1. The Forward Liquid Argon Calorimeter of the ATLAS Detector Geant4 Workshop'03 2-6 September. Triumf, Vancouver Patricia Méndez Lorenzo. CERN EP/SFT 1. Introduction and Generalities 2. FCAL at TestBeam 3. Simulation of FCAL with Geant4 4. Results of the Simulation 5. Summary 1

2. Introduction and Generalities Physics to be done at the LHC 1. Origin of the mass at the electroweak scale; search of Higgs boson ► H γγ for 90<M H <150 GeV ► H ZZ 4l for 130<M H <M Z ► WW, ZZ fusion with H ZZ, WW l,νν, 2jets for M H up 1 TeV ► pp WH, ZH, ttbar H, H bbbar (Excluded by LEP) for 80<M H <100 GeV Calorimetry plays a central role on subdetectors design at LHC 2. Deep study of the top and botton quarks 3. Search of new physics: SUSY, technicolours, extra-dimensions.... 2

3. General ATLAS Calorimeter System Goal: High precision measurements of energy and position of electrons, photons, jets and missing E T Requirements: ◘ Rapidity coverage ◘ Good electron reconstruction ◘ Excellent energy resolution ◘ Accurate measurement of the shower position Main Elements: ◙ One central cryostat barrel and 2T super-conducting solenoid ◙ Two endcaps, in each one: one electromagnetic, two hadronic wheels and one forward calorimeter Hadronic Tile Calorimeters EM Accordion Calorimeters Hadronic lAr EndCap Calorimeters Forward lAr Calorimeters 3

4. The ATLAS Forward lAr Calorimeter (FCAL) Goal of the FCAL Full coverage of the system for a good determination of the missing energy (undetected particles as neutrinos) Design ► 1 Electromagnetic copper/liquid argon module (FCAL1) ► 2 Hadronic modules (FCAL2, FCAL3) with tungsten as absorber Construction ► Several prototypes for FCAL1 constructed and tested successfully at Brookhaven and CERN ► Full depth pre-production prototypes for FCAL1 and FCAL2 (Module 0) designed and built in Arizona and Canada in 1998 Barrel EndCap EM Accordion Calorimeter Had EndCap Calorimeter FCAL Calorimeter 4

5. The FCAL at the TestBeam FCAL1 and FCAL2 prototypes (Module 0) have been tested at CERN in 1998 during a testbeam program with electrons, pions and muons ♦ Detectors and elements included in the TestBeam Setup included in the Simulation ♦ Description of FCAL module as close as possible to real detectors FCAL Module 0 test beam in Geant4 Particles enter the setup from the lower left corner FCAL1 Module 0 FCAL2 Module 0 Cryostat 5

6. Simulation of FCAL Module 0 with Geant4 Important parts: Geometry Cryostat EM Module and Had Modules TestBeam SetUp Physics Physical Processes Input Particles: electrons Visualization and histogramming Visualization packages Anaphe and Aida Simulation based on TestBeam'98 data included as a Geant4 advanced example called lAr_calorimeter 6

7. Simulation of FCAL Module 0 with Geant4 Detector Geometry Part int main(int argc, char** argv){............ G4RunManager* runManager = new G4RunManager; FCALTestbeamSetup* detector = new FCALTestbeamSetUp; runManager ->SetUserInitialization(detector);............... FCALCryostatVolumes FCALTestbeamSetUpSD FCALEMModule (including EMParameters.input) FCALHadModule (including HadParameters.input) FCALEMModuleSD FCALHadModuleSD 7

8. Simulation of FCAL Module 0 with Geant4 Standard Advanced Examples Design for Definition of Particles and Physical Processes Classes ► FCALPhysicsList : Standard Particles and Physical Processes defined ► FCALPrimaryGeneratorAction: Definition of X, Y, Z, cos_X, cos_Y, cos_Z for electrons inside tracks_20GeV.dat, tracks_40GeV.dat, tracks_80GeV.dat and tracks_200GeV.dat in files of 1000 events each. particleRun ->SetParticlePosition particleRun ->SetParticleMomentumDirection Defined following parameter definitions inside those files Standard advanced examples design for the rest of classes 8

9. Simulation of FCAL Module 0 with Geant4 Visualization Development with OpenGL All visualization packages included in FCALVisManager class Initialization of the drawing via: (interactively) idle> /control/execute vis.mac Front View of the System 9

10. Simulation of FCAL Module 0 with Geant4 5.0.6. Anaphe Implementation of the Aida 3.0 Histograms MakeFile as simple as possible ifdef G4ANALYSIS_USE CPPFLAGS += 'aida-config --include' LDFLAGS += 'aida-config --lib' Sourcing some startup scripts at CERN setenv G4ANALYSYS_USE 1 setenv PATH ${PATH}: /afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts source /afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts ln -s /afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts/* ~/bin/. (just once after the source) The example has been tested using the gcc-2.95.2 compiler inside CERN RedHat 6.1 and 7.3 10

11. Results of the Simulation Histograms and Ntuples The example produces 6 histograms and ntuples saved in “fcal.his ” Group of histos and ntuples to show the AIDA mechanismus: (included in last release) Histo1 and Ntuple1 —— > Number of Tracks out of World Histo2 and Ntuple2 —— > Number of Secondary Particles Histo3 and Ntuple3 —— > Deposited Energy in FCAL1 Histo4 and Ntuple4 ——> Deposited Energy in FCAL2 Group of histos and ntuples to compare with data of 1998 test beam: (to include in next release) Histo5 and Ntuple5 ——> Reconstructed Energy in FCAL1 Histo6 and Ntuple6 —— > Reconstructed Energy in FCAL2 11

12. Results of the Simulation Comparison between Geant4 and TestBeam Data'98 Characteristics of the simulation: ♣ Variable to study: Energy deposited in FCAL1 and FCAL2 in the liquid argon of the tube electrode summed into tiles ♣ TestBeam data: ntuples of 5000 events each for 20, 40, 60 and 80 GeV ♣ Initial Simulation Conditions: 1000 electrons are jetted at beam energies of 20, 40, 60 and 80 GeV ♣ Range cut for secondary particles production: 1 mm ♣ Important effects to take into account: noise and digitization has to be parameterized inside the simulation 12

13. Results of the Simulation Definition of the variable inside the Simulation E tile rec = c MC x E tile vis + E noise (defined by event) E rec (per event) = Σ E tile rec c MC = Monte Carlo electron calibration constant: 1/C MC = / Cuts 0.5mm 1.0mm 2.0mm c MC [%] 1.42 1.41 1.36 E tile vis = row electron signal recollected in each tile of the module E dep = Total energy deposited inside the module: E dep = E beam – E loss E loss = Energy losses outside the module E noise = correction factor calculated by gaussian smearing centered at 0 and a width of 8 GeV 13

14. Results of the Simulation 14 Statistical Test (Thanks to statistics testing team) Code design to compare Data with Simulation by a p-value test: Probability that both histos are compatible Test performed for FCAL1 Reconstructed Energy to 20, 40 and 60 GeV

15. Results of the Simulation 15

16. Results of the Simulation 16 Chi2 ≈ 300 n.d.f< 90 p-value quite small p-value very small due to an understimation of the statistical error from test beam data Quite important for these tests a good error estimation Further factors to take into accout: 1. Low energy electrons not considered into simulation 2. Constant smearing factor for all events into simulation

17. Summary 17 ♠ A simulation for the module 0 of the lAr calorimeter for the ATLAS detector has been successfully performed with the Geant4 toolkit ♠ Test beam'98 setup included in the simulation ♠ Results included in a Geant4 advanced example ♣ The statistical test results here presented are preliminary, still to be tested ♣ Only FCAL1 reconstructed energy has been checked in the comparison, further data variables have to be included in the whole analysis ♣ 2003 summer data must be tested in the simulation