CMSATLAS探测器对比

K.JakobsVorlesungPhysikanHadron-Collidern,Freiburg,SS20112.5ImportantdifferencesbetweentheATLASandCMSdetectorsTheATLASdetectorconceptCMSDetectorConceptTrackerCalorimeterCoilMuonDetectorandironreturnyokeCMSMUONBARREL
CALORIMETERS

PixelsSiliconMicrostrips
210m2ofsiliconsensors
9.6Mchannels
ECAL
76kscintillatingPbWO4crystals


CathodeStripChambers(CSC)
ResistivePlateChambers(RPC)
DriftTube

Chambers(DT)
ResistivePlate

Chambers(RPC)
SuperconductingCoil,4Tesla
IRONYOKETRACKER
MUONENDCAPS
HCAL
Plasticscintillator/brasssandwich


Totalweight12500tOveralldiameter15mOveralllength21.6mHowhugeareATLASandCMS?Sizeofdetectors:-Volume:20000m3forATLAS-Weight:12500tonsforCMS-66to80millionpixelreadoutchannelsnearvertex-200m2ofactivesiliconforCMStracker-175000readoutchannelsforATLASLArEMcalorimeter-1millionchannelsand10000m2areaofmuonchambers-Veryselectivetrigger/DAQsystem-Large-scaleofflinesoftwareandworldwidecomputing(GRID)Time-scale:Morethan25yearsfromfirstconceptualstudies(Lausanne1984)tosolidphysicsresultsin2011confirmingthatLHChastakenoverthehigh-energyfrontierfromtheTevatronATLASCMSMagneticfield2Tsolenoid+toroid:0.5T(barrel),1T(endcap)4Tsolenoid+returnyokeTrackerSiliconpixelsandstrips+transitionradiationtracker/pT510-4pT+0.01Siliconpixelsandstrips(fullsilicontracker)/pT1.510-4pT+0.005EMcalorimeterLiquidargon+Pbabsorbers/E10%/
E+0.007PbWO4crystals/E3%/
E+0.003HadroniccalorimeterFe+scintillator/Cu+LAr(10)/E50%/
E+0.03GeVBrass+scintillator(7+catcher)/E100%/
E+0.05GeVMuon/pT2%@50GeVto10%@1TeV(InnerTracker+muonsystem)/pT1%@50GeVto10%@1TeV(InnerTracker+muonsystem)TriggerL1+HLT(L2+EF)L1+HLT(L2+L3)ImportantdifferencesI:•
InordertomaximizethesensitivityforH


decays,theexperimentsneedtohaveanexcellente/
identificationandresolution•
CMS:hasoptedforahighresolutionPbWO4crystalcalorimeter-higherintrinsicresolution•
ATLAS:Liquidargoncalorimeter-highgranularityandlongitudinallysegmentation(bettere/
ID)-electricalsignals,highstabilityincalibration&radiationresistantBackCellMiddleCellStripCellATLAS/CMS:e/
resolutionsPhotonsat100GeVATLAS:1-1.5%energyresol.(all
)CMS:0.8%energyresol.(
~70%)Electronsat50GeVATLAS:1.3-2.3%energyresol.(useEMcaloonly)CMS:~2.0%energyresol.(combineEMcaloandtracker)•
Activesensorsandmechanicsaccounteachonlyfor~10%ofmaterialbudget•
Needtobring70kWpowerintotrackerandtoremovesimilaramountofheat•
Verydistributedsetofheatsourcesandpower-hungryelectronicsinsidevolume:thishasledtocomplexlayoutofservices,mostofwhichwerenotatallunderstoodatthetimeoftheTDRsAmountofmaterialinATLASandCMSinnertrackersLEPdetectors
Weight:4.5tonsWeight:3.7tonsImportantdifferencesII:•
Innerdetectors/trackerBothusesolenoidalfieldsATLAS:2TeslaCMS:4Tesla•
CMS:fullsiliconstripandpixeldetectors-highresolution,highgranularity•
ATLAS:Silicon(stripsandpixels)+TransitionRadiationTracker-highgranularityandresolutionclosetointeractionregion-“continuous”trackingatlargeradiiK.JakobsVorlesungPhysikanHadron-Collidern,Freiburg,SS2011-PerformanceofCMStrackerisundoubtedlysuperiortothatofATLASintermsofmomentumresolution.-Vertexingandb-taggingperformancesaresimilar.-However,impactofmaterialandB-fieldalreadyvisibleonefficiencies.MainperformancecharacteristicsoftheATLASandCMStrackersImportantdifferencesIII:•
Coil/Hadroncalorimeters•
CMS:electromagneticcalorimeterandpartofthehadroniccalorimeter(7)insidethesolenoidalcoil+tailcatcher,returnyokegoodfore/
resolutionbadforjetresolution•
ATLAS:calorimetryoutsidecoil11

ATLAS
HadronicabsorptionlengthofthecalorimetersK.JakobsVorlesungPhysikanHadron-Collidern,Freiburg,SS201111

CMS
K.JakobsVorlesungPhysikanHadron-Collidern,Freiburg,SS2011BiggestdifferenceinperformanceperhapsforhadroniccalorimetryETmissatET=2000GeVATLAS:~20GeVCMS:~40GeVThismaybeimportantforhighmassH/A

Jetsat1000GeVATLAS:~2%energyresolutionCMS:~5%energyresolution,Butexpectsizableimprovementusingtracks(especiallyatlowerE)ImportantdifferencesIV:•
Muonspectrometer•
ATLAS:independentmuonspectrometer;
excellentstand-alonecapabilities•
CMS:superiorcombinedmomentumresolutioninthecentralregion;limitedstand-aloneresolutionandtriggercapabilities(multiplescatteringintheiron)CMSmuonperformancedrivenbytracker:betterthanATLASat
~0;ATLASmuonstand-aloneperformanceexcellentoverwhole
rangeHowtoSelectInterestingEvents?
Bunchcrossingrate:40MHz,~20interactionsperBX(109evts/s)
canonlyrecord~200event/s(1.5MBeach),still300MB/sdatarate
NeedhighlyefficientandhighlyselectiveTRIGGER
raweventdata(70TB/s)arestoredinpipelineuntiltriggerdecision
ATLAStriggerhas3levels(CMSsimilarwith2levels)
Level-1:hardware,~3
sdecisiontime,40MHz100kHz
Level-2:software,~40msdecisiontime,100kHz2kHz
Level-3:software,~4sdecisiontime,2kHz200HztrashsavePIPELINENOYEStrigger109evts/s102evts/sDetectorLHCdatahandling,GRIDcomputingTriggersystemselects~200“collisions”persec.LHCdatavolumeperyear:10-15Petabytes=10-15
1015ByteConcorde(15Km)Balloon(30Km)CDstackwith1yearLHCdata!(~20Km)Mt.Blanc(4.8Km)LCG/EGEE/OSGe-ScienceGridisinproduction:World-wideCoverageOver200sites20’000CPUsMult