1. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Electromagnetic Calorimetry and Electron/Photon performance in ATLAS

2. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Outlook of the talk The ATLAS electromagnetic calorimeter system –Physics issues –Design overview Status of the construction Test-beam and simulation results

3. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Standard Model Higgs Search Jets Jets, Missing E t Electrons Photons Precise and Hermetic Calorimetry is Mandatory for Most of LHC Physics ! Jets, Missing E t

4. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Liquid Argon properties Long-term stability Response linearity over 15-16 bits dynamic range Intrinsic good radiation-tolerance Homogeneity of construction small constant term

5. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Some design goals for the EM calorimeter Sampling term 10%/  E or better (for SM H) Constant term 1% or better (for Z’ and H  ) > 24 X 0 depth (to limit leakage effect on resolution) Linearity 0.5% up to 300 GeV (H , H 4e)

6. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Principle of detection Accordion geometry benefits : No cracks in  Small  modulation (few per mille) Cabling on front and back only Low inductance HV 2 kV on 2.2 mm gap

7. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Barrel Calorimeter structure Fine strips for  /  0 Presampler for dead matter

8. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration End-cap Calorimeter structure Structure similar to the barrel, but : Varying gap thickness Varying high voltage Increased complexity Outer wheel (1.4<  <2.5) Inner wheel (2.5<  <3.2)

9. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Barrel Modules Construction finished these days ! One wheel assembled and successfully inserted into the cryostat Construction took in total about 3-4 years (including procurement, fabrication of absorbers, electrodes, spacers, plus stacking itself) Constant term contribution from mechanics evaluated to 0.3% (from mech. measurements)

10. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Barrel Wheel Assembly

11. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Barrel Wheel Insertion

12. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Potential Problems One 16 channel HV unit 2*8 channels per Half-module ~10 channels dead (after test of complete wheel, 55000 channels) About 0.1% of channels with HV on only one side of the electrode

13. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration End-Cap Modules 10 modules ready for assembly (one wheel=8 modules) Module stacking will finish by February 2004 Assembly of first wheel has begun (see photos)

14. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration End-Cap wheel Assembly 3 modules assembled these days !

15. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Some Test-Beam results 4 barrel and 3 end-cap modules have been beam-tested, from 2000 to 2002. Topics studied : Energy resolution, uniformity, position resolution, crosstalk, MIP response, etc

16. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Test-Beam Setup Setup similar for barrel and end-cap Located at CERN, North area (H8&H6) Electron beam from 10 to 300 GeV Read-out similar to ATLAS electronics, but not yet radiation hard.

17. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Signal Reconstruction Exponential current Physics signal Signal sampled every 25 ns Optimal filtering Amplitude : A =  a i s i Time : A.t =  b i s i Physics signal Calibration signal

18. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Crosstalk Measurements Crosstalk nature (inductive, resistive, capacitive) deduced from Signal shapes

19. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Energy Resolution One of the first points looked at Both barrel and end-cap are within specification Sampling : 10.4% Constant : 0.27%

20. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration MIP Response Will be slightly worse at LHC : about 5 (different electronics) First use : Cosmic runs But also at LHC…

21. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Corrections to raw energy measurements Lateral shower containment correction  Modulation correction

22. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Sampling weighting Presampler allows to Correct for dead matter Search for Optimal weight No presampler (1.8 X 0 ) Presampler included, Optimal weight

23. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Barrel Uniformity Region  =0.8 not included RMS/E=0.57% (515 cells)  =0  =0.8  =1.4 e Pb =1.53e Pb =1.13

24. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration End-Cap Uniformity 0.86%0.44% 0.66% 0.43%0.46%0.35%0.43% η number in S2 Φ number in S2 These number match the specifications

25. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Barrel Position Resolution Resolution in  units x 1000 S-shape fit to data on data :  = (0.360  0.009) or 0.55 mm

26. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration End-Cap Angular Resolution

27. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration  /  0 separation Needed for H to  Rejection of ~3 at 90% efficiency for  needed

28. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Barrel Intrinsic Time Resolution  (19,11) (18, 10) (19,10) (20,10) (19, 9)   Tool to reject instrumental Backgrounds Search for  0  G  in GMSB SUSY models ~ Time difference  (ps)

29. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Future Test-Beams Combined Tests (Tracker, EM Calorimeter, Had Calorimeter, for barrel + end-caps) Tuning of online software Understanding/tuning of various shower packages (G4, Fluka etc) Test of calibration procedure Energy scale

30. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Electron/Photon reconstruction Bremsstrahlung recovery E/p measurement Low energy electrons identification Electron/Jet separation Conversion reconstruction Photon/Jet separation Z ee (online calibration)

31. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Bremsstrahlung Recovery The ID represents about 0.5 X 0 before the EM calorimeter sizeable probability for Bremsstrahlung (20% of electrons loose 50% of energy as Brem photons within ID) Use the calorimeter cluster barycenter as an additional point in track fit

32. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Bremsstrahlung Recovery Standard  -like fit Standard e-like fit (Brem allowed) Standard  -like fit + calo position

33. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration E/p measurement 400 calorimeter regions can be calibrated at 0.1% with 1 M electrons 30M W e expected in 1 year at low luminosity ! Useful as a cross-check of Z to ee calibration

34. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Low Energy Electrons ID used to guide the calorimeter clustering Define probability distributions in various  and P t ranges Combine Needed to tag b to eX events

35. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Electron/Jet Separation Combination of calorimeter information and ID information give a jet rejection over 100 000 for 70% e efficiency @ p t 30 GeV(low lumi) 45 000 70% (high lumi)

36. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Conversion reconstruction Use 3×7 cluster, plus E 3×7 vs R conv (from ID)

37. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration  /Jet separation Needed for H to  Look for tracks within  =±0.1,  =±0.1 around 3×7 calorimeter cluster H to , Low lumi H to , High lumi

38. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Higgs mass resolution H to 4 e H to  @ 130 GeV : 1.3 (low lum) 1.55 (high lum) Acceptance 80% within ±1.4  H to 4 e @ 130 GeV : 1.54 (low lum) 1.81 (high lum) Acceptance 84% within ±2 

39. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Calibration with Z to ee decays Expected event rate : 1 Hz at low luminosity 0.3 % accuracy possible over 0.2×0.4 regions (~400) within a few days

40. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Conclusions (1) Construction and assembly of significant parts of the detector achieved Significant milestones have been passed (Insertion of barrel wheel, start of end-cap assembly) Next important steps :  Filling of the cryostats with Liquid Argon (2004)  Full test of a complete ATLAS electronics crate (End 2003)

41. LHC Symposium 2003 Fermilab 01/05/2003 Ph. Schwemling, LPNHE-Paris for the ATLAS collaboration Conclusions (2) Lots of test-beam data (and work on it ) has given us confidence the detector meets the specs Thinking now shifts progressively to commissioning : Z  ee, cosmic runs etc