Running GSIM CLAS simulation

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

 $GSIM/Documents/EventGenerator/src/qp1C.f

• To build the event generator use the build compilation command, e.g.

 cd  $GSIM/Documents/
 build_EG_cs

(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

 ./leptoroot.pl < 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

 ./leptoroot 

(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)

Observing the output ROOT TTree

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