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)

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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