1. The ATLAS Liquid Argon Calorimeter: Overview and Performance Huaqiao ZHANG (CPPM) On behalf of the ATLAS Liquid Argon Calorimeter Group

2. ATLAS Detector 05/13/2010Huaqiao ZHANG (CPPM)2

3. ATLAS Detector 05/13/2010Huaqiao ZHANG (CPPM)3 Physical Goal: precision electroweak theory tests, Higgs Hunting and Physics beyond standard model Physics related to Calo: W,Z,top, Higgs, SUSY… Requirements to Calorimeter: Good ability of e/g ID and energy measurement for e/g, jets/Etmiss

4. ATLAS LAr Calorimetry (1) 05/13/2010Huaqiao ZHANG (CPPM)4 Sampling Calorimeter, Full phi coverage EM part|η|<3.2 [Pb-LAr] Hadronic End-cap: 1.5<|η|<3.2 [Cu-LAr] Forward Calorimeter: 3.1<|η|<4.9 [Cu,W-LAr] Test beam: 2001-2004 Cosmics data: 2006-2009 Sept. 2008, single beam data Collision data: Since Nov. 2009 We have more than 1 nb -1 collision data now!

5. ATLAS LAr Calorimetry (2) 05/13/2010Huaqiao ZHANG (CPPM)5 Fine Granularity and multi-layer at |η|<2.5 ensure accurate e/g id and energy reco. Grosser Granularity at High η region sufficient for Jet/Etmiss measurements LArg: 0.0186% of unrecoverable channels 1.4% of dead readout channels, EM: 1.5%, HEC: 0.1% FCAL: 0% (04.05.2010) Including ~20 Dead Optical Transmitters (will be fixed when detector is opened) Totally ~180K cells, 98.6 % operational EM (EMB+EMEC) – Pre-sampler: Recover energy deposited before Calo | η |<1.8, 0.025*0.1 – Strips: Fine η granularity ensure good gamma/pi separation | η |<3.2, typical 0.003*0.1 – Middle: Most EM energies deposited | η |<3.2, typical 0.025*0.025 – Back: Recover e/g longitudinal energy leakage |η| <2.5, 0.05*0.025 HEC – Four layers: 1.5<|η| <2.5,0.1*0.1;2.5<|η| <3.2, 0.2*0.2 FCAL – Three layers, 3.1 <|η| <4.9, Non projective

6. Show two 2 D plot somewhere about Calo… 05/13/2010Huaqiao ZHANG (CPPM)6 Are these energies in LAr Calo right? Lets check the LAr

7. LAr Calorimeter HV Status All HV at nominal but 6% reduced Energy Corrections depends on the HV setting and the cell geometry Correction factor based on test beam results 05/13/2010Huaqiao ZHANG (CPPM)7 HV is well treated across all the LAr detector

8. LAr temperature and purity LAr temperature – LAr signal sensitivity 2%/K (density: -0.45%/K, Velocity: -1.55%/K) – Require 100mK stability and homogeneity – Using 150-200 PT100 probes in each cryostats immersed in liquid argon – Homogeneity 59mk, with 1.5mk RMS for each probe over 10 days LAr purity – Electronegative impurities would reduce the measured signal – Require purity better than 1000ppb – 30 purity monitors in the three cryostats – Measured impurity: Barrel ~ 200ppb, EndCap ~ 140ppb 05/13/2010Huaqiao ZHANG (CPPM)8 Well within required 0.2% uncertainties of signal RMS of each probe

9. LAr Calorimeter pulse shape and drift time 05/13/2010Huaqiao ZHANG (CPPM)9 CR-(RC) 2 Prediction depend on the knowledge of drift time measurement E More details of drift time in C. Gabaldon’s talk The RTM(FPM diff.) method : Accuracy of pulse shape better than 2%

10. Readout Electronic Performance 05/13/2010Huaqiao ZHANG (CPPM)10 Typical Pedestal ~1000ADC Take Electronic Calibrations runs up to every fill Update the calibration constants every week Reprocessing data with closest electronic calibration runs. Long term stability of Calibration constants checked ATLAS preliminary Pedestal difference w.r.t. a reference run in 6 months Very good electronics stability RMS=0.0248

11. Uniformity check with cosmics data 05/13/2010Huaqiao ZHANG (CPPM)11 Most Probable Value(MPV) from Landau convoluted Gaussian fit Global uniformity agrees to within 1% in the Barrel

12. Nov 23 rd run Timing alignment L1Calo Trigger timing: – Align the timing for all Trigger Tower to give the on-time L1Acceptance – Mainly affect the trigger efficiency – See T. Childers talk “ATLAS Level-1 Calorimeter Trigger Hardware: Initial Timing and Energy Calibration” LArCalo timing: – Align the timing from L1Acceptance to offline readout slot (achieved since cosmics data), up to 1ns accuracy – Mainly affect the online energy reco. – Using single beam events to calculate the timing delays, cross check with data 05/13/2010Huaqiao ZHANG (CPPM)12 Collision candidates Timing of the LArCalo around 2 ns level Channel level correction is on going

13. L1 EM Calo Trigger performance 05/13/2010Huaqiao ZHANG (CPPM)13 Designed constant term: 5% L1Calo - LAr offline: Same detector, different readout, different granularity At granularity 0.1*0.1 L1 Calo works as expected L1EM5: Et > 5GeV Step of 1GeV Details see V. Dao’s talk “ Commissioning of the ATLAS Electron and Photon Trigger Selection ”

14. Missing E T in random Events 05/13/2010Huaqiao ZHANG (CPPM)14 Check Noise modeling LAr sub-detectors only: A dynamical topological cluster algorithm with seeds >4 noise and neighbor > 2 noise Better Noise suppression Close to the final choice of Et miss calculation Noise monitored online LAr Noise well modeled by Gaussian topo cluster has better noise suppression

15. LAr Energy Flow 05/13/2010Huaqiao ZHANG (CPPM)15 Good data quality run used All cells except noisy ones Occupancy Map of second layer 2009 (0.5 M)2010 (5M) Collision signal visible, data/MC agrees Cabling inversion found in Energy flow map and fixed in 2010 collisions

16. Egamma observations 05/13/2010Huaqiao ZHANG (CPPM)16 Details see D. Banfi’s talk ”Electron and photon reconstruction and identification with the ATLAS Detector” Energy Fraction in Second layer Pi0 and eta signal Remarkable e/g id and energy reco. shown in pi0 and eta signals MC/data agrees

17. Observation of Jets/Etmiss in LAr and Tile Calo 05/13/2010Huaqiao ZHANG (CPPM)17 Etmiss from TopoCluster, EMscale Jets from AntiK T D=0.6 algorithm, |η| 20 GeV, EMscale Details see D. Miller’s talk “ First Measurement of jets and missing transverse energy with the ATLAS calorimeter ” Jet and Etmiss are well modeled by MC

18. Show a W events Convertions …How? 05/13/2010Huaqiao ZHANG (CPPM)18 ATLAS LAr related talk: D. Gillberg: Performance of the ATLAS Forward Calorimeters in First LHC Data G. Pospelov: Tests of Local Hadron Calibration approaches in ATLAS Combined Beam Tests J. Ye: A Serializer ASIC at 5 Gbps for Detector Front-end Electronics Readout C. Gabaldon: Drift Time measurement in the ATLAS Liquid Argon electromagnetic calorimeter using cosmic muons H. Cheng: ATLAS LAr Calorimeter Readout Electronics Upgrade R&D for sLHC P. Giovannini: Local Hadron Calibration with Atlas

19. Summary After years of study with testbeam, cosmics, collisions, ATLAS Liquid Argon Calorimeters are approaching the optimized working point: – Remarkable stability of LAr temperature, purity, and readout electronics calibration constants. – Good overall energy reconstruction uniformity. – Timed at around ±2ns, allowing first un-bias performance studies of trigger, electron/photon, Jet/Etmiss with collisions data We have confidence in the ATLAS LAr system, and expect good performance in the future physics analysis 05/13/2010Huaqiao ZHANG (CPPM)19

20. Thanks 05/13/2010Huaqiao ZHANG (CPPM)20

21. Backup - TestBeam VLE electron 05/13/2010Huaqiao ZHANG (CPPM)21

22. Backup - Monitoring Except when explicitly mentioned, the plots shown here are routinely produced by tier 0 and were taken from this tier 0 output. They are however also available online and typical time scale to reach the accuracy needed to get meaningful plots are of the order of few minutes of cosmic runs (depending on the trigger rates of course). 05/13/2010Huaqiao ZHANG (CPPM)22