LCDG4: a Geant4-based detector simulator for the LCD

Guilherme Lima

for the NICADD simulations group

Geant4 TutorialFermilab, Oct.28 2003

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Outline NICADD Linear Collider and LCD Detector simulation

Requirements Implementation details Event displays Status

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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

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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

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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

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Options under study: SD, LD, PD

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A Digital Hadronic Calorimeter?

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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

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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

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Geant4 implementation G4RunManager

UserInitialization PhysicsList LCDXML2G4DetConst (detector construction)

UserAction LCDG4PrimaryGeneratorAction LCDG4EventAction LCDG4SteppingAction LCDG4TrackingAction

G4VisManager G4UIManager

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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

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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

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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>

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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

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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

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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

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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

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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

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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

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e+e- → Z → +- (SDJan03)

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e+e- → tt event (SDJan03)

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e+e- → Z → qq event (SDJan03)

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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