M. Schott (CERN) Page 1 Status of the ATLAS Experiment Epiphany 2011 Matthias Schott (CERN) On behalf of the ATLAS Collaboration Content ATLAS Detector

M. Schott (CERN) Page 1

Status of the ATLAS Experiment

Epiphany 2011Matthias Schott (CERN)

On behalf of the ATLAS Collaboration

Content• ATLAS Detector and Data Taking• Detector Performance• Highlights of the 2010 Physics Results• Prospects and Conclusion


Content

Summary• Overview of the ATLAS Collaboration and the ATLAS Detector• Brief discussion on the data taking in 2010 and triggering• Data processing



March 2010: ATLAS Control Room May 2010: First Z Candidate

November 2010: Pb-Pb collision

The most exciting LHC year so far: 2010

July 2010: First Top Candidate


The ATLAS Collaboration3000 scientists3000 scientists

174 institutes174 institutes

38 countries38 countries

all continentsall continents

More than 1000 PhD studentsMore than 1000 PhD students

More than 1.200 working meetings More than 1.200 working meetings each montheach month

Increased by factor of 3 Increased by factor of 3 compared to pre-data periodcompared to pre-data period


The ATLAS DetectorInner DetectorInner Detector

|η|<2.5, solenoid |η|<2.5, solenoid B=2TB=2T

Si Pixels, Si Pixels, Si strips, TRTSi strips, TRT

Tracking and Tracking and vertexingvertexing

e/π separation e/π separation

Resolution: Resolution: σ/pσ/pTT~3.8x10~3.8x10-4-4ppTT[GeV][GeV]

0.015⊕0.015⊕

EM calorimeterEM calorimeter|η|<3.2|η|<3.2

LAr/Pb accordion LAr/Pb accordion structure e/γ trigger, id + structure e/γ trigger, id + measurementmeasurement

E-resolution: σ/E ~ E-resolution: σ/E ~ 10%/√E10%/√E

HAD calorimeterHAD calorimeter|η|<3.2 (Forward Calo. |η|<4.8)|η|<3.2 (Forward Calo. |η|<4.8)

Scint./Fe tiles in the central, Scint./Fe tiles in the central, W(Cu)/LAr in fwd region W(Cu)/LAr in fwd region

Trigger, jets + missing EtTrigger, jets + missing Et

E-resolution: σ/E ~ 50%/√E ⊕E-resolution: σ/E ~ 50%/√E ⊕0.030.03

Muon SpectrometerMuon Spectrometer|η|<2.7|η|<2.7

Toroid B-FieldToroid B-Field

Muon Momentum Muon Momentum resolution < 10% up resolution < 10% up to ~ 1 TeVto ~ 1 TeV


Data Taking (1/2)48.1pb48.1pb-1-1 delivered integrated delivered integrated luminosityluminosity

Many thanks to a fantastic LHC teamMany thanks to a fantastic LHC team

Luminosity detectors calibrated with Luminosity detectors calibrated with van der Meer scansvan der Meer scans

Luminosity known today to 11% (error Luminosity known today to 11% (error dominated by knowledge of beam dominated by knowledge of beam currents)currents)

Will go down significantly after Will go down significantly after analysis of last van der Meer scan (done analysis of last van der Meer scan (done on 1st Oct 2010)on 1st Oct 2010)

ALFA detector in place for 2011ALFA detector in place for 2011

elastic scattering in Coulomb-Nuclear elastic scattering in Coulomb-Nuclear interference regioninterference region

Overall ATLAS Data-taking Overall ATLAS Data-taking efficiency: 93.6%efficiency: 93.6%


Data Taking (2/2)For all systems > 97% of For all systems > 97% of channels are operationalchannels are operational

in addition have built-in in addition have built-in redundancy in most systemsredundancy in most systems

Total fraction of good quality Total fraction of good quality datadata

Constantly >94%Constantly >94%

Typical LHC FillTypical LHC FillFew minutes needed for Few minutes needed for

tracking detectors (silicon and tracking detectors (silicon and muons) to ramp HV when LHC muons) to ramp HV when LHC declares stable beamsdeclares stable beams

Short ‘dips’ in recorded rate: Short ‘dips’ in recorded rate: recover “on-the-fly” modules which recover “on-the-fly” modules which would otherwise give a BUSY would otherwise give a BUSY blocking further eventsblocking further events


Trigger (1/2)Level-1:Level-1:

Implemented in hardwareImplemented in hardware

Muon + Calo basedMuon + Calo based

coarse granularitycoarse granularity

e/γ, μ, π, τ, jet candidate selectione/γ, μ, π, τ, jet candidate selection

Define regions of interest (ROIs)Define regions of interest (ROIs)

Level-2: Level-2: Implemented in softwareImplemented in software

Seeded by level-1 ROIs, full granularity Seeded by level-1 ROIs, full granularity

Inner Detector – Calo track matchingInner Detector – Calo track matching

Event Filter:Event Filter:Implemented in softwareImplemented in software

Offline-like algorithms for physics Offline-like algorithms for physics signaturessignatures

Refine LV2 decision Refine LV2 decision

Full event buildingFull event building

Collision rate 40MHz

LV1 accepts up to 75kHz

recorded ~300 Hz


Trigger (2/2)

Trigger configuration infrastructure is Trigger configuration infrastructure is very flexiblevery flexible

Coping very well with rapidly Coping very well with rapidly increasing luminosity by adjusting increasing luminosity by adjusting prescales/menusprescales/menus

~10 different inclusive streams written ~10 different inclusive streams written out during the runout during the run

ChallengesChallengesoptimize sharing of the bandwidth for optimize sharing of the bandwidth for

physicsphysics

Determination of trigger efficiencies in Determination of trigger efficiencies in datadata

Level-1 Muon Trigger efficiency Level-1 Muon Trigger efficiency determined with ‘tag-and-probe’ determined with ‘tag-and-probe’ method on J/Psi candidatesmethod on J/Psi candidates

Combined muon track pT


Data Processing10 GB/s peak rate during data 10 GB/s peak rate during data and MC processingand MC processing

Design was 2GB/sDesign was 2GB/s

Reprocessing of all MC and Reprocessing of all MC and Data during LHC data takingData during LHC data taking

More than 1000 users running More than 1000 users running analysis jobs on the GRIDanalysis jobs on the GRID

Over 1000 different users during Over 1000 different users during past 6 months past 6 months

Millions of jobs are ran every Millions of jobs are ran every week at hundreds of sitesweek at hundreds of sites

Data distribution on the GridData distribution on the GridConstant impressive duty cycle !Constant impressive duty cycle !


Content

Overview• Discussion of the individual sub-detectors of ATLAS along their corresponding

physic objects • Inner Detector• Electrons and Photons• Jets and Missing Energy• Muons



Inner Detector Performance (1/3)

Observed all most Observed all most classic resonancesclassic resonances

KKss, K*, φ, Λ, Ω, Ξ, D, , K*, φ, Λ, Ω, Ξ, D,

D* and J/ΨD* and J/Ψ

Momentum scale Momentum scale known to permil level known to permil level in this rangein this range

Is precisely Is precisely determined via known determined via known resonancesresonances

Resolution as Resolution as expected (dominated by expected (dominated by multiple scattering) multiple scattering)

Good performance Good performance of ATLAS tracker and of ATLAS tracker and tracking/vertexing tracking/vertexing algorithmalgorithm



Today know detector material distribution Today know detector material distribution to better than 10%to better than 10%

Estimation via e.g.Estimation via e.g.Reconstructed secondary vertices due to Reconstructed secondary vertices due to

hadronic interactionshadronic interactions

KKSS mass mass

Use γ-ee conversionUse γ-ee conversion

Already very good, but can be improvedAlready very good, but can be improved

Cooling Pipe + Cable Bundle

Data MC



Particles with higher masses (e.g. Particles with higher masses (e.g. J/Psi, Z) are used to assess J/Psi, Z) are used to assess momentum scale and resolution in momentum scale and resolution in higher energy regimeshigher energy regimes

Example: J/Psi mass resolution Example: J/Psi mass resolution (see plots)(see plots)

Momentum scale known to 1% level Momentum scale known to 1% level up to ~100GeVup to ~100GeV

Offline reconstruction efficiencies Offline reconstruction efficiencies determined e.g. via ‘tag and probe’ determined e.g. via ‘tag and probe’ techniquestechniques

Inner Detector reconstruction Inner Detector reconstruction efficiency for muons above 20GeV efficiency for muons above 20GeV confirmed to be better than 99%confirmed to be better than 99%


Electrons and Photons (1/2)

Main electron selection based on EM Main electron selection based on EM calorimeter:calorimeter:

purely electromagnetic showerpurely electromagnetic shower

shower shapes shower shapes

pointing trackpointing track

Refinement via Inner DetectorRefinement via Inner Detector

Conversion detection via inner most Conversion detection via inner most pixel layerpixel layer

e/πe/π00 separation via TRT (upper left plot) separation via TRT (upper left plot)

Performance as predicted by Monte Carlo Performance as predicted by Monte Carlo simulationssimulations

Impact of ID misalignment on electron Impact of ID misalignment on electron identification before reprocessing identification before reprocessing

Di-Electron Mass Plot based on 5 GeV di-Di-Electron Mass Plot based on 5 GeV di-electron triggerelectron trigger

prescaled in later dataprescaled in later data

produces shoulder at 15 GeVproduces shoulder at 15 GeV


Electrons and Photons (2/2)

Neutral pions provide handle for Neutral pions provide handle for measuring EM energy scale and measuring EM energy scale and response uniformityresponse uniformity

~2% in η~2% in η

<0.7% in φ<0.7% in φ

Good agreement of Z-Boson Good agreement of Z-Boson lineshapelineshape• Autumn reprocessingAutumn reprocessing• Energy Scale uncertainty <1%Energy Scale uncertainty <1%• Aim for electron identification Aim for electron identification

efficiency determination for 2010 efficiency determination for 2010 data: 1%data: 1%


Jets and Missing Energy (1/2)• Jet energy computed from calibrated Jet energy computed from calibrated

topological clusterstopological clusters-ATLAS Jet AlgorithmATLAS Jet Algorithm- anti-KTanti-KT- jet radius R=0.6, 0.4jet radius R=0.6, 0.4

• Jet Energy Scale and ResolutionJet Energy Scale and Resolution-MC studiesMC studies-many years of detailed test beam studies many years of detailed test beam studies -JES from collision dataJES from collision data

- Single hadrons: ESingle hadrons: Ecalocalo/p/ptracker tracker (Use isolated (Use isolated

tracks, determine calorimeter response for tracks, determine calorimeter response for single particles)single particles)

- di-jets events with η inter-calibrationdi-jets events with η inter-calibration- Determination via Z-Boson and top eventsDetermination via Z-Boson and top events

- Aim to reach 1%Aim to reach 1%


Jets and Missing Energy (2/2)• Missing transverse energy is key Missing transverse energy is key

element for many searches and element for many searches and precision measurementsprecision measurements

-Governed by strong performance of the Governed by strong performance of the ATLAS calorimeterATLAS calorimeter

-Sensitive to calorimeter performance Sensitive to calorimeter performance (noise, coherent noise, dead cells, mis-(noise, coherent noise, dead cells, mis-calibrations, cracks, etc.), and cosmics and calibrations, cracks, etc.), and cosmics and beam-related backgroundsbeam-related backgrounds

• Calibrated ECalibrated ETTMissMiss from minimum-bias from minimum-bias

eventsevents-Plots: EPlots: ETT

MissMiss distribution and resolution as distribution and resolution as

measured in a data sample of 15.2 million measured in a data sample of 15.2 million selected minimum bias eventsselected minimum bias events

-No ENo ETTMiss Miss tails after calibrationtails after calibration

• Further calibration channels: Z, W and Further calibration channels: Z, W and top decaystop decays


Muon Systems (1/2)• Good performance of combined Inner Good performance of combined Inner

Detector and Muon Spectrometer Detector and Muon Spectrometer reconstructionreconstruction

-At low pt, Inner detector is dominating overall At low pt, Inner detector is dominating overall muon momentum resolution (~2% resolution, muon momentum resolution (~2% resolution, dominated by multiple scattering)dominated by multiple scattering)

-Transition at ~50GeVTransition at ~50GeV

• Muon Spectrometer Performance can be Muon Spectrometer Performance can be assessed viaassessed via

-Cosmic muonsCosmic muons

-Di-muon decays of known particlesDi-muon decays of known particles- Momentum scale known to 1%Momentum scale known to 1%- Momentum resolution known to rel. 10%Momentum resolution known to rel. 10%- Reconstruction efficiency known to 1-2%Reconstruction efficiency known to 1-2%- Aim is to reach <1%Aim is to reach <1%


Muon Systems (2/2)• Example: First studies of Example: First studies of

Momentum resolution of MS Momentum resolution of MS standalonestandalone

-cosmics: resolution from splitting cosmics: resolution from splitting muon tracks crossing the detector from muon tracks crossing the detector from top to bottomtop to bottom

-muons from collisions: resolution muons from collisions: resolution from comparing MS with ID from comparing MS with ID measurement (ID resolution not measurement (ID resolution not subtracted, negligible at low p)subtracted, negligible at low p)

• Z-Boson resonance appeared Z-Boson resonance appeared wider in data, due towider in data, due to

-Alignment, magnetic field Alignment, magnetic field uncertaintiesuncertainties

-Significant improvement after Significant improvement after reprocessing after new calibrationreprocessing after new calibration


Content

Summary• 15 papers already published based on 2010 collision data

• Many more to come in the next weeks• More than 100 approved results for conferences• Only a very small fraction can be shown in an overview talk

• Jet Physics, W/Z Boson Production, Exclusion Limits on UED, Top Production and Heavy Ions results

• Further reading: https://twiki.cern.ch/twiki/bin/view/AtlasPublic



Jet Physics (1/2)

• Inclusive jet cross-sectionInclusive jet cross-section-~100xTevatron~100xTevatron

• Restricted to 17 nbRestricted to 17 nb-1-1 (no pile-up (no pile-up contamination); contamination);

-ppTT > 60 GeV and |y| < 2.8 > 60 GeV and |y| < 2.8

-Measured jets corrected to particle level Measured jets corrected to particle level using parton-shower MCusing parton-shower MC

• Experimental uncertainties dominated by JES

• 9% in pT and y ranges considered

• 11% from Luminosity not included

• Good data-MC agreement over five orders of magnitude!


Jet Physics (2/2)• Why studying Jet-shapes?

• details of the parton-to-jet fragmentation process

• internal structure is mainly dictated by the emission of multiple gluons from the primary parton, calculable in pQCD

• shape of the jet depends on parton-type that give rise to jets in the final state

• sensitive to non-perturbative fragmentation effects

• Integrated jet shape Ψ(r) is defined as the average fraction of the jet pT that lies inside a cone of radius r concentric with the jet cone

• Excellent agreement with PYTHIA-Perugia2010 tune


W/Z Bosons at ATLAS (1/2)• Why W/Z Bosons production at ATLAS so important?Why W/Z Bosons production at ATLAS so important?

- Fundamental milestones in the “rediscovery”of the Standard ModelFundamental milestones in the “rediscovery”of the Standard Model- Powerful tools to constrain PDFs and test perturbative QCDPowerful tools to constrain PDFs and test perturbative QCD- Z leptonic decay is gold-plated process to calibrate the detector to the Z leptonic decay is gold-plated process to calibrate the detector to the ultimate precisionultimate precision- dominant backgrounds to searches for New Physicsdominant backgrounds to searches for New Physics

• October 2010: First measurement of the W/Z boson production October 2010: First measurement of the W/Z boson production cross-section at 7TeVcross-section at 7TeV- Already dominated by Luminosity UncertaintyAlready dominated by Luminosity Uncertainty- Excellent agreement with theoretical predictionsExcellent agreement with theoretical predictions

• See more details in Pawel’s talkSee more details in Pawel’s talk


W/Z Bosons at ATLAS (2/2)

• December 2010: First Measurement of December 2010: First Measurement of W+jets cross-sections at LHCW+jets cross-sections at LHC

• Highly Important since Highly Important since - PPrecise test of perturbative QCDrecise test of perturbative QCD- background for top, Higgs and many BSM background for top, Higgs and many BSM

models (e.g. SUSY) models (e.g. SUSY)

• Select anti-KT jets with radius 0.4, |y|Select anti-KT jets with radius 0.4, |y|<2.8, full W selection<2.8, full W selection

• Alpgen used to produce signal Alpgen used to produce signal templatetemplate

• Dominating uncertainty: JESDominating uncertainty: JES

• Much more details in Sergei‘s talkMuch more details in Sergei‘s talk


Top Quark (1/2)

• arXiv:1012.1792 [hep-ex]arXiv:1012.1792 [hep-ex]

• Cross-Section measurement based Cross-Section measurement based on 2.9pbon 2.9pb-1-1

-37 candidate events are observed in 37 candidate events are observed in the single-lepton topology the single-lepton topology

-9 events in the dilepton topology9 events in the dilepton topology

• Final Selection for single lepton Final Selection for single lepton decaydecay

• 1 isolated lepton pT>20 GeV1 isolated lepton pT>20 GeV

• EETTmissmiss > 20 GeV > 20 GeV

• EETTmissmiss + m + mTT (W) > 60 GeV (W) > 60 GeV

• ≥≥4jets with p4jets with pTT >20GeV >20GeV

• ≥ ≥ 1 b-tag jet1 b-tag jet


Top Quark (2/2)• Dominating BackgroundsDominating Backgrounds

- Muon channel: W+jetsMuon channel: W+jets- Electron channel: QCD, W+jetsElectron channel: QCD, W+jets- Both backgrounds are estimated in a data-driven wayBoth backgrounds are estimated in a data-driven way

• Cross-Section measurement with perfect agreement to Cross-Section measurement with perfect agreement to theoretical predictiontheoretical prediction- Most precise measurement at 7TeVMost precise measurement at 7TeV

• Dominating systematic uncertaintiesDominating systematic uncertainties- normalisation of the QCD multi-jet background in the normalisation of the QCD multi-jet background in the e+jets e+jets channelchannel- uncertainties which affect mainly the ttuncertainties which affect mainly the tt f f acceptance: jet energy acceptance: jet energy reconstruction, b-tagging and ISR/FSRreconstruction, b-tagging and ISR/FSR


Diphoton Events with Large ETMiss(1/1)

• Several new physics models predict much Several new physics models predict much larger γγ + Elarger γγ + ETT

MissMiss rates than SM rates than SM

- Example: Universal Extra DimensionExample: Universal Extra Dimension- postulate the existence of additional spatial postulate the existence of additional spatial

dimensionsdimensions- Predict for each SM particle a series of Predict for each SM particle a series of

excitations: Kaluza-Klein (KK) towerexcitations: Kaluza-Klein (KK) tower- Lightest KK particle is γ* which would undergo Lightest KK particle is γ* which would undergo

a cascade decay to γa cascade decay to γ

• Benchmark ModelBenchmark Model- One single TeV−1-sized UED, with One single TeV−1-sized UED, with

compactification radius Rcompactification radius R- values of 1/R < 728 GeV are excluded at 95% values of 1/R < 728 GeV are excluded at 95%

CL, providing the most sensitive limit on this model CL, providing the most sensitive limit on this model to dateto date

• See also our Prompt Photon Paper: See also our Prompt Photon Paper: arXiv:1012.4389 [hep-ex], Talk by Sergei ChekanovarXiv:1012.4389 [hep-ex], Talk by Sergei Chekanov


Searches for excited quarks (1/1)

• Search for decay of excited quarks in two Search for decay of excited quarks in two partons, i.e. q*partons, i.e. q*jj signaturesjj signatures

• Looked for di-jet resonance in the Looked for di-jet resonance in the measured Mmeasured Mjjjj distribution distribution

-leading jet pt>150 GeVleading jet pt>150 GeV

-MMjjjj>350GeV>350GeV

-spectrum compatible with a smooth spectrum compatible with a smooth monotonic functionmonotonic function

• Published exclusion limit superseded all Published exclusion limit superseded all previous experimentsprevious experiments

-0.5<M(q*)<1.53 TeV excluded at 95% C.L.0.5<M(q*)<1.53 TeV excluded at 95% C.L.-Experimental systematic uncertainties Experimental systematic uncertainties

included: JES (dominant), background fit, included: JES (dominant), background fit, luminosity.luminosity.


Heavy Ions (1/1)• Heavy Ions run in 2010Heavy Ions run in 2010

-lead-lead collisions lead-lead collisions -nucleon-nucleon centre nucleon-nucleon centre

of mass energy √s = 2.76 of mass energy √s = 2.76 TeVTeV

• Collisions of heavy ions Collisions of heavy ions at ultra-relativistic at ultra-relativistic energies are expected to energies are expected to produce quark gluon produce quark gluon plasmaplasma

-Jet QuenchingJet Quenching

• First observation of an First observation of an enhancement of events enhancement of events with large dijet with large dijet asymmetriesasymmetries


ContentContent• ATLAS Detector and Data Taking• Detector Performance• Highlights of the 2010 Physics Results• Prospects and Conclusion

Summary• Excellent performance of ATLAS detector

• Subsystems operating according to design specifications• High data-collection efficiency• Monte Carlo simulation in good agreement with data

• Many Interesting physics results already published• Hope to see something new in 2011

Documents

M. Schott (CERN) Page 1 Status of the ATLAS Experiment Epiphany 2011 Matthias Schott (CERN) On behalf of the ATLAS Collaboration Content ATLAS Detector