An update to the post from June 29, this describes the latest version of seperating signal and background reconstructed pi0 candidates in Monte Carlo data.  Specifically, each reconstructed pair is given a "type" identifier.  These identifiers will be used for distinguishing the backgrounds and also for optimizing cuts.

Matching Gen and Rec Particles and Setting Labels

Loop over all generated ancestor particles (i.e. not the particles incident on the EEMC, but their parents, and the parents parents, and the parents grandparents, etc.)

• For each generated pi0, one finds all reconstructed pi0 candidates with
  • If there is only one reconstructed pi0 matching
    
    • Set the type to PI0_GOOD_PT if the difference in pT between generated and reconstructed is below threshold (typically 1 GeV).  Otherwise set the type to PI0_BAD_PT
  • If there are multiple reconstructed pi0s matching
    • Otherwise there are multiple reconstructed tracks, so set the type to PI0_1_TO_M (one gen. to multiple rec.)
  • If while doing the above, one finds a reconstructed candidate that already has a type involving pi0s, then the reconstructed canidate must be close to multiple generated pi0s.  Set the type to PI0_M_TO_A (multiple gen. to any number of rec.).
• For each generated photon, one finds all reconstructed pi0 candidates with
  • The photon must have converted (or caused splash back which then splashed forward).  Set the type to PHOTON_CONV

All reconstructed pi0 candidates which are not labeled by one of the above labels are give the label of OTHER_PAIR.

Note:

These are all the categories for now.  The set may be increased in the future if the need arises.

Code Source

$CVSROOT/offline/users/sgliske/StRoot/StEEmcPool/EEmcTree/Pi0TypeSolver.h

$CVSROOT/offline/users/sgliske/StRoot/StEEmcPool/EEmcTree/Pi0TypeSolver.cxx