# Presentation: 804602

## 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

- Oct. 28, 2003

## 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

## 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

## 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

## Options under study: SD, LD, PD

- Oct. 28, 2003

## A Digital Hadronic Calorimeter?

- Oct. 28, 2003

## 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

## Detector Simulation

- Support the detector design activities at NICADD
- Standard 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

## Geant4 implementation

- G4RunManager
- UserInitialization
- PhysicsList
- LCDXML2G4DetConst   (detector construction)
- UserAction
- LCDG4PrimaryGeneratorAction
- LCDG4EventAction
- LCDG4SteppingAction
- LCDG4TrackingAction
- G4VisManager
- G4UIManager

- Oct. 28, 2003

**Notes:**
A Class diagram here would be great!!

## PhysicsList

- Basically inherited from Mokka
- (See _[http://polype.in2p3.fr/geant4/tesla/www/mokka/mokka.html](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, Baryon and Short-Lived constructors
- MuonPhysics
-     muons and taus
- IonPhysics
-     G4IonConstructor, Deuteron, Triton, Alpha, 3He

- Oct. 28, 2003

## 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

## 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

## 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

## 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

## 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

## 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

## 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

## Projective vs. Non-projective

- An important parameter to be studied at the earlier stages of the design

*Projective*

*Non-projective*

- Oct. 28, 2003

## e+e- → Z → +-  (SDJan03)

- Oct. 28, 2003

## e+e- → tt event (SDJan03)

- Oct. 28, 2003

## e+e- → Z → qq event (SDJan03)

- Oct. 28, 2003

## 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

- Oct. 28, 2003