Event Generators

Event Generator Framework
Example macros for running event generators + starsim in ROOT:
$ cvs co StRoot/StarGenerator/macros
  • starsim.pythia6.C
  • starsim.pythia8.C
  • starsim.hijing.C
  • starsim.herwig.C
  • starsim.pepsi.C
  • starsim.starlight.C
  • starsim.kinematics.C
To run an example macro and generate 100 events:
$ ln -s StRoot/StarGenerator/macros/starsim.pythia8.C starsim.C
$ root4star -q -b starsim.C\(100\)
This will generate two files.  A standard "fzd" file, which can be reconstructed using the big "full" chain (bfc.C).  And a root file, containing a TTree expressing the event record for the generated events.

The new Event Record

The event-wise and particle-wise information from event generators is saved in a ROOT/TTree.  The TTree can be read in in sync with the MuDst when you perform your analysis.  The ID truth values in the reconstructed tracks in the MuDst can be compared to the primary key of the tracks in the event record to identify generator tracks which were reconstructed by the tracker.

The event record can be browsed using the standard ROOT ttree viewer.  Example for pythia 8:
root [0] TFile::Open("pythia8.starsim.root")
root [1] genevents->StartViewer()
root [2] genevents->Draw("mMass","mStatus>0")
The event record contains both particle-wise and event-wise information.  For the definitions of different quantities, see the documentation provided in the StarGenEvent links above.