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MC Generation, Simulation and Reconstruction

Step 1: Generating MC event swith PYTHIA

To produce python files which generate, simulate and reconstruct we use the cmsDriver.py procedure. The generation phase uses special pythia card files to produce a python file which can be run with cmsRun. You can find a large list of example cards in the directory Configuration/GenProduction/python.

1) Use cmsDriver.py to make a executable python file

Use the following commands:

cmsDriver.py "your card file's name" -s GEN,SIM \
--conditions auto:mc \
--datatier GEN-SIM \
--eventcontent RAWSIM \
--beamspot Realistic7TeV2011Collision \
--no_exec

You will need to include the following line of code anywhere after the Configuration.StandardSequences.Services_cff is loaded:

process.RandomNumberGeneratorService.generator.initialSeed = cms.untracked.uint32(##RANDOMSEED##)

where you replace ##RANDOMSEED## with a random number. For those of you used to running on CRAB, this was done automatically, but for running locally it must be done by hand.

*N.B. The --beamspot tag is for the 7TeV 2011 collisions, there is probably a new thing named: Realistic8TeV2012Collision, but I'm not sure.

After you do that you will get some messages and then a new file will be produced in the directory you're working with with "the name of your Pythia card file".py. Inside this file you will find a place to:

a) Change the numbers of events (this can be done at the cmsDriver.py stage, but I don't see the reason why)
b) Edit the PYTHIA information
c) Chage the output file name and location

2) Running a generation job with cmsRun

I suggest you do all three and run a small job (100 evts) using the command:

cmsRun "your file's name".py

The next step does the digitization and is also the step to add pile up.
Go on to step 2: Simulating and digitizing MC events

Christopher Edward Justus

Last modified: Tue May 18 14:15:15 PDT 2010