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CERNMarch/April 2021 cerncourier.com COURIERReporting on international high-energy WELCOME CERN Courier – digital edition Welcome to the digital edition of the March/April 2021 issue of CERN Courier.

Hadron have contributed to a golden era of discovery in high-energy physics, hosting experiments that have enabled to unearth the cornerstones of the . This success story began 50 years ago with CERN’s Intersecting Storage Rings (featured on the cover of this issue) and culminated in the Large (p38) – which has spawned thousands of papers in its first 10 years of operations alone (p47). It also bodes well for a potential at CERN operating at a centre-of- energy of at least 100 TeV, a feasibility study for which is now in full swing.

Even hadron colliders have their limits, however. To explore possible new physics at the highest energy scales, physicists are mounting a series of experiments to search for very weakly interacting “slim” that arise from extensions in the Standard Model (p25).

Also celebrating a golden anniversary this year is the Institute for Nuclear Research in Moscow (p33), while, elsewhere in this issue: quantum sensors HADRON COLLIDERS target gravitational waves (p10); X-rays go behind the scenes of 50 years of discovery 1987A (p12); a high-performance computing forms to handle the big-physics data onslaught (p22); talks about his latest work (p51); and much more.

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EDITOR: MATTHEW CHALMERS, CERN DIGITAL EDITION CREATED BY IOP PUBLISHING ATLAS spots rare Higgs decay  Weinberg on effective field theory  Hunting for WISPs

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It’s ALL ATLAS Baikal-GVD CERN about the DETAILS

Dalitz decay ATLAS spots rare decay of the Higgs Universal search Baikal-GVD will continue the Staff search CER N’s efforts to attract to a and a low-mass or pair. 17 astrophysical search. 33 non-physicists into key roles. 61

NeWS people

ANALYSIS ENERGY FRONTIERS FIELD NOTES CAREERS OBITUARIES AEgIS on track to test First evidence for rare Tooling up to hunt dark Accelerating talent • free fall Higgs-boson decay • Computing at CERN • Martinus Veltman • NICA sees first beam • collaboration kicks off The challenge of attracting • Günther Plass • CLOUD and Arctic sea searches • Precision • -matter fireballs engineers, technicians • André Martin ice Quantum sensing leap for B0 shines in Protvino. 21 • s • and others who build and • • Farewell Daya Bay inside nuclei. 17 maintain CERN’s complex • Stephen Reucroft • The core of SN1987A. 7 infrastructure. 61 • Jean-Claude Berset. 69 FeaTureS

WISPS DESY/Heiner Müller-Elsner INR RAS HADRON COLLIDERS LHC In search of WISPs Russia’s - Discovery machines A decade in LHC New experiments will physics powerhouse and Peter publications expand the search for The Institute for Nuclear Jenni look at the lessons Alex Kohls, Jens Vigen and other weakly Research in Moscow learned from 50 years and Micha Moskovic interacting ‘slim’ particles continues to leave its of experience with look back on the that could hail from far mark on neutrino and hadron colliders and first 10 years of LHC above the TeV scale. 25 high-energy physics. 33 their detectors. 38 publications. 47

opiNioN DeparTmeNTS

VIEWPOINT INTERVIEW REVIEWS FROM THE EDITOR 5 Power Supply Systems CERN Connecting physics Still seeking The hitchhiker’s NEWS DIGEST 15 Precision Current Measurements with society solutions guide to weak decays APPOINTMENTS 62 We must communicate Steven Weinberg reflects An expedition to & AWARDS Beamline Electronic Instrumentation the applications and on effective field theory new physics summits RECRUITMENT 64 impact of our field, and his latest attempt to • The science of On the cover: CERN’s FMC and MicroTCA argues Barbora Bruant understand the learning physics. 57 Intersecting Storage Rings, BACKGROUND 74 Gulejova. 49 mass hierarchy. 51 the first .38 www.caenels.com CERN COURIER MARCH/APRIL 2021 3

MASTER - February 2021_Paolo.indd 1 05/02/21 13:20 CCMarApr21_Contents_v3.indd 3 12/02/2021 09:42 CERNCOURIER www. V o l u m e 6 1 N u m b e r 2 M a r c h / A p r i l 2 0 2 1 edwardsvacuum.com CERNCOURIER.COM ENABLING RESEARCH IN UHV FROM THE

Edwards are able to supply a total • Primary pumps nXDS dry scroll EDITOR vacuum package from UHV through to pumps and RV oil sealed rotary vane atmospheric pumping from a range of pumps for excellent ultimate and products including: superior vapour handling • Ultra-high vacuum Gamma With our advanced modelling The rewards of bold thinking pumps for low cost and vibration capabilities and years of experience free operation in scientific research, rest assured ack in the early 1960s, as this month’s cover feature European strategy for , CERN is exploring the Edwards has the vacuum expertise to describes (p38), discussion raged at CERN about the most ambitious long-term technological path in undertaking • High vacuum nEXT and STP meet your application requirements. Bnext best step for particle physics. At the time, the high- a feasibility study for a future circular hadron collider with a turbomolecular pumps including energy frontier was commanded by the great synchro- centre-of-mass energy of at least 100 TeV. If built, the success versions for high throughput and [email protected] trons, such as Brookhaven’s Cosmotron and, later, CERN’s of this mother of all hadron colliders will have each generation Proton , which drove fixed-target experiments. of previous machine and its detectors to thank. hardened designs But a new type of machine capable of exploiting the full energy Matthew of proton beams for the production of new particles – the Know your limits Chalmers hadron collider – was revving up in the sidelines. In Decem- As productive as hadron colliders are in probing at Editor ber 1965 the CERN Council approved the construction of the the highest energies, many current mysteries, such as dark more technologically innovative Intersecting Storage Rings matter and the origin of neutrino , may well origi- (ISR) over a very high-energy , although nate from phenomena at the latter would materialise 10 years later in the Super Proton energy scales inaccessible Synchrotron (SPS). The ISR’s first proton–proton collisions, to any collider imaginable. which reached a centre-of-mass energy of 62 GeV, took place Fortunately, models involv- on 27 January 1971, opening the era of hadron colliders. ing such scales can be tested From the ISR came the ingenious conversion of the SPS now and in the near future by a CERN-PHOTO-201802-030-9 into a proton– collider (Spp–S), the demonstration series of experiments – some of large-scale technology for the using magnets from the LHC at , and the LHC, whose elegant magnet and HERA in fact – searching design has enabled the highest collision energies (13 TeV) for very weakly interacting and luminosities to date. Each machine, and its increasingly “slim” particles that arise complex detectors, was a step into the unknown, requiring in extensions of the Stand- the invention of new technologies and sharp political and ard Model (see p25). Effective organisational skills to build and operate ever larger facil- field theory is another power- ities. The payoff was the discovery of the Standard Model’s ful tool to pursue such signals cornerstones: the W and Z at the Spp–S, the from far beyond the TeV scale, at the Tevatron, and the at the LHC. Not to be Discovery machine The LHC. explains Steven Weinberg in omitted from the hadron-beam collider success story are the this issue’s interview (p51). leaps in understanding of strongly interacting matter brought Meanwhile at CERN: ATLAS reports the first evidence for a Each machine, about by Brookhaven’s Relativistic Heavy-Ion Collider and the rare “Dalitz” decay of the Higgs boson (p17); pulsed-mode anti- and its LHC, and the deep-inelastic scattering experiments at DESY’s paves the way to test antimatter in free fall (p7); and increasingly so-far unique electron–proton collider HERA, which revealed the CLOUD experiment reveals a new mechanism that could complex the proton’s innards in full colour. accelerate the loss of Arctic sea ice (p9). Elsewhere in this issue: H a l f a c e nt u r y a f t e r t h e ISR’s fi r s t c ol l i s io n s, a n d w it h a t l e a st quantum sensors target gravitational waves (p10); X-rays go detectors, was 15 years of LHC operations still to come, particle physicists behind the scenes of supernova 1987A (p12); a high-performance a step into o n c e a g a i n fi n d t h e m s e l v e s d e b a t i n g t h e n e x t b e s t s t e p for the computing collaboration forms to handle the big-physics data the unknown fie l d. T r u e t o for m, a s r e c o m m e n d e d b y t h e 2020 u p d a teofh o n s l a u g ht ( p2 2); n e w t w i s t s i n t h e AT OM K I t a l e ( p 74); a n d m or e.

Reporting on international high-energy physics

CERN Courier is distributed Editor Laboratory correspondents Jefferson Laboratory SLAC National Technical illustrator General distribution to governments, institutes Matthew Chalmers Argonne National Kandice Carter Accelerator Laboratory Alison Tovey Courrier Adressage, CERN, and laboratories affiliated Associate editor Laboratory JINR Dubna B Starchenko Melinda Baker Advertising sales 1211 23, ; with CERN, and to Mark Rayner Tom LeCompte KEK National Laboratory SNOLAB Samantha Kuula Tom Houlden e-mail courrier- individual subscribers. Editorial assistant Brookhaven National Hajime Hikino TRIUMF Laboratory Recruitment sales adressage@.ch It is published six times Craig Edwards Laboratory Achim Franz Lawrence Berkeley Marcello Pavan Chris Thomas per year. The views Archive contributor Cornell University Laboratory Spencer K lei n Advertisement Published by CERN, 1211 expressed are not Peggie Rimmer D G Cassel Los Alamos National Lab Produced for CERN by production Kat ie Gr a ha m Geneva 23, Switzerland necessarily those of the Astrowatch contributor DESY Laboratory Rajan Gupta IOP Publishing Ltd Marketing and Tel +41 (0) 22 767 61 11 CERN management. Merlin Kole Till Mundzeck NCSL Ken K i nger y Temple Circus, Temple circulation Laura Gillham, E-mail Fermilab Kurt Nikhef Robert Fleischer Way, Bristol BS1 6HG, UK Jessica Pratten Printed by Warners [email protected] Riesselmann Novosibirsk Institute Tel +4 4 (0)117 929 7481 (Midlands) plc, Bourne, Forschungszentrum S Eidelman Advertising Lincolnshire, UK Advisory board Jülich Markus Buescher Orsay Laboratory Head of Media Jo Allen Tel +44 (0)117 930 1026 , Christine GSI Darmstadt I Peter Anne-Marie Lutz Head of Media (for UK/ display © 2021 CERN Sutton, Claude Amsler, IHEP, Beijing Lijun Guo PSI Laboratory P-R Kettle Business Development advertising) or +44 (0)117 ISSN 0304-288X Philippe Bloch, Roger IHEP, Serpukhov Saclay Laboratory Ed Jost 930 1164 (for recruitment For t y, M i ke L a mont, Yu Ryabov Elisabeth Locci Content and production advertising); e-mail SWISS OFFICIAL DISTRIBUTOR OF EDWARDS Joac h i m Kopp INFN Antonella Varaschin UK STFC Jane Binks manager Ruth Leopold [email protected] Jambe-Ducommun 19 | 2400 Le Locle | CH +41 32 926 26 06 | [email protected] CERN COURIER MARCH/APRIL 2021 5 www.plasmadiam.com

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A ntim Atter FOR PROFESSIONALS AEgIS on track to test free fall of antimatter CERN The AEgIS collaboration at CERN’s scheme allows the time at which 90% of (AD) has reported the are produced to be determined a milestone in its bid to measure the with an uncertainty of around 100 ns. gravitational free fall of antimatter – a Further steps are required before the fundamental test of the weak equivalence measurement of g can begin, explains principle. Using a series of techniques Doser. These include the formation of developed in 2018, the team demon- a pulsed beam, greater quantities of strated the first pulsed production of , and the ability to make it antiatoms, which allows the time at colder. “With only three months of beam which the antiatoms are formed to be time this year, and lots of new equipment known with high accuracy. This is a key to commission, most likely 2022 will be step in determining “g” for antimatter. the year in which we establish pulsed- “Th is is t he first t ime t hat pulsed for- beam formation, which is a prerequisite mation of antihydrogen has been estab- for us to perform a measurement.” lished on timescales that open the door to simultaneous manipulation, by lasers Targeted approach or external fields, of the formed atoms, Following a proof-of-principle measure- as well as to the possibility of applying ment of g for antihydrogen by the ALPHA PERFECT FOR USE the same method to the pulsed formation collaboration in 2013, ALPHA, AEgIS and WITH NHR – QUALITY of other antiprotonic atoms,” says AEgIS a third AD experiment, GBAR, are all spokesperson Michael Doser of CERN. targeting a measurement of g at the 1% NIM CRATES “Knowing the moment of antihydrogen level in the coming years. In contrast to formation is a powerful tool.” AEgIS’s approach, whereby the vertical General relativity’s weak equivalence deviation of a pulsed horizontal beam of principle holds that all particles with the quantities of antihydrogen has enabled Heavy stuff cold antihydrogen atoms will be measured same initial position and velocity should spectroscopic and other properties of The AEgIS i n a n a p pr o x i m a t e l y 1 m-l o n g fl i g ht t u b e, DESIGNED FOR UNIVERSAL LABORATORY USE follow the same trajectories in a gravita- antimatter to be determined in exqui- experiment is GBAR will take advantage of advances in tional field. It has been verified for mat- site detail (CERN Courier March 2018 p30). built around ion-cooling techniques to measure ultra- ter with an accuracy approaching 10–14. Whereas three-body recombination two powerful slow antihydrogen atoms as they fall from SHR Since theories beyond the Standard Model results in an almost continuous anti- superconducting a height of 20 cm. ALPHA, meanwhile, will ALSO AVAILABLE such as supersymmetry, or the existence hydrogen source, in which it is not solenoids each release antihydrogen atoms from a ver- AS NIM-DEVICE: of Lorentz-symmetry violating terms, possible to tag the time of the antia- housing a tical magnetic trap and measure the dis- ULTRA PRECISE HIGH VOLTAGE do not necessarily lead to an equivalent tom formation, AEgIS has employed an Malmberg– tribution of positions when force on matter and antimatter, finding alternative charge-exchange process . they hit the wall – ramping the trap down NHR even the slightest difference in g could between trapped and cooled slowly so that the coldest atoms, which SOURCE MEASURE UNIT + – r e v e a l t h e pr e s e n c e o f q u a nt u m e ffe c t s i n and (a e e bound system). are most sensitive to gravity, come out the gravitational . Indirect argu- Bursts of are accelerated and last. All three experiments have recently ments constrain possible differences to then implanted into a nano-channelled been hooked up to the AD’s ELENA syn- 2 / 4 channels, 2 kV / 6 kV versions below 10–6 g, but no direct measurement silicon target above an electromagnetic chrotron, which enables the production for antimatter has yet been performed trap containing cold antiprotons, where, of very low-energy antiprotons (CERN Electronically switchable polarity due to the difficulty in producing and with the aid of laser pulses, they pro- Courier December 2016 p16). containing large quantities of it. duce a cloud of excited positronium a few Given that most of the mass of anti- Antihydrogen’s neutrality and long millimetres across. This can lead to the nuclei comes from massless that 6 kV channel with electronically switchable modes: up to 2 kV/4 mA, 4 kV/3 mA or 6 kV/2 mA lifetime make it an ideal system in which formation of antihydrogen within sub-μs bind their constituent , phys- to test this and other fundamental laws, timescales, the moment of production icists think it unlikely that antimatter High-precision / very low ripple and noise / high resolution s u c h a s C P T i n v a r i a n c e. T h e fir s t pr o d u c- being defined by the well-known laser experiences an opposite gravitational tion of low-energy antihydrogen, reported firing time and the transit time of pos- ALPHA, AEgIS force to matter and therefore “falls up”. * USB / Ethernet interface in 2002 by the ATHENA and ATRAP collab- itronium toward the antiproton cloud. and GBAR are Nevertheless, precise measurements of orations at the AD, involved a three-body Since the antihydrogen is not trapped in all targeting a the free fall of antiatoms could reveal sub- * + + – – + Integrated (ARM Linux server hardware) with onboard scripting recombination reaction (e + e + p → H + e ) the apparatus, it drifts in all directions measurement tle differences that would open an impor- involving clouds of antiprotons and pos- until it annihilates on the surrounding tant crack in our current understanding. of g at the 1% 4.3“ TFT capacitive touch display (SHR) itrons. Since then, steady progress by the material, producing and pho- AD’s ALPHA collaboration in producing, tons that are detected by a scintillating level in the Further reading *SHR-device only manipulating and trapping ever larger array read out by photomultipliers. The coming years C Amsler et al. 2021 Commun. Phys. 4 19.

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NEWS ANALYSIS

CLOUD expeRImeNt Iodine aerosol production could accelerate Arctic melting

Researchers at CERN’s CLOUD experi- Guard U.S. Kelley, Coast Patrick of aerosol particles from a mixture of ment have uncovered a new mechanism vapours under precisely controlled that could accelerate the loss of Arctic atmospheric conditions, including the sea ice. In a paper published in Science on use of a high-energy beam from the Pro- 5 February, the team showed that aero- ton Synchrotron to simulate cosmic rays sol particles made of iodic acid can form up to the top of the troposphere. Last year, extremely rapidly in the marine bound- the team found that small inhomogenei- ary layer – the portion of the atmosphere ties in the concentrations of that is in direct contact with the ocean. and nitric acid can have a major role in Aerosol particles are important for the driving winter smog episodes in cities climate because they provide the seeds (CERN Courier July/August 2020 p10). The on which cloud droplets form. Marine latest result is similarly important but in new-particle formation is especially a c o m pl e t e l y d i ffe r e nt a r e a, s a y s K i r k b y. important since particle concentrations “In polar regions, aerosols and are low and the ocean is vast. However, clouds have a warming effect because how new aerosol particles form and they absorb radiation other- influence clouds and climate remain wise lost to space and then radiate it relatively poorly understood. back down to the surface, whereas they “Our measurements are the first to reflect no more incoming than show that the part-per-trillion-by- Positive feedback Global iodine emissions at high latitudes have the snow-covered surface. As more sea volume iodine levels found in marine increased threefold during the past seven decades and are likely surface is exposed by melting ice, the regions will lead to rapid formation and to continue to increase in the future as sea ice becomes thinner. increased iodic acid aerosol and cloud- growth of iodic acid particles,” says seed formation could provide a previ- CLOUD spokesperson Jasper Kirkby of sunlight and ozone on molecular iodine ously unaccounted positive feedback that CERN, adding that the particle formation emitted by the sea surface, sea ice and accelerates the loss of sea ice. However, rate is also strongly enhanced by exposed seaweed – may be the main the effect has not yet been modelled so from galactic cosmic rays. “Although driver in pristine marine regions.” we can’t quantify it yet.” most atmospheric particles form from CLOUD is a one-of-a kind experiment sulphuric acid, our study shows that iodic that uses an ultraclean cloud chamber Further reading acid – which is produced by the action of to measure the formation and growth X-C He et al. 2021 Science 371 589.

JINR JINR 503 m storage rings, which will collide the beams at two detectors: the Multi- NICA booster Purpose Detector, designed to study ac h ie ves first beam dense baryonic matter; and the - Physics Detector, designed to study collisions between polarised beams of After seven years of construction at and deuterons. High-density wiring the Joint Institute for Nuclear Research The complex is one of six Russian (JINR) in Dubna, Russia, the Booster “megascience” facilities that are part Our new high-density wiring is a synchrotron at the brand-new NICA of the CREMLIN project, which aims modular option for the Bluefors side- (Nuclotron-Based Ion Collider Facil- to use large-scale science to improve loading XLDsl dilution refrigerator ity) Complex has accelerated its first and strengthen relations and net- beam. On 19 December ions works between European and Russian system that enables a large scale-up were injected into the synchrotron research infrastructures. The CREM- of the experimental wiring, especially and a stable circulation of the beam LIN consortium comprises 19 European for high-frequency signals. It is easy was obtained at an energy of 3.2 MeV, and Russian research infrastructures, a milestone towards NICA’s scheduled including CERN and DESY. Other pro- to install and to maintain. completion in 2022. posed “megascience” facilities included NICA will allow studies of the prop- Megascience A bird’s eye view of the NICA complex in November. in this project are the Super-Charm- erties of nuclear matter in the region of Factory at the Budker Institute of maximum baryonic density. By collid- It uses 2.2 m-long dipole and quadrupole , and the Special-purpose ing heavy gold ions at energies corre- magnets made up of a window-frame Synchrotron-Radiation Source (SSRS-4) sponding to the phase iron yoke and a winding made of a at the NRC Kurchatov Institute. t r ansit ion (4.5 GeV), NICA will access the hollow -titanium supercon- “This is a historic moment for our transition of the quark– ducting cable cooled with a two-phase laboratory and a great milestone in the into , complementing studies at h e l iu m flo w. B e a m s w i l l t h e n b e trans- realisation of our flagship megascience higher energy colliders such as the LHC. ported to a separate ring surround- project – we have to thank the CREMLIN The NICA booster is a 211 m circum- ing the booster, the “nuclotron”, and grant programme for helping us in these ference superconducting synchrotron accelerated to the GeV range. Finally, challenges,” says Vladimir Kekelidze, that will accelerate beams to 500 MeV. beams will be injected into two identical the NICA project leader.

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NEWS ANALYSIS NEWS ANALYSIS

Quantum technologies Chinese particle physics, emboldening for the 20 kilotonne liquid- the country to explore major projects such detector 700 m beneath the Dashi hill in as a circular electron– collider. Guangdong was completed at the end Quantum sensing for particle physics “One important lesson we learnt from of 2020. The construction of a concrete Daya Bay is that we should just go ahead water pool is the step. AION/RAL AION/RAL

A particle physics-led experiment called jects involving UK institutes are under and do it if it is a good project, rather Lab Kaltschmidt/Berkeley R The detector concept that the three

AION (Atomic Interferometric Observa- way thanks to the UKRI scheme. One, than waiting until everything is ready. experiments used to uncover θ13 was tory and Network) is one of several multi- led by experimental particle We convinced our government that we designed by the Double Chooz collab- disciplinary projects selected for funding Ruben Saakyan of University College could do a great job, that world-class jobs oration. Thierry Lasserre, one of the by the UK’s new Quantum Technologies London, will use ultra-precise B-field need to be international, and that particle experiment’s two founders, recalls that for Fundamental Physics programme. mapping and spectrometry physics is fundamental and influential, it was difficult, 20 years ago, to convince The successful projects, announced in to determine the absolute neutrino mass and deserves to be supported.” the community that the measurement January following a £31 million call for in tritium beta-decay beyond the 0.2 eV The experiment has also paved the was possible at reactors. “It should not be proposals from UK Research and Innova- sensitivity projected for the KATRIN way for China to build a successor, the for g o t t e n t h a t s i g n i fic a nt e x p e r i m e nt a l tion (UKRI), will exploit recent advances experiment. Others include the use of new Jiangmen Underground Neutrino Obser- efforts were also undertaken in Angra in quantum technologies to tackle out- classes of detectors and coherent quan- vatory (JUNO), for which Wang is now dos Reis, Braidwood, Diablo Canyon, standing questions in fundamental phys- t u m a m pl i fie r s t o s e a r c h for h id d e n s truc- spokesperson. JUNO will tackle the Krasnoyarsk and Kashiwazaki,” he says. ics, and . ture in the vacuum state; the development neutrino mass hierarchy – the ques- “Reactor neutrino detectors can now be UKRI and university funding of about of ultra-low-noise quantum electronics tion of whether the third neutrino mass used safely, routinely and remotely, and £10 million (UKRI part £7.2 million) to underpin searches for axions and other eigenstate is the most or least massive some of them can even be deployed on the will enable the AION team to prepare light hidden particles; quantum simula- of the three. An evolution of Daya Bay, surface, which will be a great advantage the construction of a 10 m-tall atomic tors to mimic the extreme conditions of the new experiment will also measure a for non-proliferation applications.” The interferometer at the the early and black holes; and deficit of electron antineutrinos, but at next steps in reactor-neutrino physics, to explore ultra-light and the development of quantum-enhanced a distance of 53 km, seeking to resolve he explains, will now involve an extraor- provide a pathway towards detecting superfluid technologies for cosmology. fast and shallow oscillations that are dinary miniaturisation to cryogenic gravitational waves in the unexplored The UKRI call is part of a global effort e x p e c t e d t o d i ffe r d e p e n d i n g o n t h e neu- detectors as small as 10 grams, which mid-frequency band ranging from sev- to develop quantum technologies that trino mass hierarchy (CERN Courier July/ Transformative Antineutrino detectors submerged in ultrapure take advantage of the much larger cross eral mHz to a few Hz. The setup will use could bring about a “second quantum August 2020 p32). Excavation of a cavern water at one of Daya Bay’s experimental sites. section of coherent neutrino scattering. lasers to drive transitions between the “AION is a uniquely interdisciplinary Physics in revolution”. Several major international ground and excited states of a cloud of mission that will harness cold- the pipeline public and private initiatives are under c old s t ront iu m at om s i n f re e f a l l, e ffe c- quantum technologies to address key AION’s initial 10 m way. Last autumn, CERN launched its own tively acting as beam splitters and mir- issues in fundamental physics, astro- stage is hoped to quantum technologies initiative (CERN rors for the atomic de Broglie waves (see physics and cosmology that can be real- be followed by Courier September/October 2020 p47). figure). Ultralight dark matter and exotic ised in the next few decades,” says AION 100 m and km-scale “With the application of emerging light bosons would be expected to have principal investigator facilities. quantum technologies, I believe we have d i ffe r e nt i a l e ffe c t s o n t h e a t o m i c transi- of , who is also a an opportunity to change the way we tion frequencies, while a passing gravi- member of the CMS collaboration. “The search for answers to some of the biggest tational wave would generate a strain in A ION pr oj e c t w i l l a l s o s i g n i fic a nt l y c on- mysteries of the universe,” said Mark the space through which the atoms fall tribute to MAGIS, a 100 m-scale partner Thomson, executive chair of the UK’s freely. Either would create a difference experiment being prepared at Fermilab, Science and Technology Facilities Coun- between the phases of atomic beams fol- and we are exploring the possibility of cil. “These include exploring what dark lowing different paths – the greater their utilising a shaft in the UK or at the LHC matter is made of, finding the absolute separations, the greater the sensitivity for a similar second 100 m detector.” mass of and establishing how of the experiment. Six other quantum-technology pro- quantum mechanics fits with gravity.”

neutrinos this conclusively the following spring. The experiments also failed to dispel the Farewell Daya Bay, hello JUNO reactor–antineutrino , whereby obser ved neutrino flu xes are a few per- In October 2007, neutrino physicists Daya Bay m a t r i x, w h i c h q u a nt i fie s l e p t o n m i x i n g, cent lower than calculations predict. This broke ground 55 km north-east of Hong has had a with only an upper limit available. Today, has triggered a slew of new experiments Kong to build the Daya Bay Reactor it is the best known angle by some mar- located mere metres from nuclear- transformative Neutrino Experiment. Comprising eight gin, and the knowledge that it is nonzero reactor cores, in search of evidence for 20-tonne liquid-scintillator detectors effe c t on has opened the door to measuring oscillations involving additional, sterile sited within 2 km of the Daya Bay nuclear Chinese leptonic CP violation at long-baseline light neutrinos. As the Daya Bay exper- plant, its aim was to look for the dis- particle physics accelerator-neutrino experiments. iment’s detectors are dismantled, after appearance of electron antineutrinos Daya Bay was one of a trio of exper- almost a decade of data taking, the three as a function of distance to the reactor. iments located in close proximity to can reflect on the rare This would constitute evidence for mix- nuclear reactors, along with RENO in privilege of having pencilled the value ing between the electron and the third South Korea and Double Chooz in , of a previously unknown parameter into neutrino mass eigenstate, as described which were responsible for this seminal the Standard- Model Lagrangian.

by the parameter θ13. Back then, θ13 measurement. Double Chooz published Founding Daya Bay co-spokesperson

was the least well known angle in the the first hint thatθ 13 was nonzero in 2011, Yi-Fang Wang says the experiement s Pontecorvo–Maki–Nakagawa–Sakata before Daya Bay and RENO established has had a transformative effect on

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AstrowAtch Lifting the veil on supernova 1987A

On 23 February 1987 astronomers around NRAO/AUI/NSF; NASA/ESA ALMA; the world saw an extremely bright super- nova, now called SN1987A. It was the closest supernova observed for over 300 years and was visible to the naked eye. The event was quickly confirmed to be the result of the collapse of “Sanduleak –69 202”, a blue supergiant star in the . As the first nearby supernova in the era of mod- ern astronomy, SN1987A remains one of the most monitored objects in the sky. A p a r t f r o m c o n fi r m i n g s e v e r a l i m p or t a nt theories, such as being the source of the observed optical emis- sion, the supernova also raised a number of questions that remain unanswered. The most important is: where is the remnant of the progenitor star? When Compromise is Not an Option. Despite several false detection claims in the past, evidence is mounting that Sanduleak –69 202 collapsed into a High-Performance Digitizers for star that is becoming more visible as the dust around it starts to settle. A new analysis by researchers in and Missing link A hot “blob” (inset) revealed by X-rays in the dusty core of SN1987A could be the location of the Big Physics Applications Japan based on high-energy X-ray data missing formed by the collapse of its progenitor star. The red area shows dust and cold gas observed from the Chandra and NuSTAR space tele- at radio wavelengths by ALMA; the green and blue hues, recorded by Hubble and Chandra, show the collision Digitizers from Teledyne SP Devices utilize patented scopes adds the latest support to this idea. between the expanding shock wave and material around the supernova. Even before the optical light from calibration technology, the latest data converters, and SN1987A was detected, several neutrino SN1987A. Close to the centre, they found r e g i o n. W h e r e a s m o d e l s for b o t h i d e a s fit state-of-the-art FPGAs in order to achieve an unrivaled detectors around the world saw a burst a bright “blob” structure, the emission the spectral data, the pulsar wind nebula of neutrinos. The brightest one was from which appeared to be compat- is favoured because the shock emission combination of high resolution and sampling rate. Their observed by Japan’s Kamiokande II detec- ible with radio emission from parti- would not be expected to look like this versatility makes them ideal for applications such as tor, which detected a total of 12 antineu- cles accelerated by a neutron star, also for such a young remnant. trinos approximately three hours before called a pulsar wind nebula. Although The reason why this neutron star has beam position monitoring, Thomson scattering plasma t h e fi r s t o p t i c a l l i g ht r e a c h e d E a r t h. The the researchers could not exclude local escaped previous observations in optical 44 diagnostics, and more. detection of antineutrinos seemed to con- heating from Ti produced during the or soft X-ray energies is likely absorption fi r m t h e or e t i c a l pr e d i c t i o n s for a s t a r the supernova as the source, the results pro- by cold dust emitted during the super- size of Sanduleak –69 202: namely that v ided t he first hint t hat t he blob houses nova, which appears to still absorb a Supported features include: it should collapse into a neutron star, a young neutron star. large part of the synchrotron emission and emit large numbers of neutrinos observed in X-rays, especially at lower • Up to 10 GSPS sampling rate with 14 bits resolution while doing so. The optical light arrives Wind power energies. But the dust is expected to start later because it is only produced when Inspired by the ALMA results, Emanuele to heat up during the coming decades, • Open FPGA for custom real-time signal processing the shock waves from the collapse reach Greco from the University of Palermo and thereby becoming transparent to lower the surface of the star. Since the newly coworkers started to study the same energy emission. Greco and colleagues • Multiple form factors including MTCA.4, PXIe, and PCIe formed neutron star would be expected to region using X-ray data from Chandra and predict that, if the emission is indeed emit large amounts of energy at various NuSTAR taken during 2012, 2013 and 2014. induced by a neutron star, it will become • Multi-channel synchronization capabilities wavelengths, one might assume it would They found that the detected soft X-ray visible in the soft X-ray regime by 2030 be relatively easy to detect. However, no em ission (0.5–8 keV) was compatible with Chandra. • White Rabbit synchronization (MTCA.4 only) signs were found in follow-up searches with thermal emission produced in the Although astronomers have just two • Peer-to-peer streaming to GPU (PCIe only) over the past three decades, leading to remnant shock waves of the supernova observational hints that Sanduleak –69 much speculation about the fate of this event with the circumstellar medium. 202 did, as it should according to theory, • Application-specific firmware shortens design time star and its surrounding medium. However, at higher energies (10–20 keV) The results collapse into a neutron star, it appears that T h e fi r s t s i g n s o f t h e s t e l l a r r e m n ants the emission was clearly non-thermal provided the a f t e r 3 4 y e a r s o f s e a r c h i n g w e w i l l fi n a l l y of SN1987A came from radio observations in nature. Describing their findings in first hint understand what happened in SN1987A. by the Atacama Large Millimeter/sub- a preprint posted in January, the group that the millimeter Array (ALMA) in Chile in 2019. studied the two possible sources for such Further reading A group led by Phil Cigan from Cardiff emission: synchrotron emission from a blob houses P Cigan et al. 2019 ApJ 886 51. University in the UK used ALMA data at pulsar wind nebula and synchrotron a young E Greco et al. 2021 arXiv:2101.09029 various frequencies to study the core of emission produced in shock waves in the neutron star (accepted by ApJL). Learn more on our www.spdevices.com 12 CERN COURIER MARCH/APRIL 2021

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cosmic microwave background. of the spectrum of iron – the which cannot reconcile recent Data from the Square Kilometre rarest and heaviest measurements of neutron-rich Array, which may begin to be characterised so far – nuclei. 32 had been thought to be construction in South Africa and unexpectedly resembles the light a “” number of Australia as early as this year, elements more than the heavier that completes a nuclear CERN-PHOTO-202101-011-5 could allow the detection of GWs ones (Phys. Rev. Lett. 126 041104). shell and results in a slimmer with frequencies in the MHz and “Iron is an atomic-number nucleus with a greater binding GHz regime, far beyond the reach frontier that won’t be crossed energy than its neighbours. of LIGO, VIRGO or KAGRA, write for years to come,” said AMS-02 However, researchers using the the pair. spokesperson Sam Ting. Collinear Resonance Ionisation apparatus found BASE’s Jack Devlin alongside the Industrial innovation Snowmass postponed that potassium-52, which has experiment’s superconducting magnet. DESY v ir t ually k ic ked-off a new The summer study of the 2021 33 neutrons, was not observably “innovation factory” late last Snowmass exercise has been fatter than the supposedly Unorthodox ALP antenna year, allowing detailed planning postponed one year to July 2022, magic potassium-51, which The Antibaryon for the building’s infrastructure due to the ongoing COVID-19 boasts 19 protons and 32 Symmetry Experiment (BASE) to begin. The facility will pandemic. The community neutrons (Nat. Phys. doi:10.1038/ collaboration at CERN’s offer laboratories and spaces exercise, which will plot a course s41567-020-01136-5). Antiproton Decelerator has for start-ups, scientists and for US particle physics over the demonstrated an ingenious new established corporations, in coming decade, was originally Rival probes approach Mars way to search for -like the hope of building strong ties planned for this summer. First As the Courier went to press, particles (ALPs, see p25). The between research and industry. convened in 1982 in the Colorado probes from the United Arab team looked for unexpected Construction is proposed to mountain resort of the same Emirates (UAE), China and the US electrical signals in doughnut- begin in 2023, with completion name, Snowmass studies have shaped superconducting aimed for 2025. Science City been produced on numerous

coils that are usually used to Bahrenfeld, a new district in occasions throughout the years, CNSA/PEC precisely measure the oscillation Hamburg, , where most recently in 2013. More frequencies of individual trapped the facility will be built, is than 1500 letters of intent – an antiprotons. Faint signals, which also home to DESY’s PETRA III unusually large number – have might easily be mistaken for synchrotron X-ray source. already been submitted across noise, could in fact be caused by 10 “Snowmass frontiers”, ALPs interacting with the strong Cosmic rays get weirder from the energy frontier to of the Penning Results from the Alpha Magnetic community engagement. trap. The collaboration set a new Spectrometer (AMS-02) on the upper laboratory limit for the International Space Station have Novel collider concept coupling between and thrown up another surprise that Peking University physicists The first image of Mars sent by China’s ALPs within a narrow mass range may shed light on the processes urge the community to consider Tianwen-1 probe. around 2.79 neV, demonstrating that create and accelerate cosmic the merits of a novel electron– the feasibility of using Penning rays. Last year, the collaboration (arXiv:2010.15144). were approaching the Red Planet traps to search for cold dark reported unexpected differences Collisions between different – a testament to the growing matter (Phys. Rev. Lett. 126 041301). in the rigidity (momentum species of could reduce desire of many nations to develop physics backgrounds for studies space technology and explore

Dark-age detectors NASA of charged-lepton flavour the solar system. The UAE’s Valerie Domcke (CERN) and violation and Higgs-boson Hope – t he A rab world’s first Camilo Garcia-Cely (DESY) properties, and the asymmetric interplanetary spacecraft – will have proposed using radio nature of the collisions could remain in orbit and make the telescopes to detect high- be used to control troublesome first map of Mars’ surprisingly frequency gravitational waves backgrounds caused by muon sparse atmosphere. China’s (GWs) from the “dark ages” – decays inside the accelerator, Tianwen-1 will study the planet the period in the early universe argue the authors. The preprint for several months before between atoms forming and proposes 10 GeV electron and dropping a lander, potentially stars igniting (Phys. Rev. Lett. 126 The AMS-02 detector. muon beams initially, and making China only the 021104). As a result of embedding upgrades culminating in a second nation in the world to classical electrodynamics in divided by charge) dependence of TeV-scale muon–muon collider. successfully land a robot vehicle general relativistic spacetime, the primary-cosmic-ray spectra on another world, after the US. it is expected that GWs can be of light elements (helium, carbon 32 is not a magic number The US rover Perseverance will converted into photons in the and oxygen) and heavy elements A study at CERN’s ISOLDE facility descend to the planet’s surface in presence of magnetic fields, (neon, magnesium and silicon). has exposed shortcomings search of signs of habitability and leading to a distortion of the A newly published measurement in the best nuclear models, evidence of microbial life.

CERN COURIER MARCH/APRIL 2021 15

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Reports from the experiments 1000mm/s Linear Actuators ATLAS Magnetically-coupled or bellows sealed options Evidence for Dalitz decays of the Higgs

30 Bkg Bkg + H → γγ Bkg + H → γγ + Sig (μ = 1.5) data 20

Σ weights/GeV 10 ATLAS preliminary √s = 13 TeV, 139 fb–1

In(1 + S90/B90) weighted sum 0 4

0 Σ w – Bkg

110 120 130 140 150 160

mγ [GeV] Fig. 1. of the γ system, with every data event contributing a category-dependent weight representing the expected sensitivity of the H → γ signal. The data are shown as purple dots, while the lines show the signal and background functions as obtained by a fit. Rare decay A candidate H → μ+μ–γ decay in the ATLAS detector.

Evidence for the decay of the Higgs boson decays. Special treatment was needed The sensitivity to the H → γ signal to a photon and a low-mass electron or in particular for the electron channel: was increased by separating events in muon pair, propagated predominantly a dedicated electron trigger was devel- mutually exclusive categories based on by a virtual photon (γ*), H → γ*γ → γ, o p e d a s we l l a s a s p e c i fic id e nt i fic at ion lepton types and event topologies. ATLAS

has been obtained at the LHC. In a recent algorithm. The predicted m spectrum reports evidence in data for a H → γ conference note, the ATLAS collabora- rises steeply towards lower values, with signal emerging over the background tion reports a 3.2σ excess over back- a kinematic cutoff at twice the final- w it h a sig nificance of 3.2σ (see fig ure). ground of H → γ decay candidates with state lepton mass. At such low elec- The Higgs boson production cross-

dilepton mass m < 30 G eV. tron–positron invariant masses, and section times H → γ branching fraction,

The measurement of rare decays of the given the large transverse momentum measured for m < 30 GeV, amounts to +2.8 Higgs boson is a crucial component of of their system, the electromagnetic 8.7 –2.7 fb. It corresponds to a signal the Higgs-boson physics programme at showers induced by the electron and the strength – the ratio of the measured the LHC, since they probe potential new positron in the ATLAS calorimeter can times branching fraction interactions with the Higgs boson intro- merge, requiring a specially developed to the Standard Model prediction – of duced by possible extensions of the Stand- Measurement reconstruction. Furthermore, a ded- 1.5 ± 0.5. Meanwhile, ATLAS has also ard Model. The H → γ “Dalitz” decay is icated identification algorithm was extended the invariant-mass range of particularly interesting in this respect as of rare decays developed for these topologies, and its the lepton pair for the related Higgs- Designed in collaboration with Particle Accelerators to provide it is a loop process and the three-body of the Higgs efficiency was measured in data using boson decay into a photon and a Z boson final state a l lows t he CP st r uct ure of t he boson is photon detector-material conversions to lower masses, opening the door to precise, high speed actuation of beamline diagnostics. Higgs boson to be probed. However, the a crucial at low radius into an electron–positron future studies of three-body Higgs- small expected signal-to-background component pair from Z → γ events. boson decays and investigations of its ratio and the typically low dilepton invar- The signal extraction is performed underly ing CP st r uct ure. of the Higgs- iant mass make the search for H → γ by searching in the γ invariant mass boson physics highly challenging. (mγ) range between 110 and 160 GeV for Further reading The analysis performed by ATLAS programme a narrow signal peak over smooth back- ATLAS Collab. 2021 ATLAS-CONF-2021-002. + – + – Contact [email protected] for more information searched for H → e e γ and H → μ μ γ at the LHC ground at the mass of the Higgs boson. ATLAS Collab. 2020 Phys. Lett. B 809 135754. www.uhvdesign.com CERN COURIER MARCH/APRIL 2021 17

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ENERGY FRONTIERS ENERGY FRONTIERS

0 – + CMS parameter. The f s/fd ratio was measured m e nt s o f t w o i m p or t a nt d e c a y s, B s → Ds π The results a slight dependence on the centre-of- 0 in previous publications through semi- a n d B s → J/ψ φ. These are golden channels reduce the m a s s e n e r g y o f pr o t o n–pr o t o n c ol l i s io n s leptonic decays, hadronic decays with for mixing and CP violation measure- uncertainty on (figure 1). The results are used in this Deep learning tailors supersymmetry searches 0 D and hadronic decays with J/ψ ments in t he B s sector. work to update the previous branch- fs/fd by roughly mesons in the final state. Some of these The results reduce the uncertainty i n g-f r a c t ion m e a s u r e m e nt s o f a b o ut 50 a factor of 0 Supersymmetry is a popular extension t u r i n g t h e c o m pl e x it y o f t h e e v e nt s t h a n measurements are only sensitive to the on fs/fd by roughly a factor of two for d i ffe r e nt B s decay channels, significantly CMS preliminary 137 fb–1 (13 TeV) two, yielding of the Standard Model (SM) that has the 2 is possible using predetermined search pr o d u c t o f t h e f r a g m e nt a t io n f r a c t io n a n d collisions at 7 TeV, and a factor of 1.5 i m pr o v i n g t h e i r pr e c i s io n, a n d b o o s t i n g 1400 ∼± ∼0 ~~ 0 ~ 10 pp  , BR(~ ) = 1, m = 0.95m ± + 0.05m 0 potential to resolve several open ques- → χ χ → ν χ → ~ ~χ ~χ the branching fractions. This new work for collisions at 13 TeV, yielding a pre- a precision of several searc hes for new physics. 1 2 2 1 1 regions: parametric machine learning. observed ± 1σ (NN) NLO–NLL excl. tions in particle physics. As a result of a 1200 theory T h e a i m i s t o a c h i e v e t h e m a x i m u m s e n- analyses these results simultaneously, cision of about 3%. They also confirm about 3% expected ± 1σ (NN) 1709.05406 obs. postulated new symmetry between fer- experiment s it i v it y for a n y p a r a m e t e r c h oi c e n a t u r e o b t a i n i n g a pr e c i s e m e a s u r e m e nt o f f s/fd t h e d e p e n d e n c e o f f s/fd on the transverse Further reading expected (SR) 10 0 mions and bosons, the theory predicts a 1000 might have made, as supersymmetry is as well as branching fraction measure- m o m e nt u m o f t h e B s m e s o n, a n d i n d i c a t e LHCb Collab. 2021 LHCb-PAPER-2020-046. “” for each SM particle. The not one model, but a class of models. 800 lightest of these new particles could be Variations in the masses of the super- ALICE 14 U P C s a t 5.02 TeV. T h e J/ψ is reconstructed 1 + –

[GeV]   1 ALICE Pb + Pb Pb + Pb + J/ √s = 5.02 TeV what makes up dark matter, while addi- 0 partners can substantially modify the → ψ NN using the dilepton ( ) a n d pr o t o n–a nt i-

∼ χ 600 tional new could resolve m observable signatures. Parametric neural ALICE shines ALICE coherent J/ψ channels, while for the ψ′, 12 impulse approximation + – + – the question of why the Higgs boson has 400 n e t w or k s w e r e t r a i n e d t o fi n d c h a r g i n o s the dilepton and the   π π decay –1 STARLIGHT a re l at ive ly low m a ss. M a ny sea rc hes for 10 and with the unknown mass light inside EPS09 LO (GKZ) channels are studied. These data com- supersymmetry have already been per- parameters added as input variables to 10 LTA (GKZ) plement the ALICE measurement of the

200 95% CL upper limit on cross section (fb) formed by the ATLAS and CMS collabora- the training. The network can evalu- IIM BG (GM) coherent J/ cross-section at forward lead nuclei IPsat (LM) ψ –2 t i o n s, b ut m o s t h a v e fo c u s e d o n s t r o n g l y 0 10 ate the data at fixed values of the mass 8 BGK-I (LS) rapidity, –4 < y < –2.5, pr o v i d i n g s t r i n g e nt interacting superpartners that could be 200 400 600 800 1000 1200 1400 parameters, effectively performing a An ultra-relativistic electromagnetically GG-HS (CCK) c o n s t r a i nt s o n nu c l e a r g lu o n s h a d o w i n g. dy (mb)

/ b-BK (BCCM) ∼ ± = ∼0 very heavy. It is possible, however, that m m [GeV] dedicated search for a signal with given charged projectile carries a strongly con- σ The nuclear gluon shadowing fac- χ1 χ2 6 electroweak production of supersymmet- masses in t he data (fig ure 1). t racted field t hat can be t hought of as a d tor of about 0.65 at Bjorken-x between –3 –3 ric particles is the dominant or only source Fig. 1. Observed and expected exclusion limits for a model of The parametric neural network, flu x o f q u a s i-r e a l p h o t o n s. T h i s i s k now 4 0.3 × 10 and 1.4 × 10 is estimated from of superpartners accessible at the LHC. electroweak supersymmetry with slepton-mediated t o g e t h e r w it h a n e w o p t i m i s e d e v e nt bi n- a s t h e e q u i v a l e nt-p h o t o n a p pr o x i m a t i o n, t he c omp a r i s on of t he mea su re d c o he r- The unprecedented data volume of and decays. Results using neural networks (NN) are n i n g o f t h e o t h e r e v e nt c a t e g or ie s, m a k e s and was proposed by Fermi and later ent J/ψ cross-section with the impulse 2 LHC Run 2 provides a unique opportu- compared with the expected limits based on the search-region this analysis the most powerful search d e v e l o p e d b y We i z s ä c k e r a n d W i l l i a m s. approximation at midrapidity, which nity to search for rare processes such as (SR) approach, and the previous CMS analysis (green). for and neutralinos carried In practice, this means that the proton implies moderate nuclear shadowing. 0 electro weak production of supersym- out by the CMS collaboration so far. The or lead (Pb) beams of the LHC, moving T h e m e a s u r e d r a pid it y d e p e n d e n c e o f t h e metric particles. A recent result from the the momentum imbalance, can be used neural network alone results in a sensi- at ultra-relativistic energies, also carry –4 –3 –2 –1 01coherent cross-section is not completely y CMS collaboration uses the Run-2 dataset to define a set of discriminating varia- tivity boost that ranges from 30% to more a q u a s i-r e a l p h o t o n b e a m, w h i c h c a n b e reproduced by models in the full rapidity to search for the superpartners of the bl e s s e n s it i v e t o c h a r g i n o a n d n e ut r a l i n o than 100%. Substantial improvements used to look inside protons or nuclei. Fig. 1. Measured differential cross section of the coherent J/ψ range. The leading twist approximation electroweak bosons, called charginos and production. These variables are used to occur for models where the decay of the The ALICE collaboration is in this way photoproduction in Pb–Pb UPC events as a function of rapidit y. o f t h e G l a u b e r–G r i b o v s h a d o w i n g (LTA- neutralinos. Events with three or more assign the selected events into several charginos and neutralinos are mediated using the LHC as a photon–hadron col- The error bars (boxes) show the statistical (s ystematic) GKZ) and the energy-dependent hot-spot charged , or two leptons of the search regions that address different by the superpartners of leptons. The lider, shining light inside lead nuclei uncertainties. Theoretical calculations are also shown. The grey m o d e l (G G -HS (C C K)) g i v e s t h e b e s t o v e r- s a m e c h a r g e, w e r e a n a l y s e d. S u c h e v e nt s possible signals of the production and i m pr o v e m e nt s b e c o m e e v e n l a r g e r w h e n to measure the photoproduction of band represents the uncertainties of the EPS09 LO calculation. a l l d e s c r i p t i o n o f t h e r a pi d it y d e p e n d e n c e are relatively rare in the SM, and, if they decay of supersymmetric particles. Mak- the mass splitting between sleptons and charmonia and provide constraints on but shows tension with data at semi-for- exist, charginos and neutralinos are pre- i n g s u c h a m u l t i v a r i a t e bi n n i n g o p t i m a l the chargino is relatively small. The data nuclear shadowing. enon known as nuclear shadowing that ward rapidities 2.5 < |y| < 3.5 (fi g u r e 1). T h e d ic t e d t o c r e a t e a n e x c e s s o f e v e nt s w it h in every corner of phase-space, and for s h o w n o e v i d e n c e for e l e c t r o w e a k s u p e r- The intensity of the electromagnetic w a s fi r s t o b s e r v e d b y t h e E u r o p e a n M uon data might be better explained with a these topologies. Supersymmetric events any possible manifestation of supersym- partner production, and chargino masses field, and the corresponding photon flux, Collaboration at CERN in 1982 by compar- model where shadowing has a smaller are also expected to have an apparent metry, is a challenging task. up to 1450 GeV, compared to 1150 GeV in i s pr o p or t i o n a l t o t h e s q u a r e o f t h e e l e c- ing the structure functions of iron and e ffe c t a t Bj or k e n x ~ 10–2 or x ~ 5 ∙ 10–5, c or- imbalance in transverse momentum, Events with three and/or earlier CMS searches for this scenario, tric charge. This type of interaction is in the deep inelastic scattering responding to t his rapidit y range. because the lightest supersymmetric muon s prov ide t he bu l k of t he s e n sit iv- are e xcluded at 95% confidence. therefore greatly enhanced in the colli- of . The ratio of the ψ′ t o J/ψ cross-sections par t ic le should ev ade detect ion. Cor re- ity by striking the best balance between s i o n s o f l e a d i o n s (Z = 82). Ultra-peripheral Heavy-vector– photoproduction at midrapidity is consistent with the ratio lations between the multiple leptons in signal purity and yields. A novel search Further reading collisions (UPCs), in which the impact measurements provide a powerful tool of photoproduction cross sections meas- t h e e v e nt s, a n d b e t w e e n t h e l e p t o n s a n d approach is used that aims at better cap- CMS Collab. 2021 CMS-PAS-SUS-19-012. parameter is larger than the sum of the t o s t u d y p o orl y k n o w n g lu o n-s h a d o w i n g u r e d b y t h e H1 a n d L HC b c ol l a b or a t io n s, radii of two Pb nuclei, are a particularly effects at low x. The scale of the four- with the leading twist approximation LHCb useful way to study photonuclear colli- momentum transfer of the interaction predictions for Pb–Pb UPCs as well as 0 s io n s. He r e, p u r e l y h a d r o n ic i nt e r a c t io n s corresponds to the perturbative regime w it h t h e A L IC E m e a s u r e m e nt a t for w a r d Precision leap for B s fragmentation and decay a r e s u p pr e s s e d, d u e t o t h e s h or t r a n g e o f o f Q C D i n t h e c a s e o f h e a v y c h a r m o n iu m rapidities. This to the conclusion the strong force, and photonuclear inter- states. The gluon shadowing factor – the t h a t s h a d o w i n g e ffe c t s a r e s i m i l a r for 2S 0 How likely is it for a b quark to partner Fig. 1. The fraction of B s mesons to be actions dominate. The photoproduction ratio of the nuclear PDF to the proton (ψ′) and 1S (J/ψ) states. itself with an s quark rather than a light 0.30 produced, relative to the number of B0 of vector mesons in these reactions has a PDF – can be evaluated by measuring In LHC Run 3 and 4, ALICE ex pects to LHCb d or u quark? This question is key for mesons, is shown as a function of the c l e a n e x p e r i m e nt a l s i g n a t u r e: t h e d e c a y the nuclear suppression factor, defined collect a 10-times-larger data sample understanding the physics of fragmenta- proton–proton collision energy. products of the are the only to be the square root of the ratio of the t h a n i n R u n 2, t a k i n g d a t a i n a c o nt i nu o u s tion and decay following the production sig na ls in a n ot her w ise empt y detec tor. coherent vector–meson photonuclear mode, and thus with higher efficiency. 0 of a b quark in proton–proton collisions. d fragmentation fraction of a b quark to a Bs Coherent heavy-vector–meson photo- production cross section on nuclei to U P C p h y s i c s w i l l pr o fit f r o m t h i s b y l arge /f 0.25

0 s 0 In addition, the number of B s mesons f or a – is thus a key parameter at pr o d u c t i o n, w h e r e i n t h e p h o t o n i nt e r a c t s the photonuclear cross-section in the integrated luminosity as well as lower to be produced, formed by a pair of b the LHC. So far it has been measured with consistently with all the in a i m p u l s e a p pr o x i m a t io n t h a t i s b a s e d o n systematic uncertainty connected to the and s quarks, is required for measuring limited precision and has been the dom- nu c l e u s, i s o f p a r t i c u l a r i nt e r e s t b e c a u s e the exclusive photoproduction measure- m e a s u r e m e nt a n d w i l l b e a bl e t o pr o v i d e 0 its decay probabilities, most notably to inant systematic uncertainty for most Bs o f it s c o n n e c t i o n w it h g lu o n d i s t r i b ut i o n ments w it h a proton target. the shadowing factor differentially in fina l st ates t hat a re sensit ive to physics 0.20 branching fractions. Now, however, the functions (PDFs) in protons and nuclei. The ALICE collaboration recently sub- w ide Bjorken-x inter v als. beyond the Standard Model, such as the 7 8 9 10 11 12 13 LHCb collaboration has, in a recent publi- At low Bjorken-x values, gluon PDFs are mitted for publication the measurement 0 + – Bs → μ μ decay. cation, combined the efforts of five differ- significantly suppressed in the nucleus of the coherent photoproduction of J/ψ Further reading proton–proton collision energy [TeV] s The knowledge of fs/fd – the ratio of the ent analyses with information on this r e l a t i v e t o f r e e pr o t o n PDFs – a p h e n o m- and ψ′ at midrapidity |y| < 0.8 in Pb–Pb ALICE Collab. 2021 arXiv:2101.04577.

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Reports from events, conferences and meetings TOOLS 2020 Tooling up to hunt dark matter

The past century has seen ever stronger Maverik NASA/CXC/CfA/M links forged between the physics of ele- mentary particles and the universe at large. But the picture is mostly incom- plete. For example, numerous observa-

et al et

tions indicate that 87% of the matter Clowe Arizona/D WFI/Magellan/U. ./STScl/ESO of the universe is dark, suggesting the existence of a new matter constituent. Given a plethora of dark-matter candi- dates, numerical tools are essential to advance our understanding. Fostering cooperation in the development of such software, the TOOLS 2020 conference attracted around 200 phenomenologists

and experimental physicists for a week- al. et long online workshop in November. The viable mass range for dark matter spans 90 orders of magnitude, while the uncertainty about its interaction cross section with ordinary matter is even larger (see “Theoretical landscape” figure). Dark matter may be new parti- cles belonging to theories beyond-the- Standard Model (BSM), an aggregate of Dark modelling The famous Bullet Cluster, in which the mass distribution of two colliding clusters (blue) and new or SM particles, or very heavy objects the distribution of baryonic matter (pink) are overlaid on optical data showing the positions of the galaxies. such as primordial black holes (PBHs). On the latter subject, Jérémy Auffinger Theoretical software – a trend mapped and encour-

(IP2I Lyon) updated TOOLS 2020 delegates ArinaC landscape aged by the TOOLS conference series, on codes for very light PBHs, noting that Possible interaction initiated by Fawzi Boudjema (LAPTh “BlackHawk” is the first open-source cross sections are Annecy) in 1999, which has brought code for Hawking-radiation calculations. sketched versus the community together every couple mass for viable of years since. Flourishing models dark-matter Three continuously tested codes Weakly interacting massive particles candidates. currently dominate generic BSM dark- (WIMPs) have enduring popularity matter model computations. Each allows as dark-matter candidates, and are for the computation of relic density from amenable to search strategies ranging freeze-out and predictions for direct and from colliders to astrophysical obser- indirect detection, often up to next-to- vations. In the absence of any clear leading corrections. Agreement between detection of WIMPs at the electroweak them is kept below the percentage s c a le, t he nu m b e r o f m o d e l s h a s flo u r- level. “micrOMEGAs” is by far the most ished. Above the TeV scale, these include used code, and is capable of predicting general hidden-sector models, FIMPs observables for any generic model of (feebly interacting massive particles), WIMPs, including those with multiple SIMPs (strongly interacting massive ments across the globe. dark-matter candidates. “DarkSUSY” is particles), super-heavy and/or com- For each dark-matter model, astro- more oriented towards supersymmetric posite candidates and PBHs. Below the particle physicists must compute the theories, but it can be used for generic GeV scale, besides FIMPs, candidates theoretical predictions and characteris- models as the code has a very convenient include the QCD axion, more generic tic signatures of the model and confront modular structure. Finally, “MadDM” ALPs (axion-like particles) and ultra- those predictions with the experimental can compute WIMP observables for any light bosonic candidates. ALPs are a bounds to select the model parameter BSM model from MeV to hundreds of TeV. class of models that received particu- space that is consistent with observa- As MadDM is a plugin of MadGraph, it lar attention at TOOLS 2020, and is now tions. To this end, the past decade has inherits unique features such as its auto- s being sought in fixed-target experi- seen the development of a huge variety of matic computation of new dark-matter

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FIELD NOTES FIELD NOTES

observables, including indirect-detec- Models just a few. Freeze-in is now supported tor from the high-energy to the re-engineering of high-energy It is an c o m m u n it i e s – r e fle c t i n g t o d a y’s n e e d s, authorisation and authentication infra- t i o n pr o c e s s e s w it h a n a r bit r a r y nu m b e r connecting by micrOMEGAs. collider limits to fixed-target exper- physics algorithms for accelerated exascale as well as those of the future – and aug- st r uc t ure is defin i ng demonst r ators to o f fi n a l-s t a t e p a r t i c l e s a n d l o o p -i n d u ced dark matter Models connecting dark matter with iments such as NA62. To complete architectures, highlighting the signif- project for ment the existing Unified European enable large scientific communities to processes. This is essential for analys- with collider collider experiments are becoming ever a vibrant landscape of development icant mutual benefits of collaboration an exascale Applications Benchmark Suite. securely access protected resources. ing sharp spectral features in indirect- m or e o p t i m i s e d t o t h e n e e d s o f u s e r s. For effor ts, Tomas Gon zalo (Monash) pre- across fields when it comes to HPC. The collaboration will now move for- experiments problem detection gamma-ray measurements e x a m pl e, m i c r OM E G A s i nt e r f a c e s w it h sented the GAMBIT collaboration’s work PRACE’s excellent record of providing Secure access ward with its ambitious technical pro- that cannot be mimicked by any known are becoming SModelS, which is capable of quickly t o pr o v i d e t o ol s for g l o b a l fit s t o g e n e r ic support and training will also be critical Access is another challenge when using gramme. Working groups are forming astrophysical background. ever more applying all possible LHC-relevant dark-matter models. to the success of the collaboration. HPC resources. Data from the HL-LHC around specific challenges, with the Both micrOMEGAs and MadDM per- optimised supersymmetric searches. The soft- Establishing a common benchmark and the SKA will be globally distributed partner organisations providing access mit the user to confront theories with to the needs ware also includes long-lived particles, A phenomenologist’s dream suite will help the organisations to and will be moved over high-capacity to appropriate testbed resources. Impor- recast experimental likelihoods for of users as commonly found in FIMP models. Huge efforts are underway to develop measure and compare the perfor- networks, staged and cached to reduce tant activities are already taking place several direct and indirect detection As MadDM is embedded in MadGraph, a computational platform to study new mance of different t y pes of computing latency, and eventually processed, in all four areas of work, and a second experiments. Jan Heisig (UCLouvain) noted Benjamin Fuks (LPTHE Paris), directions in experimental searches for resources for data-analysis workflows analysed and redistributed. Accessing collaboration workshop will soon be reported that this is a work in progress, t o ol s s u c h a s M a d A n a l y s i s m a y b e u s e d dark matter, and TOOLS 2020 showed from astronomy and particle physics. the HPC resources themselves involves organised. with many more experimental data sets to recast CMS and ATLAS searches. that we are already very close to the The suite will include applications rep- adherence to strict cyber-security to be included shortly. Torsten Bring- C e l i n e D e g r a n d e (UC L o u v a i n) d e s c r i b e d phenomenologist’s dream for WIMPs. resentative of the HEP and astrophysics protocols. A technical area devoted to Andrew Purcell CERN. mann () noted that a another nice tool, FeynRules, which TOOLS 2020 wasn’t just about dark mat- s t r e n g t h o f D a r k S US Y i s t h e m o d e l l i n g o f pr o d u c e s m o d e l fi l e s i n b o t h t h e M a dDM ter either – it also covered developments XXXII InternatIonal workshop of the logunov InstItute qualitatively different production mech- and micrOMEGAs formats given the i n H i g g s a nd fl a vou r p hy sic s, pre c i sion a n i s m s i n t h e e a rl y u n i v e r s e. A l o n g s id e Lagrangian for the BSM model, provid- t e s t s a n d g e n e r a l fit t i n g, a n d o t h e r t o ol s. Quark-matter fireba lls hashed out in Prot v ino the standard freeze-out mechanism, ing a very useful automatised chain from Interested parties are welcome to join in several new scenarios can arise, such the model directly to the dark-matter t he ne x t TOOLS conference due to ta ke as freeze-in (FIMP models, as chem- observables, high-energy predictions place in Annecy in 2022. The XXXII international workshop of S Mukherjee/BNL reveal the state of a neutron-star inte- ical and kinetic equilibrium cannot be and comparisons with experimental the Logunov Institute for High-Energy rior. Mergers observed since 2017 may achieved), dark freeze-out, reanni- results. Meanwhile, MadDump expands Chiara Arina Université Catholique Physics of the NRC Kurchatov Institute already be able to shed light on the exist- hilation and “cannibalism”, to name MadGraph’s predictions and detec- de Louvain. in Protvino, near Moscow, brought more e nc e o f a d e c on fi ne d p h a s e i n s id e t he s e than 300 physicists together online ultra-compact objects. HPC Collaboration kiCk-off worksHoP from 9 to 13 November to discuss “hot The Protvino workshop also revealed problems in hot and cold quark matter”. the enduring importance of studying The focus of the workshop was chiral heavy-quark physics. Since heavy quarks HPC comput ing collaborat ion k icks off theories and lattice simulations, which can be considered as approximately allow estimates beyond perturbation statically coloured sources, studies of On 29 September, CERN welcomed SKAO/ICRAR/SARAO/GLEAM/N Hurley-Walker/ICRAR theory for studying the strongly cou- quarkonia production are a step towards more than 120 delegates to an online pled quark–gluon plasma (sQGP) – the understanding hadron formation and the kick-off workshop for a new collabo- hot and/or dense plasma of quarks and c o n fi n e m e nt m e c h a n i s m. P e t e r P e t rec- ration on high-performance computing gluons that is created in heavy-ion zky (Brookhaven) concluded from a lat- (HPC). CERN, SKAO (the organisation collisions, and which may exist inside tice study of Bethe–Salpeter amplitudes leading the development of the Square neutron stars. Cooling droplets The QCD phase diagram as a function of that the potential model fails to describe Kilometre Array), GÉANT (the pan- Participants considered the QCD phase baryon chemical potential and temperature. bottomonium in terms of screened European network and services pro- diagram (pictured) as a function of tem- potential at high temperatures, with vider for research and education) and perature, magnetic field (B), baryon and strongly interacting matter that are pro- further investigations clearly needed

PRACE (the Partnership for Advanced isospin chemical potentials (μ B and μI), duced in heavy-ion collisions are not only in this field. Carlos Lourenço (CERN) C o m p ut i n g i n E u r o p e) w i l l w or k t o g e t h e r and varying quark masses. The cross- superfluids but also supervortical liquids. showed that the lowering of quarkonia t o r e a l i s e t h e f u l l p o t e nt i a l o f t h e c o m- over line (yellow strip), which marks a Impressive work was also shared at binding energies in the sQGP leads to ing generation of HPC technology for transition between hadronic matter and the intersection of heavy-ion collisions nontrivial measured suppression pat- data-intensive science. sQGP, has long attracted great interest. and gravitational-wave astrophysics terns. Eric Braaten (Ohio) showed that “It i s a n e x a s c a l e pr oj e c t for a n e x a s- Vladimir Skokov (Brookhaven) employed on the subject of the equation of state the decrease with multiplicity of the cale problem,” said , CERN recent progress in the Lee–Yang approach (EoS) of neutron-star cores. The EoS is ratio of the prompt production rates coordinator of the collaboration and to pha se t r a n sit ion s to der ive f rom fi rst the relationship between pressure and of X(3872) and Ψ(2S) in proton–proton

CERN openlab CTO, in opening remarks principles that μB > 400 MeV at the critical density, and can indicate whether had- collisions can be explained by the scat- at the workshop. “HPC is at the intersec- end point (a possible termination of the ronic or quark matter is inside. Theoret- t e r i n g o f c o -m o v i n g pi o n s o ff X(3872) i f t io n o f s e v e r a l i m p or t a nt R& D a c t i v it i e s: first-order phase-transition boundary). ical bounds on the EoS come from chiral it is a weakly bound charm-meson mol- the expansion of computing resources Discussions of the phase diagram also e ffe c t i v e t h e or ie s, p e r t u r b a t i v e Q C D, a nd ecule. With equally impressively scru-

for important data-intensive science Split screen The two future SKA telescope arrays, in South Africa (left) and Australia (right), will deliver included a decrease in the pseudocritical the bound on the speed of sound cs < 1/3. pulousness, Mariana Araújo (Innsbruck) projects like the HL-LHC and the SKA, approximately 8 Tb/s to two supercomputers, before distributing and storing up to 700 PB of data each year. temperature with B, the possibility of The quantities that can be extracted from offered a solution to the longstanding

the adoption of new techniques such a first-order phase transition at μB = 0 experimental data are the mass–radius “ polarisation puzzle” by as artificial intelligence and machine technical programme. Four main ini- s e m i n a t io n o f n e w pr o g r a m m i n g s k i l l s, as B tends to infinity, the existence and relation and the relationship between making use of a model-independent l e a r n i n g, a n d t h e e v olut i o n o f s o f t w a r e t i a l a r e a s o f w or k w e r e d i s c u s s e d a t t h e which is at the core of the new HPC col- location of a superconducting phase, the tidal deformabilities of merging The workshop fit t i n g pr o c e d u r e a n d t a k i n g i nt o a c c ount t o m a x i m i s e t h e p o t e nt i a l o f h e t e r o g e- e v e nt: t r a i n i n g a n d c e nt r e s o f e x p e r t i s e, l a b or a t i o n’s pl a n. A nu m b e r o f e x a m pl e s the disagreement between measured neutron stars and the peak frequency of revealed the correlations between cross sections neous hardware architectures.” b e n c h m a r k i n g, d a t a a c c e s s, a n d a ut h or- showing the potential of heterogene- and predicted collective flows of direct the emitted gravitational waves. Several enduring and polarisations. The full-day workshop, which was photons in heavy-ion collisions, and the speakers observed that tidal deform- The next “hot problems” workshop isation and authentication. o u s s y s t e m s we re d i s c u s s e d. O ne i s t he importance organised with the support of CERN One of the largest challenges in EU-f u n d e d DE E P-E S T pr oj e c t, w h i c h i s diamagnetic and paramagnetic natures abilities, which are measured in the will be held in November. openlab, saw participants establish the using new HPC technology is the need developing a modular supercomput- of the gas and deconfined matter, inspiral phase, and the peak gravitation- of studying c ol l a b or a t i o n’s fo u n d a t i o n s, o ut l i n e i n i- to adapt to heterogeneous hardware. ing prototype for exascale computing. respectively. Evgeny Zabrodin (Oslo) al-wave frequency, which is measured heavy-quark R N Rogalyov and V A Petrov NRC s tial challenges and begin to define the This involves the development and dis- DEEP-EST has already contributed explained that the rotating fireballs of in the post-merger phase, may together physics Kurchatov Institute IHEP, Protvino, Russia.

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virtual 2021 FEATURE WEAKLY INTERACTING SLIM PARTICLES

IEEE NUCLEAR SCIENCE SYMPOSIUM DESY/Heiner Müller-Elsner AND MEDICAL IMAGING CONFERENCE

2021 IEEE NSS MIC 28th International Symposium on Room-Temperature Semiconductor Detectors

Light through a wall The ALPS II experiment at DESY will target axion-like particles suggested by astrophysical anomalies. Online Conference IN SEARCH OF WISPS

16 - 23 October 2021 Experiments such as MADMAX, IAXO and ALPS II are expanding the search for axions and other weakly interacting ‘slim’ particles that could hail from far above the TeV scale, write Axel Lindner, Béla Majorovits and Andreas Ringwald.

ABSTRACT SUBMISSION he Standard Model (SM) cannot be the complete underpins the , but theorists have also theory of particle physics. Neutrino masses evade it. postulated a bevy of pNGBs that get their tiny masses by T No viable dark-matter candidate is contained within explicit symmetry breaking and are potentially discov- DEADLINE - 6 MAY 2021 it. And under its auspices the of the erable as physical particles. Typical examples arising in neutron, experimentally compatible with zero, requires the theoretically well-motivated grand-unified theories are cancellation of two non-vanishing SM parameters that are axions, flavons and majorons. Axions arise from a broken seemingly unrelated – the strong-CP problem. The physics “Peccei–Quinn” symmetry and could potentially explain General Chair: Ikuo Kanno explaining these mysteries may well originate from new the strong-CP problem, while flavons and majorons arise Deputy General Chair: Ralf Engels phenomena at energy scales inaccessible to any collider from broken flavour and lepton symmetries. NSS Co-Chair: Hiroyuki Takahashi in the foreseeable future. Fortunately, models involving Being light and very weakly interacting, WISPs would such scales can be probed today and in the next decade be non-thermally produced in the early universe and thus NSS Co-Chair: Craig Woody by a series of experiments dedicated to searching for very remain non-relativistic during structure formation. Such THE AUTHORS MIC Co-Chair: Taiga Yamaya weakly interacting slim particles (WISPs). particles would inevitably contribute to the dark matter of WISPs are pseudo Nambu–Goldstone bosons (pNGBs) the universe. WISPs are now the target of a growing number Axel Lindner and Andreas MIC Co-Chair: Jae Sung Lee that arise automatically in extensions of the SM from and type of experimental searches that are complementary Ringwald, DESY, RTSD Co-Chair: Ralph James global symmetries which are broken both spontaneously to new-physics searches at colliders. Hamburg, and RTSD Co-Chair: Tadayuki Takahashi and explicitly. NGBs are best known for being “eaten” Among theorists and experimentalists alike, the axion Béla Majorovits by the longitudinal degrees of freedom of the W and Z is probably the most popular WISP. Recently, massive bosons in electroweak gauge-symmetry breaking, which e ffor t s h a v e b e e n u n d e r t a k e n t o i m pr o v e t h e c a lc u lations Institute for Physics.

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10–9 CERN/MADMAX ] CAST limit CAST limit –1 transparency babyIAXO projection ALPS II projectionstellar cooling hint –11 hint

[GeV 10 QUAX

a γ ORGAN

IAXO projection -SLIC ALPs as experiments cavity

–13 dark matter ADMX prototype 10 projection QCD dark-matter axion

pre-inflationary scenario CAPP

HAYSTAC dielectric haloscope

MADMAX projection QCD dark-matter axion ADMX 10–15 post-inflationary scenario QCD axion in tension projection cavity experiments

axion/ALP–photon coupling g with astrophysics CAPP, ADMX Instruments for LC circuit projection 10–17 Haloscope home The Morpurgo magnet in CERN’s North 10–8 10–7 10–6 10–5 10–4 10–3 10–2 0.1 1 Advanced Science Area, which will house a prototype MADMAX haloscope. mass [eV] of model-dependent relic-axion production in the early T he fie ld of pl ay Limits (solid lines), projected sensitivities (dashed lines) and

universe. This has led to a considerable broadening of the hints and projections (shaded areas) in the axion–photon coupling (gaγ) versus mass range compatible with the explanation of dark matter axion mass (m ) plane. The axion obtains its mass through mixing with the neutral Mass spectrometers for vacuum, gas, plasma and surface science a by axions. The axion could make up all of the dark matter pion, leading ma to be inversely proportional to the symmetry-breaking scale fa

in the universe for a symmetry-breaking scale fa between and therefore proportional to gaγ (orange, yellow and blue bands). Generic ALPs roughly 108 and 1019 GeV (the lower limit being imposed by are not expected to exhibit such a relationship. astrophysical arguments, the upper one by the Planck scale), corresponding to axion masses from 10–13 eV to 10 meV. For They target WISPs that flow through the galactic halo, other light pNGBs, generically dubbed axion-like particles shine from the Sun, or spring into existence when lasers (ALPs), the parameter range is even broader. With many pass through strong magnetic fields in the laboratory. plausible relic-ALP-production mechanisms proposed by theorists, experimentalists need to cover as much of the Dark-matter halo unexplored parameter range as possible. Haloscopes target the detection of dark-matter WISPs in Although the strengths of the interactions between the halo of our galaxy, where non-relativistic cold-dark- axions or ALPs and SM particles are very weak, being matter axions or ALPs induce oscillations

inversely proportional to fa, several strategies for observing as they pass through a magnetic field. The frequency of Residual Gas Analysis them are available. Limits and projected sensitivities span the oscillations corresponds to the axion mass, and the several orders of magnitude in the mass-coupling plane amplitude to B/fa. When limits or projections are given Perform RGA at UHV/XHV . Our RGA configurations include systems for UHV (see “The field of play” fig ure). for these kinds of experiments, it is assumed that the Since axions or ALPs can usually decay to two photons, particle under scrutiny homogeneously makes up all of science applications including temperature-programmed desorption and an external static magnetic field can substitute one of the dark matter in the universe, introducing significant electron/photon stimulated desorption. the two photons and induce axion-to-photon conver- cosmological model dependence. sion. Originally proposed by , this inverse The furthest developed currently operating haloscopes Primakoff effect can classically be described by add- are based on resonant enhancement of the axion-induced ing source terms proportional to B and E to Maxwell’s electric-field oscillations in tunable resonant cavities. Thin Film Surface Analysis equations. Practically, this means that inside a static Using this method, the presently running ADMX pro- h o m o g e n e o u s m a g n e t ic fie ld t h e pr e s e n c e o f a n a x io nor ject at the University of Washington has the sensitivity Conduct both static and dynamic SIMS analysis with a choice of primary ions ALP field induceselectric-field oscillations – an effect to discover dark-matter axions with masses of a few µeV. for full chemical composition and depth profiling. Our SIMS solutions include readily exploited by many experiments searching for Nuclear resonance methods could be sensitive to halo WISPs. Other processes exploited in some experimen- dark-matter axions with mass below 1 neV and “fuzzy” complete workstations and bolt-on modules. tal searches and suspected to lead to axion production dark-matter ALPs down to 10–22 eV within the next decade, are their interactions with electrons, leading to axion for example at the CASPEr experiments being developed , and their interactions with nucleons at the University of Mainz and Boston University. Mean- or nuclei, leading to -axion bremsstrahlung or while, experiments based on classical LC circuits, such Plasma Characterisation oscillations of the electric dipole moment of the nuclei as ABRACADABRA at MIT, are being designed to measure or nucleons. ALP- or axion-induced mag net ic field oscil lat ions in t he IAXO’s design Fully characterise a range of plasmas: RF, DC, ECR and pulsed plasmas, including The potential to make fundamental discoveries from centre of a toroidal magnet. These could be sensitive in a profited neutrals and neutral radicals. Extend your analyses to atmospheric pressure small-scale e x p e r i m e nt s i s a s i g n i fic a nt a p p e a l o f e x p eri- mass range between 10 neV and 1 µeV. greatly from mental WISP physics, however the most solidly theoretically For dark-matter axions with masses up to approximately experience processes using the HPR-60, with time-resolved mass/energy analysis. motivated WISP parameter regions and physics questions 50 µeV, promising developments in cavity technologies such with the require setups that go well beyond “table-top” dimensions. as multiple matched cavities and superconducting or diel- ATLAS toroid

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ADVERTISING FEATURE FEATURE WEAKLY INTERACTING SLIM PARTICLES

Astrophysical hints The clean technology innovations Weakly interacting slim particles (WISPs) NASA/ESA below 100 meV or sub-keV-mass ALPs with a could be produced in hot astrophysical coupling to both electrons and photons. plasmas and transport energy out of stars, Other observations suggest that TeV solving challenges in particle physics including the Sun, stellar remnants and photons from distant blazars are less absorbed other dense sources. Observed lifetimes and than expected by standard interactions with energy-loss rates can therefore probe their extragalactic background light – the so-called Particle physics laboratories across Europe are pushing the frontiers of science and existence. For the axion, or an axion-like transparency hint. This could be explained technology every day. To help them excel, particle (ALP) with sub-MeV mass that by the conversion of photons into ALPs in they need a cleanroom partner that can couples to nucleons, the most stringent limit, the magnetic field of the source, and back to 8 resolve contamination issues in new, fa > ~10 GeV, stems from the duration of the 47 Tucanae Globular clusters can be used photons in astrophysical magnetic fields. innovative ways. Over the years, cleanroom neutrino signal from the progenitor neutron to compare photon and neutrino emissions Interestingly, these would have about the same specialist Connect 2 Cleanrooms (C2C) has star of Supernova 1987A. from white dwarf stars. ALP–photon coupling strength as indicated by supported research organisations across Tantalisingly, there are stellar hints from the observed stellar anomalies, though with Europe with cleanroom projects, partnering observations of red giants, helium-burning with respect to those expected from standard a mass that is incompatible with both ALPs with CERN, STFC and ESS to find innovative solutions to support the R&D, build, servicing stars, white dwarfs and pulsars that seem to energy emission by neutrinos. These hints which can explain dark matter and with QCD and maintenance of particle accelerators. indicate energy losses with slight excesses may be explained by axions with masses axions (see “The field of play” figure, p27).

Part of CERN’s Prevessin site in France is DESY DESY dedicated to producing beam intercepting ectric cavities are ongoing at several locations, including devices, to be used in different particle position the cleanroom can be used for work C2C developed mobile cleanrooms that at CAPP in South Korea, the University of Western Aus- accelerators across its world-leading on smaller parts, which means all the beam maintain ISO 14644-1 class 5 conditions and tralia, INFN Legnaro and the RADES detector, which has particle physics laboratory. This involves the intercepting device components can be are used to provide end-to-end protection taken data as part of the CAST experiment at CERN. Above assembly of highly specialised parts such assembled in the same environment. covering the build, transportation within as collimators to clean the halo of proton the tunnel and the interconnection of ~40 µeV, however, the cavity concept becomes more and beams, beam stoppers and beam dumps to The softwall cleanroom is designed to different accelerator sections. The size of more challenging, as sensitivity scales with the volume absorb the energy of particles. These beam maintain the clean air integrity no matter the tunnel presented a challenge for the of the resonant cavity, which decreases dramatically with 3 intercepting devices are built in sections what the configuration. It achieves particle mobile cleanrooms. With an overall height increasing mass (as roughly 1/ma). To reach sensitivity at to allow parts to be decommissioned and counts to meet ISO 14644-1 class 8 when of 4 metres, the services needed to operate higher masses, in the region of a few hundred µeV, a novel removed for servicing and maintenance. in the extended position, and in the closed the accelerator at points bring the height “dielectric haloscope” is being developed by the MADMAX position it achieves particle counts to meet down to 3.5 metres. For this reason, STFC (Magnetized Disk and Mirror Axion experiment) collabo- With these highly calibrated pieces of ISO 14644-1 class 6. requested the mobile cleanroom to be in machinery there is a risk that exposed parts three different sections. Each section can ration for potential installation at DESY. It exploits the fact could be effected by particulate contamination “Connect 2 Cleanrooms was the most operate independently and be connected that static magnetic-field boundaries between media with during assembly or servicing. Even a small competitive company who passed our tender together when in position. One section is d i ffe r e nt d ie le c t r ic c o n s t a nt s le a d t o t i n y p o w e r e m i s sion amount of contamination inside the chamber qualification,” says Oliver Aberle, project height adjustable so that it can move freely that compensate the discontinuity in the axion-induced could affect how the beam is travelling and manager at CERN. “The design stage was under the services, then be adjusted to a full e le c t r ic fie ld s i n n e i g h b o u r i n g m e d i a. I f mu lt i ple s u r faces render them ineffective. Conducting the very fast and the principle of the layout was height when in position. are stacked in front of each other, this should lead to con- assembly inside a cleanroom, which has a high complete within the first iteration. The end structive interference, boosting the emitted power from air change rate of high efficiency particulate result is unique when you see the extending C2C worked to STFC’s User Requirement the expected axion dark matter in the desired mass range air (HEPA), would greatly reduce the risk of cleanroom in motion.” Specification and added value to the design particulate contamination. However, as some in terms of the fine detail, such as how to to detectable levels. Other novel haloscope concepts, based of these parts are up to 6 metres in length STFC & ESS’s mobility challenge Science connect the cleanroom units together and on meta-materials (“plasma haloscopes”, for example) and for example, by cosmological models where Peccei–Quinn Prototype and 30 tonnes in weight, transportation is and Technology Facilities Council (STFC) is perform the height alteration. topological insulators, are also currently being developed. s y m m e t r y br e a k i n g h a p p e n e d a f t e r a n i n fl at io n a r y p h a s e Conceptual design only possible by overhead crane. The real a world-leading science organisation that These could have sensitivity to even higher axion masses, of the universe. That’s where MADMAX comes in. The of the BabyIAXO challenge then, lies in how these parts would supports research in development in many “The biggest stand out I can say about up to a few meV. collaboration is working on the dielectric-haloscope con- helioscope, which be transferred into a cleanroom. disciplines, including particle physics. C2C working with Connect 2 Cleanrooms is their cept – initiated and led by scientists at the Max Planck will seek to observe has engineered numerous contamination flexibility,” says Keith Middleman, Senior Staying in tune Institute for Physics in Munich – to investigate the mass solar axions. A telescopic solution control solutions for STFC, to meet their niche Vacuum Engineer at STFC. “They bring In principle, axion-dark-matter detection should be rel- region around 100 µeV. Although on a different scale, C2C have requirements and in 2018 were appointed ideas. For us, it gives them an advantage innovated to overcome a similar challenge for a project they were delivering for The over other companies who try to offer more atively simple, given the very high number density of MADMAX will use a huge ~9 T superconducting dipole 13 3 previously. C2C’s R&D team developed European Spallation Source (ESS) in . off-the-shelf cleanrooms, because STFC need particles – approximately 3 × 10 axions/cm for an axion magnet with a bore of about 1.35 m and a stored energy of an adjustable cleanroom canopy for the These cleanrooms are now facilitating a custom-built solution. “Their mobility and mass of 10 µeV – and the well-established technique of roughly 480 MJ. Such a magnet has never been built before. plastics industry, that can be incorporated the build and operation of the particle flexibility to find new areas for cleanrooms resonant axion-to-photon conversion. But, as the axion The MADMAX collaboration teamed up with CEA-IRFU and into a modular cleanroom and automated accelerator which will be the world’s most and having the skill to provide a bespoke mass is unknown, the experiments must be painstakingly Bilfinger-Noell and successfully worked out a conceptual to slide back, giving overhead crane access powerful neutron source, enabling scientific solution, is something that isn’t readily tuned to each possible mass value in turn. After about design. First steps towards qualifying the conductor are to injection moulding machinery inside. breakthroughs in research. available elsewhere.” 15 years of steady progress, the ADMX experiment has under way. The plan is for the magnet to be installed at Scaling up on this principle, C2C collaborated reached QCD-axion dark-matter sensitivity in the mass DESY inside the old iron yoke of the former HERA exper- with CERN scientists to design a telescopic The is being built in cleanroom with three moveable modules. sections at ESS facilities in Lund, Sweden. regime of a few µeV. iment H1. DESY is already preparing the required infra- When the larger beam intercepting device Each section is initially built outside of the ADMX uses tunable microwave resonators inside a strong structure, including the liquid-helium supply necessary sections have been craned into the servicing tunnel as there are fewer restrictions on space Connect 2 Cleanrooms and Cleanroomshop.com solenoidal mag net ic field, and moder n quantum sensors to cool the magnet. R&D for the dielectric booster, with up bay, the cleanroom can be extended to and better access to infrastructure. Once Tel +44(0)1524 812899 for readout. Unfortunately, however, this technology is not to 80 adjustable 1.25 m2 disks, is in full swing. laterally envelope the part. The modules completed, the sections are then checked Email [email protected] scalable to the higher axion-mass regions as preferred, A first prototype, containing a more modest 20 discs of extend on guide rails from a closed position and sealed before being transported down Web www.connect2cleanrooms.com to triple the floor space.When in the closed the tunnel. www.cleanroomshop.com CERN COURIER MARCH/APRIL 2021 29

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FEATURE WEAKLY INTERACTING SLIM PARTICLES FEATURE EA INTERATING SI ARTIES DESY/M Mayer removing the need to make assumptions about their pro- In the overlapping mass region up to 0.1 meV, the sensitiv- duction. ALPS II is based on 24 modifi ed superconducting ities of ALPS II and BabyIAXO are roughly equal. In the event dipole magnets that have been straightened by brute-force of a discovery, this would provide a unique opportunity to deformation, following their former existence in the pro- study the new WISP. Excitingly, a similar case might be ton accelerator of the HERA complex. With the help of realised for IAXO combining the optics and detectors of two 124 m-long h i g h - fi n e s s e optical resonators, encom- ALPS II with simplifi ed versions of the dipole magnets being passed by the magnets on both sides of the wall, ALPS II is studied for FCC-hh would provide an LSW experiment with a l so t he fi r st laser-based setup to fully exploit resonance “IAXO sensitivity” regarding the axion-photon coupling, techniques. Two readout systems capable of measuring a albeit in a reduced mass range. This has been outlined 1064 nm photon fl ux down to a rate of 2 × 10–5 s–1 have been as the putative JURA (Joint Undertaking on Research for developed by the collaboration. Compared to the present Axions) experiment in the context of the CERN-led Physics best LSW limits provided by OSQAR at CERN, the signal-to- Beyond Colliders study. noise ratio will rise by no less than 12 orders of magnitude T h e p a s t d e c a d e h a s d e l i v e r e d s i g n i fi c a nt d e v e lo p m e nt s at ALPS II. Nevertheless, MADMAX would surpass ALPS II in axion and ALP theory and phenomenology. This has in the sensitivity for the axion-photon coupling strength been complemented by progress in experimental methods by more than three orders of magnitude. This is the price to cover a large fraction of the interesting axion and ALP to pay for a model-independent experiment – however, parameter range. In close collaboration with universities Panoramic view 30 cm diameter, will be tested in the “Morpurgo” magnet at toroidal magnet with eight 60 cm-diameter bores. ALPS II principally targets not dark-matter candidates but and institutes across the globe, CERN, DESY and the Max ALPS II is under CERN during future accelerator shutdowns (see “Haloscope IAXO’s design profited greatly from experience with the ALPs indicated by astrophysical phenomena. Planck society will together pave the road to the exciting construction in the home” fig ure, p27). Wit h a pea k field st reng t h of 1.6 T, its ATLAS toroid. results that are expected this decade.  AS II is HERA tunnel at dipole field will allow newALP-dark -matter parameter In the past three years, the collaboration, led by the Uni- Tnelling ahea DESY. WISPs may regions to be probed, though the main purpose of the versity of Zaragoza, has been concentrating its activities The installation of the 24 dipole magnets in a straight Frther reaing t he fi r st l a s er- be produced in the prototype is to demonstrate the operation of the booster on the BabyIAXO prototype in order to finesse the magnet section of the HERA tunnel was completed in 2020. Three L Di Luzio et al. 2020 hys. ept. 1. ase setp to left magnet string system in cryogenic surroundings inside a magnetic field. concept, the X-ray telescopes necessary to focus photons clean rooms at both ends and in the centre of the exper- MADMAX Collaboration 2019 ur. hys. . C 3. lly eploit before converting The MADMAX collaboration is extremely happy to have from solar axion conversion and the low-background detec- iment were also installed, and optics commissioning is IAXO Collaboration 2019 CA 047. resonance back to photons on fo u n d a s u it a ble m a g n e t at C E R N for s uc h t e s t s. I f s u ffic ie nt tors. BabyIAXO will increase the signal-to-noise ratio of under way. A fi rst science run is expected for autumn 2021. ALPS II Collaboration 2013 I T09001. technies the right. A large funds can be acquired within the next two to three years CAST by two orders of magnitude; IAXO by a further two vacuum chamber for magnet construction, and provided that the prototype orders of mag nitude. will house both e ffor t s at C E R N a r e s uc c e s s f u l, M A DM A X c o u ld s t a r t data In December 2020 the directorates of CERN and DESY the “wall” and ta k ing at DESY in 2028. signed a collaboration agreement regarding BabyIAXO: the optics, which While direct dark-matter s e a rc h e x p e r i m e nt s l i k e A DM X CERN will provide the detailed design of the prototype mode-match the a n d M A DM A X offe r b y f a r t h e h i g h e s t s e n s it i v it y for axion magnet including its cryostat, while DESY will design case study two optical searches, this is based on the assumption that the dark a n d pr e p a r e t h e m o v a ble pl at for m a n d i n f r a s t r uc t u r e (s e e resonators. matter problem is solved by axions, and if no signal is “Prototype” figure). BabyIAXO will be located at DESY in Make informed discovered any claim of an exclusion limit must rely on Ha m b u r g. T h e c ol l a b or at io n h o p e s t o at t r a c t t h e r e m a i n i n g specific cosmological assumptions. Therefore, other less funds for BabyIAXO so construction can begin in 2021 and model-dependent e x p e r i m e nt s, s uc h a s h e l io s c o p e s or l i g ht first science runs could take place in 2025. The timeline design decisions shining through a wall (LSW) e x p e r i m e nt s, a r e e x t r e m e l y for IAXO will depend strongly on experiences during the beneficial in addition to directdark-matter searches. construction and operation of BabyIAXO, with first light with EM simulation. potent ially possible in 2028. Solar axions In cable design, it’s important to account for capacitive, In contrast to dark-matter a x io n s or A L P s, t h o s e pr o d uc e d Light shining through a wall inductive, and thermal effects in the cable parts. For in the Sun or in the laboratory should have considerable In contrast to haloscopes, helioscopes do not rely on the example, different bonding types result in different current momentum. Indeed, solar axions or ALPs should have assumption that all dark matter is made up by axions. buildup and losses. Similarly, phase conductor and armor energies of a few keV, corresponding to the temperature But light-shining-through-wall (LSW) experiments are twist affect current distribution in the cable. Knowing this up at which they are produced. These could be detected by even less model dependent with respect to ALP produc- front will help you make informed design decisions. This is h e l io s c o p e s, w h ic h s e e k t o u s e t h e i n v e r s e P r i m a k off e ffe ct t io n. He r e, i nt e n s e l a s e r l i g ht c o u ld b e c o n v e r t e d t o a x io n s where electromagnetics simulation comes in. to convert solar axions or ALPs into X-rays in a magnet or ALPs inside a strong magnetic field by the Primakoff p oi nte d to w a rd s t he Su n, a s at t he CE R N A x ion S ol a r Te l- effect. Behind alight-impenetrable wall they would be learn more comsol.blog/cable-tutorials escope (CAST) experiment. Helioscopes could cover the re-converted to photons and detected at t he same w ave- mass range compatible with the simplest axion models, in le n g t h a s t h e l a s e r l i g ht. T h e d i s a d v a nt a g e o f L S W e x p e r i- t h e v ic i n it y o f 10 m eV, a n d c o u ld b e s e n s it i v e t o A L P s w it h m e nt s i s t h at t h e y o n l y r e a c h s e n s it i v it y t o A L P s w it h a m a s s masses below 1 eV w it hout any tuning at all. up to a few hundred µeV with comparably high coupling The CAST helioscope, which reused an LHC prototype to photons. However, this is sensitive enough to test the dipole magnet, has driven this field in the past decade, parameter range consistent with the transparency hint a n d pr o v id e s t h e m o s t s e n s it i v e e x c lu s io n l i m it s t o d at e. and parts of the mass range consistent with the stellar Going beyond CAST calls for a much larger magnet. For the hints (see “Astrophysical hints” panel, p29). The COMSOL Multiphysics® software is used for simulating designs, devices, next-generation International Axion Observatory (IAXO) The Any Light Particle Search (ALPS II) at DESY follows and processes in all fields of engineering, manufacturing, and scientific research. helioscope, CERN members of the international collab- this approach. By seeking to observe light shining through a oration worked out a conceptual design for a 20 m-long w a l l, a n y A L P s wo u ld b e g e n e r at e d i n t h e e x p e r i m e nt it s e l f,

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FEATURE INR RAS

...the power in ! RUSSIA’S PARTICLE- ULTRA AVAILABLE PHYSICS POWERHOUSE

AMPLIFIERS Fifty years after being established, the Institute for Nuclear Research in Moscow FOR ACCELERATOR & continues to leave its mark on neutrino and high-energy physics.

ounded on 24 December 1970, the Institute for JINR MEDICAL APPLICATIONS Nuclear Research of the Russian Academy of F Sciences (INR RAS) is a large centre for particle physics in Moscow with wide participation in interna- TMD in collaboration with Rosatom - NIITFA is now tional projects. The INR RAS conducts work on cosmol- ogy, neutrino physics, astrophysics, high-energy physics, able to offer revolutionary, ultra-available RF solid state and technology, neutron research and amplifiers for scientific and medical applications. nuclear medicine. It is most well-known for its unique research facilities that are spread all across Russia, and its Innovative power combining and control system results in: large-scale collaborations in neutrino and high-energy physics. This includes experiments such as the Baksan Neutrino Observatory, and collaborations with a number • Ultra-compact systems, typically one Applications: of CERN experiments including CMS, ALICE, LHCb, NA61 and NA64. 19” rack / 100 kW (pulse) • , LINACs for scientific, The institute was founded by the Decree of the Presidium • CW / Pulse Systems, long pulse experimentation/particle physics of the USSR Academy of Sciences in accordance with the • Modular Solid State architecture, and Spallation systems decision of the government. Theoretical physicist Moisey compact modules (<10 kg) • Medical therapy equipment Markov had a crucial role in establishing the institute and

Courtesy Honeywell Aerospace • Highly Maintainable with Hot Swap • Cyclotrons for radioisotope influenced the research that would later be undertaken. capability production His ambition is seen in the decision to base INR RAS on three separate nuclear laboratories of the P.N. Lebedev • Wall Plug efficiency competitive with • Option to upgrade existing systems Institute of Physics of the Academy of Sciences of the tube technology (55% demonstrated) USSR. Each laboratory had a leading physicist in charge: Ice breaker New clusters of optical modules being installed in the underwater • Highly robust to VSWR mismatch Other Products: the Laboratory headed by Nobel laure- Baikal-GVD Neutrino Telescope in April 2020. • High MTBF and Low MTTR • High Power, Very Low Phase Noise ate ; the Photonuclear Reactions Laboratory • No loss of power from any single TWT Amplifiers under the direction of Lyubov Lazareva; and a neutrino and applied research in nuclear and neutron physics, laboratory headed by Georgy Zatsepin and Alexander condensed matter, development of technologies for the element failure • Brazed UHV components C hud a k o v. T h e m a n o v e r s e e i n g it a l l w a s t h e fi r s t d i r e c t or production of a wide range of radioisotopes, operation of • High efficiency enhances reliability • Electron Guns of INR RAS, Albert Tavkhelidze, a former researcher at a complex and many other applications. • Frequencies available from • Diffusion Bonding the Joint Institute for Nuclear Research (JINR, Dubna). 2 MHz to 1.3 GHz • Vacuum/Hydrogen Brazing In 1987 Victor Matveev took over as director, followed by A town called Neutrino Leonid Kravchuk in 2014. Since 2020 the director of INR Over 1000 miles south from the Troitsk laboratory, an • MW power capability • Speciality Cleaning RAS is Maxim Libanov. underground tunnel in the Caucasus mountains is the From the very beginning, major efforts were focused base of another INR RAS facility, the Baksan Neutrino on the construction and operation of large-scale research Observatory (BNO). The facility was established in 1967 For more information on our leading edge facilities. The hub of INR RAS was built 20 km outside of and the Baksan Underground Scintillation Telescope Moscow, in a town called Troitsk. In 1973 an accelerator (BUST) started taking data in 1978. A town sensibly called technology email us at [email protected] THE AUTHORS division was created, with a long-term goal of creating a “Neytrino” (Russian for neutrino) was constructed in meson facility that would house a 600 MeV linear acceler- parallel with the facility, and was where scientists and Anna or visit www.tmd.co.uk Veresnikova ator for protons and H– ions. The first beam was eventually their families could live 1700 m above sea level next to scientific secretary accelerated to 20 MeV in 1988 and the facility was fully the observatory. In 1987 BUST was one of the four neu- INR RAS and operational by 1993. Now known as the Moscow Meson trino detectors that first directly observed neutrinos from Grigory Rubtsov Facility, it has the most powerful linear proton acceler- supernova SN1987A. deputy director ator in the Euro-Asian region, providing fundamental T h e o b s e r v at or y d id n o t fi n i s h t h e r e, a n d t h e n e x t s tep INR RAS.

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FEATURE INR RAS INR RAS INR was the gallium-germanium neutrino telescope (GGNT), HIGH VOLTAGE which was home to the Soviet–American Gallium Exper- POWER SUPPLIES iment (SAGE). The experiment made important contri- butions towards solving the problem and simultaneously gave rise to a new problem known as the MAGNET gallium anomaly, which is yet to be explained. SAGE is POWER SUPPLIES still well and truly alive, and with a recent upgrade of the GGNT completed in 2019, the team will now hunt for HIGH CURRENT sterile neutrinos By 1990 another neutrino detector was under con- POWER SUPPLIES struction, following the original proposal of Markov and Chudakov. In collaboration with JINR, plans for an under- HIGH PRECISION water neutrino telescope located at the world’s largest POWER SUPPLIES freshwater lake, Lake Baikal, took shape. Underwater telescopes use glass spheres that house photomultiplier tubes to detect Cherenkov light from the charged par- POWER SUPPLIES FOR BASIC RESEARCH ticles emerging from neutrino interactions in the lake AT THE HIGHEST LEVEL water. The first detector developed for Lake Baikal was the NT200, which was constructed over five years from Heinzinger has played a role in research for a very long time 1993–1998 and detected cosmic neutrinos for more than a A timeline of INR RAS Clockwise from top left: theoretical physicist Moisey thanks to its expertise and passion. In addition to the European decade. It has now been replaced with the Gigaton Volume Markov at the foundation of the Meson Factory building, Troitsk, 1971; CERN facility in Geneva, companies, universities, colleges and Detector (Baikal-GVD), and plans were concluded in 2015 construction of the first stage of the linear accelerator facility; the top view of the state institutions are investing in research. Whether it be testing for the first phase of the telescope to be completed by linear accelerator facility; deployment of the underwater optical module of the and measuring equipment, accelerator technology or HV pow- 2021. Baikal-GVD h a s a n e ffe c t i v e v olu m e o f1 km3 and is Baikal neutrino telescope; view of the Baksan Neutrino Observatory laboratories; er supplies for particle detectors: High-specification technical designed to register and study ultrahigh-energy neutrino the tunnel in the Andyrchi mountain for the Baksan Neutrino Observatory

equipment from Heinzinger helps to produce reliable and resilient 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: results in laboratories and testing centers all over the world. fluxes from astrophysical sources. experiments; and the neutrino council at the Baksan Neutrino Observatory with the participation of Alexander Chudakov, Vadim Kuzmin, , Left a mark Petr Spivak and Albert Tavkhelidze. There is no doubt that INR RAS has left its mark on high-energy physics. While the institute’s most recog- of hadrons outside the framework of perturbation theory, nised work will be in neutrino physics, the Moscow Meson the first everbrane-world models and the development Scintinel™ Stilbene Scintillation Crystals are Facility has also contributed to other areas of the field. of principles and the search for mechanisms for the for- the gold standard in neutron-gamma Pulse An experiment was created for direct measurement of mation of the baryon asymmetry of the universe. Shape Discrimination. the mass of the electron antineutrino via the beta decay of tritium. The “Troitsk nu-mass” experiment started in Global reach Unlike most neutron detectors, stilbene is 1985 and its limit on the electron antineutrino mass was Scientists from INR RAS take an active part in the work the world’s best for years. The improvement of this result of a number of large international experiments at CERN, sensitive only to high-energy fast neutrons. became possible only in 2019 with the large-scale KATRIN JINR, and in Germany, Japan, Italy, USA, China, France, Directly detecting fast neutrons preserves experiment in Germany that was created in collaboration and other countries. The institute also conducts timing, neutron energy distribution, and Enabling Fast with INR RAS. In fact, the Troitsk nu-mass experiment educational activities, having its own graduate school directional information. Scintinel stilbene is was considered as a prototype for KATRIN. and teaching departments in nearby institutes such as superior to liquid and plastic for Experimental data have been obtained on nuclear reac- the Moscow Institute for Physics and Technology. neutron/gamma discrimination. tions involving protons and neutrons of medium energies The future of INR RAS is deeply rooted in its new along with data on photonuclear reactions, including the large-scale infrastructures. Baikal-GVD will, along • Superior Pulse Shape Discrimination study of the spin structure of a proton using an active with the IceCube experiment at the South Pole, be able • Lower Gamma false rate pola r ised t a rget. Ne w effec t s i n col l isions of relat iv ist ic to register neutrinos of astrophysical origin in the hope nuc le i h a v e b e e n o b s e r v e d a n d a n e w s c ie nt i fic d i r e c t io n of establishing their nature. A project has been prepared • Lower Threshold for gamma rejection has been taken, “nuclear photonics”. Two effects in astro­ to modernise the linear proton accelerator in Troitsk • Excellent Neutron Detection Efficiency particle physics have been named after scientists from INR using superconducting radio-frequency cavities, while RAS: the “GZK cut­off”, which is a high-energy cut­off there are also plans to construct a large centre for nuclear There are Crystals are available in sizes up to 5 inches in the spectrum of the ultrahigh-energy cosmic rays medicine based at the linear accelerator centre. There is plans to and in various format shapes. Stilbene named after Kenneth Greisen (US), Georgy Zatsepin and a proposal to build the Baksan Large-Volume Scintillator construct a crystals are easily integrated with PMT and Vadim Kuzmin (INR RAS); and the “Mikheyev–Smirnov– Detector at BNO containing 10 ktons of ultra-pure liquid large centre SiPM devices. Wolfenstein effect” concerning neutrino oscillations in scintillator, which would be able to register neutrinos matter, named after Stanislav Mikheyev, Alexei Smirnov from the carbon–nitrogen–oxygen (CNO) fusion cycle for nuclear (INR RAS) and Lincoln Wolfenstein (US). in the Sun with a precision sufficient to discriminate medicine Theoretical studies at INR RAS are also widely known, between various solar models. based at For more information go to including the development of perturbation theory meth- The past 50 years have seen consistent growth at INR the linear www.inradoptics.com/scintinel ods, study of the ground state (vacuum) in gauge theories, RAS, and with world-leading future projects on the hori- accelerator methods for studying the dynamics of strong interactions zon, the institute shows no signs of slowing down.  centre

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FEATURE 50 YEARS OF HADRON COLLIDERS

50 years ago CERN’s Intersecting Storage Rings set in motion a series of hadron colliders charting nature at the highest possible DISCOVERY MACHINES energies, write Lyn Evans and Peter Jenni.

he ability to collide high-energy beams of hadrons CERN-PHOTO-7408061 CERN-PHOTO-7408061 CERN-AC-7604110 emerged a new committee, the European Committee for under controlled conditions transformed the field of Future Accelerators, under the chairmanship of one of T particle physics. Until the late 1960s, the high-energy CERN’s founding fathers, . After about two frontier was dominated by the great proton synchrotrons. years of deliberation, consensus was formed. The storage The Cosmotron at Brookhaven National Laboratory and ring gained most support, although a high-energy proton the at Lawrence Berkeley National Laboratory synchrotron, the (SPS), was built were soon followed by CERN’s Proton Synchrotron and some years later and would go on to play an essential role in Brookhaven’s Alternating Gradient Synchrotron, and later the development of hadron storage rings. On 15 December by the Proton Synchrotron at Serpukov near Moscow. In 1965, with the strong support of Amaldi, the CERN Council these machines protons were directed to internal or exter- unanimously approved the construction of the Intersecting nal targets in which secondary particles were produced. Storage Rings (ISR), launching the era of hadron colliders. The kinematical inefficiency of this process, whereby the centre-of-mass energy only increases as the square root of First collisions the beam energy, was recognised from the outset. In 1943, Construction of the ISR began in 1966 and first collisions Norwegian engineer Rolf Widerøe proposed the idea of col- were observed on 27 January 1971. The machine, which liding beams, keeping the centre of mass at rest in order to needed to store beams for many hours without the help exploit the full energy for the production of new particles. of synchrotron-radiation damping One of the main problems was to get colliding beam inten- t o c o m b at i n e v it a bl e m a g n e t ic fie ld On 15 December 1965, sities high enough for a useful event rate to be achieved. In errors and instabilities, pushed the the 1950s the prolific group at the University of Wisconsin boundaries in accelerator science on the CERN Council Midwestern Universities Research Association (MURA), led Super collider CERN’s Spp–S in 1983. all fronts. Several respected scien- unanimously approved

by Donald Kerst, worked on the problem of “stacking” par- Fermilab tists doubted that it would ever work. ticles, whereby successive pulses from an injector synchro- In fact, the ISR worked beautifully, the construction of the tron are superposed to increase the beam intensity. They exceeding its design luminosity by ISR, launching the era mainly concentrated on protons, where Liouville’s theorem an order of magnitude and provid- (which states that for a continuous fluid under the action ing an essential step in the devel- of hadron colliders of conservative forces the density of phase space cannot be opment of the next generation of increased) was thought to apply. Only much later, ways to hadron colliders. A key element was beat Liouville and to increase the beam density were found. the performance of its ultra-high-vacuum system, which At the 1956 International Accelerator Conference at CERN, was a source of continuous improvement throughout the Kerst made the first proposal to use stacking to produce 13 year-long lifet ime of t he mac hine. c ol l id i n g b e a m s (n o t y e t s t or a g e r i n g s) o f s u ffic ie nt i nt e n s it y. For the experimentalists, the ISR’s collisions (which At that same conference, Gerry O’Neill from Princeton pre- reached an energy of 63 GeV) opened an exciting adven- sented a paper proposing that colliding electron beams could ture at the energy frontier. But they were also learning be achieved in storage rings by making use of the natural w h at k i n d o f d e t e c t or s t o b u i ld t o f u l l y e x ploit t h e p o t e nt i a l damping of particle amplitudes by synchrotron-radiation of the machine – a task made harder by the lack of clear emission. A design for the 500 MeV Princeton–Stanford collid- physics benchmarks known at the time in the ISR energy ing beam experiment was published in 1958 and construction regime. The concept of general-purpose instruments built started that same year. At the same time, the Budker Institute by large collaborations, as we know them today, was not in for Nuclear Research in Novosibirsk started work on VEP-1, a the culture of the time. Instead, many small collaborations pair of rings designed to collide electrons at 140 MeV. Then, built experiments with relatively short lifecycles, which THE AUTHORS in March 1960, gave a seminar at Labora- New era CERN’s Intersecting Storage Rings in 1974. TeV frontier The Tevatron at Fermilab in 2011. constituted a fruitful learning ground for what was to come Lyn Evans tori Nazionali di Frascati in Italy where he first proposed a at t he ne x t generat ion of hadron colliders. (former LHC project single-ring, 0.6 m-circumference 250 MeV electron–positron energy collisions in a circular electron–positron collider sharply divided between two camps, one pushing a very There was initially a broad belief that physics action director), Imperial c ol l id e r. “A d A” pr o d uc e d t h e fi r s t s t or e d e le c t r o n a n d p o s it ron because the power radiated increases as the fourth power of high-energy proton synchrotron for fixed-target physics would be in the forward directions at a hadron collider. College London, beams less than one year later – a far cry from the time it takes the beam energy and the inverse fourth power of mass, so is and the other using the technique proposed at MURA to T h i s le d t o t h e S pl it F ie ld M a g n e t f a c i l it y a s o n e o f t h e fi r s t and Peter Jenni today’s machines to go from conception to operation! From negligible for protons compared with electrons. build an innovative colliding beam proton machine with d e t e c t or s at t h e ISR, pr o v id i n g a h i g h m a g n e t ic fie ld i n t he (former ATLAS about the same centre-of-mass energy as a conventional forward directions but a negligible one at large angle with spokesperson), these trailblazers evolved the production machines, begin- Albert Ludwig ning with ADONE at Frascati and SPEAR at SLAC. However, A step into the unknown proton synchrotron of much larger dimensions. In order to respect to the colliding beams (the nowadays so-important University of it was always clear that the gift of synchrotron-radiation Meanwhile, in the early 1960s, discussion raged at CERN resolve the conflict, in February 1964, 50 physicists from transverse direction). It was with subsequent detectors Freiburg and CERN. damping would become a hindrance to achieving very high about the next best step for particle physics. Opinion was among Europe’s best met at CERN. From that meeting featuring transverse spectrometer arms over limited

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FEATURE 50 YEARS OF HADRON COLLIDERS FEATURE 50 YEARS OF HADRON COLLIDERS

interactions, for which Sheldon Glashow, and CERN-PHOTO-7708541X Steven Weinberg were to receive the in Physics in 1979. The electroweak theory predicted the existence and approximate masses of two vector bosons, the W and the Z,

CERN-PHOTO-201802-030 which were too high to be produced in any existing machine. However, and collaborators proposed that, if the SPS could be converted into a collider with protons and antiprotons circulating in opposite directions, there would be enough energy to create them. To achieve this the SPS would need to be converted into a like the ISR, but this time the beam would need to be kept “bunched” with the radio-frequency (RF) system working continuously to achieve a high enough luminosity (unlike the ISR where the beams were allowed to de-bunch all around the ring). The challenges here were two-fold. Noise in the RF system causes particles to diffuse rapidly from the bunch. This was solved by a dedicated feedback system. It was also predicted that the beam–beam interaction would limit the performance of a bunched-beam machine with no synchrotron-radiation damping due to the strongly nonlinear interactions between a p a r t ic le i n o n e b e a m w it h t h e g lo b a l e le c t r o m a g n e t ic fie ld in the other beam. A much bigger challenge was to build an accumulator ring in which antiprotons could be stored and cooled by later generation experiments because of its inherent lack First steps s t o c h a s t ic c o ol i n g u nt i l a s u ffic ie nt i nt e n s it y o f a nt i pr o t o ns of azimuthal symmetry. UA2 featured a (at the time) highly The R702 would be available to transfer into the SPS, accelerate to segmented electromagnetic and hadronic calorimeter in experiment at the around 300 GeV and collide with protons. This was done the central part (down to 40 degrees with respect to the ISR in 1977. in two stages. First a proof-of-principle was needed to beam axis), with 240 cells pointing to the interaction region. Big beast solid angles that physicists observed a large excess of SPS opens new era show that the ideas developed at the ISR transferred to a But it had no muon detection, and in its initial phase only The Large Hadron high transverse momentum particles above low-energy However, events were unfolding at CERN that would pave dedicated accumulator ring specially designed for sto- limited electromagnetic coverage in the forward regions. Collider in 2018. e x t r a p ol at io n s. W it h t h e s e fi r s t o b s e r v at io n s o f p oi nt-l i ke the way to the completion of the Standard Model. At the chastic cooling. This ring was called the Initial Cooling There was no magnetic field except for the forward cones parton scattering, the ISR made a fundamental contribu- ISR in 1972, the phenomenon of Schottky noise (density Experiment (ICE), and operated at CERN in 1977–1978. In with toroids to probe the W polarisation. tion to strong-interaction physics. Solid angles were too fluctuations due to the granular nature of the beam in a ICE transverse cooling was applied to reduce the beam size In 1983 the Spp–S experiments made history with the limited initially, and single-particle triggers too biased, storage ring) was first observed. It was this very same and a new technique for reducing the momentum spread direct discoveries of the W and Z. Many other results were to fully appreciate the hadronic jet structure. That feat noise that speculated in a paper a few in the beam was developed. The experiment proved to be a o b t a i n e d, i n c lud i n g t h e fi r s t e v id e n c e o f n e ut r a l B-m e son required third-generation detectors, notably the Axial Field years earlier could be used for what he called “stochastic bi g s uc c e s s a n d t h e t h e or y o f s t o c h a s t ic c o ol i n g w a s r e fi n e d particle– mixing at UA1 thanks to its track- Spectrometer (AFS) at the end of the ISR era, offering full cooling” of a proton beam, beating Liouville’s theorem by to a point where a real accumulator ring (the Antiproton ing and muon detection. The calorimetry of UA2 provided azimuthal central calorimeter coverage. The experiment the fact that a beam of particles is not a continuous fluid. Accumulator) could be designed to accumulate and store immediate unambiguous evidence for a two-jet structure provided evidence for the back-to-back two-jet structure Although it is unrealistic to detect the motion of individual antiprotons produced at 3.5 GeV by the proton beam from in events with large transverse energy. Both UA1 and UA2 of hard parton scattering. particles and damp them to the nominal orbit, van der Meer the 26 GeV Proton Synchrotron. First collisions of protons pushed QCD studies far ahead. The lack of hermeticity in For the detector builders, the original AFS concept was showed that by correcting the mean transverse motion and antiprotons at 270 GeV were observed on the night of UA2’s forward regions motivated a major upgrade (UA2′) interesting as it provided an unobstructed phi-symmetric of a sample of particles continuously, and as long as the 10 July 1981, signalling the start of a new era in colliding for the second phase of the collider, complementing the m a g n e t ic fie ld i n t h e c e nt r e o f t h e d e t e c t or, h o w e v e r, atthe s t at i s t ic a l n at u r e o f t h e S c h o t t k y s i g n a l w a s c o nt i nuo u s l y beam physics. central part with new fully hermetic calorimetry (both price of massive Helmholtz coil pole tips obscuring the for- regenerated, it would be theoretically possible to reduce the A clear physics goal, namely the discovery of the W and electromagnetic and hadronic), and also inserting a new ward directions. Indeed, the ISR enabled the development beam size and increase its density. With the bandwidth of Z intermediate vector bosons, drove the concepts for the t r a c k i n g c yl i n d e r e m plo y i n g n o v e l t e c h n olo g ie s (fi br e t r a ck- of many original experimental ideas. A very important electronics available at the time, van der Meer concluded two main Spp–S experiments UA1 and UA2 (in addition to a ing and silicon pad detectors). This enabled the experiment one was the measurement of the total cross section using that the cooling time would be too long to be of practical few smaller, specialised experiments). It was no coinci- to improve searches for top quarks and supersymmetric very forward detectors in close proximity to the beam. i mp or t a nc e. B ut t h e c h a l le n g e w a s t a k e n up b y Wol f g a n g dence that the leaders of both collaborations were pioneers particles, as well as making almost background-free first These “Roman Pots”, named for their inventors, made their Schnell, who built a state-of-the-art feedback system of ISR experiments, and many lessons from the ISR were precision measurements of the W mass. At the time appearance in all later hadron colliders, confirming the that demonstrated of a proton beam taken on board. UA1 pioneered the concept of a hermetic the Spp–S was rising total pp cross section with energy. for the first time. This would open the door to the idea of detector that covered as much as possible the full solid Meanwhile in America driving new It is easy to say after the fact, still with regrets, that with s t a c k i n g a n d c o ol i n g o f a nt i pr o t o n s, w h ic h l at e r le d t o t h e angle around the interaction region with calorimetry and At the time the Spp–S was driving new studies at CERN, the First collisions studies at CERN, an earlier availability of more complete and selective (with SPS being converted into a proton–antiproton collider. tracking. This allows measurements of the missing trans- first large superconducting synchrotron (the Tevatron, with of protons and electron-trigger capability) second- and third-generation Another important step towards the next generation of verse energy/momentum, signalling the escaping neu- a design energy close to 1 TeV) was under construction at the first large antiprotons at experiments at the ISR, CERN would not have been left as a hadron colliders occurred in 1973 when the collaboration trino in the leptonic W decays. Both electrons and muons Fermilab. In view of the success of the stochastic cooling superconducting 270 GeV were spectator during the famous November revolution of 1974 with working on the heavy-liquid were measured, with tracking in a state-of-the-art drift experiments, there was a strong lobby at the time to halt synchrotron observed on the J/ψ d i s c o ve r ie s at Bro o k h a ve n a nd SL AC. The s e, a nd t he p u bl i s h e d t w o p a p e r s r e v e a l i n g t h e fi r s t e v id e n c e for w e ak chamber that provided bubble-chamber-like pictures of the construction of the Tevatron and to divert effort instead was under the night of ϒ resonances discovered at Fermilab three years later, were neutral currents. These were important observations in the interactions. The magnetic field was provided by a to emulate the SPS as a proton–antiproton collider using construction 10 July 1981 clearly observed in the later-generation ISR experiments. s up p or t o f t h e u n i fie d t h e or y o f e le c t r o m a g n e t ic a n d w eak dipole-magnet configuration, an approach not favoured in the Fermilab Main Ring. Wisely this proposal was rejected at Fermilab

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FEATURE 50 YEARS OF HADRON COLLIDERS FEATURE 50 YEARS OF HADRON COLLIDERS

tation was a breath-taking evolution in real-time event Germany and the UK were unlikely to agree to the budget Fermilab s e l e c t io n (t r i g g e r i n g ) a n d d at a a c q u i s it io n t o k e e p up w it h increase required. On the positive side, after the demise t he increasing luminosit y of t he collider. of the SSC, a US panel on the future of particle physics CERN-HI-8104591 The physics harvest of the Tevatron experiments dur- recommended that “the government should declare its ing Run II was impressive, including a wealth of QCD intentions to join other nations in constructing the LHC”. measurements and major inroads in top-quark physics, Positive signals were also being received from , Japan h e a v y-fl a v o u r p h y s ic s a n d s e a rc h e s for p h e n o m e n a b eyond and Russia. t h e St a n d a rd M o d e l. St i l l s t a n d i n g s t r o n g a r e it s pr e c i s io n In June 1994 the proposal to build the LHC was made once measurements of the W and top masses and of the elec- more. However, approval was blocked by Germany and the 2 troweak mixing angle sin θW. The story ended in around UK, which demanded substantial additional contributions 201 2 w it h a g l i mps e of t he H ig g s b os on i n a ss o c i ate d pro- from the two host states, France and Switzerland. This duction with a . The CDF and D0 experience forced CERN to propose a “missing magnet” machine where influenced the LHC era in many ways: for example they only two thirds of the dipole magnets would be installed were able to extract the very rare single-top production i n a fi r s t s t a ge, a l lo w i n g o p e r at ion at re duc e d e ne r g y for a cross-section with sophisticated multivariate algorithms, number of years. Although costing more in the long run, and they demonstrated the power of combining mature the plan would save some 300 million Swiss Francs in the single-experiment measurements in common analyses first phase. This proposal was put to Council in December to achieve ultimate precision and sensitivity. 1994 by the new Director-General Christopher Llewellyn For t h e m a c h i n e b u i ld e r s, t h e pio n e e r i n g r ole o f t h e Te v a- Smith and, after a round of intense discussions, the pro- tron as the first large superconducting machine was also ject was finally approved for two-stage construction, to essential for further progress. Two other machines – the be reviewed in 1997 after non-Member States had made R e l at i v i s t ic He a v y Io n C ol l id e r at Br o o k h a v e n a n d t h e e le c- known their contributions. The first country to do so was tron–proton collider HERA at DESY – derived directly from Japan in 1995, followed by India, Russia and Canada the the experience of building the Tevatron. Lessons learned next year. A final sting in the tail came in June 1996 when from that machine and from the Spp–S w e r e a l s o i nt e g r at e d Germany unilaterally announced that it intended to reduce into the design of the most powerful hadron collider yet its CERN subscription by between 8% and 9%, prompting built: t he LHC. the UK to demand a similar reduction and forcing CERN to take out loans. At the same time, the two-stage plan was The Large Hadron Collider dropped and, after a shaky start, the construction of the The LHC had a difficult birth. Although the idea of a large full LHC was given the green light. proton–proton collider at CERN had been around since The fact that the LHC was to be built at CERN, mak- at least 1977, the approval of the Superconducting Super ing full use of the existing infrastructure to reduce cost, Collider (SSC) in the US in 1987 put the whole project into imposed a number of strong constraints. The first was doubt. The SSC, with a centre-of-mass energy of 40 TeV, t he 27 km-circumference of the LEP tunnel in which the was almost three times more powerful than what could machine was to be housed. For the LHC to achieve its ever be built using the existing infrastructure at CERN. design energy of 7 TeV per beam, its bending magnets It was only the resilience and conviction of Carlo Rubbia, w o u ld n e e d t o o p e r at e at a fie ld o f 8.3 T, about 60% higher Chasing bosons and construction of the Tevatron continued. It came into who shared the 1984 with van der than ever achieved in previous machines. This could only the luminosity followed, and the LHC physics programme, Top results The UA1 detector operation as a fixed-target synchrotron in 1984. Two years Meer for the project leading to the discovery of the W and be done using affordable superconducting material by at an initial energy of 3.5 TeV per beam, began in earnest The Tevatron’s at the Spp–S. later it was also converted into a proton–antiproton collider Z bosons, that kept the project alive. Rubbia, who became r e d uc i n g t h e t e m p e r at u r e o f t h e l iq u id-h e l iu m c o ol a nt f r o m in March 2010. CDF detector. and operated at the high-energy frontier until its closure Director-General o f C E R N i n 1989, a r g ue d t h at, i n s pit e o f its normal boiling point of 4.2 K to 1.9 K – where helium in September 2011. its lower energy, the LHC could be competitive with the exists in a macroscopic with the loss of LHC experiments A huge step was made with the detector concepts for S S C b y h a v i n g a lu m i n o s it y a n ord e r o f m a g n it ud e h i g h e r, viscosity and a very large thermal conductivity. A second Yet a whole other level of sophistication was realised by the the Tevatron experiments, in terms of addressed physics and at a fraction of the cost. He also argued that the LHC major constraint was the small (3.8 m) tunnel diameter, LHC detectors compared to those at previous colliders. The signatures, sophistication and granularity of the detector would be more versatile: as well as colliding protons, it which made it impossible to house two independent rings priority benchmark for the designs of the general-purpose components. This opened new and continuously evolving would be able to accelerate heavy ions to record energies like the ISR. Instead, a novel and elegant magnet design, detectors ATLAS and CMS was to unambiguously discover avenues in analysis methods at hadron colliders. Already at litt le e x tra cost. first proposed by Bob Palmer at Brookhaven, with the (or r u le o ut) t h e St a n d a rd M o d e l H i g g s b o s o n for a l l p o s s i ble the initial CDF and D0 detectors for Run I (which lasted until The SSC was eventually cancelled in 1993. This made the two rings separated by only 19 cm in a common yoke and masses up to 1 TeV, which demanded the ability to measure 1996) were designed with cylindrical concepts, characteristic case for t he LHC even st ronger, but t he financial climate cryostat was developed. This also considerably reduced a v a r ie t y o f fi n a l s t at e s. T h e c h a l le n g e s for t h e H i g g s s e arch o f w h at w e n o w c a l l g e n e r a l-p u r p o s e c ol l id e r e x p e r i m e nt s, in Europe at the time was not conducive to the approval of the cost. also guaranteed the detectors’ potential for all kinds of albeit D0 s t i l l w it h o ut a c e nt r a l m a g n e t ic fie ld i n c o nt r a s t t o a large project. For e xample, CERN’s largest cont ributor, At precisely 09:30 on 10 September 2008, almost 15 years searches for physics beyond the Standard Model, which C DF’s 1.4 T s ole n oid. I n 1995 t h e e x p e r i m e nt s d e l i v e r e d t h e Germany, was struggling with the cost of reunification after the project’s approval, the first beam was injected was the other driving physics motivation at the energy first Tevatron highlight: the discovery of the top quark. Both and many other countries were getting to grips with the into the LHC, amid global media attention. In the days that frontier. These two very ambitious LHC detector designs d e t e c t or s u n d e r w e nt m aj or up g r a d e s for Ru n II (2001–201 1) introduction of the single European currency. In December followed good progress was made until disaster struck: integrated all the lessons learned from the experiments at – a t heme now se en for t he LHC e x p er i me nt s – w h ic h h ad 1993 a plan was presented to the CERN Council to build during a ramp to full energy, one of the 10,000 supercon- the three predecessor machines, as well as further tech- a great impact on the Tevatron’s physics results. CDF was the machine over a 10-year period by reducing the other ducting joints between the magnets failed, causing exten- nology advances in other large experiments, most notably equipped with a new tracker, a silicon vertex detector, new e x p e r i m e nt a l pr o g r a m m e s at C E R N t o t h e a b s olut e m i n- sive damage which took more than a year to recover from. at HERA and LEP. for w a rd c a lor i m e t e r s a n d muo n d e t e c t or s, w h i le D 0 added imum, with the exception of the full exploitation of the Following repairs and consolidation, on 29 November 2009 Just a few simple numbers illustrate the giant leap from a 1.9 T central solenoid, vertexing and fibre tracking, and fl a g s h i p L a r g e E le c t r o n P o s it r o n (L E P) c ol l id e r. A lt h ough beam was once more circulating and full commissioning the Tevatron to the LHC detectors. CDF and D0, in their new forward muon detectors. Alongside the instrumen- t h e pl a n w a s g e n e r a l l y w e l l r e c e i v e d, it b e c a m e c le a r t h at and operation could start. Rapid progress in ramping up upgraded versions operating at a luminosity of up to

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FEATURE 50 YEARS OF HADRON COLLIDERS

that there are no strict boundaries between these three physics fields for them. All of them have learned to use features of their instruments to contribute at least in part to the full physics spectrum offered by the LHC, of which

CER N-PHO T O-201907-204 the highlight so far was the July 2012 announcement of the discovery of the Higgs boson by the ATLAS and CMS collaborations. The following year the collaborations were named in the citation for the 2013 Nobel Prize in Physics awarded to François Englert and . Since then, the LHC has exceeded its design luminosity by a factor of two and delivered an integrated luminosity of almost 200 fb–1 in proton–proton collisions, while its beam energy was increased to 6.5 TeV in 2015. The machine has also delivered heavy ion (lead–lead) and even lead–proton collisions. But the LHC still has a long way to go before its estimated end of operations in the mid-to-late 2030s. To this end, the machine was shut down in November 2018 for a major upgrade of the whole of the CERN injector complex as well as the detectors to prepare for operation at high luminosities, ultimately up to a “levelled” luminosity of 7 × 1034 cm–2 s–1. The High Luminosity LHC (HL-LHC) upgrade is pushing the boundaries of superconducting magnet tech- nology to the limit, particularly around the experiments where the present focusing elements will be replaced by

new magnets built from high-performance Nb3Sn super- conductor. The eventual objective is to accumulate 3000 fb–1 Insert here 4 × 1032 cm–2 s–1, typically had around a million channels of integrated luminosity. The LHC’s CMS and a triggered event rate of 100 Hz, with event sizes of In parallel, the LHC-experiment collaborations are pre- experiment 500 kB. The collaborations were each about 600 strong. paring and implementing major upgrades to their detectors undergoing By contrast, ATLAS and CMS operated during LHC Run 2 using novel state-of-art technologies and revolutionary upgrades in 2019. at a luminosity of 2 × 1034 cm–2 s–1 with typically 100 million approaches to data collection to exploit the tenfold data RELIABLE readout channels, and an event rate and size of 500 Hz volume promised by the HL-LHC. Hadron-collider detector and 1500 kB. Their publications have close to 3000 authors. concepts have come a long way in sophistication over the You know what For many major LHC-detector components, comple- past 50 years. However, behind the scenes are other fac- UNDER ALL mentary technologies were selected. This is most visible tors paramount to their success. These include an equally you want to detect: for the superconducting magnet systems, with an elegant s p e c t a c u l a r e v olut io n i n d at a-flo w a rc h it e c t u r e s, s o f t w a r e CONDITIONS. and unique large 4 T solenoid in CMS serving both the and the computing approaches, and analysis methods – muon and inner tracking measurements, and an air-core all of which have been driven into new territories by the - X-rays toroid system for the muon spectrometer in ATLAS together extraordinary needs for dealing with rare events within Heading into the unknown to open new horizons with a 2 T solenoid around the inner tracking cylinder. the huge backgrounds of ordinary collisions at hadron col- - Gamma-rays demands reliable tools. Help turn your resarch These choices drove the layout of the active detector com- liders. Worthy of particular mention in the success of all - Neutrons goals into reality. ponents, for instance the electromagnetic calorimetry. LHC physics results is the Worldwide LHC Computing Grid. Vacuum valve solutions and bellows Here again, different technologies were implemented: a This journey is now poised to continue, as we look ahead - Particles from VAT provide unfailing reliability novel-configuration liquid-argon sampling calorimeter towards how a general-purpose detector at a future 100 TeV and enhanced process safety – for ATLAS and lead-tungstate crystals for CMS. hadron collider might look like. From the outset, the LHC was conceived as a highly ver- under all conditions. satile collider facility, not only for the exploration of high Beyond the LHC This journey is transverse-momentum physics. With its huge production Although the LHC has at least 15 years of operations ahead of now poised to o f b a n d c q u a r k s, it offe r e d t h e p o s s i bi l it y o f a v e r y f r u it ful it, t h e q ue s t io n n o w a r i s e s, a s it d id i n 1964: w h at i s t h e n e x t continue, pr o g r a m m e i n fl a v o u r p h y s ic s, e x ploit e d w it h g r e at s uc c es s t e p for t h e fie ld? T h e C E R N C o u n c i l h a s r e c e nt l y a p proved as we look by the purposely designed LHCb experiment. Furthermore, the recommendations of the 2020 update of the European in special runs the LHC provides heavy-ion collisions for strategy for particle physics, which includes, among other ahead towards studies of the quark–gluon plasma – the field of action for things, a thorough study of a very high-energy hadron how a general- the ALICE experiment. collider to succeed the LHC. A technical and financial fea- purpose As the general-purpose experiments learned from the sibility study for a 100 km circular collider at CERN with a SCIONIX Holland B.V. detector at history of experiments in their field, the concepts of both collision energy of at least 100 TeV is now under way. While a a future Tel. +31 30 6570312 LHCb and ALICE also evolved from a previous generation decision to proceed with such a facility is to come later this We know how to 100 TeV hadron of experiments in their fields, which would be interesting d e c a d e, o n e t h i n g i s c e r t a i n: le s s o n s le a r n e d f r o m 50 y e a r s o f Fax. +31 30 6567563 collider might to trace back. One remark is due: the designs of all four experience with hadron colliders and their detectors will be Email. [email protected] build your detectors look like m a i n d e t e c t or s at t h e L HC h a v e t u r n e d o ut t o b e s o fle x i ble crucial to the success of our next step into the unknown.  www.scionix.nl

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FEATURE LHC PUBLICATIONS A DECADE IN LHC PUBLICATIONS The first 10 years of LHC operations have generated a bumper crop of new knowledge. dr a id Dav ré nd A 400 700 LHCb publications by LHC collaborations 600 CMS 500 300 ATLAS 400 ALICE 300 200 200

of submissions 100 100 cumulative number 0 –100 0 Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct 2016 2016 2016 2016 2017 2017 2017 2017 2018 2018 2018 2018 2008 2010 2012 2014 2016 2018 2020 date 2852 papers from experiment From the first publications in 2008 750 shades of model building There was a major influx of papers from that described the detector designs, through 2012’s discovery of the the theory community when hints of a 750 GeV resonance were found by Higgs boson, all the way to CMS’s 1000th publication in 2020. the LHC experiments – only to turn out to be a statistical fluctuation.

n June 2020, the CMS collaboration submitted a paper THE AUTHORS entific relevance of the LHC. There were tens of thousands titled “Observation of the production of three massive Alex Kohls, of additional papers published over the past decade that Igauge bosons at √s = 13 TeV” t o t h e a r X i v pr e pr i nt s e r v e r. Jens Vigen and mention the LHC experiments, use their data or are based A s c ie nt i fic h i g h l i g ht i n it s o w n r i g ht, t h e p a p e r a l s o m arked Micha Moskovic on the LHC’s findings. The papers published by the four the collaboration’s thousandth publication. ATLAS is not CERN. major experiments received on average 112 citations per far from reaching the same milestone, currently at 964 paper, compared to an average of 41 citations per paper publications (data correct as of 7 January). With the rest of across all experimental papers indexed in INSPIRE and t h e L HC e x p e r i m e nt s t a k i n g t h e t o t a l nu m b e r o f p a p e r s t o even 30 citations per paper across all HEP publications 2852, the first 10 years of LHC operations have generated (4.8 million citations across 163,000 documents since 2008). a bumper crop of new k nowledge. Unsurprisingly, the number of citations peaks with the T h e p u bl ic at io n l a n d s c a p e i n high-energy p h y s ic s (H E P) CMS and ATLAS papers on the Higgs-boson discovery, i s e x c e p t io n a l d ue t o a long-held pr e pr i nt c u lt u r e. A t C E R N, w it h 10,910 a n d 1 1,195 c it at io n s, r e s p e c t i v e l y, w h ic h at t h e paper copies were kept in cabinets outside the library from end of 2019 were the two most cited high-energy physics the 1950s onwards, but since the early a growing papers released in t he past decade. nu m b e r h a v e b e e n s t or e d e le c t r o n ic a l l y at arXiv.org. P r e- Large author numbers are another exceptional aspect of print posting and actual journal publication often happen LHC-experiment p u bl i s h i n g, w it h p a p e r s c o n s i s t e nt l y c a r r y- at t h e s a m e t i m e, a n d c it at io n s b e t w e e n a l l t y p e s o f p u bl i- i n g hu n d r e d s or e v e n t h o u s a n d s o f n a m e s. T h i s c u l m i n at e d cations are compiled and counted in the INSPIRE system. in a world record of 5154 authors on a joint paper between Particle physics has fully embraced the open-science CMS and ATLAS in 2015, which reduced the uncertainty movement, in publishing, software, hardware and, most on the measurement of the Higgs-boson mass to ±0.25%. recently, data. In 2004 former Director-General Robert Ten years of LHC publications have established the Aymar encouraged the creation of SCOAP3 (Sponsoring Standard Model at unprecedented levels of precision. But Consortium for Publishing in Particle Phys- the hunger for new physics is clear (see “750 shades of ics) at CERN. Devoted to converting closed access HEP m o d e l b u i ld i n g” fi g u r e). O n 15 D e c e m b e r 2015, AT L A S and journals to open access, SCOAP3 has grown extensively CMS presented data that hinted at an excess of events at and now has more than 3000 libraries from 44 different 750 GeV in proton collisions, fuelling hopes that a new countries. All original LHC research results have been pub- particle might be showing itself. While the significance lished open access. The first collaboration articles by the o f t h e e x c e s s w a s o n l y 2 σ a n d 1.6 σ, respectively, theorists four main ex periments, describing t he detector desig ns, w e r e q u ic k t o r e s p o n d w it h a n i n flu x o f hu n d r e d s o f p a p ers. and published in the Journal of Instrumentation, remain This excitement was, however, damped by the release of amongst the most cited articles from LHC collaborations the August 2016 data, where there was no further sign of a nd – despite b ei ng more t ha n a dec ade old – a re some of the anomaly, and it became commonly recognised as a Large author t he most recent ly read ar t icles of t he jour nal. statistical fluctuation – part and parcel of the scientific Si n c e t h e n, a lo n g w it h t h e 2 852 p u bl ic at io n s b y t h e L HC numbers process, if r uining t he fun for t he t heorists. experiments, some 380 papers have been written by indi- are another Wit h t he LHC to cont i nue op er at ions to t he m id-2030s, viduals on behalf of the collaboration. A further 10,879 exceptional and only around 6% of its expected total dataset collected articles (preprints, conference proceedings, etc) from the aspect of LHC- so far, we can look forward to thousands more publica- LHC experiments were not published in a peer-reviewed experiment tions about nature’s basic constituents being placed in j o u r n a l. Ho w e v e r, t h i s s t i l l r e pr e s e nt s o n l y p a r t o f t h e s c i- publishing the public domain. 

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Supporting particles physics with Innovation OPINION clean technology With a skilled and competent R&D team, we can engineer innovative innovations solutions to complex requirements. VIEWPOINT Quality

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and having the skill M Polykapoulou Audiences never look at particle physics to provide a bespoke SCAN ME FOR with the same eyes once they’ve learned solution, is something” MORE INFO about its wider applications, says Senior Vacuum Engineer Barbora Bruant Gulejova

Science and basic research are drivers of technologies and innovations, which in B Gulejova turn are key to solving global challenges such as climate change and energy. The United Nations has summarised these challenges in 17 “sustainable develop- Call +44 (0)1524 812 899 Email [email protected] ment goals”, but it is striking how little connection with science they include. Furthermore, as found by a UNESCO study Barbora Bruant DESIGN & BUILD CONSUMABLES & EQUIPMENT VALIDATION & TESTING in 2017, the interest of the younger gen- Gulejova eration in studying science, technology, Hands on A high-school student analysing ATLAS collisions during World Wide is strategic The UK and Europe’s leading provider of integrated cleanroom solutions since 2002 www.connect2cleanrooms.com engineering and mathematics is falling, Data Day organised under the umbrella of IPPOG, Serres, . development lead despite jobs in these areas growing at a for the International rate three times faster than in any other Some in the community are resistant to tor technology. In the environmental Particle Physics sector. Clearly, there is a gulf between communicate physics spin-offs because arena, recent CERN spin-offs include a Outreach Group, and scientists and non-scientists when it this is not our primary purpose. Yet, mil- global network of air-quality sensors and former industry and comes to the perception of the impor- lions of people who have lost their income fibre-optic sensors for improved water knowledge-transfer tance of fundamental research in their as a result of COVID-19 are rather more and pesticide management, while CERN liaison officer for lives – to the detriment of us all. concerned about where their next rent open-source software is used for digital with CERN. Try asking your neighbours, kids, family and food payments are coming from, than preservation in libraries and its computing members or mayor of your city whether they are about the couplings of the Higgs resources have been heavily deployed in they know about the medical and other boson. Reaching out to non-physicists is fight ing t he pandemic. applications that come from particle phys- more important than ever, especially to ic s, or t h e s t r e a m o f h i g h l y q u a l i fie d p e o pl e t h o s e w it h a n i n d i ffe r e nt or e v e n n e g a t i ve Building trust trained at CERN who bring their skills to a t t it u d e t o s c i e n c e. D i ffe r e nt i a t i n g a u di- Credibility and trust in science can only business and industry. While the majority ences between students, general pub- be built by scientists themselves, while of young people are attracted to physics by lic and politicians is not relevant when working hand in hand with professional its mindboggling findings and intriguing addressing non-scientifically educated communicators, but not relying only on open questions, our subject appeals even people. Strategic information should be them. Extracurricular activities, such more w he n i nd iv idua l s fi nd out a b out it s proactively communicated to all stake- as those offered by IPPOG, CERN, other usefulness outside academia. This was holders in society in a relatable way, via institutions and individual initiatives, one of the key outcomes of a recent survey, eye-opening, surprising and emotionally are crucial in changing the mispercep- Creating Ambassadors for Science in Society, charged stories about the practical appli- tions of the public and bringing about organised by the International Particle cations of curiosity-driven discoveries. fact-based decision-making to the young Physics Outreach Group (IPPOG). IPPOG has been working to provide generation. Scientists should develop a Do most “Cernois” even know about such stories since 2017 – and there is no proactive strategic approach and even the numerous start-ups based on CERN shortage of examples. Take the touch- consider becoming active in policy mak- technologies or the hundreds of technol- screen technology first explored at CERN ing, following the shining examples of ogy disclosures from CERN, 31 of which 40 years ago, or humanitarian satellite those who helped realise the SESAME came in 2019 alone? Or about the numer- mapping carried out for almost 20 years light source in the Middle East and the ous success stories contained within the by UNOSAT, which is hosted at CERN. South East European International Insti- Reaching CERN impact brochure and the many Millions of patients are diagnosed daily tute for Sustainable Technologies. out to non- resources of CERN’s knowledge-transfer thanks to tools like PET and MRI, while Particle physics already inspires some physicists group? Even though “impact” is gaining more recent medical developments include of the brightest minds to enter science. attention, anecdotally when I presented innovative radioisotopes from MEDICIS But audiences never look at our subject is more these facts to my research colleagues they for pr e c i s i o n m e d i c i n e, t h e fi r s t 3 D c ol o ur with the same eyes once they’ve learned important were not fully aware. Yet who else will X-ray images, and novel cancer treatments about its applications and science-for- than ever be our ambassadors, if not us? based on superconducting accelera- peace initiatives.

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Still seeking solutions

Steven Weinberg reflects on the , effective field theory, and his latest attempt to understand the fermion mass hierarchy.

How did winning a Special Valentine M be correct. So I was very pleased that Breakthrough Prize last year the Breakthrough Prize acknowledged compare with the Nobel Prize? some of those things that didn’t lead It came as quite a surprise because to specific predictions but changed a as far as I know, none of the people general framework. who have been honoured with the Breakthrough Prize had already You coined the term effective received the Nobel Prize. Of course field theory (EFT) and recently nothing compares with the Nobel Prize inaugurated the online lecture series in prestige, if only because of the long All Things EFT. What is the importance history of great scientists to whom it of EFT today? has been awarded in the past. But the My thinking about EFTs has always Breakthrough Prize has its own special been in part conditioned by thinking value to me because of the calibre of about how we can deal with a the young – well, I think of them as quantum theory of gravitation. You young – theoretical physicists who are can’t represent gravity by a simple really dominating the field and who renormalisable theory like the make up the selection committee. Standard Model, so what do you do? In fact, you treat general relativity The prize committee stated that you the same way you treat low-energy would be a recognised leader in the pions, which are described by a low- field even if you hadn’t made your energy non-renormalisable theory. seminal 1967 contribution to the (You could say it’s a low-energy limit genesis of the Standard Model. W hat do of QCD but its ingredients are totally you view as Weinberg’s greatest hits? different – instead of quarks and There’s no way I can answer that gluons you have pions). I showed how and maintain modesty! That work you can generate a power series for any on the electroweak theory leading given scattering amplitude in powers to the mass of the W and Z, and the of energy rather than some small existence and properties of the Higgs, coupling constant. The whole idea of was certainly the biggest splash. But it EFT is that any possible interaction was rather untypical of me. My style is is there: if it’s not forbidden it’s usually not to propose specific models compulsory. But the higher, more that will lead to specific experimental Deep mind Steven Weinberg is director of the theory research complicated terms are suppressed by predictions, but rather to interpret group, University of Texas at Austin. negative powers of some very large in a broad way what is going on and mass because the dimensionality of make very general remarks, like with the cosmological constant before the the coupling constants is such that the development of the point of view discovery of the accelerated expansion they have negative powers of mass, associated with effective field theory. of the universe. I worried about that – like the gravitational constant. That’s Doing this I hope to try and change I gave a series of lectures at Harvard why they’re so weak. the way my fellow physicists look at in which I finally concluded that the If you recognise that the Standard things, without usually proposing only way I can understand why there Model is probably a low-energy limit any t hing specific. I have occasionally isn’t an enormous vacuum energy is of some more general theory, then made predictions, some which actually because of some kind of anthropic you can consider terms that make www.ipac21.org worked, like calculating the pion– I wish I selection. Together with two guys the theory non-renormalisable here at Austin, Paul Shapiro and nucleon and pion–pion scattering could claim and generate corrections to it. In lengths in the mid-1960s using the Hugo Martel, we worked out what particular, the Standard Model has this broken symmetry that had been that I had was the most likely value that beautiful feature that in its simplest proposed by Nambu. There were other predicted the would be found in terms of order of renormalisable version there are things, like raising the whole issue of neutrino mass magnitude, which was later found to symmetries that are automatic: at least

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OPINION INTERVIEW

to all orders of perturbation theory, CERN order t he mass would be finite. I w rote it can’t violate the conservation of a paper, but then I just gave it up after baryon or . But if the no progress, until now when I went Standard Model just generates the bac k to it, no longer young, and ag first term in a power series in energy I found models in whic h you do have and you allow for more complicated an accidental symmetry. Now the idea non-renormalisable terms in the is not just the muon and the electron, Lagrangian, then you find it’s very but t he t hird generat ion feeding dow n natural that there would be baryon to g ive masses to t he second, whic h and lepton non-conservation. In would then feed down to give masses fact, the leading term of this sort is to the first. Others have proposed what a term that violates lepton number might be a more promising idea, that • Full Beamline Solutions and g ives neut rinos t he masses we the only mass that isn’t zero in the tree observe. I wish I could claim that I approx imat ion is t he top mass, whic h • Accelerator and Neutron Instrumentation had predicted the neutrino mass, but is so much bigger than the others, there already was evidence from the and everything else feeds down • Monochromator and Mirror Systems solar neutrino deficit and also it’s not from that. I just wanted to show the certain that this is the explanation of kinds of cancellations in infinites • High Stability Cryo Coolers neutrino masses. We could have Dirac that can occur, and I worked out neut rinos in whic h you have lef t and the calculations. I was hoping Sub-20nrad • Experimental Stations right neutrinos and antineutrinos t hat when t his paper came out some Stability Achieved coupling to the Higgs, and in that bright young physicist would come up • Insertion Devices way get masses without any violation with more realistic models, and use Two Horizontal-Bounce Cryo-Cooled DCMs of lepton-number conservation. these calculational techniques – that for Diamond Light Source DLS • Professional Engineering Support But I find t hat t horoughly repulsive hasn’t happened so far but it’s still because there’s no reason in that case pretty early. why the neutrino masses should be so smal l, whereas in t he EFT case we What other inroads are there to the have Majorana neutrinos whose small mass/flavour hierarchy problem? Axilon AG • Emil-Hoffmann Str. 55-59 • 50996 Köln • Germany • +49 (221) 165 324 00 • [email protected] • www.axilon.de masses are much more natural. EffectiveWeinberg delivering a special seminar at CERN in The hope would be that December 1979, the year he won the Nobel Prize and published experimentalists discover some On this point, doesn’t the small value a seminal paper on effective field theory. correction to the Standard Model. of the cosmological constant and The problem is that we don’t have Higgs mass undermine the EFT view cosmological constant, maybe that’s a theory that goes beyond the Clean-Critical Fastener & Seal Solutions by pointing to extreme fine-tuning? t he answer w it h t he Higgs mass – Standard Model, so what we’re doing HV, UHV, EUV, Cleanroom Ready Fasteners and Seals Yes, they are a warning about things maybe it’s got to be small for anthropic is floundering around looking for we don’t understand. The Higgs reasons.” That’s very disturbing if it’s corrections in the model. So far, the in Just About Any Size, Material, and Finish to Meet Your Needs! mass less so, after all it’s only about a true, as we’re going to be left waving only one discovered w as t he neut rino hundred times larger than the proton our hands. But I don’t k now. mass and that’s a very valuable piece of  = Clean-tech standard  Custom solutions & prototypes mass and we k now why t he proton data whic h we so far have not fig ured All UC products arrive pre-cleaned, vacuum sealed,  Exceptional customer service mass is so small compared to the Early last year you posted a preprint out how to interpret. It definitely goes rigorously inspected, and ready to install  100% parts traceability GUT or Planck scale; it is because the “Models of lepton and quark masses” beyond the Standard Model – as I  = Clean-tech standard.  Vented, plated, baked, inspected, consistent NOTICE: proton gets it mass not from the quark in which you returned to the problem ment ioned, I t hin k it is a dimension- All UC products arrive pre-cleaned, vacuum sealed, masses, whic h have to do w it h t he of the fermion mass hierarchy. How five operator in the effective field rigorously inspected, and ready to installWebsite Upgrade Higgs, but from the QCD forces, and was it received? theory of which the Standard Model is  Vented, plated, baked, inspected, consistent @ we k now t hat t hose become st rong Even in t he abst ract I adver t ise how the renormalisable part.  Custom solutions & prototypes very slowly as you come down from this isn’t a realistic theory. It’s a The big question is whether we can high energy. We don’t understand problem t hat I first worked on almost cut off some sub-problem that we can  Exceptional customer service uccomponents.com t his for t he Higgs mass, whic h, a f ter 50 years ago. Just looking at the table of act ually solve w it h what we already  100% parts traceability  2D Sales Prints all, is a term in the Lagrangian, not masses I thought know. That’s what I was trying to do  Increased Resources li ke t he proton mass. But it may be that the electron and the muon were in my recent paper and did not succeed  Better Shopping Experience similar – that’s the old technicolour cr y ing out for an e x planat ion. The in getting anywhere realistically. If  Improved Navigation idea, that there is another coupling elect ron mass looks li ke a radiat ive that is not possible, it may be that we alongside QCD that becomes strong correction to the muon mass, so I can’t make progress without a much  Better Catalog at some energy where it leads to a spent the summer of 1972 on the deeper theory where the constituents  Live Chat potential for the Higgs field, which back deck of our house in Cambridge, are much more massive, something then breaks electroweak symmetry. where I said, “This summer I am going li ke st ring t heor y or an asy mptot ically Now, I don’t have such a theory, and if I to solve the problem of calculating sa fe t heor y. I st ill t hin k st ring t heor y did I wouldn’t know how to test it. But the electron mass as an order-alpha Maybe we is our best hope for the future, but this there’s at least a hope for that. Whereas correction to the muon mass.” I was have 2500 future seems to be much further away regards to the cosmological constant, I able to prove that if in a theory it was years ahead than we had hoped it would be. Then I can’t think of anything along that line natural in the technical sense that keep being reminded of Democrit us, of us before Call for a quote today! that would explain it. I think it was the electron would be massless in the who proposed t he e x istence of atoms Nima Arkani-Hamed who said to me, tree approximation as a result of an we get to the in around 400 BCE. Even as late as uccomponents.com (408) 782-1929 “If the anthropic effect works for the accidental symmetry, then at higher next big step 1900 physicists like Mach doubted

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OPINION INTERVIEW

SS Scientific have worked with some of the largest the existence of atoms. They didn’t think the Higgs might not couple to It’s still it became strong enough to produce become really nailed down until the all three generations? p ossible t h at a breakdown of the electroweak research facilities worldwide to produce products first years of t he 20t h cent ur y. So Before the Higgs was discovered something symmetry. This was pushed by Lenny for exacting requirements. maybe we have 2500 years a head of us it seemed quite possible that the Susskind and myself, independently. like before we get to the next big step. explanation of the hierarchy problem The problem with that theory was TRANSMISSION LINES, COAXIAL & WAVEGUIDE technicolour was that there was some new then: how did the quarks and leptons • Recently the LHC produced the first technicolour force that gradually i s t r ue get their masses? Because while it gave evidence that the Higgs boson became strong as you came from very a very natural and attractive picture PATCH PANELS & SPLITTERS Vacuum Safety Switch couples to a second-generation high energy to lower energy, and that of how the W and Z get their masses, it • fermion,Anz_spec_CERN_2-2021_sp the muon. Is there 08.02.21 reason to13:39 somewhere Seite 1 in the multi-TeV range left it really mysterious for the quarks CUSTOMISED RF COMPONENTS and leptons. It’s still possible that something like technicolour is true. Then the Higgs coupling to the quarks and leptons gives them masses just AWG + Digitizer in one box! as expected. But in the old days, when we took technicolour seriously as the Ideal for Stimulus-Response, mechanism for breaking electroweak symmetry, which, since the discovery Record/Replay, ATE and MIMO NEW! of the Higgs we don’t take seriously high-speed! anymore, even then there was the question of how, without a scalar field, • Installed at Diamond Light Source, Brookhaven can you give masses to the quarks National Laboratory & Australian Synchrotron and leptons. So, I would say today, it would be amazing if the quarks • Certified and Rated to SIL3 (IEC615081:2010) hybridNETBOX and leptons were not getting their with 4+4 channels masses from the expectation value (DN2.82x-04) www.exirbroadcasting.com of the Higgs field. It’s important now to see a very high precision test of all Exir Broadcasting AB t his, however, because small effects Industrigatan 17 - SE-242 31 Hörby - Sweden Thermal Outgassing System CCMarApr21Ad_MDC_QP_PROOF.pdf+46 415 30 14 00 - [email protected] 1 12/02/2021 09:00 Multi-channel signal generation + acquisition in one box coming from new physics might show 2+2 or 4+4 channels with 180 MS/s to 500 MS/s up as corrections. But these days any suggestion for future physics facilities AWG: 625 MS/s (4 channels) or 1.25 GS/s (2 channels) gets involved in international politics, AWG: up to ±2,5 V into 50 ohms (at 1.25 GS/s) which I don’t include in my area Digitizer: 6 input ranges: ±200 mV up to ±10 V of expertise. SDKs included: C++, Python, LabVIEW, MATLAB, JAVA etc. Any more papers or books in the pipeline? I have a book that’s in press at Cambridge University Press called hybridNETBOX Foundations of Modern Physics. with 8+8 channels It’s intended to be an advanced (DN2.80x-08) undergraduate textbook that takes you from the earliest work on atoms, through thermodynamics, transport theory, Brownian motion, to early Multi-channel signal generation + acquisition in one box quantum theory; then relativity and 2+2, 4+4 or 8+8 channels with 40 MS/s or 125 MS/s quantum mechanics, and I even AWG: output up to ±12 V into high impedance have two chapters that probably go beyond what any undergraduate would AWG: fixed trigger to output delay want, on nuclear physics and quantum Digitizer: single-ended or differential inputs field theory. It unfortunately doesn’t • Choice of vacuum hardware SDKs included: C++, Python, LabVIEW, MATLAB, JAVA etc. fit into what would normally be the • OFHC chamfered conductance plate plan for an undergraduate course, so I don’t know if it will be widely

adopted as a textbook. It was the SS Scientific deliver a range of high quality standard SPECTRUM result of a lecture course I was asked INSTRUMENTATION to give called “thermodynamics and customised vacuum components and systems. and quantum physics” that has been See our website www.s3vacuum.com for full Perfect fit – modular designed solutions taught at Austin for years. So, I said details. “alright”, and it gave me a chance Europe / Asia: Phone +49 (4102) 695 60 | US: Phone (201) 562 1999 to learn some thermodynamics and transport theory. Contact us today on www.spectrum-instrumentation.com +44 1323 638230 Interview by Matthew Chalmers. or email [email protected]

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The hitchhiker’s guide to weak decays S Berger tigation of beyond-the-SM sensitivity Gauge Theory of Weak Decays: on the other. These are precisely the two The Standard Model and the Expedition to New Physics Summits ingredients of Buras’s book. In the first part, he guides the reader though all the 27 SEPTEMBER-1 OCTOBER 2021 By Andrzej J Buras steps necessary to arrive to the most Cambridge University Press up-to-date predictions for rare decays. This part of the book offers different Most travellers know that it is essential to paths to different readers: students are have a good travel guide when setting out guided, in a very pedagogical way, from 1 into unexplored territory. A book where tree-level calculations to high-precision one can learn what previous travellers multi-loop calculations. Experienced @BSBF2021 #bsbf2021 discovered about these surroundings, readers can directly find up-to-date with both global information on the lan- phenomenological expressions that guage, history and traditions of the land summarise the present knowledge on Early Bird Registration: 30 April 2021 to be explored, and practical details on Don’t forget your towel Andrzej Buras’s new book is an virtually any process of current exper- how to overcome day-to-day difficulties. indispensable travel guide to unexplored territory in weak imental interest. This part of the book 1 Andrzej Buras’s recent book, Gauge Theory decays, writes our reviewer. can also be viewed as a well-thought-out of Weak Decays, is the ideal guide for both summary of the history of precise SM new physicists and seasoned travellers, CUP experiments, could indeed be the first calculations for weak decays, written by and experimentalists and theoreticians hint of new physics. The strategic role one of its most relevant protagonists. alike, who wish to start a new expedition that weak decays play in the search for The second part of the book is devoted into the fascinating world of weak meson new physics is further reinforced by the to physics beyond the SM. Here the style is decays, in pursuit of new physics. absence on the horizon, at least in the q u it e d i ffe r e nt: l e s s p e d a g o g i c a l a n d m ore The physics of weak decays is one of near future, of a collider with a centre-of- encyclopaedic. Employing a pragmatic the most active and interesting fron- mass energy exceeding that of the LHC, approach, which is well motivated to dis- tiers in particle physics, from both the while the LHC and other facilities still cuss low-energy processes, extensions of theoretical and the experimental points have a large margin of improvement in t h e S M a r e c l a s s i fie d a c c ord i n g t o pr o per- of view. Major steps in the construc- precision measurements. ties of hypothetical new heavy particles, tion of the Standard Model (SM) have As Buras describes with clarity, signals f r o m Z′ b o s o n s t o l e p t o q u a r k s, a n d f r o m been made possible only thanks to key of new physics in the weak decays of K, D, charged Higgs bosons to “vector-like” observations in weak decays. The most and B mesons, and other rare low-energy . This allows Buras to analyse the famous example is probably the sup- processes, could manifest themselves as impact of such models on rare processes pression of flavour-changing neutral deviations from the precise predictions in a systematic way, with great attention currents in decays, which led Gla- of the corresponding decay rates that we paid to correlations between observables. show, Iliopoulos and Maiani to postu- are able to derive within the SM. In the To my knowledge, this book is the first late, in 1970, the existence of the charm absence of a reference beyond-the-SM comprehensive monograph of this type, quark, well before its direct discovery. theory, it is not clear where, and at which covering far more than just the general But there are many other examples, level of precision, these deviations could aspects of SM physics, as may be found such as the heaviness of the top quark, show up. But general quantum field the- in many other texts on quantum field inferred from the large matter-to-anti- ory arguments suggest that weak decays theory. The uniqueness of this book lies matter oscillation frequency of neutral B are particularly sensitive probes of new in its precious details on a wide variety mesons, again well before its discovery. physics, as they can often be predicted of interesting rare processes. It is a key In the post-Higgs-discovery era, weak with high accuracy within the SM. reference that was previously missing, decays are a privileged observatory in The two necessary ingredients for a and promises to be extremely useful in which to search for signals of physics journey in the realm of weak decays are the coming decades. beyond the SM. The recent “B-physics therefore precise SM predictions on the anomalies”, reported by LHCb and other one hand, and a broad-spectrum inves- Gino Isidori .

The Science of Learning Physics: A greying giant of the field speaks to the A means for t ransfi xed in admirat ion. Cognitive Strategies for blackboard for 45 minutes before turning, lecturers to This is not the teaching style advocated Improving Instruction dismissively seizing paper and scissors, r efle c t on a nd by José Mestre and Jennifer Docktor in and cutting a straight slit. The sheet is their new book The Science of Learning By José P Mestre and enrich their MINISTERIO twisted to represent the conical space– Physics. And it’s no longer typical, say the DE CIENCIA Jennifer L Docktor E INNOVACIÓN time described by the symbols on the teaching authors, who suggest that approximately World Scientific s board. A lecture theatre of students is strategies half of physics lecturers use at least one @CDTIoficial

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OPINION REVIEWS

“evidence-based instructional practice” World Scientific Mestre and Docktor, who are both but does not connect it. Neurons fire, but – jargon, most often, for an interactive educational psychologists with a back- synaptic connections are not trained. teaching method. As colleagues joked ground in physics, offer intriguing tips to And as the list of neurotransmitters that w h e n I q u e s t io n e d t h e m o n t h e i r t e a c h i n g maximise the impact of such practices. reinforce synaptic connections includes s t y l e s, t h e r e i s s t i l l a p e r for m a t i v e a s p e c t A f t e r a n s w e r i n g a s n a p p ol l, t h e y s a y, s t u- dopamine and serotonin, making students to lecturing, but these days it is just as d e nt s s h o u l d d i s c u s s w it h t h e i r n e i g h b o u r feel good by answering questions cor- likely to reflect the rock-star feeling of b e for e b e i n g p ol l e d a g a i n. T h e g o a l i s n o t r e c t l y m a y b e w or t h t h e t i m e i n v e s t m e nt. having a hundred camera phones pointed just to allow the lecturer to tailor their R e l a t i v e t o o t h e r s c i e n c e s, p h y s i c s l e c- at you – albeit so the students can snap teaching, but also to allow students to t u r e r s a r e l e a d i n g t h e w a y i n i m pl e m e nt i n g a QR c o d e o n y o u r s l id e t o t a k e p a r t i n a n “c o n s t r u c t” t h e i r k n o w l e d g e. L e c t u r i n g, evidence-based instructional practices, interactive mid-lecture quiz. they say, gives piecemeal information, b ut f a r t o o fe w a r e w e l l t r a i n e d, s a y M e s- tre and Docktor, who want to bring the tools and educational philosophies of the h i g h-s c h o ol p h y s i c s t e a c h e r t o t h e l e c t u r e theatre. Swiss and Soviet developmental p s y c h ol o g i s t s Je a n P i a g e t a n d L e v V y g o t- s k y a r e d u l y n a m e c h e c k e d. “T h i n k–p a i r– s h a r e”, m i n i w h it e b o a rd s a n d fl i p pi n g t h e c l a s s r o o m (n o t a d i s c o u r t e o u s g e s t u r e b ut t h e a d v a n c e v ie w i n g o f pr e-r e c ord e d l e c- tures before a more participatory lecture), are the order of the day. Students are not blank slates, they write, but have strong attachments to deeply ingrained and o f t e n e r r o n e o u s i nt u it io n s t h a t t h e y h a v e previously constructed. Misconceptions c a n n o t b e s u p pl a nt e d w h ol e s a l e, b ut m u s t be unknotted strand by strand. Lectur- ers should therefore explicitly describe their thought processes and encourage students to reflect on “metacognition”, or “t h i n k i n g a b o ut t h i n k i n g”. He r e t h e t e x t is reminiscent of Nobelist Daniel Kahne- man’s seminal text Thinking, Fast and Slow, which divides thinking into two types: “s y s t e m 1”, w h ic h i s i n s t i n c t i v e a n d e m o- tional, and “system 2”, which is logical but effortful. Lecturers must fight against “knee-jerk” reasoning, say Mestre and D o c k t or, b y m o d e l l i n g t h e t i m e-i nt e n s i v e Hadron colliders and Luvata, construction of knowledge, rather than a s pi r i n g to m i sle a d i n g v i r t uo s o d i s pl a y s o f m a t h e m a t ic a l pr o w e s s. W h e r e v e r p o s- relationships that go back 50 years. sible, this should be directly assessed by giving marks not just for correct answers, Luvata is a combination of metallurgical expertise, Whether you are looking for high-purity oxygen-free b ut a l s o for id e nt i f y i n g t h e “bi g id e a” a n d application know-how and close customer copper or alternative alloys that offer higher show ing your work ing. relationships coming together to make the most strength, Luvata makes the unique shape and D i s a p p oi nt i n g l y, e x a m pl e s a r e l i m it e d of metal. For nearly sixty years, Luvata has been size you are looking for. to pulleys and ramps, and, somewhat ironically, the book’s dusty academic manufacturing copper hollow conductors for the tone may prove ineffective at teaching most demanding applications. Luvata joins in celebrating 50 years of hadron teachers to teach. But no other book colliders and we look forward to the science and comes close to The Science of Learning discovery of the next five decades. Physics a s a m e a n s for l e c t u r e r s t o r e fle c t on a n d e n r ic h t he i r t e a c h i n g s t r at e g ie s, and it is highly recommend on that basis. That said, my respect for my old general-relativity lecturer remained www.luvata.com/cern-courier-nov2020 undimmed as I finished the last page. Those old-fashioned lectures were hugely inspiring – a “non-cognitive aspect” that Mestre and Docktor admit their book does not consider. luvata.com Mark Rayner associate editor.

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While CERN holds a natural CERN attraction for physicists, hiring the engineers, technicians and others who build, operate and maintain the lab’s complex infrastructure is more challenging, explains A n n a Co ok.

CERN enjoys a world-class reputation as a sci- e nt i fic l a b or a t or y, w it h t h e s t a r t-u p o f t h e L arge Hadron Collider and the discovery of the Higgs b o s o n pr o p e l l i n g t h e or g a n i s a t i o n i nt o t h e p u bl i c spotlight. Less tangible and understood by the public, however, is that to achieve this level of success in cutting-edge research, you need the infrastructure and tools to perform it. CERN is an incredible hub for engineering and technology – hosting a vast complex of accelerators, detec- tors, experiments and computing infrastruc- ture. Thus, CERN needs to attract candidates Engineering prowess Natalia Magdalena Koziol, an engineer from , is responsible for from across a wide spectrum of engineering quality assurance of the LHC’s insulation vacuum during Long Shutdown 2. a n d t e c h n i c a l d i s c i pl i n e s t o f u l fi l it s o bj e c t i v es. CERN employs around 2600 staff members I get to challenge myself targeting of, for example, a mechanical tech- who design, build, operate, maintain and sup- n i c i a n i n a l l C E R N M e m b e r St a t e s, c r e a t i v e a n d port an infrastructure used by a much larger in areas and with innovative approaches have to be utilised. The worldwide community of physicists. Of these, varying landscapes, cultural preferences and o n l y 3% a r e r e s e a r c h p h y s i c i s t s. T h e c or e h i r i n g technology you don’t languages come into play, and this is com- needs are for engineers, technicians and support pounded by the different job-seeking behav- s t a ff i n a w i d e v a r i e t y o f d o m a i n s: m e c h anicl, see any other place in iours of students, graduates and experienced electrical, engineering, vacuum, cryogenics, professionals through a constantly evolving c iv i l eng i neer i ng, r ad iat ion protec t ion, r ad io- the world ecosystem of channels and solutions. A wide- frequency, computing, software, hardware, s pr e a d pr e s e n c e i s k e y. T h e c or n e r s t o n e s a r e: a n data acquisition, materials science, health and attractive careers website; professional networks s a fe t y… t h e l i s t g o e s o n. F u r t h e r m or e, t h e r e a r e developed in 2010 to promote its opportunities such as LinkedIn to promote CERN’s employ- also competences needed in human resources, i n a n i n c r e a s i n g l y d i g it a l i s e d e n v i r o n m e nt. T h e ment opportunities and proactively search for legal , communications, knowledge brand centres around factors that make working c a n d i d a t e s; s o c i a l m e d i a t o i n c r e a s e v i s i bi l it y o f t r a n s fe r, fi n a n c e, fi r e fi g ht e r s, m e d ic a l pr ofes- at CERN the rich experience that it is, namely h i r i n g c a m p a i g n s; a n d b e i n g pr e s e nt o n v a r i o u s Gain unique insights on the latest research sionals and other support functions. challenge, purpose, imagination, collaboration, j o b p or t a l s, for e x a m pl e i n t h e oi l, g a s a n d e n e r g y i nt e g r it y a n d q u a l it y o f l i fe – u n d e r pi n n e d b y t h e arenas. Outreach events, presence at university breakthroughs and project developments in On the radar s l o g a n “T a k e p a r t”. T h i s s e r v e s a s a n i d e nt it y t o career fairs and online webinars further serve CERN’s hiring challenge takes on even greater devise attractive campaigns through web con- to present CERN and its diverse opportunities particle physics and related fields m e a n i n g w h e n o n e c o n s i d e r s t h e d r i v e t o a t t r a c t t e nt, v id e o, o n l i n e, s o c i a l m e d i a a n d j o b -p or t a l to the targeted audiences. students, graduates and professionals from a d v e r t i s e m e nt s t o pr o m o t e C E R N a s a n e m pl o y e r Storytelling is an essential ingredient in across CERN’s 32 Member and Associate Member o f c h oic e t o t h e a u d ie n c e s w e s e e k t o r e a c h: f r o m pr o m o t i n g o u r o p p or t u n it i e s, a s a r e t h e e x p e- States. In what is already a competitive mar- students to professionals, apprenticeships to riences of those already working at CERN. In the cerncourier.com k e t, a t t r a c t i n g p e o pl e f r o m a l a r g e m u l t it u d e o f P h D s, a c r o s s a l l d i v e r s it y d i m e n s i o n s. T h e i nt e n- words of Håvard, an electromechanical tech- disciplines to an organisation whose reputation t i o n i s t o p ut C E R N “o n t h e r a d a r” o f p e o pl e w h o n ic i a n f r o m Nor w a y: “I g e t t o c h a l l e n g e m y s e l f r e v ol v e s a r o u n d p a r t ic l e p h y s ic s c a n b e a c h a l- wouldn’t normally identify CERN as a possibility i n a r e a s a n d w it h t e c h n ol o g y y o u d o n’t s e e a n y lenge. So how is this challenge tackled? CERN in t heir c hosen career pat h. other place in the world.” Gunnar, a firefighter now has a well-established “employer brand”, As no single channel exists that will allow from Germany describes, “I am working as a

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PEOPLE CAREERS

fi r e fi g ht e r i n o n e o f t h e m o s t i nt e r n a t i o nalfire engineering fellow from , summed it technical or doctoral student, as a graduate or brigades at CERN in what is a very complex, up with, “Here I am, living my dreams, being a professional, builds skills and knowledge that challenging and interesting environment.” part of an organisation that’s helping me grow are highly transferable in today’s demanding Katarina, a computing engineer from Sweden, every single day.” Each individual experience is a n d c o m p e t it i v e j o b m a r k e t, a l o n g w it h l a s t i n g says, “The diversity of skills needed at CERN is a rich insight for potential candidates to identify connections. As the cherry on the cake, a job at so much larger than what most people know!” with and recognise the possibility of joining CERN paves the way to become CERN’s future While Julia, a former mechanical engineering CERN in their own right. a lu m n i a n d j oi n t h e e v e r-g r o w i n g H i g h-E n e r g y technical student from the UK put it simply: CERN doesn’t just bring together people Network. Take part! “I never knew that CERN recruited students from a large scope of fields but unites people for internships.” Natasha, a former software from all over the world. Working as summer, Anna Cook CERN HR department.

Appointments and awards ThinkEdu Conclave ThinkEdu ESA announces new DG in 1996 as a researcher, was high-energy cosmic rays. The The European Space Agency previously vice-director at JINR Prize is awarded for (ESA) Council has appointed Josef and served as Russia’s deputy a significant contribution Aschbacher as its next director minister of education and science to high-energy astrophysics, general for a period of four years. from 2017–2020. He replaces with a particular emphasis on He will succeed Jan Wörner from Victor Matveev, who was JINR recent work. 30 June. Aschbacher is currently director since 2012. With a term ESA time of five years, Trubnikov 2020 Pomeranchuk Prize will oversee an important period Theorists (CERN) at JINR, with the scheduled and Mikhail Vasiliev (Lebedev completion of the NICA complex Institute) were awarded the 2020 in 2022 (see p9). France. Godbole was recognised Pomeranchuk Prize, which has for her contributions towards been granted annually since 1998

SCIPP’s new skipper collaborations between France S Ferrara Jason Nielsen of the University and India and for her role in of California at Santa Cruz has promoting women’s visibility taken over as director of the Santa in science. Godbole’s decades Cruz Institute for Particle Physics of work in particle physics has ESA director of Earth observation (SCIPP), succeeding Steven Ritz ranged from supersymmetry programmes and head of ESA’s who steps down after 10 years at to electroweak theory, and she centre for Earth observation near the helm. Nielsen, who has served is currently a member of the

Rome. Born in , he studied G Fisher international detector advisory at the University of Innsbruck, group for the International M Vasiliev M where he obtained Masters Linear Collider. and PhD degrees in natural sciences. He has more than three IceCube awarded Rossi Prize decades of experience working The 2021 Bruno Rossi Prize in international organisations, was awarded to including ESA, the European (below) and the IceCube Commission, the Austrian Space Collaboration for the discovery Agency and the Asian Institute of a high-energy neutrino flux of Technology. of astrophysical origin. Halzen as associate director of SCIPP for is principal investigator and JINR director change the past eight years, started out co-spokesperson of the IceCube Grigory Trubnikov has been on the ALEPH experiment at LEP project based at the South Pole, by the Institute for Theoretical

appointed as the new director and is a long-standing member Richter/UW-Madison B and in of the Joint Institute for Nuclear of the ATLAS collaboration, for Moscow. Ferrara (top), who Research (JINR) in Dubna, Russia. which he currently serves on the co-discovered supergravity in Trubnikov, who first joined JINR management advisory committee 1976 along with Daniel Freedman

S Krasilnikov/TASS for the US ATLAS organisation. and , was cited “for his contribution France recognises Godbole to fundamental aspects of Phenomenologist Rohini supersymmetry that has been a Godbole of the Centre for High very important achievement for Energy Physics, Indian Institute our understanding of modern of Science, Bangalore, has supergravity theories”, while been awarded with the Ordre which in September 2017 detected Vasiliev was recognised for an national du Mérite (National a high-energy neutrino from the “outstanding series of papers” on ,, ,.... Order of Merit), one of the direction of a blazar, providing the higher spin theory in Anti-de "' highest distinctions granted by the first evidence of a source of Sitter and de Sitter spaces.

-2 -1 0 1 2 3 Input Power {dBm)

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ELI Beamlines is a part of the ELI (Extreme Light Infrastructure) pan-European laser RECRUITMENT centre representing a unique tool of support of scientific excellence in Europe. ELI Beamlines operates the world’s most intense laser system. With ultra-high power 10 PW and concentrated intensities of up to 1024 W/square cm, we offer our users a unique source of radiation and rays of accelerated particles. These beamlines are enable pioneering research not only in physics and material science, For advertising enquiries, contact CERN Courier recruitment/classified, IOP Publishing, Temple Circus, Temple Way, Bristol BS1 6HG, UK. but also in biomedicine and laboratory astrophysics and many other fields. 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. Please contact us for information about rates, colour options, publication dates and deadlines. We have the following positions available: 1. Scientist – High-energy Density Physics The theory/simulation group RP6 is expanding and recruiting a theoretician in the field of ultra-high intensity laser-plasma interaction. In our team we therefore have this position available. The position could also be on the junior level depending on the qualification and past experience of the candidates. For more details please visit https://brightrecruits.com/physicsworld-jobs/job/senior-researcher-on-theory- and-simulation-of-high-intensity-laser-matter-interaction/ 2. Senior Researcher An open position in the Department of Plasma Physics and Ultra-High Intensity Interaction. For more details please visit JOIN US! https://brightrecruits.com/physicsworld-jobs/job/senior-researcher-iv-81/ The future is in laser technologies The Institute of Physics of the Czech Academy of Sciences is a holder of the HR Excellence in Research Award. It is awarded by the to institutions which put significant effort into improving their human resources strategy and ensuring professional and ethical working conditions.

DATA SCIENTIST / SOFTWARE DEVELOPER EXCITING CAREERS FOR STEM GRADUATES AND POSTGRADUATES

Tessella is one of the world’s leading data science and AI consultancies. We are scientists and engineers who enjoy solving the real-world technical challenges faced by companies at the forefront of science and Purpose. Challenge. Imagination. technology. Using a combination of deep domain knowledge and technical expertise, we work with our clients to unlock the value held within their data, enabling better-informed business decisions. Integrity. Collaboration. Quality of life: Our projects are varied and typically at the cutting-edge of high-tech R&D, for example: » Solving computational problems for chemists in drug discovery and development. » Modelling and simulating new products for FMCG clients and analysing data to improve processes. » Writing algorithms and solving complex mathematical problems to control satellites and radar systems. just a few of the reasons why working for CERN is such a rich experience. » Solving the computational challenges of oil and gas exploration and production, from reservoir modelling to writing control systems.

We are looking for science, mathematics and engineering graduates and postgraduates to join us. Could you be next to join this unique Organization? Supported by our extensive training package, you will apply your deep domain knowledge and use a range of skills to create and develop innovative solutions that truly make a difference in the world. Find out more about our student, graduate and professional opportunities in a wide variety of disciplines on https://careers.cern. careers.tessella.com | [email protected]

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Research Associate

For our location in Hamburg we are seeking: For our location in Hamburg we are seeking: For our location in Zeuthen we are seeking: The Facility for Rare Isotope Beams (FRIB) at Michigan State DESY-Fellowships – experimental The Director of Research for Postdoc for the Photo Injector Test University is approaching completion and commencement Particle Physics Facility PITZ in Zeuthen of user operation in early 2022. The FRIB high-power particle physics superconducting linear accelerator has already been demonstrated to accelerate ion beams to the design energy DESY DESY DESY∙ ∙ ∙ of 200 MeV/u to produce rare isotopes. FRIB is poised to be DESY, with its 2700 employees at its two locations in Hamburg and Zeuthen, DESY, with its 2700 employees at its two locations in Hamburg and Zeuthen, DESY, with its 2700 employees at its two locations in Hamburg and Zeuthen, the world’s most powerful rare isotope beam facility, with is one of the world‘s leading research centres. Its research focuses on is one of the world‘s leading research centres. Its research focuses on is one of the world‘s leading research centres. Its research focuses on unprecedented opportunities to study the vast unexplored decoding the structure and function of matter, from the smallest particles decoding the structure and function of matter, from the smallest particles potential of more than 1,000 new rare isotopes never before decoding the structure and function of matter, from the smallest particles of the universe to the building blocks of life. In this way, DESY contributes of the universe to the building blocks of life. In this way, DESY contributes of the universe to the building blocks of life. In this way, DESY contributes to solving the major questions and urgent challenges facing science, society to solving the major questions and urgent challenges facing science, society produced on Earth. FRIB includes a target facility for the in- to solving the major questions and urgent challenges facing science, society and industry. With its ultramodern research infrastructure, its interdisciplinary and industry. With its ultramodern research infrastructure, its interdisciplinary flight production of rare isotopes. An Advanced Rare Isotope and industry. With its ultramodern research infrastructure, its interdisciplinary research platforms and its international networks, DESY offers a highly research platforms and its international networks, DESY offers a highly Separator (ARIS) will prepare fast rare isotope beams with high- research platforms and its international networks, DESY offers a highly attractive working environment in the fields of science, technology and attractive working environment in the fields of science, technology and purity for nuclear physics experiments. attractive working environment in the fields of science, technology and administration as well as for the education of highly qualified young administration as well as for the education of highly qualified youngscientists. administration as well as for the education of highly qualified young scientists. The Photo Injector Test Facility PITZ in Zeuthen (near Berlin) is one of the We invite Ph.D. graduates to apply for this Research Associate scientists. The activities of DESY in particle physics comprise a vibrant experi mental leading international groups in developments on modern photo injectors position and join the FRIB Accelerator Physics Department. programme including participation in the ATLAS and CMS experiments and their applications. Current R&D goals of PITZ include improving The Research Associate will contribute to the commissioning, We participate in leading roles in particle physics projects on our campus at the Large Hadron Collider, the Belle II experiment at SuperKEKB, local electron source brightness beyond state of the art and demonstration development, and operation of the FRIB by undertaking projects and in international laboratories such as CERN or KEK. We develop experimental activities in dark matter searches, and a strong involvement of accelerator-based THz pump sources for high repetition rate X-ray technologies for detectors and accelerators, and work on scientific in developments of detector technologies for future projects in particle Free-Electron Lasers (FELs) like FLASH and European XFEL. Such efforts and activities to improve facility performance as measured by computing. We operate important infrastructures such as the Tier-2 centre physics. DESY hosts a world leading group in theoretical particle physics require reliable and comprehensive electron beam characterization, i.e. a beam quality, intensity, power, purity, and variety. or the electron test beam. focused on phenomenology, lattice gauge theory, string theory, and detailed reconstruction for both projected and time-resolved phase space cosmology. DESY also operates one of the largest computing centres measurements. The focus of the offered position will be on further develop- Position duties can be adjusted according to the candidate’s The position for particle physics, astroparticle physics, and photon science. DESY is ments of tools for the characterization of high brightness electron beams experience, interests, and talents. currently engaged in an international search process for the Director of and/or start-to-end beam dynamics simulations for e.g. commissioning the You are invited to take an active role in one or more of the following Research for Particle Physics. new THz SASE FEL beamline. For more details and how to apply, please visit: projects in Hamburg: https://brightrecruits.com/physicsworld-jobs/job/research- • The ATLAS and CMS experiments at CERN or the Belle II experiment The position The position associate/ at KEK The Director of Research for Particle Physics • Develop, test and support software packages for low-emittance electron • Experimental activities on-site (ALPS II and future on-site experiments) • is head of the particle physics division and as member of the board of beam characterization and THz SASE FEL commissioning • Preparations for future particle physics experiments, in particular detector directors responsible for the development of the lab as whole • Perform accurate modeling of experimental procedures for electron beam and technology development • plays a leading role in shaping the future of particle physics at DESY measurements including classification and analysis of systematic errors • Scientific computing including the cooperation with other research areas • Carry out start-to-end simulations of the beam dynamics in the photo • Accelerator development • is responsible for representing the field of particle physics in the injector for operation conditions as well as for future applications Helmholtz Association and for coordinating DESY‘s contribution to • Analyze experimental data and compare with start-to-end simulation results international projects in particle physics as well as representing DESY in • Participate in shift operation for accelerator R&D at PITZ and/or European Requirements international networks and/or organisations XFEL • Ph.D. in physics (to be eligible, you have to take up the position at the • is expected to take over responsibility for infrastructure service groups latest 5 years after your doctorate) Requirements • Interest in particle physics Requirements • University degree in accelerator physics with PhD, with very good Discover what’s out there • Expertise relevant in at least one of the areas listed above • Outstanding research record, international stature, and a broad knowledge in accelerator physics and accelerator technology or spectrum of interest in particle physics as well as in accelerator- based equivalent qualification DESY-Fellowships are awarded for a duration of 2 years with the possibility science • Strong background in beam dynamics simulations of space charge Take the next step in your career of prolongation by one additional year. • Long-standing experience in providing leadership of people and larger dominated beams as well as in numerical and statistical methods scientific groups • Good knowledge in experimental characterization of particle beams with Physics World Jobs. Further information and a link to the submission system for your application • Proven scientific leadership and excellent managing skills using image processing; good programming skills and knowledge of and the references can be found here: http://www.desy.de/FellowFH • Sound knowledge of the international research landscape high-level scripting languages (Python/Matlab) • Very good command of English is required and knowledge of German is Please note that it is the applicant‘s responsibility that all material, including For further information please contact Dr. Rafael Abela (Chairman of the physicsworld.com/jobs of advantage 3 letters of reference, reach DESY before the deadline. Search Committee) email: [email protected] • Excellent teamwork abilities in an international environment The appointment is for a period of maximum five years. Reappointment is Salary and benefits are commensurate with those of public service possible. The position is compensated at an international level in accordance For further information please contact Dr. Mikhail Krasilnikov at organisations in Germany. Classification is based upon qualifications and with the W3 salary system in Germany which includes the option of +49 33762 7-7213 ([email protected]). assigned duties. Handicapped persons will be given preference to other performance-related payments. The position is limited to 2 years at the beginning. equally qualified applicants. DESY operates flexible work schemes. DESY operates flexible work schemes. DESY‘s goal is to promote more Salary and benefits are commensurate with those of public service organi- DESY is an equal opportunity, affirmative action employer andencourages women into leadership positions. Applications from women will therefore sations in Germany. Classification is based upon qualifications and assigned applications from women. Vacant positions at DESY are in general open be explicitly welcomed. Persons with disabilities will be given preference to duties. Persons with disabilities will be given preference to other equally quali fied to part-time work. During each application procedure DESY will assess other equally qualified applicants. applicants. DESY operates flexible work schemes. DESY is an equal oppor- whether the post can be filled with part-timeemployees. Please note the data protection instruction under the link tunity, affirmative action employer and encourages applications from women. We are looking forward to your application via our application system: www.desy.de/data_privacy_policy/index_eng.. We are looking forward to your application via our application system: www.desy.de/onlineapplication We are looking forward to your application via our application system: www.desy.de/onlineapplication www.desy.de/onlineapplication Deutsches Elektronen-Synchrotron DESY Deutsches Elektronen-Synchrotron DESY Deutsches Elektronen-Synchrotron DESY Human Resources Department | Code: APPO001/2021 Human Resources Department | Code: FHFE001/2021 Particle Physics Search Committee Notkestraße 85 | 22607 Hamburg Germany Notkestraße 85 | 22607 Hamburg Germany c/o Human Resources Department | Code: FHDIR/2021 Phone: +49 40 8998-3392 Phone: +49 40 8998-3392 Notkestraße 85 | 22607 Hamburg Germany | Phone: +49 40 8998-3392 www.desy.de/career Deadline for applications: 2021/03/31 www.desy.de/career Deadline for applications: 2021/03/22 www.desy.de/career Deadline for applications: 2021/03/10

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Meet cancer’s PEOPLE biggest threat: OBITUARIES

Precision Jack Steinberger 1921–2020 Radiation A giant of t he field e e /E N t/CER net Ben E S Jack Steinberger, a giant of the field who wit- nessed and shaped the evolution of particle Medicine. physics from its beginnings to the confirma- tion of the Standard Model, passed away on 12 December aged 99. Born in the Bavarian town of Bad Kissingen in 1921, his father was a c a nt or a n d r e l i g io u s t e a c h e r t o t h e s m a l l Je w i s h community, and his mother gave English and F r e n c h l e s s o n s t o s u p pl e m e nt t h e f a m i l y i n c o m e. I n 193 4, a f t e r n e w Na z i l a w s h a d e x c lu d e d Je w i s h children from higher education, Jack’s parents a p pl i e d for h i m a n d h i s br o t h e r t o t a k e p a r t i n a c h a r it a bl e s c h e m e t h a t s a w 300 G e r m a n r e f u g e e children transferred to the US. Jack found his home as a foster child, and was reunited with his parents and younger brot her in 1938. Jack studied chemistry at the until 1942, when he joined the army and was sent to the MIT radiation laboratory t o w or k o n r a d a r b o m b s i g ht s. He w a s a s s i g n e d to the antenna group where his attention was brought to physics. After the war he returned to Chicago to embark on a career in theoretical physics. Under the guidance of , Jack photographed at CERN in 2016. howe ver, he s w itc he d to t he e x p er i me nt a l side of the field, conducting mountaintop investi- should be adopted across the whole detector gations into cosmic rays. He was awarded a PhD A curious and as far as possible. This led to the end-caps in 1948. Fermi, who was probably Jack’s most reflecting the design of the central detector, influential physics teacher, described him as imaginative for example. Jack was also insistent that all “direct, confident, without complication, he technologies considered for the detector first c o n c e nt r a t e d o n p h y s i c s, a n d t h a t w a s e n o u g h”. physicist with an had to be completely understood. As the LEP I n 1949 St e i n b e r g e r w e nt t o t h e R a d i a t i o n L a b era got underway, this level of discipline was a t t h e Un i v e r s it y o f C a l i for n i a a t B e r k e l e y, w h e r e extraordinary rigour reflected in ALEPH’s results. he performed an experiment at the electron syn- Next to physics, music formed an important chrotron that demonstrated the production of S y n c h r o t r o n, Ja c k b e c a m e a fo u n d i n g m e m b e r o f part of Jack’s life. He organised gatherings of n e ut r a l pi o n s a n d t h e i r d e c a y t o p h o t o n p a i r s. He the CERN–Dortmund–Heidelberg–Saclay (CDHS) amateur, and occasionally professional, musi- s t a y e d o n l y o n e y e a r i n B e r k e l e y, p a r t l y b e c a u s e c ol l a b or a t i o n. R u n n i n g f r o m 1976 t o 1984, C DHS cians at his house. These were usually marathons he declined to sign the anti-communist loyalty produced a string of important results using neu- of Bach, starting in the late afternoon and contin- oat h, and moved on to Columbia Universit y. trino beams to probe the structure of the nucleon u i n g u nt i l t h e l a t e e v e n i n g. I n h i s a ut o bi o g r a p h y, In the 1960s the construction of a high- and the Standard Model in general. In particular, Jack summarised: “I play the flute, unfortunately energy, high-flux proton accelerator at t he col l ab or at ion con fi r me d t he pre d ic te d v a r- not very well, and have enjoyed tennis, moun- Brookhaven opened the door to the study of iation of the structure function of the valence taineering and sailing, passionately.” w e a k i nt e r a c t i o n s u s i n g n e ut r i n o -b e a m e x p e r- q u a r k s w it h Q 2 (n i c k n a m e d “s c a l i n g v i ol a t i o n s”), Ja c k r e t i r e d f r o m C E R N i n 1986 a n d w e nt o n t o iments. This marked the beginning of Jack’s a milestone in t he establishment of QCD. become a professor at the Scuola Normale Supe- Elekta is committed to ensuring everyone interest in neutrino physics. Along with Mel When the Large Electron–Positron (LEP) r i or e d i P i s a. P r e s i d e nt R o n a l d R e a g a n a w a r d e d Schwarz and Leon Lederman, he designed and collider was first proposed, a core group from him the National Medal of Science in 1988. In in the world with cancer has access to—and built the experiment that established the differ- C DHS j oi n e d p h y s i c i s t s f r o m o t h e r i n s t it ut i o n s 2001, on the occasion of his 80th birthday, the ence between neutrinos associated with muons to develop a detector for CERN’s new flagship city of Bad Kissingen named its gymnasium in benefits from—more precise, personalized and those associated with electrons, for which collider. This initiative grew into the ALEPH his honour. Jack continued his association with radiotherapy treatments. t hey received t he 1988 Nobel Pri ze in Physics. e x p e r i m e nt, a n d Ja c k, a c u r i o u s a n d i m a g i n a t i v e CERN throughout his 90s. He leaves his mark Jac k joi ne d CER N i n 1968, work i ng on e x p er- p h y s i c i s t w it h a n e x t r a or d i n a r y r i g o u r, w a s t h e not ju s t on p a r t ic le p hy sic s but on a l l of u s w ho i me nt s at t he P rot on S y nc h rot ron e x plor i n g CP n a t u r a l c h oi c e t o b e c o m e it s fi r s t s p o k e s p e r s o n had the opportunity to collaborate with him. Focus where it matters. violation in neutral . In the 1970s, with the in 1980, a position he held until 1990. From the elekta.com/PRM a d v e nt o f n e w n e ut r i n o b e a m s a t t h e S u p e r P r o t o n outset, he stipulated that standard solutions His friends and colleagues.

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PEOPLE OBITUARIES PEOPLE OBITUARIES

M artinus J G VeltM an 1931–2021 Günther Plass 1930–2020 A lasting impact Decisive contributions to CERN

Eminent physicist and Nobel laureate Martinus CERN Günther Plass, a former CERN director of accel- modifications, is now a key component of the Veltman passed away in his home town of erators who made decisive contributions to the LHC ion programme as the Low-Energy Ion Ring Bilthoven, the , on 4 January. development and successful operation of many of (LEIR). He displayed the full measure of his talent Martinus (Tini) Veltman graduated in physics at CERN’s large facilities, passed away on 11 Decem- as leader and conductor of a large orchestra as Utrecht University, opting first for experimental ber, aged 90. After graduating from the Technical deputy to , the LEP project leader, physics but later switching to theory. After his University Berlin–Charlottenburg, and a short from 1981 onwards and from 1983 as LEP division conscript military service in 1959, Léon Van Hove detour via an industrial magnet laboratory in leader. His contributions range from optimising CERN-HOMEWEB-PHO-2021-006-1 offered him a position as a PhD student. Veltman Germany, Günther joined CERN in 1956, partic- the siting of the 27 km-long tunnel within the started in Utrecht, but later followed Van Hove ipating in the construction of the Proton Syn- geological and environmental constraints of to the CERN theory division. chrotron (PS) as a member of the magnet group. the region, planning during construction and CERN opened up a new world, and Tini often Over the years, he made major contributions to integrating frequent last-minute demands by mentioned how he benefited from contacts the continuous upgrade of the PS complex, the the experimenters, to handling arbitrations with with John Bell, Gilberto Bernardini and Sam heart of CERN’s accelerator chain to this day. difficult contractors. As director of accelerators Berman. The latter got him interested in weak With Berend Kuiper, he led the development of from 1990, he lent full support to the upgrade of interactions and in particular neutrino phys- the machine’s novel fast-ejection system, which Günther was instrumental in the development and LEP by means of superconducting cavities, which ics. During his time there, Tini spent a short enabled the first satisfactory neutrino beam operation of many of CERN’s large facilities. extended its energy reach from the Z° to the W+W– period at SLAC where he started to work on his benefitting from the magnetic horns invented threshold and above, and he strongly encouraged computer algebra program “Schoonschip”. He by Simon van der Meer. Günther was then his mark as a member of the SPS design com- the studies that would ensure the future of CERN, correctly foresaw that practical calculations of responsible for the infrastructure for Gargamelle, mittee as the author, together with Colin Ramm such as those for the LHC and CLIC. Feynman diagrams would become more and the bubble chamber where neutral currents were as early as 1961, of a suggestion to construct the Günther’s success was due to his unassuming more complicated, particularly for theories with later discovered. As leader of the Synchrotron SPS near the site, well before the final character, his patience and ability to listen, his v e c t or b o s o n s. No w a d a y s e x t e n d e d c a lc u l a t i o n s Ring group, he shaped the massive PS improve- decision was taken in 1970. open and calm mind in the face of adversity, and beyond one loop are unthinkable without com- ment programme launched in 1965. Once the antiproton–proton programme was his ability to identify the essential points and puter algebra. Later, in 1978, he oversaw the construction successfully under way, a strong interest in the the right people for a task or project. In 1964 Murray Gell-Mann proposed an alge- of the new Linac2, which faithfully delivered use of low-energy antiprotons developed. In bra of conserved current operators for hadronic protons to all CERN’s facilities for 40 years until 1980 Günther was among those proposing the Kurt Hübner and Carlo Wyss matter, which included the weak and electro- it gave way to Linac4 in 2018. Günther also left Low-Energy Antiproton Ring (LEAR), which, after formerly of CERN (now retired). magnetic currents. He argued that commutators Martinus Veltman (right) with John Bell at CERN in 1973. of two currents taken at the same instant in a ndré M artin 1929–2020 Martin Family time should “close”, meaning that these com- Veltman made a lasting the mass of the top quark, which was not yet other similar systems, in particular in atomic mutators can be written as linear combinations discovered. Later, when CERN was planning to An ambassador physics. André also liked lighter topics, such of the same set of currents. From this relation impact on particle build the LEP collider, the emphasis changed as the stability of four-legged tables on uneven one could derive so-called sum rules that can be to the calculation of one-loop corrections for ground, inspired by experiments on the CERN c o m p a r e d t o e x p e r i m e nt s. Fa c i n g t h e t e c h n i c a l physics, and inspired various processes in e+e– collisions. As a member for CERN cafeteria terrace, a study widely shared on the problems with this approach, Tini came up with of t he CER N S c ie nt i fic Pol ic y C om m it te e (SP C), Web in the early . an alternative proposal. In a 1966 paper he sim- many students Veltman strongly argued that LEP should operate André Martin passed away on 11 November 2020, Among his distinctions, he was admitted to ply conjectured that the hadronic currents for at the highest possible energy, well above the marking a great loss to the theory community the French Académie des Sciences in 1990, and the electromagnetic and weak interactions had W+W– threshold, to study the electroweak theory worldwide and to the CERN family. André was he was awarded the Légion d’honneur in 1992, to be covariantly conserved, where he assumed theories. Veltman, who was already well aware of with precision. The Standard Model has since born in Paris on 20 September 1929 and stud- the Gian-Carlo Wick Medal in 2007 and the that the weak interactions were mediated by many of the pitfalls, only gradually agreed, and passed all of these tests. ied at the École Normale Supérieure (ENS) and Pomeranchuk Prize in 2010. He met his wife, virtual vector bosons, just as electromagnetic so Gerard ’t Hooft joined the programme. This From his early days at CERN it was clear that the University of Paris. His thesis adviser was Alice-Anne Schubert (“Schu”), who passed away processes are mediated by virtual photons. turned out to be a very fruitful endeavour and Tini had a strong interest in confronting theo- Maurice Lévy (ENS theory group), with whom he in 2016, at CERN thanks to his dear friend Julius The current conservation laws therefore had the work was proudly presented in the summer of retical predictions with experimental results, had a lifelong friendship and many common pro- André Martin joined CERN in 1959. Wess. They were a wonderful power couple, with t o c o nt a i n e x t r a t e r m s d e p e n d i n g o n t h e p h o t o n 1971. Veltman and ’t Hooft continued to collabo- and in the organisation needed to do so. To this jects. André arrived at CERN in 1959 as a fellow, an intense cultural and social life. Their hospi- field and the fields associated with the weak rate on Yang–Mills theory. Their 1972 papers are end, he was one of a small group of colleagues b e c a m e a s t a ff m e m b e r i n 1964 a n d a n h o n or ary often came back to problems when he had tality was extraordinary, and it was a pleasure intermediate vector bosons. Quite surpris- among the finest that have been written on the in the Netherlands to push for a national insti- member in 1994. He was still working until a already obtained striking results but was not to enjoy their immense culture in literature ingly, he could then demonstrate that these subject. In 1999 they shared the Nobel Prize in tute for subatomic physics – Nikhef, which few days before he was admitted to hospital, fully satisfied. Among the many topics of his and art. They are survived by their two sons, new conservation equations suffice to prove Physics “for elucidating the quantum structure was founded in 1975. In 1981 Tini moved to the diagnosed with coronavirus and died of pneu- sc ient ific cont r ibut ions, we ca n h ig h l ig ht t he Thierry and Philippe, and two grandchildren, the same sum rules. A more important aspect of electroweak interactions”. University of Michigan in Ann Arbor, returning monia. He led a cosmopolitan life, travelling all analytic properties of scattering amplitudes, Raoul and Jeanne. of his approach was only gradually realised, With the renormalisability of the electroweak to the Netherlands after his retirement in 1996. over the world, and had friends and colleagues the high-energy behaviour of integrated and André had friends in almost every univer- namely that the conservation laws for these theory established, precision comparisons with Ve l t m a n m a d e a l a s t i n g i m p a c t o n t h e fie l d o f all over. He had long and productive visits to differential cross sections, the inverse prob- sity or institute, whom he met at CERN or con- currents are characteristic of a non-abelian experiment were within reach, and Veltman particle physics, and inspired many students. various US institutions, including Princeton, lem in quantum mechanics, the ambiguities in ferences. He was often the go-between who gauge theory as had been written down more started to work on these problems with postdocs Until recently he followed what was happening Stony Brook, Seattle, Caltech, Los Alamos and phase-shift analyses, the range of annihila- initiated new collaborations. He was deeply than 10 years earlier by Yang and Mills. Hence and PhD students. One important tool was the in the field, regularly attending the September Rockefeller. André was proud to have contrib- tion and two-dimensional quantum mechan- committed to CERN’s mission and was one of Veltman started to work on the possible renor- so-called rho parameter (a ratio of the masses of meetings of the SPC. Our community will miss uted to the launching of the Cargese school and ics. After the discovery of charmonium, he its best ambassadors and advocates. He will be malisability of Yang–Mills theory. t h e W a n d Z b o s o n s a n d t h e w e a k m i x i n g a n g l e). his sharp reasoning and clear-eyed look at par- supported the Erice and Les Houches centres. became interested in the spectral properties sorely missed. Meanwhile, Veltman had left CERN towards Its experimental value was close to one, which ticle physics that are crucial for its development. André worked on rigorous mathemati- of con fi n i ng p ote nt i a l s, a subje c t on w h ic h he the end of 1966 to accept a professorship at showed that only models in which the Higgs field cal physics and the derived phenomenology wrote several important articles and eventu- Luis Álvarez-Gaumé Stony Brook University Utrecht. At the end of 1969 a prospective PhD starts as a doublet are allowed. From the small Karel Gaemers Nikhef/University of Amsterdam applied to the dynamics of strong interac- ally a book. His results and methods applied and Jean-Marc Richard Institut de Physique student insisted on working on Yang–Mills deviations from one, it was possible to estimate and Bernard De Wit Nikhef/Utrecht University. tions, both alone and in collaboration. He to quarkonia and were extended to des 2 Infinis de Lyon.

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PEOPLE OBITUARIES Freiburg of University Stephanie ZimmeR m ann 1973–2020 Stephanie was an outstanding scientist who Open access for CERN researchers received university awards for best Masters Outstanding thesis and again for best doctoral thesis, the latter also awarded the ATLAS Marc Virchaux commitment Prize. She was highly regarded for her detailed Thanks to a transformative agreement between CERN and 50+ journals including: knowledge of every aspect of the project, her IOP Publishing, you can: outstanding commitment and team spirit, as ATLAS physicist Stephanie Zimmermann passed well as her support and care for her collaborators. Publish open access in more than 50 IOP Publishing journals away suddenly on 10 November. She joined the As NSW project manager, she was known and • experiment when she was studying physics respected for her strong will, assertiveness and at no cost to you at the University of Freiburg, and worked on matter-of-factness. While she could be uncom- the muon system as a Masters student from promising when defending the project, she was • Increase your paper’s visibility and impact* 1999. After graduating, she continued her work a tender-hearted person who cared deeply about Comply with any open access mandate and policy, even when in ATLAS during her doctoral thesis, research her team members. Her shining example will • fellowship at CERN and subsequent research Stephanie led the ATLAS New Small Wheel project. encourage us to make her dream come true and publishing in non-SCOAP3 journals career at Freiburg. She held many important to finish and install t he NSW on sc hedule. positions in ATLAS. As a fellow, she coordinated ATLAS underground hall. She was involved in • Be covered whether your affiliation is primary or secondary the integration work of the monitored drift- the muon-detector control system, and served Philipp Fleischmann (for the ATLAS Include articles from CERN experimental collaborations tube chambers and the resistive plate cham- as muon run coordinator, ATLAS run coordi- Muon System), Gregor Herten (for the • bers. It was largely thanks to her that this task nator and, from 2013, led the New Small Wheel Freiburg ATLAS group) and such as ATLAS, CMS, LHCb and ALICE was completed in time for installation in the (NSW) project. (for the ATLAS collaboration).

Stephen ReucRoft 1943–2020 BCTV novel avalanche photodiode sensors), software and computing systems, and physics analyses. Find out more at http://bit.ly/CERNIOP An all-round He actively promoted technology transfer from academia to industry and co-founded a non- experimentalist profit company in Boston that was the first to bring silicon photomultipliers to market. He also initiated a cloud service for the protection Experimental particle physicist Stephen of elderly and fragile people, and launched a Reucroft passed away in October 2020 after a crowd-funding campaign to advance next- long struggle against cancer. generation nuclear energy technologies. Steve grew up in Yorkshire, UK, earning a Steve was a strong advocate for young scien- PhD in particle physics in 1969 from the Uni- tists, advising more than 45 PhD students and versity of Liverpool. His early research career postgraduates, and was very active in scientific focused on precision measurements using the outreach. He co-founded the Research Expe- high-resolution rapid-cycling bubble chambers Reucroft actively promoted technology transfer rience for Undergraduates (REU) programme HYBUC and LEBC at the CERN PS and SPS. These from academia to industry. at CERN, judged the Intel (now Regeneron) included resonance properties, mag- International Science and Engineering Fair, netic moments, and charm-particle production Observatory. He developed novel scintillating and co-wrote a science column for The Boston and decay. He was the CERN-EP group leader fibre detectors that were used successfully in the Globe newspaper. He wrote numerous academic for the North Area experiments NA13, 16 and and proposed for the SSC, and built papers, popular articles and books, was a regu- 27. Subsequently, he was spokesperson of E743, up and led a large research group on the L3 and D0 lar contributor to CERN Courier, and was elected which took LEBC to Fermilab to successfully experiments working on precision electroweak to the National Association of Science Writers. resolve a controversy about the energy depend- and QCD measurements, among many others. An Steve was invariably cheerful with a unique ence of the charm production cross section. early collaborator on the CMS experiment, Steve sense of humour, and his door was always open. Steve became professor of physics at North- led a consortium of eight NSF-supported uni- He will be much missed. eastern University, Boston, in 1986, working at versity groups that made major contributions to the highest energy colliders and the Pierre Auger the electromagnetic calorimeter (especially the Lucas Taylor Fermilab. Family Berset Family Jean-claude BeRSet 1939–2020 Jean-Claude worked on the PS and ISR, SPS, LEP An expert and finally the LHC. he worked on the development of the readout elec- tronics for the ALICE – a engineer system that was in operation until very recently. Jean-Claude retired from CERN in 2005. His SCAN ME TO FIND OUT MORE CERN engineer Jean-Claude Berset passed away colleagues remember him not only as an expert on 1 October at the age of 81. Jean-Claude arrived and competent engineer, highly skilled, analyti- at CERN in 1970 and was assigned as an electronics cal, meticulous and always ready to help, but also technician in the former NP division, developing a colleague and friend whose modesty and fine * H Piwowar, J Priem, L V arivière, J P Alperin, L Matthias, B Norlander, A Farley, J West, S Haustein (2018) The state of OA: a large-scale analysis of the prevalence and impact of Open Access articles. front-end electronics. He participated in the devel- human qualities we will treasure. PeerJ 6:e4375 https://doi.org/10.7717/peerj.4375 opment and construction of systems for various experiments at CERN, from his early days on the PS His colleagues and friends in the a nd ISR, t he n SPS, LEP a nd fi n a l ly t he LHC, w here ALICE collaboration.

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Notes and observations from the high-energy physics community The g reat physics ba ke-off From the archive: April 1981 Antiprotons à gogo Cakes were baked, votes were C Joe counted, and UK student Maddie On 11–14 Febr uar y CERN’s 28 GeV Proton Watkins beat off stiff competition Sy nc hrot ron, PS, became t he world’s from a ba ker’s dozen of high- first antiproton synchrotron. Intense 27.2.81 CERN energy physicists to be crowned pulses of 3.5 GeV antiprotons from the star baker of the inaugural are accelerated #GreatPhysicsBakeOff for her to 26 GeV in t he PS for use in proton– depiction of Archimedes’ eureka antiproton collisions in the Intersecting The TT6 beamline, soon scheduled to transport moment. “We had gravitational- Storage Rings or in the Super Proton 28 GeV antiprotons from the lensing g ateau x, stel lar- Synchrotron, SPS, after subsequent PS to the ISR. nucleosynthesis sponge and acceleration [achieved on 10 July at recreations of the International 540 GeV cent re-of-mass energ y] in t he searc h for t he elusive Wilson Hall in gingerbread, by Fermilab Space Station, the NASA Space inter mediate bosons of wea k inter act ions. At t he ot her end of t he accelerator operator Cindy Joe. Shuttle and Fermilab’s iconic energy scale, preparations are under way in the PS South Hall to Wilson Hall,” says organiser const r uct a Low Energ y A nt iproton R ing, LE A R, prov iding intense Katharine Leney (Southern Methodist University) of the January ant iproton beams in t he energ y r ange 0.1 to 2 GeV. Investigations of competition, which took place on social media. “We’re still wondering proton–antiproton annihilation should improve our knowledge of if you lose weight eating antiparticle cupcakes,” adds co-organiser quark behaviour. LEAR physics will also cover spectroscopy, Steph Hil ls (STFC). exotic proton–antiproton atoms, and could provide a definitive answer on bar yonium, states for med from bar yons and ant ibar yons. The shortest unit of time  Based on te x t from pp104–105 and 113–115 of CERN Courier Apr il 1981. ever measured (1 zs = 10–21s), Compiler’s note corresponding to the Antimatter – like black holes, wormholes and multiverses – feeds our time it takes light to cross deep-seated curiosity for the mysterious. The is supposed to have created particles in pairs, equal and opposite, that recombine on contact, a hydrogen , 247 zs releasing the energy that produced them. So why is there anything other as clocked by physicists at than energy in the universe? For every billion pairs that annihilated, it seems DESY’s PETRA III facility just one partner survived – a sine que non for our existence. To date, (Science 370 339). laboratory efforts to create antimatter have done little to redress the imbalance. By 2015 it was estimated that CERN had created 1 ng of antiprotons, Fermilab an impressive 15 ng, and 2 ng of positrons had been produced at DESY. But the total annihilation energy obtainable using this ATOMKI boson under fire ersatz antimatter is insufficient to boil cup of tea.

Particle physicists in Canada and the US have added a new twist to + – t he tale of t he ATOMKI anomaly – a repor ted 6.8σ e xcess of e e pairs resurfaced after the 94 year-old 8 Media corner created during nuclear transitions of excited Be nuclei to their ground neutrino pioneer’s passing state spotted by a team in in 2015, and for which a new 17 MeV in November (American Institute “At Brookhaven, I was always (“X17”) has been proposed as an explanation (CERN of Physics). Courier January/February 2019 p7). In a preprint posted on 3 February, sitting on the edge of my chair Aleksandrs Aleksejevs (Memorial University of Newfoundland) and [during unblinding], and I think I “I could not be more excited about co-workers pour cold water on this interpretation, arguing that the will be here, too.” the new supercollider!” anomaly can be explained by adding the full set of second-order Experimentalist Lee Roberts of Elon Musk on T w it ter (2 Novemb er) corrections and the interference terms to the Born-level decay Boston University quoted in interacting with Fermilab director amplitudes considered by the ATOMKI team (arXiv:2102.01127). Science (27 Januar y) about t he Nigel Loc k yer on t he subject of a X17’s proponents remain undeter red. “The aut hors appear to let t he hotly anticipated muon g-2 f ut ure c ircular col l ider. si ze of t he higher-order effects be a free par ameter and find t hat by measurement from Fermilab. assuming they are much larger than expected, one could produce a bump “Today, Jane Street’s source code is at 15 MeV, not t he 17 MeV obser ved. So it’s an interest ing step, but t here’s “That statement made me furious, 25M lines long, about half as much st il l more work to be done,” says Jonat han Feng of UC Ir v ine. Meanwhile, so I started studying physics.” as the Large Hadron Collider uses.” spokesperson for t he ATOMKI e x per iment At t ila K r aszna horkay A 1997 quote by t he late Nobel The Financial Times (28 Januar y) protests that the effect has since also been seen in other nuclear species: laureate Masatoshi Koshiba, on c hannels CERN to communicate “Our results for 4He and 12C would not be affected by any inter ference how a professor telling him that the complexity of the algorithms phenomenon, while we see t he X17 anomaly in bot h of t hem, so we he cannot study physics made him used by quantitative trading firm continue our experiments, with new results soon to be published.” take it up in the first place, has Jane St reet.

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