/data/refman/pasoursint/CMSSW_4_1_8_patch12/src/RecoJets/JetAlgorithms/src/PrunedRecombiner.cc

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//
// PrunedRecombiner.cc
// Last update: 5/28/09 CKV
// PrunedRecomb version: 0.2.0
// Author: Christopher Vermilion <verm@u.washington.edu>
//
// Implements the PrunedRecombiner class.  See PrunedRecombiner.hh
//

#include "PrunedRecombPlugin.h"

#include <string>
#include <sstream>
#include <iostream>

FASTJET_BEGIN_NAMESPACE

std::string PrunedRecombiner::description() const
{
        std::ostringstream s;
        s << "Pruned " << JetDefinition::DefaultRecombiner::description()
          << ", with zcut = " << _zcut << " and Rcut = " << _Rcut;
        return s.str();
}       
        
void PrunedRecombiner::recombine(const PseudoJet & pa, const PseudoJet & pb, 
                           PseudoJet & pab) const
{
        //std::cout << "In PR::recombine()\n";
        PseudoJet p0(0.0, 0.0, 0.0, 0.0);
        // test if recombination should be pruned
        switch ( _pruning_test(pa, pb) ) {
                case 1:
                        // MAKE RECORD OF PB BEING PRUNED
                        JetDefinition::DefaultRecombiner::recombine(pa, p0, pab);
                        break;
                case 2:
                        // MAKE RECORD OF PA BEING PRUNED
                        JetDefinition::DefaultRecombiner::recombine(pb, p0, pab);
                        break;
                default: 
                        // if no pruning, do regular combination
                        JetDefinition::DefaultRecombiner::recombine(pa, pb, pab);
        }
}

                
// Function to test if two pseudojets should be merged -- ie, to selectively
//   veto mergings.  Should provide possibility to provide this function...
//   Return codes:
//
//   0: Merge.  (Currently, anything other than 1 or 2 will do.)
//   1: Don't merge; keep pa
//   2: Don't merge; keep pb 
//
int PrunedRecombiner::_pruning_test(const PseudoJet & pa, const PseudoJet & pb) const
{
        // create the new jet by recombining the first two, using the normal
        //   recombination scheme
        PseudoJet newjet;       
        JetDefinition::DefaultRecombiner::recombine(pa, pb, newjet);

        double minpT = pa.perp();
        int hard = 2;  // harder pj is pj2
        double tmp = pb.perp();
        if (tmp < minpT) {
                minpT = tmp;
                hard = 1;  // harder pj is pj1
        }
        
        if ( pa.squared_distance(pb) < _Rcut*_Rcut 
              || minpT > _zcut * newjet.perp() )
                return 0;
        else
                return hard;
}


FASTJET_END_NAMESPACE