GeMSE_MC

Geant4 code to simulate the GeMSE detector efficiency

Compilation

If you are sitting on top of the GeMSE_environment, run:

git clone https://github.com/AG-Schumann/GeMSE_MC.git
cd GeMSE_MC
source /opt/GeMSE/setup_sims.sh
make -j # "-j" for parallel compilation using all available CPU

and your executables will be built under ./bin/Linux-g++/GeMSE_MC, where . is the default working directory ($G4WORKDIR).

If running locally, make sure you have ROOT and Geant4 (10.3 recommended) installed. Compilation errors will arise because of the nonexistent paths that the CADMesh.hh class needs to execute. You can either install these extra libraries (ask Diego) or just run the code without CADMesh, assuming you do not want to simulate a 3D sample. In order to do that:

• remove the include/CADMesh.hh file from its directory,
• comment out these lines from the top of the src/GeMSE_DetectorConstruction.cc file:

  #define USE_CADMESH_TETGEN // To use tetgen
  #include <CADMesh.hh>

• comment out these two lines from the Makefile

  EXTRALIBS +=/opt/GeMSE/assimp/bin/libassimp.so
  EXTRALIBS +=/opt/GeMSE/tetgen/tetlib.so

and you're ready to go:

git clone https://github.com/AG-Schumann/GeMSE_MC.git
cd GeMSE_MC
export G4WORKDIR=${PWD} # optional, otherwise defaulted to /home/<username>/geant4workdir/
make -j # "-j" for parallel compilation using all available CPU

Execution

Run the executable with:

$G4WORKDIR/bin/Linux-g++/GeMSE_MC -m <macrofile.mac> -o <results_folder> -g <sample_geometry.txt>

where the -g option is only for the cases in which you define your sample shape via txt file (see sample_geometries README).

macrofile.mac

• Contains the information which isotopes or gamma lines are simulated
• See example [macros/ efficiency_standard_isotopes_G4103p3.mac ](macros/ efficiency_standard_isotopes_G4103p3.mac ), where the various output tree option commands and gamma efficiency settings are explained.
• For visualization only use macros/<visualization_macro.mac> (no need for -o argument in this case).

results_folder

• Folder where result files are written. No output will be written if this argument is not specified

Output format

The simulation output is a *.root file with several layers of information:

• TNamed G4VERSION_TAG, with the information on the Geant4 version used during the run
• TNamed MCVERSION_TAG, with the information on the GeMSE_MC version used during the run
• TTree RunInfo: tree with basic run information
  • TBranch nEvents: number of simulated events
  • TBranch nDecays: number of primary decays in the run (i.e., decays on the primary particle)
  • TBranch RunTime: guess what
  • TBranch Seed: random seed of the run, so that you can reproduce it
• TTree tree: tree with information about detection efficiency and branching ratio (emission probability) for every gamma line chosen (empty branches if no /gammaline/ commands are provided in the run macro)
  • TBranch energy: energy of gamma line
  • TBranch efficiency: detection efficiency
  • TBranch efficiency_err: statistical uncertainty of detection efficiency
  • TBranch eff_BR: product of detection efficiency and branching ratio
• TTree GeHits: tree with information on every particle hit (energy deposit > 0) in the Ge
  • TBranch EventID: run event id
  • TBranch NHits: number of Ge hits for a given event
  • TBranch TotEdep: total energy deposit in the Ge crystal for a given event
  • TBranch TrackID: id of the tracks producing the hits in the Ge crystal
  • TBranch ParticleID: Geant4 particle identifier for the hits
  • TBranch Edep: energy deposit of the individual hits
  • TBranch xPos, yPos, zPos: position of the individual hits
  • TBranch Time: time of the individual hits
  • TBranch Ekin: kinetic energy of the particle at the time of the hit
• TTree MuonHits: tree with information on every particle hit in the muon veto panels
  • Contains the exact same branches as the GeHits tree, with the addition of PanelNr, to extract the information on the panel that saw the hit (0 for top, 1 for side panel).
• TTree Primaries: Tree with information on all generated particles in the run (deactivated by default, add /writePrimaries true to your macro to fill the branches below)
  • TBranch EventID
  • TBranch TrackID
  • TBranch ParentID: run id of the parent particle
  • TBranch xPriPos, yPriPos, zPriPos: primary position
  • TBranch Ekin
  • TBranch ParticleID
  • TBranch xDir, yDir, zDir: initial momentum direction

Note: The tree tree must keep that name for backwards compatibility with simulations and analysis scripts.

Import 3D CAD samples

The CADMesh interface, specifically v2.0.3 is integrated into this code. This means that one can import CAD samples in STL, PLY or OBJ format into Geant4 for their construction. See an example in sample_geometries/banana_scan.cc.

Note: Contrary to the CADMesh version used up to (and including) GeMSE_MC v1.2.0, this one does not support binary STL files (see sample_geometries/scans_3d/banana_LRT_talk_binary.stl). These can be converted to ASCII using commercial CAD software.