1. The ATLAS Liquid Argon Calorimeter Peilong Wang, Southern Methodist University For PHYS 5380 Fall 2014

2. Outline Physics requirements for the ATLAS LAr Calorimeter Structure of the ATLAS LAr Calorimeters Electromagnetic Calorimeters Electromagnetic Barrel Calorimeter (EMB) Electromagnetic End-cap Calorimeter (EMEC) Hadronic End-cap Calorimeters (HEC) Forward Calorimeters (FCal) Readout Electronics for the LAr Calorimeter Performance of the ATLAS LAr Calorimter 2

3. Physics Requirements for the LAr Calorimeter 3 Decided by the type of the collision statistical error ⊕ systematic error the detector’s response to the particle’s energy

4. Structure of the ATLAS LAr Calorimeter 4

5. Electromagnetic Barrel Calorimeter (EMB) 5 Cu electrode Honeycomb spacer Pb absorber clad in stainless steel

6. Sampling calorimeter & Accordion structure 6 Absorber layerActive layer An incoming particle loses its energy in the absorber layers, initiating a shower of secondary particles. The active layer collects the deposited energy.

7. 7 Electromagnetic End-cap Calorimeters (EMEC) EMEC

8. Hadronic End-cap Calorimeter (HEC) 8 HEC

9. Three modules: 1 EM (copper), 2Hadronic (tungsten). Forward Calorimeters (FCal) 9

10. 10 How the ATLAS LAr Calorimeter works

11. Readout Electronics for the LAr Calorimeter 11 Pileup noise Thermal noise Bipolar signal Shaping time

12. The LAr Calorimeter is well running at CERN now. The resolution and stability is demonstrated to be pretty good while running The proton and electron identification remains good when the number of the reconstructed primary vetices increasing Based on the great performance, the Higgs-like boson is discovered Performance of the ATLAS LAr Calorimeter 12

13. Thank you! Reference: ATLAS LArg Collaboration, “The ATLAS Liquid Argon Calorimeter: an overview,” J. Phys.: Conf. Ser. 160 012043, 2009 ATLAS Collaboration, “Performance of the ATLAS Liquid Argon Calorimeter after Three Years of LHC Operation and Plans for a Future Upgrade,” arXiv:1306.6756 R D Schaffer, “Pedagocial Lectures on Detection of Electromagnetic Interactions,” SMU, Oct. 28, 2014 13

14. Back up 14