1. ATLAS detector commissioning with cosmics and first beam Alessandro Cerri on behalf of the ATLAS collaboration

2. Talk Outline Introduction Status of ATLAS Commissioning of the detector with cosmic rays First beam …plans? Please see later at this conference: D. Sampsonidis: “early ATLAS physics” Weina Ji: “B hadron properties @ LHC” A. Dewhurst: B s  J/ψϕ with ATLAS and CMS S. Chouridou: “expected performance of the ATLAS inner detector” 2

3. 37 Countries 169 Institutions ~2800 Scientific Authors (~800 PhD students) Talk presented on behalf of the ATLAS Collaboration Albany, Alberta, NIKHEF Amsterdam, Ankara, LAPP Annecy, Argonne NL, Arizona, UT Arlington, Athens, NTU Athens, Baku, IFAE Barcelona, Belgrade, Bergen, Berkeley LBL and UC, HU Berlin, Bern, Birmingham, UAN Bogota, Bologna, Bonn, Boston, Brandeis, Bratislava/SAS Kosice, Brookhaven NL, Buenos Aires, Bucharest, LPSC Grenoble, Technion Haifa, Hampton, Harvard, Heidelberg, Hiroshima, Hiroshima IT, Indiana, Innsbruck, Iowa SU, Irvine UC, Istanbul Bogazici, KEK, Kobe, Kyoto, Kyoto UE, Lancaster, UN La Plata, Lecce, Lisbon LIP, Liverpool, Ljubljana, QMW London, RHBNC London, UC London, Lund, UA Madrid, Mainz, Manchester, CPPM Marseille, Massachusetts, MIT, Melbourne, Michigan, Michigan SU, Milano, Minsk NAS, Minsk NCPHEP, Montreal, McGill Montreal, FIAN Moscow, ITEP Moscow, MEPhI Moscow, MSU Moscow, Munich LMU, MPI Munich, Nagasaki IAS, Nagoya, Naples, New Mexico, New York, Nijmegen, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma, Oklahoma SU, Olomouc, Oregon, LAL Orsay, Osaka, Oslo, Oxford, Paris VI and VII, Pavia, Pennsylvania, Pisa, Pittsburgh, CAS Prague, CU Prague, TU Prague, IHEP Protvino, Regina, Ritsumeikan, UFRJ Rio de Janeiro, Rome I, Rome II, Rome III, Rutherford Appleton Laboratory, DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, SLAC, Southern Methodist Dallas, NPI Petersburg, Stockholm, KTH Stockholm, Stony Brook, Sydney, AS Taipei, Tbilisi, Tel Aviv, Thessaloniki, Tokyo ICEPP, Tokyo MU, Toronto, TRIUMF, Tsukuba, Tufts, Udine/ICTP, Uppsala, Urbana UI, Valencia, UBC Vancouver, Victoria, Washington, Weizmann Rehovot, FH Wiener Neustadt, Wisconsin, Wuppertal, Würzburg, Yale, Yerevan Cambridge, Carleton, Casablanca/Rabat, CERN, Chinese Cluster, Chicago, Chile, Clermont- Ferrand, Columbia, NBI Copenhagen, Cosenza, AGH UST Cracow, IFJ PAN Cracow, UT Dallas, DESY, Dortmund, TU Dresden, JINR Dubna, Duke, Frascati, Freiburg, Geneva, Genoa, Giessen, Glasgow, Göttingen, 3

4. The ATLAS Collaboration, G. Aad et al., The ATLAS Experiment at the CERN Large Hadron Collider, JINST 3 (2008) S08003 The ATLAS Detector 4

5. The ATLAS Inner Detector SCT TRT Pixe l Tracking |  |<2.5 B=2T Silicon pixels (Pixel) : 80 10 6 channels Silicon strips (SCT) : 6.3 10 6 channels Transition Radiation Tracker (TRT) : straw tubes (Xe), 3.5 10 5 channels e/  separation Resolutions:  /p T ~ 1.5%  3.4x10 -4 p T (GeV)  d0 ~ 10  140 / P t (GeV) μm 5

6. The ATLAS barrel tracker goes in place (August 2006) 6

7. Muons in ATLAS Stand-alone momentum resolution Δpt/pt < 10% up to E μ ~ 1 TeV Barrel: ~650 MDT (Monitored Drift Tubes) precision chambers for track reconstruction, ~550 RPC (Resitive Plate Chambers) for trigger 2-6 Tm |  |<1.3 4-8 Tm 1.6<|  |<2.7 Barrel chambers MDT 7

8. Forward Muon Detectors Big wheels (and end-wall wheels): ~500 MDT precision chambers and ~3600 TGC (Thin Gap Chambers) trigger chambers September 2007 February 2008 Small wheels: 32 CSC (Cathode Strip Chambers) precision chambers + ~80 MDT 8

9. ATLAS Magnets System October 2005: full barrel toroid is in place 8 superconducting coils, 25 m long, 100 ton each, I=20.5 kA, T=4.5 K Since August 2008, the full magnet system (barrel toroid, end-cap toroids and central solenoid) has been operated at full current for long periods June-July 2009 Planned short runs, not quenches! 9

10. Calorimetry |  |<5 Hadronic Endcap Tile Barrel em Electromagnetic Calorimeter Barrel, Endcap: Pb-LAr  E ~10%/√E for e/γ 170000 channels: longitudinal segmentation Hadron Calorimeter Barrel: Iron-Tile EC/Fwd: Cu/W-LAr (~19000 channels)  /E ~ 50%/  E  0.03 (~10 ) Trigger and measurements for e/γ, jets, Missing E T 10

11. The ATLAS Trigger/DAQ infrastructure Front End Electronics Readout Drivers Level-2 Trigger RoI e/γ, , jet,.. Full granularity in RoI ~ 500 PC (multi-core) Level-1 Trigger Calorimeter Muon System Hardware based Coarse granularity Event Filter ~1800 PC (multi-core) High bandwidth Data Network Event Building More PC farms on Data Network DAQ software Control, configuration, monitoring on Control Network 300 MByte/s to Computer Center ~3 Pbytes stored / year High Level Trigger (HLT) Readout System Custom built buffers in PC farm 11

12. Today: 850 HLT PCs installed (35% of what we plan for high luminosity) Level-1 Trigger racks In total about 300 racks with electronics in the underground counting rooms The ATLAS Trigger and DAQ systems have been extensively exercised since early 2008 running simulated data through the DAQ chain, as well as with several periods of cosmic rays data taking! 12

13. Computing! ATLAS world-wide computing: ~ 70 sites (including CERN Tier0, 10 Tier-1s, ~ 40 Tier-2 federations) Amazing operational challenges: ~ 50 PB of data to be moved across the world every year 10 9 raw events per year to be processed and reprocessed Complex Computing Model Operation and computing models have been stress-tested and refined over the last years through functional tests and data challenges of increasing functionality, size and realism. 13

14. ATLAS was ready for LHC data-taking in August 2008 August-October 2008: global cosmics runs (with full detector operational) (~ 500 M events collected, 1.2 PB of raw data) September 2008: single-beam events recorded October 2008: detector opened for maintenance, consolidation, a few repairs June 2009: closed again End June 2009: global cosmics runs restarted (100 M events collected) 14

15. 10 September 2008, ~10h am: waiting for first beams 15

16. 10 September 2008, 10:19h am: first ATLAS ‘beam splash’ event recorded tertiary collimators 140 m Beam pick-ups (BPTX) (175 m) Beam bunches (2x10 9 protons at 450 GeV) stopped by (closed) collimators upstream of experiments  “splash” events in the detectors (debris are mainly muons) ~ 100 TeV in the detector ! 16

17. First beam: trigger timing 10 September12 September Note different scale RPC not adjusted Remember: ATLAS is 6 LHC bunch crossings (25 ns each) across!!! Various systems aligned in time using beam pick-ups (BPTX) as reference Signal times of various triggers adjusted to match the BPTX reference Few splash events meant a jump in quality with respect to cosmic rays for detector timing! Remember: ATLAS is 6 LHC bunch crossings (25 ns each) across!!! Various systems aligned in time using beam pick-ups (BPTX) as reference Signal times of various triggers adjusted to match the BPTX reference Few splash events meant a jump in quality with respect to cosmic rays for detector timing! 17

18. ATLAS Commissioning with Cosmics Cosmic events collected from mid September to end October 2008 18

19. A “typical” cosmic ray seen by ATLAS Cosmics rate in ATLAS: 1-700 Hz (varies with sub-detector size and location) Achieved precisions far better than expectations at this stage Commissioning with cosmics: Debug the experiment  fix problems First calibration and alignment studies Gain global operation experience in situ 19

20. Commissioning with cosmics: plenty of results! 20

21. LVL1 calo trigger LVL1 trigger towers Full calo readout 12m 18m Extrapolation to the surface of cosmic muon tracks Access shafts Muon (shower) energy measured with full calorimeter readout vs energy measured in trigger towers (  x  =0.1x0.1) by level-1 calorimeter trigger. [Initial calibration: final one will reduce spread (from RPC trigger chambers) 21

22. Trigger on cosmics ATLAS L1 and HLT triggers have reliably collected, selected and rejected 100s of millions of events! Curves reflect the different geometrical acceptance of the various sub-detectors Efficiency of the track trigger at level-two vs track impact parameter ~ 5 M cosmics events selected by this trigger Radial impact parameter d 0 (mm) Difference in η between the Event Filter muon and the offline reconstructed muon Good agreement, width of fitted Gaussian = 0.007 Tails understood, due to slightly different configuration online vs offline Difference in η between the Event Filter muon and the offline reconstructed muon Good agreement, width of fitted Gaussian = 0.007 Tails understood, due to slightly different configuration online vs offline η difference: event filter - offline 22

23. ID alignment and B-field measurement Pixel detector alignment with cosmics data residuals before alignment residuals after alignment MC (perfect detector) Distance (mm) between fitted track and hits in the individual layers Solenoid B-field mapping campaign 2006: precision of 2x10 -4 (4 Gauss) achieved Both are essential ingredients for precise measurements of tracks and knowledge of absolute momentum scale to << 0.1% (e.g. for W-mass measurement) Pixels, SCT: achieved with cosmics: alignment precision: ~ 20  m (ultimate goal 5-10  m) alignment stability Oct-2008-June-2009: few microns layer hit efficiency: > 99% ; pixel occupancy: 10 -10 250 000 points measured (5 currents) 23

24. ID track reconstruction Cosmic rays allow direct measurement of track resolutions: Cosmic tracks cross both the upper and lower hemisphere of the ID Split in the center and refit tracks separately Cosmic rays allow direct measurement of track resolutions: Cosmic tracks cross both the upper and lower hemisphere of the ID Split in the center and refit tracks separately Impact parameter resolutionMomentum resolution Already close to ideal detector performance! 24

25. Muon Spectrometer Alignment Cosmics data, field off Muon spectrometer is basically another tracking system! Alignment needed to achieve nominal performance Study unbiased residuals at different alignment stages Alignment procedure successfully tested on cosmic ray tracks Combination of segments on outer layers 25

26. ID and Muon Spectrometer Correlation Muon  coordinate Inner Detector Muon Spectrometer Δ Muon momentum (ID-MS) [GeV/c] Difference between the muon momentum measured in the ID and in the MS for tracks in the bottom part of the detector (energy lost in the calorimeter: ~ 3 GeV as expected) 26

27. ATLAS Detector Status Overall data taking efficiency: already ~ 83% during the latest cosmic weeks [6-14 hour long simulated LHC stores in July 2009] Sub-detectorNumber of channelsOperational fraction (%) Pixels80 M98.5 SCT Silicon Strips6 M99.5 TRT Transition Radiation Tracker350 k98.2 LAr EM Calorimeter170 k99.1 Tile Calorimeter980099.5 Hadronic endcap LAr calo560099.9 Forward LAr calorimeter3500100 MDT Muon Drift Tubes350 k99.3 CSC Cathode Strip Chambers31 k98.4 RPC Barrel Muon Trigger370 k~95.5 ( aim >98.5) TGC Endcap Muon Trigger320 k99.8 27

28. Expectations with 100 pb -1 Goals in 2010: 1) Commission and calibrate the detector in situ using well-known physics samples e.g. - Z  ee,  tracker, ECAL, Muon chamber calibration and alignment, etc. - tt  bl bjj jet scale from W  jj, b-tag performance, etc. 2) “Rediscover” and measure Standard Model at LHC: W, Z, tt, QCD jets … (also because omnipresent backgrounds to New Physics) 3) Early discoveries ? Potentially accessible: Z’, SUSY, …. surprises ? Note: expect up to 200 pb -1 after first physics run at high energy Channels (examples)Expected no of events in ATLAS after cuts √s = 10 TeV, 100 pb -1 J/ψ−> μμ ϒ −> μμ W −> μν Z −> μμ tt −> W b W b −> μν+X QCD jets p T > 1 TeV m ~ 1 TeV ~10 6 ~ 5 10 4 ~ 3 10 5 ~ 3 10 4 ~ 800 ~ 500 ~ 5 few pb -1 50 pb -1 100 pb -1 …. 28

29. ATLAS performance on Day 1 Expected @ Day 1Ultimate goalPhysics samples to improve EM unif.~2.5%0.7%Isolated e, Z  ee EM E-scale2-3%<0.1%J/ψ, Z  ee Hadronic unifo. 2-3%1%Single π, QCD jets Hadronic E-scale 5-10%1%γ/Z - jet, W  jj in tt events Tracker align.20-200 μm5 μmIsolated tracks/μ, Z  μμ, cosmics Muon align.40-1000 μm30 μmOptical + tracks @ no field, Z  μμ 29

30. Pending Issues Calibrations, alignments etc. (previous slide) Finalization of trigger timing – needs beam events Concerns: long term reliability of – Low Voltage power supplies – LAr readout optical links – Inner detector cooling Back-up solutions are being prepared for future shut-down periods 30

31. Conclusion ATLAS in excellent shape O(10 -3 ) non-working channels!!! 0.5B cosmic and “few” single beam events: – Detector performance above expectations – Procedures and people trained to operate the detector Software and computing ready to simulate, analyze and distribute data! Ready for the challenge of LHC collisions! 31

32. Backup

33. The Transition Radiation Tracker Transition radiation intensity is proportional to particle  factor. The onset at high  ( E~100 GeV for muons) is observed with cosmic muons as compared to test beam results. Transition radiation intensity is proportional to particle  factor. The onset at high  ( E~100 GeV for muons) is observed with cosmic muons as compared to test beam results. 33

34. Performance on Day 1 Expected perf. Day 1Physics samples to improve EM relative2.5%Isolated e, Z  ee EM absolute2-3%Z  ee Hadronic rel.2-3%Single π, QCD jets Hadronic absolute5-10%γ/Z jet, W  jj in tt events Tracker align.20-200 μmIsolated tracks, Z  μμ, cosmics Muon align.40-1000 μmOptical + tracks @ no field, Z  μμ Ultimate GoalDriven by…Statistics Needed EM relative0.5%H  γγ 10 5 Isolated e, Z  ee EM absolute0.02%W mass10 5 Isolated e, Z  ee Hadronic rel.1%Missing E t Single π, QCD jets Hadronic absolute1%t massγ/Z jet, W  jj in tt Tracker align.10 μmb-tagging10 6 tracks Muon align.30 μmZ’  μμ 10 7 tracks 34