Strategy Brochure CERN

8/9/2019 Strategy Brochure CERN

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Towards a European strategy for particle physic3

Contents

Towards a European strategy for particle physics

Particle physics –a cornerstone of European scientiÞc strategy (4-5)

Opening a gateway to the Universe (6-13) Illuminating the high energy frontier (14-17

Zooming in on new discoveries (18-19)

Matter and antimatter– a question of balance (20-21

Three neutrinos that made our world (22-23)

Underground physics – exploring rare phenomena (24-2

Light sources – powered by particle physics (26-2

Applications in medicine (28-29)

From the Web to the Grid (30-31)

Particle physics in Europe (32-33)

Particle physics in the World (34-35)

The European strategy for particle physics (36-37)


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Towards a European strategy for particle physics4

Particle physics a cornerstone of European scienti Þ c strategyParticle physics – the study of the structure of the Uat its most fundamental level – stands on the thresa new era of discovery and insight. As the scale o

perimental and theoretical challenges increases, Eparticle physicists need a strategy to ensure that Eurcontinue to lead the exploration of this exciting doman increasingly global framework.

The extraordinary UniverseThe modern science of particle phys-ics is the direct descendant of ancientGreek philosophical tradition. It facesthe challenge of identifying the funda-mental constituents of matter and the basic rules governing their behaviour. Itaims to explain how these constituentsand rules relate to all physical phenom-

ena we observe in the Universe today.We now understand a great deal aboutthe ordinary matter from which we, andall the stars and planets, are made. Weare able to predict with amazing preci-

sion the results of experiments, using a beautiful mathematical description of thefundamental particles and the way theyinteract, called the Standard Model. Thisis built upon the twin foundations of


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Towards a European strategy for particle physic5quantum mechanics and special relativ-ity, revolutionary scientiÞ c concepts de-veloped in Europe during theÞ rst halfof the 20th century. During the secondhalf of the 20th century, many of the keydiscoveries that led to the subsequent de-velopment of the Standard Model werealso made in Europe. Today the Stan-dard Model ranks alongside remarkableadvances in biology, medicine, the envi-ronment, cosmology and other physicalsciences as one of the greatest scientiÞ cachievements of the 20th century.

But there is much more to learn in all do-mains, and particle physics is no excep-tion. Although we understand the com-position of ordinary matter at its mostfundamental level, we now know thatit accounts for only about 4% of the to-tal mass and energy of the Universe. Theremaining 96% is made up of some newcomponent – usually called dark matterand dark energy – about which we knowvery little, although we are immersed inan invisible sea of it. This missing com-ponent does not shine or reß ect light, andits presence has been exposed through itseffects on the gravitational forces shap-ing the Universe. Understanding thenature of dark matter and dark energy is just one of the big challenges for particlephysics today, as we try toÞ ll the gaps inour knowledge of the ordinary and theextraordinary.

A global endeavour Particle physics is big science. It requiresthe development of huge scientiÞ c instru-ments that push technology to the limit.It demands concentration of facilities andintellect, and has long been organised onan international scale. In the Europe ofthe 1950s, 12 countries chose to combinetheir strengths and create a EuropeanOrganization for Nuclear Research. Formore than 50 years, this Organization hasoperated a major laboratory, CERN, nearGeneva. Its Member States have grownto 20, each with a thriving domestic pro-gramme, including a number of world-class national laboratories. In addition,the particle physics community has longset an example of global collaboration,with scientists from all over the world

sharing their knowledge and experiencein the pursuit of common goals. It is noaccident that particle physics gave rise tothe World Wide Web.

A new adventureOver the next few decades, particle phys-ics experiments should complete ourknowledge of ordinary matter, and beginto explore the extraordinary Universe ofdark matter and energy. The next step onthis voyage of discovery will be taken bythe Large Hadron Collider accelerator atCERN. After a decade in the making, thismachine, 27 kilometres in circumference,and its four mammoth particle detec-tors, will begin commissioning in 2007,and should soon start answering some ofthe most pressing questions. It will alsolight up the way ahead to a more com-

plete theory and make clear which newfacilities, such as the International LinearCollider, will be needed to explore andverify it.

Towards the strategyA European strategy for particle physicsis needed to meet the challenges posed by the increasingly global nature of fron-tier facilities. In 2005, the CERN Councilformed an ad hoc scientiÞ c group to pro-pose such a strategy. European particlephysics is founded on strong nationalinstitutes, universities and laboratories,as well as CERN. In taking particle phys-ics forward, Europe must build on theleadership it has established in theÞ eld,while at the same time engaging evenmore fully with the global particle phys-ics community.

Developing the strategyThe CERN Council decided in June 2005 to set up a scientiÞ c advisory group,the strategy group, to propose a strategy for European particle physics in thedecade to come. The resulting strategy document was approved by Council at aspecial meeting in Lisbon on 14 July 2006.

The strategy addresses:•accelerator based particle physics•non-accelerator based particle physics•R&D for novel accelerator and detector technologies

It is the result of a bottom-up approach with the following key phases:•an open symposium in Orsay in January 2006•a strategy group meeting in Zeuthen, Berlin, in March 2006•a dedicated meeting of CERN Council in Lisbon in July 2006

All relevant documents concerning this work are available at:http://cern.ch/council-strategygroup/


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The Standard Model is a triumphof 20th century science. It describesthe particles that make up our Uni-verse and the forces acting betweenthem. However, it does not explainwhy there are three families of mat-

ter particles, nor why there are fourapparently distinct forces actingbetween them.


Opening a gateway to the Universe

The giant new experiment in Geneva will soon reveal more of the still well guarded secrets of the Unparticle physicists from the Atlantic to the Black Sthe Arctic to the Mediterranean, the discoveries wilbeginning in the search for answers to fundamental qWhy does matter have mass? Where did all the anti And what is the mystery of the missing 96% of theenergy of the Universe?


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Towards a European strategy for particle physic 7

SLD picture(to be found)

Throughout recorded history, humanshave sought to understand what theUniverse contains, what it is made of,and how it came to be. This search foran understanding of the matter in andaround us has progressed through manystages, and particle physics is its cuttingedge. The objective of particle physicsis to discover the fundamental laws ofNature that govern the behaviour of theUniverse: to explore the frontiers of mat-ter, energy, space and time.

Particles and forcesThe ancient Greeks and their succes-sors went from qualitative ideas abouta handful of fundamental constituentsof matter – earth, air,Þ re and water - tothe atomic theory that wasÞ nally con-Þ rmed just over a century ago. In quicksuccession, the discoveries of the elec-tron, radioactivity and nuclei revealedthat atoms were not fundamental. Later20th-century experiments revealed thatnuclei are themselves composed of pro-tons and neutrons, and that these are inturn composed of yet more fundamentalentities called quarks. A picture emerged,called the Standard Model, in which allphysical phenomena can be reduced to asmall set of indivisible particles and theforces that govern their interactions. Theparticles are the quarks of which protons

and neutrons are composed, along withothers, such as electrons, which are col-lectively known as leptons. Their inter-

actions explain how the particles sticktogether, how they decay and how theyform complex structures from the micro-scopic to the macroscopic scale. Modernparticle physics aims to understand thisframework, its origins and its implica-tions, in greater depth.

Essential to an understanding of the com-ponents of particles are the fundamen-tal forces that hold them together andcause many of them to decay. Electricity,magnetism and gravity are forces felt ineveryday life. Inside the atom, a strongforce conÞ nes quarks within protons andneutrons, which are in turn combinedinto nuclei, while a weak force causesthe radioactive decays of some nuclei.

Two facilities that put the Standard Model to a gruelling test throughthe 1990s. Left, the European LargeElectron Positron collider (LEP),which demonstrated incontrovert-ibly that there are three families ofmatter particles. Right, the SLDdetector at the Stanford LinearAccelerator Center in the US.


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Left: Tracks betraying the presenceof a Z particle in the UA1 detector atCERN.

Right: The UA2 detector.

The discovery of W and Z particles atCERN in the 1980s brought veri Þca-tion of the theory that uni Þes two ofNature’s forces.

lows us, among other things, to establishhow they contributed to the evolution ofthe Universe into what we observe to-day. The Standard Model accounts withextraordinary precision for the results of

these experiments. It provides the math-ematical instrument with which to calcu-late the behaviour of matter one tenth ofa billionth of a second after the Big Bang,when the energy density of the Universematched the energies achievable in to-day’s experiments, and to extrapolate theUniverse’s subsequent evolution.

The Standard Model extends and gener-alizes the combined theory of electricityand magnetism that was developed inthe 19th century, and which was revo-lutionized by quantum mechanics andspecial relativity. It includes a successfultheory of the strong nuclear force andit predicted the properties of the weakforce later discovered in experiments in

the 1970s and 1980s. In the last decade ofthe 20th century, precise measurementsof the properties of the weak force putthe Standard Model on a very solid ex-perimental foundation.

Weighty questionsThe Standard Model is a triumph of hu-man ingenuity, patience and painstakingresearch. It is the most accurately testedand veriÞ ed theory in the history of sci-ence.

Nevertheless, the successes of the Stan-dard Model raise deeper questions, thesolutions to which are the current objec-tives of particle physics. We know thatmatter has weight. Newton taught usthat weight is proportional to mass. Ein-stein in turn demonstrated the equiva-lence of mass and energy. However, nei-

Together, these forces explain how theSun shines and provides the sources ofenergy on which our civilization and itstechnologies are based.

Most of our understanding of particlephysics derives from experiments per-formed with particle accelerators. Ac-celerating particles to velocities closeto the speed of light and bringing theminto collision at very high energy allowsus to exploit Einstein’s equation E=mc²and to convert this energy into new par-ticles. The higher the energy, the heavierthe particles that can be produced, mak-ing it possible to explore states of matterthat, while playing no apparent role inour daily life, were nevertheless pres-ent in the early instants of the Universe,when the prevalent high energy madetheir production possible. The study ofthe properties of such particles in experi-ments at today’s large accelerators al-


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Particle tracks hold the key to understanding new phe-nomena. In this simulation of a collision at the LHC,the red tracks originate from the decay of a Higgs par-ticle, whose discovery would help to explain the mys-tery of mass.

Towards a European strategy for particle physic 9

ther Newton nor Einstein explained theorigin of mass itself, or why some parti-cles are very heavy whilst others have nomass at all. Since the mass of the electrondetermines the sizes of atoms, and since

radioactivity is relatively uncommon be-cause the carrier of the weak force – theW boson, a particle discovered at CERN– weighs as much as a medium-sized nu-cleus, understanding the origin of masswill unlock some of the most profoundmysteries of the Universe.

Whatever the explanation for particlemasses, it requires new physics to mani-fest itself at some inÞ nitesimally smalldistance, only slightly smaller than thatalready probed by particle accelerators.This new physics is necessary to explainthe great success of the Standard Model,and will be explored with the next gen-eration of particle accelerators.

Ordinary matter accounts for just 4% of the mass and en-ergy of the known, visible, Universe. The remaining 96%makes its presence felt through gravitational effects. Some21% is thought to be dark matter, with the rest being darkenergy.

4%

21% 75%

The Standard Model provides a possiblemechanism to explain particle masses,known as the Higgs mechanism. Thisidea envisages a Universe permeatedwith a medium, in addition to the famil-

iar gravitational, electric and magneticÞ elds, whose interactions with elemen-tary particles provide their masses. Fluc-tuations in this newÞ eld should appearas a new particle, which has been namedthe Higgs particle. Its mass is so largeand it is so rarely produced that it hasescaped detection at particle acceleratorsuntil now, but the Standard Model pre-dicts that, if it exists, it must be within thereach of the LHC experiments.

Testing this idea, and discovering theHiggs particle, is a top priority for thenew generation of particle physics exper-iments. However, while the Higgs mech-anism provides a possible way to explainthe masses of particles, it does not pro-


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Probes such as NASA’s WMAP can ‘see’ back in time to the point at whichthe Universe became transparent, at an age of about 380,000 years. To probe phenomena occuring at earlier times, back into the Þrst second of the Uni-verse’s life, requires particle accelerators. WMAP will soon be joined by theEuropean Planck probe, which will further re Þne our understanding of the earlyUniverse.

vide a satisfactory understanding of theorigin of mass itself. Particle physicistsexpect that this understanding lies insome extension of the Standard Model,an extension that would not only pro-vide a conclusive answer to the questionof mass, but also unveil the existence ofnew particles and link the acquisition of

mass to other mysteries of the Universe.For example, in some of the alternativeproposals new particles exist in addi-tion to the Higgs particle. The lightest ofthese might provide the dark matter thatno telescope can detect but which mustexist to explain the fabric of the Universeand the formation of structures, such asgalaxies, within it. Other proposals pos-tulate the existence of new dimensionsof space that would be discernible to thenext generation of accelerators.

The understanding of mass is the lastmissing ingredient of the Standard Mod-el. It is nevertheless likely that, as weprobe at higher and higher energies, newphenomena will appear.

The extraordinary UniverseWe know that only 4% of the Universe ismade up of what we think of as ordinarymatter. The remaining 96% is extraordi-nary – dark matter and energy that is allaround us but invisible to us. The nextgeneration of accelerator experimentswill take theÞ rst steps into this extraor-dinary world.

The Universe is expanding at an accel-erating rate, and must have been veryhot and dense when it was young. Theconditions a fraction of a second after theBig Bang are similar to those created bycolliding particles together at very highenergies using powerful accelerators. Ifwe want to push the understanding ofthe primordial Universe to times earlierthan a tenth of a billionth of a second,the time ruled by Standard Model phys-ics, we need to push further the frontierof high-energy accelerators. This is nec-essary to clarify the origin of dark mat-


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Left: Satellite-based global positioning systems rely on general relativity for their pinpoint accuracy. Right: The humbletransistor - a quantum machine at the heart of all modern electronic devices. We rely on quantum mechanics and generalrelativity every day, yet the two theories remain to be reconciled.

ter and energy, and toÞ nd an explana-tion for the dominance of matter overantimatter in today’s Universe. Goingto higher energies will allow us to peer beyond the Standard Model, uncoveringnew phenomena and gaining a greaterunderstanding of the workings of ourUniverse.

Probes such as NASA’s WMAP can ‘see’ back in time to the point at which theUniverse became transparent, at an ageof about 380,000 years. To go back fur-ther, right into theÞ rst second of the Uni-verse’s life, requires particle accelerators.

In search of the superforceThe intellectual achievement of the Stan-dard Model is to have successfully iden-tiÞ ed a common framework describingall particles and their interactions by aunique and concise set of rules. This isunderscored by the uniÞ cation of twoamong the fundamental forces – electro-

magnetic and weak – and by the elegantstructure within which the elementarymatter particles are organized.

Three different ‘families’ of matter par-ticles exist, one that makes up the ordi-nary stable matter composed of protons,neutrons and electrons, and two heavier

families that have been revealed in cos-mic rays and accelerator experiments.The particles in the extra families are un-stable and, once produced, decay to theparticles of theÞ rst family after a tinyfraction of a second. They play no part inthe ordinary matter from which we aremade. The Standard Model does not ex-plain why there are three families of mat-ter particles. However, they played a cru-cial role in the processes taking place inthe early Universe. Their presence mayhave helped create the conditions thatremoved all antimatter and let the mat-ter we are made of survive, and they mayhave determined the relative abundanceof the light nuclei that continue to fuelthe stars.


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CDF is one of two experiments thatare currently exploring the high-energy frontier at Fermilab in theUS, home to the Tevatron proton-antiproton collider.

Today, we see four distinct forces atwork. The mathematical frameworkof the Standard Model shows a strongunderlying similarity between the elec-tromagnetic, weak and strong forces.This suggests that these forces could be joined together at some very high energyscale; there is even a possibility that, atsome still higher energy scale, they could be joined by gravity in a single “super-force”. Experiments at accelerators, andon neutrinos produced by cosmic raysand the Sun, reinforce this idea, offeringhints as to how the fundamental forcesmight be uniÞ ed at high energies and inthe very early Universe. Among the con-sequences of the uniÞ cation of forces isthe uniÞ cation of matter particles, lead-ing to the transformation of quarks intoleptons, and ultimately to the possibledecay of a proton into an antielectronand pure energy. If conÞ rmed by experi-ments, proton decay would provide anunequivocal proof of force uniÞ cation,and demonstrate matter’s ultimate instability. However, although the Standard

Theoretical physicists have come upwith many ideas for what lies at thehigh energy frontier. Experiment isabout to put them to the test.

Model seems capable of describing theuniÞ cation of the forces, it does not ex-plain why they have such evidently dif-ferent characteristics when we examinethem at work today.

A question of scaleThe deepest quandary in fundamentalphysics may be how to reconcile two fun-damental pillars of 20th century science,quantum mechanics and the general the-ory of relativity. Both theories work, andwe put them to use in everyday life.

Quantum mechanics underpins our un-derstanding of the microworld – theworkings of atoms and the fundamentalparticles. Without it, there would be notransistors and no consumer electronics.General relativity is a theory of gravity.It governs the large-scale behaviour ofthe Universe, and is taken into accountin achieving pinpoint accuracy in globalpositioning systems.

Electron-proton collisions at theHERA accelerator are probing moredeeply than ever into the structure ofthe proton and neutron at the DESYlaboratory in Germany.


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Direct evidence for gluons, carriersof the strong force that binds quarkstogether, was Þrst seen at DESY in1979 in patterns of tracks like this inthe TASSO detector.

OPAL, one of four detectors at CERNthat measured the number of familiesof fundamental particles, and which put the Standard Model to a gruellingexperimental test.

Inside the Gargamelle bubble chamberat CERN, which in 1973 found the Þrst evidence for particle interactions predicted by the theory that uni Þesthe electromagnetic and weak forces.

Quantum mechanics and the generaltheory of relativity were the greatestachievements in fundamental physics inthe Þ rst half of the 20th century, yet thetwo seem to be mutually incompatible.Any reconciliation is likely to requirenew insights into the natures of spaceand time themselves.

Through the energy frontier We will not know which, if any, of thesetheories has been endorsed by Natureuntil the next generation of acceleratorsstarts to provide experimental results.The Large Hadron Collider (LHC) cur-rently nearing completion at the CERNlaboratory near Geneva will provideÞ rstdirect information on physics at the nextdistance or energy scale. ItsÞ ndings willguide scientists towards the answers tomany of the questions discussed here,and will undoubtedly trigger new ones.Making sense of the new scenarios un-veiled by the LHC, through the develop-ment of new theories and by designing

and performing new experiments, will be a great challenge to physicists world-wide.

If the LHC discovers a candidate for theHiggs particle, will it have all the proper-ties required for its role as mass donor toall the elementary particles? If the LHCÞ nds some new particles not predicted bythe Standard Model, could they provideall the dark matter in the Universe? Ifthe LHCÞ nds new dimensions of space,how many will there be, how large, andof what shape? Will the new physics castlight on the problems of force uniÞ cationor the reconciliation of quantum mechan-ics and gravity? Could it also be probedin non-accelerator experiments?

Finding the answers to these questions re-quires a worldwide effort, within whichEurope should play a leading role, deÞ n-ing a strategy assembled from severalcomplementary scientiÞ c elements. Newexperiments at the high-energy frontierare central to this strategy, but other tac-

tics may be useful. Lower-energy accel-erators with high-intensity beams, forexample, may have a role to play.

What new accelerators will we need tounravel fully the problems of mass anduniÞ cation? Are the technologies neededto build these accelerators and their ac-companying detectors already in hand,

or do they require further development?Do we need higher-precision tests of theStandard Model and better understand-ing of the forces and particles it contains?What are the roles for future non-accel-erator experiments? What are the rolesfor theoretical physics in guiding and in-terpreting future experiments?

The LHC will soon revolutionize our un-derstanding of matter, forces and space.Now is the time to get ready to exploit

the scientiÞ

c opportunities it will reveal.


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The LHC, accelerating science


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Illuminating the high energy frontier

The Large Hadron Collider will generate billions oevery second. It will amass mountains of data everyilluminate a new landscape of physics and trigger a discovery. It could even reveal extra dimensions of s

Particle physics is a voyage of explora-tion, and like any such adventure it pass-es through alternating cycles of discov-ery and understanding. With the LargeHadron Collider (LHC), currently underconstruction at CERN, we are about toenter a new era.

Physicists have been painstakingly put-ting the Standard Model together forfour decades, in great detail. They arenow ready to explore what lies beyond.Although there are many theories as towhat that might be, we are essentiallyin the dark. The beam that will throw asearching light on a new landscape ofphysics beyond the Standard Model isthe LHC.

The LHC will be the world’s most pow-erful particle accelerator. When runningat full energy, it will collide protons at acombined energy of 14 TeV (see box), giv-ing access to physics at an energy scaleabout ten times higher than has beenopen to exploration so far.

Frontier scienceParticle physicists are very excited bythe LHC. There are very strong reasonsto believe that the energy frontier it willreach is crucial. For example, the mecha-nism that governs particle masses should become visible. This mechanism may an-nounce itself through the production ofone or more so-called Higgs particles, so

a major theme for the LHC is to searchfor and study these.

The Standard Model requires Higgs par-ticles so that it can continue to describeNature at the energies that will be probed by the LHC. If the Higgs mechanism is

the correct hypothesis, then our calcula-tions and measurements tell us that Higgsparticles must be produced at the LHC.And if there are no Higgs particles? Thenit seems unavoidable that something elsemust emerge from the shadows as an al-ternative to the Higgs mechanism.

Theorists speculate as to what mighthappen at the LHC and at high ener-gies, where the Standard Model is no

longer enough. By far the most popularextension of the Standard Model is calledsupersymmetry. This provides a wayfor the strengths of the electromagnetic,weak and strong forces to converge natu-rally to the same value at very high ener-gy, leading to uniÞ cation of these forces.

Supersymmetry also predicts a rangeof so-far unobserved particles and soprovides a possible explanation for theenigmatic cosmic dark matter. If super-symmetry is right, the lightest super-symmetric particles could be producedat the LHC.

Another possible road beyond the Stan-dard Model requires the introduction ofextra dimensions of space. These would

What is a TeV?

A TeV is a unit of energy used inphysics. One TeV is roughly equiva-lent to the energy of motion carriedby a mosquito. What makes the LHCspecial is that it concentrates four-teen times this energy into a space atrillion times smaller than a mosquit


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Particle Þreworks. Each collision gives rise to a spray of new par-ticles such as these, simulated inthe ATLAS detector. This patternshows what the detector would seeif a mini black hole were producedand immediately decayed.

With its extremely demanding computing and networking needs, it is no ac-cident that particle physics attracts the IT industry. The CERN openlab fordatagrid applications, for example, brings cutting edge science and industrytogether to the bene Þt of both.

be invisible to us much as a third dimen-sion would be beyond the experience ofan ant crawling on aß at sheet of paper.If extra dimensions exist, they couldproduce measurable effects in the en-ergy region to be explored by the LHC.This would allow the LHC to enter thedomain of quantum gravity, providingexperimental data that will help us tounderstand how to reconcile quantummechanics and gravity.

Frontier technologyThe LHC is a machine of superlatives.It is the world’s largest superconduct-ing installation. Its interior is colder thanouter space. It contains a vacuum moreperfect than anywhere between the Earthand the Moon. It will produce billionsof proton-proton collisions per second.All this makes it not only a machine forfrontier physics, but also a machine forfrontier technology.

Housed in a 27 km long circular tunnel,

the LHC is a true giant. It is the mostcomplex scientiÞ c instrument ever con-structed. At its heart are superconduct-ing magnets based on coils made fromniobium-titanium wire that conductselectricity without resistance at low tem-perature. The LHC magnets will operateat 1.9 degrees above absolute zero (about-271 C), and they are cooled by super-ß uid helium.

A major feature of these magnets is theirtwo-in-one design. To provide oppositemagneticÞ elds for the two beams travel-ling around the machine in opposite di-rections, two coils are embedded withina single structure. The LHC uses 1232 di-pole magnets to guide the beam, togetherwith a few thousand additional magnetsto focus the beams andÞ ne-tune the or- bits. Altogether, they use enough super-conductingÞ lament to stretch to the Sunand back Þ ve times, with enough leftover for a few trips to the Moon.

The high intensity of the LHC beams,


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The concentric structure of the CMS detector is clearly visible during its assem-bly. When the LHC is running protons will collide head on at the centre, and thevarious layers will measure different particle properties, building up a complete picture of each collision recorded.

Assembly of a ring-imaging Cher-enkov detector for the LHCb detec-tor is carried out under extremelyclean conditions.

which gives rise to the enormous collisionrate, poses its own challenges. For exam-ple, at full intensity there will be enoughenergy in each beam to melt about 500 kgof copper. This is 200 times more than thehighest stored energies achieved in anyprevious accelerator.

Each time protons collide inside a par-ticle detector, between 100 and 1000particles will emerge. Since there will beup to six hundred million collisions persecond in each detector, this adds up toan enormous amount of data. Powerfulelectronic systems will select the interest-ing collisions, reject those that are unin-teresting, and record the remaining data.Even after rigorous selection, the volumeof data to be recorded by each experi-ment wouldÞ ll some 100 thousand DVDsevery year.

Two detectors called ATLAS and CMShave been designed to see anything thatthe LHC will reveal. Each surroundsa point at which protons collide, and

measures the energies and trajectoriesof the emerging particles. Each has beenprepared by a collaboration of around2000 researchers from around the world,a prime example of different culturesworking towards a common goal. Top oftheir priority lists are Higgs particles andsupersymmetry.

Two other detectors, ALICE and LHCbare also under construction. ALICE willstudy matter as it was in theÞ rst in-stants of the Universe, in an attempt tounderstand how it evolved into matteras we know it today. LHCb will focus onnature’s preference for matter over anti-matter.

Frontier thinking Conceived in the 1980s, approved in the1990s, and scheduled to start commis-sioning in 2007, the LHC is a huge invest-ment and a long-term project. In itsÞ rstphase of operation it is set to illuminatea vast new terrain of physics for explora-

tion, and set a course for the future. Whatnew facilities that future will demand re-mains to be seen, but the LHC will oper-ate for at least a decade at the forefront ofscience. Beyond that, the LHC could it-self become part of the future landscape,through upgrades to push the number ofcollisions higher, or to increase their en-ergy beyond the current frontier.


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Zooming in on new discoveries

Turn on, tune in and see what drops out: discovethe new LHC could lead straight to a new and evchallenging research tool. That is because it is one tha new horizon, quite another to explore it.

A simulated collision at a linearelectron-positron collider.

If a searchlight is the best way to illumi-nate a large area of terrain, then a power-ful spotlight is the best tool for exploringthe detail. Electron-positron colliders arethe spotlights of particle physics, andtheir Þ nely focused beams will probe thesmallest features.

Circular proton colliders such as theLHC are the instruments of choice fordiscovery in particle physics. They can

cover a broad spectrum of energy, sothey illuminate vast new landscapes,and bring anything new into sharp relief.However, what is a strength for discov-ery is a weakness for precision investiga-tion where the ability to tune the energyprecisely is needed, and this is what elec-tron-positron machines do best.

The basic difference between the two isthe nature of the collided particles. Pro-tons are composite particles made up ofsmaller entities called quarks and gluons,which share the total energy in a randomway. Since the interesting physics comesfrom collisions between these smallerentities, proton machines produce colli-sions with a broad range of energy.


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An artist’s impression of a possibleinternational linear collider.

A simulation of the Þeld insidesuperconducting cavities developedby the DESY laboratory for a futurelinear collider. Cavities such as thisare also powering DESY’s free elec-tron laser facility (pp26-27).

A prototype copper acceleratingstructure for the Compact LinearCollider study, which is investigat-ing novel accelerating technology.

Going straight Electrons and positrons are fundamentalparticles so the energy of a beam can beprecisely tuned to home in on whateverenergy the physicists need. But electronand positron beams do not like to besteered around corners. They lose energyas they curve round, making it harder toreach the highest energies. The machinethat will zoom in on the LHC’s discov-eries is therefore likely to be straightinstead of circular.

A linear electron-positron collider woulddeliver precise data to build on the dis-coveries of the LHC, it would completelymeasure features of particles discoveredat the LHC that are within its reach, per-haps describing Higgs particles and thesupersymmetric particle that could ex-plain the nature of the dark matter andenergy in the Universe.

Universities and laboratories from allover the world are already working ona detailed design for an InternationalLinear Collider (ILC). Physicists and en-

gineers with decades of experience haveteamed up with young scientists toÞ gureout the best way to build this extremelychallenging machine. For theÞ rst time,this effort is being coordinated from theoutset on a global scale, because wherev-er such a machine is built it will be a fa-cility for the world. European scientists,working closely with researchers fromother continents, lead theÞ eld in many

areas of this research.

Parallel linesThey plan to smash electrons and posi-trons together in two 20-kilometre su-perconducting linear accelerators, ini-tially producing collisions at energies of0.5 TeV. This is within the energy rangeto be explored by the LHC. In parallel, aEuropean initiative in novel acceleration

technology, known as the Compact Lin-ear Collider (CLIC) study, could deliverenergies up to several TeV, should theLHC’s discoveries point to the need forhigher energy.

By the end of the decade, the ILC techni-cal design will be complete, the LHC willhave illuminated the features of the newTeV-scale landscape, and the CLIC studywill have demonstrated whether the newtechnology is viable. These three resultswill help the global particle physics com-munity to take an informed decision onthe shape of experiments to come.

Whatever that decision may be, an over-

lap in operating time between the LHCand a linear collider would allow the datafrom one machine to inß uence investi-gations at the other. The spotlight andthe searchlight will work in tandem.Rather than seeing double, particlephysicists will see in depth and gain newperspectives.


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Antimatter is described by theory, it iscreated by cosmic rays in collisions withthe atmosphere and it is studied in labora-tories. Scientists believe that it must haveexisted in huge quantities a few moments

after the Big Bang when matter was alsocreated. But no signiÞ cant amount of an-timatter has so far been found in our Uni-verse. If the same amounts of matter andantimatter were present at the beginning,where has all the antimatter gone?

The theory of antimatter, developed in

the 1930s, says that for every type of mat-ter particle, there exists an equivalentparticle of antimatter. Antimatter par-ticles have the same mass, but oppositecharge to their matter equivalents. In1932, the discovery in cosmic rays of thepositron, the antimatter counterpart ofthe electron, provided theÞ rst experi-mental conÞ rmation that antimatter wasmore than just a theory.

With the discovery of antiparticles, inter-est shifted to studies of their properties.If we really do live in a Universe of mat-ter, then something must have happenedto the antimatter. Nature must have apreference. The quest to understand thispreference takes place at the level of theparticles and antiparticles themselves.

Broken symmetryIn 1964 physicists working with particlescalled neutral kaons showed that the la- bels matter and antimatter are more than just convention. There really is a differ-ence. Neutral kaons break the so-calledCP symmetry (see box), which would bea perfect symmetry if Nature were evenhanded. Many years after thisÞ rst hint

Matter and antimatter a question of balance

We exist because antimatter does not – at least, lethal quantities. But what happened to the missing substance? Why does the Universe seem to favosubatomic twin, rather than the other? To answequestions, particle physicists must go back to the be

The wire chamber of the KLOE de-tector at Italy’s Frascati laboratorymakes a beautiful sight. KLOE isengaged in research to understand

matter-antimatter asymmetry.


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of Nature’s bias, experiments were ableto reveal more. The rate of disintegra-tion into two pions of a neutral kaon andof a neutral anti-kaon is not the same, aprocess called direct CP-violation, a phe-nomenon that truly distinguishes par-ticles from antiparticles.

This result was not entirely unexpected.CP-symmetry breaking is one of the con-ditions necessary to develop an imbal-ance between matter and antimatter inthe Universe. Kaons provided theÞ rst

evidence, but frustratingly the amountof CP-symmetry breaking seen was notnearly enough to account for the ob-served matter-antimatter imbalance inthe Universe. More recently, experimentshave conÞ rmed that CP-symmetry is also broken in particles called B mesons, buthere too the amount is not enough to ac-count for the apparent bias towards mat-ter across the Universe.

Perhaps there is another explanationfor the apparent absence of antimatter.Experiments have been sent into space,or high into the atmosphere, to look forevidence of antimatter in the cosmos.If these were to detect a single complexnucleus made entirely of antiparticles -

CP – the imperfect mirror Each of C and P are symmetries thatare conserved in most particle inter-actions. C represents swapping thecharges of all the particles in an in-

teraction. If the interaction looks thesame before and after, then C sym-metry is said to be conserved. If not,C is a broken symmetry. P is called parity and it corresponds to a mirrorvision that reverses all three spatialco-ordinates. Physicists once thoughtthat each of these symmetries wasconserved in particle interactions,but then in 1956 experiments dem-onstrated that P could be broken.At the time the CP combination wasthought to be conserved, but this too proved not to be the case.

The US BaBar detector (left) and the Japanese Belle detector have made precisemeasurements of matter-antimatter asymmetry in B mesons.

The small payload at the back of thespace shuttle is the Alpha MagneticSpectrometer, AMS, an experimentthat ßew on the shuttle in 1998 tolook for antimatter in space.

anti-helium or anti-carbon, for example- that would be powerful evidence thatsomewhere in space large amounts ofantimatter exist in the form of anti-stars,or anti-galaxies. So far, however, not asingle anti-nucleus has been seen.

The quest to understand the matter-an-timatter imbalance continues in labora-tories such as CERN where anti-hydro-gen atoms can be produced and studied.Preparations have begun to compare theproperties of atoms of anti-hydrogen

with those of hydrogen, the simplest andmost precisely known atoms. It is tooearly to say what such comparisons will bring, but one thing is for certain: nei-ther searches for antimatter in space, norexisting measurements of matter-anti-matter asymmetry in the laboratory, canexplain Nature’s observed preference formatter. Some as yet unknown phenom-enon must be responsible and the chal-lenge for particle physics is toÞ nd it.


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Three neutrinos that made our world

Don’t make light of them. These ghostly particles through planets as if they were not there but somthe neutrinos know how to throw their weight arouparticles that began as notional units of subatomic pÞt andloss are now credited with a role in shaping the Univ

A beam of neutrinos sent throughthe Earth’s crust from CERN to theGran Sasso underground laboratorynorth of Rome will help physiciststo understand neutrinos better.


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Neutrinos: almost massless, they couldpass through 50 light years of lead with-out interacting, yet in theÞ rst billionthsof a second after the Big Bang they couldhave determined the shape of the Uni-verse today. As particle physics shiftsits emphasis towards why things are theway they are, new tools will allow us tostudy these mysterious particles, and de-termine the role they played when theUniverse was born.

Neutrinos were proposed in 1930, tosolve an accountancy puzzle in experi-mental physics. When certain atoms de-cay, emitting an electron, something elseis needed to balance the energy budget.That something else is a neutrino. In the1970s, neutrinos helped provide the ex-perimental foundation of modern parti-cle physics. Three and only three types ofneutrinos have been discovered, and theStandard Model, in which neutrinos bearno mass, has become a powerful and con-sistent theory for almost all phenomenaobserved in particle physics today.

But not quite all, for neutrinos have also become theÞ rst heralds of physics from beyond the Standard Model. So-calledneutrino oscillations, in which the tinyparticles can change from one type to

another, were observed in neutrinosemitted by the Sun and in cosmic rays,and then conÞ rmed by experiments withneutrinos produced in nuclear reactorsand particle accelerators. Neutrino os-cillations are clear evidence that there isphysics beyond the Standard Model, be-cause these oscillations can only happenif neutrinos have mass.

Massive consequencesThe fact that neutrinos have mass hasprofound consequences. Having mass

but no charge, neutrinos could be theirown antiparticles, a property possessed by no other fundamental particles. Andthe existence of three types of neutrinoscould lead to antineutrinos with differ-ent properties from neutrinos. Neither ofthese phenomena has yet been observed, but if both were true, neutrinos wouldhold the key to one of the longest stand-ing mysteries of the Universe.

We imagine the Big Bang as the transfor-mation of a world of pure energy into aworld of particles, with large and equalnumbers of particles and antiparticles.Since matter and antimatter annihilateon contact, it is a mystery that only mat-ter seems to remain. A small transition of

some of the antimatter into matter wouldhave allowed matter to remain to buildour Universe, a possibility that massiveneutrinos could offer.

The discovery that neutrinos have masshas stimulated the emergence of a grow-ing community of particle physicists inpursuit of these questions, with new ex-periments around the world. In Europe, aneutrino beam is being sent from CERNto the Gran Sasso laboratory 730 kilome-tres away. In Japan and the US similarprogrammes exist or are planned in thenear future.

But neutrinos are slippery subjects. Theyhardly ever interact – they pass throughother matter as if it wasn’t there – and it isdif Þ cult to produce them in a pure state.Detailed studies will require more pre-cise instruments and more intense beamsthan any available today. New detectors,weighing up to a million tons, are beingdiscussed, together with very intenseand pure neutrino beams produced fromthe storage of unstable nuclei or fromunstable particles like muons. In Europe,physicists have begun to test these newtechniques, preparing to discover justhow these elusive particles may haveshaped our Universe.

The giant Super-Kamiokande detec-tor in Japan found the Þrst evidence for neutrino oscillation in 1998.

An engineering drawing of the Muon Ionisation Cooling Experiment (MICE)at the CCLRC Rutherford Appleton Laboratory in the UK. This experiment isan essential step in R&D towards the realization of a neutrino “factory”.


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Underground physicsexploring rare phenomena

Somewhere in the subatomic world, a neutrino hitsa WIMP shows its dark side and a proton gives up These vanishingly rare events could never be detectirradiated and bombarded surface of the Earth. So pphysics has gone deep underground, to add new meresearch in depth.

Laboratories deep underground, shielded by the Earth’s crust from the confusion of

particles that rain down on the surface inthe form of cosmic rays, provide an ideallocation for exploring rare phenomena.They complement and reinforce researchprogrammes at accelerator laboratories.Europe has four world-class deep un-derground laboratories: three close toroad or rail tunnels under mountains inFrance, Italy and Spain, and one deepin a mine in the United Kingdom. Theystudy neutrinos, search for dark matterand watch for proton decay.

Ghostly particlesNeutrinos are dif Þ cult to study: theyinteract with matter so rarely. For this

reason underground facilities are goodplaces to study them. Whether lookingfor the rare interactions of neutrinos fromspace, or in a beam from an acceleratoron Earth, deep underground laboratoriesprovide the isolation that will maximisethe chance of seeing something interest-ing. Although we know that neutrinoshave mass, we still do not know whatthat mass is. And although we know that

they oscillate between one kind and an-other, we have yet to understand fullythe oscillation process.

Experiments at underground laborato-ries could also help usÞ nd out whetherneutrinos are their own antiparticles ornot, a question that may be linked to theapparent imbalance between matter andantimatter in the Universe. If neutrinosare their own antiparticles, then certainnuclei should decay by emitting two elec-

trons and no neutrinos in a process calledneutrinoless double beta decay. Withneutrinos or not: the answer has pro-found consequences, because it wouldprovide an answer to the mystery of themissing antimatter. Deep undergroundlaboratories are also used for studies ofneutrinos sent from accelerator laborato-ries far away (see pp 22-23).

Dark matter Dark matter accounts for about 21% ofthe Universe. Ordinary matter adds an-other 4% or so and dark energy accountsfor everything else. Dark energy is large-ly in the realm of cosmology, but dark

Boulby

Canfranc

Gran Sasso

Modane

Europe has four world-class deep

underground laboratories, where experiments are looking for rare phe-nomena that could help us answerquestions about matter instability,antimatter, dark matter and darkenergy.


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matter should be acessible to particlephysics. It could be made of so-far unde-tected particles, relics from the Big Bangthat have been roaming the Universeever since, making their presence knownonly through their gravitational inß u-ence. Whatever they are, the fact that wehave never detected any makes deep un-derground laboratories, with their quietconditions, good places to look.

The Þ rst indication of dark matter camemore than 70 years ago from observa-tions on galaxies and on clusters of galax-ies. For example, close inspection showedthat the speeds at which galaxies movedwithin a cluster was very different fromwhat would be expected if visible matterwere all that was needed to hold the clus-ter together. Later, the phenomenon wasconÞ rmed through studies of the rotationof spiral galaxies. The results suggestedthat the apparently ß at-looking spiralgalaxies must be embedded in an invis-ible spherical halo of dark matter.

Cosmologists and particle physicistshave begun to move towards the sameconclusion: dark matter must be made ofthings that are massive but undetectable,the so-called weakly interacting massiveparticles, or WIMPs. In particle phys-

ics, studies of the fundamental particleshave led to the development of super-symmetry, a theory that provides a morecomplete picture of the particle worldthan the Standard Model, and predictsa range of extra particles. Could someof these extra particles be cosmology’sWIMPs? Over the coming years, re-searchers at underground laboratorieswill work closely with their cousins ataccelerator laboratories toÞ nd out.

At accelerator laboratories, researcherstry to make the new particles and thenobserve their decays. In undergroundlaboratories there are two approaches.One is to search for WIMPs indirectly, by looking for particles such as neutri-nos that would emerge from WIMP an-nihilations in high-density places like theSun. The other is to look for signals that aWIMP has slammed into a nucleus insidea sensitive detector. Because WIMPs leada sort of double existence, mixed up withour Universe though hardly interactingwith it, these events would be rare: no- body expects to detect more than a fewevents per year in the most ambitious de-tector currently conceivable.

The big pictureCould all of Nature’s seemingly differ-ent forces be manifestations of the samething? One of the ultimate goals of parti-cle physics is toÞ nd out, and a big step onthe way would be to see a proton decay.Protons are the most stable of all compos-ite particles, with an average lifetime ofat least 10³³ years: a million billion billiontimes longer than the Universe has so farexisted. But theories that enable Nature’sforces to be uniÞ ed also predict that pro-tons must decay. The only way toÞ nd

out is to observe very large quantities ofprotons, since if they do decay, each yeara few will do so long before their averagelife expectancy. European physicists arepart of the global effort to design largeunderground detectors for this task.

This experiment at Gran Sasso is patiently looking for the phenom-enon of neutrinoless double betadecay, which could help us to un-derstand the apparent absence ofantimatter in the Universe.

At work in the apparently contra-dictory environment of a clean roomwithin a mine. The UK’s Boulbymine hosts a research programmelooking for dark matter.

The Edelweiss experiment in theunderground laboratory at Modanein France searches for particlesknown as WIMPs with detectorsmade from germanium.


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Light sources powered by particle physics

Certain kinds of particle accelerators have energy tThat was a problem, once. But the radiation thafrom curved beams now lights up the invisible intmanufacture and medicine. No wonder Europe’s took a shine to the synchrotron.

Their brilliance, their intensity, their co-herence... scientists swoon over the vir-tues of accelerator-based light sources.These are now among the most importanttools of research, from material scienceto molecular biology, and they began inparticle physics. Accelerators are the ba-sic tools of particle physics, but they are

versatile instruments that can be used inmany ways. Today, more than 60 of themserve as light sources in over 20 countriesall around the world. Light sources area prime example of how today’s funda-mental research provides tomorrow’s ap-plications

The TESLA test facility at theDESY laboratory in Hamburg isa valuable proving ground for a future linear collider. It has also provided the technology for the Eu-ropean X-ray Free Electron Laser

facility at DESY.


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Wide-ranging applicationsCharged particles that travel on curvedpaths at almost the speed of light emita wide spectrum of electromagnetic ra-diation. Accelerator-based light sourcesmake use of this radiation, and the mostuseful wavelength they deliver is that ofinvisible X-rays, around 10 millionths ofa millimetre. That is roughly the size ofan atom and the study of atoms is whatlight sources do best: they serve as super-microscopes that can peer into atomicstructures in materials and biologicalcells.

The results are new and fundamental in-sights with a remarkable range of appli-cations in industry and medicine. Lightsource results contribute to the develop-ment of computer chips, catalysts andLED-screens. They bring about advancesin welding seams, bone replacementsand anti-viral medication, to name but afew examples.

Rooted in physicsLight sources wereÞ rst developed in the1960s at particle accelerator laboratories.The researchers exploited a phenomenonthat is a nuisance for particle physics

Undulators like this one at theEuropean Synchrotron RadiationFacility shake photons from elec-tron beams.

Diffraction images like this one from HASYLAB at DESY inHamburg are produced when a protein crystal is irradiated withX-rays from a particle accelerator.Using X-ray diffraction, scientistscan decode the internal structure ofcomplex protein molecules.

itself, but which has become an invalu-able tool for applied science: synchrotronradiation. Synchrotron radiation means

that particles lose energy when they fol-low curved paths: this is exasperating forparticle physicists, who want ever-higherenergies from their accelerated particles.But one man’s poison is another man’smeat, and it soon became clear that thisnuisance radiation could be put to gooduse. TheÞ rst generation of light sourcesconsequently piggybacked on researchprogrammes at particle physics labora-tories.

Since the 1960s, new generations of lightsources have been developed. Many cir-cular accelerators called synchrotronshave been developed speciÞ cally to makethis once-undesirable radiation, andspecialised devices called wigglers andundulators have been devised to shakelight out of the beams in ways that canserve drug designers or materials tech-nologists. Today, many third generationlight sources are in operation around theworld, but particle physics has not sim-ply taken a back seat.

Installing a sample on a proteincrystallography beamline at theSwiss Light Source.

The fourth generationA fourth generation of light sources is justaround the corner. These will be a radicaldeparture from theÞ rst three genera-tions’ sources, and once again they haveemerged directly from contemporaryparticle accelerator technology. Fourthgeneration light sources go by the name

of free-electron lasers, or FELs, and theyare based on linear electron acceleratorscurrently under development for thenext frontier in particle physics. FELsare poised to open a whole new windowonto the nano-world. Their pulsed laser-like beams even make it possible toÞ lmdynamic processes on an atomic level.Research on the world’sÞ rst X-ray free-electron laser, XFEL, started at the DESYlaboratory in 2005. This 300-metre deviceis a prototype for a 3-kilometre EuropeanXFEL facility due to start up in 2013.


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Applications in medicine

Particle and nuclear physics have begun to pmedical treatment as well as basic research. developed to explore the Universe could also intractable tumours. And detectors fashionewitness subatomic mayhem have begun to help map the human metabolism.

A section through the head of the Þrst patient to undergo hadron therapyat the GSI laboratory in Darmstadt.It is overlaid with the physical dosedistribution for a proton beam thatcomes from the right. Critical struc-tures like the brain stem, shown bya green line, are largely untouchedby the beam. The GSI facility is inregular use to treat cancer, and hasinspired a hospital-based facility inHeidelberg.


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Crystals like these, developed bythe Crystal Clear Collaboration, arebeing used in experiments at theLHC. Similar crystals from a previous generation of experiments have foundapplication in medical diagnostictechniques such as PET.

High-quality detector, accelerator, and beam technologies – the tools of particlephysics - are being deployed to create better diagnostic techniques in medicineand to provide new forms of radiationtreatment of disease.

DiagnosisThe detectors developed for particlephysics must spot subatomic particles

that survive for tiny fractions of a second:so they provide precision, sensitivity andhigh-speed response. These attributesare valuable in medicine, where there isa demand for accurate, fast diagnosticimaging that uses as little radiation aspossible. There are now semiconductordetectors under development that willdetect single X-rays or photons and pro-vide enhanced contrast. This could mean better X-ray images for the doctor as wellas a lower X-ray dose for the patient.

Emission tomography is an increasinglyimportant method for imaging in bothdiagnosis and treatment. The patienttakes a dose of a radioactive tracer, andthe radiographer tracks its distributionthrough the body. The main techniquesare PET (positron emission tomogra-phy) and SPECT (single photon emis-sion computed tomography). In each, anarray of detectors senses the radiationemitted as the tracer arrives at its targetwithin the patient. SPECT uses tracersthat emit gamma-rays, while in PET thetracer emits positrons, which annihilatewith electrons in the surrounding atomsto produce back-to-back pairs of gammarays.

Detectors developed for particle phys-ics are now being applied to improve theperformance of both techniques. In tra-ditional SPECT, for example, few of theemitted gamma rays are really observed,as they mustÞ rst pass through tiny holesin lead collimators to deÞ ne their direc-tion before detection. Silicon detectorscould be designed to recognise the direc-tion of the gamma rays without the needfor collimation: the pay-off would bemore precise information and surer diag-nosis from a smaller dose of tracer.

TherapyEvery day, in radiation treatment centresaround the globe, thousands of patientsare treated with X-rays produced at lin-ear electron accelerators. Now in manycountries another kind of treatment,known as hadron therapy, is on the way.Hadron therapy makes use of stronglyinteracting particles – hadrons – that de-posit most of their energy close to the endof their range in matter. This means thatmost of the radiation gets all the way toa tumour inside the body, while causingmuch less damage to the healthy tissuearound it than, for example, with X-rays.

The particles that could kill off cancercells are protons and carbon ions – nucleiof carbon atoms. Proton therapy is wellsuited to cases in which a tumour is closeto organs at risk. Carbon ion beams, be-ing much more ionizing, can control tu-mours that are resistant both to X-raysand to protons. By the beginning of 2006,around 45 000 patients had been treat-ed with proton beams and some 2500

with carbon ions at centres around theworld.

Hadron therapy requires a circular ac-celerator to provide the beams and large‘gantries’ to deliver the radiation to pa-tients. These complex high-tech systemsrun effectively and continuously becauseof the experience developed for under-standing the subatomic world throughresearch in nuclear and particle physics.Proton-therapy facilities exist in France,

Germany, Italy, Russia, Sweden, Swit-zerland and the UK. Recent initiatives inaccelerator laboratories in Europe haveled to important steps in the develop-ment and construction of dual centresfor protons and carbon ions in hospi-tals. The Heidelberg Ion Therapy (HIT)Centre designed by the GSI laboratoryin Darmstadt was approved in 2001 andthe Þ rst treatment will take place in 2007.Construction of the Italian national cen-tre CNAO started in 2002 and will beÞ nished in 2007. At PSI in Switzerlandthere is a new superconducting cyclotronfor proton therapy and related research.Further centres are under construction orplanned in Wiener Neustadt in Austria,Lyon in France and Uppsala in Sweden.


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What is the Grid?The Grid is a service for sharing com-puter power and data storage capacityin a geographically distributed way. Likethe Web, the Grid is a service that runson the Internet. Unlike the Web, there isno uniform standard or protocol for theGrid today; rather there are many differ-ent Grids for different applications. SomeGrids link resources on a local or nationalscale. ScientiÞ c Grids, such as the LHCComputing Grid (LCG) led by CERN,link together major computing centres.

How does the Grid work?The essential ingredient is the ‘middle-ware’, which is software that allows theuser to access remote data and process-ing power in a simple, reliable and ef Þ -cient way. The middleware also managessecurity, monitoring, accounting and oth-er features of the Grid. The underlyingphysical infrastructure of the Grid con-sists of clusters of PCs, supercomputers,tape and disk storage systems, as well asthe networks that link them together.

What does the Grid do forparticle physics?When fully operational, the LHC ex-periments will each produce roughly

The Grid links computing and datastorage resources from around theworld into a seamless whole.

Testing the Grid. This map shows the path of real data ßowing out from CERNto a few selected grid nodes during an LHC computing grid data challenge.

1 million Gigabytes (some 100 thousandDVDs) of data annually. Thousands ofscientists can only access and analyse somuch data if they unite the computingresources of hundreds of research insti-tutes around the globe into a single com-puting Grid.

Will the Grid replace super-computers?Grids like LCG are good at solving prob-lems that can be divided into relativelysmall independent tasks, and can thusrely on clusters of PCs, where each pro-cessor works alone. But some scientiÞ cproblems require frequent high-speedcommunication between processors, andtherefore need a supercomputer wherehundreds or thousands of processors areable to work together ef Þ ciently.

An example is the notoriously intrac-table problem of quantum chromody-namics (QCD), the fundamental theoryof the strong force that binds protonsand neutrons. Supercomputers involvingthousands of processors are beginning to

reveal what the theory predicts. It is evenpossible to join geographically dispersedsupercomputers into a Grid. So super-computers and Grids are really comple-mentary approaches.

How will the Grid affect youAround 2,000 computers in 11 Britishlaboratories linked up in a Grid projectrecently to simulate 300,000 compoundsand electronically sample them for prop-

erties that might help combat the avianß u virus H5N1. It was an exercise thatmight have tied up one computer for100 years. The Grid is already changingthe way science is done and is starting tohave an impact in the commercial andÞ -nancial worlds.

CERN also leads the world’s largestmultiscience Grid project, Enabling Gridsfor E-sciencE, which is supported by theEuropean Union. Its impact on a numberof computer and data-intensiveÞ elds in-cludes:•speeding up the search for new drugsand facilitating computer-based medicaldiagnostics•simplifying disaster relief by sharingdata globally and accelerating forecast-ing simulations ofß oods and volcanicactivity•helping geophysical analysis for oil ex-ploration, as well as enabling the designof future fusion reactors•supporting distributed search and cata-loguing for electronic libraries•running complex Þ nancial simulationprograms.


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RAL

DAPNIA

DESY

LNF

LNGS

CERN

Particle physics in Europe

PSI

LAL


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DAPNIAThe DAPNIA laboratory is dedicated toresearch into the fundamental laws of theUniverse. Its research portfolio includesastrophysics, particle physics and nucle-ar physics.

DESYThe German Electron Synchrotron(DESY) is one of the world’s leading ac-celerator centres. It is a national researchcentre with locations in Hamburg andZeuthen, near Berlin. It is host to theHERA collider, and is an important cen-tre for light source research.

LALThe Linear Accelerator Laboratory (LAL)near Paris has a 50 year tradition at thefrontier of research. Its main area of re-search is particle physics, complemented by a strong engagement with cosmologyand astrophysics.

LNFThe Frascati laboratory (LNF) near Romeis home to DAFNE, a high-intensityelectron-positron collider allowing preci-sion studies to be made.

LNGSThe Gran Sasso laboratory (LNGS) is theworld’s largest deep underground labo-ratory for experimental particle physicsand nuclear astrophysics.

PSIThe Paul Scherrer Institute, home to theSwiss Light Source, is also a base for par-ticle physics.

RALThe Rutherford Appleton Laboratory,operated by the Council for the CentralLaboratory for the Research Councils(CCLRC), is a focus for particle physics.

CERN, the European Organization for Nuclear Research, has its headquartersin Geneva. At present, its Member States are Austria, Belgium, Bulgaria, theCzech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy,Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzer-land and the United Kingdom. India, Israel, Japan, the Russian Federation, theUnited States of America, Turkey, the European Commission and UNESCOhave Observer status.


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TRIUMF

SLAC

BINP, RussiaThe Budker Institute of Nuclear Phys-ics is a major centre for nuclear physicsresearch in Russia. It is also host to theSiberian Synchrotron Radiation Centre.

BNL, USAThe Brookhaven National Laboratory(BNL) is a large, multi-disciplinary re-search centre. It is host to the RHICheavy-ion collider.

CCLRC, UKThe Council for the Central Laboratoryfor the Reseach Councils (CCLRC) oper-ates the Rutherford Appleton and Dares- bury laboratories, which provide a UKfocus for particle physics, accelerator sci-ence and light sources.

CERNThe European Organization for NuclearResearch (CERN) operates the world’slargest particle physics research centre.W and Z particles were discovered atCERN, and the centre is also the birth-place of the World Wide Web. In 2007, itwill start bringing the Large Hadron Col-lider into operation. The LHC will be theworld’s highest energy particle collider.

Cornell, USACornell University is host to the CESRelectron-positron collider, and is an im-portant centre for accelerator R&D.

DAPNIA, FranceThe DAPNIA laboratory is dedicated toresearch into the fundamental laws of theUniverse. Its research portfolio includesastrophysics, particle physics and nucle-ar physics.

DESY, GermanyThe German Electron Synchrotron(DESY) is one of the world’s leading ac-celerator centres. It is a national researchcentre with locations in Hamburg andZeuthen, near Berlin. It is host to theHERA collider, and is an important cen-tre for light source research.

Particle physics in the World

CornellFNAL

Laboratories represented at the Joint ICFA-Laboratory Directors’meeting.

FNAL, USAThe Fermi National Accelerator Labora-tory (FNAL) is the home of the Tevatron,the world’s most powerful particle accel-erator. It is the scene of important discov-eries, including that of the top quark.IHEP, ChinaThe Institute of High Energy Physics(IHEP) is the largest and most compre-hensive fundamental research centre inChina. The major researchÞ elds of IHEPare particle physics, accelerator physicsand their associated technologies and ap-plications.

IHEP, RussiaThe State Research Centre of the Rus-sian Federation Institute for High En-ergy Physics (IHEP), Moscow, is one ofthe leading Russian centres for particlephysics.

JINRBased in Dubna, Russia, the Joint Insti-tute for Nuclear Research (JINR) is anintergovernmental organization foundedin 1956, with currently 18 member states.Its mission is to study the fundamentalproperties of matter.

KEK, Japan Japan’s high energy accelerator researchorganization (KEK) is host to the BELLEexperiment, and is an important centrefor accelerator R&D.

LAL, FranceThe Linear Accelerator Laboratory (LAL)near Paris has a 50 year tradition at thefrontier of research. Its main area of re-search is particle physics, complemented by a strong engagement with cosmologyand astrophysics.

LNF, ItalyThe Frascati laboratory (LNF) near Romeis home to DAFNE, a high-intensity elec-tron-positron collider allowing precisionstudies to be made.


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JINR

KEK

BINP

BNL

CCLRC

CERN

DAPNIA

DESY

IHEP

IHEP

LAL

LNF

SLAC, USAThe Stanford Linear Accelerator Cen-ter (SLAC) is the host to the BaBar ex-periment, and is an important centre forlight-source science.

TRIUMF, CanadaThe TRIUMF laboratory in Vancouver isCanada’s national laboratory for particleand nuclear physics.


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The European strategy for particle physics36

The European strategy for particle physics

Particle physics stands on the threshold of a new and exciting era oThe next generation of experiments will explore new domains and pstructure of space-time. They will measure the properties of the elemstituents of matter and their interactions with unprecedented accuracwill uncover new phenomena such as the Higgs boson or new forms ostanding puzzles such as the origin of mass, the matter-antimatter athe Universe and the mysterious dark matter and energy that permemos will soon beneÞt from the insights that new measurements will bring.the results will have a profound impact on the way we see our UniveEuropean particle physics should thoroughly exploit its current exciting and div programme. It should position itself to stand ready to address the chwill emerge from exploration of the new frontier, and it should particincreasingly global adventure.

General issues1. European particle physics is founded on strong national

institutes, universities and laboratories and the CERNOrganization; Europe should maintain and strengthen itscentral position in particle physics.

2. Increased globalization, concentration and scale of particlephysics make a well coordinated strategy in Europeparamount;this strategy will be de Þned and updated by CERNCouncil as outlined below.

Scienti Þ c activities3. The LHC will be the energy frontier machine for the

foreseeable future, maintaining European leadership in theÞ eld; the highest priority is to fully exploit the physics potentialof the LHC, resources for completion of the initial programmehave to be secured such that machine and experiments can operateoptimally at their design performance. A subsequent majorluminosity upgrade (SLHC), motivated by physics resultsand operation experience, will be enabled by focussed R&D;to this end, R&D for machine and detectors has to be vigorously pursued now and centrally organized towards a luminosityupgrade by around 2015.

4. In order to be in the position to push the energy andluminosity frontier even further it is vital to strengthenthe advanced accelerator R&D programme;a coordinated programme should be intensi Þed, to develop the CLIC technologyand high performance magnets for future accelerators, and to playa signi Þcant role in the study and development of a high-intensityneutrino facility.

5. It is fundamental to complement the results of the LHC withmeasurements at a linear collider. In the energy range of0.5 to 1 TeV, the ILC, based on superconducting technology,will provide a unique scientiÞ c opportunity at the precisionfrontier; there should be a strong well-coordinated European

activity, including CERN, through the Global Design Effort, forits design and technical preparation towards the constructiondecision, to be ready for a new assessment by Council around2010.

6. Studies of the scientiÞ c case for future neutrino facilitiesand the R&D into associated technologies are required to be in a position to deÞ ne the optimal neutrino programme based on the information available in around 2012;Councilwill play an active role in promoting a coordinated European participation in a global neutrino programme.

7. A range of very important non-accelerator experimentstake place at the overlap between particle and astroparticlephysics exploring otherwise inaccessible phenomena;Council will seek to work with ApPEC to develop a coordinatedstrategy in these areas of mutual interest.


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The European strategy for particle physics37

8. Flavour physics and precision measurements at the high-luminosity frontier at lower energies complement ourunderstanding of particle physics and allow for a moreaccurate interpretation of the results at the high-energyfrontier;these should be led by national or regional collaborations,and the participation of European laboratories and institutesshould be promoted.

9. A variety of important research lines are at the interface between particle and nuclear physics requiring dedicatedexperiments;Council will seek to work with NuPECC in areasof mutual interest, and maintain the capability to perform Þxedtarget experiments at CERN.

10. European theoretical physics has played a crucial rolein shaping and consolidating the Standard Model andin formulating possible scenarios for future discoveries.Strong theoretical research and close collaboration withexperimentalists are essential to the advancement of particlephysics and to take full advantage of experimental progress;the forthcoming LHC results will open new opportunities for

theoretical developments, and create new needs for theoreticalcalculations, which should be widely supported.

Organizational issues11. There is a fundamental need for an ongoing process to

deÞ ne and update the European strategy for particlephysics;Council, under Article II-2(b) of the CERN Convention,shall assume this responsibility, acting as a council for European particle physics, holding a special session at least once each year for this purpose. Council will de Þne and update the strategybased on proposals and observations from a dedicated scienti Þcbody that it shall establish for this purpose.

12. Future major facilities in Europe and elsewhere requirecollaborations on a global scale;Council, drawing on theEuropean experience in the successful construction and operationof large-scale facilities, will prepare a framework for Europeto engage with the other regions of the world with the goal ofoptimizing the particle physics output through the best shareduse of resources while maintaining European capabilities.

13. Through its programmes, the European Union establishesin a broad sense the European Research Area with Europeanparticle physics having its own established structures andorganizations;there is a need to strengthen this relationship forcommunicating issues related to the strategy.

14. Particle physicists in the non-Member States beneÞ t from,and add to, the research programme funded by the CERNMember States;Council will establish how the non-MemberStates should be involved in de Þning the strategy.

Complementary issues15. Fundamental physics impacts both scientiÞ c and

philosophical thinking, inß uencing the way we perceive theuniverse and our role in it. It is an integral part of particlephysics research to share the wonders of our discoverieswith the public and the youth in particular. Outreachshould be implemented with adequate resources from thestart of any major project;Council will establish a networkof closely cooperating professional communication of Þcers fromeach Member state, which would incorporate existing activities, propose, implement and monitor a European particle physicscommunication and education strategy, and report on a regularbasis to Council.

16. Technology developed for nuclear and particle physicsresearch has made and is making a lasting impact on

society in areas such as material sciences and biology(e.g. synchrotron radiation facilities), communication andinformation technology (e.g. the web and grid computing),health (e.g. the PET scanner and hadron therapy facilities);to further promote the impact of the spin-offs of particle physicsresearch, the relevant technology transfer representatives atCERN and in Member states should create a technology transfer forum to analyse the keys to the success in technology transfer projects in general, make proposals for improving its effectiveness, promoting knowledge transfer through mobility of scientists andengineers between industry and research.

17. The technical advances necessary for particle physics both beneÞ t from, and stimulate, the technological competencesavailable in European industry;Council will consolidate andreinforce this connection, by ensuring that future engagement withindustry takes account of current best practices, and continuously pro Þts from the accumulated experience.

Unanimously approved by the CERNCouncil at the special Session held inLisbon on 14 July 2006

CERN/2685


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ContributorsU. Amaldi

A. BlondelA. CeccucciE. Coccia J. Ellis J. EngelenP. FolkertsB. FosterM. ManganoG. Wormser

Editorial BoardM. Aguilar

T. ÅkessonD. BarneyK. PeachG. HertenE. IarocciE. OsnesM. Spiro

Thanks to B. Beauseroy

Editors J. GilliesC. SuttonP. BarrattA. Del Rosso ViteF. GreyP. Royole-DegieuxB. Warmbein

Thanks to T. Radford

Graphic DesignF. Marcastel

Illustration creditsAll copyright CERN except:

p6: A.-P. Olivierp7: left, Peter Ginter; right, SLACp9: right, Sergio Cittolinp10: NASA/WMAP Science Teamp11: left, NASAp12: left, DESY Hamburg; middle, Fermi-lab Visual Media Servicesp13: left, DESY/Physics PhotographicUnit, Oxford Universityp18: DESY Zeuthenp19: left, SLAC; middle, DESY Hamburgp20: INFNp21: left, Peter Ginter/SLAC; middle,KEK; right, NASAp22: Stefano Carrara/Courtesy “Le Sci-enze”p23: left, Stephanie Yang/Oxford Univer-sity; right; Kamioka Observatory, ICRR,Tokyo Universityp24: clockwise from left: Universidad deZaragoza; courtesy UK Dark Matter col-laboration; LSM; INFN/LNGSp25: left, INFN/LNGS; middle, LSM;right, courtesy UK Dark Matter collabo-ration.

p26: DESY Hamburgp27: left, Peter Ginter/ESRF; middle,Swiss Light Source/PSI; right, MaxPlanck Working Groups, Hamburgp28: GSIp29: Antonio Sabap32: clockwise from bottom left: CNRS/LAL; CEA/J.J. Bigot; CCLRC; DESYHamburg; PSI; INFN/LNGS; INFN/LNFp34–35: clockwise from top left: Pe-ter Ginter; Cornell/Wilson Labora-tory; CCLRC; DESY Hamburg; IHEP,Russia; JINR; BINP; KEK; IHEP, Beijing;INFN/LNF; CEA/J.J. Bigot; CNRS/LAL;Brookhaven National Laboratory; PeterGinter; TRIUMF.

Published 24 July 2006


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Documents

Strategy Brochure CERN