/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_5_3_14/src/RecoJets/JetAssociationAlgorithms/src/JetTracksAssociationDRVertex.cc

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// Associate jets with tracks by simple "dR" criteria
// Fedor Ratnikov (UMd), Aug. 28, 2007
// $Id: JetTracksAssociationDRVertex.cc,v 1.4 2010/03/18 12:17:58 bainbrid Exp $

#include "RecoJets/JetAssociationAlgorithms/interface/JetTracksAssociationDRVertex.h"

#include "DataFormats/JetReco/interface/Jet.h"
#include "DataFormats/TrackReco/interface/Track.h"

#include "DataFormats/Math/interface/deltaR.h"
#include "DataFormats/Math/interface/Vector3D.h"


JetTracksAssociationDRVertex::JetTracksAssociationDRVertex (double fDr) 
: mDeltaR2Threshold (fDr*fDr)
{}

void JetTracksAssociationDRVertex::produce (reco::JetTracksAssociation::Container* fAssociation, 
                                         const std::vector <edm::RefToBase<reco::Jet> >& fJets,
                                         const std::vector <reco::TrackRef>& fTracks) const 
{
  // cache tracks kinematics
  std::vector <math::RhoEtaPhiVector> trackP3s;
  trackP3s.reserve (fTracks.size());
  for (unsigned i = 0; i < fTracks.size(); ++i) {
    const reco::Track* track = &*(fTracks[i]);
    trackP3s.push_back (math::RhoEtaPhiVector (track->p(),track->eta(), track->phi())); 
  }
  //loop on jets and associate
  for (unsigned j = 0; j < fJets.size(); ++j) {
    reco::TrackRefVector assoTracks;
    const reco::Jet* jet = &*(fJets[j]); 
    double jetEta = jet->eta();
    double jetPhi = jet->phi();
    for (unsigned t = 0; t < fTracks.size(); ++t) {
      double dR2 = deltaR2 (jetEta, jetPhi, trackP3s[t].eta(), trackP3s[t].phi());
      if (dR2 < mDeltaR2Threshold)  assoTracks.push_back (fTracks[t]);
    }
    reco::JetTracksAssociation::setValue (fAssociation, fJets[j], assoTracks);
  }
}