Running GSIM CLAS simulation

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GSIM Inventory

  • GSIM directory is to be located on the farm, at a large enough work disk. An example of the simulation inventory can be found at
 /work/halla/e07006/disk1/Erez/GSIM  (will be used for the remainder of the documentation as $GSIM)

Running GSIM

Setting an Event Generator and create events file

  • PYTHIA is used as the base-line event generator (EG) for GSIM
  • The existing EG is a fortran script located under $GSIM/Documents/ directory.

Setting Event Generator

  • The EG should be modified for the specific solid target. An example for 12C can be found at
  • To build the event generator use the build compilation command, e.g.
 cd  $GSIM/Documents/

(the result: an executable event generator e.g. EventGenerator_exe/EG_C.exe)

Generate the Events

  • Generate the events by executing the EG, e.g.
 ./EG_C.exe > test.dat

(the result: a data file EventGenerator_exe/test.dat)

Look at the generated distributions

  • A utility for observing the generated data exist in the main EG directory $GSIM/Documents/EventGenerator/LeptoRoot
  • Port the data file into the utility directory
 cp $GSIM/Documents/EventGenerator_exe/test.dat $GSIM/Documents/LeptoRoot/
  • A perl script is used to write it in the right format
 ./ < test.dat > data.dat 

(the result: a different (just numbers) data file LeptoRoot/data.dat)

  • An executable is then used to write the data into a ROOT TTree

(the result: a ROOT file LeptoRoot/data.root that will enable you to observe the generated distributions)

Converting generated data files to GEANT-3 format input

  • port the generated-events data file (in this example test.dat) to the converters utility and convert it to txt format.

For example, a file from the 2H target would be converted by

 cp $GSIM/Documents/EventGenerator_exe/test.dat $GSIM/converters
 ./convert_deut < test.dat > convert_output.dat

(the result: a txt file /converters/convert_output.dat )

  • port and convert the txt file to a G3 part format corresponding to the MCTK bank (works better than particle bank in G3)
 mv convert_output.dat  ../Lepto64
 cd ../Lepto64
 ./txt2part -m -omctk.evt < convert_output.dat 

(the result: a part file /Lepto64/mctk.evt suitable for GSIM)

Running generated events through a CLASS GEANT-3 simulation

running GSIM with the generated events

Preprocessing to add smearing of the data

Look at the output files

Converting the GSIM output file to root

Observing the output ROOT TTree

[back to Tel Aviv University SRC Group]