Category "parameterisations/gflash"

These examples demonstrate the use of the GFLASH parameterisation library. They use the GFLASH equations (hep-ex/0001020, Grindhammer & Peters) to parametrise electromagnetic showers in matter. In these examples the calorimeter is a simple cube, which consists of 10 x 10 crystals of PbWO4 (CMS like).

Briefly, whenever a e-/e+ enters the calorimeter, it is parametrised if it has a minimum energy and the shower is expected to be contained in the calorimeter (so called " parameterisation envelope"). If this is fullfilled the particle is killed, as well as all secondaries, and the energy is deposited according to the GFLASH equations.

The examples show how to interface GFLASH to your application. The simulation time is measured, so the user can see immediately the speed up by using GFLASH.

Geometry and parametrisation is defined in different ways in the set of three equivalent (in terms of produced showers) examples: gflash1, gflash2 and gflash3, to demonstrate how to use the parametrisation, sensitive detectors and parallel geometry. The classes which are the same in all three examples have the names with ExGflash prefix while the names of classes specific to each example have the prexix ExGflash[1,2,3].

The gflasha example - allow histogramming of show profiles and fine tuning of gflash parametrization for homogeneous medium.

Note: Instead of particle gun the gps class is used here for particle generation.

Briefly

Table below presents in which world/geometry (mass or parallel) each of the elements is defined.

Example	gflash1	gflash2	gflash3
Block of material	mass geo	mass geo	mass geo
Crystals (readout geometry)	mass geo	mass geo	parallel geo
Sensitive detector	mass geo	mass geo	parallel geo
Envelope for parametrisation	mass geo	parallel geo	mass geo

Example gflash1:

Uses only the mass geometry, with each crystal defined as a volume, with parametrisation attached to the envelope in the mass geometry. Geometry and sensitive detector are defined in:

• ExGflash1DetectorConstruction
• ExGflash1SensitiveDetector

Example gflash2:

Uses mass geometry to create volumes and to create a sensitive detector for storing hits, but parametrisation is attached to the envelope in the parallel geometry (see also examples/extended/parametrisations/Par01). Geometry and sensitive detector are defined in:

• ExGflash2DetectorConstruction
• ExGflash2ParallelWorld
• ExGflash2SensitiveDetector

Example gflash3:

Uses mass geometry to create the main volume (homogeneous material) and use it as an envelope for the parametrisation, but the readout geometry (crystals) are defined in the parallel geometry, together with the sensitive detector to store the hits. Geometry and sensitive detector are defined in:

• ExGflash3DetectorConstruction
• ExGflash3ParallelWorld
• ExGflash3SensitiveDetector

Details of implementation:

Example gflash1:

To use GFLASH the user has to implement the following:

• ExGflash1DetectorConstruction::ConstructSDandField() :
  Here GFLASH has to be initialized and assigend to the envelope, where it should be active (here our calorimeter = caloLog )

  // **********************************************
  // * Initializing shower modell
  // ***********************************************
  G4cout << "Creating shower parameterization models" << G4endl;
  fFastShowerModel = new GFlashShowerModel("fFastShowerModel", fRegion);
  fParameterisation = new GFlashHomoShowerParameterisation(pbWO4);
  fFastShowerModel->SetParameterisation(*fParameterisation);
  fParticleBounds = new GFlashParticleBounds();
  fFastShowerModel->SetParticleBounds(*fParticleBounds);
  fHitMaker = new GFlashHitMaker();
  fFastShowerModel->SetHitMaker(*fHitMaker);
  G4cout<<"end shower parameterization."<<G4endl;
  // **********************************************

• ExGflash1SensitiveDetector:
  It is mandatory to use G4VGFlashSensitiveDetector as (additional) base class for the sensitive detector. Here it is necessary to implement a seperate interface, where the GFlash spots are processed. (ProcessHits(G4GFlashSpot*aSpot ,G4TouchableHistory* ROhist)) The separate interface is used, because the GFLASH spots contains (naturally) less information than the full simulation.

Example gflash2:

• ExGflash2.cc: Parallel world needs to be registered; Fast simulation is activated for parallel world (where envelope is);
• ExGflash2DetectorConstruction: Only main geometry and SD are created;
• ExGflash2ParallelWorld: Construction of identical volume for the main box as in the mass geometry, but with dummy material (it is not used anyway); Creation of G4Region associated to G4LogicalVolume; Initialization of GFlash, attaching it to the envelope (G4Region);
• ExGflash2SensitiveDetector: Uses pointer to ExGflash2ParallelWorld to get the crystals for the readout;

Example gflash3:

• ExGflash3.cc: Parallel world needs to be registered; Physics of the parallel world needs to be registered so sensitive detector can collect hits; Fast simulation is activated for mass world (where envelope is);
• ExGflash3DetectorConstruction: Only main volume (box) with material is created; Creation of G4Region associated to G4LogicalVolume of that box; Initialization of GFlash, attaching it to the envelope (G4Region);
• ExGflash3ParallelWorld: Construction of identical volume for the main box as in the mass geometry, but with dummy material (it is not used anyway); Construction of individual crystals for the readout geometry; Creation of the sensitive detector;
• ExGflash3SensitiveDetector: Uses pointer to ExGflash3DetectorConstruction to get the crystals for the readout;

Macros

• vis.mac - macro for use in interactive mode (default, if no arguments are specified)
• test.mac - macro for tests: 50 GeV electrons are shot in the direction of the detector (along z axis), 10 times. As they enter the parametrisation envelope, the GFlash parametrisation is invoked and energy is deposited. The results are printed out:
  • energy in the most central crystal
  • energy in 3x3 crystals
  • energy in 5x5 crystals
  • number of created deposits
  • simulation time per event