ATLAS Detector Status & Performance H. H. Williams (University of Pennsylvania)

1. Highest-mass di-jet event observed so far: Mjj = 2.55 TeV ATLAS Detector Status & Performance H. H. Williams (University of Pennsylvania) Representing the ATLAS Collaboration pT (j1)=420 GeV pT (j2)=320 GeV

2. The ATLAS Detector Muon Spectrometer (||<2.7): air-core toroids with gas-based muon chambers Muon trigger and measurement with momentum resolution < 10% up toE ~ 1 TeV Length : ~ 46 m Radius : ~ 12 m Weight : ~ 7000 tons ~108 electronic channels 3000 km of cables 3-level trigger reducing the rate from 40 MHz to ~200 Hz Inner Detector (||<2.5, B=2T): Si Pixels, Si strips, Transition Radiation detector (straws) Precise tracking and vertexing, e/ separation Momentum resolution: /pT ~ 3.8x10-4 pT (GeV)  0.015 EM calorimeter: Pb-LAr Accordion e/ trigger, identification and measurement E-resolution: /E ~ 10%/E HAD calorimetry (||<5): segmentation, hermeticity Fe/scintillator Tiles (central), Cu/W-LAr (fwd) Trigger and measurement of jets and missing ET E-resolution:/E ~ 50%/E  0.03

3. Operational Efficiency Fraction of data labeled “Good” by subsystem Fraction of Channels Operational by subsystem 100% channels operational 97% Integrated Luminosity LVL1 Muon RPC Trig Forw LAr Calor RPC Det. Muon Drift Tube Tile Calor Pixel TRT LAr EM Calor LVL1 Muon TGC Trig EndC LAr Calor TGC Det. SCT LVL1 Calo Trig Muon CSC 95% data-taking efficiency (Efficiency includes time to ramp pixel, silicon bias voltage after stable beams declared) Luminosity detectors calibrated with van der Meer scans. Luminosity known today to ~11% (error dominated by knowledge of beam currents)

4. Trigger commissioning and operation 3 levels: LVL1, LVL2, Event Filter (EF) High-Level-Trigger (HLT) : LVL2 and EF Un-prescaled rates of some LVL1 items vs L • Trigger output: typically 300 Hz • History: • L < few 10 27 cm-2 s-1: minimum-bias • LVL1 trigger: hits in scintillator • counters (MBTS) located at • Z=± 3.5 m from collision centre • L > 1027 cm-2 s-1 : MBTS prescaled • (only fraction of events recorded) • 0thers items (EM2, J5, TAU5, MU0..): • un-prescaled • L ~ 1029 cm-2 s-1: start to activate HLT • chains to cope with increasing rate • while running with low LVL1 thresholds. • Jet items: prescaled (HLT rejection small) • Figure gives examples for L up 7x1029 300 Hz HLT on (μ) for MU0 fwd HLT on (e/γ) for EM2, EM3 J5 pre-scaled HLT on (τ) for TAU5

5. Tracking efficiency at HLT for electron candidates with EToff (calo) > 5 GeV LVL1 jet trigger efficiency for the lowest threshold (J5) Crucial for jet cross-section Crucial for J/ψ ee LVL1 forward muon trigger efficiency for the lowest threshold (MU0) Example of trigger performance studies Crucial for di-muon resonances

6. ATLAS Inner Detector Tracking h < 2.5 Immersed in 2 Tesla field Intrinsic Position Resolution 10m pixels, 17m SCT, ~130m TRT in R,f 115m pixels, 580m SCT in z (barrel) • Pixels • 3 barrel layers, 3 disks each endcap • 1744 modules • Silicon Strip Detectors (SCT) • 4 barrel double-sided, 9 disks in endcaps • 4088 modules • Transition Radiation Tracker (TRT) • 4 mm straw proportional drift tubes • Tracking and transition radiation detection • 298k straws

7. Pixel Detector - Highlights Electronics measures time-over-threshold (Tot) Tot ~ charge deposition ~ dE/dx dE/dx depends on b 3 pixel hits allows good dE/dx measurement Position Residuals Particle ID via dE/dx sdata~ 25m (Really FWHM/2.35) Pos trks f -> K+K- Neg trks Deuterium Protons Kaons Pions

8. Silicon Strip Detector (SCT) - Highlights SCT Efficiency SCT Residuals sdata~ 42m Lorentz Angle – Measured & Modeled

9. Transition Radiation Tracker (TRT) - Highlights Track Position vs Drift Time (R-t) Measures Drift Time and Trans. Rad. Photons Position Residuals in TRT Barrel Electron ID using Number TR Photons sdata~ 141m

10. Combination of Pixel/SCT & TRT Very Powerful

11. Impact Parameters & Secondary Vertices Impact Parameter – d0 Decay Length Significance – L/s

12. Multiple Primary Vertices Already at 1.6 * 1030 mean number interactions~ 1.3 Event with 4 pp interactions in the same bunch-crossing ~ 10-45 tracks with pT >150 MeV per vertex Vertex z-positions : −3.2, −2.3, 0.5, 1.9 cm (vertex resolution better than ~200 μm)

13. Tracking: from early observation of peaks to cascade decays and J/ψ  ee - Ks  p+p- PDG: 1321.32 Ξ  Λπ p π- Λ π- 78 nb-1 Momentum scale known to permil in this range Resolution as expected (multiple scattering) Complex algorithms (cascades, b-tag, Brem recovery, …) work well Working on material, alignment, data-driven efficiencies, … J/ψ  e+e-

14. J/ψ provides large samples of low-pT muons to study μ trigger and identification efficiency, resolution and absolute momentum scale in the few GeV range Absolute momentum scale known to ~ 0.2% and momentum resolution to ~2 % in the few GeV region J/ψ mass peak vs muon η J/ψ mass resolution vs muon η 5 MeV PDG Inner Detector Inner Detector

15. Reconstruction of Conversions: g e+e- Reconstruction of Conversions very important for Higgs -> ggand many Other physics processes Mapping the Inner Detector material with γ  e+e- conversions … Reconstructed conversion radius of γ  e+e- from minimum bias Data Pixel 1 √s = 7 TeV Pixel 2 Beam pipe Pixel support structures Pixel 3 SCT 1 SCT 2 π0 Dalitz decays Data show that Pixel supports are displaced in the simulation Charged particle interactions also being used succesfully.

16. The ATLAS calorimeter system (1) Surrounded by Tile Calorimeter  |h|<1.7 Liquid Argon (LAr) detectors in 3 cryostats |h|<5 17m 1780 9m 4m Intrinsically linear and stable with time Intrinsic radiation-hard Excellent time resolution Maximum absorption depth at least cost

17. The ATLAS calorimeter system (2) • Sampling EM calorimeter • Absorber : lead with accordion shape • Active material : liquid argon (90 K) • Readout : large electrodes (2 m2) • Sampling hadronic calorimeters • Mix of technologies to cover |h|<5 • Steel + Tile scintillators  Tile • Copper + LAr  HEC • Copper/Tungstate + LAr  FCal S3 : DhxDf = 0.05x0.025 Shower ends 10l S2 : DhxDf = 0.025x0.025 Shower develops S1 : DhxDf ~ 0.003x0.1 g/p0 separation PS : DhxDf ~ 0.025x0.1 Recover energy loss Hermetic in f, very granular (173k cells)  Good e(g) resolution, e/jet separation Hermetic (>10 l) up to |h|<5  Good jet and Etmiss resolution

18. Performance of EM Calorimeter Relative energy outside S1 shower core • Extract prompt electron/g samples using EM calorimeter granularity Electron vs hadrons Photons vs p0 g p0 Layer X0 ET(cluster)>7 GeV, |h|<2.0, track, EM-like shower in S2 >2 16 ~4 S3 S2 S1 PS (E±3−E±1)/E±1 ET>10 GeV, loose identification E(S1)/Etot Fraction total energy in S1 (E±3−E±1)/E±1 Good data-MC agreement for ATLAS EM calorimeter identification variables

19. Properties of Jets and Calorimeter Response Jet radial shape Number of clusters in jets pT>7 GeV vs number of tracks Longitudinal jet profile Isolated hadrons E +5% -5%

20. Jet Energy Scale uncertainty Ultimate goal: ~1% Dominant uncertainty on jet cross-section measurement Jet momenta corrected (for calorimeter non-compensation, material, etc.) using η/pT-dependent calibration factors derived from MC (need ~ 1 pb-1 for in-situ γj) • Builds on detailed foundation work to • understand main ingredients by • comparing MC/data (see before) • Many sources of systematic • uncertainties studied in detail Inter-calibration central-forward checked using jet pT-balance Today JES known in ATLAS to : ~ 7%

21. Missing transverse energy Sensitive to calorimeter performance (noise, coherent noise, dead cells, mis-calibrations, cracks, etc.), and cosmics and beam-related backgrounds Calibrated Calibrated ETmiss from minimum-bias events ETmiss spectrum from SUSY searches: events with ≥ 3 high-pT jets Measured over ~ full calorimeter coverage (3600 in φ, |η| < 4.5, ~ 200k cells) SUSYx10

22. pT (jet) > 1.12 TeV Observed event with hardest jet pT (j1)= 1120 GeV pT (j2)= 480 GeV pT (j3)= 155 GeV pT (j4)= 95 GeV Event display shows uncalibrated energies

23. Atlas Muon System

24. As seen by a W -> m n event Efficiency Chamber Resolution Alignment score ~ 100m s ~ 430m

25. Muon System Momentum Resolution Small Muon Sectors Large Muon Sectors Data (cosmics) Data (cosmics) MC (cosmics) MC (cosmics)

26. Di-muon resonances Full data sample • Simple analysis: • LVL1 muon trigger with • pT ~ 6 GeV threshold • 2 opposite-sign muons • reconstructed by combining • tracker and muon spectrometer • both muons with |z|<1 cm • from primary vertex • Looser selection: includes also muons made of Inner Detector • tracks + Muon Spectrometer segments • Distances between resonances fixed to PDG values; • Y(2S), Y(3S) resolutions fixed to Y(1S) resolution

27. Z  ee, μμ measurements σNNLO (γ*/Z  ll) ~ 0.99 nb per family for M(ll) > 60 GeV From the sub-sample (~ 225 nb-1) used for the cross-section measurement GeV ee μμ Peak 89.6± 0.8 90.5 ± 0.8 Width (ΓZ unfolded) 3.6 ± 0.8 4.2 ± 0.8  still some work to do on alignment of ID and forward muon chambers, and on calorimeter inter-calibration, to achieve expected resolution

28. After call cuts except mT Full data sample • Work to determine systematic uncertainties • (ETmiss, …) in the presence of pile-up ongoing • W cross-section and asymmetry measurements • presented here are based on first 17 nb-1(recorded • at lower instantaneous luminosity) After all selections W  μν: 1111 events W  eν: 815 events Observed in data W eν(296 nb-1): 815 events W μν(291 nb-1): 1111 events