CERN Courier–Digital Edition

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CERN Courier – digital edition

Welcome to the digital edition of the March/April 2021 issue of CERN Courie r. Hadron colliders have contributed to a golden era of discovery in high-energy physics, hosting experiments that have enabled physicists to unearth the cornerstones of the Standard Model. 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 Hadron Collider (p38) – which has spawned thousands

of papers in its ﬁrst 10 years of operations alone (p47). It also bodes well for a

potential future circular collider at CERN operating at a centre-of-mass energy of at least 100TeV, 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” particles 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 target gravitational waves (p10); X-rays go behind the scenes of supernova

1987A (p12); a high-performance computing collaboration forms to handle the

big-physics data onslaught (p22); Steven Weinberg talks about his latest work (p51); and much more.

ery

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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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Volume 61 Number 2 march/april 2021

IN THIS ISSUE

It’s ALL

about the

DETAILS

Dalitzdecay ATLA S s pot s r ar e d eca y o f t h e H igg s b oson

UniversalsearchBaikal-GVD will continue the

StaﬀsearchCERN’s eﬀorts to attract

AEgIS on track to test antimatter free fall
First evidence for rare

Higgs-boson decay

Tooling up to hunt dark

Jack Steinberger

Martinus Veltman Günther Plass

Acceleratingtalent at CERN

The challenge of attracting engineers, technicians

and others who build and

maintain CERN’s complex

infrastructure. 61

•••••••

matter Computing

NICA sees ﬁrst beam

CLOUD and Arctic sea
Supersymmetry

collaboration kicks oﬀ

searches Precision

Quark-matter ﬁreballs

in Protvino. 21

André Martin

Stephanie Zimmermann Stephen Reucroft Jean-Claude Berset. 69

The core of SN1987A. 7

FeaTureS

Insearchof WISPs

New experiments will expand the search for axions and other weakly interacting ‘slim’ particles that could hail from far

above the TeV scale. 25

Discoverymachines

Lyn Evans and Peter Jenni look at the lessons learned from 50 years of experience with hadron colliders and

their detectors. 38

A decadeinLHC publications

Alex Kohls, Jens Vigen and Micha Moskovic

look back on the

Russia’sparticle- physicspowerhouse

The Institute for Nuclear Research in Moscow continues to leave its mark on neutrino and high-energy physics. 33

ﬁrst 10 years of LHC

publications. 47

DeparTmeNTS opiNioN

FROM THE EDITOR

Power Supply Systems

Connectingphysics withsociety

We must communicate the applications and

impact of our ﬁeld, argues Barbora Bruant

Gulejova. 49

Stillseeking solutions

Steven Weinberg reflects on effective field theory

and his latest attempt to understand the fermion

mass hierarchy. 51

Thehitchhiker’s guidetoweakdecays

An expedition to

NEWS DIGEST

Precision Current Measurements Beamline Electronic Instrumentation FMC and MicroTCA

APPOINTMENTS &AWARDS

new physics summits

RECRUITMENT BACKGROUND

64 74

Onthecover: CERN’s

Intersectin g S torag e R ings,

the ﬁrs t h adron collider. 38

The science of

learning physics. 57

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ack in the early 1960s, as this month’s cover feature Europeanstrategyforparticlephysics, CERNisexploringthe describes (p38), discussion raged at CERN about the mostambitiouslong-termtechnologicalpathinundertaking nextbeststepforparticlephysics.Atthetime,thehigh- a feasibility study for a future circular hadron collider with a energyfrontierwascommandedbythegreatprotonsynchro- centre-of-massenergyofatleast100TeV. Ifbuilt, thesuccess trons, such as Brookhaven’s Cosmotron and, later, CERN’s ofthismotherofallhadroncolliderswillhaveeachgeneration

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Matthew Chalmers

Editor

of proton beams for the production of new particles – the Know your limits hadron collider – was revving up in the sidelines. In Decem- As productive as hadron colliders are in probing nature at 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 masses, may well origi(ISR) over a very high-energy proton synchrotron, although thelatterwouldmaterialise10yearslaterintheSuperProton

Synchrotron (SPS). The ISR’s ﬁrst proton–proton collisions,

whichreachedacentre-of-massenergyof62GeV, tookplace on 27 January 1971, opening the era of hadron colliders. From the ISR came the ingenious conversion of the SPS nate from phenomena at energy scales inaccessible to any collider imaginable. Fortunately, models involving such scales can be tested nowandinthenearfuturebya seriesofexperiments–some using magnets from the LHC andHERAinfact–searching for very weakly interacting “slim” particles that arise in extensions of the Stand-

ardModel(seep25). Eﬀective ﬁeldtheoryisanotherpower-

fultooltopursuesuchsignals fromfarbeyondtheTeVscale, explains Steven Weinberg in this issue’s interview (p51).
–into a proton–antiproton collider (SppS), the demonstration

of large-scale superconducting magnet technology for the Tevatron at Fermilab, and the LHC, whose elegant magnet design has enabled the highest collision energies (13TeV) and luminosities to date. Each machine, and its increasingly complex detectors, was a step into the unknown, requiring the invention of new technologies and sharp political and organisational skills to build and operate ever larger facil-

ities. The payoﬀ was the discovery of the Standard Model’s

–cornerstones: the W and Z bosons at the SppS, the top quark

at the Tevatron, and the Higgs boson at the LHC. Not to be Discovery machine The LHC. omittedfromthehadron-beamcollidersuccessstoryarethe leapsinunderstandingofstronglyinteractingmatterbrought

Meanwhile at CERN: ATLAS reports the ﬁrst evidence for a

Eachmachine, andits increasingly complex detectors, was astepinto the unknown

aboutbyBrookhaven’sRelativisticHeavy-IonColliderandthe rare“Dalitz”decayoftheHiggsboson(p17);pulsed-modeantiLHC, andthedeep-inelasticscatteringexperimentsatDESY’s hydrogen paves the way to test antimatter in free fall (p7); and so-faruniqueelectron–protoncolliderHERA, whichrevealed the CLOUD experiment reveals a new mechanism that could

Half a century after the ISR’s ﬁrst collisions, and with at least quantum sensors target gravitational waves (p10); X-rays go

15 years of LHC operations still to come, particle physicists behindthescenesofsupernova1987A(p12);ahigh-performance

once again ﬁnd themselves debating the next best step for the computing collaboration forms to handle the big-physics data ﬁeld. True to form, as recommended by the 2020 update of the onslaught (p22); new twists in the ATOMKI tale (p74); and more.

Reporting on international high-energy physics

Argonne National Laboratory

Jeﬀerson Laboratory

Kandice Carter

JINR Dubna B Starchenko KEK National Laboratory

Hajime Hikino

Lawrence Berkeley Laboratory Spencer Klein Los Alamos National Lab

Rajan Gupta

NCSL Ken Kingery Nikhef Robert Fleischer Novosibirsk Institute

S Eidelman

SLAC National Accelerator Laboratory

Melinda Baker

SNOLAB Samantha Kuula TRIUMF Laboratory

Marcello Pavan

Technical illustrator

Alison Tovey

Advertising sales

Tom Houlden

Recruitment sales

Chris Thomas

Advertisement production Katie Graham Marketing and circulation Laura Gillham,

Jessica Pratten

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Matthew Chalmers

Associate editor

Mark Rayner

Editorial assistant

Craig Edwards

Archive contributor

Peggie Rimmer

Astrowatch contributor

Merlin Kole

Tom LeCompte

Brookhaven National Laboratory Achim Franz Cornell University

D G Cassel

DESY Laboratory

Till Mundzeck

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NEWS

ANALYSIS

AntimAtter

FOR

AEgISontracktotestfreefallofantimatter

PROFESSIONALS

theatomsareproducedtobedetermined with an uncertainty of around 100 ns. Further steps are required before the measurement of g can begin, explains Doser. These include the formation of a pulsed beam, greater quantities of antihydrogen, and the ability to make it colder. “Withonlythreemonthsofbeam timethisyear,andlotsofnewequipment to commission, most likely 2022 will be the year in which we establish pulsedbeam formation, which is a prerequisite forustoperformagravitymeasurement.”
AntiprotonDecelerator(AD)hasreported a milestone in its bid to measure the gravitational free fall of antimatter – a fundamentaltestoftheweakequivalence principle. Using a series of techniques developed in 2018, the team demon-

strated the ﬁrst pulsed production of

antiatoms, which allows the time at which the antiatoms are formed to be knownwithhighaccuracy. Thisisakey step in determining “g” for antimatter.

“This is the ﬁrst time that pulsed for-

mation of antihydrogen has been established on timescales that open the door tosimultaneousmanipulation, bylasers

Targeted approach

or external ﬁelds, of the formed atoms,

as well as to the possibility of applying thesamemethodtothepulsedformation ofotherantiprotonicatoms,”saysAEgIS spokesperson Michael Doser of CERN. “Knowing the moment of antihydrogen formation is a powerful tool.” Generalrelativity’sweakequivalence
Followingaproof-of-principlemeasurementofgforantihydrogenbytheALPHA collaborationin2013, ALPHA, AEgISand a third AD experiment, GBAR, are all targeting a measurement of g at the 1% level in the coming years. In contrast to AEgIS’s approach, whereby the vertical deviation of a pulsed horizontal beam of coldantihydrogenatomswillbemeasured

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