LCDG4: a Geant4-based detector simulator for the LCD Guilherme Lima for the NICADD simulations group...
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Transcript of LCDG4: a Geant4-based detector simulator for the LCD Guilherme Lima for the NICADD simulations group...
LCDG4: a Geant4-based detector simulator for the LCD
Guilherme Lima
for the NICADD simulations group
Geant4 TutorialFermilab, Oct.28 2003
Oct. 28, 2003 2
Outline NICADD Linear Collider and LCD Detector simulation
Requirements Implementation details Event displays Status
Oct. 28, 2003 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
Oct. 28, 2003 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- and configurations Accelerator technology and site not yet chosen Start date: around 2015 Overlap with LHC is desirable
Oct. 28, 2003 5
Detector geometry 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
SDJan03
Oct. 28, 2003 6
Options under study: SD, LD, PD
Oct. 28, 2003 7
A Digital Hadronic Calorimeter?
Oct. 28, 2003 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
Oct. 28, 2003 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
Oct. 28, 2003 10
Geant4 implementation G4RunManager
UserInitialization PhysicsList LCDXML2G4DetConst (detector construction)
UserAction LCDG4PrimaryGeneratorAction LCDG4EventAction LCDG4SteppingAction LCDG4TrackingAction
G4VisManager G4UIManager
Oct. 28, 2003 11
PhysicsListBasically inherited from Mokka
(See http://polype.in2p3.fr/geant4/tesla/www/mokka/mokka.html)
GeneralPhysics charged, neutral geantinos, and all decays EMPhysics
e+, e-, , e, e
HadronPhysicsLHEP G4 Meson, Barion and ShortLived constructors MuonPhysics muons and taus IonPhysics G4IonConstructor, Deuteron, Triton, Alpha, 3He
Oct. 28, 2003 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
Oct. 28, 2003 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>
Oct. 28, 2003 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
Oct. 28, 2003 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
Oct. 28, 2003 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
Oct. 28, 2003 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
Oct. 28, 2003 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
Oct. 28, 2003 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
Oct. 28, 2003 20
e+e- → Z → +- (SDJan03)
Oct. 28, 2003 21
e+e- → tt event (SDJan03)
Oct. 28, 2003 22
e+e- → Z → qq event (SDJan03)
Oct. 28, 2003 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