Pl a n o f A c t io n ( JC P OA) – a n d v e r i fic at io n c o n c e p t s this performance without shutting the reactor down and it to be agreed, a relatively modest tonne-scale neutrino 1 eV would be a simple explanation. This mass range has for a future agreement with North Korea. sampling a significant fraction of the highly radioactive detector right outside the reactor building could detect a of an eV-scale been suggested by experiments with accelerator neutrinos, fuel. The conventional approach would be extremely dis- powering up of this reactor within a day. sterile neutrino m o s t n o t a bl y L SN D a n d M i n i B o oN E, t h o u g h it c o n fl ic t s w it h Nuclear diplomacy ruptive to reactor operations and would put inspectors and Nor t h K or e a i s a l s o c o n s t r uc t i n g t h e E x p e r i m e nt a l L i g ht you need to predictions that muon neutrinos should oscillate into such One of the sticking points in negotiating the 2015 Iran plant operators at risk of radiation exposure. Even if the Water Reactor at Yongbyon. A 150 MW water-moderated get within a sterile neutrino, which experiments such as MINOS+ have deal was the future of the IR-40 reactor, which was being host country were to agree in principle, developing a safe reactor running with low-enriched fuel, this reactor would about 10 m of failed to confir m. constructed at Arak, an industrial city in central Iran. The plan and having all sides agree on its feasibility would take not be particularly well suited to plutonium production. the reactor

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FEATURE DETECTOR TECHNOLOGY FEATURE TESLA TECHNOLOGY COLLABORATION

detectors that would be needed. A more promising future le/DESY Noel D

Daya Bay application of neutrino-detector technology is to meet the new challenges posed by advanced nuclear-reactor designs. TESLA’S Advanced safeguards The current safeguards regime relies on two key assump- tions: that fuel comes in large, indivisible and individually id e nt i fi a ble u n it s c a l le d “f ue l a s s e m bl ie s”, a n d t h at p ower HIGH- reactors need to be refuelled frequently. Most advanced reactor designs violate at least one of these design char- ac ter i st ic s. F ue l m ay c ome i n t hous a nd s of sm a l l p e b ble s or be molten, and its coolant may not be transparent, in GRADIENT contrast to current designs, where water is used as mod- erator, coolant and storage medium in the first years after discharge. Either way, counting and identification of the MARCH f ue l b y s e r i a l nu m b e r m a y b e i m p o s s i ble. A n d u n l i k e c u r r e nt power reactors, which are refuelled on a 12-to-18-month cycle, allowing in-core f ue l t o b e v e r i fie d a s w e l l, a d v a n ced A d i ffe r e nt Its design is not dissimilar to much larger reactors used reactors may be refuelled only once in their lifetime. scenario Three throughout the world to produce electricity, and it could Neutrino detectors would not be hampered by any of of the 20 tonne help address the perennial lack of electricity that has lim- these novel features. Detailed simulations indicate that Established 30 years ago with neutrino detectors ited the development and growth of the country’s economy. t he y could b e effe c t ive i n add ressi ng t he sa feg ua rd c ha l- employed by the North Korea may wish to operate it indefinitely. A larger, lenges presented by advanced reactors. Crucially, they a linear electron–positron Daya Bay 10 tonne neutrino detector could detect any irregularities would work in a very similar fashion for any of the new collider in mind, the TESLA experiment in during its refuelling – a tell-tale sign of a non-civilian use reactor designs. China. To monitor of the reactor – on a timescale of three months, which is I n 2019 t h e US D e p a r t m e nt o f E n e r g y c h a r t e r e d a n d f u n d e d Technology Collaboration a total shutdown w it hin t he goals set by t he IA E A. a study (which I co-chair) w it h t h e g o a l o f d e t e r m i n i n g t h e of all reactors at In a different scenario, wherein the goal would be to ut i l it y o f t h e u n iq ue c a p a bi l it ie s offe r e d b y n e ut r i n o d e t e c t ors has played a major role in the Yongbyon, it monitor a total shutdown of all reactors at Yongbyon, it for nuclear security and energy applications. This study would be feasible would be feasible to bury a Daya-Bay-style 50 tonne single includes investigators from US national laboratories and aca- development of superconducting to bury a 50 tonne volume detector under the Yak-san, a mountain about 2 km demia more broadly, and will engage and interview nuclear single volume outside of the perimeter of the nuclear installations (see “A s e c u r it y a n d p ol ic y e x p e r t s w it h i n t h e D e p a r t m e nt o f E n e r g y, radio-frequency cavities and detector of similar d i ffe r e nt s c e n a r io” fi g u r e). T h e c o s t a n d d e plo y m e nt times- the State Department, NGOs, academia, and international related technologies for a wide design under a cale would be more onerous than in the other scenarios. agencies such as the IAEA. The results are expected early in nearby mountain In the case of longer distances between reactor and 2021. They should provide a good understanding of where variety of applications. in North Korea. detector, detector masses must increase to compensate neutrinos can play a role in current and future monitoring an inverse-square reduction in the reactor-neutrino flu x. and verification agreements, and may help to guide neu- As cosmic-ray backgrounds remain constant, the detectors trino detectors towards their firstreal-world applications. nergetic beams of charged particles are essential for Superconducting materials, on the other hand, can support Standing tall must be deployed deep underground, beneath an over- T h e id e a o f u s i n g n e ut r i n o s t o m o n it or r e a c t or s h a s b e e n high-energy physics research, as well as for studies sustainable high-accelerating gradients wit h an afforda- Superconducting burden of several 100 m of rock. To this end, the UK’s around for about 40 years. Only very recently, however, as a Eof nuclear structure and dynamics, and deciphering ble electricity bill. Early pioneering work demonstrating radio-frequency S c ie n c e a n d Te c h n olo g y Fa c i l it ie s C o u n c i l, t h e U K A t o m ic result of a surge of interest in sterile neutrinos, has detector complex molecular structures. In principle, generating such the first beam-acceleration using superconducting radio- cavities at DESY. We a p o n s E s t a bl i s h m e nt a n d t h e US D e p a r t m e nt o f E n e r g y, technology become available that would be practical in beams is simple: provide an electric field for acceleration frequency (SRF) cavities took place in the late 1960s and are funding the WATCHM AN collaboration to pursue the real-world s c e n a r io s s uc h a s t h e JC P OA or a n e w Nor t h K or e a n and a magnetic field for bending particle trajectories. In early 1970s at Stanford, Caltech, the University of Wuppertal construction of a multi-kilo-tonne water-Cherenkov nuc le a r a g r e e m e nt. T h e m o s t l i k e l y i n it i a l a p pl ic at io n w i l l practice, however, the task becomes increasingly challenging and Karlsruhe. The potential for real utility was clear, but detector at the Boulby mine, 20 km from two reactors be near-field reactor monitoring with detectors inside the as the desired particle energy goes up. Very high electric t e c h n iq ue s a n d m at e r i a l r e fi n e m e nt s w e r e n e e d e d. S e v e ral in Hartlepool, in the UK. The goal is to demonstrate the fence of the monitored facility as part of a regional nuclear fie ld s a r e r e q u i r e d t o at t a i n t h e h i g h e s t e n e r g y b e a mswithin individual laboratories began to take up the challenge for ability to monitor the operational status of the reactors, d e a l. Suc h d e t e c t or s w i l l n o t b e a p a n a c e a t o a l l v e r i fic at io n practical real-estate constraints. their own research needs. Solutions were developed for which have a combined power of 3000 MW. In a use-case and monitoring needs, and can only be effective if there The most efficient way to generate the ver y high electric electron acceleration at CESR, HERA, TRISTAN, LEP II and context this would translate to excluding the operation is a sincere political will on both sides, but they do offer fields in a vacuum environment required to transport a beam CEBAF, while heavy-ion SRF acceleration solutions were Neutrino of an undeclared 10 to 20 MW reactor within a radius of a more room for creative diplomacy, and a technology that is to build up a resonant excitation of radio waves inside a developed at Stony Brook, ATLAS, ALPI and others. The few kilometres , but no safeguards scenario has emerged is robust against the kinds of political failures which have metallic cavity. There is something of an art to shaping such community of SRF accelerator physicists was small but the detectors where this would give a unique advantage. derailed past agreements.  cavities to “get the best bang for the buck” for a particular lessons learned were consistently shared and documented. could be Inverse-square scaling eventually breaks down around application. The radio-frequency (RF) fields are inherently By the early 1990s, SRF technology had matured such that effective in 100 km, as at that distance the backgrounds caused by Further reading time-varying, and bunches of charged particles need to arrive complex large-scale systems were credible and the variety addressing civilian reactors far outshine any undeclared small reac- J Ashenfelter et al. 2018 Phys. Rev. Lett. 121 251802. with the right timing if they are to see only forward-accelerat- of designs and applications began to blossom. the safeguard tor almost anywhere in the northern hemisphere. Small A Bernstein et al. 2020 Rev. Mod. Phys. 92 011003. ing electric fields. Desirable very high resonant electric fields THE AUTHORS challenges signals also prevent the use of neutrino detectors for A A Borovoi et al. 1978 Soviet Atomic Energy 44 589–592. (e.g. 5–40 MV/m) require the existence of very high currents The TESLA springboard Eiji Kako KEK, presented nuclear-explosion monitoring, or to confirm the origin R Carr et al. 2019 Science & Global Security 27 15–28. in the cavity walls. These currents are simply not sustainable In 2020, the TESLA Technology Collaboration (TTC) cele- Paolo Pierini ESS by advanced of a suspicious seismic event as being nuclear, as conven- A Haghighat et al. 2020 Phys. Rev. Appl. 13 034028. for long durations using even the best normal-conducting brates 30 years of collaborative efforts on SRF technologies. and Charles E reactors tional technologies are more feasible than the very large C Stewart et al. 2019 Nat. Comm. 10 3527. materials, as they would melt from resistive heating. The TTC grew out of the first international TESLA (TeV Reece JLab.

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FEATURE TESLA TECHNOLOGY COLLABORATION FEATURE TESLA TECHNOLOGY COLLABORATION D Sertore/INFN D 60 s ll M Kel ly/A NL ce ILC TDR ILC 1 TeV upgrade 1TeV R&D goal high-gradient R&D 3 of 5 LSF5-1 Source: R G eng/JL ab 50

40

AL CM2 module ILC construction DESY XM-3 module ILC goal FN FAST 2X 125 GeV linac KEK CM-1+CM-2a module PXFEL1 module dule 30 STF mo E-XFEL construction [MV/m] c TESLA goal TTF TTF SASE FEL run 17.5 GeV linac E-XFEL photon science ac single-cell cavity E CEBAF 12 GeV upgrade multi-cell cavity CEBAF 12 GeV nuclear physics 20 2X 1.1 GeV linac CEBAF 12 GeV upgrade goal LCLS-II goal LCLS-II photon science

k ALICE LCLS-II construction SHINE construction SHINE CEBAF module ELBE re-wor CEBAF 4 GeV linac 8 GeV linac photon 10 6 GeV science JLAB FEL physics ARIEL ARIEL run construction nuclear medicine CEBAF goal CEBAF module CEBAF 4 – 5.7 GeV physics run production run

HEPL module SCA physics and FEL run (300 MeV) SCA FEL run (65 MeV) for physics, chemistry, biology, medicine today 0 MUSL-I MUSL-II nuclear physics run (80 MeV) 1970 1980 1990 2000 2010 2020 2030 few international vendors. Pushing up the purity of deliv- s io n o f i nt e r n at io n a l e ffor t s at K E K, DE S Y, C E A-S a c l a y a nd Low-beta year erable material required a concerted push, resulting in JLab eliminated this problem through the development of cavities Gradient growth SRF linac accelerating gradient achievements and application the avoidance of foreign material inclusions, which can electro-polishing techniques. Following a deeper under- A half-wave specifications since 1970. CW SRF Linacs – SCA: Stanford Superconducting be deadly to performance when uncovered in the final standing of the underlying electrochemistry, accelerating resonator string Accelerator; MUSL: llinois Microtron Using a Superconducting Linac; CEBAF: s t e p o f s u r f a c e pr o c e s s i n g. T h e fi g u r e-o f-m e r it for p u r it y gradients above 40 MV/m are now attainable with niobium. assembly at Continuous Electron Beam Accelerator Facility; JLab FEL: JLab Free Electron Laser; is the ratio of room-temperature to cryogenic normal- Another vexing problem that TTC member institutions Argonne National ELBE: HZDR Electron Linear accelerator with high Brillance and Low Emittance; conducting resistivity – the residual resistance ratio, RRR. helped to solve was the presence of “Q-drop” in the region Laboratory for ALICE: STFC Accelerators and Lasers In Combined Experiments; T h e c o m m o n c a v it y-g r a d e n io biu m m at e r i a l s p e c i fic at io n of high surface magnetic field, for which present expla- use in PIP-II at ARIEL: TRIUMF Advanced Rare IsotopE Laboratory; LCLS-II: Linac Coherence has thus come to be known as high-RRR grade. nations point to subtle migration of near-surface oxygen Fermilab. Light Source extension; SHINE: Shanghai High Brightness Photon Facility. Vertical test The first cavity of the ESS elliptical section Another later pursuit of pure niobium is the so-called deeper into the lattice, where it inhibits the subsequent Pulsed SRF Linacs – FAST: Fermilab Accelerator Science and Technology Facility; developed by INFN, seen here on the left (next to a large-grain “large grain” or “direct-from-ingot” material. Rather formation of lossy nanohydrides on cool-down. Avoidance of STF: KEK Superconducting RF Test Facility; E-XFEL: European X-Ray Free Electron prototype), being prepared for a vertical test at DESY before than insist on controlled ~30 µm grain-size distribution nanohydrides, whose by proximity effect Laser; ILC: International Linear Collider. shipment to CEA Saclay for assembly in the cryomodule. (grains being microcrystals in the structure), this mat- breaks down in the Q-drop regime, is required to sustain erial uses sheet slices cut directly from large ingots having accelerating gradients above 25 MV/m for some structures. Energy Superconducting Linear Accelerator) workshop, T E SL A Te c h n olo g y C ol l a b or at io n w it h a s c o p e b e yo n d t h e much larger, but arbitrarily sized, grains. Although not which was held at Cornell University in July 1990. Its aim original motivation of high-energy physics. The TTC, with yet widely used, this material has produced the highest Cleaning up w a s to de fi ne t he pa r a me ter s for a sup erconduc t i ng l i nea r its incredible worldwide collaboration spirit, has had a gradient TESLA-style cavities to date – 45 MV/m with a TTC members have also shared analyses and best practices 10 c ol l id e r for h i g h-e n e r g y p h y s ic s o p e r at i n g i n t h e TeV r e g io n major role in the growth of the SRF community, facilitating quality factor Q0 > 10 . Here again, though the topic was in cleaning and cleanroom techniques, which have evolved and to explore how to increase the gradients and lower the numerous important contributions over the past 30 years. initiated at JLab, this fruitful work was accomplished via dramatically during the past 30 years. This has helped to costs of the accelerating structures. It was clear from the worldwide international collaborations. beat down the most common challenge for developers and beginning that progress would require a large international 30 years of gradient march As niobium is a refractory metal that promptly cloaks users of SRF accelerating cavities: particulate-induced collaboration, and the Cornell meeting set in motion a series Conceptually, the objective of simply providing “nice clean” itself with about 4 nm of dielectric oxide, welding niobium field emission, whereby very high peak surface electric of successes that are ongoing to this day – including FLASH n io biu m s u r f a c e s o n R F s t r uc t u r e s s e e m s pr e t t y s t r a i g ht- components has to be performed by vacuum electron beam fields can turn even micron-scale foreign material into and the European XFEL at DESY (CERN Courier July/August for w a rd. I m p or t a nt s u b t le t ie s b e g i n t o e m e r g e, h o w e v e r, a s welding. Collaborative efforts in Europe, North America parasitic electron field emission sources, with resulting 2017 p25). T h e c ol l a b or at io n a l s o le d t o pr o p o s a l s for s e v e r a l o n e c o n s id e r s t h at t h e h i g h R F-s u r f a c e c u r r e nt s r e q u i r e d t o and Asia refined the parameters required to yield con- c r yogen ic a nd r ad iat ion burdens. E x tended i nter ior fina l large SRF-based research facilities including SNS, LCLS-II, s up p or t m a g n e t ic fie ld s up t o ~100 mT flo w o n l y i n t h e t op sistent niobium welds. The community gradually realised rinsing with high- ultra-pure water prior to cavity ESS, PIP-II and SHINE, as well as a growing number of 100 nm of the niobium surface, which must offer routine that extreme cleanliness is required in the surface-weld assembly has become standard practice, while preparation smaller facilities around the world. surface resistances at the nano-ohm level over areas of preparation, since even microscopic foreign material will and assembly of all beamline vacuum hardware under ISO At the time of the first TESLA collaboration meeting, the around 1 m2. Achieving blemish-free, contamination-free be vaporised during the weld process, leaving behind small 4 cleanroom conditions is necessary to maintain these state-of-the-art in accelerating gradients for electrons was surfaces that present excellent crystal lattice structure voids that become performance-limiting defects. clean surfaces for accelerator operations. around 5 M V/m i n t h e o p e r at i n g SR F s y s t e m s o f T R ISTA N at even in this thin surface layer is far from easy. Ha v i n g t h e b e s t n io biu m i s n o t s u ffic ie nt, h o w e v e r. Sup er- The most recent transformation has come with the rec- K E K, H E R A at DE S Y, L E P-II at C E R N a n d C E B A F at Je ffe r s o n The march of progress in cavity gradient for linacs and c o n d uc t or s h a v e i n h e r e nt c r it ic a l m a g n e t ic fie ld l i m it at io n s, ognition that interstitial doping of the niobium surface Lab (JLab), which were then under construction. Many the many representative applications over the past 50 years or equivalently local surface-current density limitations. with nitrogen can reduce SRF surface resistance much participants in this meeting agreed to push for a five-fold (see figure “Gradient growth”) are due to breakthroughs Because the current flow is so shallow, local magnetic field more than was dreamed possible, reducing the cryogenic increase in the design accelerating gradient to 25 MV/m i n t h r e e m a i n a r e a s: m at e r i a l p u r it y, f a br ic at io n a n d pr o - enhancements induced by microscopic topography translate heat load to be cooled. While still the subject of material to meet the dream goal for TESLA at a centre-of-mass cessing techniques. The TTC had a major impact on each into gradient-limiting quench effects. Etching of fabricated research, this new capability was rapidly adopted into energ y of 1 TeV. The init ia l focus of t he col labor at ion w as of t hese areas. surfaces has routinely required a combination of hydro- the specification for LCLS-II cavities and is also being Accelerating centred on the design, construction and commissioning W it h s o m e n o t a ble e x c e p t io n s, b u l k n io biu m c a v it ie s f a b - fluor ic a n d n it r ic a c id s, b u ffe r e d w it h p h o s p h or ic a c id. This considered for an ILC. The effort started in the US and gradients of a technological demonstrator, the TESLA Test Facility ricated from sheet stock material have been the standard, exothermic etching process inherently yields step-edge quickly propagated internationally via the TTC, for example above 40 MV/m (TTF) at DESY. In 2004, SRF was selected as the basis for even though the required metallurgical processes pres- faceting at grain boundaries, which in turn creates local, in cavity tests at the European Spallation Source (see are now an International Linear Collider (ILC) design and, shortly ent challenges. Cycles of electron-beam vacuum refining, even nanoscopic, field enhancements, anomalous losses and “Vertical test” image). Earlier this year, Q-values of attainable afterwards, the TESLA collaboration was re-formed as the rolling, and intermediate anneals are provided by only a quenches as the mean surface field is increased. A progres- 3–4 × 1010 at 2 K at 30 MV/m were reported in TESLA-style with niobium

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FEATURE TESLA TECHNOLO COLLAORATION FEATURE RESEARCH FACILITIES

1800. Were a 250 GeV ILC to go ahead in Japan, approx- imately 8000 such units would be required. (Note that an alternative proposal for a high-energy linear collider, ESS the Compact Linear Collider, relies on a novel dual-beam FRIB acceleration scheme that does not require SRF cavities.) ARIEL SPIRALLING INTO MYRRHA bERLinpro Since the partners collaborating on the early TESLA goal CBETA MESA HEPS IFMIF LCLS-II TARLA of a linear collider were also involved in other national SARAF and international projects for a variety of applications a nd doma i ns, t he fi rst decade of t he 21st cent ur y saw t he CiADS Operation RAON TTC broaden its reach. For example, we started including e p i THE FEMTOSCALE SHINE reports from other projects, most notably the S Spallation Construction Neutron Source, and gradually opened to the community e electron Now freshly equipped with a new superconducting linac, the SPIRAL2 facility p proton/deuteron working on low-beta ion and proton superconducting cavi- i heavy ion ties, such as the half-wave resonator string collaboratively at GANIL will probe short-lived heavy nuclei and address applications in fission developed at A rgonne Nat ional Lab and now dest ined for Future plan e p i u s e i n PIP-II at Fe r m i l a b (s e e “L o w-b e t a c a v it ie s” i m a g e). and materials science using charged and neutron beams. TTC meetings include topical sessions with industries to discuss how to shorten the path from development to On the plus side lobal vie cavities – representing tremendous progress, but with production. Recently, the TTC has also begun to facilitate Inside view of the istriution of much optimisation still to be carried out. collaborative exchanges on alternative SRF materials to Ferdinand R radio-frequency

superconducting One of the main goals of the TTC has been to bridge the bulk niobium, such as Nb 3Sn and even hybrid multilayer quadrupole at the particle gap between state-of-the-art R on laboratory prototypes fi lms, for potential accelerator applications. entrance to accelerators using and actual accelerator components in operating facilities, SPIRAL2’s SR structures for with the clear long-term objective to enable superconduct- Sustaining success superconducting electrons orange, ing technology for a Te-scale linear collider. This objec- The mission of the TTC is to advance SRF technology R linear accelerator. protons purple tive demanded a staged approach and intense work on the and related accelerator studies across the broad diversity of and heavy ions development of all the many peripherals and subcompo- scientifi c applications. It is to provide a bridge for open com- pin. More nents. The collaboration embraced a joint eff ort between munication and sharing of ideas, development and testing than SR the initial partners to develop the TTF at ES, which aimed across associated projects. The TTC supports and encour- accelerators are in to demonstrate reliable operation of an electron super- a g e s t h e f r e e a n d o p e n e x c h a n g e o f s c ie nt i fi c a n d t e c h n ic a l operation circles, conducting linac at gradients above 1 Mm in vector knowledge, engineering designs and equipment. Further- approimately sum control – whereby many cavities are fed by a single more, it is based on cooperative work on SRF accelerator are presently high-power RF source to improve cost eff ectiveness. In 1993 technology by research groups at TTC member institution under construction the collaboration fi nalised a 1.3 GHz cavity design that is laboratories and test facilities. The current TTC membership triangles and still the baseline of large projects like the European FEL, consists of 60 laboratories and institutes in 12 countries more than LCLS-II and SHINE, and nearly all L-band-based facilities. across Europe, North America and Asia. Since progress in future proects cavity performance and related SRF technologies is so rapid, are under Toards a linear collider the major TTC meetings have been frequent. consideration A n i nt e n s e c ol l a b or at i v e e ff or t s t a r t e d for t h e d e v e lo p m e nt Particle accelerators using SRF technologies have been squares. of all peripheral components, for example power couplers, applied widely, from small facilities for medical appli- high-order mode dampers, digital low-level RF systems and cations up to large-scale projects for particle physics, cryomodules with unprecedented heat load performances. nuclear physics, neutron sources and free-electron lasers Several of these components were designed by TTC part- (see “Global view” fi gure). Five large-scale (> 100 cavities) ners in an open collaborative and competitive eff ort, and a SRF projects are currently under construction in three number of them can be found in existing projects around regions: ESS in Europe, FRIB and LCLS-II in the US, and uclear physics is as wide-ranging and relevant (CIME) added in 2001. The latter is used to reaccelerate the world. The tight requirements imposed by the scale of a SHIN E (C h i n a) a n d R AON (K or e a) i n A s i a. C lo s e i nt e r n at io n a l today as ever before in the century-long history short-lived nuclei produced using beams from the other linear collider required an integrated design of the acceler- collaboration will continue to support progress in these N of the subject. Researchers study exotic systems cyclotrons – the Système de Production d’Ions Radioactifs ating modules, containing the cavities and their peripheral and future projects, including SRF thin-fi lm technology from hydrogen-7 to the heaviest nuclides at the bounda- en Ligne (SPIRAL1) facility. The various beams produced components, which led to the concept of the TESLA style relevant for a possible future circular electron–positron ries of the nuclear landscape. By constraining the nuclear by these cyclotrons drive eight beams with specialised cryomodules, variants of which provide the building blocks collider. Perhaps the next wave of SRF technology will be equation of state using heavy-ion collisions, they peer instrumentation. Parallel operation allows the running of t he linacs in T TF, European XFEL, LCLS-II and SHINE. the maturation of economical small-scale applications inside stars in controlled laboratory tests. By studying of three experiments simultaneously, thereby optimising The success of the TTF, which delivered its fi rst beam with high multiplicity and international standards. As weak nuclear processes such as beta decays, they can even the available beam time. These facilities enable both high- in 1997, led it to become the driver for a next-generation an ultimate huge future SRF project, realising an ILC will probe the Standard Model of particle physics. And this is intensity stable-ion beams, from carbon-12 to uranium-238, light source at DESY, the VUV-FEL, which produced fi rst indeed require sustained broad international collaboration. not to mention numerous applications in accelerator-based and lower intensity radioactive-ion beams of short-lived light in 2005 and which later became the FLASH facility. The open and free-exchange model that for 30 years has atomic and condensed-matter physics, radiobiology and nuclei, with lifetimes from microseconds to milliseconds, The European FEL built on this strong heritage, its large enabled the TTC to make broad progress in SRF technol- industry. These nuclear-physics research areas are just a such as helium-6, helium-8, silicon-42 and nickel-68. THE AUTHORS scale demanding a new level of design consolidation and ogy is a major contribution to science diplomacy eff orts selection of the diverse work done at the Grand Accélérateur Coupled with advanced detectors, all these beams allow Patrick Dolégiéviez, industrialisation. It is remarkable to note that the total on a worldwide scale. e celebrate the many creative and National d’Ions Lourds (GANIL), in Caen, France. nuclei to be explored in terms of excitation energy, angular Robin Ferdinand number of such TESLA-style cavities installed or to be collaborative eff orts that have served the international GANIL has been operating since 1983, initially using four momentum and isospin. and Alahari Navin installed in presently approved accelerators is more than community well via the TESLA Technology Collaboration.  cyclotrons, with a fifthCyclotron pour Ions de Moyenne Energie The new SPIRAL2 facility, which is currently being GANIL.

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FEATURE RESEARCH FACILITIES FEATURE RESEARCH FACILITIES

The multifaceted physics criteria called for an original Multitasking GANIL design featuring a compact multi-cryostat structure for GANIL The nineteen the superconducting cavities, which was developed in superconducting collaboration with fellow French national organisations cryomodules of CEA and CNRS. Though the 19 cryomodules are compara- the SPIRAL2 linac. ble in number to the 23 employed by the larger and more powerful SNS accelerator, the new SPIRAL2 linac has far fewer accelerating gaps. On the other hand, compared to normal-conducting cavities such as those used by Linac4, the power consumption of the superconducting structures at SPI R A L 2 i s s i g n i fic a nt l y lo w e r, a n d t h e l i n a c c o n for m sto additional constraints on the cryostat’s design, operation and cleanliness. The choice of superconducting rather than High intensity SPIRAL2’s new superconducting linac and its experimental halls. room-temperature cavities is ultimately linked not only to the need for higher beam intensities and energies, but commissioned, will take this work into the next decade also to the potential for the larger apertures needed to and beyond. The most recent step forward is the beam reduce beam losses. commissioning of a new superconducting linac – a major Beams are produced using two specialised ion sources. upgrade to the existing infrastructure. Its maximum beam At 200 kW in continuous-wave (CW) mode, the beam power intensity of 5 mA, or 3 × 1016 particles per second, is more is high enough to make a hole in the vacuum chamber in than two orders of magnitude higher than at the previous less than 35 µs, placing additional severe restrictions on the facility. The new beams and state-of-the-art detectors will beam dynamics. The operation of high beam intensities, allow physicists to explore phenomena at the femtoscale up to 5 mA, also causes space-charge effects that need to right up to the astrophysical scale. be controlled to avoid a beam halo which could activate accelerator components and generate neutrons – a greater demonstration of the cavity performance at 8 MV/m – a t i n-1 2 4. He r e, g r o u n d-s t at e pr o p e r t ie s s uc h a s t h e m a s s o f Landmark facility difficulty in the case of deuteron beams. c o m p e t it i v e e le c t r ic fie ld w e l l a b o v e t h e r e q u i r e d6.5 MV/m. nuclei must be measured with a precision of one part in 109 SPIRAL2 was approved in 2005. It now joins a roster of For human safety and ease of technical maintenance, The first beam was injected into the linac in late October – a le v e l o f pr e c i s io n e q u i v a le nt t o o b s e r v i n g t h e a d d it io n o f cutting-edge European nuclear-physics-research facil- beam losses need to be kept below 1 W/m. Here, the SPIRAL2 2019. The cavities were tuned and a low-intensity 200 µA a pea to the weight of an Airbus A380. SPIRAL2’s low-energy ities which also features the Facility for Antiproton and design has synergies with several other high-power accel- beam of protons accelerated to the design value of 33 MeV experimental hall for the disintegration, excitation and Ion Research (FAIR), in Darmstadt, Germany, ISOLDE and erators, leading to improvements in the design of quar- and sent to a first test experiment in the neutrons for science storage of radioactive ions (DESIR), which is currently under nTOF at CERN, and the Joint Institute for Nuclear Research ter-wave resonator cavities. These are used at heavy-ion (NFS) area. A team from the Nuclear Physics Institute in c o n s t r uc t io n, w i l l f u r t h e r f a c i l it at e d e t a i le d s t ud ie s o f t h e (JINR) in Russia. Due to their importance in the European accelerators such as the Facility for Rare Isotope Beams Prague irradiated copper and targets and the products ground-state properties of exotic nuclei fed both by S3 and nuclear-physics roadmap, SPIRAL2 and FAIR are both in the US and the Rare Isotope Science Project in Korea; for m e d i n t h e r e a c t io n w e r e t r a n s p or t e d b y a f a s t-a ut o m at ic SPIRAL1, the existing upgraded reaccelerated exotic-beams now recognised as European Strategy Forum on Research for producing radioactive-ion beams and improving beam s y s t e m 40 m away, where their characteristic γ-d e c a y w a s facility. The commissioning of S3 is expected in 2023 and Infrastructures (ESFRI) Landmark projects, alongside 11 dynamics at intense-light particle accelerators worldwide; measured. Precise measurements of such cross-sections experiments in DESIR in 2025. In parallel, a continuous other facilities, including accelerator complexes such as for producing neutrons at the International Fusion Materials are important in order to benchmark safety codes required improvement in the SPIRAL2 facility will begin with the the European X-Ray Free-Electron Laser, and telescopes Irradiation Facility, the ESS, the Myrrha Multi-purpose for t he operat ion of nuclear reactors. integration of a new injector to substantially increase the such as the Square Kilometre Array. Hybrid Research Reactor for High-tech Applications, and SPIRAL2 is now moving towards its design power by intensit y of heav y-ion beams. Construction began in 2011. The project was planned in t h e SNS; a n d for a l a r g e r a n g e o f s t ud ie s r e l at i n g t o m at e r i a l s gradually increasing the proton beam current and sub- Thanks to its very high neutron flux – up to two orders two phases: the construction of a linac for very-high-in- properties and the generation of nuclear power. sequently the duty cycle of the beam – the ratio of pulse of magnitude higher, in the energy range between 1 and tensity stable beams, and the associated experimental duration to the period of the waveform. A similar procedure 40 M eV, t h a n at f a c i l it ie s l i k e L A NS C E at L o s A l a m o s, nT OF at h a l l s (s e e “H i g h i nt e n s it y” fi g u r e); a n d i n f r a s t r uc t u r e for Beam commissioning with alpha particles and deuteron beams will then follow. CERN and GELINA in Belgium – SPIRAL2 is also well suited t he reacceleration of shor t-lived fission frag ments, pro- Initial commissioning of the linac began by sending beams Physics programmes will begin in autumn next year. for a p pl ic at io n s s uc h a s t h e t r a n s mut at io n o f nuc le a r w a s t e duced using deuteron beams on a uranium target through from the injector to a dedicated system with various diag- in accelerator-driven systems, the design of present and one of the GANIL cyclotrons. Though the second phase is nostic elements. The injector was successfully commissioned Future physics next-generation nuclear reactors, and the effect of neu- currently on hold, SPIRAL2’s new superconducting linac with a range of CW beams, including a 5 mA proton beam, W it h t h e n e w s up e rc o n d uc t i n g l i n a c, SPI R A L 2 w i l l pr o v id e trons on materials and biological systems. Light-ion beams is now in a first phase of commissioning. a 2 mA alpha-, a 0.8 mA oxygen–ion beam intense beams from protons to nickel – up to 14.5 M eV/A for from the linac, including alpha particles and lithium-6 M o s t l i n a c s a r e o p t i m i s e d for a b e a m w it h s p e c i fic c h ar- and a 25 µA –ion beam. In each case, almost 100% heavy ions – and continuous and quasi-mono energetic and lithium-7 impinging on lead and bismuth targets, will acteristics, which is supplied time and again by an injector. transmission was achieved through the radio-frequency beams of neutrons up to 40 MeV. With state-of-the-art also be used to investigate more efficient methods for the T h e p a r t ic le s p e c ie s, v e lo c it y pr ofi le o f t h e p a r t ic le s b eing quadrupoles. Components of the linac were installed, the cry- instrumentation such as the Super Separator Spectrometer production of certain radioisotopes for cancer therapy. accelerated and beam intensity all tend to be fixed. By omodules cooled to liquid-helium temperatures (4.5 K), and (S3), t h e c h a r g e d p a r t ic le b e a m s w i l l a l lo w t h e s t ud y o f v e r y D e v e lo p m e nt s at SPI R A L 2 a r e q u ic k l y m o v i n g for w a rd s. Properties must tuning the phase of the electric fields in the accelerating the mechanical stability required to operate the 26 supercon- rare events in the intense background of the unreacted In September, the control of the full emittance and space– SPIRAL2 joins be measured structures, charged particles surf on the radio-frequency ducting cavities at their design specifications demonstrated. beam with a signal to background fraction of 1 in 1013. The c h a r g e e ffe c t s w a s d e m o n s t r at e d – a c r uc i a l s t e p t oreach a roster of with a level waves in the cavities with optimal efficiency in a single As GANIL is a nuclear installation, the injection of beams c h a r g e d p a r t ic le b e a m s w i l l a l s o c h a r a c t e r i s e e x o t ic nuc le i the design performance of the linac – and a first neutron cutting-edge pass. Though this is the case for most large projects, such into the linac required permission from the French nucle- w it h pr o p e r t ie s v e r y d i ffe r e nt f r o m t h o s e fo u n d i n n at ure. beam was produced at NFS, using proton beams. The future of precision European as Linac4 at CERN, the Spallation Neutron Source (SNS) ar-safety authority. Following a rigorous six-year author- T h i s w i l l a d d r e s s q ue s t io n s r e l at e d t o h e a v y a n d s up e r-h e a v y looks bright. With the new SPIRAL2 superconducting linac equivalent to nuclear- in the US and the European Spallation Source in Sweden isation process, commissioning through the linac began e le m e nt /i s o t o p e s y nt h e s i s at t h e e x t r e m e b o u n d a r ie s o f t h e now supplementing the existing cyclotrons, GANIL pro- observing the physics- (CERN Courier September/October 2020 p29), SPIRAL2’s in July 2019. An additional prerequisite was that a large periodic table, and the properties of nuclei such as tin-100, vides an intensity and variety of beams that is unmatched addition of a pea research linac (see “Multitasking” figure) has been designed for a number of safety systems be validated and put into oper- wh ic h have t he sa me numb er of neut rons a nd protons – a in a single laboratory, making it a uniquely multi- to the weight of facilities wide range of ions, energies and intensities. ation. The key commissioning step completed so far is the far cry from naturally existing isotopes such as tin-112 and disciplinar y facilit y in t he world today.  an Airbus A380

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A unique period for computing, but will it last?

The i nc rea se i n comput i ng dem a nd s CERN-CO-0101012-01 expected this decade puts high-energy phy sic s i n a si m i l a r p osit ion to 1995 w he n the field moved to PCs, argues Sverre Jarp.

Twenty-five years ago in Rio de Janeiro, N Ja r p at the 8th International Conference on Comput i ng i n Hig h-Energ y a nd Nuc lea r Physics (CHEP-95), I presented a paper on behalf of my research team titled “The PC as Physics Computer for LHC”. We h i g h l i g ht e d i m pr e s s i v e i m pr o v e m e nt s in price and performance compared to o t h e r s olut i o n s o n o ffe r. I n t h e y e a r s t ha Stack ’em high Monica Marinucci and Ivan Deloose at CERN’s PC farm in 2001. Sverre Jarp fol l o w e d, t h e c o m mu n it y s t a r t e d m o v i n g worked at CERN for t o P C s i n a m a s s i v e w a y, a n d t o d a y t h e P C little more than a decade. After 2006, had no idea that the PC would remain an more than 40 years, rema i n s unc ha l lenge d a s t he work horse when speed increases became impossible uncontested winner during a quarter of during which he for h i g h- e n e r g y p h y s i c s (H E P) c o m p ut i n g. for thermal reasons, efforts moved to a century of scientific computing. The held many different H E P- c o m p ut i n g d e m a n d s h a v e a l w a y s producing multi-core chips. However, q u e s t io n i s w h e t h e r it w i l l l a s t for a n o t h e r positions, including been greater than the available capac- H E P c o nt i nu e d t o pr o fit. Si n c e a l l p h y s ics quarter century? CTO of CERN ity. However, our community does not events at colliders such as the LHC are openlab from have the financial clout to dictate the independent of all others, it was suf- The contenders 2002 until 2014. w a y c o m p ut i n g s h o u l d e v ol v e, d e m a n d- ficient to split a job into multiple jobs The end of CPU scaling, argued a recent ing constant innovation and research in across all cores. r e p or t b y t h e H E P S o f t w a r e Fo u n d a t io n, c o m p ut i n g a n d I T t o m a i nt a i n pr o g r e s s. The HEP community was also lucky demands radical changes in computing A fe w y e a r s b e for e C H E P-95, R IS C w or k- with software. Back in 1995 we had and software to ensure the success of stations and servers had started comple- chosen Windows/NT as the operating the LHC and other experiments into the Hadron colliders and Luvata, menting the mainframes that had been system, mainly because it supported 2020s and beyond (CERN Courier April acquired at high cost at the start-up of multiprocessing, which significantly 2018 p39). There are many contenders LEP in 1989. We thought we could do even e n h a n c e d o u r pr ic e/ p e r for m a n c e. P h y s i- that would like to replace the x86 PC relationships that go back 50 years. b e t t e r t h a n R IS C. T h e i n c r e a s e d- e n e r g y cists, however, insisted on Unix. In 1991, architecture. It could be graphics proces- L E P 2 p h a s e n e e d e d l o t s o f s i m u l a t i o n, a n d Linus Thorvalds released Linux version sors, where both Intel, AMD and Nvidia Luvata is a combination of metallurgical expertise, Whether you are looking for high-purity oxygen-free t h e s a m e n e e d s w e r e a l r e a d y m a n i fe s t for 0.01 and it quickly gathered momen- are active. A wilder guess is quantum application know-how and close customer copper or alternative alloys that offer higher t h e L HC. T h e s e w e r e o u r i n s pi r a t i o n s t h a t tum as a worldwide open-source pro- computing, whereas a more conservative relationships coming together to make the most strength, Luvata makes the unique shape and led PC servers to start populating our j e c t. W h e n r e le a s e 2.0 a p p e a r e d i n 1996, guess would be processors similar to the of metal. For nearly sixty years, Luvata has been size you are looking for. c o m p ut e r c e nt r e s – a m o v e t h a t w a s a l s o multiprocessing support was included x86, but based on other architectures, helped by a fair amount of luc k. and the operating system was quickly suc h as A R M or RISC-V. manufacturing copper hollow conductors for the adopted by our community. During the PC project we collabo- most demanding applications. Luvata joins in celebrating 50 years of hadron Fast change Furthermore, HEP adopted the Grid rated with Hewlett-Packard, which had colliders and we look forward to the science and HEP programs need good floating-point c o n c e p t t o c o p e w it h t h e d e m a n d s o f t h e a division in Grenoble, not too far away. discovery of the next five decades. The end of compute capabilities and early genera- LHC. Thanks to projects such as Ena- Such R&D collaborations have been vital CPU scaling tions of the Intel x86 processors, such bling Grids for E-science, we built the to CERN and the community since the as the 486/487 chips, offered mediocre Worldwide LHC Computing Grid, which b e g i n n i n g a n d t h e y r e m a i n s o t o d a y. T h e y demands capabilities. The Pentium processors that today handles more than two million a l low us to get i n sig ht i nto for t hcom i ng radical emerged in the mid-1990s changed the tasks across one million PC cores every pr o d u c t s a n d f ut u r e pl a n s, w h i l e o u r fe e d- www.luvata.com/cern-courier-nov2020 changes to s c e n e s i g n i fic a nt l y, a n d t h e c o m p e t it ive 24 hours. Although grid computing b a c k c a n h e l p t o i n flu e n c e t h e pr o d u c t s in ensure the r a c e b e t w e e n I nt e l a n d A M D w a s a m aj or remained mainly amongst scientific pl a n. C E R N o p e n l a b, w h i c h h a s b e e n t h e success of driver of continued hardware innovation. users, the analogous concept of cloud fo c a l p oi nt for s u c h c ol l a b or a t i o n s for t w o Another strong tailwind came from computing had the same cementing d e c a d e s, e a rl y- o n c oi n e d t h e p h r a s e “Yo u the LHC and the relentless efforts to shrink tran- effect across industry. Today, all the make it, we break it”. However, whatever other high- sistor sizes in line with Moore’s law, major cloud-computing providers over- t he f ut u re hold s, it i s f a i r to a s su me t h at luvata.com energy physics which saw processor speeds increase whelmingly rely on PC ser vers. PCs will remain the workhorse for HEP experiments from 50/100 MHz to 2000/3000 MHz in I n 1995 w e h a d s e e n a g l i m m e r, b ut w e comput ing for many years to come.

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pumpsFind the information you needin from opticsIOP Publishing’s vacuum chambers world-leading journals and award-winning books Vacuumprogramme, engineers along and with scientists conference have proceedings long and knownscience that news even from if a sample Physics material World. is In pursuit of the possible initially clean and handled with ultrahigh- vacuumiopscience.org/particle-and-nuclear-physics (UHV) standards, a carbon contamination layer will deposit and grow on Theorist Giulia Zanderighi, collider phenomenologist and director at the Max Planck Institute for the material’s surface after placing it in a high Physics, discusses fundamental physics at the boundary between theory and experiment. vacuum (HV) or UHV chamber. This condition

is also true for the optics vacuum chambers Griesch/MPP A found in particle accelerators and synchrotron What do collider phenomenologists do? the International Max Planck Research beamlines. For the optics vacuum chambers, I tend to prefer the term particle Schools for PhD students. Our institute this situation is worsened by X-ray irradiation, phenomenology because the collider in Munich is a very unique place. One which can result in a one to two orders is just the tool that we use. However, can feel it immediately. As a guest in of magnitude pressure increase and high compared to other experiments, such the theory department, for example, yield of carbon contaminants. The effects of as those searching for dark matter or you get to sit in t he Heisenberg office, carbon contamination on the X-ray optics can axions, colliders provide a controlled which feels like going back in time. Our significantly reduce the X-ray transmission laboratory where you decide how institute was founded in Berlin in 1917 downstream to the experimental stations, carbon K edge, around 285 eV, as well as at conditions. Carbon contamination is not only many collisions and what energy w it h A lber t Einstein as a first director. and as next-generation synchrotrons usher higher energies around 1000 eV. As early as experimentally detected; it is also visually these collisions should have. This is In 1958 the institute moved to Munich in X-ray brightness increases of two to three the 1980s, this carbon contamination layer evident after a few months to a year of quite unique. Today, accelerators and with Werner Heisenberg as director. orders of magnitude, it is critical to minimize was shown to cause intensity modulations beamline operation. It will usually appear as a detectors have reached an immense A f ter more t han 100 years I’m t he first these losses from carbon contamination. in X-ray absorption spectra that closely black line where the X-rays strike the optics. level of sophistication, and this female director, which of course is a resembled those above the carbon K edge allows us to perform a vast amount of great responsibility. But I also really Read the full paper online. Multiple studies have shown that carbon in bulk crystalline graphite. These results fundamental measurements. So, the loved both CERN and Oxford. At CERN I contamination develops on X-ray optics and suggested the formation of graphitic SAES Group S.p.A field spans precision measurements of felt like I was at the centre of the world. reduces the transmission of photons near the carbon contamination even under UHV Web www.saesgroup.com fundamental properties of particles, It is such a vibrant environment, and I in particular of the Higgs boson, loved the proximity to the experiments consistency tests of the Standard Model and the chats in the cafeteria about (SM), direct and indirect searches for calculations or measurements. In new physics, measurements of rare done even at future proposed lepton Giulia Zanderighi Oxford I loved the multidisciplinary decays, and much more. For essentially colliders. Furthermore, by picking up the aspect, the dinners in college sitting all these topics we have had new a lepton from one proton and a quark department of novel next to other academics working in results in recent years, so it’s a very from the other proton, one can place computational completely different fields. I g uess I’m act ive and cont inuously evolv ing field. new constraints on leptoquarks, and techniques lucky that I’ve been in so many and Particle and But of course we do not just measure plenty of other things. This idea was in particle suc h different places. things for the sake of it. We have big, already proposed in the 1990s, but phenomenology at fundamental questions and we are was essentially forgotten because the the Max Planck What is the biggest challenge to nuclear physics looking for hints from LHC data as to lepton PDF was not known. Now we Institute for Physics reach higher precision in how to address them. know this very precisely, bringing new in Munich. quantum-field-theory calculations possibilities. But let me stress that this of key SM processes? What’s hot in the field today? is just one idea – there are many other The biggest challenge is that often Find the information you need from IOP One topic that I think is very cool is new ideas out there. For instance, one there is no single biggest challenge. Publishing’s world-leading journals and that we can benefit from the LHC, in its major branch of phenomenology is to For instance, for inclusive Higgs- current setup, also as lepton collider. use machine learning or deep learning boson production we have a number award-winning books programme, along with In fact, at the LHC we are looking at to recognise the SM and extract from of theoretical uncertainties, but they conference proceedings and science news elementary collisions between the data what is not SM-like. are all quite comparable in size. This proton’s constituents, quarks and means that to reduce the overall from Physics World. gluons. But since the proton is charged, How does the Max Planck Institute uncertainty considerably, one needs it also emits photons, and one can talk differ from your previous positions, to reduce all uncertainties, and they about the photon parton-distribution for example at CERN and Oxford? all have ver y different physics orig ins Publish with us function (PDF), i.e. the photonic A long time ago, somebody told me that and difficulties – from a better We offer a range of publishing options to suit your content of protons. These photons can the best thing that can happen to you in understanding of the incoming parton split into lepton pairs, so when one Germany is the Max Planck Society. It’s densities and a better knowledge of the needs, ensuring that your work gets the attention that collides protons one is also colliding true. You are given independence and strong coupling constant, to higher it deserves. leptons. The fascinating thing is that the means to fully focus on research order QCD or elect rowea k effects and the “content” of leptons in protons is and ideas, largely free of teaching duties effects related to heav y par t icles in rather democratic, so one can look at or the need to apply for grants. Also, virtual loops, etc. Computing power iopscience.org/particle-and-nuclear-physics collisions between, say, a muon and a there are very valuable interactions can be a liming factor for certain tau lepton – something that can’t be with universities, be it in research or via calculations, so making things

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numerically more efficient is also D Dominguez/CERN Is naturalness a good guiding force in impor tant. One of t he main goals of fundamental research? REVIEWS t he coming year w ill be t he calculat ion Yes. We have plent y of e xamples of t wo to t hree scat tering processes at where nat uralness, in t he sense of a t he LHC at ne x t-to-ne x t-to-leading quadrat ic sensit iv it y to an un k now n order (NNLO) in QCD. For instance, a ultraviolet scale, leads to postulating milestone w ill be t he calculat ion of a new par t icle: t he energ y of t he top-pair product ion in associat ion w it h elect ron field (leading to t he posit ron), a Higgs boson at t hat level of accurac y. t he c harged and neut ral mass Weinberg on astrophysics This is t he process where we can difference (leading to t he rho-meson)

measure most direct ly t he top-Yukaw a or t he kaon t ransit ion rates and R Rubio/Virgo Collaboration coupling. The impor tance of t his mi x ing, whic h led to t he post ulat ion Lectures on Astrophysics measurement can’t be overst ressed. of t he e x istence of t he c har m quark By Steven Weinberg While t he big discover y at t he LHC is in 1970, before its direct discover y so far t he Higgs boson, one should also in 1974 at SL AC and Brook haven. In Cambr idge Universit y Press remember t hat t he Yukaw a interact ion ever yday li fe we constant ly assume is a new t y pe of f undamental nat uralness, so yes, it is puzzling t hat Typical introductions to astrophys- interaction, which is proportional Loops and legs Calculating scattering processes at the LHC at t he Higgs mass appears to be fine- ics range from 500 to more than 1000 to t he mass of t he par t icle, just li ke next-to-next-to-leading order in QCD is a high priority for the field. t uned. Cer tainly, t here is a lot we st ill pages. This trend is at odds with many g rav it y, but yet so different from don’t understand here, but I would not of today’s students, who prepare for g rav it y. For some calculat ions, NNLO is quic k ly at t he LHC. Now t hings give up on naturalness, at least not that examinations using search engines and already enough in ter ms of per t urbat ive have turned out to be different, but easily. In t he case of t he elect rowea k a r e o f t e n p ut o ff b y p o n d e r o u s t r e a t i s es. precision; going to N 3LO doesn’t really this is what makes it exciting and nat uralness problem, it is clear t hat St e v e n We i n b e r g’s n e w b o o k w i s e l y g o e s add muc h yet. But t here are a few cases c halleng ing – even more so, because any solution, such as i n t h e o p p o s it e d i r e c t i o n. T h e 1979 No b e l where it helps already, such as super- t he same mysteries are st ill t here. or compositeness, w ill also leave an laureate, and winner last week of a spe- clean Drell–Yan processes. We have big, fundamental questions. imprint in the Higgs couplings. So c i a l Br e a k t h r o u g h pr i z e i n f u n d a m e nt a l We have hints from t heor y, from t he LHC can, in principle, tell us about physics, has written a self-contained and Is there a level of precision of LHC experiments. We have a powerful, nat uralness even i f we do not discover relatively short 214-page account of the measurements beyond which indirect multi-purpose machine – the LHC new physics directly; we just have to foundations of astrophysics, from stars to searches for new physics are no – that is only just getting started measure ver y precisely i f t he Higgs galaxies. The result is extremely pleasant Unexpected Earlier this month, LIGO and Virgo observed gravitational waves from the most massive longer fruitful? and will provide much more data. Of boson couplings align on a straight line and particularly suitable for students and black-hole merger seen so far, between 66 and 85 solar-mass black holes – an astrophysical event thought We will never rule out precision course, e x pectat ions li ke t he quic k in the mass-versus-coupling plane. young practitioners in the field. to be physically impossible. measurements as a route to search for discovery of supersymmetry have not Instead of building a large treatise, new physics. We can always extend been f ulfilled, but nat ure is how it is. I Which collider should follow the LHC? Weinberg prioritises key topics that numerical computations that are mostly bibliography at the end of each chapter. the reach and enhance the sensitivity t hin k t hat prog ress in physics is driven That is the billion-dollar question – I appeared in a set of lectures taught by p e r for m e d b y c o m p ut e r s. B y t h e a ut h or’s St e v e n We i n b e r g’s b o o k s a l w a y s s t i m- of indirect searches. By increasing by e x periments. We have beaut i f ul mean, the 25 billion-dollar question! the author at the University of Texas at o w n a d m i s s i o n, h o w e v e r, t h i s b o o k i s pr i- ulate a wealth of considerations on the precision, we are e x ploring deeper in exceptions where progress comes To me one should go for the machines Austin. The book has four parts, which m a r i l y i nt e n d e d for t h o s e w h o c a r e a b o ut mutual interplay of particle physics, the ultraviolet region, where we can from theory, like general relativity, that explore as much as possible the deal with stars, binaries, the interstel- the rationale of astrophysical formulas astrophysics and cosmology, and the start to become sensitive to states or t he post ulat ion of t he mec hanism new energ y front ier, namely a 100 TeV lar medium and galaxies, respectively. and their applications. problems of dark matter, dark energy, e xc hanged in t he loops t hat are more for electroweak symmetry breaking. hadron collider. It is a compromise The analysis of stellar structure starts This monograph is also a valid occa- gravitational waves and neutrino masses and more heav y. There is a limit, but When I t hin k about t he Higgs bet ween what we might be able to from the study of hydrostatic equilibrium s io n for p a y i n g t r i b ut e t o a c ol l e c t io n o f are today so interlocked that it is quite we are ver y far from it. It’s li ke look ing mechanism, I am still astonished ac hieve from a mac hine-building/ and is complemented by various classic classic treatises that inspired the current difficult to say where particle physics with a better and better microscope: that such a simple and powerful idea accelerator/engineering point of view discussions including the mechanisms astrophysical literature and that are still s t o p s a n d a s t r o p h y s i c s t a k e s o v e r. M o d- t he bet ter t he resolut ion, t he more postulated in 1964 turns out to be and really exploring a new frontier. for nuclear energy generation and the rather popular among the practition- ern science calls for multidisciplinary one can e x plore. However, t he realised in nature. But these cases, For instance, at a 100 TeV machine one Hertzsprung–Russell diagram. In view ers of the field. The author reveals in approaches, and while the frontiers experimental precision has to go hand where theory precedes experiments, can measure the Higgs self-coupling, o f t h e s t r i k i n g o b s e r v a t i o n s i n 2015 b y t h e his preface that his interest in stellar between the different areas are now in hand with theoretical precision, are the exception not the rule. In most which is intimately connected with the LIGO and Virgo interferometers, the sec- structure started many years ago after fading away, the potential discovery of and t his is where t he real c hallenge for cases prog ress in physics comes from Higgs potential and to the profound ond part contains a dedicated discussion reading the celebrated book of Subrah- new laws of nature will not only proceed phenomenologists lies. Of course, if observations. After all, it is a natural question of the stability of the vacuum. of the emission of gravitational waves by manyan Chandrasekhar (An introduction from concrete observational efforts but you have a super precise measurement science, it is not mathematics. bina r y pulsa rs a nd coa lesc ing bina r ies. to Stellar Structure), which was reprinted also from the correct interpretation of the but no theory prediction, or vice versa, There are some questions that Which open question would you most As you might expect from the classic by Dover in the late 1950s. Similarly, the existing theories. If we want to under- then you can’t do much with it. With are really tough, and we may never like to see answered during your career? s t y l e o f We i n b e r g’s m o n o g r a p h s, t h e b o o k discussions on the interstellar medium stand the developments of fundamental the Higgs boson I am confident that real ly see an answer to. But w it h t he Probably t he nat ure of dark mat ter. The provides readers with a kit of analytic are inspired by the equally famous physics in the coming years, Lectures on the theory calculations will not be LHC t here are many ot her smaller presence of da rk mat ter is over whel m i ng tools of permanent value. His approach m o n o g r a p h o f Ly m a n S pit z e r Jr. (Physical Astrophysics w i l l b e a n i n s pi r i n g s o u r c e o f In most cases t he deal brea ker. We w ill event ually questions we certainly can address, in t he universe and it is embar rassing contrasts with many modern astrophysics Processes in the Interstellar Medium 1978, reflect ions and a v alid reference. hit t he w all in ter ms of e x perimental progress such as understanding the proton t hat we k now lit t le to not hing about and particle-theory texts, where analyti- J. W i le y & S on s). For t he b e ne fit of c u r i- precision, but you can’t put a figure on in physics structure or studying the interaction its nat ure and proper t ies. There are cal derivations and back-of-the-envelope ous and alert readers, these as well as Massimo Giovannini CERN and where t his w ill happen. Unt il you see a comes from potential between and many exciting possibilities, ranging approximations are often replaced by other texts are cited in the essential INFN Milano-Bicocca. deviation you are never really done. observations. strange , which are relevant from t he lightest neut ral states in After all, it to understand the physics of neutron new-physics models to a non-par t icle- How to find a Higgs boson – Finding Higgs bosons can seem eso- A realistic you experience similar difficulties in How would you characterise the state stars, and t hese are st ill adv ancing li ke inter pretat ion, li ke blac k holes. and other big mysteries in the teric to the uninitiated. The spouse of representation describing what you do to loved ones? is a natural world of the very small of particle physics today? knowledge. The brightest minds are Eit her w ay, an answer to t his quest ion a colleague of mine has such trouble of what it’s like If so, then Ivo van Vulpen’s book How to When I entered the field as a student, science, attracted to the biggest problems, would be an incredible breakthrough. d e s c r i bi n g w h a t t h e i r p a r t n e r d o e s t h a t find a Higgs boson may provide you with By Ivo van Vulpen to be a particle t here were high e x pectat ions t hat it is not and this will always draw young they read from a card in the event that an ideal gift opportunity. s supersymmetry would be discovered mathematics researchers into the field. Interview by Matthew Chalmers. Yale they are questioned on the subject. Do physicist R e a d e r s w i l l fe e l l i k e t h e y a r e t a l k-

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ber of electrons in an , and even North Pole explorer who sets out with hogwash, he writes, in the English EBAMed translation by David McKay. Sociological Accelerator engineer realities such as “mixed CMS–ATLAS” Adriano Garonna is CEO and couples temper the physics, which is co-founder of EBAMed, which unabashedly challenging and unvar- nished. The book boasts a particularly is developing technologies lucid and intelligible description of to enable non-invasive particle detectors for the general reader, and has a nice focus on applications. treatments of heart arrhythmia Particle accelerators are discussed in using proton beams. relation to the “colour X-rays” of the Medipix project. Spin in the context In December last year, a beam of protons was of MRI. Radioactivity with reference used to treat a patient with cardiac arrhythmia to locating blocked arteries. Antimat- – an irregular beating of the heart that affects ter in the context of PET scans. Key around 15 million people in Europe and North ideas are brought to life in cartoons America alone. The successful procedure, per- by Serena Oggero, formerly of the formed at the National Center of Oncological LHCb collaboration. Hadrontherapy (CNAO) in Italy, signalled a new Attentive readers will occasionally application of proton therapy, which has been be frustrated. For example, despite a used to treat upwards of 170,000 cancer patients Physicists at heart EBAMed’s technical team (left to right: Saskia Camps, Rosalind Perrin, stated aim of the book being to fight worldwide since the early 1990s. Jérémie Gringet and Adriano Garonna) at the Campus Biotech Innovation Park in Geneva. “formulaphobia”, Bohr’s famous recipe In parallel to CNAO – which is based on accel- for energy levels lacks the crucial minus erator technologies developed in conjunction development and the first human tests. at CERN. “At CERN most of my projects involved sign just a few lines before a listing of with CERN via the TERA Foundation (CERN Courier Garonna’s professional journey began when he e x pl or i n g n e w a r e a s. W h i l e I b e n e fit t e d f r o m t he –3.6 eV (as opposed to –13.6 eV) for the January/February 2018 p25) – a Geneva-based was a summer student at CERN in 2007, working support of my supervisors, I had to drive projects energy of the ground state. Van Vulpen start-up called EBAMed (External Beam Ablation) on user-interface software for a new optical on my own, seek the right solutions and build compares the beauty seen by physicists founded by CERN alumnus Adriano Garonna aims position-monitoring system at LHC Point 5 the appropriate ecosystem to obtain results. in equations to the beauty glimpsed by to develop and commercialise image-guidance (CMS). Following his graduation, Garonna This certainly developed an initiative-driven, musicians as they read sheet music, but solutions for non-invasive treatments of heart returned to CERN as a PhD student with the TERA entrepreneurial streak in me.” then prints Einstein’s field equations arrhythmias. EBAMed’s technology is centred Foundation and École Polytechnique Fédérale with half the tensor indices missing. on an ultrasound imaging system that mon- de Lausanne, and then as a fellow working for Healthy competition But to quibble about typos in the English itors a patient’s heart activity, interprets the the programme PARTNER, a train- Proton therapy is booming, with almost 100 translation would be to miss the point motion in real time and sends a signal to the ing network for European radiotherapy. This facilities operating worldwide and more than 35 of the book, which is to allow readers proton-therapy machine when the radiation led to a position as head of therapy accelerator under construction. EBAMed’s equipment can be “to impress friends over a drink,” should be sent. Once targeted, the proton beam commissioning at MedAustron in Austria – a installed in any proton-therapy centre irrespec- and talk physics “next time you’re in ablates specific heart tissues to stop the local facility for proton and ion therapy based, like tive of its technology, says Garonna. “We already a bar”. Van Vulpen’s writing is always conduction of disrupted electrical signals. CNAO, on TERA Foundation/CERN technology. have prospective patients contacting us as they entertaining, but never condescending. A f t e r h e l pi n g d e l i v e r t h e fi r s t p a t i e nt t r e a t m e nt s h a v e h e a rd o f o u r d e v i c e a n d w i s h t o b e n e fit f r o m Filled with amusing but perceptive Fast learner at MedAustron, Garonna returned to CERN and the treatment. As a company, we want to be the one-liners, the book is perfectly cal- “Our challenge was to find a solution using entered informal discussions with TERA founder leaders in our field. We do have a US compet itor, ibrated for readers who don’t usually the precision of proton therapy on a fast and Ugo Amaldi, who was one of Garonna’s PhD who has developed a planning system using con- enjoy science. Life in a civilisation irregular moving target: the heart,” explains supervisors, about how to take the technol- ventional radiotherapy, and we are grateful that that evolved before supernovas would Garonna. “The device senses motion at a very ogy further. Along with former CERN engineer there is another player on the market as it helps have no cutlery, he observes. Neutri- fast rate, and we use machine learning to inter- Giovanni Leo and arrhythmia expert Douglas pave the way to non-invasive treatments. Addi- nos are the David Bowie of particles. pret the images in real time, which allows robust Packer, the group founded EBAMed in 2018. tionally, it is dangerous to be alone, as that could The weak interaction is like a dog on an decision-making.” Unlike current treatments, “Becoming an entrepreneur was not my initial imply t hat t here is no market in t he first place.” attometre-long chain. which can be lengthy and costly, he adds, people purpose, but I was fascinated by the project and Leaving the security of a job to risk it all with This book could be the perfect gift for can be treated as outpatients; the intervention convinced that a start-up was the best vehicle a start-up is a gradual process, says Garonna. a curious spouse. But beware: fielding is non-invasive and “completely pain-free”. to bring it to market,” says Garonna. Not having “It’s definitely challenging to jump into what questions on the excellent last chapter, The recipient of several awards – including a business background, he benefitted from the seems like cold water… you have to think if it which takes in supersymmetry, SO(10), TOP 100 Swiss Startups 2019, Venture Busi- CERN Knowledge Transfer entrepreneurship is worth the journey. If you believe in what you and millimetre-scale extra dimensions, ness Plan 2018, MassChallenge 2018, Venture seminars as well as the support from the Geneva are doing, I think it will be worth it.” may require some revision. Kick 2018 and IMD 2017 Start-up Competition incubator Fongit and courses organised by Inno- – EBAMed recently received a €2.4 million suisse, the Swiss innovation agency. Garonna Craig Edwards (based on materials published by Mark Rayner associate editor. grant from the European Union to fund product also drew on previous experience gained while the Office for CERN Alumni Relations).

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CERN appoints new directors 2021 APS awards “for key insights into the structure of sustainable CERN Several outstanding particle and interactions of hadrons nuclear energy For advertising enquiries, contact CERN Courier recruitment/classified, IOP Publishing, Temple Circus, Temple Way, Bristol BS1 6HG, UK. physicists have been recognised and nuclei using numerical use and Tel +44 (0)117 930 1264 E-mail sales@cer ncourier.com. by the 2021 spring awards of and analytical methods”. The natural-gas Please contact us for information about rates, colour options, publication dates and deadlines. the American Physical Society Edward A Bouchet award, which pyrolysis”.

(APS). The W K H Panofsky promotes the participation of Lindau Nobel Laureate Meeting The 39 million Prize in experimental particle underrepresented minorities rouble physics has been awarded to in physics, has been awarded to ($0.5 million) R Bello/CERN Henry Sobel (pictured below Chanda Prescod-Weinstein of award was Looking forward to a fresh start in 2021? left) of the University of the University of New Hampshire announced on California, Irvine and Edward (below right) for her contributions 8 September in Kaluga, Russia by CERN offers unique student, graduate and professional opportunities Kearns of Boston University the Global Energy Association. MIT/Univ. New Hampshire New MIT/Univ. (below right) for pioneering and Rubbia is more widely known in engineering, computing and technology. leadership contributions to large as the winner, alongside Simon underground experiments for the van der Meer, of the 1984 Nobel Take a look and join an Organization like nowhere else on earth. Following the re-election discovery of neutrino oscillations Prize in Physics, for using the of Fabiola Gianotti as CERN and sensitive searches for SPS to discover the W and Z Director-General last year, the number violation. The J J Sakurai bosons, before being appointed CERN. Take part! CERN Council has approved the Prize for theoretical particle CERN Director-General in 1989. https://careers.cern appointment of four directors physics has been given to Vernon There have been 42 winners for the period 2021–2025. Mike Barger (bottom left) of University to theoretical cosmology of the annual prize, with 78 Lamont (pictured top left), a CERN of Wisconsin-Madison for and particle physics, and for scientists from 20 countries accelerator physicist of more pioneering work in collider physics co-creating the Particles for put forward this year. Previous than 30 years and former deputy contributing to the discovery and Justice movement. winners include former CERN

head of the beams department, Scott UCI/C The Herman Feshbach Prize in Director-General, Robert Aymar, has replaced Frédérick Bordry theoretical nuclear physics has who was recognised in 2006 for as director for accelerators and been awarded to Berndt Mueller of work to develop the scientific and technology. Joachim Mnich Brookhaven National Laboratory engineering foundation of the (top right), who worked on the (below left) for his contributions ITER project. at LEP and has to the identification of quark– been director of particle physics gluon plasma signatures, while Pontifical appointment at DESY since 2009, succeeds the 2021 Henry Primakoff Award On 29 September, Pope Eckhard Elsen as director for for early-career particle physics Francis appointed CERN research and computing. Raphaël characterisation of the W boson, has gone to Jaroslav Trnka of the Director-General Fabiola Gianotti Bello (lower left), formerly a top quark and Higgs boson, and University of California, Davis to the Pontifical Academy of representative for France at the for the development of incisive (below right) for seminal work Sciences. Candidates for a seat in European Bank for Reconstruction strategies to test theoretical on the computation of particle the academy are chosen “on the

and Development, is the new ideas with experiments. In BNL/UC Davies basis of their eminent original director for finance and human the field of accelerators, Yuri scientific studies and of their resources, replacing Martin Fyodorovich Orlov (below right), acknowledged moral personality, Steinacher. Charlotte Warakaulle formerly of Cornell University, without any ethnical or religious

(lower right), who joined CERN in was awarded the Robert R Wilson CERN 2016, is reappointed as director Prize for his pioneering for international relations. innovation in accelerator theory and practice. Orlov received the CMS management change news shortly before his passing on CERN The CMS 27 September. scattering amplitudes. Finally, collaboration Phiala E Shanahan of MIT the 2020 Dwight Nicholson has announced (above left) has been granted Medal for Outreach has been Discover what’s out there its new the 2021 Maria Goeppert Mayer given to Michael Barnett of management Award, which recognises an Lawrence Berkeley National for the period outstanding contribution to Laboratory (not pictured) “for Take the next step in your career 2020–2022. physics research by a woman, bringing the discoveries and discrimination”. The body has Former deputy searches of particle physicists formally existed since 1936 but with Physics World Jobs. Univ. Wisconsin-Madison/Cornell spokesperson and cosmologists to multitudes of its origins go back to 1603 with Luca Malgeri students and lay-people around the founding of the Accademia (pictured), who has been a CMS the world”. dei Lincei, to which Galileo Galilei physicsworld.com/jobs member since 2003, is now was one of the first appointees. spokesperson, with Gautier Rubbia wins energy prize Other ordinary members of Hamel de Monchenault and Carlo Rubbia is one of three the academy today include Jim Olsen appointed deputy winners of the 2020 Global Carlo Rubbia, Ed Witten and spokespersons. Energy Prize for “the promotion Juan Maldacena.

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advertentie CERN 193mmx130mm.indd 1 2020-10-19 11:09:52 CERNCOURIER www. V o l u m e 6 0 N u m b e r 6 N o v e mber /D e c e m b e r 2 0 2 0 CERNCOURIER.COM CERNCOURIER.COM PEOPLE PEOPLE OBITUARIES (EMC), which would go on to do experiments in ALEPH experiment at CERN’s Large Electron students. Following his retirement from RAL, OBITUARIES the high-intensity muon beam at CERN. Positron collider, LEP. The group undertook he was appointed visiting professor at Imperial As NINA came to the end of its life and Dares- the task of building the end-cap electromag- where he was lead author on the publication bury moved to host one of the first dedicated netic calorimeters, which worked successfully of the final ALEPH W-mass measurements. He “light sources”, John moved with other colleagues during the 11 years of ALEPH operations. John continued to advise and guide students, and took in particle physics to RAL. Interested in the pro- became heavily involved with early results for charge of graduate lectures until recently, when Horst Wenninger 1938–2020 duction of high-energy photons at the EMC, he which the calorimeter performance was crucial, f a i l i n g h e a l t h m a d e it d i ffic u l t for h i m t o d oso. organised the transfer of the LAMP lead–glass such as its use in counting the number of neu- John was a first rate, hands-on experimen- array from the UK to CERN to study the production trino species from the radiative return reaction tal physicist. He had a talent for understanding Relishing the CERN adventure of photon s i n t he for w a rd d i re c t ion. In t he fi n a l e+e– → ν– ν γ. During the LEP2 period in the late the difficulties of others and involving himself phase of the EMC activities he successfully led 1990s, John’s major contribution concerned the selflessly to help them progress. He always had Former CERN director Horst Wenninger, who CERN decision. His cryptic reaction was conveniently a team from RAL that implemented the change m e a s u r e m e nt o f t h e W m a s s a n d w id t h. T h i s l e d a patient, calm, happy and relaxed manner, and played key roles in the approval of the LHC and in interpreted by the supportive German delegate to a polarised target – a very difficult procedure to a highly productive collaboration between will be sadly missed. establishing knowledge transfer at CERN, passed as a green light, a determined move for the good that had to be done in just a few months. the Imperial College and RAL ALEPH teams, away on 16 July. Horst was universally trusted and of CERN. Horst was later awarded the Order of In the 1980s John led the RAL group into the and saw John become instrumental in guiding His friends and colleagues. his advice was sought regularly by colleagues. He Merit (First Class) of the German Republic. knew his way around CERN like no one else, and In 2000 Horst helped launch the CERN tech- M a x Zolotorev 1941–2020 knew whom to contact to get things done (and, nology transfer division and chaired the tech- crucially, how to get them to do it). Before becom- nology advisory board. Also, thanks largely to ing a physicist, Horst had considered becoming his drive, the 2017 book Technology Meets Research Curiosity, creativity and rigour a diplomat. Somehow, he managed to combine – 60 Years of CERN Technology: Selected Highlights the two professions, all in the interest of CERN. was published. Horst retired from CERN in 2003, Max Samuilovich Zolotorev, a pioneer of experi- ences. In 1989 Max emigrated to the US and took He cultivated the art of connecting scientists, but continued to make major contributions. He mental studies of atomic parity violation, passed up a research position at SLAC, later moving to F Izrailev engineers and administrators – always with the was asked to provide guidance for the FAIR project away on 1 April in his home in Oregon, US. Lawrence Berkeley National Laboratory, where aim of achieving a clear goal. at GSI Darmstadt, where he was instrumental in Max was born in Petrovsk, a small town not he worked until his retirement in 2018. At SLAC, Born in Wilhelmshaven, Germany in 1938, the arranging the involvement of CERN accelerator far from the Russian city of Saratov, where his Max and colleagues proposed using lasers to cool t h i r d c h i l d o f a n a v a l o ffic e r, Hor s t e a r n e d h i s P hD Horst at his retirement party at CERN in 2003. experts and later steered the complex and delicate mother found herself evacuated from the advanc- hadrons in colliders as a variation on van der in nuclear physics from Heidelberg University in organisation of major international “in-kind” ing German army. Upon graduating from second- Meer’s stochastic cooling method. The “optical 1966. Two years later he joined CERN to partici- t h e d e t e c t or s h a d t o b e fi n a n c e d, d e v e l o p e d a nd contributions. When, in 2019 the EU approved the ary school, despite showing unusual talent and stochastic cooling” concept will soon be tested pate in the Big European Bubble Chamber (BEBC). provided by outside groups with central CERN “South-East European International Institute for ability from an early age, he was not admitted to at Fermilab by a group led by a former student From the outset Horst was inspired by CERN. Early coordination. In 1990 he became leader of the Sustainable Technologies” (SEEIIST), Horst was an institute or even a vocational school because he of Max’s. Another of his co-inventions is the on he saw the importance of the Laboratory for accelerator technologies division, and in 1993 he a p p oi nt e d t o c o or d i n a t e t h e pr oj e c t’s fi r s t p h a s e. was Jewish. After eventually securing a position so-called “slicing method” to produce ultra- establishing peaceful worldwide collaboration was appointed LHC deputy project leader, where Horst left his mark on CERN. The wider com- with the Novosibirsk Electro Technical Institute short pulses of X-rays essential for time-resolved and relished participating in the adventure. his profound knowledge of CERN was vital for m u n it y a l s o b e n e fit e d i m m e n s e l y f r o m h i s con- in Siberia, where he demonstrated outstanding studies of the properties of condensed matter. He was soon identified as a leader, first as the reassessment of the LHC project. tributions in advisory roles throughout his active academic performance, he was able to transfer to Max Zolotorev was an inspiring mentor and physics coordinator for the BEBC in 1974. In 1980 Horst’s five-year term as CERN research and life. We have lost an outstanding colleague and a the newly founded Novosibirsk State University. Max Zolotorev was an inspiring mentor and teacher. teacher who always set the highest expectations he went to DESY to work on electron–positron technical director began in 1994 – the year LHC good friend from whose enthusiasm, advice and He graduated in 1966, before obtaining his first for h i s s t u d e nt s. H i s a bi l it y t o fi n d “ w e a k s p o t s” c ol l i d e r p h y s i c s i n pr e p a r a t i o n for L E P, r e t u r n i n g approval was expected. The day before the crucial w isdom we al l benefited t remendously. and second doctoral degrees in 1974 and 1979 at neutral weak currents, there was no evidence in one’s scientific logic was legendary. One of to CERN in 1982 to lead the BEBC group. In 1984 vote by the CERN Council in December of that the Institute of Nuclear Physics in Novosibirsk that the neutral weak current violated parity Max’s great insights was that, as physicists, we he became head of the experimental facilities year, the German delegation was still not author- His friends and colleagues. Academgorodok. as predicted by the Glashow–Weinberg–Salam should never design our experiments around division, providing support for Omega, UA1 and ised to vote in support of the project. In a late- (Editor’s note: Horst was much appreciated as a Max started out by working on measurements (G W S) m o d e l. F u r t h e r m or e, e a rl i e r a t o m i c p a r it y what was sitting in our labs or in our heads. UA2. For the R&D and construction of the LEP night action Horst managed to arrange contact source of wisdom and good humoured advice for o f t h e h y p e r o n m a g n e t i c m o m e nt s. Ho w e v e r, i n violation experiments had produced null results, Instead, we should choose deep and important detectors Horst needed to implement a new style with the office of the German chancellor, with the the editors of CERN Courier, past and present, and the early 1970s he was drawn into studying fun- in contradiction with theoretical predictions. problems, think hard about them and develop of collaboration: for the first time, major parts of mission to sway the minister responsible for the as a former member of the advisory board.) damental physics using the methods of atomic, The observation of parity violation in bismuth, the cleverest way to approach them that we can, molecular and optical physics. Together with his followed later by measurements of parity vio- learn new subjects, build new apparatus, and JoHn tHompson 1939–2020 m e nt or a n d c ol l e a g u e L e v B a r k o v, h e w a s t h e fi r s t lating electron scattering at SLAC, was crucial push our boundaries and limits. Max’s work to discover parity violation in by observ- evidence that the GWS model was indeed the e x e m pl i fie d t h e c u r i o s it y, c r e a t i v it y a n d r igour ing optical rotation of the plane of polarisation correct description of the weak interaction. of physics at its best. A first rate, hands-on physicist of light propagating through a bismuth vapour. Max and his colleagues also established the The 1978 measurement came at a crucial time foundation for some of today’s most sensitive Derek F Jackson Kimball, Dmitry Budker, John Thompson, a senior physicist at the UK’s photograph Family documented by the Particle Data Group. i n t h e d e v e l o p m e nt o f t h e St a n d a rd M o d e l. W h i l e magnetometers with their measurements in the Valeriy V Yashchuk, his friends and Rutherford Appleton Laboratory (RAL), passed John was central to the formation of Dares- observations of high-energy neutrino scattering late 1980s of nonlinear Faraday rotation, clearly colleagues (based on an article previously away on 20 August. bury’s LAMP group, which focused on a series on nuclei at CERN in 1973 provided evidence of identifying the crucial role of quantum coher- published in Physics Today). John obtained his PhD in nuclear physics for of hadronic photoproduction experiments. He work on the Van de Graaff accelerator at the played a leading role in the development of the DaviD NewtoN 1937–2020 University of Liverpool in the early 1960s before 480-element lead–glass array for studies of neu- David Newton was also an excellent teacher. moving to the University of Manitoba, Canada t r a l p a r t ic le pro duc t ion i n t he fi n a l p h a s e o f t he Focusing to work on particle physics. He then took a post L A MP e x periment. physics, he then took a position at Lawrence

at Daresbury Laboratory in the UK to work on D u r i n g t h i s p e r i o d, fol l o w i n g t h e d i s c o v e r y o f Family photograph Berkeley National Laboratory in the US, returning experiments using the 5 GeV electron syn- d e e p i n e l a s t ic s c a t t e r i n g a t SL AC a n d DE S Y, Jo h n on photons to the UK in 1968 as a lecturer in physics at the chrotron, NINA. His first experiment involved together with his colleagues became involved recently formed particle-physics group at Lan- a measurement of the total hadron photoproduc- in the plans to study deep inelastic scattering at David Newton was educated at Manchester c a s t e r Un i v e r s it y. He q u ic k l y b e c a m e i nt e r e s t e d tion cross sections for energies from 1 to 4 G eV. the higher energies afforded by the Super Proton Grammar School, UK, and after National Service in high-energy photon interactions, initially car- These precise measurements have never been John Thompson played a prominent role in ALEPH, Synchrotron (SPS) at CERN. He became a founding became a student at the University of Oxford. rying out experiments at Daresbury Laboratory. s s superseded and remain the definitive values among other experiments. member of the European Muon Collaboration Following his postgraduate studies in particle With the development of the SPS accelerator

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PEOPLE OBITUARIES PEOPLE OBITUARIES

at CERN he initiated a programme of research to generating a happy and productive atmosphere, thought was his main strength, and his ability EugènE CrEmmEr 1942–2019 extend these studies to much higher energies. a n d s p e nt s e v e r a l y e a r s a t C E R N w or k i n g o n t h e to see a simple solution if it was available was ENS gravity and 4D N = 8 supergravity made the 11th He was involved in the design of the electron project. He then joined the H1 collaboration at most admirable. He truly enjoyed understanding A modest and d i m e n s i o n u n e s c a p a bl e a n d e x h i bit e d e x c e p t i o n a l beam at CERN that was needed to produce the DESY, where he made a reputation for very precise physics and was happy to discuss whatever phys- (now widely used) duality symmetries. For these photons. Their interactions with protons in a measurements – in particular of the magnet- ics problem was brought to him. He loved the original thinker works, Eugène received the CNRS silver medal in hydrogen target were studied using the Omega ic-field distributions in the H1 magnet, per- countryside, especially walking with his wife, 1983. Some 15 years later, duality symmetries were spectrometer. A large international collabora- formed by him with the help of others. Jennifer, who was an expert botanist. The world e x tended to higher deg ree for ms. tion was formed to further these studies, which David will be remembered as an excellent is a poorer place with the loss of David Newton. Theorist Eugène Cremmer, who passed away in The successes of Eugène’s work led to many included several members of the Lancaster group. teacher who continued to help young people up October 2019, left his mark in superstring and invitations abroad. Though he chose to remain David became spokesperson of this collaboration, until a few months before his death. Clarity of Terry Sloan Lancaster University. supergravity theory. He will be remembered in France, he maintained collaborations and across the world as a brilliant colleague, as orig- activities at a high level. He was director of the PhiliPPe Mer Mod 1978–2020 inal as he was likeable. ENS theoretical-physics laboratory in 2002–2005. Born in Paris in 1942, his parents ran a book- Eugène was as regular as clockwork, arriv- store. The neighbourhood children were firmly Cremmer had an important role in 11D supergravity. ing and leaving the lab at the same time every An intense career cut short oriented towards vocational schools and Eugène day – the only exception I witnessed was due was trained in woodworking. He was eventually group of pilgrims from the theoretical-physics to ’s work addiction, Philippe Mermod, a member of the ATLAS and participated in the proposed SHiP experiment. spotted by a mathematics teacher, obtained a group at Orsay. He worked with Jean-Loup Ger- w h i c h h e e nj o y a bl y i n fl i c t e d u p o n u s for a w h i l e.At SHiP collaborations at CERN, passed away on M or e o v e r, h e r e c e nt l y m a d e s i g n i fic a nt c o nt ri- technical Baccalauréat degree and then pursued v a is on st r i ng field t heor y a nd later col labor ated 12:18 p.m. Eugène would always gather all avail- P Mermod 20 August. butions to the design and construction of the mathematics at École Normale Supérieure (ENS) with Scherk, the author, and several visitors on able colleagues to go to lunch, and this led Guido Born in Geneva in 1978, Philippe obtained time-of-flight detector for the near-detector in Paris in 1962. In 1968–1969, following a trig- supersymmetry, supergravity and applications to Altarelli to observe “Were Eugène to disappear his Master’s degree in 2002 from the University upgrade of the T2K collaboration in Japan; this gering of research into dual models by Daniele . His revolutionary 1976 paper with the whole lab would starve to death!” Eugène of Geneva and his PhD in 2006 from Uppsala is the first modern neutrino detector applying Amati and Martinus Veltman, Eugène began to Scherk introduced the linking number of a cyclic kept his papers in an encrypted pre-computer University in Sweden. He joined ATLAS in 2007, this technology. compute higher loop diagrams in a remarkable dimension by a closed string. This would turn out order, and nobody could understand how he was affiliated first with Stockholm University and Philippe was an intense scientist, curious to s e r i e s o f t e c h n i c a l l y i m pr e s s i v e p a p e r s. T h e fi r s t to be crucial for heterotic string models, T duality able to extract any needed reference in no time, then with the University of Oxford and, in 2011, explore new paths, who devoted his attention one was written with André Neveu, and others and mirror symmetry, for the so-called Scherk– always remembering most of the content. He cul- rejoined the University of Geneva as a research a n d e ffor t s t o f u n d a m e nt a l p h e n o m e n a a n dwho with Joël Scherk in 1971–1972 while a postdoc S c h w a r z c o m p a c t i fic a t i o n, a n d w a s s o o n a p pl i e d t o tivated his inner energy by walking quickly while associate, becoming assistant professor in 2014. sought the answer to questions rather than per- at CERN. At that time, CERN was an important . The 1977 proposal with Scherk of sponta- absorbed in thought. We have lost a role model Philippe made several contributions to ATLAS. sonal promotion. He was also an active citizen, cradle of string theory, with groups from different neous compactification of the six extra dimensions and a modest, full-time physicist. Among them, he pioneered the search for dis- conscious of the need for fairness and sustaina- countries forming a critical mass. of space remains central in modern string theory. placed heavy neutral leptons and led the effort Philippe was always curious to explore new paths. bility if humanity was to have a future, whether In late 1974 Eugène returned to ENS with a small In 1978–1979 his pioneering papers on 11D super- Bernard Julia École Normale Supérieure. on the search for highly ionising particles in Run he would see it himself or, alas, not. We will miss 2. He also made important contributions to the performed using various techniques in ATLAS, his energy, ideas and vision. trigger system. Philippe’s preferred topic was MoEDAL and other experiments. the search for magnetic monopoles, which he Always looking for more science, he also His colleagues and friends.

ronald Fortune 1929–2019 At CERN from its beginnings

Experimental physicist Ronald Fortune, who coordinated a large CERN–Berkeley–Ruther- CERN Courier readers save 30% joined CERN’s first nuclear research group in ford team in the extensive study of accelerator January 1956, passed away on 16 June 2019 at M Fortune shielding problems. The final phase of his career the age of 90. at CERN was spent in organising the large-scale Great news for readers of CERN Courier, you can now purchase books directly Ron graduated with a degree in physics and production of particle detectors (wire chambers) from IOP Publishing’s new bookstore and save 30% across the store. mathematics from the University of Aberdeen, for the nuclear-physics divisions. UK, before joining electrical engineering firm In 1973 Ron resigned his staff position at CERN Use the code CERN30 at checkout to claim your discount. This offer is valid AEI in Manchester, where he acquired valuable to direct an independent consultancy in phys- practical training in several departments and ics, engineering-physics and project manage- through 2020. research experience in high-voltage techniques ment. In 1976 the firm signed a contract with and electron-microscope design. This training the Dutch government, where he was charged was put to immediate use in his first post as with the construction of a five-metre supercon- store.ioppublishing.org scientific officer in the British Royal Naval Sci- ducting solenoid for the muon channel of the entific Service, where he developed automated National Institute for Nuclear Physics Research instrumentation for the study of atomic-weapon in Amsterdam, which was successfully brought explosions at the Woomera test range in Australia. Ron Fortune joined CERN just over a year after it into operation in 1981. Ron’s main career was as a senior scientist had been established. In later years Ron actively collaborated in at CERN, where he spent 17 years engaged in neuroscience research carried out at the Geneva a wide variety of projects. This included six equipment for the photography of high-energy University Hospital, co-authoring several years in high-energy physics research study- p a r t i c l e s. For h i s w or k o n r e l a t i v i s t i c i o n i s a t i o n, peer-reviewed articles in specialised journals. i n g K-m e s o n s, r e l a t i v i s t ic io n i s a t io n e ffe c t s a n d he was awarded a doctorate by the University Ron was a most charming person, always very hu nt i n g for q u a r k s, d u r i n g w h i c h R o n pi o n e e r e d of Geneva. The next eight years were spent in cheerful and positive with an extraordinary methods for identifying high-energy particles CERN’s applied-physics divisions, where he was sense of humour. by measurement of their momentum and ionis- a member of the team that developed the world’s ing power, and developed high-precision optical first radio-frequency particle separator. Ron also Helli Merica Fortune his wife and colleague.

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Notes and observations from the high-energy physics community

14 Cosmic plumber, fixed a leak for $100 million (4,9) End-of-year crossword 15 No wimps allowed in this noble medium – but maybe axions? (2) 16 Biological effectiveness is a factor for this absolute unit (2) Pit your wits against fellow CERN Courier readers and review the year 17 Status of baguette after LHC switched on (5) in particle physics with our inaugural cryptic crossword, compiled 19 Ser iously tense consta nt now m icrow aves look c losed not flat (6) 20 Simon says focus your neutrino beam with this (4) by associate editor Mark Rayner. The first correct entr y to reach 22 Jejune quark model, struggles when things get non-perturbative (5) [email protected] will win a mystery prize. 23 Elementary for spotting neutrinos, according to Yankee time projections (2) 1 2 3 4 5 6 7 25 NA62’s neutral sibling will first knock off trillions o’background (4) 26 Could symmetries actually emerge here, initially, and dissolve in the extreme ultraviolet? (2) 27 Island lab to ditch an ion for an electron by the end of the decade (10) 8 9 10 11 28 Ideal surname for academic preeminence – enough to drive colleagues to drink (2) 12 13 29 Presidential baryon that decays to a hyperon and a pion (2) 30 Initially, a European bid to triangulate gravitational waves (2) 14 32 Now dissolved in a super detector, will tag neutrons in a flash (10) 33 Lab with emissions equivalent to a cruise liner, says new report (4) 15 16 Down 1 Letters bestowed to avoid paying grad students (2) 17 18 2 Courier policy on paying contributors in order: in favour of a writer (9) 3 Seems just as rigid as Mg and Si, weirdly – thanks to 14 across we can 19 20 21 double check (2) 4 Planned sequel to Japanese smash hit, will face spicy competition from 22 Den is Vi l leneuve’s sc i-fi epic (5,10) 5 Figurative status of a Director-General with a fresh mandate (4,2,3,6) 23 24 25 6 Once again the world’s most luminous lab – the belle of the ball, you might say (3) 26 27 7 Bye-bye for now to Homi Bhabha’s institute (4) 8 Tetraquark interpretation going out of fashion given hidden beauty of 28 29 recent observation? (9) 11 Se x y first spot ted in 1898 (4) 30 31 12 Program that can be read and changed in any order, before folk and ja z z influences (3) 32 17 Number of large-hadron years celebrated in 2020 – not counting the false start (3) 33 18 A middle way does exist, at least in condensed matter, whatever Bose and Fermi say (5) 21 Supercool substance central to success at 26 down and 33 across (7) Across 24 Functionally, its product with 10 across can be a matrix or plain old number (3) 1 Amount of data collected so far at the LHC (4,2,3,6) 25 Initially 1/2 |dφ/dt|2, for example (2) 8 Robert, François and Peter seem to have predicted this coupling correctly too (4) 26 Latin journey to Gallic fusion (4) 9 Control and monitoring software beloved of DAQ experts like Gilgamesh (5) 27 Beloved elephant, now getting on a bit, maintains he saw too many 10 Parenthetical quantum state (3) tau leptons (5) 13 Unstable academic position discovered by the Curies (2) 31 Sola r c yc le first obser ved by Bore x ino t h is yea r (3)

From the archive: November 1980

Tunnel vision felt important to gain knowledge expected to run with increased On 18 September 1980 the CERN of the sub-Jura conditions before luminosity until around 2038. Finance Committee approved a launching the project. And then? On 19 June the CERN contract with a Franco–Swiss  Based on CERN Courier Council approved an update to the

consortium for a tunnel under CERN-PHOTO-8107558 November 1980 p345. European strategy for particle the Jura mountains, where it physics, recommending further is planned to build the large Compiler’s note studies towards a huge 100 km Future electron–positron storage ring, The LEP tunnel, Europe’s largest Circular Collider at CERN. If built, the LEP. Ten kilometres of LEP’s 30 km civil-engineering project prior to the FCC will be a dream project for tunnel circumference would pass under Channel Tunnel, will serve the engineers. The region around CERN the Jura and, though the probable Drilling a borehole along the physics community well for half a will confront them with almost every tunnelling conditions around the proposed line of the LEP tunnel in century. It housed LEP from 1989 known subterranean challenge, going rest of the ring are known from 1981 to reveal conditions likely to be until 2000, when it was recycled to where no tunnel has gone before SPS construction experience, it is encountered during excavation. accommodate the LHC, which is (CERN Courier Sep/Oct 2019 p26).

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The DT1081A and N1081A are innovative laboratory tools that incorporate in a single module the most common functionalities that you need to implement the logic capabilities of your experiment. Wide range of user-selectable functionalities:

COUNTERS/TIMERS DIGITAL PULSE GENERATOR TIME STAMPING LOGIC GATES

• Touch screen and Web interface for easy programming and optimal user-experience • User-friendly widgets to configure each section, monitor real-time output data and access the online help • Ethernet (1 Gbps) and USB2.0 connectivity

Small details… Great differences A new CAEN Tool in your Laboratory!

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