TrackAssociatorByChi2.h

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#ifndef TrackAssociatorByChi2_h
#define TrackAssociatorByChi2_h

#include "SimTracker/TrackAssociation/interface/TrackAssociatorBase.h"
#include "SimDataFormats/Track/interface/SimTrackContainer.h"
#include "FWCore/Framework/interface/ESHandle.h"
#include "MagneticField/Engine/interface/MagneticField.h" 
#include "MagneticField/Records/interface/IdealMagneticFieldRecord.h" 
#include "FWCore/Framework/interface/EventSetup.h"
#include "SimDataFormats/Vertex/interface/SimVertexContainer.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "DataFormats/Math/interface/LorentzVector.h"
#include "DataFormats/BeamSpot/interface/BeamSpot.h"
#include "FWCore/Utilities/interface/InputTag.h"

#include<map>

//Note that the Association Map is filled with -ch2 and not chi2 because it is ordered using std::greater:
//the track with the lowest association chi2 will be the first in the output map.

class TrackAssociatorByChi2 : public TrackAssociatorBase {

 public:
  typedef std::map<double,  SimTrack> Chi2SimMap;
  typedef std::pair< reco::Track, Chi2SimMap> RecoToSimPair;
  typedef std::vector< RecoToSimPair > RecoToSimPairAssociation;

  TrackAssociatorByChi2(const edm::ESHandle<MagneticField> mF, const edm::ParameterSet& conf):
    chi2cut(conf.getParameter<double>("chi2cut")),
    onlyDiagonal(conf.getParameter<bool>("onlyDiagonal")),
    bsSrc(conf.getParameter<edm::InputTag>("beamSpot")) {
    theMF=mF;  
    if (onlyDiagonal)
      edm::LogInfo("TrackAssociator") << " ---- Using Off Diagonal Covariance Terms = 0 ---- " <<  "\n";
    else 
      edm::LogInfo("TrackAssociator") << " ---- Using Off Diagonal Covariance Terms != 0 ---- " <<  "\n";
  }

  TrackAssociatorByChi2(const edm::ESHandle<MagneticField> mF, double chi2Cut, bool onlyDiag, const edm::InputTag& beamspotSrc){
    chi2cut=chi2Cut;
    onlyDiagonal=onlyDiag;
    theMF=mF;  
    bsSrc = beamspotSrc;
  }

  ~TrackAssociatorByChi2(){}


  virtual
  reco::RecoToSimCollection associateRecoToSim(const edm::RefToBaseVector<reco::Track>&,
                           const edm::RefVector<TrackingParticleCollection>&,
                           const edm::Event * event = 0,
                                               const edm::EventSetup * setup = 0 ) const override;
  virtual
  reco::SimToRecoCollection associateSimToReco(const edm::RefToBaseVector<reco::Track>&,
                           const edm::RefVector<TrackingParticleCollection>&,
                           const edm::Event * event = 0,
                                               const edm::EventSetup * setup = 0 ) const override;
  
  virtual
  reco::RecoToSimCollection associateRecoToSim(edm::Handle<edm::View<reco::Track> >& tCH, 
                           edm::Handle<TrackingParticleCollection>& tPCH, 
                           const edm::Event * event = 0,
                                               const edm::EventSetup * setup = 0) const override {
    return TrackAssociatorBase::associateRecoToSim(tCH,tPCH,event,setup);
  }
  
  virtual
  reco::SimToRecoCollection associateSimToReco(edm::Handle<edm::View<reco::Track> >& tCH, 
                           edm::Handle<TrackingParticleCollection>& tPCH,
                           const edm::Event * event = 0,
                                               const edm::EventSetup * setup = 0) const override {
    return TrackAssociatorBase::associateSimToReco(tCH,tPCH,event,setup);
  }  


 private:

  std::pair<bool,reco::TrackBase::ParameterVector> parametersAtClosestApproach(const Basic3DVector<double>&,// vertex
                                           const Basic3DVector<double>&,// momAtVtx
                                           float,// charge
                                           const reco::BeamSpot&) const;//beam spot

  double compareTracksParam(reco::TrackCollection::const_iterator, 
                edm::SimTrackContainer::const_iterator, 
                const math::XYZTLorentzVectorD&, 
                const GlobalVector&,
                const reco::TrackBase::CovarianceMatrix&,
                const reco::BeamSpot&) const;

  RecoToSimPairAssociation compareTracksParam(const reco::TrackCollection&, 
                          const edm::SimTrackContainer&, 
                          const edm::SimVertexContainer&,
                          const reco::BeamSpot&) const;

  double getChi2(const reco::TrackBase::ParameterVector& rParameters,
         const reco::TrackBase::CovarianceMatrix& recoTrackCovMatrix,
         const Basic3DVector<double>& momAtVtx,
         const Basic3DVector<double>& vert,
         int charge,
         const reco::BeamSpot&) const;

  double associateRecoToSim(reco::TrackCollection::const_iterator,
                TrackingParticleCollection::const_iterator,
                const reco::BeamSpot&) const;


  edm::ESHandle<MagneticField> theMF;
  double chi2cut;
  bool onlyDiagonal;
  edm::InputTag bsSrc;
};

#endif