/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_5/src/GeneratorInterface/GenFilters/src/MCDijetResonance.cc

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#include "GeneratorInterface/GenFilters/interface/MCDijetResonance.h"

#include "SimDataFormats/GeneratorProducts/interface/HepMCProduct.h"
#include <iostream>

#include "FWCore/MessageLogger/interface/MessageLogger.h"

using namespace edm;
using namespace std;


MCDijetResonance::MCDijetResonance(const edm::ParameterSet& iConfig) :
  label_(iConfig.getUntrackedParameter("moduleLabel",std::string("generator")))
{
   //here do whatever other initialization is needed
   
   //Get dijet process type we will select
   dijetProcess = iConfig.getUntrackedParameter<string>( "dijetProcess" );
   cout << "Dijet Resonance Filter Selecting Process = " << dijetProcess << endl;
   
   maxQuarkID = 4;   //Maximum |ID| of Light Quark = charm quark gives  u, d, s, and c decays of Zprime.
   bosonID = 21;     //Gluon

   //Number of events and Number Accepted
   nEvents = 0;
   nAccepted = 0;   
}


MCDijetResonance::~MCDijetResonance()
{
 
   // do anything here that needs to be done at desctruction time
   // (e.g. close files, deallocate resources etc.)

}

void MCDijetResonance::endJob() 
{
  edm::LogVerbatim("MCDijetResonanceInfo") << "================MCDijetResonance report========================================\n" 
            << "Events read " << nEvents << " Events accepted " << nAccepted << "\nEfficiency " << ((double)nAccepted)/((double)nEvents) 
            << "\n====================================================================" << std::endl;
}

// ------------ method called to skim the data  ------------
bool MCDijetResonance::filter(edm::Event& iEvent, const edm::EventSetup& iSetup)
{
  nEvents++;
  cout << endl << "Event=" << nEvents << endl;
  using namespace edm;
  Handle<HepMCProduct> evt;
  iEvent.getByLabel(label_, evt);
  const HepMC::GenEvent * myGenEvent = evt->GetEvent();

  //If process is not the desired primary process, cleanup and reject the event.
  if (dijetProcess == "ZprimeLightQuarks" &&  myGenEvent->signal_process_id() != 141){
    // Wanted a Z' but didn't find it, so reject event.
    delete myGenEvent;
    return false;
   }
  if (dijetProcess == "QstarQuarkGluon" &&  myGenEvent->signal_process_id() != 147  &&  myGenEvent->signal_process_id() != 148){
    // Wanted a q* but didn't find it, so reject event.
    delete myGenEvent;
    return false;
   }
  
  //found a dijet resonance
  
  //debug
  // int count = 0;
  //for ( HepMC::GenEvent::particle_iterator p = myGenEvent->particles_begin();
  //    p != myGenEvent->particles_end() & count<13; ++p ) 
  // {
  //std::cout << count << ": ID=" << (*p)->pdg_id() << ", status=" << (*p)->status() << ", mass=" << (*p)->momentum().invariantMass() << ", pt=" <<(*p)->momentum().perp() << std::endl;
  //count++;
  //} 
  
  for ( HepMC::GenEvent::particle_const_iterator p = myGenEvent->particles_begin();
        p != myGenEvent->particles_end(); ++p ) 
    {
      //Find resonance particle and check that it is part of hard collision
      if ( (*p)->status() == 3 && ( (dijetProcess == "ZprimeLightQuarks" && (*p)->pdg_id() == 32)     || 
                                    (dijetProcess == "QstarQuarkGluon"   && abs((*p)->pdg_id()) == 4000001) ||
                                    (dijetProcess == "QstarQuarkGluon"   && abs((*p)->pdg_id()) == 4000002) ) )
        { 
          // The next two particles are the outgoing particles from the resonance decay
          p++;
          int ID1 = (*p)->pdg_id();
          p++;
          int ID2 = (*p)->pdg_id();

          //Check for the process we want
          if( (dijetProcess == "ZprimeLightQuarks" && abs(ID1) <= maxQuarkID  && abs(ID2) <= maxQuarkID ) ||
              (dijetProcess == "QstarQuarkGluon"   && ( ID1 ==  bosonID  || ID2 == bosonID )            )   ) 
          {
            //cout << "dijet resonance " << dijetProcess << " found " << endl; 
            nAccepted++;
            delete myGenEvent;   
            return true;
          }
          else
          {
            delete myGenEvent;   
            return false;
          }
        }

    } 

  delete myGenEvent;   
  return false;
}