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LCDG4: a Geant4-based detector simulator for the LCD

LCDG4: a Geant4-based detector simulator for the LCD. Guilherme Lima for the NICADD simulations group. Geant4 Tutorial Fermilab, Oct.28 2003. Outline. NICADD Linear Collider and LCD Detector simulation Requirements Implementation details Event displays Status. NICADD.

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LCDG4: a Geant4-based detector simulator for the LCD

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  1. LCDG4: a Geant4-based detector simulator for the LCD Guilherme Lima for the NICADD simulations group Geant4 Tutorial Fermilab, Oct.28 2003

  2. Outline • NICADD • Linear Collider and LCD • Detector simulation • Requirements • Implementation details • Event displays • Status

  3. NICADD • Northern Illinois Center for Accelerator and Detector Development • Research and Developments for the next Linear Collider (LC) • Detectors: design, development, prototyping, testing and construction of a sampling, scintillator-based digital hadronic calorimeter • Simulation and software developments by Dhiman Chakraborty (coordinator), Guilherme Lima, Jeremy McCormick, Vishnu Zutshi • More information at http://nicadd.niu.edu

  4. Linear Collider • Electron-positron collisions at 500 to 1000 GeV • Luminosities of 1034 cm-2 s-1 • Physics motivation: Precision studies: Higgs, supersymmetry and other new phenomena • Possible e-e-, e-g and gg configurations • Accelerator technology and site not yet chosen • Start date: around 2015 • Overlap with LHC is desirable

  5. Detector geometry SDJan03 • Some versions under study • SD detector • LD detector • PD detector • Detector components • VXD (vertex detector) • Tracker • EM calorimeter • Hadronic calorimeter • Luminosity detector • Solenoid coil • Muon system

  6. Options under study: SD, LD, PD

  7. A Digital Hadronic Calorimeter?

  8. Simulation of a digital HCal • High segmentation for better energy resolution: one bit (digital) or two bits (semidigital) per cell • Questions to be addressed • Cell shapes (squares, rectangles, hexagons) • Cell dimensions (digital calorimeter) • Projective vs. non-projective calorimeters • Sampling fractions (number of layers, active to absorber ratios) • Cost / performance optimization

  9. Detector Simulation • Support the detector design activities at NICADD • Useful tool for the whole LCD collaboration • Some basic requirements: • Flexible geometry description • Input from binary STDHEP • Output in LCD-specific formats (sio, lcio) • Hits should be associated to MC particles

  10. Geant4 implementation • G4RunManager • UserInitialization • PhysicsList • LCDXML2G4DetConst (detector construction) • UserAction • LCDG4PrimaryGeneratorAction • LCDG4EventAction • LCDG4SteppingAction • LCDG4TrackingAction • G4VisManager • G4UIManager

  11. PhysicsList Basically inherited from Mokka (See http://polype.in2p3.fr/geant4/tesla/www/mokka/mokka.html) • GeneralPhysics charged, neutral geantinos, and all decays • EMPhysics e+, e-, g, ne, ne • HadronPhysicsLHEP G4 Meson, Barion and ShortLived constructors • MuonPhysics muons and taus • IonPhysics G4IonConstructor, Deuteron, Triton, Alpha, 3He

  12. LCDXML2G4DetConst • Detector construction from XML input file • XML parsing is done by Sun’s xercesc library • Limitation: cylinders or disks only • Uses other classes to do the real work: • LCDXML2G4VXD • LCDXML2G4Tracker • LCDXML2G4Lum • LCDXML2G4EMCal • LCDXML2G4HDCal • LCDXML2G4Muon • LCDG4MaterialMgr • LCDXML2G4Field • LCDXML2G4InactiveVolume

  13. XML detector description <?xml version="1.0" ?> <!-- SDJan03.xml - Standard Silicon Detector --> <!DOCTYPE lcdparm SYSTEM "detParms.dtd" > <lcdparm> <global file="SDJan03.xml" /> <physical_detector topology="silicon" id = "SDJan03" > <-- Just an example: description of the HCal barrel --> <volume id="HAD_BARREL" rad_len_cm="1.133" inter_len_cm="0.1193"> <tube> <barrel_dimensions inner_r = "144.0" outer_z = "286.0" /> <layering n="34"> <slice material = "Stainless_steel" width = "2.0" /> <slice material = "Polystyrene" width = "1.0" sensitive = "yes“ /> </layering> <segmentation cos_theta = "600" phi = "1200" /> </tube> <calorimeter type = "had" /> </volume> <-- all other volumes dropped... --> </physical_detector> </lcdparm>

  14. LCDG4PrimaryGeneratorAction • Inherits from G4VUserPrimaryGeneratorAction • LCDG4readStdFile for binary StdHEP input file • A Geant4 primary track is created for each MC particle in the input file • LCDMcPart keeps track of parents and some additional information (one for each track, except for tracks produced inside a calorimeter shower) • LCDG4Trk2McPart inherits from G4VUserTrackInformation and associates one or more G4Tracks to one LCDMcPart • Standard G4ParticleGun can also be used • LCDG4PrimaryGeneratorMessenger can be used for simple interactive changes to the G4ParticleGun generator

  15. LCDG4TrackingAction • Inherits from G4UserTrackingAction • Builds the associations between parents and children, so that all hits can be traced back to a MC particle saved in output file • It does this by creating an LCDG4Trk2McPart object for each secondary particle created by Geant during tracking

  16. LCDG4SteppingAction • Inherits from G4UserSteppingAction • It complements LCDG4TrackingAction by creating LCDMcPart objects for non-primary particles (except for particles from calorimeter showers) • It is also used for geantino scans, to calculate accumulated radiation and interaction lengths along straight lines

  17. LCDG4EventAction • Accesses all hit collections (G4HCofThisEvent) and streams hits and MC particles into output format • Output formats are LCD-specific (sio and lcio) • Data format keeps links between different objects, like hits associated to MC particles • Some limited ASCII output can be used for debugging purposes

  18. Hit Processing • LCDG4HDCalSD inherits from G4VSensitiveDetector • Determines which cell was hit based on the PreStepPoint coordinates (virtual cells!) • LCDG4HDCalHit keeps track of hit information in each individual cell. It inherits from G4VHit • Energy deposition is linked to the MC particle • Energy deposition in absorbers are also kept for analysis • Similar classes exist for each subcomponent

  19. Projective vs. Non-projective • An important parameter to be studied at the earlier stages of the design • Mokka doesn’t currently have this functionality Projective Non-projective

  20. e+e- → Z → m+m- (SDJan03)

  21. e+e- → tt event (SDJan03)

  22. e+e- → Z → qq event (SDJan03)

  23. Status • Detailed comparisons between LCDG4 and Mokka under way • Only cylinders and disks currently supported • Plans to upgrade from XML to GDML • Other Geant4 projects: • NICADD test stand • Test beam prototype (see Jeremy’s talk!) • For more information, please check: http://nicadd.niu.edu/research/lcd

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