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 would be 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 would be 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 would be a different (just numbers) data file LeptoRoot/data.dat)

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

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

Converting generated data files to GEANT-3 format input

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

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