ATLASATLAS experimentexperiment atat thethe CERNCERN LargeLarge HadronHadron ColliderCollider
Peter Watkins, Head of Particle Physics Group, University of Birmingham, UK [email protected] Large Hadron Collider (LHC)
PointPoint 11 activitiesactivities andand perspectivesperspectives
MarzioMarzio NessiNessi
ATLASATLAS plenaryplenary d OutlineOutline ofof talktalk
•• BuildingBuilding blocksblocks ofof thethe universeuniverse •• WhyWhy dodo experimentsexperiments atat thethe LHCLHC ?? •• LHC,LHC, ATLASATLAS andand collaborationcollaboration •• SearchingSearching forfor aa newnew particleparticle •• RecentRecent LHCLHC newsnews
AcknowledgementsAcknowledgements –– ManyMany slidesslides fromfrom LHCLHC colleaguescolleagues 4 The very small
nucleus proton neutron up quark down quark
10-14 m10-15 m< 10-18 m 10-10 m (thickness of human hair ~ 10-5 m) FundamentalFundamental ForcesForces All forces are carried by particles !
Gravity – solar system, galaxies …- extremely weak force
Electromagnetic – atoms, electricity ….. - carried by photons
Weak force – beta decay and how stars generate energy
- carried by massive W and Z bosons
Strong – binds quarks inside proton carried by gluons Higgs boson? TheThe HiggsHiggs BosonBoson
One key objective of the LHC is to understand the origin of mass – is it due to a universal Higgs field? (A Higgs field everywhere with the Higgs boson as the force carrier?).
Massless particles are not impeded by the Higgs field and, thus, travel at the speed of light. Analogy: Downhill skier experiences no drag by the snow field.
Light particles interact weakly with the Higgs field and travel slower. Analogy: Snowshoes on the top of the snow field experience some drag.
Heavy particles interact strongly with the Higgs field and travel very slowly. Analogy: Wading through the snow field is a big drag! We call this drag “Mass”. WhatWhat elseelse isis outout there?there?
•• VariousVarious ideasideas consideredconsidered…… •• DarkDark mattermatter • •• ExtraExtra dimensionsdimensions ofof spacespace
• Suggested by superstring theory •• MicroscopicMicroscopic blackblack holesholes
TheThe LHCLHC experimentsexperiments cancan looklook forfor allall ofof thesethese..
AlsoAlso sensitivesensitive toto somethingsomething “completely“completely different”different” TheThe LargeLarge HadronHadron ColliderCollider (LHC)(LHC)
Mont Blanc The LHC is a 27km accelerator that collides counter-rotating beams of protons of up to 7 TeV. Geneva (Tev = million million eV)
Airport Energy densities similar to billionths of a second after the big-bang will be recreated at collision points
CERN laboratory on Swiss – French border BuildingBuilding thethe LHCLHC In the main ring: 1746 superconducting magnets … including 1232 15m SC dipoles … weighing 27 tonnes each … producing 8.36 Tesla … and running at –270c … needs 700,000 litres liquid He
… and 12 million litres liquid N2 TheThe fastestfastest racetrackracetrack onon thethe planetplanet The protons will reach 99.9999991% speed of light, and go round the 27km ring 11,000 times per second CollisionCollision pointspoints
At four places the beams intersect HotHot spotsspots tootoo !!
When the two beams of protons collide, they will generate temperatures 1000 million times hotter than the heart of the sun, but in a minuscule space ATLASATLAS DetectorDetector 7,000 tonnes 42m long 22m wide 22m high (About the height of a 5 storey building) 2,800 Physicists 169 Institutes 37 Countries
ElectromagneticElectromagnetic CalorimeterCalorimeter AA basicbasic calorimetercalorimeter Basics
The past
Challenges
Where to start?
Detector Design Tracker Calorimetry Particle ID
LHC detectors
“Events”
Final thoughts
Total # of particles is proportional to energy of incoming particle Active detector slices produce a signal proportional to the number of charged particles traversing MuonMuon DetectorsDetectors
E2 = p2c2+ m2c4
DiscoveringDiscovering aa newnew particleparticle TheThe collisioncollision raterate challengechallenge •• ProtonProton bunchesbunches collidecollide 4040 millionmillion timestimes aa secondsecond •• ~25~25 protonproton--protonproton collisionscollisions occuroccur eacheach timetime •• 10000000001000000000 collisionscollisions perper secsec –– 200200 perper secondsecond limitlimit forfor recordingrecording •• SelectSelect thethe mostmost ‘‘interestinginteresting’’ collisionscollisions inin fewfew microsecondsmicroseconds SearchingSearching forfor RareRare PhenomenaPhenomena
Number of collisions All interactions 9 orders of magnitude The HIGGS
Collision energy
50 magnets repaired 3 km of beam pipe cleaned LHCLHC statusstatus andand plansplans
•• LargeLarge HadronHadron ColliderCollider restartedrestarted inin NovNov 20092009 andand isis workingworking wellwell
•• WorldWorld recordrecord waswas setset forfor collisioncollision energyenergy inin DecemberDecember 20092009 •• OnOn MarchMarch 3030th 20102010 thethe collisioncollision energyenergy waswas increasedincreased toto 77 TeVTeV •• SomeSome earlyearly measurementsmeasurements alreadyalready publishedpublished •• SearchSearch forfor HiggsHiggs bosonboson needsneeds moremore collisionscollisions ZZ bosonboson candidatecandidate SummarySummary
•• ManyMany peoplepeople areare interestedinterested inin thethe LHCLHC andand thethe keykey ideasideas areare widelywidely accessibleaccessible •• TheThe searchessearches forfor newnew particlesparticles areare onlyonly justjust beginningbeginning andand willwill lastlast forfor aa decadedecade
•• WeWe workwork onon sharingsharing thethe excitementexcitement ofof thethe projectproject withwith thethe widestwidest possiblepossible audienceaudience •• WeWe needneed youryour helphelp toto dodo thisthis toto anan eveneven widerwider audience!audience! Thanks for listening