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
 $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)


Running generated events through a CLASS GEANT-3 simulation

running GSIM with the generated events

  • port the events file to the shared directory
 mv mctk.evt share
 cd share
  • to run the first XXXX events through the simulation, modify the ffread file so that it triggers XXXX events
  • then source the shell script that runs GSIM
 ./gsim_test.csh

(the result: 2 bos + 1 txt files , gsimtest.txt, gsimtest.bos, gpp_test.bos and the output file outfile1 )

  • gsimtest.bos contains the data 'collected' by CLASS (ADC/TDC)
  • gpp_test.bos incorporates preprocessing to add smearing of the data
  • outfile1 is the physical data after REConstruction SYStem analyzed it


Look at the output files

  • using COUNTBS one could count the number of events, e.g.
 ./countbs gsimtest.bos

(Note the first additional two events are header and are not to be accounted)

  • using BOSDUMP code, one can look at the data from the terminal, e.g.
 ./bosdump gsimtest.bos
 ./bosdump gpp_test.bos


Converting the GSIM output file to ROOT

  • this is the easy part now. For an output file named outfile1 e.g., use
 ./WriteRootDst -o output.root -GSIM outfile1

(the result: a root file /output.root)


Observing the output ROOT TTree

  • The ROOT TTree is called
 CLASEVENT
  • To look at the data use e.g.
 CLASEVENT -> StartViewer()
  • The 'collected data' is stored in EVNT.XXXX variables, while the generated data is stored in GSIM.XXXX variables.


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