CERNSeptember/October 2020 cerncourier.com COURIERReporting on international high-energy physics WLCOMEE CERN Courier – digital edition Welcome to the digital edition of the September/October 2020 issue of CERN Courier. NUCLEAR PHYSICS This issue’s cover feature (p36) describes recent results from CERN’s ISOLDE facility, where researchers are probing the extremities of the nuclear landscape to complete AT THE our understanding of the nuclear interaction. Advanced laser and trapping techniques developed over many years at ISOLDE are also bringing new ways to test physics EDGE beyond the Standard Model.

This autumn CERN launches its quantum technology initiative (p47) – part of a fast-growing interdisciplinary effort taking place worldwide to develop quantum computing, communication, sensing and other devices that promise to underpin a “second quantum revolution” (p49).

Sticking with CERN science, we report on new tetraquark discoveries by LHCb (p25), NA62’s evidence for an ultra-rare kaon decay (p9), the first signs of Higgs– muon coupling (p7), and how the Higgs boson has so far delivered three fundamental discoveries (p41). Also, don’t miss our special feature on careers from the CERN Alumni Network (p56).

Elsewhere in this issue: the European Spallation Source nears completion (p29); neutrinos prove rare solar-fusion process (p11); how particles attract Nobel prizes (p70); reports from ICHEP and Neutrino 2020 (p19); news in brief (p13); reviews (p53), and more.

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EDITOR: MATTHEW CHALMERS, CERN   DIGITAL EDITION CREATED BY IOP PUBLISHING High-energy careers One Higgs, three discoveries CERN and quantum technologies

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Tetraquarks Recent LHCb observations On target The European Spallation Source Quantum future Alberto Di Meglio on reignite the meson-diquark debate. 25 nears completion. 29 CERN’s quantum technology initiative. 47

NeWS people

ANALYSIS ENERGY FRONTIERS FIELD NOTES CAREERS OBITUARIES Higgs-muon coupling The LHC as a photon ICHEP a virtual success Growing the high- Ulrich Becker 1938–2020 The x740 is a CAEN Waveform Digitizers family able to perform basic waveform • XENON1T excess colldier • The exotic • Neutrino 2020 zooms energy network • Claude Détraz 1938– • Signs of ultra-rare nature of X(3872) into virtual reality CERN alumni 2020 • John Flanagan recording and run real-time advanced Digital Pulse Processing (DPP) kaon decay • CERN’s • J/ψ polarisation in • Terascale summer demonstrate the value 1964–2020 • Henri impact on the UK lead collisions school goes global. 19 placed by employers on Laporte 1928–2020 • Estonia joins CERN • LHCb’s search for the skills acquired in high- • George Trilling CHECK THIS OUT! • CNO process detected. 7 dark photon. 15 energy physics. 56 1930–2020. 65 V/VX2740 - 64 Channel 16 bit 125 MS/s Digitizer 1GbE or 10GbE • 64 channel, 125 MS/s, 16 bit waveform digitizer FeAtureS • Four 40 pin, 2 mm header connectors CMS-PHO-EVENTS-2019-002-7 • Adapters to 1.27 mm flat cables or coax MULTI-QUARK STATES NEUTRON SCIENCE EXOTIC NUCLIDES HIGGS BOSON • Differential or SE inputs Tetraquarks back ESS under Exploring nuclei One Higgs, in the spotlight construction at the limits three discoveries 1 DAC output (signal • 1GbE or 10GbE or CONET2 (optional) The debate over whether The European Spallation Recent studies of exotic ATLAS and CMS have inspection or trigger sum) • USB 3.0 type C tetraquarks are loosely Source will provide nuclides at ISOLDE made three distinct • Common Trigger (waveforms) or Individual Self-trigger modes bound pairs of mesons new research into offer new ways to look discoveries regarding • DPP options: PHA, QDC, PSD, CFD or tightly bound pairs of material properties and for physics beyond the the Higgs, argues • Advanced Waveform Readout modes: ZLE, DAW diquarks. 25 fundamental physics. 29 Standard Model. 36 Yosef Nir. 41 Open • Open FPGA FPGA • 4 LEMOs + 16 LVDS programmable I/Os • 1 DAC output (1ch 125MS/s 14bit) opINIoN DepArtmeNtS • Independent 5MS/ch of max. Record Length • Available in desktop form factor VIEWPOINT INTERVIEW REVIEWS FROM THE EDITOR 5 CERN and quantum Lessons in An intuitive NEWS DIGEST 13

Four 40pin, 2mm FIRMWARE SOFTWARE technologies leadership approach to teaching APPOINTMENTS 60 header connectors CERN’s new quantum The best leaders are New textbook by Common Trigger (waveforms) or & AWARDS technology initiative those who don’t want to Larkoski • Accelerator G Audi/W Huang/AMDC-NUCLEUS Individual Self-trigger modes & WAVE RECRUITMENT 61 DUMP can enrich its research be leaders per se, says radiation protection. 53 On the cover: The nuclear CAEN programme, says experimentalist landscape, showing mass BACKGROUND 70 Alberto Di Meglio. 47 Ian Shipsey. 49 excess (vertical) versus Z, N C and LabVIEW™libraries available for custom developments. and decay mode (colour). 36

CERN COURIER SEPTEMBER/OCTOBER 2020 3 Small details… Great differences

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ISOLDE: shaping the nuclear landscape AMDC-NUCLEUS (G Audi, W Huang, D Lunney) (G W Huang, Audi, AMDC-NUCLEUS fter 100 years of expanding and exploring the chart of the nuclides (cover image) physicists are still without A a complete understanding of nuclear interactions. An early picture of the nucleus was of an incompressible liquid drop. Systematic surveys of the nuclear chart later revealed that protons and neutrons arrange themselves in quantum orbits or shells, with certain “magic” numbers of nucleons Matthew resulting in greater stability. Reconciling the drop and shell Chalmers models has been a longstanding quest, but a lack of predictive Editor power has required further exploration of the nuclear chart to reveal clues. By continuing to innovate in the production and purification of the most exotic species, CERN’s ISOLDE facility leads the charge in probing the extremities of the nuclear landscape (see p36). Understanding nuclear structure relies on measurements of the mass and radii of nuclei, made possible by precision Onwards and outwards Nuclear mass excess versus proton and laser and trapping techniques developed at ISOLDE over many neutron number. Colours show decay mode (stable nuclides in black). years, which have been adopted by facilities worldwide. The farther experimenters venture from the valley of stability, Quantum future the more surprises they find – the most dramatic being the This autumn, CERN launches its quantum technology initiative erosion of the stabilising magic of closed nuclear shells, which (p47). New quantum computing, communication and sensing gives way to nuclei in contorted dis-equilibrium. devices that harness properties such as entanglement promise ISOLDE’s ability to produce the most exotic nuclides is also to underpin a “second quantum revolution”, following the stimulating developments in theory, in particular ab-initio information and communication technology that resulted techniques, derived using chiral effective field theory that from the birth of quantum mechanics in the 20th century. respects the symmetries of QCD. Recently, precision laser and Several major national programmes are already under way, mass spectroscopy have brought radioactive molecules within with the US recently announcing more than $500M for five its grasp – offering a new way to detect possible electric dipole quantum-science institutes at its national laboratories (p13). moments that would point to new physics. In its sixth decade, Though relatively new to the game, CERN has significant expe- ISOLDE continues to innovate and evolve. rience in many of the relevant domains and provides valuable CERN’s science is a strong theme of this issue, with recent use-cases, particularly in quantum computing. results from LHCb reinvigorating the tetraquark debate (p25), As our interview (p49) explores, it is too early to tell how NA62 establishing evidence for an ultra-rare kaon decay (p9), quantum technologies will impact society – just as nobody and the LHC experiments reporting the first indications of in the 1950s could have predicted that billions of transistors CERN’s couplings of the Higgs boson to a second-generation fermion would be packed into our pockets today. But it is clear that science is a (p7 and p41). Our special feature on the CERN Alumni Network high-energy physics stands to benefit from new computing, strong theme (p56), meanwhile, highlights the high value placed by employ- sensing and other quantum-technology applications, and of this issue ers on skills gained from training in high-energy physics. that labs like CERN have the potential to make a real impact.

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, Switzerland; with CERN, and to Mark Rayner Brookhaven National JINR Dubna B Starchenko SNOLAB Samantha Kuula Tom Houlden e-mail courrier- individual subscribers. Archive contributor Laboratory Achim Franz KEK National Laboratory TRIUMF Laboratory Recruitment sales adressage@cern.ch It is published six times Peggie Rimmer Cornell University Hajime Hikino Marcello Pavan Chris Thomas per year. The views Astrowatch contributor D G Cassel Lawrence Berkeley Advertisement Published by CERN, 1211 expressed are not Merlin Kole DESY Laboratory Laboratory Spencer Klein Produced for CERN by production Katie Graham Geneva 23, Switzerland necessarily those of the E-mail Till Mundzeck Los Alamos National Lab IOP Publishing Ltd Marketing and Tel +41 (0) 22 767 61 11 CERN management. [email protected] Enrico Fermi Centre Rajan Gupta Temple Circus, Temple circulation Laura Gillham Guido Piragino NCSL Ken Kingery Way, Bristol BS1 6HG, UK Printed by Warners Advisory board Fermilab Kurt Nikhef Robert Fleischer Tel +44 (0)117 929 7481 Advertising (Midlands) plc, Bourne, Peter Jenni Riesselmann Novosibirsk Institute Tel +44 (0)117 930 1026 Lincolnshire, UK Christine Sutton Forschungszentrum S Eidelman Head of Media Jo Allen (for UK/Europe display Claude Amsler Jülich Markus Buescher Orsay Laboratory Head of Media advertising) or © 2020 CERN Philippe Bloch GSI Darmstadt I Peter Anne-Marie Lutz Business Development +44 (0)117 930 1164 (for ISSN 0304-288X Roger Forty IHEP, Beijing Lijun Guo PSI Laboratory P-R Kettle Ed Jost recruitment advertising); 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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Your partner in Non Destructive NEWS Diagnostic Solutions ANALYSIS for Low Current Measurements

Higgs boson Turning the screw on H → μμ CMS-PHO-EVENTS-2020-017-1 CMS-PHO-EVENTS-2020-017-1 The first evidence for the coupling of the Higgs boson to a second-generation fermion, the muon, has been reported at the LHC. At the 40th International Conference on High Energy Physics, Turbo-ICT & BCM-RF held from 28 July to 6 August (see p19), CMS reported a 3σ excess of H → μμ decay candidates compared to the expected sample under the hypothesis Very low charge measurement of no coupling between the Higgs boson of ultra-short bunches and the muon. A similar analysis by the ATLAS collaboration yielded a 2σ excess for the coupling. The latest measurements of the Resolution down to 10 fC Higgs boson by ATLAS and CMS follow 5σ observations of its coupling to the tau lepton in 2015 and to the top and bottom quarks in 2018, all of which are third-generation fermions. Its couplings to W and Z bosons have also been estab- lished at 5σ confidence. Within present experimental accuracy, all couplings between the Higgs boson and other Standard Model particles correspond to the strength of interaction that would give the particles their observed masses, New topology ons observed at the LHC; vector-boson are compatible with the Standard Model,” CWCT & BCM-CW according to the Brout–Englert–Higgs A CMS candidate fusion; the production of a Higgs boson says ATLAS physics coordinator Klaus mechanism. In this model, the parti- for Higgs-boson in association with a weak vector boson; Mönig. “Assuming the H → μμ coupling cles acquire mass through spontane- production via and its production in association with predicted by the Standard Model, and ous symmetry breaking; the W and Z vector-boson a top quark–antiquark pair. Uniquely, extrapolating the current results, the Precise average current measurement of as a result of a local gauge symmetry fusion and its decay CMS simulated the background to the combined sensitivity could get near the and the fermions, such as the muon, into two muons vector-boson-fusion signal rather than observation threshold of 5σ at the end Continuous Wave beams or macropulses as a result of Yukawa couplings to the (red lines). fitting it from data – a procedure that of Run 3, from 2022 to 2024.” Higgs field – a novel type of interaction would have incurred additional statistical If there is only a single Higgs field, among fundamental particles that is not uncertainty – resulting in the topology it should provide the masses for all the Resolution down to 0.5 µA derived from a symmetry principle (see contributing roughly equal statistical Standard-Model particles, but there may p41). Any deviation from the expected power compared to gluon fusion. be additional Higgs fields that could make couplings would imply that the Higgs contributions to their masses. The new sector is more complicated than this Machine learning results therefore reduce the scope avail- minimal scenario. “The fi rst e v idence i n C M S w a s reac he d able to such multi-Higgs models, and Couplings to lighter particles are thanks to the excellent performance of sharpen the question of why there is a expected to be proportionately smaller our muon and tracking systems, and an hierarchy of particle masses, says John a n d m or e d i ffic u lt t o o b s e r v e. T h e d e cay improved signal/background discrim- Ellis of King’s College London. “Why is to two muons, H → μμ, is expected to ination with machine-learning tech- the Higgs coupling to the muon so dif- Visit www.bergoz.com occur with a branching fraction of just niques,” says Andrea Rizzi, CMS physics ferent from its coupling to the tau lepton, one in 5000 Higgs-boson decays, and is The new co-coordinator. whereas the couplings of the W boson to overwhelmed by backgrounds from the results The signature for the decay is a small tau leptons and muons are equal to within Drell–Yan process. sharpen the excess of events near a muon-pair a couple of percent? The more we learn The new ATLAS and CMS analyses, question of invariant mass of 125 GeV – the mass of about the Higgs, the more mysterious DISTRIBUTORS MANUFACTURER which deploy the entire 13 TeV Run-2 a Higgs boson. CMS reports an overall it seems!” why there is data set, include events where the Higgs signal strength of 1.2 ± 0.4, while ATLAS U.S.A.: GMW Associates India: GEEBEE International BERGOZ Instrumentation boson was produced according to four a hierarchy finds a signal strength of 1.2 ± 0.6, with Further reading www.gmw.com www.geebeeinternational.com www.bergoz.com topologies: gluon fusion, which accounts of particle the uncertainties dominated by their sta- ATLAS Collab. 2020 arXiv.org:2007.07830. [email protected] [email protected] 156 rue du Mont Rond for the creation of 87% of the Higgs bos- masses tistical component. “Both measurements CMS Collab. 2020 CMS-PAS-HIG-19-006. Espace Allondon Ouest Japan: Hayashi-Repic China: Beijing Conveyi Limited 01630 Saint Genis Pouilly, France www.h-repic.co.jp www.conveyi.com CERN COURIER SEPTEMBER/OCTOBER 2020 7 [email protected] [email protected] [email protected]

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Dark m atter R aRe decays Researchers grapple with XENON1T excess Double digits for ultra-rare kaon decay NA62 collaboration NA62 collaboration CERN’s NA62 collaboration has pre- run, and plans to improve its sensitivity 10–4 An intriguing low-energy excess w i l l fi n d it w it h i n t h e fi r s t h o u r s ofrun- sented its latest progress in the search for Camerini experimental upper limit @ 90% CL to less than 0.1 per billion by increasing of background events recorded by 120 ning,” says Garcia Irastorza. K+ → π +νν– – a “golden decay” with excep- the beam intensity and upgrading the 10–5 experimental measurement the XENON1T detector at Gran Sasso A second new-physics explanation tional sensitivity to physics beyond the theoretical prediction KOTO detectors. Klems National Laboratory in Italy has sparked 100 cited for XENON1T’s low-energy excess Standard Model (SM). The new analysis 10–6 As experimental uncertainties are XENON collaboration Cable a series of preprints speculating on its is an enhanced rate of solar neutrinos provides the strongest evidence yet for _ expected to approach the theoretical νν ) Asano underlying cause, ranging from unex- interacting in the detector. In the Stand- the existence of this ultra-rare process, + 10–7 precision in coming years, explains 80

→ π → E787 pected background sources to phenom- ard Model, neutrinos have a negligi- at 3.5σ sig n i fica nce. “A f ter se ver a l yea rs theo rist Andrzej Buras of the Institute + 10–8

ena beyond the Standard Model. On 17 keV) bly small magnetic moment, however, of a very challenging analysis, battling 10 for Advanced Study in Garching, Germany, .

BR(K E787 + + 0 60 –9 – and K – decays can probe June the XENON collaboration, which should they be Majorana rather than orders of magnitude of background over 10 + E949 K → π νν L → π νν

year NA62

searches for excess nuclear recoils in a . Dirac fermions, and identical to their the signal, we are proud to have achieved scales as high as a few hundred TeV – –10 one-tonne liquid-xenon time-projection 40 antiparticles, their magnetic moment the first statistically significant evidence 10 beyond the reach of most B-meson decays. chamber (TPC), reported an unexpected should be larger, and proportional to for a process that has great sensitivity to “K+ → π +νν– is most sensitive to hypothet- 10–11 excess of events at energies of a few keV. 20 background model their mass, though still not detectable. new physics,” says lead analyst Giuseppe 1960 1970 1980 1990 2000 2010 2020 ical Z′ gauge bosons, vector-like quark Though acknowledging that the excess New physics could, however, enhance the Ruggiero of Lancaster University, who models, supersymmetry and some lep- events/(tonne science run 1 data year of publication could be due to a difficult-to-constrain 0 magnetic moment further, leading to a presented the result on 5 August during toquark models,” he says. “LHCb studies + – tritium background, the collaboration 2 larger interaction cross section at low the International Conference on High- of KS → μ μ and Belle II studies of B → K(K*) says that solar axions and solar neu- σ energies and an excess of low-energy Energy Physics (see p19). Convergence eight orders of magnitude using parti- νν– will also have a part to play, allow- –2 trinos with a Majorana nature, both of elec t ron recoi ls. X ENON1T fit s i nd icate A flavour-changing, neutral-current Theoretical cle-identification techniques. ing a global analysis to test not only the which would signal physics beyond the that solar Majorana neutrinos with an process, K+ → π +νν– is highly suppressed predictions and The collaboration’s new result, which concept of minimal flavour violation, but 0 5 10 15 20 25 30 Standard Model, are credible explana- enhanced magnetic moment are also in the SM, with contributions from Z- experimental includes the full dataset collected until also probe new CP-violating phases and tions for the approximately 3σ effect. energy [keV] favoured over the background-only penguin and box diagrams with W, top measurements of 2018, adds a further 17 events to its previous right-handed currents.” hypothesis at the level of 3σ. quark and charm exchanges. It is also the K+ → π +νν– analysis, wherein three events observed Theorists expect to reach an accuracy World-leading limits Threshold events X ENON1T data from scientific run 1, very “clean” theoretically, since the branching fraction. in 2016 and 2017 yielded an estimated of 5% on the predicted K+ → π +ν branching +72 The XENON collaboration has been in from Februar y 2017 to Februar y 2018, show an excess of Flurry of activity low-energy hadronic matrix elements are branching fraction of 47 –47 decays per ratio towards the end of the decade. In the pursuit of WIMPs, a leading cold-dark- low-energy electronic recoils above the background model. The community has quickly chimed in just those of the quark currents between trillion. The measured branching fraction same period, the NA62 team is seeking +40 matter candidate, since 2005 with a with additional ideas, with more than the hadronic states. of 110 –35 per trillion is in agreement with to hone its resolution from the current programme of 10 kg, 100 kg and now If the XENON1T signal is 100 papers citing XENON1T’s findings NA62 observes the 6% of positively the SM prediction of 84 ± 10 per trillion. 30% down to 10%. The collaboration will 1 tonne liquid-xenon TPCs. Particles appearing on the arXiv preprint server charged kaons that are produced when The NA62 result is expected to soon resume data taking in 2021, following scattering in the liquid xenon create indeed an axion, IAXO will since the result was released. One pos- 450 GeV protons from the Super Proton be complemented by a measurement of upgrades to both beam and detector tak- 0 – both scintillation light and ionisation sibility is a heavy dark-matter particle Synchrotron strike a beryllium target. The the related CP-violating KL → π νν decay ing place during the ongoing second long electrons; the latter drift upwards in an find it w it hin t he first hours that annihilates or decays to a second, analysis is challenging because of the tiny by the KOTO collaboration at the J-PARC shutdown of CERN’s accelerator complex. electric field towards a gaseous phase much lighter, “boosted dark-matter” branching fraction and the presence of a research facility in Tokai, Japan. This “The horizon of a new-physics programme where electroluminescence amplifies of running particle that could scatter on electrons neutrino pair in the final state. Pioneering even rarer process has a predicted SM with a sensitivity to decay rates well below the charge signal into a light signal. via some new interaction, notes CERN the technique of observing kaon decays branching fraction of just 34 ± 6 per tril- the 10–11 level is now in sight,” says NA62 XENON1T derives its world-leading consistent with the XENON1T excess. theorist Joachim Kopp. Another class i n fl i g ht, t he c ol l a b or at ion me a s u re s t he lion. KOTO’s 2015 data yielded no event spokesperson Cristina Lazzeroni of the limit on WIMPs – the strictest 90% According to this hypothesis, the axions of dark-matter model that has been kinematics of both the initial kaon and the candidates and a 90% confidence upper University of Birmingham, UK. confidence limit being a cross-section would be detected via the “axioelec- proposed, he says, is “inelastic dark final-state pion to isolate the kinematic limit on the branching fraction of 3.0 of 4.1 × 10–47 cm2 for WIMPs with a mass tric” effect, an axion analogue of the matter”, where dark-matter parti- signature of K+ → π +νν–, before then sup- per billion, but the collaboration is now Further reading of 30 GeV – from the very low rate of photoelectric effect. Though a good fit cles down-scatter in the detector into pressing other decay modes by a further fi n a l i si n g it s re s u lt s f rom t he 2016–2018 NA62 Collab. 2020 arXiv:2007.08218. nuclear recoils observed by XENON1T phenomenologically, and like tritium another dark-matter state just a few keV from February 2017 to February 2018. favoured over the background-only below the original one, with the liber- Policy HV Wooding A surprise was in store, however, in hypothesis at approximately 3σ, the ated energy then seen in the detector. the same data set, which also revealed solar-axion explanation is disfavoured “An explanation I like a lot is in terms UK report shows 285 electronic recoils at the lower end of by astrophysical constraints. For exam- of dark photons,” he says. XENON1T’s energy acceptance, from 1 to ple, it would lead to a significant extra The XENON collaboration is soon to impact of CERN 7 keV, over the expected background of energy loss in stars. start taking data with a new detector, 232 ± 15. The sole background-modelling Axion helioscopes such as the CERN XENONnT. With three times the fidu- membership explanation for the excess that the col- Axion Solar Telescope (CAST) experi- cial volume of XENON1T and a factor laboration has not been able to rule out ment will help in testing the hypoth- six reduction in backgrounds, explains T h e b e n e fit s o f C E R N m e m b e r s h i p g o wel is a minute concentration of tritium in esis. “It is not impossible to have an XENON spokesperson Elena Aprile b e y o n d s c i e n c e a n d t e c h n ol o g y, c o n fi r m s the liquid xenon. Though cryogenic dis- axion model that shows up in XENON of Columbia University in New York, a study commissioned by the UK’s Science tillation plus running the liquid xenon but not in CAST, but CAST already con- XENONnT should be able to verify or and Technology Facilities Council (STFC). through a getter is expected to remove strains part of the axion interpretation refute the signal within a few months of The report “Evaluation of the benefits any tritium below the level that would be of the XENON signal,” says CAST deputy data taking. “I am especially intrigued that the UK has derived from CERN”, pub- relevant, there is not yet any instrument spokesperson Igor Garcia Irastorza of the by the possibility to detect axions pro- l i s h e d o n 6 A u g u s t, fi n d s t h a t a r o u n d 500 sensitive enough to directly detect such University of Zaragoza. Its successor, the duced in the Sun,” she says. “Who needs U K fi r m s h a v e b e n e fit t e d f r o m s u p pl ying a trace amount, says the collaboration. International Axion Observatory (IAXO), the WIMP if we can have the axion?” goods and services to CERN during the One explanation proposed by the team which is set to begin data taking in 2024, past decade, bringing in £183.3M in rev- is solar axions, which, should they exist, will have improved sensitivity. “If the Further reading enue. An additional £33.4M was awarded Profit An electroplating plant at UK engineering firm HV Wooding, which is one of 500 UK companies to have s would be produced by the Sun at energies XENON1T signal is indeed an axion, IAXO E Aprile et al. 2020 arXiv.org:2006.09721. to UK firms for CERN experiments benefitted from supplying goods and services to CERN during the past decade.

8 CERN COURIER SEPTEMBER/OCTOBER 2020 CERN COURIER SEPTEMBER/OCTOBER 2020 9

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and from the CERN pension fund, while eight UK universities revealed that 95% B ei ng pa r t valued at more than £495M, before even AstrowAtch a further £1B in turnover and £110M in were attracted to study science because of one of considering the impact of the advances profit is estimated to have resulted from of activities in particle physics, with more the biggest that this research may underpin. Bibli- k n o c k- o n e ffe c t s for U K c o m p a n i e s a f ter than 50% saying they were inspired by ometric analyses also show that CERN Neutrinos confirm rare solar-fusion process working with CERN. the discovery of the Higgs boson. international research underpins many of the UK’s Over the same 10-year period, 1000 In terms of science diplomacy, the scientific most influent ial physics papers. Despite being our closest star, much collaboration Borexino or so individuals who have participated report acknowledges that CERN pro- collaborations The new report supports previous remains to be learned about the exact in CERN’s various employment schemes vides a platform for the UK to engage on the planet s t u d ie s i nt o t h e b e n e fit s o f C E R N me- nature of the Sun and how it produces have received training estimated to be more widely in global initiatives and places the UK bership. In particular, a recent study its energy. Two different fusion pro- worth more than £4.9M. The knowledge international networks, spilling over at t he f r ont ier of the impact of the High Luminosity cesses are thought to be at play in the and skills gained via working at CERN to favourable perceptions of its mem- LHC conducted by economists at the majority of stars: the direct fusion of are deployed across sectors including IT bers and greater engagement in science, of discovery University of Milan concluded that the hydrogen into helium, which is thought and software, engineering, manufactur- technology and beyond. “Fundamental science quantifiable return to society is well in to be responsible for approximately 99% ing, financial services and health, the research requires long-term engage- excess to the project’s costs (CERN Courier of the Sun’s energy; and the fusion of report notes, with young UK researchers ment; international collaboration makes September 2018 p51). hydrogen into helium via the six-stage who have engaged with CERN estimated t h i s e s s e nt i a l p o ol i n g o f e ffor t s p o s s i bl e, The UK is one of CERN’s founding carbon–nitrogen–oxygen (CNO) process to earn 12% more across their careers and the report provides a promising tes- members, and currently contributes (see CNO cycle diagram). Although theo- (corresponding to an extra £489M in timony for the future of CERN member- £144M per year to the CERN budget rised in the 1930s, direct proof of this additional wages in the past 10 years). ship,” said Charlotte Warakaulle, CERN (representing 16% of Member State sub- fusion process was missing. Now, the Each year an average of 12,000 school director of international relations. scriptions) via the STFC. “Being part of international Borexino collaboration students and other members of the pub- Carried out by consulting firm Tech- one of the biggest international scientific directly detected neutrinos produced in lic visit CERN in person; 220,000 visit nopolis, the study also quantified the collaborations on the planet places the UK the CNO cycle, providing the first direct CERN’s website; and 40,000 interact with scientific benefits of CERN membership. at the frontier of discovery science, which proof of this important fusion process. its social media. More than 1000 teachers Over the past decade, more than 20,000 in turn helps to inspire the next gener- The Borexino detector uses 278 tonnes have attended CERN’s national teacher scientific papers with a UK author have ation to study physics and other STEM of liquid scintillator held in a nylon programme in the past decade, who go on cited one of the 40,000 papers based subjects,” says STFC executive chair Mark balloon deep under the mountains at to teach an estimated 175,000 school stu- directly on CERN research published in Thomson. “This is of huge value to the Gran Sasso National Laboratory in Italy Solar focus Borexino’s 2200 photomultipliers detect scintillation light generated by electron/positron recoils dents within three months of their visit. the past 20 years. The report estimates UK – and for the first time this report to detect extremely rare interactions induced by sub-MeV neutrinos. A survey of 673 physics undergraduates in that the production of knowledge can be goes some way to quantify this.” between the scintillator and solar neu- trinos. In 2012 the experiment detected Commons/Borb Creative The spectral measurements performed CERN S Hertzog/CERN 4H neutrinos from the main solar fusion 1H of the CNO cycle exclude a non-detection process. Now, one year before the end of 1H with a statistical significance of more Estonia joins its scheduled operations, the Borexino γ than five sigma. The solar-neutrino +3.0 team has fully probed the solar energy interaction rate (7.2 –1.7 counts per day per CERN production. 100 t o n n e s o f t a r g e t, a t 68% c o n fid e n c e) 12 Despite minimising backgrounds from C furthermore agrees with models which 15 On 19 June the prime minister of Estonia, cosmic rays, trace amounts of radioactive N 13N predict that 1% of the energy produced Jüri Ratas, and CERN Director-General, nuclei that leak into the active volume in the Sun comes from the CNO process. Fabiola Gianotti, signed an agreement of Borexino produce a background of the ν e+ Additionally, the results shine light on admitting Estonia as an associate same magnitude as the sought-after the density of elements other than + member state in the pre-stage to mem- signal. The most important background e ν hydrogen and helium – the metallicity bership of CERN. The agreement will for the CNO analysis was 210Bi, a prod- – of the Sun’s core, which in recent years 15 13C enter into force once CERN has been uct of 210Pb of which trace amounts can O has been debated to potentially differ 14 informed by the Estonian authorities that diffuse into the scintillator from the N from that on the solar surface. The all the necessary approval processes have nylon balloon surface. Since the energy Borexino results indicate that the density been finalised. spectrum of the beta-decay of 210Bi is likely similar, although more precise γ γ “With Estonia becoming an associate resembles that induced by neutrinos 1H measurements with future detectors are member, Estonia and CERN will have the produced in the CNO process, the key to 1H required to confir m t his. opportunity to expand their collabora- detecting CNO neutrinos was to directly The groundbreaking Borexino study, tion in, and increase their mutual ben- Online firstEstonia’s prime minister Jüri Ratas and CERN Director-General Fabiola Gianotti at the signing measure the 210Bi-induced background. CNO cycle A proton is absorbed by a carbon nucleus, followed which required not only some of the efit from, scientific and technological ceremony which, due to the COVID-19 pandemic, took place via a live feed between Tallinn and Geneva – This was made possible by delving by a nuclear decay, then a second and third absorption of a proton, most precise techniques used in particle development as well as education and a first in CERN’s 66-year history. into the fluid dynamics of the liquid followed by another decay, the absorption of a fourth proton and physics but also complex fluid-dynam- training activities,” said CERN Direc- scintillator. finally a decay into a carbon nucleus, a helium nucleus and the ics simulations, provides a first probe tor-General Fabiola Gianotti. “We are the Compact Linear Collider project, “As an associate member, many The 210Bi in Borexino’s scintillator release of around 25 MeV of energy. into the processes at the cores of stars. looking forward to strengthening our a CMS team involved in data analysis important opportunities open up for produces 210Po, which undergoes alpha Although it has now been proved that t ies f ur t her.” and the Worldwide LHC Computing Estonian entrepreneurs, scientists and decay with a half-life of 134 days. As the the scintillator material by stabilising the CNO process is responsible for only After joining the CMS experiment in Grid, and another team taking part in researchers to work together on innova- alpha decay is relatively easy to identify, the temperature, both through insula- a fraction of the Sun’s energy, for heav- 1997, Estonia became an active member the TOTEM experiment. tion and R&D, which will greatly benefit the team used 210Po decays to deduce the tion and direct temperature regulation. ier and therefore hotter stars it is pre- of the CERN community. Between 2004 CERN’s associate member states are Estonia’s business sector and the econ- number of 210Bi decays in the detector. After the 210Po decay distribution inside dicted to be the dominant fusion process, and 2016 new collaboration frameworks entitled to participate in meetings of omy as a whole,” said Jüri Ratas, Estonia’s Ho w e v e r, a s t h e d i ffe r e nt i s o t o p e s m o ve the detector was found to be stable over making future high-precision studies gradually boosted scientific and tech- the CERN Council, Finance Committee prime minister, at the signing ceremony. around in the liquid it cannot be guar- times exceeding its half-life, an area important to understand the evolution nical co-operation. Today, Estonia is and Scientific Policy Committee. Their “Becoming an associate member is the anteed that the 210Bi distribution is equal with low 210Po activity was identified of the universe in general. represented by 25 scientists at CERN, nationals are eligible for staff positions next big step for Estonia to deepen its to 210Po unless the flow in the detector is and used to measure the CNO neutrinos comprising an active group of theo- and fellowships, and their industries are co-operation with CERN before becoming well understood. To overcome this, the with a well-understood and relatively Further reading rists, researchers involved in R&D for entitled to bid for CERN contracts. a full member.” collaboration had to reduce the flow of low background. Borexino Collab. 2020 arXiv:2006.15115.

10 CERN COURIER SEPTEMBER/OCTOBER 2020 CERN COURIER SEPTEMBER/OCTOBER 2020 11

CCSepOct20_NewsAnalysis_v4.indd 10 09/09/2020 11:05 CCSepOct20_NewsAnalysis_v4.indd 11 09/09/2020 11:06 CERNCOURIER www. V o l u m e 6 0 N u m b e r 5 S e p t e m b e r / O c t o b e r 2 0 2 0 CERNCOURIER.COM NEWS Books in High Energy Physics DIGEST Find your next read from over 800 high quality textbooks & research references Brilliant synchrotron begins and achieve an unprecedented Simplifying sums

www.tinyurl.com/wsparticlephys R Hahn Following a 20-month shutdown, precision of 21 ppt. The proton’s A team led by Pierpaolo Mastrolia the European Synchrotron mass discrepancy is the latest (Padova) and Sebastian Mizera Lectures on Quantum Field Lectures on Accelerator Physics Radiation Facility (ESRF), in in a series of oddities observed (Princeton) has published a new Theory (2nd Edition) By Alexander Wu Chao (SLAC National Accelerator Lab., USA) Grenoble, France, is back in in recent years, including the exposition of their 2017 idea for By Ashok Das (Univ. of Rochester, USA) Accelerators have been driving research and industrial advances action with users now able to converging proton-radius puzzle using techniques in algebraic for decades. This textbook illustrates the physical principles behind carry out experiments using a and the long-standing proton geometry to circumvent some Reviews of the First Edition: these incredible machines, often with intuitive pictures and simple Alex Romanenko (Fermilab) with a brand new fourth-generation spin crisis (CERN Courier May/June of the challenges relevant to “Ashok Das has written an excellent, mathematical models. The style is informal and accessible to qubit based on RF-cavity technology. high-energy synchrotron light 2019 p38). computing multi-loop Feynman comprehensive introduction to modern graduate-level students without prior knowledge in accelerators. source, the Extremely Brilliant amplitudes. The approach quantum field theory, covering both its US invests in quantum technology Source (EBS). The new machine Muon-collider study initiated uses “twisted cohomology”, theoretical underpinnings and basic com- 700pp Oct 2020 putational methods. It will be very useful to 978-981-122-796-7(pbk) US$88 / £75 Following a competitive will provide users across a wide A new international design a mathematical theory students, teachers, and researchers as a 978-981-122-673-1 US$188 / £165 peer-review process, the US range of disciplines with an study for a future muon collider previously only applied to string course text, and as a volume for self-study Department of Energy has funded X-ray brilliance and coherence began in July, following the theory, to tame the algebraic and reference.” Reviews of Accelerator Science and Technology new quantum-technology 100 times greater than ESRF’s recommendations of the 2020 complexity inherent to multi- Stephen L Adler, IAS, Princeton Volume 10: The Future of Accelerators centres at five national previous storage ring. It is update of the European strategy loop computations. Their new laboratories: Argonne, Berkeley, based on the hybrid multi-bend for particle physics (CERN Courier paper provides further evidence Edited by: Alexander W Chao (SLAC National Accelerator Lab., “This book is a comprehensive introduction to modern quan- Brookhaven, Fermilab and Oak achromat – with seven, July/August 2020 p7). Initiated by that the technique could be USA) & Weiren Chou (Fermi National Accelerator Lab., USA) tum field theory. The topics under consideration would be of Ridge. Each lab will receive a as opposed to two, bending the Large European Laboratory used in the future to perform great interest for every physicist and mathematician who are Beginning with a short article by Chen Ning Yang, this book contains $115 million investment over magnets per cell, reducing the Directors Group, which exists calculations for the LHC that are interested in methods of the quantum physics.” the more personal views, perspectives, and advices from frontier five years plus contributions horizontal emittance (CERN to maximise co-operation in out of the reach of conventional Zentralblatt MATH researchers on the future possibilities of accelerator research and from industrial partners. The Courier December 2018 p17). the planning, preparation and techniques (arXiv:2008.04823). development. 940pp Jul 2020 successful proposals include bids execution of future projects, the 978-981-122-216-0(pbk) US$98 / £85 352pp Sep 2019 to use accelerator technology in study will initially be hosted Laplace vindicated

978-981-122-086-9 US$198 / £175 978-981-120-959-8 US$158 / £140 quantum computing, by using KoelemeijJ at CERN, and carried out in Two centuries ago, Pierre-Simon New Books superconducting radio-frequency collaboration with international Laplace modelled t he effect of cavities to make niobium qubits. partners. Institutes can join t he Moon’s g rav it y on a t hin fluid Earlier this year, such Fermilab by expressing their intent to coating a smooth sphere, and cavities broke the world record collaborate via a Memorandum deduced that continent-sized for qubit coherence, achieving of Understanding. The goal of the pressure waves would periodically stability over a period of seconds study is to evaluate the feasibility sweep across the planet at (Phys. Rev. Applied 13 034032). of both the accelerator and its hundreds of kilometres per hour.

The five labs will also develop physics experiments (CERN Courier T Sakazaki quantum-sensor technology for May/June 2020 p41). CERN’s use in applications including The ion trap used to measure the Daniel Schulte has been appointed dark-matter searches. In June, proton-electron mass ratio. as interim project leader. CERN also launched a quantum- technology initiative (see p47). Proton slimmed down KEK reclaims luminosity record A new precision laser A new record for the highest by Albert Schwarz by Michel Rausch de Traubenberg edited by Swapan Chattopadhyay by S Y Lee edited by Carlos Pérez High-performance collaboration spectroscopy measurement of luminosity at a particle collider (University of California (Strasbourg Univ., CNRS Inst. (Northern Illinois Univ., USA), Gérard (Indiana University, de los Heros (Uppsala On 22 July, CERN and the Square the proton-electron mass ratio has been set by SuperKEKB at Resonant modes can be randomly at Davis, USA) Pluridisciplinaire Hubert Curien, Mourou (École Polytechnique, France), USA) University, Sweden) Kilometer Array (SKA) signed using trapped HD+ ions supports Japan’s KEK laboratory. On 15 June, excited in the atmosphere. France) & Mauricio Valenzuela Vladimir D Shiltsev (Fermi National an agreement to co-operate other recent indications that electron–positron collisions at (Centro de Estudios Científicos Accelerator Lab., USA) & Toshiki Tajima (CECs), Chile) (Univ. of California, Irvine, USA) with European networking the proton is less massive than the 3 km-circumference machine Takatoshi Sakazaki (Kyoto) and data-management previously thought (10.1126/ reached an instantaneous and Kevin Hamilton (Hawaii) AD LY 08 20 04 E International Journal of Modern Physics A (IJMPA) organisations GÉANT and PRACE science.aba0453). In the last few luminosity of 2.22 × 1034 cm–2 s–1 have now analysed 38 years of on the development of high- years, traditional Penning-trap — surpassing the LHC’s record atmospheric data to prove him Modern Physics Letters A (MPLA) performance computing in high- measurements (e.g. Phys. Rev. of 2.14 × 1034 cm–2 s–1 set with correct (J. Atmos. Sci. 2020 77 2519). Particles and Fields ∙ Gravitation ∙ Cosmology ∙ Astrophysics ∙ Nuclear Physics energy physics and astronomy. Lett. 119 033001) have weighed proton–proton collisions in Sakazaki and Hamilton observed Accelerator physics ∙ Quantum Information Analysing the data sets generated in at around 300 parts per 2018. SuperKEKB is an upgrade the ringing of randomly excited by the High-Luminosity LHC trillion (ppt) and three standard of the KEKB B-factory, which global-scale resonant modes • 35 years of publishing since 1986 at CERN and the SKA radio- deviations lighter than the held the luminosity record in precise accord with those telescopes planned for Australia previously accepted mass. The of 2.11 × 1034 cm−2 s−1 for almost hypothesised by Laplace. With • Approximately 600 papers published each year and South Africa will depend new measurement, obtained by 10 years until the LHC edged past periods as short as two hours, • Frequent special issues focusing on latest research upon “exascale” supercomputers, researchers in the Netherlands it. SuperKEKB’s new record was the new excitations complete developments capable of 1018 operations per and France, deployed a pair achieved thanks to a novel “nano- t he e x perimental pict ure first • Feature contributions (Review papers and Brief Reviews) second, which are expected to of narrowly detuned counter- beam” scheme that squeezes the hinted at by the observation of the by world’s leading physicists including Nobel Laureates emerge in the next few years propagating lasers to eliminate vertical height of the beams at the fundamental two-hemisphere (CERN Courier April 2018 p39). error due to the Doppler effect collision point to about 220 nm. mode in the 1980s. Visit our website to enjoy FREE access to selected papers: https://worldscientific.com/worldscinet/ijmpa https://worldscientific.com/worldscinet/mpla CERN COURIER SEPTEMBER/OCTOBER 2020 13

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Reports from the Large Hadron Collider experiments ATLAS The LHC as a photon collider

1200 data ATLAS preliminary γγ → WW –1 ATLAS preliminary data 2017 γγ → ττ √s = 13 TeV, 139 fb 1000 –1 qq → WW peμ > 30 GeV 60 √s = 13 TeV, 14.6 fb uncertainty other qq initiated T 800 non-prompt pp → p(γγ → μμ)p Drell–Yan total uncertainty mll ∉ [70, 105] GeV pp → p(γγ → ee)p 600 ee + μμ , 0.02 < ξ < 0.12 events 40 postfit pp → p(γγ → μμ)p* 400 pp → p(γγ → ee)p* combinatorial bkg. 200

events/0.0025 20

When Compromise is Not an Option. 1.4 1.2 1.0 0 High-Performance Digitizers for 0.8 –0.02 0 0.02 0.04 –0.02 0 0.02 0.04

data/pred. 0.6 A A C C ξAFP – ξll ξAFP – ξll 0 1 234 number of reconstructed tracks, n Big Physics Applications trk Fig. 2. A sample of γ γ → ℓℓ events can be isolated by observing a scattered proton in Fig. 1. To isolate a sample of γγ → WW interactions, events with the AFP spectrometer. Here, the proton energy loss measured in the AFP installed either Digitizers from Teledyne SP Devices utilize patented no additional reconstructed charged-particle tracks in the side (A and C) of the collision point (ξAFP, dimensionless) is shown to agree with that vicinity of the electron–muon pair (n = 0) are selected. predicted from measurements of the lepton pair in the main detector (ξ ). calibration technology, the latest data converters, and trk ℓℓ state-of-the-art FPGAs in order to achieve an unrivaled Protons accelerated by the LHC generate p a i r s – a r e t h e o n l y p a r t i c l e s d e t e c t e d i n side of the collision point, the AFP can a large flux of quasi-real high-energy the vicinity. However, if charged par- detec t protons t hat have been scat tered combination of high resolution and sampling rate. Their photons that can interact to produce ticles arise from nearby proton–proton in photon–photon collisions but which versatility makes them ideal for applications such as particles at the electroweak scale. Using collisions, the clean γγ → W W s i g n a l c a n have nevertheless been focused by the the LHC as a photon collider, the ATLAS be missed. The main background is W LHC’s magnets. Its pioneering results beam position monitoring, Thomson scattering plasma collaboration recently announced a set b o s o n p a i r s pr o d u c e d i n h e a d- o n pr o t o n– so far analyse a standard-candle pro- diagnostics, and more. o f l a n d m a r k r e s u l t s, a m o n g w h i c h i s t h e pr o t o n c ol l i s i o n s w h e r e p a r t i c l e s f r o m t h e c e s s w he re a prot on i s s c at t e re d i n p ho- first observation the photo-production breakup of the protons are not detected ton collisions that produce electron or of W-boson pairs. due to imperfect detector coverage or muon pa i rs (γγ → ℓℓ). For these signals, Supported features include: A s it pr o c e e d s v i a t r i l i n e a r a n d q u a r t i c reconstruction (figure 1). A total of 127 the measured proton energy loss is equal gauge-boson vertices involving two W background events are predicted com- to that predicted from the lepton pairs • Up to 10 GSPS sampling rate with 14 bits resolution b o s o n s a n d e it h e r o n e or t w o p h o t o n s, t h e pared to 307 events observed in data. This measured in the main ATLAS detector pr o d u c t i o n o f a p a i r o f W b o s o n s f r o m t w o signal excess corresponds to a statistical (fi g u r e 2). AT L A S r e p or t e d 180 e v e nt s w ith • Open FPGA for custom real-time signal processing photons (γγ → W W ) t e s t s a l o n g-s t a n d i n g significance of 8.4 standard deviations. a proton having matched kinematics to prediction of the Standard Model (SM). This establishes the existence of light the lepton pair with an expected back- • Multiple form factors including MTCA.4, PXIe, and PCIe This process is extremely rare but pre- t r a n s for m i n g i nt o p a r t i c l e s w it h w e a k- ground of about 20 events. This corre- dicted precisely by electroweak theory, s c a le m a ss e s – a re m a rk a ble a nd pre v i- sponds to a significance exceeding nine • Multi-channel synchronization capabilities such that any observed deviation would ously unobserved phenomenon. s t a n d a r d d e v i a t i o n s for b o t h l e p t o n fl a- • White Rabbit synchronization (MTCA.4 only) suggest that new physics is at play. The Precisely testing SM predictions of vours, establishing the presence of the mea surement re l ies on t he l a rge 139 fb–1 photon collisions requires accurate signal and the successful operation of • Peer-to-peer streaming to GPU (PCIe only) dataset of proton–proton collisions knowledge of the rate protons remain t h e A F P s p e c t r o m e t e r i n h i g h-lu m i n o s it y recorded by ATL AS in LHC Run 2. i nt a c t r e l a t i v e t o t h o s e t h a t br e a k a p a r t. Observing data. The detectors were sufficiently well • Application-specific firmware shortens design time Protons usually remain intact or are This is challenging to predict theoret- γγ → WW and u n d e r s t o o d t o m e a s u r e t h e c r o s s s e c t io n s excited into a higher energy state in ically and probing these rates unam- scattered of these processes. photon collisions, with the products of biguously requires directly detecting protons Observing γγ → WW and scattered any subsequent decay not reaching the the intact protons. The ATLAS Forward in γγ → ℓ ℓ protons in γγ → ℓℓ interactions are innermost components of the ATLAS Proton (AFP) spectrometer is becoming interactions long-awaited milestones in an emerg- detector. In these cases, the electron increasingly indispensable for this task. ing experimental programme studying and muon decaying from the W bosons A m o n g t h e n e w e s t a d d it i o n s t o t h e AT L A S are long- photon collisions. These complement – a n e vent top olog y c hosen to avoid t he e x p e r i m e nt, a n d l o c a t e d a fe w m i l l i m e- awaited recent heavy-ion results where ATLAS s h i g h b a c k g r o u n d for s a m e-fl a v o u r l e p t o n tres from the beam 210 metres either milestones measured muon pairs from photon Learn more on our website www.spdevices.com CERN COURIER SEPTEMBER/OCTOBER 2020 15

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collisions and t he k inemat ic proper t ies γγ → WW and γγ → ℓℓ interactions lay interesting with the increased dataset ψ(2S) and χC, and modifying their feed- maximum positive deviation for λθ (cor- o f l i g ht-b y-l i g ht s c a t t e r i n g – a v e r y r a r e t h e g r o u n d w or k for f ut u r e, m or e d e t a i l e d of Run 3 and t he High-Luminosit y LHC. down fractions into the ground state, J/ψ → μ+μ–, helicity responding to a transverse polarisation) 0.8 process predicted by quantum electro- t e s t s o f t h e S M . F u r t h e r r e s u l t s u s i n g t h e J/ψ. T h i s e ffe c t m a y l e a d t o a v a r i a t i onf of 2σ for 2 < pT < 4 GeV in the helicity ref- dynamics. Interestingly, the latter was A F P s p e c t r o m e t e r c a n i m pr o v e t h e or e t i c a l Further reading the overall polarisation values since dif- erence frame. Interestingly, the corre- also used to search for the axion-like understanding of photon collisions that ATLAS Collab. 2020 ATLAS-CONF-2020-038. ferent charmonium states are expected 0.4 sponding LHCb pp result for prompt J/ψ

p a r t i c l e s pr e d i c t e d b y c e r t a i n e x t e n s i o n s will also benefit future measurements ATLAS Collab. 2020 ATLAS-CONF-2020-041. to be produced with different polarisa- at √(sNN) = 7 TeV instead shows a small

of the SM. of γγ → W W pr o d u c t io n. T h e s e l a n d m a r k ATLAS Collab. 2020 CERN-EP-2020-135. tions. In addition, the recombination of θ but significant longitudinal polarisation.

λ 0 The techniques developed to study e x p e r i m e nt a l fe a t s w i l l o n l y b e c o m e m or e ATLAS Collab. 2020 CERN-EP-2020-138. uncorrelated heavy-quark pairs inside T h e o b s e r v a t i o n o f a s i g n i fic a nt d i ffe r- the QGP gives rise to an extra source of ence between J/ψ polarisation results in CMS J/ψ, which can further modify the overall –0.4 pp and Pb–Pb collisions motivates fur-

polarisation with respect to pp collisions. ALICE, Pb–Pb √s NN = 5.02 TeV, 2.5 < y < 4 ther experimental and theoretical stud- CMS reaffirms exotic nature of the X(3872) The ALICE experiment has recently –0.8 LHCb, pp √s = 7 TeV, 3 < y < 3.5 ies, with the main goal of connecting made t he first measurements of t he J/ψ this observable with the known suppres- Exotic charmonium-like states are a very a similar ratio for the decays involving and ϒ(1S) polarisation in Pb–Pb colli- sion and regeneration mechanisms in CMS 140 fb–1 (13 TeV) 02468 10 12 active field of study at the LHC. These ψ(2 S) i s c o n s i s t e nt w it h u n it y. T h i s i s n o t sions. The data correspond to a centre- p [GeV] heavy-ion collisions. For the rarer ϒ(1S), data T states have atypical properties such as expected from naive “spectator-quark” o f-m a s s e n e r g y √(s ) = 5.02 TeV, and the a bound state of a bottom and an anti- 180 fit NN non-zero electric charges and strong con sider at ion s, ba se d on a si mple t re e- rapidity range 2.5 < y < 4. The measure- Fig. 1. Inclusive J/ψ polarisation parameters as a function of bottom quark, the inclusive polarisation (X(3872), φ) decays that violate isospin symmetry. 140 (X(3872), bkg) level diagram, and assuming X(3872) is ments were carried out in the dimuon trans verse momentum for Pb–Pb collisions at √(s NN) = 5.02 TeV. parameters were found to be compatible The exotic X(3872) charmonium state (bkg, φ) a p u r e c h a r m o n iu m s t a t e. T h e m e a s u r e d decay channel, and results were obtained The results are compared to proton–proton collisions observed by with zero within sizeable uncertainties. discovered by the Belle collaboration 100 (bkg, bkg) ratio also happens to be consistent with i n t w o d i ffe r e nt r e fe r e n c e f r a m e s, h e l ic ity LHCb for prompt J/ψ at √s = 7 TeV (Eur. Phys. J. C 2013 73 2631). A higher precision and momentum-dif- in 2003 displays such isospin-violating the analogous ratio for the B0 → X(3872) and Collins–Soper, each of them with its ferential measurement will be enabled strong decays and has a natural width 60 K0 to B + → X(3872)K+ decays, t houg h t he o w n d e fi n it i o n o f t h e q u a nt i s a t i o n a xis. boosted in the quarkonium rest frame by the ten-fold larger Pb–Pb luminosity candidates/5 MeV of about 1 MeV, which is unexpectedly latter ratio has not yet been measured In the helicity frame, the quarkonium is used in the Collins–Soper frame. The expected in Run 3 of the LHC. 20 narrow for a state with mass very close with high accuracy. The results suggest momentum direction in the labora- J/ψ polarisation parameters, evaluated in – to the D*0 D0 t hreshold. that spectator quarks behave differently tory is chosen, while the bisector of the three p bins covering the range between Further reading 3.80 3.85 3.90 3.95 T Several theoretical interpretations in the B + and B 0 two-body decays into angle formed by the two colliding beams 2 and 10 GeV, are close to zero, but with a ALICE Collab. 2020 arXiv:2005.11128. m(J/ψπ+π–) [GeV] (s) of the internal structure of these char- X(3872) and a light meson. In a recent m on iu m-l i k e s t at e s h a v e b e e n pro p o s e d theoretical paper, former CERN Direc- LHCb 1 to explain their peculiar properties. To of the corresponding rates for decays to Fig. 1. The t or-G e n e r a l L u c i a n o M a i a n i a n d c ol l a b - c h o o s e t h e m o s t a d e q u a t e m o d e l for e a c h X(3872) s h o w d i ffe r e n c e s, h o w e v e r, w h i c h reconstructed orators pointed out that the new CMS LHCb explores 4 state, we must continue studying their may provide a clue to the nature of this invariant mass m e a s u r e m e nt c a n n a t u r a l l y b e e x pl a i n e d –1 properties and improving the determi- exotic charmonium-like state. distribution of by a tetraquark model of X(3872), which dark-sector 10 + – 2 nation of their parameters. As for the Recently the CMS collaboration X(3872) → J/ψπ π d e s c r i b e s t h i s e x o t ic p a r t ic l e a s a b o u n d 0 0

confinement [c τ (X)/mm] X(3872), although it is inconsistent with o b s e r v e d t h e d e c a y B s → X(3872)φ for t h e for Bs → X(3872)φ state of a diquark (charm and up quarks)

10 10–2 the predicted conventional charmonium fi r s t t i m e, w it h a s i g n i fic a n c e e x c e eding candidates. and its anti-diquark. 0 s t a t e s a n d d o e s n o t h a v e a d e fi n it e i s o s pi n, five st a nda rd de v iat ions. The X(3872) is Further studies of X(3872) are now The possibility that dark-matter parti- log + – its production partially resembles that of reconstructed via its decay to J/ψπ π , important in order to gain a deeper cles may interact via an unknown force, LHCb ordinary charmonium states such as ψ(2S) followed by a decay of the J/ψ meson into understanding of its exotic properties felt only feebly by Standard Model (SM) –2 10–3

or χc1(1 P). O n e o f t he w a y s t o e v a lu at e t he a pair of muons, and of the φ meson to a and uncover its mysterious nature. The particles, has motivated substantial 0.3 0.5 1 3 d e g r e e o f s i m i l a r it y b e t w e e n X(3872) a n d pair of c harged kaons (fig ure 1). results may have interesting conse- efforts to search for dark forces. The m(X) [GeV] ψ(2 S) i s t o c o m p a r e t h e i r pr o d u c t io n r a t e s At a simple Feynman-diagram level, q u e n c e s for o u r u n d e r s t a n d i n g o f q u a n- force-carrying particle for such hypoth- i n e x c lu s i v e b -h a d r o n d e c a y s. I n t h e c a s e this decay is a close analogue to the tum chromodynamics. esised interactions is often referred to of ψ(2S), which is a conventional char- B+ → X(3872)K+ a n d B 0 → X(3872)K0 d e c a y s as a dark photon, in analogy with the Fig. 1. 90% ios that exhibit confinement in the dark the searches found evidence for a signal m o n iu m s t a t e, t h e br a n c h i n g f r a c t i o n s o f t h a t h a v e pr e v io u s l y b e e n o b s e r v e d. T h e Further reading ordinary photon that mediates the elec- confidence upper sector, similar to how the strong nuclear and exclusion limits were placed on the 0 + + + – t h e d e c a y s B s → ψ (2S)φ, B → ψ (2S)K , a n d ratio of the branching fractions of this CMS Collab. 2020 arXiv:2005.04764. tromagnetic interaction. limits on the kinetic force confines SM quarks, would pro- X → μ μ cross sections, each with min- 0 0 0 + B → ψ (2S)K , are approximately equal to n e w B s d e c a y t o t h a t o f t h e B d e c a y i s s i g- L Maiani, A D Polosa and V Riquer 2020 In the minimal dark-photon scenario, mixing strength duce a high multiplicity of light hidden imal model dependence. each other. Recent CMS measurements n i fic a nt l y b e l o w u n it y a t 0.48 ± 0.10, w h i l e arXiv:2005.08764. the dark photon does not couple directly between photons hadrons from showering processes in a For many types of dark-sector mod- to SM particles; however, quantum- and composite similar way to jet production in the SM. els, these limits are the most stringent ALICE mechanical mixing between the photon hidden-valley These hidden hadrons would typically to date. This is especially true for the J/ψ polarisation Polarisation however, and measurements at the LHC I n p p c ol l i s i o n s, p ol a r i s a t i o n h a s b e e n and dark-photon fields can generate a bosons, X (colour decay displaced from the proton–pro- H V s c e n a r io (s e e fi g u r e), for w h ic h L HC b studies pose significant further challenges. mainly used to investigate the J/ψ pro- small interaction, providing a portal scale), for a scenario ton collision, thus failing the criteria has placed the first such constraints on differs in lead represent ALICE measures quarkonia spin ori- duction mechanism. Reproducing the through which dark photons may be that exhibits employed in previous dark-photon physically relevant HV mixing strengths entations with respect to a chosen axis small values of polarisation parameter produced and through which they might confinement, as a searches to suppress backgrounds due in this mass range. a valuable via a measurement of the anisotropy in o b s e r ve d at t he LHC i s a c h a l le nge for decay into v isible final states. function of mass and to heavy-flavour quarks. Therefore, it These results demonstrate the unique collisions λθ tool for the the angular distribution of the decay m a n y t h e or e t i c a l m o d e l s. Unt i l r e c e nt l y, While the minimal dark-photon model proper decay length. is desirable to perform experimental sensitivity of the LHCb experiment to Q u a r k o n i a, t h e b o u n d s t a t e s o f c h a r m a n d study of the products. The angular distribution is n o c or r e s p o n d i n g r e s u l t s w e r e a v a i l a bl e is both compelling and simple, it is not The grey box was searches for dark sectors that are less dark sectors. Looking forward to Run 3, anti-charm or bottom and anti-bottom properties of parametrised in terms of the polarisa- for nucleus–nucleus collisions, and in the only viable dark-sector scenario. vetoed due to a large model dependent, by not focusing solely the trigger will be upgraded, greatly q u a r k s, a r e a n i m p or t a nt t o ol t o t e s t o u r tion parameters, , and , where this domain polarisation studies rep- quark–gluon λθ λφ λθφ θ Many other well-motivated dark-sector doubly misidentified on the minimal dark-photon scenario. increasing the efficiency to low-mass k n o w l e d g e o f q u a nt u m c h r o m o d y n a m i c s and φ a r e t h e p ol a r a n d a z i m ut h a l e m i s- resent a valuable tool for the study of background. plasma models exist, and some of these would KS Using its Run-2 data sample, LHCb dark sectors, and the luminosity will be (QCD). At t he LHC, t he study of quarko- sion angles. If all of them are null, no the properties of quark–gluon plasma have avoided detection in all previous recently performed searches for both higher. Taken together, these improve-

nia polarisations offers a valuable new polarisation is present, whereas (λθ = 1, (Q GP). T h e for m a t io n o f t h i s d e c o n fi n e d, experimental searches. Fully exploring short-lived and long-lived exotic bos- ments will further expand LHCb’s

window onto how heavy quarks bind λφ = 0, λθφ = 0) a nd (λθ = –1, λφ = 0, λθφ = 0) strongly interacting medium impacts the space of dark sectors is vital given ons that decay into the dimuon final world-leading dark-sector programme. together in such states. Understanding indicate a polarisation of the spin in the differently on the various quarkonium the lack of signals observed thus far in state. These searches explored the quarkonium polarisation has already transverse and longitudinal directions, resonances, inducing a larger suppres- the simplest scenarios. For example, invariant mass range from near the Further reading s proven to be difficult at lower energies, respectively. sion on the less bound excited states so-called hidden-valley (HV) scenar- dimuon threshold up to 60 GeV. None of LHCb Collab. 2020 arXiv:2007.03923.

16 CERN COURIER SEPTEMBER/OCTOBER 2020 CERN COURIER SEPTEMBER/OCTOBER 2020 17

CCSepOct20_EnergyFrontiers_v3.indd 16 09/09/2020 10:46 CCSepOct20_EnergyFrontiers_v3.indd 17 09/09/2020 10:47 CERNCOURIER www. V o l u m e 6 0 N u m b e r 5 S e p t e m b e r / O c t o b e r 2 0 2 0 CERNCOURIER.COM CERNCOURIER.COM ADVERTISING FEATURE FIELD EPICS integration of the ESS NOTES accelerator cryoplant Reports from events, conferences and meetings InternatIonal ConferenCe of HIgH energy PHysICs

The European Spallation Source (ESS) will be the world’s most powerful pulsed neutron source to provide a means for ICHEP’s online success multidisciplinary research in areas such

as materials science, life sciences, energy, ICHEP 2020 Originally set to take place in Prague, the environmental technology, cultural heritage and fundamental physics. ESS plans the first International Conference of High Energy experiments for 2023 with the commencement Physics (ICHEP) took place virtually from 28 July to 6 August. Running a major of the user programme. Ivana Mustać Kostevc describes how it was possible to adapt an biennial meeting virtually was always industrial solution for a cryogenic plant going to be extremely difficult, but the (cryoplant) to the custom requirements of the local organisers rose to the challenge by ESS EPICS environment. embracing technologies such as Zoom and YouTube. To allow global partici- The proton linear accelerator of ESS will pation, the conference was spread over contain three cryogenic refrigeration/ eight days rather than the usual six, with liquefaction plants and an extensive cryogenic presentations compressed into five-hour distribution system. The accelerator cryoplant slots that were streamed twice: first as (ACCP), which is currently in the phase of a live “premiere” and later as recorded commissioning, is the largest of the ESS “r e pl a y” s e s s io n s, for t h e b e n e fit o f p ar- cryoplants. Its primary purpose is to cool the t icipants in different t ime zones. Building bridges A photo-collage of ICHEP delegates mapped to the Charles Bridge – a Prague landmark superconducting RF cavities to a temperature Example of a cryoplant, courtesy of Linde Kryotechnik AG. This was the first ICHEP meeting that has facilitated trade between eastern and western Europe since the 15th century. of 2 K via saturated He-II baths through since the publication of the update of the several cryomodules. Apart from that, a technical safety requirements and For the screen design we used templates, European strategy for particle physics, top quark), indicating the universality of by ATLAS and CMS were truly impressive forced flow of 4.5 K helium is supplied in a deterministic sequence programmes, is wherever possible. which presented an ambitious vision for the Standard-Model Higgs boson as the and we should not forget that it is still second circuit to cool the RF power couplers, carried out by a Siemens Step 7- 400 PLC. the future of CERN. Though VIP-guest mechanism through which all Standard relatively early in the LHC programme. and a third circuit provides helium at around All relevant control points are collected and A large and complex system like a cryoplant Peter Gabriel – rock star and human- Model particles acquire mass. These are In parallel, direct searches for new phe- 40 K to cool the thermal radiation shields. processed by the PLC and distributed and is always customised by an experienced rights advocate – may not have been highly non-trivial statements. nomena, such as supersymmetry and the The ACCP provides cooling for all three of exposed to the operator via a dedicated IOC supplier. However, when considering an aware of this when delivering his open- ATLAS also presented a combined “unexpected”, continues apace. Results these circuits. running EPICS. The interface between the PLC extensive facility such as ESS, all systems ing remarks, his urging that delegates measurement of the Higgs signal from direct searches at the energy fron- and the IOC is implemented through the s7plc must be integrated into the central control speak up for science and engage with strength, which describes a common tier were covered in numerous parallel The two main ACCP subsystems are the warm EPICS driver, which is based on the Siemens system similarly – employing the same politicians resonated with the physicists scaling of the expected Higgs-boson session presentations. The current status compressor station and the coldbox. The send/receive protocol. technologies that are used for other virtually present. yields in all processes, of 1.06 ± 0.07. In was summarised succinctly by Paris Sph- warm compressor station consists of three subsystems. The latter is vital for operators M a n y s c i e nt i fic h i g h l i g ht s w e r e c o v erd this measurement, the experimental and icas (Athens) in his conference summary oil-lubricated compressor skids with a bulk oil The EPICS database covers the input and and becomes a necessity when considering at ICHEP and it is only possible to scratch theoretical uncertainties are now roughly talk: “Looked for a lot of possible new removal system and oil and gas filters, a final output of all relevant control points and maintenance throughout the system’s the surface here. The results from all four equal, emphasising the ever-increasing things. Nothing has turned up yet. Still oil removal system and a gas management additional functionalities such as the lifecycle. In ESS’s case, Cosylab put particular major LHC experiments were particularly importance of theoretical developments looking intensively.” panel consisting of valves and pipe terminals communication logic with the PLC, recovery emphasis on managing device configuration impressive and the collective progress in in keeping up with the experimental pro- for the process control. There is a single of set-points after a system shut down and in the cryoplant as the latter changes during understanding the properties of neutrinos gress; a feature that will ultimately deter- Flavour physics coldbox with a number of heat exchangers, locking access to a single workstation. development and testing. The final product shows no sign of slowing down. mine the precision that will be reached Over the last few years, a number of expansion turbines, a cold compressor Data from the PLC to the IOC is stored and was the functioning “missing link” between system, adsorbers, filters, electrical heaters recovered by the PLC while IOC setpoints the industrial solution of the cryoplant by the LHC and high-luminosity LHC deviations from theoretical predictions and other equipment. are stored on the IOC. The EPICS database manufacturer and the custom requirements Higgs physics (HL-LHC) Higgs physics programmes. have been observed in B-meson decays to provides the option to either initialize all data of ESS’s control system – the EPICS AT L A S a nd C M S pre s e nte d t he fi r s t e v i- More generally, the precision we are final states with leptons. Discrepancies Many manual and remote valves will be to their last values on the IOC, or to copy their environment. dence for the decay of the Higgs boson seeing from the ATLAS and CMS Run 2 have been observed in ratios of decays installed for different purposes, for example respective readbacks from the PLC. into a pair of muons (two and three proton–proton data is truly impressive, to different lepton species, and in the ABOUT THE AUTHOR to isolate specific loops, to protect the system standard deviations, respectively, see p7). and an exciting indication of what is to angular distributions of decay products Ivana Mustać Kostevc started working Combined, the results provide strong evi- come as the integrated luminosity accu- (CERN Courier May/June 2020 p10). Taken against loss of oil or helium and safety valves Since the ACCP is a large and complicated at Cosylab in 2015. She holds a PhD to protect the system against overpressure. system, we structured its graphical user in physics with a topic in elementary dence for the coupling of the Higgs boson mulated by the experiments ramps up, alone, each of these discrepancies are not Measuring points necessary for operation interface hierarchically. At the top level, particle physics. She is a senior to the muon, with the strength of the and then ramps up again in the HL-LHC p a r t ic u l a rl y s i g n i fic a nt, b ut c ol l e c t i v e l y team leader in the Scientific Services The collective and protection of the equipment include a process diagram of the whole system department and an expert in designing coupling consistent with that predicted era. One interesting new example was they may be telling us something new points for helium mass flow and water flow, provides a quick overview of the cryoplant’s EPICS-based control systems. Kostevc in the Standard Model. Prior to these the first observation of WW production progress in about nature. At ICHEP 2020, the LHCb was the technical lead on the EPICS position of all control valves, limit switches most critical measuring points. Due to the integration project for the ESS ACCP. new results, the Higgs had only been from photon–photon collisions, where understanding experiment presented their recently for manual valves, oil-level, oil and helium, complexity of the ACCP control system, we Her hobbies are dancing and cycling. observed to couple to the much heavier the photons are radiated from the incom- the properties published results on the angular analy- e-mail [email protected] 0 *0 + – impurity, helium, water, and oil temperatures. automated as much as possible. Appropriate third-generation fermions and the W and ing proton beams (see p15). This is a neat of neutrinos sis in B → K μ μ . The overall picture These measurements, and control over the Python scripts parse the PLC variables and Z gauge bosons. The measurements also measurement that demonstrates the remains unchanged. The full analysis devices mentioned above, are exposed to the all relevant information to create the EPICS provide further evidence for the linear- breadth of physics accessible at the LHC. shows no of the LHCb Run-2 data set, including operators by the ESS control system. database and configuration files for services ity of the Higgs coupling, now over four Overall, the range and Standard Model sign of updated measurements of the relative s such as the alarm handler and archiving Cosylab, Control System Laboratory orders of magnitude (from the muon to measurements presented at ICHEP 2020 slowing down rates of the muon and electron decay Supervision of all functions of the ACCP service. The latter ensures that all services Tel +386 1 477 66 76 control system, including substantial are up to date with the EPICS database. Email [email protected] | Web www.cosylab.com CERN COURIER SEPTEMBER/OCTOBER 2020 19

CCSepOct20_Fieldnotes_v2.indd 19 09/09/2020 10:40 CERNCOURIER www. V o l u m e 6 0 N u m b e r 5 S e p t e m b e r / O c t o b e r 2 0 2 0 CERNCOURIER.COM

FIELD NOTES

modes (RK and RK*), is eagerly awaited. The search Updates were presented by the NOvA Virtual success The search for rare kaon decays con- for rare experiment in the USA and the T2K A vast range of high-qualify scientific tinues to attract interest. One of the most kaon decays experiment in Japan. Both experiments research was covered in the 800 parallel impressive results presented at ICHEP favour the normal-ordering hypothe- session presentations and summarised was the recent observation by NA62 of continues sis, although not definitively, and there in the 44 plenary talks at ICHEP 2020. the extremely rare kaon decay, K+ → π+ νν–. to attract is currently a slight tension between The quality of the presentations was Occurring only once in every 10 billion interest the CP violation results from the two high, and speakers coped well with the SDD decays, this is an incredibly challenging experiments. It is worth noting that challenge of pre-recording talks. The measurement and the new NA62 result is the combined interpretation of the two “replay” sessions worked extremely Silicon Drift Detectors the first statistically significant obser- experiments is quite complex. The NOvA well too – an innovation that is likely to vation of this decay, based on just 17 and T2K collaborations are working on a persist in the post-COVID world. About events (see p9). Whilst the observed rate combined analysis to clarify the situation. 3000 people registered for the meeting, for Science at the Speed of Light is consistent with the Standard Model There were also a number of pres- which is more than double the previous expectation, its observation opens up entations on the next generation of two events. It was particularly pleasing Technologically Advanced Silicon Drift Detectors a new future avenue for exploring the long-baseline neutrino oscillation to learn that almost 2500 connected to possible effects of new physics. experiments, DUNE in the US and the parallel sessions. Hyper-Kamiokande in Japan, which Despite the many successes, we all Exceptional Rise Time — Rise times <25 ns Neutrino physics aim to make the definitive discovery missed the opportunity to meet col- Neutrino physics continues to be one of of CP violation in the neutrino sector. leagues in person; it is often the informal Outstanding Throughput — Output count rates >5 Mcps the most active areas of research in par- In the context of DUNE, the progress d i s c u s s i o n s o v e r c o ffe e or i n r e s t a u r a nt s ticle physics (CERN Courier July/August with liquid-argon time-projec- and bars that generate new ideas and, Superior Energy Resolution — Energy resolution <230 eV at 3 Mcps (OCR) 2020 p32), so it was not surprising that tion-chamber (LArTPC) detector tech- importantly, lead to new collaborations. the neutrino parallel sessions were the nology is impressive. It was particularly Whilst virtual conferences are likely Unique Sensor Thickness — Thickness available 0.5 mm, 1.0 mm and 2.0 mm best attended of the conference. This pleasing to see a number of physics to remain a feature in the post- is a particularly interesting time, with results from MicroBooNE at Fermilab, COVID world, they will not replace long-baseline neutrino oscillation and the single-phase DUNE detector in-person events. experiments becoming sensitive to the prototype at CERN, that are based on The VORTEX® range Silicon Drift Detectors, available with a selection of configurations including neutrino mass ordering, and beginning the automatic reconstruction of LArTPC Mark Thomson STFC and the University Sensor Thickness — 0.5, 1.0 and 2.0 mm to provide constraints on CP violation. images – a longstanding challenge. of Cambridge. Active Areas — 50, 65 and 100 mm2 NeutriNo 2020 Probe Lengths — From 60 to over 600 mm Neutrino 2020 zooms into virtual reality

Sensor Arrays and Designs — Single, Multiple, Planar, Focused Tutto/Fermilab M Del More than 4000 people from every conti- Environments — Air, vacuum, UHV and He nent, including Antarctica, participated from 22 June to 2 July in the XXIX Inter- Number of Sensors — Single VORTEX® EX and EM SDD national Conference on Neutrino Phys- ics and Astrophysics, which was hosted — Three VORTEX® ME-3 SDD online by Fermilab and the University of Minnesota. Originally planned as a — Four VORTEX® ME-4 SDD five-day in-person June meeting at a large hotel in Chicago city centre, the — Seven VORTEX® ME-7 SDD organisers quickly pivoted in March, due to COVID-19, to an online programme Customization — Contact [email protected] with eight half days over two weeks, four poster sessions with both web-based and virtual-reality displays, and the use of the Slack platform for speaker questions and ongoing discussions. A highlight of the conference was the first observation of solar CNO neutri- nos by the Borexino collaboration, which operates a 280 tonne liquid-scintillator of CNO and 210Bi neutrinos. “The quest Neutrino 2020 was the report from the Gerda collab- detector in Italy’s Gran Sasso Laboratory. for CNO is turned into the quest for 210Bi avatars oration on the search for neutrino-less Dominant in stars more than 1.3 times the through 210Po,” he emphasised. “With The conference’s double beta decay. If observed, this pro- mass of the Sun, the CNO cycle accounts this outcome, Borexino has completely poster session took cess would confirm the long-suspected for about 1% of the Sun’s energy and unravelled the two processes power- place in virtual Majorana rather than Dirac-fermion generates a difficult-to-detect neutrino ing the Sun – the pp chain and the CNO reality. nature of neutrinos – a beyond the flux similar to backgrounds due to decays cycle.” The final data analysis yielded Standard Model feature with intriguing in the detector of 210Bi and its daughter a 5.1σ statistic against a hypothesis of implications for why the neutrino mass nucleus 210Po. Gioacchino Ranucci (INFN, no CNO neutrinos, and a CNO flux at the is so small. Since Neutrino 2018, Gerda +2.9 8 –2 –1 M i l a n o) e x pl a i n e d t h a t t h e s p e c t r a l fit t o Earth of 7.0–1.9 × 10 cm s (see p11). has nearly doubled its Phase 2 exposure s Hitachi High-Tech Science America, Inc. www.hitachi-hightech.com/hhs-us/ the observed data returns only the sum Another highlight from Gran Sasso and added a liquid-argon veto and a 21770 Nordhoff St., Chatsworth, CA 91311 Email: [email protected] Tel: +1-818-280-0745 CERN COURIER SEPTEMBER/OCTOBER 2020 21

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FIELD NOTES HIGH PRECISION POWER SUPPLIES

EACTLY. new detector string. The now complete A highlight of muon disappearance determined by the in-person conference, the virtual real- HIGH VOLTAGE. Phase 2 result is a 90% confidence level the conference now completed long-baseline MINOS/ ity (VR) poster presentation was novel 26 half-life of > 1.8 × 10 years according w a s t he fi r st MINOS+ collaboration. These limits are and unique. Marco Del Tutto (Fermilab) to a frequentist analysis, or > 1.4 × 1026 in tension with the appearance data from created multiple virtual “rooms” for observation years, according to a Bayesian analysis both LSND and MiniBooNE when ana- five posters each, along with additional with additional prior assumptions. Talks of solar CNO lysed as ev idence for sterile neut rinos. rooms for topical discussions, sightsee- describing a half-dozen other double-be- neutrinos Two talks described the world’s i n g i n C h i c a g o a n d v i s it i n g Fe r m i l a b. T h e ta-decay experiments displayed the high 200 km-scale neutrino-oscillation most enabling feature of the VR was that OUT NOW level of interest in t his field. e x p e r i m e nt s, NO vA a n d T 2 K . T h e d e g e n- the software facilitated dialogue between eracy of mass difference, mixing angle, participants whose avatars could move Sterile neutrinos hierarchy and possible CP violation around the space and speak with one Searches for additional “sterile” neu- make interpretation of these experi- another. For example, if a group of ava- WITH ONBOARD trinos with no Standard Model gauge ments’ results quite complex. Inter- tars clustered around a poster, the par- interactions were also featured. Taka- estingly, there is mild tension, albeit ticipants could discuss the poster as a sumi Maruyama (KEK) described the only at the 1σ level, between the NOvA group. The VR feature attracted 3409 par- 2 PYTHON SCRIPTING liquid-scintillator JSNS experiment as and T2K results regarding leptonic CP ticipants. The VR was also supplemented a direct test of the controversial LSND conservation and the neutrino mass by two-minute videos from presenters, experiment result, first reported about hierarchy. The two collaborations are w h ic h e n a ble d 5800 Yo uT ub e v ie w s a n d 25 years ago. JSNS2 c ol l e c t e d it s fi r s t d a t a now working together on a combined 60,600 web displays. during the three weeks before Neutrino analysis. Several talks discussed future 2020. Adrien Hourlier (MIT) reported on initiatives. Lia Merminga (Fermilab) Exciting physics the now complete analysis of data from r e p or t e d o n L BN F a n d PI P-II, w h i c h w i l l In the closing remarks, the organis- MiniBooNE that was collected during result in a new neutrino beam from Fer- ers acknowledged the challenges of an the past 17 years. Combining neutrino milab to the Sanford Laboratory in South online conference, but also emphasised and anti-neutrino modes, MiniBooNE D a k o t a for t h e DU N E e x p e r i m e nt. C o m- the strengths of this novel approach. reports a 4.8σ excess. Hourlier presented bined, these two projects will result in a The exciting physics of Neutrino 2020 soon-to-be published detailed distribu- beam power of 2.4 MW, more than three w as made av a i lable to a n e x tensive a nd tions that the collaboration hopes “will times the intensity of the current NuMI diverse audience, including many sci- guide theorists to explain our data”. beam. Michael Mooney (Colorado State) entists who would not have been able to Minerba Betancourt (Fermilab) then reported on the enormous progress of the attend an in-person conference because described the Fermilab Short-Baseline DUNE project with two successful pro- of funding, visas, family concerns or Neutrino (SBN) programme, which will totype detectors operating at CERN and other issues. About 60% of participants use three detectors to obtain a defini- pre-excavation work progressing at San- were students or post-docs and the tive result on neutrino oscillations for ford Laboratory. Complementary to the conference reached participants from an LSND and MiniBooNE-like ratio l iq u id-a r gon t e c h nolo g y o f DU N E i s t he 67 countries. The Slack discussions and of oscillation distance to energy of recently approved Hyper-Kamiokande posts on social media indicated wide- ~1 m/MeV. The beam neutrino energy water-Cherenkov detector, which was spread praise that the online format peaks at 700 MeV. A new liquid-argon described by Masaki Ishitsuka (Tokyo worked as well as it did. Some aspects NEW n e a r d e t e c t or (SBN D) w i l l b e pl a c e d 1 10 m Un i v e r s it y o f S c i e n c e). Hy p e r-K w i l l h a v e of Neutrino 2020 may well affect the from the target. The existing MicroBooNE a total mass of 260 kilotonne and 8.4 planning and organisation of future i s l o c a t e d a t 470 m a n d t h e IC A RUS D e t e c- times the fiducial volume of the current in-person and online conferences. EDIT your python script directly on browser or locally with t or, m o v e d f r o m G r a n S a s s o, i s i n s t a l l e d Super-Kamiokande detector. access to all hardware parameters at 600 m. Thomas Carroll (Wisconsin) While much of Neutrino 2020 was Steve Brice and Sam Zeller Fermilab, and reported on sterile-neutrino limits by modelled after the usual features of an Marvin Marshak University of Minnesota. UPLOAD and start the script directly on iCS capable device Ter ascale summer school International per day. Active moderation was key, with appeal students typing questions in the chat CREATE your own visualisation easily in HTML / Javascript / CSS Terascale summer Forced online by box, and the moderator interrupting school goes global the pandemic, the the lecturer when appropriate to give summer school the participants a chance to speak up. THOUSANDS OF APPLICATIONS POSSIBLE drew particularly This format conferred upon less brash Data logging, event driven voltage channel control, testing, external control of voltage (by temperature changes), block rampup. In a new venture by physicists at DESY, high participation participants a more comfortable way to Start easily with the iseg datalogger example, which stores measured values directly on USB flash drive. the first Terascale Summer School took from Cuba, Egypt, ask questions, several students noted. place online from 23 July to 12 August, India, Malaysia and When one brave pioneer had broken the Download the latest version from: www.iseg-hv.com/ics providing more than 160 undergradu- Russia. ice, queries flowed every few minutes – a ate students from more than 30 coun- r e s o n a n c e e ffe c t c h a r a c t e r i s e d b y a l i v e ly, runs on: MMS / Mpod multichannel Low and High Voltage tries with an engaging introduction to stimulating and relaxed atmosphere that supplies with CC24 Controller card SHR labratory High Voltage the world of particle and astroparticle boosted concentration levels. iCSmini2 Source-Measure-Unit physics. Following a wide-ranging three With its global reach and breathing controller box weeks of teaching, an impromptu fort- space for students to explore concepts night-long online tutorial, which only independently, Terascale 2020’s compact concluded yesterday, focused on strong As the school had been forced online online format may merit consideration interactions and Monte Carlo techniques, due to the ongoing pandemic, the organ- during less extraordinary times too. allowing students to deepen their knowl- isers settled upon a reduced programme edge through practical exercises. with just one or two 45 minutes lectures Olaf Behnke DESY Hamburg.

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FEATURE MULTI-QUARK STATES Got radiation? TETRAQUARKS BACK See what you’ve been missing IN THE SPOTLIGHT

A hidden-double-charm tetraquark D Dominguez/CERN observed recently by the LHCb collaboration has reinvigorated the debate over whether tetraquarks are loosely bound pairs of mesons or tightly bound pairs of diquarks.

he existence of particles with fractional charges and fractional baryon numbers was a hard sell in 1964 Twhen Gell-Mann and Zweig independently proposed the quark model. Physicists remained sceptical until the discovery of the J/ψ meson 10 years later. Heavier than any- Photo courtesy of EUROfusion. Website: www.euro-fusion.org thing previously seen and extremely narrow, with a width of just 0.1 MeV and a mass of 3097 MeV, the J/ψ pointed to the existence of a new quark with its own quantum num- Imaging in radiation environments just got easier b e r. T h i s c o n fi r m e d G l a s h o w, I l io p o u lo s a n d M a i a n i’s 1970 hypothesis, which they cooked up to explain peculiarities in rare kaon decays. Any doubt as to the existence of a With superior capabilities for operating in radiation environments, the MegaRAD cameras provide charm–anticharm system was eliminated by observing narrow excitations of the J/ψ, which lined up as expected excellent image quality well beyond dose limitations of conventional cameras, and are well suited in non-relativistic quantum mechanics. The spectrum of for radiation hardened imaging applications charmonium mesons soon became populated by states with widths up to hundreds of MeV as their masses surpassed the threshold for decaying to a pair of “open-charm” mesons with a single charm quark each. Diquark dilemma An artist’s impression of a hidden-double-charm tetraquark. Hadron spectroscopy continues to be a rich area of fun- In the pictured model, a pair of colour-charged diquarks are bound together by damental exploration today, with results from collider the exchange of gluons. experiments over the past two decades revealing the exist- ence of multi-quark states more exotic than the familiar (qqqqq–) and hexaquarks (qqqq––qq–– or qqqqqq) were all sug- mesons and baryons (CERN Courier April 2017 p31). The LHCb gested. In the early 1970s, a deepening understanding of experiment at CERN is at the forefront of this work. Now, the dynamics of strong interactions brought about by QCD a structure in the J/ψ-pair mass spectrum consistent with only furthered the motivation for seeking new multi-quark MegaRAD3 produce color MegaRAD10 produce color KiloRAD PTZ radiation a tetraquark state made up of two charm quarks and two states. QCD not only predicted attractive forces between or monochrome video up to or monochrome video up to resistant camera with charm antiquarks has been observed by the collabora- a quark and an antiquark, and between three quarks, but 6 7 3 x 10 rads total dose 1 x 10 rads total dose Pan/Tilt/Zoom tion. With doubly hidden charm, the new cccc— state is the also between two quarks. most significant evidence so far for the existence of tightly The attraction between two quarks can easily be proven In the United States: International: bound tetraquarks composed of a pair of colour-charged when they are close together and the strong coupling con- THE AUTHORS For customer service, call 1-800-888-8761 For customer service, call [01] 315-451-9410 “d iq u a r k s”, a n d s h e d s l i g ht o n a d i ffic u lt-t o-m o d e l r e g i me stant is small enough to allow perturbative calculations. Marco Pappagallo To fax an order, use 1-315-451-9421 To fax an order, use [01] 315-451-9421 of quantum chromodynamics (QCD). Similar interactions also likely occur in the non-pertur- bative regime. Such systems, known as diquarks, have INFN and University Email: [email protected] Email: [email protected] of Bari, Liupan An Multi-quark states the colour charge of an antiquark. (For example, red and INFN Sezione di Gell-Mann and Zweig both acknowledged that the sym- blue combine to make an anti-green diquark.) As coloured Firenze and metries which led to the quark hypothesis allowed for objects, they can be confined in hadrons by partnering Tomasz Find out more at thermofisher.com/cidtec m or e c o m pl ic at e d q u a r k c o n fi g u r at io n s t h a n ju s t m e s ons with other coloured constituents. A diquark can attract a Skwarnicki (qq–) and baryons (qqq). Tetraquarks (qq–q–q), pentaquarks quark to create a simple baryon. Alternatively, a diquark Syracuse University.

For Research Use Only. Not for use in diagnostic procedures. © 2020 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific and its subsidiaries unless otherwise specified CERN COURIER SEPTEMBER/OCTOBER 2020 25

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FEATURE MULTI-QUARK STATES FEATURE MULTI-QUARK STATES LHCb Collaboration Four muons LHCb Collaboration Bucking the trend A J/ψ-pair Yukawa-style bindings cannot, however, explain a large LHCb data candidate event in number of broader tetraquark-like structures with hidden 200 total fit the LHCb detector, charm, with widths of hundreds of MeV, which are not resonance in which both near any hadron–hadron threshold. Such states include threshold BW1 160 threshold BW2 mesons decayed the charged Z (4430) observed by Belle in 2008 and later c DPS into a pair of confirmed by LHCb in 2014, and a family of states that NRSPS muons (green decay to a J/ψ φ fi n a l s t at e, i n c lud i n g X(4 1 40) a n d X(4 274), 120 DPS+NRSPS lines). LHCb w h ic h w e r e o b s e r v e d b y t h e C DF c ol l a b or at io n at Fe r m i l a b observed a i n 2009 a nd l ater by C M S a nd LHCb at CER N. These st ates 80 resonance in the could be either manifestations of diquark interactions or invariant mass of k i n e m at ic e ffe c t s n e a r t h e f a l l-a p a r t t h r e s h old. No s ingle such events, which simple model can account for all of them. 40 weighted candidates / (28 MeV) is indicative of a Reaching states with hidden double charm (cccc—) now hidden-double- promises new insights into multi-quark dynamics, as 0 charm tetraquark. all the quarks are non-relativistic. Furthermore, there 7000 8000 9000 is no known mechanism for two charmonium mesons to Mdi-J/ψ [MeV] be loosely bound, according to a molecular model, as no l i g ht v a le n c e q u a r k s a r e a v a i l a ble t o b e e x c h a n g e d. C o m- pact diquark-type tetraquarks have been predicted for tures also appear in the invariant mass spectra of other Di-J/ψ bump The such quark combinations, but it is not clear whether they charmonium or doubly charmed baryon pairs. X(6900) structure and an antidiquark can attract each other to create a Experiments to the fore might lead to experimentally detectable signatures – the The first LHCb upgrade is currently in progress and data (solid red curve) tetraquark. As a result of their direct colour couplings, Molecular tetraquark proposals were fuelled in 2003 by tetraquarks could be too broad or their production rate too taking will recommence at the beginning of LHC Run 3 observed in the such compact tetraquarks can have binding energies of the unexpected discovery by the Belle collaboration, at small. While collisions at the LHC provide enough energy to in 2022, with a second upgrade phase planned to collect a J/ψ-pair mass several hundreds of MeV. the KEKB electron–positron collider in Tsukuba, Japan, of simultaneously produce pairs of charm–anticharm quark muc h l a r g e r d at a s e t b y 2030. T h e AT L A S a n d C M S e x p e r- spectrum. Compact two-diquark tetraquarks stand in stark con- a new narrow state, right at the sum of the masses of a combinations, getting them close enough together to form iments have highly performing muon detectors too, and trast to the alternative “molecular” model for tetraquarks, charmed-meson pair. Unlike other charmonium states near diquarks is a tall order. Additionally, while observations c o u ld a l s o m a k e s i g n i fic a nt c o nt r i b ut io n s t o t h e s t ud y o fthe

which was named by loose analogy with the exchange of its mass, the state is surprisingly narrow, with a width of of beauty-charm mesons such as Bc and doubly charmed n e w X(6900) s t r uc t u r e, w it h b o t h e x i s t i n g a n d f ut u r e d at a.

electrons between atoms in molecules. In this picture, t he order of just 1 MeV. Or ig i na l ly na med X(3872), it is now baryons such as Ξcc showed that LHCb has reached the A key contribution may also be made by Belle’s successor,

the tetraquark is arranged as a pair of mesons that attract conventionally referred to as χ c1(3872), r e fle c t i n g it s n at u re sensitivity to detect the interactions of two heavy quarks, Belle II, currently in its start-up phase, which observes each other by exchanging colour-neutral objects, such as as a possible triplet P-wave state with hidden charm and it was unclear until recently if the interactions of diquark- electron–positron collisions at the SuperKEKB collider at light mesons and glueballs – an idea first proposed in 1935 one unit of total angular momentum. Despite subsequent model tetraquarks could be detected. The observation, energies above the observed J/ψ-pair mass structure. It is by Hideki Yukawa, in the context of interactions between results from collider experiments around the world, there is repor ted i n July, by LHCb, of a h ig h ly sig n i fica nt J/ψ-pair unclear, however, if the collision energy, luminosity and nucleons. Such exchanges only provide a binding energy no consensus about its exact nature, as it variously exhibits mass structure is therefore an exciting moment for the electromagnetic production cross sections will be high of a few MeV per nucleon. features of simple charmonium or a loosely bound molecule. study of multi-quark dynamics. enough to achieve the required sensitivity. Molecular tetraquarks are therefore expected to be only Stronger evidence for the loose meson–meson binding of Re s e a rc h i s a l r e a d y m o v i n g for w a rd q u ic k l y, w it h f u r t h e r loosely bound, with masses near the sum of the masses of mu lt i-q u a r k s t at e s w a s pr o v id e d b y o b s e r v at io n s i n 2013 o f Introducing the X(6900) evidence for diquark tetraquarks coming from an even

their constituent mesons, however they could have rather a hidden-charm tetraquark candidate Zc(3900) by the BES Exploiting the full data set collected from 2011 to 2018, LHCb more recent discovery by LHCb of two “X(2900)” states narrow widths if their mass lies below the “fall-apart” III collaboration at the BEPC II electron–positron collider investigated the J/ψ-pair invariant mass spectrum, where with widths between 57 and 110 MeV. As they decay to a threshold. As such states are most likely to be created in Beijing, China, and by Belle, and of the Z (4020), also by J/ψ meson candidates are reconstructed from the dimuon D+K– fi n a l s t at e, t h e y a r e b o t h o p e n l y c h a r m i n g a n d openly c –– without angular momentum between the mesons, the BES III. Since they have electrically charged forms, they decay mode. A narrow peaking structure at 6900 MeV and s t r a n g e. T h e i r m o s t l i k e l y c o m p o s it io n i s t h at o f a (c s)(ud) spin-parity combinations available to them are highly cannot be counted as charmonium states. They are both a broader structure at approximately twice the J/ψ mass d iq u a r k t e t r a q u a r k. W h i le t h e X(2900) s t at e s d e c a y s t r o n g l y, –– restricted. In contrast, a rich spectrum of radial and relatively narrow states near meson–meson thresholds for t h re s hold w a s o b s e r ve d. The s t r uc t u re of X(6900) i s c on- similar heavy-light diquark systems, such as (cc)(ud), (bc) –– –– angular momentum excitations between the coloured open charm, with widths of the order of tens of MeV. They sistent with the signature of a resonance (see figure), sug- (ud) and (bb)(ud), have been studied theoretically, resulting constituents is predicted for diquark tetraquarks. The are definitely tetraquarks, though it is still a moot point gesting a four-charm-quark state. in varying degrees of confidence that some may be stable

widths of these states could be large, as they can easily if they are genuinely bound states or merely manifesta- While the peaking X(6900) structure is close to the χc0 χ c1 with respect to strong interactions, and instead decay fall apart into lighter hadrons, with their binding energy tions of non-binding hadron–hadron forces that manifest meson-pair threshold, its width, of the order of a hundred w e a k l y, w it h m e a s u r a ble l i fe t i m e s. Hu nt i n g for s uc h s t at e s transformed into a light quark–antiquark pair. in complicated forms. The molecular interpretation had M eV, s e e m s t o o l a r g e t o fit i nt o t h e lo o s e-bi n d i n g s c h eme, i s a n e x c it i n g pr o s p e c t for t h e up g r a d e d L HC b e x p e r i m e nt. Unfortunately, it is difficult to rigorously apply QCD in also been reinforced in 2012 by Belle’s observations of the wherein decay modes other than the “fall-apart” topology LHCb’s new tetraquark observations have once again

t h e c o n fi n i n g r e g i m e o f mu lt i-q u a r k s t at e s. It i s t h e r e fore hidden-beauty Zb(10610) and Z b(10650) tetraquarks. These are expected to be strongly suppressed, and in any case, thrown open the debate on the nature of multi-quark up to experiments to discover which multi-quark states states also have relatively narrow widths of the order of tens there is no known loose binding mechanism between two states. With the theory still mired in non-perturbative This actually exist in nature. There have been some hints of of MeV and masses near the threshold for falling apart, in charmonium states. Charmonium-pair re-scattering calculations, experimental observations will be decisive observation tetraquark states built out of light quarks, though without this case to “open-beauty” mesons. effects are also disfavoured due to the requirements of i n le a d i n g t h e d e v e lo p m e nt o f t h i s s u bj e c t. T h e c o m mu n it y It is up to is the most definite proof. This is largely because additional light quark Pentaquark observations have also weighed in on the such interactions. This observation is therefore the most i s w a it i n g e a g e rl y t o s e e i f o t h e r e x p e r i m e nt s c o n fi r m t h e intriguing experiments pairs can easily be created in the decay process of simple debate. Last year’s observation of three narrow hid- intriguing experimental indication so far for hadrons made LHCb obser v at ion, and shed light on its nature.  to discover mesons and baryons, and the highly relativistic nature of den-charm pentaquarks by the LHCb collaboration, with out of diquarks. experimental which multi- such states makes model predictions for their excitations widths below tens of MeV and masses close to the charm It is less clear if the observed structure is made of one Further reading indication so quark states unreliable. Hidden charm states have proved helpful again, meson-baryon threshold (CERN Courier M a y/ Ju n e 2019 p15), state, or several that may or may not interfere with each LHCb Collaboration 2020 arXiv:2006.16957. far for hadrons actually exist however, as the charmonium spectrum and the properties also points to loose hadron–hadron binding, in this case other. There is no information on the spin-parity of the LHCb Collaboration 2020 arXiv:2009.00025. made out of in nature of such states are well predicted. between a meson and a baryon. o b s e r v e d s t r uc t u r e. Ne it h e r d o w e y e t k n o w i f m a s s s t r uc- LHCb Collaboration 2020 arXiv:2009.00026. diquarks

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ADVERTISING FEATURE FEATURE NEUTRON SCIENCE

ZAO® based non-evaporable Getter pumps in optics vacuum chambers

Vacuum engineers and scientists have long known that even if a sample material is initially clean and handled with ultrahigh- vacuum (UHV) standards, a carbon contamination layer will deposit and grow on the material’s surface after placing it in a high vacuum (HV) or UHV chamber. This condition is also true for the optics vacuum chambers found in particle accelerators and synchrotron beamlines. For the optics vacuum chambers, this situation is worsened by X-ray irradiation, which can result in a one to two orders of magnitude pressure increase and high yield of carbon contaminants. The effects of carbon contamination on the X-ray optics can significantly reduce the X-ray transmission downstream to the experimental stations, carbon K edge, around 285 eV, as well as at conditions. Carbon contamination is not only and as next-generation synchrotrons usher higher energies around 1000 eV. As early as experimentally detected; it is also visually in X-ray brightness increases of two to three the 1980s, this carbon contamination layer evident after a few months to a year of orders of magnitude, it is critical to minimize was shown to cause intensity modulations beamline operation. It will usually appear as a these losses from carbon contamination. in X-ray absorption spectra that closely black line where the X-rays strike the optics. resembled those above the carbon K edge Read the full paper online. Multiple studies have shown that carbon in bulk crystalline graphite. These results contamination develops on X-ray optics and suggested the formation of graphitic SAES Group S.p.A reduces the transmission of photons near the carbon contamination even under UHV Web www.saesgroup.com

On track An aerial view of the European Spallation Source (ESS) construction site in Lund, Sweden, on 28 May 2020. (Credit: P Nordeng/ESS) ESS UNDER CONSTRUCTION

The European Spallation Source (ESS) will provide neutron beams 100 times brighter than those from reactor sources, enabling new research into material properties and fundamental physics.

ust a few years after the discovery of the neutron by James about atomic and molecular structure and dynamics. Neu- Chadwick in 1932, investigations into the properties of trons also carry a magnetic moment. This property, com- Jneutrons by Fermi and others revealed the strong energy bined with their absence of electric charge, make neutrons dependence of the neutron’s interactions with matter. This u n iq ue l y s e n s it i v e t o m a g n e t i s m at a n at o m ic le v e l. O n t h e knowledge enabled the development of sustainable neutron downside, the absence of electric charge means that neu- production by fission, opening the era of atomic energy. The tron-scattering cross sections are much weaker than they fi r s t nuc le a r-fi s s io n r e a c t or s i n t h e 1940 s w e r e a l s o e q u i ped are for X-rays and electrons, making neutron flux a limiting with the capacity for materials irradiation, and some provided factor in t he power of t his met hod for scient ific researc h. low-energy (thermal) neutron beams of sufficient intensity Throughout the 1950s and 1960s, incremental advances in for studies of atomic and molecular structure. Despite the t h e p o w e r o f nuc le a r-r e s e a rc h r e a c t or s a n d i m pr o v e m e nt s high cost of investment in nuclear-research reactors, neutron in moderator design provided increasing fluxes of thermal THE AUTHORS science flourished to become a mainstay among large-scale neutrons. In Europe these developments culminated in the Håkan Danared, facilities for materials research around the world. construction of the 57 MW high-flux reactor (HFR) at the Shane Kennedy and The electrical neutrality of neutrons allows them to probe Institut Laue-Langevin (ILL) in Grenoble, France, with a Mats Lindroos d e e p i nt o m at t e r i n a n o n-d e s t r uc t i v e m a n n e r, w h e r e t h e y compact core containing 9 kg of highly enriched uranium European Spallation scatter off atomic nuclei to reveal important information enabling neutron beams with energies from around 50 μeV Source, Sweden. www.goodfellow.com | [email protected] | 0800 731 4653

CERN COURIER SEPTEMBER/OCTOBER 2020 29

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FEATURE NEUTRON SCIENCE FEATURE NEUTRON SCIENCE ESS U Hammarlund/ESS ESS ESS

Monolith The 6000-tonne target station monolith, consisting of concrete and steel shielding, will surround the target wheel, moderator, cooling systems and beam extraction system. Cool view A section of the cryogenic system for the 600 m-long linear accelerator.

ESS from above Left: the ESS site layout, showing accelerator buildings (dark blue), target (violet), instrument halls (light blue), offices and labs for macromolecular crystallography, two small-angle scat- bi-spectral neutron moderator, which allows a high degree (green) and auxiliary buildings (red and yellow). Right: the positions of the first 15 neutron instruments: diffractometers for hard-matter structure tering instruments for the study of large-scale structures, of flexibility in the choice of neutron energy. determination (DREAM, HEIMDAL and MAGIC), macromolecular crystallography (NMX) and engineering studies (BEER); small-angle scattering t w o r e fle c t o m e t e r s for t h e s t ud y o f s u r f a c e s a n d i nt e r f a c es, instruments for the study of large-scale structures (LOKI and SKADI); reflectometers for the study of surfaces and interfaces (ESTIA and FREIA); five spectrometers for the study of atomic and molecular Accelerator and target spectrometers for the study of atomic and molecular dynamics (BIFROST, C-SPEC, MIRACLES, T-REX and VESPA); and a neutron imaging station (ODIN). dynamics over an energy range from a few μeV to several Most of the existing spallation neutron sources use a linear hundred meV, a diffractometer for engineering studies accelerator to accelerate protons to high energies. The to 500 meV. When the HFR came into operation in 1972, by more than two orders of magnitude. and a neutron imaging station (see “ESS layout” figure). particles are stored in an accumulator ring and are then however, it was clear that nuclear-fission reactors were The idea for the ESS was advanced in the early 1990s. Given that the ESS target system has the capacity for two extracted in a short pulse (typically a few microseconds in already approaching their limit in terms of steady-state The decision in 2009 to locate it in Lund, Sweden, led to neutron moderators and that the beam extraction system le n g t h) t o a h e a v y-m e t a l s p a l l at io n t a r g e t s uc h a s t u n g s t e n neutron flux (roughly 1.5 × 1015 neutrons per cm2 per second). the establishment of an organisation to build and operate a l lo w s v ie w i n g o f e a c h m o d e r at or b y up t o 4 2 b e a m p or t s, or mercury, which have a high neutron yield. A notable In an effort to maintain pace with advances in other the facility (ESS AB) in 2010. Ground-breaking took place there is the potential for many more neutron instruments exception is SINQ at PSI, which uses a cyclotron that pro- methods for materials research, such as synchrotron X-ray i n 201 4, a n d t o d a y c o n s t r uc t io n i s i n f u l l s w i n g, w it h fi r s t w it h o ut m aj or i n v e s t m e nt i n t h e b a s ic i n f r a s t r uc t u r e. T h e duces a continuous beam. facilities and electron microscopy, accelerator-based neu- science e x pected in 2023 and f ull user operat ion in 2026. ESS source also has a unique time structure, with far longer ESS has a linear accelerator but no accumulator ring, tron sources were established in the 1980s in the US (IPNS The ESS is organised as a European Research Infrastructure pulses than existing pulsed sources, and an innovative and it will thus have far longer proton pulses of 2.86 ms. and LANSCE), Japan (KENS) and the UK (ISIS). Spallation Consortium (ERIC) and at present has 13 member states: has long been hailed as the method with the potential to Czech Republic, Denmark, Estonia, France, Germany, Hun- Fundamental physics at the ESS push through to far greater neutron fluxes, and hence to gary, Italy, Norway, Poland, Spain, Sweden, Switzerland provide a basis for continued growth of neutron science. a nd t he U K. S we de n a nd D e n m a rk a re t he hos t c ou nt r ie s, The ESS will offer a multitude of from 1 to 100 TeV, far beyond observed baryon asymmetry of open up for other kinds of However, after nearly 50 years of operation, and with 10 providing nearly half of the budget for the construction opportunities for fundamental the threshold of direct particle the universe. fundamental physics as well as more modern medium- to high-flux neutron sources phase. Around 70% of the funding from the non-host coun- physics with neutrons, neutrinos production at accelerators, A design study, financed for new perspectives in neutron and potentially other secondary (including five spallation sources) in operation around tries is in the form of in-kind contributions, meaning and resolve the tiny effects of through the European scattering, and muon storage rings. particles from additional the world, the HFR is still the benchmark source for neu- that the countries are delivering components, personnel hadronic weak interactions, Commission’s Horizon 2020 Finally, a proposal has been target stations. While neutron tron-beam research. Of the spallation sources, the most or other support services to the facility rather than cash. enabling quantitative tests of programme, is also under way submitted to ESS concerning brightness and pulse time the non-perturbative limit of for the ESS Neutrino Super coherent neutrino–nucleus powerful (SNS at Oak Ridge National Laboratory in the The unprecedented brightness of ESS neutrons will enable structure are key parameters for US and J-PARC in Japan) have now been in operation for s m a l le r s a m ple s, f a s t e r m e a s u r e m e nt s a n d m or e c o m ple x neutron scattering (the main quantum chromodynamics. Beam (ESSνSB) project. This scattering (CEνNS). The high more than a decade. SNS has reached its design power experiments than what is possible at existing neutron focus of ESS experiments), the Another collaboration ambitious project would see an proton beam power together of 1.4 MW, and J-PARC is planning for tests at 1 MW. At sources. This will inevitably lead to discoveries across total intensity is more important is proposing a two-stage accumulator ring and a separate with the 2 GeV proton energy these power levels the sources are competitive with ILL a wide range of scientific disciplines, from condensed- for many fundamental-physics experiment at the ESS to search neutrino target added to the will provide a 10 times higher for leading-edge research. It has long been known that matter physics, solid-state chemistry and materials experiments. for baryon-number violation. The ESS facility, with the aim of neutrino flux from the spallation the establishment of a new high-flux spallation neutron sciences, to life sciences, medicine and cultural heritage. A cold neutron-beam facility first stage, HIBEAM, will look for sending neutrinos to a large target than previously obtained facility is needed if European science is to avoid a severe A wide range of industrial applications in polymer science for particle physics called ANNI evidence for sterile neutrinos. As underground detector in mid- for CEνNS. Measured for the shortage in access to neutron science in the coming years and engineering are also anticipated, while new avenues is proposed to allow precision a second stage, NNBAR could be Sweden, 400–500 km from the first time by the COHERENT (CERN Courier May/June 2020 p49). i n f u n d a m e nt a l p h y s ic s w i l l b e o p e n e d (s e e “F u n d a m e nt a l measurements of the beta decay, installed at the large beam port, ESS. Here, the neutrinos would collaboration in 2017 at ORNL’s physics at the ESS” panel). hadronic weak interactions and with the purpose to search for be detected at their second Spallation Neutron Source, Spallation Unprecedented performance From the start, the ESS has been driven by the neu- electromagnetic properties of oscillations between neutrons oscillation maximum, giving CEνNS offers a new way to has long been The European Spallation Source (ESS), with a budget of tron-scattering community, with strong involvement from the neutron. ANNI will improve and anti-neutrons. Observing the highest sensitivity for probe the properties of the hailed as the €1.8 billion (2013 figures), is a next-generation high-flux all the leading neutron-science facilities around Europe. the accuracy of measurements of such a transition would show that discovery and/or measurement neutrino including searches method with neutron source that is currently entering its final con- To ma x imise its scient ific potent ial, a reference set of 22 neutron beta decay by an order the baryon number is violated of the leptonic CP-violating for sterile neutrinos and a the potential to struction phase. Fed by a 5 MW proton linac, and fitted instrument concepts was developed from which 15 instru- of magnitude. Experiments will by two units and that matter phase. An accumulator ring neutrino magnetic moment, and push through with the most compact neutron moderator and matched ments covering a wide range of applications were selected probe a broad range of new- containing neutrons is unstable, and the resulting short proton could help reduce the mass of to far greater neutron transport systems, at full power the brightness for c o n s t r uc t io n. T h e s u it e i n c lud e s t h r e e d i ff r a c t o m e t e r s physics models at mass scales potentially shedding light on the pulses needed by ESSνSB would neutrino detectors. neutron fluxes of the ESS neutron beams is predicted to exceed the HFR for h a rd-m at t e r s t r uc t u r e d e t e r m i n at io n, a d i ff r a c t o m e t e r

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FEATURE NEUTRON SCIENCE FEATURE NEUTRON SCIENCE

and construction of the neutron instruments and the struction phase ends in late 2025, ESS is expected to be sample-environment euipment. SS has developed its operating at 2 MW, and all 15 neutron instruments will be own detector and chopper technologies for the neutron in operation or ready for hot-commissioning.

HammarlundSS HammarlundSS instruments, and these are being deployed for a number of The SS has been funded to provide a service to the the instruments currently under construction. In parallel, scientific community for leading-edge research into the SS ata anagement and Software entre, located in materials properties. Every year, up to 3000 researchers openhagen, enmark, is managing the development of from all over the world are epected to carry out around instrument control, data management and visualisation 1000 experiments there. Innovation in the design of the and analysis systems. uring full operation, the SS will accelerator, the target system and its moderators, and in produce scientifi c data at a rate of around 10 PB per year, the key neutron technologies of the neutron instruments while the compleity of the data-handling reuirements neutron guides, detectors and choppers), ensure that for the diff erent instruments and the need for real-time the ESS will establish itself at the vanguard of scientifi c visualisation and processing add additional challenges. discovery and development well into the 21st century. The maor upcoming milestones for the SS proect are Furthermore, provision has been made for the epansion beam-on-target, when fi rst neutrons are produced, and of the SS to provide a platform for leading-edge research uad control i r ui i i e oiioe fi rst-science, when the fi rst neutron-scattering experi- into fundamental physics and as yet unidentifi ed fi elds eee e rooue iie e ue ments take place. According to current schedules, these of research.  Ever ear m i le s t o n e s w i l l b e r e a c h e d i n O c t o b e r 202 2 a n d Ju l y 2023, up to Cabling This characteristic, combined with the 1 H repetition which makes the technology for transporting neutrons respectively. Although beam power at the fi rst-science Further reading io o rate of the SS accelerator, is a key advantage of the SS s o p h i s t ic at e d. T h e g u id e s c o n s i s t o f o p t ic a l l y fl at g l a s s or milestone is expected to be around 100 kW, performance H Andersen e 2020 Nu ru eo Re researchers r o e for studies of condensed matter, because it allows good metal channels coated with many thin alternating layers simulations indicate that the quality of results from fi rst 163402. from all over roo i energy resolution and broad dynamic range. The result is of nickel and titanium, in a seuence designed to enhance eperiments will still have a high impact with the user D Baxter e 2019 arXiv:1911.00762. the world a source with unprecedented fl exibility to be optimised for the critical angle for refl ection. The optical properties of community. The initiation of an open user programme, R aroby e 2018 r 014001. are epected studies from condensed-matter physics and solid-state t h e g u id e s a l lo w for br o a d s p e c t r u m fo c u s i n g t o m a x i m i s e with three or more of the neutron instruments beginning D M ilstead 2015 arX iv:1510.01569. to carr out chemistry, to polymers and the biological sciences with intensity for varying sample sies, typically in the range operation, is expected in 2024, with further instruments T Soldner e 2019 E e Co 10003. around applications to medical research, industrial materials and from a few mm3 to several cm3. b e c om i ng av a i l a ble for op er at ion i n 2025. W he n t he c on- E Wildner e 2016 i Eer 8640493. eperiments cultural heritage. The ESS concept is also of major benefi t for e x per iments in f undamenta l physics, where t he tota l Under construction integrated fl u x is a main fi g ure of merit. onstruction of the SS has been growing in intensity since T h e h i g h n e ut r o n fl u x at E S S i s p o s s i ble b e c a u s e it w i l l b e it began in 2014. The infrastructure part was organised driven by the worlds most powerful particle accelerator, in diff erently compared to other scientifi c large-scale research Cryogenic Components terms of W of beam on target. It will have a proton beam facilities. A partnering collaboration agreement was set up ■ Cryogenic Control & Shut-off Valves of 2.5 mA accelerated to 2 eV, with most of the energy gain w it h t he ma in cont r actor (Skanska), w it h separ ate ag ree- coming from superconducting radio-freuency cavities ments for the design and target cost settled at the beginning ■ Quench Relief Valves cooled to 2 . Together with its long pulse structure, this of diff erent stages of the construction to make it a shared ■ Single & Multi-Line Johnston Couplings gives 5 W average power and 125 W of peak power. For interest to build the facility within budget and schedule. ■ proton energies around a few eV, the neutron production Today, all the accelerator buildings have been handed Check valves and associated products is nearly proportional to the beam power, so the ratio over from the contractor to SS. The ion source, where the b e t w e e n b e a m c u r r e nt a n d b e a m e n e r g y i s t o a l a r g e e x t e nt protons are produced from hydrogen gas, was delivered ■ Focusing on cryogenic temperatures below 100 K the result of a cost optimisation, while the pulse structure from INFN in Catania at the end of 2017. After installation, ■ Optimized design for low operating cost is set by reuirements from neutron science. testing and commissioning to nominal beam parameters, The neutrons are produced by spallation when the the ion source was inaugurated by the Swedish king and the ■ Suitable to operate in high magnetic field and high-energy protons hit the rotating tungsten target. Italian president in November 2018. Since then, the radio- ionizing radiation Please visit us at our website: The 2.5 m-diameter target wheel consists of 3 sectors of freuency uadrupole and other accelerator components ■ Long maintenance intervals and simple www.weka-ag.ch tungsten blocks inside a stainless-steel disk. It is cooled have been put into position in the accelerator tunnel, and the by helium gas, and it rotates at approximately 0.4 Hz, such fi rst prototype cryomodule has been cooled to 2 K. There is service requirements that successive beam pulses hit adacent sectors to allow intense installation activity in the accelerator, where 5 km ■ More than 40 years of experience adeuate heat dissipation and limiting radiation damage. of radio-frequency waveguides are being mounted, 6000 The neutrons enter moderator–refl ector systems above w e ld s o f c o ol i n g-w at e r pi p e s p e r for m e d a n d 25,000 c a ble s or below the target wheel. The unique ESS “butterfl y” being pulled. The target building is under construction, and Liquefaction of gases moderator design consists of interpenetrating vessels of has reached its full height of 31 m. The large target vacuum water and parahydrogen, and allows viewing of either or vessel is due to arrive from in-kind partner SS ilbao in Gas distribution systems The ESS will both vessels from a 120° wide array of beam ports on either Spain later this year, and the target wheel in early 2021. Gas recirculation systems be driven b side. The moderator is only 3 cm high, ensuring the highest The handover of buildings for the neutron instruments WEKA AG · Schuerlistrasse 8 the worlds Hydrogen infrastructure possible brightness. Thus each instrument is fed by an started in September 2019, with the hall of the long instru- CH-8344 Baeretswil · Switzerland most powerful Space infrastructure intense mix of thermal (room temperature) and cold (20 K) ments along with the buildings housing associated labo- Phone +41 43 833 43 43 particle neutrons that is optimised to its scientifi c requirements. ratories and workshops. While basic infrastructure such Plasma & fusion research [email protected] · www.weka-ag.ch accelerator in The neutrons are transported to the instruments through as the neutron bunker and radiation shielding for the terms of of neutron-refl ecting guides that are up to 165 m long. Neutron neutron guides are provided by SS in Lund, uropean beam on target optics are uite challenging, due to the weak cross-sections, partner laboratories are heavily involved in the design

ARCA Flow Group worldwide: 32 CERN COURIER SEPTEMBER/OCTOBER 2020 Competence in valves, pumps & cryogenics

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FEATURE EXOTIC NUCLIDES EXPLORING NUCLEI AT THE LIMITS

Recent studies of exotic nuclides using traps and lasers at CERN’s ISOLDE facility are not only helping researchers understand nuclear structure, e x pla i n Dav id Lun ne y a nd G erda Ne yens, but a l so offer ne w w ays to lo ok for physics b e yond t he St a nda rd Mo del.

nderstanding how the strong interaction binds the ingredients of atomic nuclei is the central quest of COLLAPS U nuclear physics. Since the 1960s CERN’s ISOLDE CRIS facility has been at the forefront of this quest, producing 10 m ISOLTRAP the most extreme nuclear systems for examination of their basic characteristic properties. A chemical element is defined by the number of protons REX-ISOLDE i n it s nuc le u s, w it h t h e nu m b e r o f n e ut r o n s d e fi n i n g it s i so- PS Booster topes. Apart from a few interesting exceptions, all elements 1.4 GeV to HIE-ISOLDE in nature have at least one stable isotope. These form the proton beam so-called valley of stability in the nuclear chart of atomic HRS number versus neutron number (see “Nuclear landscape” fi g u r e). A d d i n g or r e m o v i n g n e ut r o n s d i s t u r b s t h e nuc lear equilibrium and creates isotopes that are generally radio- active; the greater the proton–neutron imbalance, the faster the radioactive decay. Nuclear landscape Chart of nuclides plotted with atomic to MEDICIS The mass of a nucleus reveals its binding energy, which number (Z) versus neutron number (N), with stable species laboratory reflects the interplay of all forces at work within the nucleus indicated by black squares. The colours correspond to the from the strong, weak and electromagnetic interactions. decay half-life, T, which gets shorter with farther ISOLDE from above Laser and trap experiments (red) in the low-energy section Indications of sudden changes in the nuclear shape, when excursions from stability. The black horizontal and of ISOLDE (the REX-ISOLDE post-accelerator and the recent HIE-ISOLDE project adding neutrons, are often revealed first indirectly as a vertical lines correspond to the closed-shell (“magic”) produce radioactive ion beams of higher energies). A target behind that of the sudden change in the mass, and can then be probed in detail configurations, with certain doubly magic nuclei labelled. high-resolution separator (HRS) can be parasitically irradiated and then moved with by measurements of the charge radius and electromagnetic robots to the MEDICIS facility to extract long-lived radioisotopes for medical research. moments. Such diagnosis – performed by ion-trapping and laser-spectroscopy experiments on short-lived (from isons with the liquid drop revealed conspicuous peaks c o n fi g u r at io n s t e n d t o f a v o u r s p h e r ic a l nuc le i, b ut s i n c e t hes now a museum piece at CERN), ISOLDE now lies just off a few milliseconds upwards) isotopes – provides the first at certain so-called “magic” numbers (8, 20, 28, 50, 82, are rather rare, a particularly important feature of nuclei is the beam line to the Proton Synchrotron (PS), receiving vital signs concerning the nature of nuclides with extreme 126), analogous to the high atomic-ionisation potentials their deformation. Inspecting electromagnetic moments 1.4 GeV beam pulses from the PS Booster (see “ISOLDE from proton-to-neutron ratios. of the closed electron-shell noble-gas elements. These d e r i v e d f r o m t h e m e a s u r e d at o m ic h y p e r fi n e s t r uc t u r e a n d t h e a b o v e” fi g u r e). IS OL DE i n f a c t r e c e i v e s t y pic a l l y 50% o fthe Recent mass-spectrometry measurements and findings inspired thenuclear-shell model, developed by change in charge radii derived from its isotopic shift provides pulses in the so-called super-cycle that links the intricate high-precision measurements of nuclear moments and Maria Goeppert-Mayer and Hans Jensen, which is still used detailed information about nuclear shapes and deformation, complex of CERN’s injectors for the LHC. radii at ISOLDE demonstrate the rapid progress being made a s a n i m p or t a nt b e n c h m a r k t o d a y. T h e d i ffe r e n c e w it h t he beautifully complementing mass measurements. The heart of ISOLDE is a cylindrical target that can contain in understanding the stubborn mysteries of the nucleus. atomic system is that the force that governs the nuclear During the past half-century, nuclear science at ISOLDE v a r io u s d i ffe r e nt m at e r i a l s. T h e s t a ble nuc le i i n t h e t a r get ISOLDE’s state-of-the-art laser-spectroscopy tools are also shells is poorly understood. This is because nucleons are has expanded beyond fundamental studies to applications are dissociated by the proton impact and form exotic com- opening an era where molecular radioisotopes can be used themselves composite particles that interact through the involving radioactive tracers in materials (including bio- binations of protons and neutrons. Heating the target (up to as sensitive probes for physics beyond the Standard Model. complex interplay of three fundamental forces, rather materials) and the fabrication of isotopes for medicine (with 2000 degrees) helps these fleeting nuclides to escape into than the single electromagnetic force governing atomic the MEDICIS facility). But the bulk of the ISOLDE physics an ionisation chamber, in which they form 1+ ions that are Tools of the trade structure. The most important question in nuclear physics pr o g r a m m e, a r o u n d 70%, i s s t i l l d e v o t e d t o t h e e luc id at io n electrostatically accelerated to around 50 keV. Isotopes of Progress in understanding the nucleus has gone hand today is to describe these closed shells from fundamental of nuclear structure and the properties of fundamental one particular mass are selected using one of two available in hand with the advancement of new techniques. Mass principles (e.g. the strong interaction between quarks and interactions. These studies are carried out through nuclear mass separators, and subsequently delivered to the exper- measurements of stable nuclei pioneered by Francis Aston g luo n s i n s id e nuc le o n s), t o u n d e r s t a n d w h y s h e l l s t r uc t u r e reactions, by decay spectroscopy, or by measuring the basic iments through more than a dozen beamlines. A similar nearly a century ago revealed a near-constant binding erodes and how new shells arise far from stability. global properties – mass and size – of the most exotic number of permanent experimental setups are operated by energy per nucleon. This pointed to a characteristic satu- A k e y t o r e a c h i n g a d e e p e r u n d e r s t a n d i n g o f nuc le a r s t r uc- species possible. several small international collaborations. Each year, more THE AUTHORS ration of the nuclear force, which underlies the liquid-drop ture is the ability to measure the size and shape of nuclei. t h a n 40 e x p e r i m e nt s a r e p e r for m e d at IS OL DE b y m or e t h a n David Lunney model and led to the semi-empirical mass formula for the This was made possible using the precision technique of laser Half a century of history 500 users. More than 900 users from 26 European and 17 IN2P3/CNRS U. Paris-Saclay and nucleus developed by Bethe and von Weizsäcker. With spectroscopy, which was pioneered with tremendous success The fabrication of extreme nuclear systems requires a driver non-European countries around the world are registered Gerda Neyens the advent of particle accelerators in the 1930s, more at ISOLDE in the late 1970s. While increased binding energy accelerator of considerable energy, and CERN’s expertise as members of the ISOLDE collaboration. CERN and isotopic mass data became available from reactions and i s a t e l l-t a le s i g n o f a d e for m i n g nuc le u s, it g i v e s n o s p e c i fic here has been instrumental. After many years receiving ISOLDE sets the global standard for the production of KU Leuven. decays, bringing new surprises. In particular, compar- information concerning nuclear size or shape. Closed-shell proton beams from a 600 MeV synchrocyclotron (the SC, exotic nuclear species at low energies, producing beams that

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installing a post-accelerator that enables exotic nuclides spanning the entire nuclear chart. The most recent results, CERN-PHOTO-201911-394-15 to be delivered at MeV energies for the study of more subtle published this year by Vladimir Manea (Paris-Saclay), Jonas nuclear reactions, such as Coulomb excitation and transfer. Karthein (Heidelberg) and colleagues, concern the strength Post-accelerated radioactive beams have superior optical of the N = 82 shell closure below the magic (Z = 50) 132Sn quality compared to the GeV beams from fragment separa- from the masses of (Z = 48) 132,130Cd. The team found that the CERN-PHOTO-201911-394-1 tors so that the radioactive beams accelerated in the REX binding energy only two protons below the closed shell was and more recent HIE-ISOLDE superconducting linacs enable much less than what was predicted by global microscopic tailored reactions to reveal novel aspects of nuclear structure. models, stimulating new ab-initio calculations based on ISOLDE’s state-of-the art experimental facilities have a nucleon–nucleon interaction derived from QCD through evolved from more than 50 years of innovation from a ded- c h i r a l e ffe c t i v e-fie ld t h e or y. T h e s e c a lc u l at io n s w e r e pr evi- icated and close-knit community, which is continuously o u s l y a v a i l a ble for l i g ht e r s y s t e m s b ut a r e n o w, for t h e fi r s t expanding and also includes material scientists and bio- time, feasible in the region just south-east of 132Sn, which is chemists. The pioneering experiments concerning binding of particular interest for the rapid neutron-capture process energies, charge radii and moments were all performed creating elements in merging neutron stars. at CERN during the 1970s. This work, spearheaded by the The other iconic doubly magic nucleus 78Ni (Z = 28, N = 50) O r s a y g r o up o f t h e l at e R o b e r t K l a pi s c h, s a w t h e fi r s t u s e o f is not yet available at ISOLDE due to the refractory nature o n-l i n e m a s s s e p a r at io n for t h e id e nt i fic at io n o f m a n y n ew of nickel, which slows its release from the thick target so exotic species, such as 31Na. This particular success led to that it decays on the way out. However, the production of the first precision mass measurements in 1975 that hinted copper – just one proton above – is so good that CERN’s at the surprising disappearance of the N = 20 shell closure, Andree Welker and his colleagues at ISOLTRAP were recently eight neutrons heavier than the stable nucleus 23Na. In col- able to probe the N = 50 shell by measuring the mass of its laboration with atomic physicists at Orsay, Klapisch’s team nuclear neighbour 79C u, fi n d i n g it t o b e c o n s i s t e nt w it h t hat ISOLTRAPpers CERN fellow Maxime Mougeot and PhD student Lukas Nies a l s o p e r for m e d t h e fi r s t l a s e r s p e c t r o s c o p y31 of Na in 1978, of the doubly magic 78Ni nucleus. Masses from large-scale supernova explosions and compact-object mergers, such COLLAPS view (University of Greifswald) tuning ISOLDE’s high-precision mass spectrometer in 2019. revealing the unexpected large size of this exotic isotope. shell-model calculations were in excellent agreement with as the recent neutron-star merger GW170817. Liss Vasquez To reach heavier nuclides, a mass spectrometer with higher the observed copper masses, indicating the preservation Building on pioneering work by COLLAPS, the collinear Rodriguez resolution was required, so the work naturally continued of the N = 50 shell strength but with some deformation laser beamline, CRIS, was constructed at ISOLDE 10 years (Heidelberg), at the expanding ISOLDE facility in the early 1980s. energy creeping in to help. Complementary observables ago by a collaboration between the groups of Manchester Tassos Meanwhile, another pioneering experiment was initiated from laser spectroscopy helped to tell the full story, with and KU Leuven. In CRIS, a bunched atom beam is overlapped Kanellakopoulos by the group of the late Ernst-Wilhelm Otten. After having results on moments and radii from the COLLAPS and the with two or three pulsed laser beams that are resonantly (KU Leuven) and R Stevens/KU Leuven developed the use of optical pumping with spectral lamps more recent Collinear Resonance Ionization Spectroscopy laser-ionised v ia a par ticular hy per fine transition. These Mark Bissell in Mainz to measure charge radii, Otten’s group exploited (CRIS) experiments adding an interesting twist. ions are then deflected from the remaining background (Manchester) at ISOLDE’s first offerings of neutron-deficient Hg isotopes atoms and counted in quasi background-free conditions. ISOLDE’s Collinear and discovered the unique feature of shape-staggering Laser spectroscopy with COLLAPS and CRIS CRIS has dramatically improved the sensitivity of the col- Laser Spectroscopy in 1972. Through continued technical improvements, the Quantum electrodynamics provides its predictions of linear laser spectroscopy method so that beams containing experiment, Mainz group established the collinear laser spectroscopy atomic energy levels mostly by assuming the nucleus is just a few tens of ions per second can now be studied with COLLAPS, in 2019. (COLLAPS) programme at ISOLDE in 1979, with results on point-like a n d i n fi n it e l y h e a v y. Ho w e v e r, t h e nuc le u s i n d ed the same resolution as the optical technique of COLLAPS. barium and ytterbium isotopes. When tunable lasers and has a finite mass as well asnon-zero charge and current Ruben de Groote of KU Leuven and co-workers recently ion traps became available in the early 1980s, the era of distributions, which impact the fine structure. Thus, com- used CRIS to study the moments and charge radii of the high-precision measurements of radii and masses began. plementary to the high-energy scattering experiments copper isotopes up to 78Cu, providing critical information These atomic-physics inventions have revolutionised the used to probe nuclear sizes, the energy levels of orbit- on the wave function and shape of these exotic neighbours, study of isotopes far from stability and the initial experi- ing electrons offer a marvellous probe of the electric and and insight on the doubly magic nature of 78Ni. Both the mental set-ups are still in use today thanks to continuous magnetic properties of the nucleus. This fact is exploited ISOLTRAP and CRIS results provide a consistent picture upgrades and the introduction of new measurement methods. by the elegant technique of laser spectroscopy, a fruitful of fragile equilibrium in 78Ni, where the failing strength Most of these developments have been exported to other marriage of atomic and nuclear physics realised by the of the proton and neutron shell closures is shored up with CRIS collaborators CERN research fellow Ronald Garcia Ruiz with former PhD radioactive beam facilities around the world. COLLAPS collaboration since the late 1970s. COLLAPS uses binding energy brought by slight deformation. students Adam Vernon (Manchester) and Agi Koszorus (KU Leuven), with ISOLDE tunable continuous-wave lasers for high-precision studies These precision measurements in new regions of the group leader Gerda Neyens (standing, centre) at the Collinear Resonance Ionization Mass measurements with ISOLTRAP of exotic nuclear radii and moments, and similar setups nuclear chart bring complementary observables that must Spectroscopy (CRIS) experiment, photographed in 2018. ISOLTRAP is one of the longest established experiments are now running at other facilities, such as Jyvaskyla in be coherently described by global theoretical approaches. at ISOLDE. Installed in 1985 by the group of Hans-Jürgen Finland, TRIUMF in Canada and NSCL-MSU in the US. They have stimulated and guided the development of new are particularly amenable to study using precision lasers K lu g e f r o m M a i n z, it w a s t h e fi r s t P e n n i n g t r apon-line at A recent highlight from COLLAPS, obtained this year by ab-initio results, which now allow the properties of extreme and traps developed for atomic physics. Hence, ISOLDE is a radioactive beam facility, spawning a new era of mass Simon Kaufmann of TU Darmstadt and co-workers, is the nuclear matter to be predicted. While ISOLDE cannot pro- Most of the complementary to higher energy, heavy-ion facilities such spectrometry. The mass is determined from the cyclotron measurement of the charge radius of the exotic, semi-magic duce absolutely all nuclides on the chart (for example, developments as the Radioactive Isotope Beam Factory (RIBF) at RIKEN frequency of the trapped ion, and bringing the technique isotope 68Ni. Such medium-mass exotic nuclei are now in the super-heavy elements), precision tests in other, key have been in Japan, the future Facility for Rare Isotope Beams (FRIB) o n l i n e r e q u i r e d s i g n i fic a nt a n d c o nt i nuo u s d e v e lo p m e nt, r e a c h o f t h e m o d e r n a b -i n it io c h i r a l e ffe c t i v e-fie ld t h e or ie s, r e g io n s pr o v id e c o n fid e n c e i n t h e g lo b a l-m o d e l pr e d ic t ions in the US, and the Facility for Antiproton and Ion Research notably with buffer-gas cooling techniques for ion manip- which reveal a strong correlation between the nuclear charge in regions unreachable by experiment. exported (FAIR/GSI) in Europe. These installations produce even more ulation. Today, ISOLTRAP is composed of four ion traps, radius and its dipole polarisability. With both measured for to other exotic nuclides by fragmenting heavy GeV projectiles on a each of which has a specific function for preparing the ion 68Ni, the data provide a stringent benchmark for theory, and Searches for new physics radioactive thin target, and are more suitable for studying high-energy of interest to be weighed. allow researchers to constrain the point-neutron radius By combining the ISOLDE expertise in radioisotope pro- beam facilities reactions such as breakup and knock-out. Since 2001, ISOLDE Since the first results on caesium, published in 1987, and the neutron skin of 68Ni. The latter, in turn, is related duction with the mass spectrometry feats of ISOLTRAP around the has also driven low-energy nuclear-reaction studies by ISOLTRAP has measured the masses of more than 500 species to the nuclear equation-of-state, which plays a key role in and the laser spectroscopy prowess from the CRIS and world

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LS esonant oniation Laser on Source teas, a Many interesting new-physics opportunities will new era for fundaental physics research has opened open up using diff erent kinds of radioactive molecules up t is centred on the ability of SL to produce tuned for sensitivity to specific syetry violation short-lived radioactive olecules coposed of heavy aspects to test the Standard Model, but also with poten- , pear-shaped nuclei, in which a putative electric dipole tial ipact in nuclear physics for eaple, enhanced ONE HIGGS moment (EDM) would be amplifi ed to off er a sensitive sensitivity to specifi c moments), chemistry and astro- test of tie-reversal and other fundaental syetries physics This will also reuire dedicated eperiental M ole c u le s o f r a d iu m fl uor id e (R a F) a r e pr e d ic t e d t o b e t h e set-ups, cobining lasers with traps The CS collab- ost sensitive probes for such precision studies the heavy oration is preparing these new set-ups, and the ability THREE DISCOVERIES ass and octupole-defored pear shape of soe radiu to produce RaF and other radioactive molecules is isotopes, immersed in the large electric fi eld induced by also under investigation at other facilities, including the molecular RaF environment, makes these molecules TRIUMF and the low-energy branch at FRIB. More than very sensitive probes for syetry-violation e ff e c t s, s uc h 50 years after its breakthrough beginning, ISOLDE as the eistence of an M However, these precision continues to forge new paths both in applied and studies require laser cooling of the RaF molecules, and fundaental research  since all isotopes of a are radioactive, the olecular spectroscopy of RaF was only known theoretically. Frther reai T h i s y e a r, for t h e v e r y fi r s t t i m e, a n IS OL DE c ol l a b or at io n de roote et al. 2020 at. hs. 620 and led by CS collaborator onald arcia ui at CN was 201 hs. ev. 04102 a bl e t o pr o d uc e, id e nt i f y a n d s t ud y t h e s p e c t r o s c o p y o f R a F R F Garcia Ruiz et al. 2020 ature 96 X marks the molecules, containing diff erent long-lived radioisotopes S aufann et al. 2020 hs. ev. Lett. 1202 spot A Higgs of radium. Specifi c Ra isotopes were chosen because of Lunney on behalf of the SLTA Collaboration candidate event A e era for their octupole nature, as revealed by eperients at the 201 . hs. 06400 in the ATLAS fameta - and H-SL accelerators in 201 and 2020 The Manea et al. 2020 hs. ev. Lett. 09202 detector. Four phsis easured olecular ecitation spectral properties pro- Neugart et al. on behalf of CLLAS and muon tracks researh has v id e c l e a r e v id e n c e for a n e ffi c ie nt l a s e r-c o ol i n g s c h e m e, CS Collaborations 201 . hs. 064002 (blue) emerge opee p prov iding t he fi rst step tow ards precision studies. A Welker et al. 201 hs. ev. Lett. 19202 from the interaction point. ATLAS-PHO-EVENTS-2014-015-1 Performing a STOP analysis requires a multiphysics approach... The ATLAS and CMS collaborations have not only discovered a new particle, argues Yosef Nir, but also laid bare the underpinnings of electroweak interactions Structural-thermal-optical performance (STOP) analyses involve temperature calculation, structural a nd uncovered t he fi rst e v idence for a ne w t y p e of f unda ment a l i nter ac t ion– deformation modeling, and ray tracing. To perform one not related to a k now n s y m met r y of nat ure. a STOP analysis, engineers need to account for all of these physics in one high-fidelity simulation. With the he discovery of the Higgs boson in 2012 was the can be related to three distinct classes of measurements: COMSOL® software, you can. culmination of almost five decades of research, the decay of the Higgs boson into two photons, and its The COMSOL Multiphysics® software is used for T beginning in 1964 with the theoretical proposal of production from and decays into the weak force carriers the Brout–Englert–Higgs (BEH) mechanism. This discov- and third-generation fermions, respectively. simulating designs, devices, and processes in all fields e r y w a s m o nu m e nt a l, b ut w a s it s e l f ju s t a b e g i n n i n g, a n d Until 2012, the list of elementary particles could be of engineering, manufacturing, and scientific research. research into the properties of the Higgs boson and the divided into just two broad classes: spin-1/2 matter Visualization of ray trajectories for See how you can apply it to STOP analysis. BEH mechanism, which has unique significance for the particles (fermions) and spin-1 force carriers (vector three field angles in a Petzval lens d y n a m ic s o f t h e St a n d a rd M o d e l, s t r e t c h e s t h e h or i z o n s o f bosons), with a spin-2 force carrier (the graviton) pencilled comsol.blog/STOP-analysis system at nonuniform temperature. e v e n t h e m o s t a m bit io u s f ut u r e-c ol l id e r pr o p o s a l. D e s pit e in by most theorists to mediate the gravitational force. t h i s, t h e AT L A S a n d C M S c ol l a b or at io n s h a v e a l r e a d y m a d e The first jewel in the LHC’s crown is the discovery of an t h r e e m aj or d i s c o v e r ie s r e l at i n g t o t h e H i g g s b o s o n. T h e s e e le m e nt a r y s pi n-0 p a r t ic le – t h e fi r s t a n d o n l y p a r t ic le of a r e t h e j e w e l s i n t h e c r o w n o f L HC r e s e a rc h s o f a r: a n e le- t h i s t y p e t o h a v e b e e n d i s c o v e r e d. T h e q ue s t io n o f t h e s pi n THE AUTHOR mentary spin-zero particle, the mechanism that makes o f t h e H i g g s b o s o n i s i nt r i n s ic a l l y l i n k e d t o t h e d o m i n a nt Yosef Nir t h e w e a k i nt e r a c t io n s h or t r a n g e, a n d t h e m e c h a n i s m t h at d i s c o v e r y m o d e i n 201 2: t h e d e c a y i nt o t w o p h o t o n s. C o n- Weizmann Institute gives the third-generation fermions their masses. They servation laws insist that only a spin-0 or spin-2 particle of Science, Israel.

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the Higgs boson. The field related to this particle is the Vector-boson symmetric BEH field. fusion A candidate Mγ = Mw = Mz = 0 The next question was whether this new particle is event for the

J Ellis/M Neubauer elementary or composite. If the Higgs boson is actually a production of a V (φ) composite spin-0 particle, then there should be a whole Higgs boson in the

s e r ie s o f n e w c o m p o s it e p a r t ic le s w it h d i ffe r e nt q u a nt u m CMS-PHO-EVENTS-2016-007-1 CMS detector in numbers – in particular, spin-1 particles whose mass scale 2016, showing two electroweak is roughly inversely proportional to the distance scale that high-energy phase characterises their internal structure. electrons (green), transition One can test the question of whether the Higgs boson two high-energy Higgs is elementary or composite in three ways. Firstly: indi- muons (red) and boson r e c t l y. T h e v i r t u a l e ffe c t s o f t h e s e h e a v y s pi n-1 p a r t ic les two-high energy would modify the properties of the W and Z bosons. Part jets (yellow cones). of the legacy of the LEP experiments, which operated at The cross section Im (φ) CERN between 1989 and 2000, and the SLD experiment, for this process is in asymmetric which operated in SLAC between 1992 and 1998, is a large agreement with the extra W, Z polarisation Re (φ) Mγ = 0 class of precision measurements of these properties. The hypothesis that the Mw, Mz other two ways are pursued by the LHC experiments: the force carriers of the direct search for the new spin-1 particles, and precision weak interaction Broken symmetry The energy stored in the Higgs field, as a function of its value. If measurements of properties of the Higgs boson itself, gain their masses we look at it from far away, we realise that the Higgs potential is symmetric. However, such as its couplings to electroweak vector-boson pairs, via their a local observer sitting in the rim of the potential, at the vacuum state, will not which would differ if it were composite. No such composite interactions with experience a symmetric world. Thus, the theory is symmetric, but the ground state is excitations have been discovered to date, and the Higgs the everywhere- not. In the Higgs mechanism, the rotational degree of freedom along the rim becomes boson shows no signs of internal structure down to a present BEH field. the longitudinal polarisation of the W and Z bosons, which thereby acquire mass. scale of 10–19 m – some four orders of magnitude smaller than the proton. try is respected by the quantum field theory but not by o n c e t h e g r o u n d s t at e o f t h e u n i v e r s e br e a k s t h e s y m m e t r y, t h e g r o u n d s t at e o f t h e u n i v e r s e (s e e “Br o k e n s y m m e t r y” the latter process is also allowed to occur. A second jewel image). The theory’s predictions will then be different A n a s y m m e t r ic g r o u n d s t at e c o s t s t h e t h e or y n o n e o f it s The electromagnetic and strong interactions are mediated from those that would follow if the ground state were predictive power. The strength of the interaction of the Z by massless mediators – the photon and the gluon. Con- also symmetric. One way in which the symmetry can be boson with the BEH field, measured by the mass it gains sequently, they are long-range, though colour confine- broken is if there is a scalar field that does not vanish in from this interaction, is closely related to the strength ATLAS-PHOTO-2019-016-3 ment – the phenomenon that quarks and gluons cannot t he g round state. This is t he case for t he Higgs potent ial, of the interaction of the Z boson with the Higgs particle, be isolated – renders the long-range effects of the strong which, unlike a purely parabolic potential, does not have measured by the rate at which the Higgs boson decays interaction unobservable. By contrast, weak interactions rotational symmetry around its ground state. The weak- into two Z bosons, or by the rate at which it is produced are mediated by massive mediators – the W and Z bosons force carriers are affected by their interaction with the by Z-boson fusion. This relation is commonly expressed

– with masses of the order of 100 times larger than that BEH field, and this interaction slows them down. Moving as the ratio μZZ* bet ween the measured and the predicted of the proton. As a result, the weak force is exponentially at speeds slower than the speed of light – the consequence rates: if the field related to the newly discovered spin-0 suppressed at distances larger than 10–18 m. of interacting with the BEH field in the ground state – particle is indeed responsible for the mass of the Z boson,

A common feature of the electromagnetic, strong and is equivalent to having non-zero masses, making weak then μZZ* = 1. weak forces is that their mediators are all spin-1. This type i nt e r a c t io n s s h or t r a n g e. T h e s e i n s i g ht s a l s o t r a n s for m e d The rate of the Higgs decay into two Z bosons was first of interaction is very special. By assuming that nature our understanding of the early universe. Following the measured with 5σ significance by the ATLAS and CMS

has certain gauge symmetries, our current quantum field Glashow–Weinberg–Salam breakthrough shortly after the experiments in 2016. Its current value is μZZ* ≈ 1.2 ± 0.1. theories can predict the existence of these types of inter- BEH proposal, the Standard Model presents a universe in The rate at which the Higgs boson decays into a pair of W actions, and many of their features. There are numerous which the ground state transitioned from zero to non-zero bosons was measured in the same year. Its current value of

predictions stemming from these symmetries that have due to the spontaneous breaking of electroweak symmetry μWW* ≈1.2 ± 0.1 a l s o c or r e s p o n d s t o t h e s t r e n g t h o f i nt e r a c t io n been successfully tested by experiments, such as the iden- – a c o s m olo g ic a l e v e nt t h at t o o k pl a c e w he n t he u n i v e r s e t h at w o u ld g i v e t h e W b o s o n it s m a s s. F i n a l l y, t h e e x p e r i- Two photons A 2016 ATLAS candidate for the decay of a Higgs boson into two photons t ic a l c o upl i n g s b e t w e e n g luo n s a n d q u a r k s o f a l l fl a v o u r s, w as about 10 -11 seconds old. m e nt s m e a s u r e d t h e r at e at w h ic h a s i n g le H i g g s b o s o n i s

(green) in the ATLAS detector. Only a spin-0 or spin-2 particle can decay this way. the fact that photons don’t interact with each other, and A BE H fie ld d i ffe r e nt f r o m z e r o i n t h e g r o u n d s t at eofth produced in vector-boson fusion to be μVBF ≈ 1.2 ± 0.2. T hu s, the structure of higher-order corrections, for example universe has important observational and experimental AT L A S a n d C M S h a v e e s t a bl i s h e d a n e w l a w o f n at u r e: t h e can decay into two photons. the running of coupling constants and the anomalous consequences. For example, if the symmetry were unbro- force carriers of the weak interaction gain their masses To decide between the two spin options, a more complex magnetic moment of the electron and the muon. Yet, as ken, a process where a single Higgs particle decays into a via their interactions with the everywhere-present BEH study than just measuring decay rates was needed. The the mass term in the Lagrangian isn’t invariant under pair of Z bosons would be forbidden. But, once the ground fie ld. T h e s t r e n g t h o f t h i s i nt e r a c t io n i s pr e c i s e l y t h eright s pi n o f t h e p a r e nt p a r t ic le a ffe c t s t h e a n g u l a r d i s t r i b ut io ns gauge transformations, gauge symmetry predicts, at least s t at e o f t h e u n i v e r s e br e a k s t h e s y m m e t r y – t h e BE H fie ld s i z e t o l i m it t h e e ffe c t s o f t h e w e a k i nt e r a c t io n t o d i s t ances of the daughter particles of Higgs-boson decays. Stud- naively, that the spin-1 force carriers should be massless. is non-zero – this process is allowed to occur. (Strictly shor ter t han 10 –18 metres. ies began immediately within ATLAS and CMS, showing So, while the symmetries that predict the electromagnetic s p e a k i n g, t h e H i g g s b o s o n c a n n o t d e c a y i nt o t w o Z b o s o n s unambiguously that the newly discovered particle was and strong interactions also explain why their force car- because the sum of their masses is larger than the mass Third generation, third jewel ATLAS and spin-0. The ways in which this particle is produced and riers are massless, the symmetry principle that predicts of the Higgs boson, however, the Higgs boson can decay T h e t h i rd j e w e l i n t h e c r o w n o f t h e L HC i s t h e e x pl a n at io n CMS have the ways in which it decays call for its identification with the weak interaction is challenged by the experimental into a real Z boson and a virtual one that produces a pair for how the tau-lepton and the top and bottom quarks – established the only particle that was predicted by the Standard Model fact that its force carriers are massive. of fermions.) Similarly, the symmetry would not allow a m e m b e r s o f t h e t h i rd, h e a v ie s t fe r m io n f a m i l y – g a i n t h e i r a new law of particle physics that had not been observed by 2012 – This conundrum has a possible solution if a symme- single Higgs-boson production from Z-boson fusion. But, m a s s e s. T h e s a m e e le c t r o w e a k s y m m e t r y t h at pr e d ic t s t h at of nature

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have the strongest couplings to the Higgs boson, and con- extreme fi ne-tuning, perhaps by as many as 32 orders of fi rst-order phase transition could open the door to a new sequently the largest rates of Yukawa interactions with magnitude, between seemingly unrelated constants of mechanism to explain the matter–antimatter imbalance it. The first Yukawa interaction to be measured, with the n at u r e. Va r io u s id e a s o f h o w t o r e s t or e “n at u r a l n e s s”, s uc h in the universe. These deep questions depend on a new significance in both the ATLAS and CMS analyses rising as supersymmetry and Higgs compositeness, have been chapter of Higgs research concerning the self-interaction to 5σ in 2015, concerned the decay of a Higgs boson into suggested, but the LHC experiments have not uncovered of the Higgs boson, which will be carried forward by a

CMS-PHO-EVENTS-2019-002-7 a tau lepton–antilepton pair. The current decay rate is any of the TeV-scale particles predicted by these models future collider.

μτ+τ– ≈ 1.15 ± 0.15, w h ic h, w it h i n pr e s e nt e x p e r i m e nt a l a c c u- and are ruling out ever-increasing swathes of parameter Beyond constituting amazing intellectual and techno- racy, corresponds to the strength of interaction that would space for t he models. logical achievements, the LHC experiments have already give the tau lepton its mass. The rate of Higgs-boson decays The potential of the LHC to discover new facts about made a series of profound discoveries about nature. The into the bottom quark–antiquark pair was measured by nature and the universe is far from saturated. There are at existence of a spin-0 particle whose non-zero force fi eld ATLAS and CMS three years later. The current value is le a s t t w o a d d it io n a l, bi g o p e n q ue s t io n s t h at a r e g u a r a nt e e d is responsible for both the short range of weak interactions – μ bb ≈ 1.04 ± 0.13. W it h i n pr e s e nt e x p e r i m e nt a l a c c u r a c y, t h i s to be answered, at least in par t, by t he LHC ex periments. and, in a distinct way, the masses of spin-1/2 particles, corresponds to the strength of interaction that would give First is the understanding of the mechanism that gives represents three major discoveries. That theorists have the bottom quark its mass. s e c o n d-g e n e r at io n p a r t ic le s – i n p a r t ic u l a r t h e muo n a n d long speculated on these new laws of nature ideas must In the case of the top quark, the Higgs boson has a van- the charm quark – their masses. That may be the same not diminish the signifi cance of establishing them experi- ishingly tiny decay rate into a top–antitop pair, because mechanism as the one that has been shown to give the mentally. These three jewels in the crown of LHC research, the mass of each is individually larger than that of a Higgs third-generation fermions masses, or it may be diff erent the fi rst steps in the exploration of Higgs physics, begin boson, and both would have to be produced virtually. To (for the latest progress, see p7). Second is the question of a trek to some of the most signifi cant open questions in The potentl extract the strength of the Higgs–top interaction, experi- what happened at the electroweak phase transition in the particle physics and cosmology.  o the H to ments instead measure the rate at which this trio of parti- early universe? It may have been a smooth crossover, where cles is produced. The rate of the production of a Higgs boson the value of the BEH fi eld changed from zero to its present Frther redn dscoer new together with a top quark–antiquark pair was measured v a lue c o nt i nuo u s l y a n d u n i for m l y i n s p a c e, a s pr e d ic t e d b y ATLAS Collab. 2012 hys. Lett. 1. cts ot by the ATLAS and CMS experiments in 2018. The current the combination of the Standard Model of particle physics CMS Collab. 2012 hys. Lett. 30. ntre nd

– value is μtth ≈ 1.3 ± 0.2. Within present experimental accu- and the Big Bang model, or it may have been a fi rst-order F Englert and R Brout 1964 hys. e. Lett. 321. the nerse racy, this value corresponds to the strength of interaction phase transition, where bubbles with a fi nite value of the B Heinemann and Y Nir 2019 hys. sp. 920. s r rom that would give the top quark its mass. (The remaining BEH fi eld nucleated within the surrounding plasma. A P W Higgs 1964 hys. e. Lett. 508. strted third-generation particle, a neutrino, is at least 12 orders Yukawa the weak-force carriers should be massless also predicts of magnitude lighter than the top quark, and is suspected evidence that all 12 spin-1/2 matter particles known to us should to derive its mass via a different mechanism, which is The LHC also be massless. Experiments have shown, however, that unlikely to be tested experimentally in the near future.) uncovered the all the matter particles are massive, with the one possi- ATLAS and CMS have therefore discovered a new fact first Yukawa ble exception of the lightest neutrino. The fact that this about nature: the third-generation charged particles – interactions symmetry is broken in the ground state of the universe the tau lepton, the bottom quark and the top quark – also – spin-0 mediated also opens the door to the possibility that matter particles gain their masses via their interaction with the every- forces that are not gain masses. But via what mechanism? For the ground where-present BEH field. This is also the discovery of predicted by state of the BEH field to slow down the fermions as well the new and rather special Yukawa interactions among symmetry as the W and Z bosons, a new type of interaction has to elementary particles, which are mediated by a spin-0 force principles. This exist: an interaction with a spin-0 mediator – the Higgs carrier, the Higgs boson. 2017 event in CMS boson itself. Discovering a Higgs-boson decay into a pair is evidence for the of fermions would mean the discovery of this new type of The path forward production of a spin-0 m e d i at e d i nt e r a c t io n, w h ic h w a s fi r s t pr o p o s e d i n Answering questions about nature’s fundamental workings Higgs boson in a different conte x t by Hidek i Yukaw a in t he 1930s. almost always leads to new questions. The discovery of the association with a Yukawa interactions are fundamentally different from Higgs boson has already been the source of at least two. pair of top quarks. the interactions through which the W and Z bosons get Firstly, the value of the Higgs boson’s mass suggests the An electron is their mass because they are not deduced from a symmetry possibility that our universe is likely in an unstable state. shown in green, principle. Another difference, in contrast not only to weak, In the extremely distant future, a transition to an entirely a muon in red, but also to strong and electromagnetic interactions, is different universe with a different ground state could occur. and missing that the interaction strength is not quantised. However, Should this remain true as precision improves, not only is energy in pink. the strength of the interaction of a matter particle with there nothing special about Earth, nor the solar system, the BEH field, measured by the mass it gains from this nor even Milky Way galaxy, but the fundamental struc- interaction, is still closely related to the strength of the ture of the universe is itself only temporary. What’s more, Yu k a w a i nt e r a c t io n o f t h at m at t e r p a r t ic le w it h t h e H i g g s the lightness of the mass of the Higgs boson compared boson, measured by the rate at which the Higgs boson to both the Planck scale (above which quantum-grav- d e c a y s i nt o t w o s uc h fe r m io n s. O n c e a g a i n, i f t h e fie ld t h at ity effects become significant) and the “seesaw scale” gives the matter particles their masses is indeed the one (b e lo w w h ic h n e w p a r t ic le s, b e yo n d t h o s e o f t h e St a n d a rd related to the newly discovered spin-0 particle, then the M o d e l, a r e pr e d ic t e d t o e x i s t), p o s e s a c h a l le n g e t o t h e b a s ic measured decay rate of the Higgs particle to fermion pairs framework that we use to formulate the laws of nature. In 11 www.lakeshore.com should give a value of unity to the corresponding μ-ratio. quantum field theory, cancellations between tree-level The three heaviest spin-1/2 particles – the top quark, and higher order loop-diagram contributions to the mass the bottom quark and the tau lepton – are expected to of the Standard Model Higgs boson are huge, and require

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

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• Crystal planes oriented to ±2 arc-sec CERN inherent phenomena of quantum • High vacuum compatibility, no outgassing mechanics such as superposition and • Uniform performance from unit to unit entanglement, have the potential to trans- for m s c ie n c e a n d s o c i e t y o v e r t h e n e x t fi v e to 10 years. This is sometimes described as the second quantum revolution, following t h e fi r s t t h a t i n c lu d e d t h e i nt r o d u c t i o nof devices such as lasers and transistors over QT inroads CERN’s AEGIS experiment is able to explore the multi-particle entangled Alberto Di Meglio the past half century. Quantum technol- nature of photons from positronium annihilation, and is one of several examples of is coordinator of the ogies (QTs) require resources that are not existing CERN research with relevance to quantum technologies. To learn more, visit www.inradoptics.com/products/x-ray-imaging-crystals CERN quantum mainstream today. During the past couple technology of years, dedicated support for R&D in QTs second is quantum sensing and metrol- tion with leading experts, universities initiative and head has become part of national and inter- ogy, which exploits the high sensitivity and industry, and identify mechanisms of CERN openlab. national research agendas, with several of coherent quantum systems to design for knowledge sharing within the CERN major initiatives underway worldwide. new classes of precision detectors and Member States, the high-energy phys- Meet us at IPAC2020: 10th - 15th of May 2020 in Caen, FRA The time had come for CERN to engage measurement devices. The third, quantum ic s c om mu n it y, ot he r s c ie nt i fic re s e a rc h more formally with such activities. communication, whereby single or entan- communities and society at large. Grad- Following a first workshop on quan- gled photons and their quantum states are uate students will be selected in time for HIGH VOLTAGE tum computing in high-energy physics used to implement secure communication t he first projects to beg in in early 2021. organised by CERN openlab in November protocols across fibre-optic networks, or POWER SUPPLIES 2018 (CERN Courier December 2018 p41), quantum memory devices able to store Joint initiatives best-effort initiatives, events and joint quantum states. The fourth domain is A number of joint collaborations are MAGNET pilot projects have been set up at CERN to quantum theory, simulation and infor- already being created across the high- explore the interest of the community in mation processing, where well-controlled energy physics community and CERN POWER SUPPLIES quantum technologies (in particular quan- quantum systems are used to simulate is involved in several pilot investiga- tum computing), as well as possible syn- or reproduce the behaviour of differ- tion projects with leading academic and HIGH CURRENT e r g ie s w it h o t he r re s e a rc h fie ld s. I n Ju n e, ent, less accessible, many-body quan- research centres. On the industry side, CERN management announced the CERN tum phenomena, and relations between through CERN openlab, CERN is already POWER SUPPLIES quantum technology initiative. CERN is in quantum phenomena and gravitation collaborating on quantum-related tech- the unique position of having in one place can be explored – a topic at the heart of n ol o g i e s w it h C Q C, G o o g l e, I B M a n d I nt e l. HIGH PRECISION the diverse set of skills and technologies CERN’s theoretical research programme. The CERN quantum technology initiative – including software, computing and data There is much overlap between these four will continue to forge links with industry POWER SUPPLIES science, theory, sensors, cryogenics, elec- domains, for example quantum sensors and collaborate with the main national tronics and material science – necessary a n d n e t w or k s c a n b e br o u g ht t o g e t h e r t o quantum initiatives worldwide. for a mu lt id i s c i pl i n a r y e n d e a v o u r l i k e Q T. create potentially very precise, large-scale By taking part in this rapidly growing BASIC RESEARCH CERN also has compelling use cases that detector systems. field, CERN not only has much to offer, AT THE HIGHEST LEVEL create ideal conditions to compare classic Over the next three years, the quan- b ut a l s o s t a n d s t o b e n e fit d i r e c t l y f r o m it. Quantum and quantum approaches to certain appli- tum technology initiative will assess For example, QTs have strong potential Heinzinger has played a role in research for a very long time technologies c a t i o n s, a n d h a s a r i c h n e t w or k o f a c a d e m i c the potential impact of QTs on CERN and in supporting the design of new sophis- thanks to its expertise and passion. In addition to the European have the a n d i n d u s t r y r e l a t i o n s w or k i n g i n u n i q u e high-energy physics on the timescale of ticated types of detectors, or in tackling CERN facility in Geneva, companies, universities, colleges and potential to collaborations such as CERN openlab. the HL-LHC and beyond. After establish- the computing workloads of the physics state institutions are investing in research. Whether it be testing transform Today, QT is organised into four main ing governance and operational instru- experiments more efficiently. The CERN and measuring equipment, accelerator technology or HV pow- domains. One is computing, where quan- ments, the initiative will work to define quantum technology initiative, by helping science and tum phenomena such as superposition concrete R&D objectives in the four main structure and coordinate activities with our

er supplies for particle detectors: High-specification technical Rosenheim (Germany) 4 I 83026 GmbH I Anton-Jakob-Str. Heinzinger electronic I www.heinzinger.com 2458 0 I email: info @heinzinger.de +49 8031 P: society over equipment from Heinzinger helps to produce reliable and resilient are used to speed up certain classes of QT areas by the end of this year. It will community and the many international results in laboratories and testing centers all over the world. t he ne x t five computational problems beyond the lim- also develop an international education public and private initiatives, is a vital step to 10 years its achievable with classical systems. A and training programme in collabora- to prepare for this exciting future.

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Lessons in leadership

The best leaders are those who don’t want to be leaders per se, says experimentalist Ian Shipsey, who started out in kaon physics before taking up prominent positions in CLEO, the LHC experiments, the Vera Rubin Observatory and, most recently, quantum technologies.

What drew you to particle physics? Oxford of University of the CMS quarkonia working group. Ever since I was an undergraduate, The atmosphere at CERN was electric I wanted to know why there was a and analysing those first LHC data was lot more matter in the universe than one of the most exciting moments of antimatter – an asymmetry that my career. CMS has been a wonderful, permits us to exist. My thesis was supportive environment in which to on CP violation in the kaon system learn and grow as a physicist. Then, as part of the NA31 experiment at in 2013, I took up a position at Oxford, ,, ,.... CERN. I had the opportunity to help which is a founding member of "' build a muon detector and we found ATLAS. I joined ATLAS in 2016 and t he first ev idence t hat mat ter and brought with me experience with ant imat ter behave different ly as t hey muons, silicon and data analysis. -2 -1 0 1 2 3 Input Power {dBm) disintegrate; subsequently established It’s very exciting to be part of ATLAS with greater significance by NA48 and the collaboration has been very and by KTeV at Fermilab. NA31 was a welcoming. wonderfully nurturing environment with many brilliant physicists. Like What attracted you to work on the many European students at that Vera C Rubin Observatory? time, I was strongly encouraged to The Rubin Observatory is a ground- head to the US for post-PhD finishing based 8.4 m, 10 square-degree field- school and decided to join the CLEO of-view telescope that will see more experiment at the Cornell Electron of the universe at optical wavelengths Storage Ring (CESR) – for two reasons: in its first mont h of operat ion t han first, CLEO studied beauty quarks, all previous telescopes combined. Expand your reach and engagement The benefits of choosing a digital-first publisher which were expected to have much Scheduled to start in late 2022, (but larger CP violating effects than kaons; delayed by COVID-19 situation), Publish your textbook, monograph, review or handbook and second because I had fallen in love Positive outlook Ian Shipsey is head of the physics department it will revolutionise astronomical with IOP ebooks and benefit from circulation to peers with a student (now my wife, Daniela at the University of Oxford. observations by conducting the Legacy at targeted institutions and conferences, as well as Bortoletto) working on CLEO whom I Survey of Space and Time – an optical timely marketing campaigns, member newsletters and had met at CERN. CLEO was another this application, but then, in 1993, the survey of faint astronomical objects astonishingly nurturing environment. SSC was cancelled and a lot of people across the entire sky every three much more. I joined Purdue University as an went towards the LHC. I was invited to nights, enabling precision dark-energy Rapid publication Multimedia Full-color print assistant professor just a couple of join ATLAS due to my MPGD expertise, measurements, studies of dark matter We welcome proposals in all areas of physical sciences, times content copies years after arriving in the US. but I decided to focus on CLEO and the and opening a movie-like window on applications, education, methods, computational tools surety of great physics results, which objects that change or move on rapid and techniques. How did you make the transition to were needed to win tenure. Shortly timescales. I have been a member the LHC experiments? afterwards, with CLEO colleagues, I since 2007, when I was asked to help Choose the right publisher for you While I’d help build the CLEO muon received a large grant to build a silicon out in the pitch to the US Department spectrometer and worked on analyses, vertex detector for CLEO III, which was of Energy (DOE) to participate in the If you are interested in being part of this rapidly expanding there was an expectation to work commissioned successfully in 2000. project. The scope of particle physics book series, we’d like to hear from you. Submit a summary on a far-future project as well. I set Almost immediately I and my group NA31 was a was broadening and the US national of your proposal to [email protected], and No Digital Rights e-reader A dedicated, up a fledgling research group to were invited to join CMS to help build wonderfully laboratories engaged in particle Management compatibility hands-on editor develop micro pattern gas detectors the forward silicon pixel detector. physics had sig nificant capabilit ies, include a current biography and contact details. nurturing (MPGDs) for the SDC collaboration at After the pixel detector was installed I environment for example in silicon detector the Superconducting Super Collider was asked to co-lead the LHC Physics construction, that were an excellent (SSC). Fairly quickly we concluded that Center (LPC) at Fermilab. Then the with many match to the technical challenges of silicon microstrip and pixel detectors LHC began operation and I moved to brilliant building the Rubin Observatory’s 3 were a better technology choice for CERN, serving also as the co-convener physicists Gigapixel CCD camera. We met healthy

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OPINION INTERVIEW OPINION INTERVIEW

scepticism at DOE, given the completely University Cornell What is driving current interest in new detection technologies. Related Drell, who is now Provost at Stan ford, It taught me to be posit ive and to unknown nature of dark energy. From a quantum technologies? fields t hat w ill also be impacted by w as essent ial in ta k ing it to t he ne x t believe in mysel f and in li fe. Belief science perspective we found two lines The birth of quantum mechanics quant um sensing are g rav itat ional level because she suggested she is impor tant in ever y t hing we do of argument were useful. First, the job nearly 100 years ago has led to the w ave cosmolog y, ast rophysics and w rite dow n what people said. Ot hers bot h as indiv iduals and as scient ific of particle physicists is to understand information and communication f undamental tests of quant um quic k ly followed suit, allow ing me to inst it ut ions. Believ ing a 100 km the fundamental nature of energy, technology that is now central to mec hanics. Quant um comput ing, communicate instant ly for t he first circumference future circular matter, space and time, and in so doing modern civilisation – sometimes along w it h t radit ional high- t ime. In 2003 I had a coc hlear implant collider is possible is a prerequisite for to understand the origin, evolution referred to as the first quantum performance computing and advances installed. When I couldn’t hear, I w as it to happen – and I believe! and fate of the universe. Second, by revolution. But none of the existing in mac hine lear ning and ar t ificial t reated completely li ke ever yone else. analog y to t he Higgs field and Higgs technologies use any of the iconic intelligence, w ill be absolutely I didn’t sense any discriminat ion. Interview by Matthew Chalmers editor. boson, the cosmological observations characteristics of quantum mechanics necessar y to analyse HL-LHC data. are consistent with dark energy being such as the uncertainty principle, Quant um communicat ion is also key a scalar field, whic h i f cor rect implies superposition states, macroscopic to this. an associated scalar particle. The pitch quantum interference, or two-particle was successful and the DOE approved quantum entanglement. Second- What can high-energy physics funding for the construction of the CCD generation quantum technology that contribute to quantum technologies? camera. Soon after arriving at Oxford exploits these phenomena is just Bringing the unique resources I was asked to help make the case for coming online. Most well-known is and e x per t ise of t he par t icle- UK participation in the project. Like quantum computing, which exhibits physics communit y to bear on t he everyone else in the Rubin Observatory extraordinary capabilities and is development of quantum sensors will community, I am eagerly anticipating steadily entering the scientific lead to rapid technology advances. For first data. and corporate marketplaces. example, Fermilab develop high-Q Sense of beauty Shipsey first rose to management positions in As humankind harnesses the superconducting RF cavities. Some Did you plan to enter scientific the CLEO experiment at the Cornell Electron Storage Ring. characteristics of quantum mechanics searches for ultra-light dark matter management? and gains mastery over them we use these. Additionally, they provide I had no plan to be involved in organised. Our leaders are not generals will witness the second quantum a high-coherence environment for scientific management of any kind! or CEOs, but colleagues called to serve revolution that will transform our qubits used as detectors, isolating At around the time I joined CMS a few for a time before returning to the rank society in as profound a way as the them from a noisy environment. of us had been developing the idea and file. first quantum revolution did. It is CERN, as the premier particle-physics to transform CLEO and CESR into a no different to the transistor in the laboratory in the world, will also machine that would preferentially How did you wind up leading the 1950s: if people told you back then find ways to contribute. In quantum produce charm quarks rather than quantum-sensor programme for that transistors could change your sensing, CERN can help with its deep beauty quarks to test ultra-precise the UK’s Quantum Technologies life, no one would have believed shafts potentially suited to atom lattice-QCD predictions used by initiative? you; now we have a billion of them inter feromet r y. Several fledgling B-physics experiments to extract CKM In 2017 the DOE invited me and a in a smart phone. So we can start to efforts exist, and collaboration matrix elements. When getting the colleague to articulate the case for harness (crudely) phenomena such can be enhanced by structures and idea funded I became the public face of quantum sensing in particle physics. as entanglement and the promise is funding and a world lab that brings the experiment, and around that time We co-organised a workshop bringing that over the next 20–30 years we can people together from a wide range I was also elected by the collaboration together many disparate communities put this technology in your phone. We of disciplines. to be co-spokesperson. As CLEO from which an influential whitepaper can’t even begin to think what that entered its twilight phase, the success (arXiv.org:1803.11306) emerged would enable because it’s beyond our How has becoming profoundly deaf at of the LPC led to me being elected and contributed to the creation imagination. Think quantum internet, the age of 29 affected your career? chairperson of the CMS collaboration of a new DOE-funded quantum- quantum liquid crystals and quantum I w as eight-mont hs mar ried and board in 2012. I was also elected chair sensing programme in 2018. I then artificial neural networks. had just been appointed assistant of the APS division of particles and conducted a similar activity in the professor when suddenly I fell ver y fields. Moving back to Europe I was UK at the invitation of the Science What do quantum technologies offer ill and w as diag nosed w it h a rare elected head of the Oxford particle- and Technology Facilities Council high-energy physics? cancer of t he blood and bone mar row physics group in 2014 and I was elected (STFC), bringing together the particle- A revolution in the theory and called acute myeloid leukemia, whic h head of the physics department in physics and particle-astrophysics tools of quantum mechanics has few people at t hat t ime sur v ived. I 2018. Throughout this entire period, community with the atomic, molecular produced new sensitive measurement underwent intense chemotherapy, leadership roles have occupied about and optical and condensed-matter techniques that allow measurements whic h wea kened my immune system 50% of my working day, which has communities to form a Quantum to be made near the intrinsic noise and caused me to fall into a coma. meant that to get research done I tend Our leaders Sensing for Fundamental Physics limits imposed by the uncertainty The hair cells in my coc hlea were to be connected to my laptop until the are not (QSFP) consortium, targeting principle, as well as enabling new destroyed as a result of the antibiotics early hours on most days. Fortunately, strategic UK government funding to capabilities in sensitivity, resolution t hat were medically necessar y to generals or five to six hours of sleep each night support interdisciplinary research. and robustness. This can now be keep me sa fe unt il my ow n immune is sufficient. I have also been blessed CEOs, but STFC announced around £40M for harnessed to accelerate searches for system had ret ur ned, rendering me with wonderful colleagues, students, colleagues the programme in September 2019 new physics including, for example, per manent ly dea f. I w as taught to lip postdocs, and administrative support. called to and a call for proposals led to the dark matter, hidden dark sectors read but I didn’t lear n to sig n because In my opinion the best leaders are serve for a identification of seven projects and electric dipole moments. For in general physics is not a culture those people who don’t want to be time before for funding, for which an official decades, one way that we’ve hunted where it is used. I also didn’t develop leaders per se, and I think I was announcement is imminent. I am a for dark-matter particles is with large dea f spea k. However, w it hout hearing selected for this reason. Particle returning to member of one of them: AION detectors via nuclear recoils, but the it w as a slow process to communicate. physics is a team effort, quite distinct the rank (the Atom Interferometer allowable mass ranges from 10-22 eV There was immense support from to the way an army or a corporation is a nd fi le Observatory Network). to the Planck scale, which demands my colleag ues at Cor nell and Persis

50 CERN COURIER SEPTEMBER/OCTOBER 2020 CERN COURIER SEPTEMBER/OCTOBER 2020 51

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Find the information you need from IOP Publishing’s world-leading journals and award-winning books programme, along with conference proceedings and science news from Physics World. iopscience.org/particle-and-nuclear-physics

CERNCOURIER.COM OPINION Particle and REVIEWS nuclear physics

Find the information you need from IOP An intuitive approach to teaching

Publishing’s world-leading journals and / ATLAS-PHO-COLLAB-2012-013-1 M Rayner award-winning books programme, along with Elementary Particle Physics: conference proceedings and science news An Intuitive Introduction By Andrew Larkoski from Physics World. Cambridge University Press

Publish with us This elementary textbook, suitable for We offer a range of publishing options to suit your either advanced undergraduate or intro- ductory postgraduate courses, is a gem. needs, ensuring that your work gets the attention that Its author, Andrew Larkoski, is a phe- it deserves. nomenologist with expertise in QCD, and a visiting professor at Reed College. It is worth mentioning that Reed College is iopscience.org/particle-and-nuclear-physics a l s o h o m e t o D a v i d J G r i ffit h s, w h o i s t he author of several successful textbooks, including his well-known Introduction to Elementary Particles (Wiley, 2nd edi- tion, 2008). Larkoski’s book has a similar scope to Griffiths’ and certainly lives up to its legacy. Larkoski begins with an introduction Brain food A particularly attractive feature of Larkoski’s writing is his use of intuitive and conceptual We are in the loop to special relativity and the standard discussions, writes our reviewer. BrillianSe X-ray Camera preliminaries to particle physics, such 16-Megapixel, micron-scale spatial resolution, as the Dirac equation, Fermi’s golden other projects. The book’s modernity is Martin (Quarks and Leptons, Wiley, and high energy direct conversion imaging rule and a very accessible introduction also evident through mentions through- 1984), and other popular textbooks to group theory. The book also features a out the text on the latest results in dark that currently form the backbone of superb 30-page chapter on experimen- matter and neutrino physics, and a dis- many university courses, use the Dirac High Energy Micron-Scale Pixel Direct Conversion tal concepts and statistics – an excel- cussion on how the Higgs boson discov- basis. As a result, both equations and lent resource for any student starting ery was made. Fey nman rules look different, and care BrillianSe delivers a unique combination of high spatial a particle-physics project for the first A particularly attractive feature of will be required when multiple text- resolution and detection efficiency for hard X-rays time. The main menu follows: matrix Larkoski’s writing is his use of intuitive books are used in the same course. In element and cross-section calculations and conceptual discussions: dimensional general, Larkoski is closer to Thomson 16-megapixel sensor format for QED, QCD and weak interactions. The analysis is used often in calculations to and Griffiths, as it does not include the 4096 x 4096 pixels at 2 fps book includes a nice introduction to elec- get an idea of what we expect; analogies wide range of calculations of Halzen and troweak unification, the basics of flavour are drawn between Feynman diagrams Martin, which is slightly more advanced. physics, neutrino oscillations, and an and electrical circuits; connections Larkoski’s new book will certainly 8 µm pixel pitch accessible discussion on parton evolution between space curvature and quantum find its way among the most popular 50% MTF at ½ Nyquist and 63 keV and jets. The latter will be particularly chromodynamics are pointed out, just to particle-physics textbooks. Its clear and Patented Custom CMOS Design Flow Monitoring by ELETTA. useful for students of LHC physics. The mention some of the very many examples intuitive presentation will doubtlessly High detection efficiency book closes with an insightful chapter you can find in t he book. deepen the understanding of students a-Se direct conversion Extreme reliability on your on open problems in particle physics. One point that the lecturers should be who read it, and inspire lecturers to a 43 eV cost per electron-hole pair A very nice collection of unsolved exer- aware of is that Larkoski employs the more conceptual approach to teaching. at 63 keV cooling systems. cises will serve as an invaluable resource Weyl basis of Dirac γ-matrices, whereas Safety on critical applications. for lecturers. Many refer to processes Griffiths, Thomson (Modern Particle Nikolaos Rompotis University Large full well capacity currently being studied at the LHC and Physics, Cambridge, 2013), Halzen and of Liverpool. Resolving power 877,000 electrons Supplier for more than Accelerator Radiation Physics Don Cossairt and Matthew Quinn’s A compact and tutes a compact and comprehensive 40 years at CERN and other for Personnel and recently published book summarises comprehensive compendium for radiation-protection Environmental Protection both basic concepts of the propagation professionals working at accelerators. www.kaimaging.com • [email protected] compendium particle accelerators. By J Donald Cossairt and of particles through matter and funda- The book’s content originates in a course +1 226-215-9897 for radiation- Matthew Quinn mental aspects of protecting person- taught by Cossairt, a longstanding and www.eletta.com nel and environments against prompt protection recently retired radiation expert at CRC Press s [email protected] radiation and radioactivity. It consti- professionals Fermilab, at numerous sessions

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OPINION REVIEWS

of the US Particle Accelerator School rules-of-thumb. Graphs of represent- time when the material upon which the (USPAS) since the early 1990s. It is also ative particle spectra and yields serve book is based was written. For exam- available as a Fermilab report, which for back-of-the-envelope calculations ple, the rules-of-thumb presented in has stood the test of time as one of the and describe the fundamental charac- the text are nowadays mostly used for standard health-physics handbooks for terist ics of radiat ion fi elds. cross-checking results obtained with accelerator facilities for more than 20 much more powerful and user-friendly years. Quinn, the book’s co-author, is the Practical uestions Monte Carlo transport programs. laboratory’s radiation-physics depart- The second half of the book deals with The reader will not, however, find ment manager. the practical questions encountered information on the use and limitations The book begins with a short overview in everyday radiation-protection of such codes. For example, the chapter of the physical and radiological quan- assessments, such as the selection of on aspects of radiation dose attenua- tities relevant for radiation-protection Recirc-cryo-IOP 8/9/18the 5:40 most PM effi Page cient 1 shielding material tion through passage ways and ducts as assessments, and briefly sketches for a given radiation fi eld, the energy well as environmental doses due to the mechanisms for energy loss and spectra to be expected outside of the prompt radiation (skyshine) gives scattering during particle transport shielding, where personnel might be only analytical formulae, while assess- in matter. The introductory part con- present, and lists of the radiologically ments are nowadays more readily and cludes with chapters on the Boltz- relevant nuclides that are typically accurately obtained with Monte Carlo mann equation, which in this context produced around accelerators. It also simulations. There is a risk, however, describes the transport of particles provides a compact introduction to that such codes will be treated as a through matter, and its solution using activation at accelerators. The final black box, and their results blindly Monte Carlo methods. The follow- chapter gives a comprehensive overview believed. In this regard, the book gives ing chapters illustrate the radiation of the radiation-protection instrumen- many tools necessary for obtain- fields that are induced by the inter- tation traditionally used at accelerators, ing rough but valuable estimates for actions of electron, hadron and ion helping the reader to select the most setting up simulations and cross- beams with beamline components. appropriate detector for a given radi- checking results. The tools described in these chapters ation fi eld. are parametrised equations and handy Some topics have evolved since the Stefan Roesler E.

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PEOPLE CAREERS PEOPLE A lumni speciAl Markus Pflitsch almost word for word to the position she where he was tasked with developing tools to CAREERS Founder and CEO of Terra Quantum held at the time, but in a completely different enable customers to enter their data online Markus joined CERN as sector: CERN’s cooling and ventilation and obtain the best tariff. “Nowadays, this ALUMNI SPECIAL a summer student in group. “So, why not?” she thought. “At is quite commonplace, but at the time such 1996, working on the CERN, I discovered the importance of being software did not exist,” he says. Alessandro OPAL experiment at LEP. open to different paths and different ways is now general manager of Diagramma, Eager to tackle other of thinking.” In 2004, five years in to her which is developing AI algorithms to professional challenges, position and with a “reasonable prospect” increase the efficiency of its products. He Growing the high-energy network upon graduating he but no confirmation of a permanent contract, values his particle-physics experience accepted an internship she began to think about the future. “I more than ever: “It wasn’t enough to know with the Boston Consulting decided that it would be either CERN or the physics and think logically, I also had While most CERN alumni remain in research, stories from those who choose other professional Group. “On my first day I a sister international organisation that to think differently, laterally one could avenues demonstrate the high value placed by employers on skills acquired in high-energy physics. found myself surrounded by Harvard MBAs in would also give me the opportunity to take say. I learnt how to solve problems using sleek suits, wondering what we would have ownership of my work and shape it.” She an innovative approach. Having worked at

C Smith/CERN in common,” he says. “I think there are two sent a single application for an open position CERN, I know how multi-talented these very clear reasons why companies are so keen in the launcher department of the European people are and I am very keen to employ such to employ people from CERN. Number one, Space Agency (ESA), and was successful. talent in my company.” you develop extremely strong and structured “I didn’t know of course if I was making a analytical skills, and this is coupled with the good choice and I was afraid of closing Stephen Turner second reason: a CERN experience provides doors. But, my interest was already piqued Electrical/electronic engineer at STFC you with a deep passion to perform.” by the launchers!” Carmen joined ESA at Following a Master’s In 2001 Markus returned to Germany as an exciting time, when Ariane 5 was degree in electrical and director of corporate development with preparing for flight. She trained on the electronic engineering at Thumbs up Deutsche Bank. He enjoyed a meteoric job, largely thanks to a “work-meeting” the University of Plymouth Barbara Warmbein, rise in the world of finance, moving to technique that allows small teams to be in the UK, Stephen started Miguel Anjo, Paulo UniCredit/HypoVereinsbank as managing fast and share knowledge and experience working for the UK Science Pinto, Marzena director in 2005, and then to Landesbank effectively on a specific objective, and is and Technology Facilities Lapka, Hugo França, Baden-Württemberg (LBBW), first as head currently working on the Ariane 6 design Council (STFC), where he Michael Eppard, of corporate development and subsequently project. “I do not hesitate to change sought a three-month Ana Sousa e Silva CEO of LBBW Immobilien GmbH. The global positions at ESA, taking into account my placement as part of their and Pedro Alexandre financial crisis in 2009 led him to pursue a technical interests, without giving too graduate scheme. Having contacted an Loureiro at the more entrepreneurial role, and he moved much importance to opportunities for STFC scientist with CERN links “who knew CERN Alumni “First into marketing, becoming CFO and managing hierarchical promotion.” someone, who also knew someone” at Collisions” event in director of Avantgarde. After six successful CERN – a scientist supporting the Beamline February 2018. years he sought some major life changes, Alessandro Pasta for Schools competition – Stephen secured taking three months off and discovering a General manager at Diagramma his placement in the autumn of 2017. As a passion for hiking. In 2018 Markus founded In 1987, then 18 year-old member of the support-scientists team, his Terra Quantum to develop quantum Alessandro was selected to role was to help characterise the detectors computing. He describes it as his proudest take part in a physics school and prepare the experimental area for the career achievement to date, taking him back hosted by the Weizmann students, enabling him to combine his to his lifelong interest in quantum physics. Institute of Science in passion for education and outreach with Since its launch in June 2017, the CERN Alumni in the Alumni Network. A notable success has been a series of “Moving “CERN gave me so much!” he says. “Recently Israel. His mentor Eilam technical experience, where he would gain Network has attracted more than 6300 members The alumni.cern platform (also available as out of Academia” networking events that show- I brought 70 entrepreneurs to CERN and they Gross sparked a passion precious knowledge that could be put to use located in more than 100 countries. Predomi- an app on Android and iOS) provides mem- case sectors into which CERN alumni migrate. were blown away by their visit. Not only were for particle physics, and in his current role at the ISIS neutron and nantly a young network, with the majority of its bers with access to an exclusive and powerful Over the course of one afternoon, around half a they impressed that CERN is seeking answers Alessandro arrived at muon source at the Rutherford Appleton members aged between 25 and 39, CERN alumni network that can be leveraged as required, dozen alumni are invited to share their expe- to the most profound and relevant questions, CERN in 1991 as a summer Laboratory. “My experience at CERN range between their early 20s up to those who whether at the start of a career or later when riences in a specific sector. Events devoted but the sheer scale of project management student working on micro strip gas avalanche provided me with the bigger picture of how are over 75. After a professional experience at the desire to give back to CERN is there. The to finance, industrial engineering, big data, of such a gigantic endeavour left them in chambers for a detector to be installed in such user facilities are run,” he says. Whilst CERN, be it as a user of the lab, as an associate, a platform facilitates different groups, includ- entrepreneurship and, most recently, medical complete awe.” the DELPHI experiment at LEP. His contract at Plymouth, Stephen was also involved in student, a fellow or a staff member, our alumni ing regional groups, interest groups (such as technologies, have proved a great success. The was extended to enable him to complete Engineers Without Borders UK, which works v e nt u r e i nt o d i v e r s e c a r e e r s i n m a n y d i ffe r e nt entrepreneurship and finance) and groups for alumni provide candid and pragmatic advice Maria Carmen Morodo Testa his work, and he returned to CERN in 1992 with non-governmental organisations in fields, such as computer software, informa- m a n a g i n g t h e a lu m n i o f t h e C E R N s c i e nt i fic c ol- about working within a specific field, how to Launch range programmatic support to work on DELPHI. After three glorious developing countries on projects including tion technology and services, mechanical or laborations. Events and selected news articles market oneself and discuss the additional skills officer at ESA years, his Swiss scholarship was replaced by water sanitation and hygiene, building industrial engineering, electric/electronic are also posted on the alumni.cern platform, that are advisable to enter a certain sector. After completing her studies an Italian one with a much lower salary. A techniques and clean energy. Although he manufacturing, financial services and man- a n d m e m b e r s c a n a l s o b e n e fit f r o m m e s s a g i n g. These events attract more than 100 in-person as a telecommunications desire to buy a house and start a family forced now has a full time job, Stephen is still an agement consulting. A key appeal of the platform is its jobs board, participants and many more via webcast. engineer at the Polytechnic him to consider other avenues, drawing active volunteer, and his interests in public The network was established to enable where both alumni and companies can post job The Office for Alumni Relations has recently University in Barcelona, on his hobby of computer programming. engagement and international development our alumni to maintain an institutional link opportunities free of charge. Since its launch l a u n c h e d it s fi r s t g l o b a l C E R N a lu m n i s u r v eyto Carmen joined a “I had a number of ongoing consultancies brought him back to CERN in 2018 to share with the organisation, as well as to demon- more than 500 opportunities have been posted understand the community better and identify multinational company with external companies so I switched my knowledge on target manufacturing and strate the positive impact of a professional with 260 applications submitted directly via the problems it can help to solve. The survey results in the agro-food sector hobby for my job and physics became my testing with the CERN mechanical and CERN experience on society. Though most platform, mostly in fields such as engineering, will soon be shared with registered members, specialising in automation hobby!” Alessandro returned to Italy in 1995 materials engineering group. “Lots of CERN alumni remain in high-energy physics software engineering and data science. Several helping us to continue to build a vibrant and and control systems, whilst as a freelance software developer designing variety, public engagement and outreach research or closely related fields, those who CERN alumni have found their next position supportive network for the future. studying for an MBA. On the antennas. In 1999 he joined Milan software were part of the job’s remit and it has kept wish to use their skills elsewhere, especially thanks to the network, either directly via job university walls she spotted an advert for a company Diagramma, and transitioned its promises, he says. “There are not many early-career members, will find active support postings or through networking events. Rachel Bray Office for CERN Alumni Relations. staff position at CERN, which corresponded from telecommunications to car insurance – companies that can offer this!”

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PEOPLE CAREERS PEOPLE CAREERS A lumni speciAl A lumni speciAl

John Murray the UK and joined a technology consultancy firm Maaike Limper scientific collaborations. It was also whilst at Cynthia Keppel They started to collaborate, and a few years Private investor and synthetic-biology in Cambridge where she had the opportunity to Data engineering and web portal CERN that my first ever paper was published, Professor, Hampton University later Thia founded the Center for Advanced consultant run a variety of different small-scale projects. specialist at Swiss Global Services when DELPHI started taking data, around 1990 Having attended a small Medical Instrumentation at Hampton John arrived at CERN in 1985 “I really enjoyed that variety, I think that was Following a PhD on ATLAS, I think – I was absolutely thrilled. Even though, liberal arts college in the University. More than a dozen patented as a PhD student on the L3 what I was seeking,” she says. “Now I know that Maaike became a CERN somewhere in the middle of my career, I ended US where the focus was on technologies later, they were contacted experiment at LEP. Every at CERN there are varied jobs one person can do, openlab fellow in 2012. There up doing a lot of computational physics, CERN is philosophy, Thia found by Hampton University’s president about day was a new experience, he but at that time perhaps I wasn’t mature enough was a lot to learn in moving where I began my career as an experimentalist herself a bit frustrated. proton therapy and realised that they had the says. “My absolute favourite to realise that.” Today, she works in investment from physics to IT, she says. and I am always grateful for that.” He did not “We would discuss deep know-how to build their own proton-therapy thing was spending time with and finance, and has actively sought out roles “You need to understand how want to leave fundamental research, and today questions at length in centre, which ended up being one of the largest the summer students, out on that allow her to travel and work with people technology actually works: Panayotis is a senior scientist at Fermilab. class, and I would think:’ in the world. “Having directed the centre from the patio of Restaurant 1 in from different places. But a return visit to CERN how it stores your data as In 2014 he was head of Fermilab’s scientific Can’t we test something?’ the start, Thia preferred the period of building, the evenings, just chatting. in 2011 added another career dimension. “A bytes on the disk or how your computing division and since 2018 has led Physics seemed to be a place where people were instrumenting and commissioning the facility Everyone was so curious and knowledgeable.” fantastically positive change had happened in computations can optimise the CPU usage.” Fermilab’s Quantum Science Program, which striving to provide concrete answers to big over that of clinical operations. So she decided Despite the fulfilment of his experience, he my lifetime: the appreciation of the importance Until last year, Maaike was head of aviation includes simulation of quantum field theories, questions, so I looked for summer internships to set up a consulting company, which has so decided to pursue a career in finance, reckoning of science by wider society. It was time to think surface performance at Inmarsat, investigating teleportation experiments and applying qubit in physics, and to my surprise I got one.” She far helped to start 16 proton-therapy centres. it was a game he could “win”. He found his how to capitalise on this and help society become solutions to allow aircraft passengers to have technologies to quantum sensors in high-energy wound up working with a group of plasma “I think that my discourse-based philosophy first job on Wall Street thanks to a book he had more engaged directly with us.” The answer a reliable internet connection. One of her physics experiments. Shortly afterwards, physicists who wanted an “artsy” person to education has been a help in learning to read about option pricing, realising that the was the CERN & Society Foundation, of which challenges was to put data from all the systems he presented the Fermilab programme to make a movie visualising the solar magnetic express ideas clearly and succinctly to people,” equations were similar to those of quantum Anne was appointed chair and that has seen involved in passenger internet connectivity, CERN openlab’s “Quantum computing for flux cycle. “I liked learning the physics, I liked she says. “If you’re going to irradiate people, field theory, only easier. His employer, CERN proactively engage with society, leading such as ground control, satellites and aircraft high-energy physics” event. “Coming back to being sent off on my own, and it turned out I you must explain carefully and well why First Boston, soon gave him responsibility to the future Science Gateway project dedicated together and understand where outages were CERN was actually strange, because everything even liked the programming.” She went on that’s a beneficial thing. Once you’re used for investing the firm’s capital, and by the to education and outreach. “When we started experienced and why.” As a particle physicist, by had changed so much that I needed to follow to do a PhD in nuclear physics at SLAC and to explaining things in plain language to late 1990s he was a hedge-fund manager at the foundation in 2014 we did not know how contrast, Maaike was dealing with “very specific signs to find my way to the cafeteria!” He would continued her research at JLab where, one potential patients or the public, you can give Goldman Sachs. Realising that the investment incredibly successful it was going to be. The issues and no longer felt challenged”. She also like to see Fermilab establish an alumni night, while working late on a scintillating the same talk in a boardroom.” world was about to go digital, he started his own major part of this success comes from the interest also didn’t warm to the ruthless competition network of its own. “It is good to have a sense fibre-type particle detector, she realised that • This final case study is based on an article in company, building computer models that could and engagement we have had from alumni.” she encountered, especially when the first of community, especially during difficult times a colleague in the lab across from her was APS Careers 2020, produced in conjunction with predict market inefficiencies and designing LHC data were being collected and the normal when you need your community to stand up in building the same type of detector – but for Physics World. All other articles and images are trading strategies. “Finance textbooks said Bartosz Niemczura collaborative spirit was slightly set aside. In her support of your organisation.” a project in medical instrumentation. drawn from the CERN Alumni Network. these sorts of things were impossible, but Software engineer, Facebook new career, which recently saw her join Swiss they were all written before the markets went Bartosz graduated with a Global Services as a data-engineering specialist, digital,” he says. In recent years, John has Master’s degree in computer she feels she is the expert. “I like the fact that turned his attention to synthetic biology, where science from AGH University I am constantly kept busy, challenged and, he invests in and advises start-up companies. of Science and Technology sometimes, very much stressed!” However, her Biology is following a similar path to finance in 2012. The following year particle-physics training had a useful impact 30 years ago, he says, and the pace of progress he became a CERN technical on her career. “At CERN, we are very good at is going to accelerate as the field becomes student working on databases developing our own tools and we don’t just more quantitative. In 2018 John offered to in CERN’s IT department. expect there to be a ready-made product on the co-found the New York group of the CERN It was his first professional market.” And Maaike is proud that the detector Alumni Network. “I loved the time I spent at experience, and he was immediately captivated she worked on sits at the centre of the ATLAS CERN and the energy of its people. In setting by the field of data security. Deciding to enter into experiment. “I was there, checking that each up the New York group, I want to recreate that a career in the area, he then applied for positions optical cable was producing the right sound once atmosphere. I also hope to help young alumni elsewhere, leading to a six-month research connected and that everything was working as at the beginning of their careers. I hope we can internship at IBM Zurich, participating in the expected. So actually, yes, a little piece of my help our younger members avoid making the Great Minds Programme. “My project focused heart is there, deep inside ATLAS.” same mistakes we did!” on big-data analysis, an activity very closely related to my CERN project. I probably wouldn’t Panayotis Spentzouris Anne Richards have been selected for the internship if I hadn’t Head of Fermilab’s Quantum Science CEO at a private finance services company had the CERN experience,” he explains. “It’s Program Anne came to CERN as a not just about the experience, but also the CERN Panayotis’s affiliation summer student in 1984 reputation and prestige.” Working in a global with CERN began in 1986 and fell in love with the environment with more than 20 international as an associate physicist international environment, students was also extremely valuable. Since working on a prototype of leading her to apply for 2015 Bartosz has been working as a software a detector for the DELPHI a fellowship where she engineer for Facebook’s product security team in experiment at LEP. He worked on software and Silicon Valley. “Despite the culture being slightly moved to the US in 1990 and electronics for LEP. At the different at Facebook compared to CERN, I still started a PhD, continuing his end of the fellowship, she apply the same approach I learnt at CERN,” he research at Fermilab, first was faced with a choice. “I was surrounded by says. “Having learnt to communicate with people as a Columbia University postdoc and then a these awesomely brilliant, completely focused from other countries, this is highly useful for me junior staff scientist. Of his time at CERN he physicists who were willing to dedicate their in my current position as I now find it easier to recalls the challenging experience of working lives to fundamental research. And much as I make connections. It’s important not to close for a multi-institutional, multicultural and loved to be amongst them and was proud of my yourself off in your office. Go out and talk to multinational collaboration of many people of equipment being installed in the accelerator, I people, those who have lots of experience, or who different cultures. “I remember it being a great didn’t feel I had the same passion they did. I was are working on something different from you, experience with exposure to many wonderful still seeking something else.” She returned to ask questions, make connections!” things from machine shops to computers and

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PEOPLE CAREERS A lumni speciAl RECRUITMENT Appointments and awards

Yeck to lead EIC full-energy exploitation study instigators of the current and

Brookhaven National Laboratory from 2015–2019. Among the next future LHCb upgrades, and IUPAP For advertising enquiries, contact CERN Courier recruitment/classified, IOP Publishing, Temple Circus, Temple Way, Bristol BS1 6HG, UK. (BNL) has appointed Jim Yeck significant steps for the HL-LHC has worked extensively on Te l +4 4 (0)1 17 930 1 264 E-m a i l s a le s@c e r nc ou r ie r.c om. as the project director for the are the testing of the first triplet physics studies involving the Please contact us for information about rates, colour options, publication dates and deadlines. Electron–Ion Collider (EIC), quadrupole prototype, and the charm quark and the experiment’s which will open new vistas on RF-dipole crab cavities in the SPS. VELO detector. Brookhaven National Laboratory National Brookhaven Sette continues at ESRF 2020 Guido Altarelli awards After more than 11 years as the This year’s Guido Altarelli awards, director-general of the European which recognise exceptional Synchrotron Radiation Facility achievement by young scientists work in the development of fast Planning your next career move? (ESRF) in Grenoble, France, in the field of deep inelastic crystal sensors for the precision Francesco Sette’s term has been scattering (DIS), and related timing of charged particles, while extended to 2025. Having joined topics, have been presented to Benjamin Safdi (University of ESRF in 1991, Sette was at the Pier Francesco Monni (CERN; Michigan; right) was honoured

ESRF top) and Philip Ilten (University “For groundbreaking theoretical Join CERN, a unique work environment at the cutting edge of technology of Birmingham; below). contributions to the search for Monni was recognised for his dark matter, in particular the in a place like nowhere else on earth. the properties and dynamics of pioneering contributions to the development of innovative

quarks and gluons (CERN Courier F Monni techniques to search for axion October 2018 p31). Yeck has held dark matter, and to separate dark leading roles in BNL’s Relativistic matter signals from astrophysical CERN currently has diverse student, graduate and professional Heavy Ion Collider and National backgrounds”. The award was Synchrotron Light Source II, the presented during the 2020 opportunities open for application. US hardware contribution to the International Conference of LHC project, and the IceCube High Energy Physics (see p19). neutrino observatory (CERN Courier June 2014 p27). He was forefront of the effort to develop CMS thesis award Apply now and take part! also former director general of a new generation of inelastic Marcel Rieger (RWTH Aachen the European Spallation Source. X-ray scattering beam lines, University) has been presented https://careers.cern

Yeck will head a newly created before becoming director E Ilten with the 2019 CMS Thesis Award, EIC directorate at BNL, working of research in 2001. The with a thesis exploring “ttH” in partnership with Jefferson announcement comes at a pivotal production – the process by which Laboratory and others. The EIC is time for the ESRF, as the European a Higgs boson is created scheduled to begin operations at facility begins user operations of in high-energy particle collisions BNL at the end of the decade. its brand new Extremely Brilliant in combination with two top Source (see p13). quarks. The annual award is given Brüning takes hi-lumi helm to the best PhD of the year, based CERN’s Oliver Brüning has New LHCb spokesperson on originality, importance and succeeded Lucio Rossi, who retires Chris Parkes of the University clarity, and Rieger’s contribution this year, as project leader for the of Manchester, UK, became to the first observation of ttH High-Luminosity LHC (HL-LHC). spokesperson of the LHCb theory and phenomenology of production in 2018 made him stand Brüning, who completed his PhD collaboration on 1 July for a period multi-scale QCD resummation, out among the 25 other nominees. on particle dynamics at HERA, of three years, taking over from and Ilten, a member of the LHCb joined CERN in 1995 one year Giovanni Passaleva of the National collaboration, for his exceptional LHCb honours young researchers after the LHC was approved. Institute for Nuclear Physics in contributions to bridging the In June, the LHCb collaboration He has been at the forefront of Florence, Italy. Previously gap between experiment and announced the recipients of

accelerator and beam physics ever A Ricoult phenomenology in QCD and its 2020 PhD Thesis and Early since, being one of the initial six proton structure. The ceremony Career Scientist Awards. Thesis machine coordinators during the took place during a LHCb awards were presented to Philippe LHC start-up and leading the LHC collaboration meeting in June. D’Argent of Heidelberg University

A Jankoviak A and Laurent Dufour of Nikhef/ IUPAP Young Scientist Prize Groningen University, while The International Union of early-career prizes were granted Pure and Applied Physics to Carlos Abellan Beteta (Zurich), (IUPAP) has awarded its Young Claudia Bertella (CERN), Daniel Scientist Prize for 2020 to two Campora (Nikhef), Nadim Conti early-career researchers working (INFN, Milan), Edgar Lemos Cid deputy LHCb spokesperson, in high-energy physics. CMS (Santiago de Compostela), Olli Parkes has been a member of member Marco Lucchini of Lupton (Warwick), Mark Smith the collaboration for more than Princeton University (left) was (Imperial College) and Dorothea 20 years. He was one of the recognised “For his pioneering vom Bruch (LPNHE, Paris).

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Deutsches Elektronen-Synchrotron DESY We are ready to design and build this accelerator. Are you? A Research Centre of the Helmholtz Association

At MYRRHA (www.myrrha.be), based in Mol, For our location in Hamburg we are seeking: Faculty Position in Theoretical Belgium, we firmly believe that our unique research facility must serve society. That’s why DESY-Fellowships - High Energy Physics we’re building an Accelerator Driven System Experimental Particle Physics (ADS): our sub-critical lead–bismuth cooled at the Ecole polytechnique fédérale reactor will be driven by a super conducting, DESY. de Lausanne (EPFL) high power proton linear accelerator. DESY is one of the world’s leading research centres for photon science, particle and astroparticle physics as well as accelerator physics. More The School of Basic Sciences (Physics, Chemistry and Mathemat- “Building the most reliable accelerator in the world is a challenge that appeals to me.” than 2700 employees work at our two locations Hamburg and Zeuthen in ics) at EPFL seeks to appoint a tenure track Assistant Professor in Angélique Gatéra science, technology and administration. Theoretical High Energy Physics. The appointment is solicited at Our goal is to build the first 100 MeV stage of the superconducting, high power Are you searching for a challenge that Particle physics and the investigation of the fundamental building blocks the Tenure Track level, but in exceptional cases, appointments at of nature and their interactions are at the core of the DESY mission. We proton linac. This includes selecting systems and components with redundancy contributes to solving some of society’s other ranks will be considered as well. take significant responsibility in internationally leading projects, e.g. and extreme reliability in mind. Join a community of energetic explorers! most important issues, such as closing at CERN and at KEK, and on our campus. We develop detectors and We primarily target scientific excellence by searching broadly in We are looking for your expertise in many accelerator technology fields. the nuclear fuel cycle, transforming the lives of cancer patients or conducting technologies relevant for our experimental activities, and we engage in this area. Preference will be given to applicants who can produce For now we are looking for a: fundamental physics research? scientific computing and in the development of future accelerators for innovative ideas in particle physics and cosmology as well as think particle physics. • Head of the accelerator group critically and originally on the more conceptual problems in Quan- • Technical risk analysis (machine and personal protection) Don’t look any further and apply! The position tum Field Theory. • Embedded System Engineer (Low-level RF) You are invited to take an active role in one or more of the following areas • Project engineer (control system) at Hamburg: Candidates should have an excellent record of scientific accom- • Power converter engineer https://www.sckcen.be/en/careers l Our involvements at CERN (ATLAS, CMS) and at KEK (Belle II) plishments. In addition, commitment to teaching at the under- • ... l Experimental activities on-site (ALPS II and future on-site experiments) graduate, master and doctoral levels is expected. Proficiency in l Preparations for future particle physics experiments, in particular French is not required, but a willingness to learn the language is Exploring detector and technology development appreciated. a better tomorrow l Scientific computing l Accelerator development EPFL, with its main campus located in Lausanne, Switzerland, on advertentie CERN 193mmx130mm.indd 1 2020-09-01 11:39:39 Requirements the shores of Lake Geneva, is a dynamically growing and well-fund- l Ph.D. in physics completed within the last four years ed institution fostering excellence and diversity. It has a highly in- ELI Beamlines research centre in Dolní Břežany is part We o er: l Interest in particle physics ternational campus with world-class infrastructure, including high of pan-European Extreme Light Infrastructure supporting l • the opportunity to participate in this unique scienti c Expertise relevant for at least one of the areas listed above performance computing. scienti c excellence in Europe by making available its project DESY-Fellowships are awarded for a duration of 2 years with the capacities to the best scienti c teams across the world. • competitive and motivating salary possibility of prolongation by one additional year. EPFL covers the entire spectrum of science and engineering. The ELI Beamlines is part of the Institute of Physics of the Czech Academy of Sciences. The High Field Initiative • Ž exible working hours Futher informations and a link to the submission system for your Together with nearby CERN it offers a fertile environment for re- search and cooperation between different disciplines. The EPFL en- project at the ELI-BL is established to be the leading • career growth application and the references can be found here: • lunch vouchers, pension contribution and 5 sick days vironment is multi-lingual and multi-cultural, with English serving project in the high  eld science. http://www.desy.de/FellowFH • support of leisure time activities Please note that it is the applicants responsibility that all material, as a common interface. including letter of references, reach DESY before the deadline for the Applications should include a cover letter, a CV with a list of pub- Interviews will begin immediately and the position will stay application to be considered. open until  lled. Salary and benefits are commensurate with those of public service lications, a concise statement of research (3 pages) and teaching The HiFI-ERT (Excellence Research Team) recruits organisations in Germany. Classification is based upon qualifications and interests (1 page), and the contact information of at least three a scientist for developing theory and computer assigned duties. Handicapped persons will be given preference to other references. simulations on the following activities: Applications, containing CV, cover letter, contacts of equally qualified applicants. DESY operates flexible work schemes. DESY references, and any other material the candidate considers Applications should be uploaded in PDF form by October 20th, is an equal opportunity, affirmative action employer and encourages • theory of charged particle acceleration and hard relevant, should be sent to 2020 to : applications from women. Vacant positions at DESY are in general open electromagnetic radiation in relativistic laser plasma Mrs. Jana Ženíšková, HR specialist ([email protected], +420 - 601560322). to part-time work. During each application procedure DESY will assess https://facultyrecruiting.epfl.ch/positiondetails/23691265 • development and use of various computer codes for whether the post can be filled with part-time employees. simulation of nonlinear processes in laser plasmas Information regarding the personal data processing and Deadline for applications: 2020/09/30 Enquiries may be addressed to: Further questions on scienti c project can be addressed to access to the personal data at the IoP CAS can be found Prof. Harald Brune on: https://www.fzu.cz/en/processing-of-personal-data. We are looking forward to your application via our application system: Chair of the Search Committee Sergei Bulanov ([email protected]) www.desy.de/onlineapplication E-mail : [email protected] Requirements: Deutsches Elektronen-Synchrotron DESY Human Resources Department | Code: FHFE003/2020 For additional information, please consult het.epfl.ch, • PhD in Physics or Mathematics with the focus on Notkestraße 85 | 22607 Hamburg Germany iphys.epfl.ch, sb.epfl.ch theoretical and computation physics related to Phone: +49 40 8998-3392 http://www.desy.de/career nonlinear waves, charged particle acceleration, quantum electrodynamics, numerical modeling of EPFL is an equal opportunity employer and family friendly university. It is committed to increasing the diversity of its faculty. It strongly encourages relativistic plasmas women to apply.

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Ulrich Becker 1938–2020 Take the next step in your career with Physics World Jobs. A master of detectors and hardware

Ulrich J Becker, a major contributor to LEP’s MIT drift chamber would provide large acceptance physicsworld.com/jobs L3 experiment and the Alpha Magnetic Spec- coverage for experiments, and his drift tube trometer (AMS), passed away on 10 March at enabled physicists to measure particles near the age of 81. Born in Dortmund, Germany, on the interaction point. Those developments 17 D e c e m b e r 1938 – t h e d a y t h a t nu c l e a r fi s s i o n led Becker to design and build the huge muon was discovered in Berlin – as a young man he detectors for the MARK-J experiment at DESY, was adept as an electrician, coal miner and which resulted in the discovery of the three-jet even in steel smelting. More drawn to phys- pattern from gluon production. Becker then led ics, he studied at the University of Marburg hundreds of colleagues in designing the muon and obtained his PhD in Hamburg, focusing detector for the L3 experiment at LEP. on the photo-production and leptonic decays In 1993 Becker started to work with MIT’s of vector mesons. team on building AMS – another Ting pro- In late 1965 Becker met Sam Ting, who admit- ject that was born when he and Becker were ted him to his group at DESY using the 6 GeV on a coffee brea k wh i le work i ng on L3. Bec ker synchrotron to measure the size of the electron. then went on to help design the transition It was a complementary match: Becker was radiation detector for AMS-02, which has so a dogged researcher with detector and hard- far collected more than 150 billion cosmic-ray ware acumen, and Ting was a master in scien- events from its position on the International tific organisation and politics. In 1970 Becker Ulrich Becker was a long-time collaborator with Space Station. joined the MIT faculty, where he found mentors Sam Ting. Becker was a mentor to many great phys- including Victor Weisskopf and Martin Deutsch. icists. He also made important contributions He was promoted to associate professor in 1973, l o n g-l i v e d h e a v y r e s o n a n c e. T i n g fle w t o St an- to advancing international collaboration in Department of Space and Climate Physics and the following year he began designing a ford in November and he and Richter quickly high-energy physics, for example involving precision spectrometer for Brookhaven National organised a lab seminar. They presented their China. In 2013 he transitioned to emeritus status Laboratory. He joined a group led by Ting that discovery of the J/ψ particle, a bound state of at MIT, but still he came in every day to men- Now accepting applications for: Image: NASA astronauts used the spectrometer to search for heavy par- a charm quark and antiquark, on 11 November tor students. At the age of 81 he even picked repair the Hubble Space ticles produced when protons were smashed 1974, sparking rapid changes in high-energy up Python to continue his craft. His friendly MSc Space Science and Engineering Telescope into a fixed target of beryllium. Instead, the physics. Ting and Richter shared the 1976 Nobel approach and deep understanding of physics The space industry is a multi-billion pound industry in the UK team recorded an unexpected bump in the data Prize in Physics for the J/ψ discovery. If only one made him a superb teacher, even if his style and is growing world-wide. In a programme taught by the UK’s corresponding to the production of a heavy par- of the groups, MIT, had discovered the particle, was highly individual. largest university space science department, learn how to design ticle with a lifetime that was about a thousand it is likely that Becker would also have shared Our community has lost an excellent a space mission from payload selection to launch and operation. times longer than predicted. in the prize. researcher and teacher, and a wonderful col- Taking the Space Technology pathway, you will learn cutting Meanwhile, MIT alumnus Burton Richter was Made a full professor at MIT in 1977, Becker league and human being. edge space applications for science and technology including mechanical reviewing data from Stanford Linear Accelerator developed several other major instruments that and electrical design of satellites. Laboratory when he too found what looked like a were the catalyst for discoveries. His large-area His friends and colleagues at MIT. P Loïez The Space Science pathway prepares you for a career in the exciting fields claUde détr az 1938–2020 of experimental solar-, planetary-, or astro- physics. Learn how to design and operate scientific instrument in space from scientists and engineers that work on ESA and NASA missions. A true visionary Find more information and apply at: bit.ly/MSSL_MSc Claude Détraz was born on 20 March 1938 in evidence of deformation in exotic nuclei at MSc Space Risk and Disaster Reduction Albi, in the south of France. He graduated a shell closure. Drawing on these results, he from the École Normale Supérieure and began became convinced that the beams at the Grand In an increasingly technological and globally connected world, his research career at CNRS in 1962, studying Accélérateur National d’Ions Lourds (GANIL) risks to space-based communications systems and critical atomic nuclei. Détraz then joined the Institut laboratory in Caen could also become a unique infrastructure are emerging threats to national security and de Physique Nucléaire d’Orsay, founded by Irène tool in t his field. businesses. and Frédéric Joliot Curie, which has recently As director of GANIL from 1982 to 1990, he This unique programme unites emergency response, disaster risk reduction been merged with its neighbouring laboratories launched several research projects on exotic and space technology, you will learn about satellite technology, mission in Orsay to form the Laboratoire de Physique nuclei. The legacy of these projects is still with design, hazards and vulnerabilities unique to outer space, and the monitoring des 2 Infinis Irène Joliot-Curie (IJCLab). us today and will continue into the future. of hazards on Earth from outer space. Taught jointly with the Institute of Risk At CERN’s Proton Synchrotron (PS), in Détraz was one of the main founders of NuPECC collaboration with Robert Klapisch’s team, (the Nuclear Physics European Collaboration Claude Détraz was CERN research director from and Disaster Reduction, this programme is a blend of disaster science and s space technology. he contributed to the discovery of the first Committee) and was its first chair from 1989 1999–2003. Find more information and apply at: bit.ly/MSSL_MSc

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PEOPLE OBITUARIES

to 1992, cementing its position as the main Détraz made a major contributed substantially. coordinating committee for nuclear physics Throughout his career Détraz promoted in Europe. contribution to and supported interaction between scientific In 1991 Détraz became a technical adviser in disciplines. As a nuclear physicist he estab- t he office of t he Frenc h minister for researc h, ensuring that the lished strong links with particle physics. He Hubert Curien. Through his involvement with was also one of the architects of the emergence d e c i s i o n-m a k i n g b o d i e s a t a l l l e v e l s i n F r a n c e, LHC project was of astroparticle physics, and received multiple Détraz made a major contribution to ensuring honours bot h in France and abroad. that the LHC project was approved in 1994. approved in 1994 Détraz was a great scientist and a true For example, he played a key role in Curien’s visionary, who played a major role in nuclear appointment as president of the CERN Council, a and particle physics in France and Europe. p o s it i o n f r o m w h i c h h e w a s a bl e t o e x e r t a m aj or General at that time, appointed Détraz As well as being a brilliant scientist and i n flu e n c e i n t h e fi n a l p h a s e s o f t h e d e c i s ion.As as director of research, jointly with Roger occupying several high-level positions, Claude director of IN2P3 at CNRS from 1992 to 1998, he C a s h more, u nt i l 2003. Th i s w a s a p e r io d fi l le d was a true “Enlightenment man” of great h e l p e d t o pr o v i d e t h e i m p e t u s, fi r s t w it h R o b e rt with important events for CERN, including culture and finesse. He was a shining light of Aymar and then with Catherine Cesarsky of the the shutdown of LEP, the excavation of new our generation. C E A, t o F r a n c e’s w h ol e h e a r t e d p a r t i c i p a t i o n i n caverns for the LHC and the start of a project to the LHC adventure. send neutrinos from CERN to the underground Michel Spiro former president of the In 1999 Luciano Maiani, CERN Director- laboratory at Gran Sasso, to which Claude CERN Council.

John Flanagan 1964–2020 Accelerating physics at KEK A c c e l e r a t or p h y s i c i s t Jo h n Fl a n a g a n, w h o m a d e His beam-monitoring important contributions to beam instrumen-

tation for the KEKB and SuperKEKB projects in M Masuzawa work played a key role Japan, passed aw ay on 13 Marc h. John grew up in The Valley of Vermont, grad- in KEKB’s achievement uating from Harvard University in 1987 with a degree in physics, astronomy and astrophysics. of the world’s highest After working for a few years at software com- panies and at the Space Sciences Laboratory luminosity at an at Berkeley, he attended graduate school in physics at t he Un iversit y of Haw a i’i at M a noa electron–positron in 1992 and joined the Super-Kamkiokande accelerator e x p e r i m e nt i n Ja p a n a t a n e a rl y s t a g e. Jo h n t o o k t he first dat a-t a k i ng sh i f t on t he e x per i ment in 1996, and the following year completed his t h e s i s o n t h e fi r s t o b s e r v a t io n o f a t m o s p h e r ic Finally, he developed an innovative X-ray neutrino oscillations at Super-Kamkiokande, b e a m profi le m on it or i n g t e c h n iq ue b y a d a p t- Agilent is Your Dry Vacuum s u p e r v i s e d b y Jo h n L e a r n e d. He t h e n b e c a m e a ing techniques from X-ray astronomy and research fellow in the KEK accelerator division using innovative high-speed electronics. In where his talent was quickly recognised. He the near future, an upgraded version of this Solutions Partner was appointed as an assistant professor in 1999, X-ray monitor will be used to realise John’s an associate professor in 2008 and promoted dream of bunch-by-bunch measurements of to full professor in 2016. small vertical beam sizes. TwisTorr 305-IC and TwisTorr 305 FS Clean, quiet, performing, easy to integrate John was well known for his immense In addition to his fluent command of Japa- and connected vacuum for your experiments contributions to the KEKB and SuperKEKB nese and understanding of Japanese manners, projects. His work on the photoelectron insta- John was a modest and kind person who was bility, monitoring of the beam size via synchro- John Flanagan made immense contributions to beloved by his colleagues in the KEK accel- – New TwisTorr 305 turbo pumps with smart connectivity: Bluetooth, USB and NFC tron light and X-rays, and feedback systems the KEKB and SuperKEKB projects. erator division and by those on the Belle and played a key role in KEKB’s achievement of B e l l e II e x p e r i m e nt s. He w a s a l s o k n o w n for h i s the world’s highest luminosity at an electron– Jo h n a l s o l e d w or k o n t h e r e m e d i a t i o n o f t h e activities on gender-equality issues, including – IDP dry scroll pumps: sustainable, quiet, oil-free, with inlet isolation valve positron accelerator. He is most celebrated electron-cloud effect, in particular concerning p a r t ic ip at ion i n t he Jap a ne s e Phy sic a l S o c ie t y for his outstanding work on the synchrotron the onset of the electron-cloud blowup and taskforces and committees as well as serving IDP-7 and IDP-10 Scroll Pumps – Wide portfolio of ion pumps and controllers, from the inventor of UHV radiation (SR) light monitor using interfer- its relation to the head–tail instability, which as an instructor at the Rikejo science camp for ometry, which allows real-time measurement has been quite visible in the global accelerator high-school girls. of micron-level beam sizes. For SuperKEKB, community. In addition to being one of the We will all remember John with the greatest Learn more: he greatly improved the SR monitor by using key accelerator problems for KEKB and of respect, as a splendid person, an innovative a diamond mirror; this eliminated the SuperKEKB, the solution to the electron-cloud scientist and someone who we are very proud to www.agilent.com/chem/vacuum systematics from thermal expansion of the problem will also benefit the future Interna- have had the opportunity to work with. 00 800 234 234 00 (toll-free) • [email protected] mirror that had plagued the SR monitoring tional Linear Collider, where it is needed for system in KEKB. successful operation of the damping rings. His friends and colleagues.

© Agilent Technologies, Inc. 2020 Agilent Ion Pump and IPCMini controller

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PEOPLE OBITUARIES

Henri Laporte 1928–2020 Leading the construction of LEP

Henri Laporte, who led the civil-engineering CERN to study damage and take urgent decisions. In work for the Large Electron Positron collider (LEP) 1988 t he t unnel w as finally completed. at CERN, passed away on 18 May. Built in the But the main tunnel represented less than half 1980s, LEP was the biggest construction project the total excavation work, as the ring is punc- for fundamental research ever undertaken and tuated with access shafts, caverns and service included the construction of the 27 km-circum- tunnels. In addition, around 80 buildings were ference tunnel that now houses the LHC. built on the surface. Jean-Luc Baldy, who man- A native of Sète in the south of France, Laporte aged the surface work, and Michel Mayoud, who graduated from the École Polytechnique and École was in charge of the crucial work of the surveyors, des Ponts et Chaussées, and began his career in remember the trust that Laporte placed in them, 27 SEPTEMBER-1 OCTOBER 2021 marine engineering in the early 1950s. He was giving them considerable room for manoeuvre. appointed as chief engineer, first for the con- Once the construction work had been com- struction of the port of Oran and then the Toulon pleted, CERN became entangled in protracted naval base, before moving to French Polynesia Henri Laporte, photographed in 2017. legal proceedings involving the consortium of in 1963 to preside over the extension of the Port companies that had carried out the work. Laporte 1 of Papeete. In 1967 he was recruited by CERN to T h e fl a g s h i p c o n s t r u c t io n pr oj e c t b e g a n i n 1983 spent several years working with the CERN legal lead the technical services and buildings division. with the excavation of 18 shafts, followed by the service, once more demonstrating his trademark @BSBF2021 #bsbf2021 Known for his relentless work ethic, expertise excavation of the tunnel itself. Three tunnel-bor- persistence. At the arbitration tribunal, Laporte and authority, Laporte joined LEP at the start of ing machines were required to dig out 23 km’s distinguished himself not only for his technical the 1980s and was given responsibility for the worth of earth under the plain. Explosives were knowledge, but also his talent as an actor and his Early Bird Registration: 30 April 2021 hugely ambitious civil-engineering project by used to excavate the section of the tunnel below humour. He retired in 1993 and devoted himself project leader Emilio Picasso. Before excavation the Jura mountains due to fears that a geological to numerous intellectual and artistic pursuits. 1 could begin, however, CERN had to get the local incident could halt the progress of the machines. Henri Laporte was a man of great curiosity and authorities on board as the tunnel would pass And such an incident did indeed occur in 1986, was highly knowledgeable in many fields. He will underneath about 10 Swiss and French communes, when high-pressure inflows of water flooded the b e r e m e m b e r e d a s a c h a r i s m a t ic m a n, w it h a fi r m and nine sites would be built on the surface. Under tunnel, causing delays to the project. Laporte’s hand and great tenacity, but also someone who Robert Lévy-Mandel, who was in charge of the expertise and leadership were decisive in the exuded a contagious joviality and always showed impact study, dozens of consultation meetings response to this incident and throughout the compassion towards his colleagues. were held. Laporte shone on these occasions project as a whole. It was a regular occurrence thanks to his oratory and interpersonal skills. for him to arrive on site any time of day or night His friends and colleagues.

GeorGe triLLinG 1930–2020 An exemplary leader

George Trilling passed away in Berkeley, Califor- photograph Family oration, the first major experiment approved for nia, on 30 April at the age of 89. Born in Poland, the SSC in 1990. Despite retiring in 1994, he was he completed his PhD at Caltech in 1955 and two instrumental in helping to organise and negotiate years later joined the University of Michigan. the US participation in the LHC. In 1960 he joined the faculty at the University Throughout his career, George was asked to of California, Berkeley and the scientific staff take on important leadership roles. At the age of at what is now called the Lawrence Berkeley 38 he became chair of the UC Berkeley physics National Laboratory (LBNL). He followed Don department. From 1984 to 1987 he was director Glaser, whose invention of the bubble chamber of the physics division at LBNL, where he guided provided a new way to view particle interactions, a major evolution towards precision semicon- and teamed up with Gerson Goldhaber. ductor detectors – still a dominant theme at the The Trilling–Goldhaber group used bubble lab today. Work on pixel detectors for the SSC, chambers developed at Berkeley to study K-me- custom ASIC design, the Microsystems Lab and son interactions. In the early 1970s the group the CDF silicon vertex detector all began under joined SLAC colleagues led by Burt Richter and George Trilling was instrumental in securing his leadership. The Berkeley group is now a major Martin Perl to build the Mark-I detector for the US participation in the LHC. participant in the ATLAS collaboration at the LHC. SPEAR electron–positron collider. The Mark-I A member of the National Academy of collaboration went on to discover the J/ψ res- of the B meson among other important results. Sciences, in 2001 George served as president of onance, charmed particles and the tau lepton. George was a key figure in the many US studies the American Physical Society. He also chaired Beginning in the 1980s, the group continued their in the 1980s that led to the successful proposal innumerable national panels, committees and collaboration with SLAC to construct the Mark- II for the Superconducting Super Collider (SSC). He task forces. We shall miss him greatly.

d e t e c t or, w h i c h w a s fi r s t i n s t a l l e d a t SPE A R, a nd served on the SSC board of overseers and helped MINISTERIO DE CIENCIA later moved to the higher energy PEP collider, foster the early SSC design phase at LBNL. He Abe Seiden UC Santa Cruz; Bob Cahn, E INNOVACIÓN where it enabled the measurement of the lifetime initiated and led the Solenoidal Detector Collab- Gil Gilchriese and Jim Siegrist DOE. @CDTIoficial

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Notes and observations from the high-energy physics community Particles mean prizes From the archive: September/October 1980

NblFudtion Foundat Nobel Pioneers … Just five researc h areas account The ‘hot news’ at the XI International for more than half of Nobel prizes, even though they publish only 10% Conference on High Energy of papers, reveals a study by social Accelerators, held at CERN from 7–11 CERN77.7.95 scientists John Ioannidis, Ioana- July, was the spectacular first operation Alina Cristea and Kevin Boyack of the CERN Antiproton Accumulator (PLOS ONE 15(7):e0234612). The t rio (see image, right). The AA ring, one of mapped the number of Nobel prizes the most demanding ever built, was At the control console during in medicine, physics and chemistry completed in less t han t wo years. commissioning are (left to bet ween 1995 and 2017 to 114 fields At the 66th Session of the CERN right) Roy Billinge, who led the of science, finding t hat par t icle Council on 27 June, the project for a construction, Eifionydd Jones physics came top with 14%, followed large electron–positron storage ring and Simon Van der Meer. by cell biology (12%), atomic physics (LEP) was formally presented as (11%), neuroscience (10%) and molecular chemistry (5%). Europe’s next major high-energy Particle-physics prize-winners in the period studied include: physics research facility. By using Perl and Reines (1995) for the discovery of the tau lepton and CERN’s existing proton accelerators in the detection of the neutrino; ’t Hooft and Veltman (1999) for the injection scheme (PS and SPS), contributions to electroweak theory; Davis and Koshiba (2002) for Council ag reed t hat t he project can be the detection of cosmic neutrinos; Gross, Politzer and Wilczek (2004) considered as an extension of CERN for asymptotic freedom; Nambu, Kobayashi and Maskawa (2008) for facilities, to simplify authorization in a work on spontaneous symmetry breaking and quark mixing; Englert number of Member States with ‘Phase 1’ and Higgs (2013) for the Brout–Englert–Higgs mechanism; and Kajita – 50 GeV per beam and four e x per imental The symbol used at Uppsala and McDonald (2015) for the discovery of neutrino oscillations. The halls – being financed within existing to convey what the team also chose to class Mather and Smoot’s 2006 prize relating to the budget levels for a cost of 900 million ‘International Conference cosmic microwave background, Perlmutter, Schmidt and Riess’s 2011 Sw iss fr ancs over eight years. on Experimentation at LEP’ award for the discovery of the accelerating expansion of the universe, From 16–20 June some 350 physicists was all about. and Weiss, Barish and Thorne’s 2017 gong for the observation of gathered at the University of Uppsala, Sweden, to take a first look at g rav itat ional w aves as par t icle-physics researc h. the challenges of LEP’s experiments. For data collection and analysis, the way to go looked to be distributed rather than aral i k la rda Pa M monolithic, with many computers dedicated to specific tasks. Neutrino Establishing standards throughout the data-handling system would passoire ease the participation of small groups.  Based on CERN Courier September 1980 p235, p255; October 1980 p292.

According to Hesiod, w rit ing Compiler’s note in the seventh-century BCE, During the 1980s, standard data-acquisition hardware, CAMAC and Zeus and Mnemosyne gave FASTBUS, became widespread in the field, with brave attempts to define bir t h to nine Muses who Muses Neutrino Passoire will open in and adopt standards for the associated software. Distributed computing inspire the world’s artists. Annecy, France, on 12 October. was commonplace in LEP experiments and across the community, Judging from recent increasing the acceptance of networking that culminated in the invention arts–sciences collaborations (e.g. CERN Courier 2020 July/August p62), of the Web at CERN in 1989, contemporary with LEP start-up. t he sisters may have a hit her to un k now n sibling: t he neut rino. The latest oeuvre by choreographer Mairi Pardalaki and particle physicist Kostas Nikolopoulos of the University of Birmingham The most massive black- explores how neutrinos originate in the Sun and pass through our hole merger yet observed bodies undisturbed. This gave Pardalaki the idea that the human body is not a for t ress, but a colander. “Le neutrino vois des passoires by the LIGO and Virgo partout,” she nar rates (“The neut rino sees colanders ever y where”), gravitational-wave as two dancers, arms aloft and entwined in a single red elastane detectors. Announced on shi f t, revolve on stage, before abr upt ly inject ing karaoke snippets +28 2 September, the merger 142–16 M⊙ from Ella Fitzgerald’s timeless collaboration with Louis Armstrong is the first clear detection into the performance. The dance is also intended to be an allegory of an intermediate-mass for the cross-border movement of people. “Both particle physicists and artists try to make something that’s invisible, visible,” observes black hole – an object Ni kolopoulos. “What we cal l t he creat ive process in ar t is just what we thought too large to result call researc h in science.” from such inspiral events.

70 CERN COURIER SEPTEMBER/OCTOBER 2020

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