/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_7/src/CommonTools/RecoUtils/src/PF_PU_AssoMapAlgos.cc

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#include "CommonTools/RecoUtils/interface/PF_PU_AssoMapAlgos.h"

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

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

#include "DataFormats/GeometryCommonDetAlgo/interface/Measurement1D.h"
#include "RecoVertex/VertexTools/interface/VertexDistance3D.h"
#include "RecoVertex/VertexPrimitives/interface/ConvertToFromReco.h"
#include "RecoVertex/VertexPrimitives/interface/VertexState.h"

#include "DataFormats/RecoCandidate/interface/RecoChargedCandidate.h"

#include "TrackingTools/IPTools/interface/IPTools.h"
#include "RecoEgamma/EgammaTools/interface/ConversionTools.h"

using namespace edm;
using namespace std;
using namespace reco;

/*************************************************************************************/
/* dedicated constructor for the algorithms                                          */ 
/*************************************************************************************/

PF_PU_AssoMapAlgos::PF_PU_AssoMapAlgos(const edm::ParameterSet& iConfig)
  : maxNumWarnings_(3),
    numWarnings_(0)
{

        input_MaxNumAssociations_ = iConfig.getParameter<int>("MaxNumberOfAssociations");

        input_VertexCollection_= iConfig.getParameter<InputTag>("VertexCollection");

        input_BeamSpot_= iConfig.getParameter<InputTag>("BeamSpot");

        input_doReassociation_= iConfig.getParameter<bool>("doReassociation");
        cleanedColls_ = iConfig.getParameter<bool>("GetCleanedCollections");
  
        ConversionsCollection_= iConfig.getParameter<InputTag>("ConversionsCollection");

        KshortCollection_= iConfig.getParameter<InputTag>("V0KshortCollection");
        LambdaCollection_= iConfig.getParameter<InputTag>("V0LambdaCollection");

        NIVertexCollection_= iConfig.getParameter<InputTag>("NIVertexCollection");

        input_FinalAssociation_= iConfig.getUntrackedParameter<int>("FinalAssociation", 0);

        ignoremissingpfcollection_ = iConfig.getParameter<bool>("ignoreMissingCollection");

        input_nTrack_ = iConfig.getParameter<double>("nTrackWeight");

}

/*************************************************************************************/
/* get all needed collections at the beginning                                       */ 
/*************************************************************************************/

void 
PF_PU_AssoMapAlgos::GetInputCollections(edm::Event& iEvent, const edm::EventSetup& iSetup)
{
  
        //get the offline beam spot
        iEvent.getByLabel(input_BeamSpot_, beamspotH);

        //get the conversion collection for the gamma conversions
        iEvent.getByLabel(ConversionsCollection_, convCollH);
        cleanedConvCollP = PF_PU_AssoMapAlgos::GetCleanedConversions(convCollH,beamspotH,cleanedColls_);

        //get the vertex composite candidate collection for the Kshort's
        iEvent.getByLabel(KshortCollection_, vertCompCandCollKshortH);
        cleanedKshortCollP = PF_PU_AssoMapAlgos::GetCleanedKshort(vertCompCandCollKshortH,beamspotH,cleanedColls_);
  
        //get the vertex composite candidate collection for the Lambda's
        iEvent.getByLabel(LambdaCollection_, vertCompCandCollLambdaH);
        cleanedLambdaCollP = PF_PU_AssoMapAlgos::GetCleanedLambda(vertCompCandCollLambdaH,beamspotH,cleanedColls_);
  
        //get the displaced vertex collection for nuclear interactions
        //create a new bool, true if no displaced vertex collection is in the event, mostly for AOD
        missingColls = false;
        if(!iEvent.getByLabel(NIVertexCollection_,displVertexCollH)){
          if (ignoremissingpfcollection_){

            missingColls = true; 

            if ( numWarnings_ < maxNumWarnings_ ) {
              LogWarning("PF_PU_AssoMapAlgos::GetInputCollections")
                << "No Extra objects available in input file --> skipping reconstruction of displaced vertices !!" << endl;
              ++numWarnings_;
            }

          }
        } else {

            cleanedNICollP = PF_PU_AssoMapAlgos::GetCleanedNI(displVertexCollH,beamspotH,true);

        }
          
        //get the input vertex collection
        iEvent.getByLabel(input_VertexCollection_, vtxcollH);

        iSetup.get<IdealMagneticFieldRecord>().get(bFieldH);

}

/*************************************************************************************/
/* create the track to vertex association map                                        */ 
/*************************************************************************************/
std::auto_ptr<TrackToVertexAssMap> 
PF_PU_AssoMapAlgos::CreateTrackToVertexMap(edm::Handle<reco::TrackCollection> trkcollH, const edm::EventSetup& iSetup)
{

        auto_ptr<TrackToVertexAssMap> track2vertex(new TrackToVertexAssMap());

        int num_vertices = vtxcollH->size();
        if ( num_vertices < input_MaxNumAssociations_) input_MaxNumAssociations_ = num_vertices;
            
        //loop over all tracks of the track collection  
        for ( size_t idxTrack = 0; idxTrack < trkcollH->size(); ++idxTrack ) {

          TrackRef trackref = TrackRef(trkcollH, idxTrack);

          TransientTrack transtrk(trackref, &(*bFieldH) );
          transtrk.setBeamSpot(*beamspotH);
          transtrk.setES(iSetup);

          vector<VertexRef>* vtxColl_help = CreateVertexVector(vtxcollH);

          for ( int assoc_ite = 0; assoc_ite < input_MaxNumAssociations_; ++assoc_ite ) {

            VertexStepPair assocVtx = FindAssociation(trackref, vtxColl_help, bFieldH, iSetup, beamspotH, assoc_ite);    
            int step = assocVtx.second;
            double distance = ( IPTools::absoluteImpactParameter3D( transtrk, *(assocVtx.first) ) ).second.value();
           
            int quality = DefineQuality(assoc_ite, step, distance);

            //std::cout << "associating track: Pt = " << trackref->pt() << "," 
            //          << " eta = " << trackref->eta() << ", phi = " << trackref->phi() 
            //          << " to vertex: z = " << associatedVertex.first->position().z() << " with quality q = " << quality << std::endl;

    
            // Insert the best vertex and the pair of track and the quality of this association in the map
            track2vertex->insert( assocVtx.first, make_pair(trackref, quality) );

            PF_PU_AssoMapAlgos::EraseVertex(vtxColl_help, assocVtx.first);

          }

          delete vtxColl_help;

        }

        return track2vertex;

}

/*************************************************************************************/
/* create the vertex to track association map                                        */ 
/*************************************************************************************/

std::auto_ptr<VertexToTrackAssMap> 
PF_PU_AssoMapAlgos::CreateVertexToTrackMap(edm::Handle<reco::TrackCollection> trkcollH, const edm::EventSetup& iSetup)
{

        auto_ptr<VertexToTrackAssMap> vertex2track(new VertexToTrackAssMap());

        int num_vertices = vtxcollH->size();
        if ( num_vertices < input_MaxNumAssociations_) input_MaxNumAssociations_ = num_vertices;
            
        //loop over all tracks of the track collection  
        for ( size_t idxTrack = 0; idxTrack < trkcollH->size(); ++idxTrack ) {

          TrackRef trackref = TrackRef(trkcollH, idxTrack);

          TransientTrack transtrk(trackref, &(*bFieldH) );
          transtrk.setBeamSpot(*beamspotH);
          transtrk.setES(iSetup);

          vector<VertexRef>* vtxColl_help = CreateVertexVector(vtxcollH);

          for ( int assoc_ite = 0; assoc_ite < input_MaxNumAssociations_; ++assoc_ite ) {

            VertexStepPair assocVtx = FindAssociation(trackref, vtxColl_help, bFieldH, iSetup, beamspotH, assoc_ite);    
            int step = assocVtx.second;
            double distance = ( IPTools::absoluteImpactParameter3D( transtrk, *(assocVtx.first) ) ).second.value();
           
            int quality = DefineQuality(assoc_ite, step, distance);

            //std::cout << "associating track: Pt = " << trackref->pt() << "," 
            //          << " eta = " << trackref->eta() << ", phi = " << trackref->phi() 
            //          << " to vertex: z = " << associatedVertex.first->position().z() << " with quality q = " << quality << std::endl;
    
            // Insert the best vertex and the pair of track and the quality of this association in the map
            vertex2track->insert( trackref, make_pair(assocVtx.first, quality) );

            PF_PU_AssoMapAlgos::EraseVertex(vtxColl_help, assocVtx.first);

          }

          delete vtxColl_help;
  
        }

        return vertex2track;

}

/*****************************************************************************************/
/* function to sort the vertices in the AssociationMap by the sum of (pT - pT_Error)**2  */ 
/*****************************************************************************************/

auto_ptr<TrackToVertexAssMap>  
PF_PU_AssoMapAlgos::SortAssociationMap(TrackToVertexAssMap* trackvertexassInput) 
{
        //create a new TrackVertexAssMap for the Output which will be sorted
        auto_ptr<TrackToVertexAssMap> trackvertexassOutput(new TrackToVertexAssMap() );

        //Create and fill a vector of pairs of vertex and the summed (pT-pT_Error)**2 of the tracks associated to the vertex 
        VertexPtsumVector vertexptsumvector;

        //loop over all vertices in the association map
        for(TrackToVertexAssMap::const_iterator assomap_ite=trackvertexassInput->begin(); assomap_ite!=trackvertexassInput->end(); assomap_ite++){

          const VertexRef assomap_vertexref = assomap_ite->key;
          const TrackQualityPairVector trckcoll = assomap_ite->val;

          float ptsum = 0;
 
          TrackRef trackref;

          //get the tracks associated to the vertex and calculate the manipulated pT**2
          for(unsigned int trckcoll_ite=0; trckcoll_ite<trckcoll.size(); trckcoll_ite++){

            trackref = trckcoll[trckcoll_ite].first;
            int quality = trckcoll[trckcoll_ite].second;

            if ( quality<=2 ) continue;          

            double man_pT = trackref->pt() - trackref->ptError();
            if(man_pT>0.) ptsum+=man_pT*man_pT;

          }

          vertexptsumvector.push_back(make_pair(assomap_vertexref,ptsum));

        }

        while (vertexptsumvector.size()!=0){

          VertexRef vertexref_highestpT;
          float highestpT = 0.;
          int highestpT_index = 0;

          for(unsigned int vtxptsumvec_ite=0; vtxptsumvec_ite<vertexptsumvector.size(); vtxptsumvec_ite++){
 
            if(vertexptsumvector[vtxptsumvec_ite].second>highestpT){

              vertexref_highestpT = vertexptsumvector[vtxptsumvec_ite].first;
              highestpT = vertexptsumvector[vtxptsumvec_ite].second;
              highestpT_index = vtxptsumvec_ite;
        
            }

          }
          
          //loop over all vertices in the association map
          for(TrackToVertexAssMap::const_iterator assomap_ite=trackvertexassInput->begin(); assomap_ite!=trackvertexassInput->end(); assomap_ite++){

            const VertexRef assomap_vertexref = assomap_ite->key;
            const TrackQualityPairVector trckcoll = assomap_ite->val;

            //if the vertex from the association map the vertex with the highest manipulated pT 
            //insert all associated tracks in the output Association Map
            if(assomap_vertexref==vertexref_highestpT) 
              for(unsigned int trckcoll_ite=0; trckcoll_ite<trckcoll.size(); trckcoll_ite++) 
                trackvertexassOutput->insert(assomap_vertexref,trckcoll[trckcoll_ite]);
 
          }

          vertexptsumvector.erase(vertexptsumvector.begin()+highestpT_index);   

        }

        return trackvertexassOutput;

}

/********************/
/*                  */
/* Member Functions */ 
/*                  */
/********************/

/*************************************************************************************/
/* create helping vertex vector to remove associated vertices                        */ 
/*************************************************************************************/

std::vector<reco::VertexRef>* 
PF_PU_AssoMapAlgos::CreateVertexVector(edm::Handle<reco::VertexCollection> vtxcollH)
{

        vector<VertexRef>* output = new vector<VertexRef>();
        
        for(unsigned int index_vtx=0;  index_vtx<vtxcollH->size(); ++index_vtx){

          VertexRef vertexref(vtxcollH,index_vtx);

          output->push_back(vertexref);

        }

        return output;

}

/****************************************************************************/
/* erase one vertex from the vertex vector                                  */ 
/****************************************************************************/

void 
PF_PU_AssoMapAlgos::EraseVertex(std::vector<reco::VertexRef>* vtxcollV, reco::VertexRef toErase)
{
        
        for(unsigned int index_vtx=0;  index_vtx<vtxcollV->size(); ++index_vtx){

          VertexRef vertexref = vtxcollV->at(index_vtx);

          if ( vertexref == toErase ){
            vtxcollV->erase(vtxcollV->begin()+index_vtx);
            break;
          }

        }

}


/*************************************************************************************/
/* function to find the closest vertex in 3D for a certain track                     */ 
/*************************************************************************************/

VertexRef 
PF_PU_AssoMapAlgos::FindClosestZ(const reco::TrackRef trkref, std::vector<reco::VertexRef>* vtxcollV, double tWeight)
{

        double ztrack = trkref->vertex().z();

        VertexRef foundVertexRef = vtxcollV->at(0);

        double dzmin = 1e5;
          
        //loop over all vertices with a good quality in the vertex collection
        for(unsigned int index_vtx=0;  index_vtx<vtxcollV->size(); ++index_vtx){

          VertexRef vertexref = vtxcollV->at(index_vtx);

          double nTracks = sqrt(vertexref->tracksSize());

          double z_distance = fabs(ztrack - vertexref->z());

          double weightedDistance = z_distance-tWeight*nTracks; 

          if(weightedDistance<dzmin) {
            dzmin = weightedDistance; 
            foundVertexRef = vertexref;
          }
        
        }

        return foundVertexRef;
}


/*************************************************************************************/
/* function to find the closest vertex in 3D for a certain track                     */ 
/*************************************************************************************/

VertexRef 
PF_PU_AssoMapAlgos::FindClosest3D(TransientTrack transtrk, std::vector<reco::VertexRef>* vtxcollV, double tWeight)
{

        VertexRef foundVertexRef = vtxcollV->at(0);

        double d3min = 1e5;
          
        //loop over all vertices with a good quality in the vertex collection
        for(unsigned int index_vtx=0;  index_vtx<vtxcollV->size(); ++index_vtx){

          VertexRef vertexref = vtxcollV->at(index_vtx);

          double nTracks = sqrt(vertexref->tracksSize());

          double distance = 1e5;                
          pair<bool,Measurement1D> IpPair = IPTools::absoluteImpactParameter3D(transtrk, *vertexref);
 
          if(IpPair.first)
            distance = IpPair.second.value();

          double weightedDistance = distance-tWeight*nTracks;   

          if(weightedDistance<d3min) {
            d3min = weightedDistance; 
            foundVertexRef = vertexref;
          }
        
        }

        return foundVertexRef;
}

/****************************************************************************************/
/* function to calculate the deltaR between a vector and a vector connecting two points */ 
/****************************************************************************************/

double
PF_PU_AssoMapAlgos::dR(const math::XYZPoint& vtx_pos, const math::XYZVector& vtx_mom, edm::Handle<reco::BeamSpot> bsH)
{

        double bs_x = bsH->x0();
        double bs_y = bsH->y0();
        double bs_z = bsH->z0();

        double connVec_x = vtx_pos.x() - bs_x;
        double connVec_y = vtx_pos.y() - bs_y;
        double connVec_z = vtx_pos.z() - bs_z;

        double connVec_r = sqrt(connVec_x*connVec_x + connVec_y*connVec_y + connVec_z*connVec_z);
        double connVec_theta = acos(connVec_z*1./connVec_r);

        double connVec_eta = -1.*log(tan(connVec_theta*1./2.));
        double connVec_phi = atan2(connVec_y,connVec_x);

        return deltaR(vtx_mom.eta(),vtx_mom.phi(),connVec_eta,connVec_phi);
    
}

/*************************************************************************************/
/* function to filter the conversion collection                                      */ 
/*************************************************************************************/

auto_ptr<ConversionCollection> 
PF_PU_AssoMapAlgos::GetCleanedConversions(edm::Handle<reco::ConversionCollection> convCollH, Handle<BeamSpot> bsH, bool cleanedColl)
{
        auto_ptr<ConversionCollection> cleanedConvColl(new ConversionCollection() );

        for (unsigned int convcoll_idx=0; convcoll_idx<convCollH->size(); convcoll_idx++){

          ConversionRef convref(convCollH,convcoll_idx);

          if(!cleanedColl){   
            cleanedConvColl->push_back(*convref);
            continue;
          }

          if( (convref->nTracks()==2) &&
              (fabs(convref->pairInvariantMass())<=0.1) ){
    
            cleanedConvColl->push_back(*convref);

          }

        }

        return cleanedConvColl;

}


/*************************************************************************************/
/* function to find out if the track comes from a gamma conversion                   */ 
/*************************************************************************************/

bool
PF_PU_AssoMapAlgos::ComesFromConversion(const TrackRef trackref, const ConversionCollection& cleanedConvColl, Conversion* gamma)
{

        for(unsigned int convcoll_ite=0; convcoll_ite<cleanedConvColl.size(); convcoll_ite++){

          if(ConversionTools::matchesConversion(trackref,cleanedConvColl.at(convcoll_ite))){
        
            *gamma = cleanedConvColl.at(convcoll_ite);
            return true;

          }

        }

        return false;
}


/********************************************************************************/
/* function to find the closest vertex for a track from a conversion            */ 
/********************************************************************************/

VertexRef
PF_PU_AssoMapAlgos::FindConversionVertex(const reco::TrackRef trackref, const reco::Conversion& gamma, ESHandle<MagneticField> bfH, const EventSetup& iSetup, edm::Handle<reco::BeamSpot> bsH, std::vector<reco::VertexRef>* vtxcollV, double tWeight)
{ 

        math::XYZPoint conv_pos = gamma.conversionVertex().position();

        math::XYZVector conv_mom(gamma.refittedPair4Momentum().x(),
                                 gamma.refittedPair4Momentum().y(),
                                 gamma.refittedPair4Momentum().z());

        Track photon(trackref->chi2(), trackref->ndof(), conv_pos, conv_mom, 0, trackref->covariance());

        TransientTrack transpho(photon, &(*bfH) );
        transpho.setBeamSpot(*bsH);
        transpho.setES(iSetup);

        return FindClosest3D(transpho, vtxcollV, tWeight);      

}

/*************************************************************************************/
/* function to filter the Kshort collection                                          */ 
/*************************************************************************************/

auto_ptr<VertexCompositeCandidateCollection>
PF_PU_AssoMapAlgos::GetCleanedKshort(Handle<VertexCompositeCandidateCollection> KshortsH, Handle<BeamSpot> bsH, bool cleanedColl)
{

        auto_ptr<VertexCompositeCandidateCollection> cleanedKaonColl(new VertexCompositeCandidateCollection() );

        for (unsigned int kscoll_idx=0; kscoll_idx<KshortsH->size(); kscoll_idx++){

          VertexCompositeCandidateRef ksref(KshortsH,kscoll_idx);

          if(!cleanedColl){   
            cleanedKaonColl->push_back(*ksref);
            continue;
          }

          VertexDistance3D distanceComputer;

          GlobalPoint dec_pos = RecoVertex::convertPos(ksref->vertex());    

          GlobalError decayVertexError = GlobalError(ksref->vertexCovariance(0,0), ksref->vertexCovariance(0,1), ksref->vertexCovariance(1,1), ksref->vertexCovariance(0,2), ksref->vertexCovariance(1,2), ksref->vertexCovariance(2,2));
        
          math::XYZVector dec_mom(ksref->momentum().x(),
                                  ksref->momentum().y(),
                                  ksref->momentum().z());    

          GlobalPoint bsPosition = RecoVertex::convertPos(bsH->position());
          GlobalError bsError = RecoVertex::convertError(bsH->covariance3D());
      
          double kaon_significance = (distanceComputer.distance(VertexState(bsPosition,bsError), VertexState(dec_pos, decayVertexError))).significance();

          if ((ksref->vertex().rho()>=3.) &&
              (ksref->vertexNormalizedChi2()<=3.) &&
              (fabs(ksref->mass() - kMass)<=0.01) &&
              (kaon_significance>15.) &&
              (PF_PU_AssoMapAlgos::dR(ksref->vertex(),dec_mom,bsH)<=0.3) ){
  
            cleanedKaonColl->push_back(*ksref);

          }

        }

        return cleanedKaonColl;
}

/*************************************************************************************/
/* function to filter the Lambda collection                                          */ 
/*************************************************************************************/

auto_ptr<VertexCompositeCandidateCollection>
PF_PU_AssoMapAlgos::GetCleanedLambda(Handle<VertexCompositeCandidateCollection> LambdasH, Handle<BeamSpot> bsH, bool cleanedColl)
{

        auto_ptr<VertexCompositeCandidateCollection> cleanedLambdaColl(new VertexCompositeCandidateCollection() );

        for (unsigned int lambdacoll_idx=0; lambdacoll_idx<LambdasH->size(); lambdacoll_idx++){

          VertexCompositeCandidateRef lambdaref(LambdasH,lambdacoll_idx);

          if(!cleanedColl){   
            cleanedLambdaColl->push_back(*lambdaref);
            continue;
          }

          VertexDistance3D distanceComputer;

          GlobalPoint dec_pos = RecoVertex::convertPos(lambdaref->vertex());    

          GlobalError decayVertexError = GlobalError(lambdaref->vertexCovariance(0,0), lambdaref->vertexCovariance(0,1), lambdaref->vertexCovariance(1,1), lambdaref->vertexCovariance(0,2), lambdaref->vertexCovariance(1,2), lambdaref->vertexCovariance(2,2));
        
          math::XYZVector dec_mom(lambdaref->momentum().x(),
                                  lambdaref->momentum().y(),
                                  lambdaref->momentum().z());    

          GlobalPoint bsPosition = RecoVertex::convertPos(bsH->position());
          GlobalError bsError = RecoVertex::convertError(bsH->covariance3D());
      
          double lambda_significance = (distanceComputer.distance(VertexState(bsPosition,bsError), VertexState(dec_pos, decayVertexError))).significance();

          if ((lambdaref->vertex().rho()>=3.) &&
              (lambdaref->vertexNormalizedChi2()<=3.) &&
              (fabs(lambdaref->mass() - lamMass)<=0.005) &&
              (lambda_significance>15.) &&
              (PF_PU_AssoMapAlgos::dR(lambdaref->vertex(),dec_mom,bsH)<=0.3) ){
  
            cleanedLambdaColl->push_back(*lambdaref);

          }

        }

        return cleanedLambdaColl;
}

/*************************************************************************************/
/* function to find out if the track comes from a V0 decay                           */ 
/*************************************************************************************/

bool
PF_PU_AssoMapAlgos::ComesFromV0Decay(const TrackRef trackref, const VertexCompositeCandidateCollection& cleanedKshort, const VertexCompositeCandidateCollection& cleanedLambda, VertexCompositeCandidate* V0)
{

        //the part for the reassociation of particles from Kshort decays
        for(VertexCompositeCandidateCollection::const_iterator iKS=cleanedKshort.begin(); iKS!=cleanedKshort.end(); iKS++){

          const RecoChargedCandidate *dauCand1 = dynamic_cast<const RecoChargedCandidate*>(iKS->daughter(0));
          TrackRef dauTk1 = dauCand1->track();
          const RecoChargedCandidate *dauCand2 = dynamic_cast<const RecoChargedCandidate*>(iKS->daughter(1));
          TrackRef dauTk2 = dauCand2->track();

          if((trackref==dauTk1) || (trackref==dauTk2)){
          
            *V0 = *iKS; 
            return true;

          }

        }

        //the part for the reassociation of particles from Lambda decays
        for(VertexCompositeCandidateCollection::const_iterator iLambda=cleanedLambda.begin(); iLambda!=cleanedLambda.end(); iLambda++){

          const RecoChargedCandidate *dauCand1 = dynamic_cast<const RecoChargedCandidate*>(iLambda->daughter(0));
          TrackRef dauTk1 = dauCand1->track();
          const RecoChargedCandidate *dauCand2 = dynamic_cast<const RecoChargedCandidate*>(iLambda->daughter(1));
          TrackRef dauTk2 = dauCand2->track();

          if((trackref==dauTk1) || (trackref==dauTk2)){
          
            *V0 = *iLambda; 
            return true;

          }

        }

        return false;
}


/*************************************************************************************/
/* function to find the closest vertex in z for a track from a V0                    */ 
/*************************************************************************************/

VertexRef
PF_PU_AssoMapAlgos::FindV0Vertex(const TrackRef trackref, const VertexCompositeCandidate& V0_vtx, ESHandle<MagneticField> bFieldH, const EventSetup& iSetup, Handle<BeamSpot> bsH, std::vector<reco::VertexRef>* vtxcollV, double tWeight)
{ 

        math::XYZPoint dec_pos = V0_vtx.vertex();

        math::XYZVector dec_mom(V0_vtx.momentum().x(),
                                V0_vtx.momentum().y(),
                                V0_vtx.momentum().z());

        Track V0(trackref->chi2(), trackref->ndof(), dec_pos, dec_mom, 0, trackref->covariance());

        TransientTrack transV0(V0, &(*bFieldH) );
        transV0.setBeamSpot(*bsH);
        transV0.setES(iSetup);

        return FindClosest3D(transV0, vtxcollV, tWeight);               

}


/*************************************************************************************/
/* function to filter the nuclear interaction collection                             */ 
/*************************************************************************************/

auto_ptr<PFDisplacedVertexCollection>
PF_PU_AssoMapAlgos::GetCleanedNI(Handle<PFDisplacedVertexCollection> NuclIntH, Handle<BeamSpot> bsH, bool cleanedColl)
{

        auto_ptr<PFDisplacedVertexCollection> cleanedNIColl(new PFDisplacedVertexCollection() );

        for (PFDisplacedVertexCollection::const_iterator niref=NuclIntH->begin(); niref!=NuclIntH->end(); niref++){


          if( (niref->isFake()) || !(niref->isNucl()) ) continue;

          if(!cleanedColl){
            cleanedNIColl->push_back(*niref);
            continue;
          }

          VertexDistance3D distanceComputer;

          GlobalPoint ni_pos = RecoVertex::convertPos(niref->position());    
          GlobalError interactionVertexError = RecoVertex::convertError(niref->error());

          math::XYZVector ni_mom(niref->primaryMomentum().x(),
                                 niref->primaryMomentum().y(),
                                 niref->primaryMomentum().z());

          GlobalPoint bsPosition = RecoVertex::convertPos(bsH->position());
          GlobalError bsError = RecoVertex::convertError(bsH->covariance3D());
      
          double nuclint_significance = (distanceComputer.distance(VertexState(bsPosition,bsError), VertexState(ni_pos, interactionVertexError))).significance();

          if ((niref->position().rho()>=3.) &&
              (nuclint_significance>15.) &&
              (PF_PU_AssoMapAlgos::dR(niref->position(),ni_mom,bsH)<=0.3) ){
  
            cleanedNIColl->push_back(*niref);

          }

        }

        return cleanedNIColl;
}

/*************************************************************************************/
/* function to find out if the track comes from a nuclear interaction                */ 
/*************************************************************************************/

bool
PF_PU_AssoMapAlgos::ComesFromNI(const TrackRef trackref, const PFDisplacedVertexCollection& cleanedNI, PFDisplacedVertex* displVtx)
{

        //the part for the reassociation of particles from nuclear interactions
        for(PFDisplacedVertexCollection::const_iterator iDisplV=cleanedNI.begin(); iDisplV!=cleanedNI.end(); iDisplV++){

          if(iDisplV->trackWeight(trackref)>1.e-5){
          
            *displVtx = *iDisplV; 
            return true;

          }

        }

        return false;
}


/*************************************************************************************/
/* function to find the closest vertex in z for a track from a nuclear interaction   */ 
/*************************************************************************************/

VertexRef
PF_PU_AssoMapAlgos::FindNIVertex(const TrackRef trackref, const PFDisplacedVertex& displVtx, ESHandle<MagneticField> bFieldH, const EventSetup& iSetup, Handle<BeamSpot> bsH, std::vector<reco::VertexRef>* vtxcollV, double tWeight)
{

        TrackCollection refittedTracks = displVtx.refittedTracks();

        if((displVtx.isTherePrimaryTracks()) || (displVtx.isThereMergedTracks())){

          for(TrackCollection::const_iterator trkcoll_ite=refittedTracks.begin(); trkcoll_ite!=refittedTracks.end(); trkcoll_ite++){
        
            const TrackBaseRef retrackbaseref = displVtx.originalTrack(*trkcoll_ite); 

            if(displVtx.isIncomingTrack(retrackbaseref)){

              VertexRef VOAssociation = TrackWeightAssociation(retrackbaseref, vtxcollV);

              if( VOAssociation->trackWeight(retrackbaseref) >= 1.e-5 ){
                return VOAssociation;
              }

              TransientTrack transIncom(*retrackbaseref, &(*bFieldH) );
              transIncom.setBeamSpot(*bsH);
              transIncom.setES(iSetup);

              return FindClosest3D(transIncom, vtxcollV, tWeight); 

            }

          }

        }

        math::XYZPoint ni_pos = displVtx.position();

        math::XYZVector ni_mom(displVtx.primaryMomentum().x(),
                               displVtx.primaryMomentum().y(),
                               displVtx.primaryMomentum().z());

        Track incom(trackref->chi2(), trackref->ndof(), ni_pos, ni_mom, 0, trackref->covariance());

        TransientTrack transIncom(incom, &(*bFieldH) );
        transIncom.setBeamSpot(*bsH);
        transIncom.setES(iSetup);

        return FindClosest3D(transIncom, vtxcollV, tWeight); 

}

/*************************************************************************************/
/* function to find the vertex with the highest TrackWeight for a certain track      */ 
/*************************************************************************************/

VertexRef 
PF_PU_AssoMapAlgos::TrackWeightAssociation(const TrackBaseRef& trackbaseRef, std::vector<reco::VertexRef>* vtxcollV) 
{

        VertexRef bestvertexref = vtxcollV->at(0);              
        float bestweight = 0.;

        //loop over all vertices in the vertex collection
        for(unsigned int index_vtx=0;  index_vtx<vtxcollV->size(); ++index_vtx){

          VertexRef vertexref = vtxcollV->at(index_vtx);

          //get the most probable vertex for the track
          float weight = vertexref->trackWeight(trackbaseRef);
          if(weight>bestweight){
            bestweight = weight;
            bestvertexref = vertexref;
          } 

        }

        return bestvertexref;

}

/*************************************************************************************/
/* find an association for a certain track                                           */ 
/*************************************************************************************/

VertexStepPair 
PF_PU_AssoMapAlgos::FindAssociation(const reco::TrackRef& trackref, std::vector<reco::VertexRef>* vtxColl, edm::ESHandle<MagneticField> bfH, const edm::EventSetup& iSetup, edm::Handle<reco::BeamSpot> bsH, int assocNum)
{

        const TrackBaseRef& trackbaseRef = TrackBaseRef(trackref);

        VertexRef foundVertex;

        //if it is not the first try of an association jump to the final association
        //to avoid multiple (secondary) associations and/or unphysical (primary and secondary) associations
        if ( assocNum>0 ) goto finalStep;

        // Step 1: First round of association:
        // Find the vertex with the highest track-to-vertex association weight 
        foundVertex = TrackWeightAssociation(trackbaseRef, vtxColl);

        if ( foundVertex->trackWeight(trackbaseRef) >= 1.e-5 ){
          return make_pair( foundVertex, 0. );
        }

        // Step 2: Reassociation
        // Second round of association:
        // In case no vertex with track-to-vertex association weight > 1.e-5 is found,
        // check the track originates from a neutral hadron decay, photon conversion or nuclear interaction

        if ( input_doReassociation_ ) {

          // Test if the track comes from a photon conversion:
          // If so, try to find the vertex of the mother particle
          Conversion gamma;
          if ( ComesFromConversion(trackref, *cleanedConvCollP, &gamma) ){
            foundVertex = FindConversionVertex(trackref, gamma, bfH, iSetup, bsH, vtxColl, input_nTrack_);
            return make_pair( foundVertex, 1. );
          }

          // Test if the track comes from a Kshort or Lambda decay:
          // If so, reassociate the track to the vertex of the V0
          VertexCompositeCandidate V0;
          if ( ComesFromV0Decay(trackref, *cleanedKshortCollP, *cleanedLambdaCollP, &V0) ) {
            foundVertex = FindV0Vertex(trackref, V0, bfH, iSetup, bsH, vtxColl, input_nTrack_);
            return make_pair( foundVertex, 1. );
          }

          if ( !missingColls ) {

            // Test if the track comes from a nuclear interaction:
            // If so, reassociate the track to the vertex of the incoming particle 
            PFDisplacedVertex displVtx;
            if ( ComesFromNI(trackref, *cleanedNICollP, &displVtx) ){
              foundVertex = FindNIVertex(trackref, displVtx, bfH, iSetup, bsH, vtxColl, input_nTrack_);
              return make_pair( foundVertex, 1. );
            }

          }

        }

        // Step 3: Final association
        // If no vertex is found with track-to-vertex association weight > 1.e-5
        // and no reassociation was done do the final association 
        // look for the closest vertex in 3D or in z/longitudinal distance
        // or associate the track always to the first vertex (default)

        finalStep:

        switch (input_FinalAssociation_) {
          
          case 1:{

            // closest in z
            foundVertex = FindClosestZ(trackref,vtxColl,input_nTrack_);
            break;


          }
          
          case 2:{

            // closest in 3D
            TransientTrack transtrk(trackref, &(*bfH) );
            transtrk.setBeamSpot(*bsH);
            transtrk.setES(iSetup);

            foundVertex = FindClosest3D(transtrk,vtxColl,input_nTrack_);
            break;

          }
          
          default:{

            // allways first vertex
            foundVertex = vtxColl->at(0);
            break;

          }

        }
        
        return make_pair( foundVertex, 2. );

}

/*************************************************************************************/
/* get the quality for a certain association                                         */ 
/*************************************************************************************/

int 
PF_PU_AssoMapAlgos::DefineQuality(int assoc_ite, int step, double distance)
{

        int quality = 0;

        switch (step) {
            
          case 0:{

            //TrackWeight association
            if ( distance <= tw_90 ) {
              quality = 5;
            } else {
              if ( distance <= tw_70 ) {
                quality = 4;
              } else {
                if ( distance <= tw_50 ) {
                  quality = 3;
                } else {
                  quality = 2;
                }  
              }
            }
            break;

          }

          case 1:{

            //Secondary association
            if ( distance <= sec_70 ) {
              quality = 4;
            } else {
              if ( distance <= sec_50 ) {
                quality = 3;
              } else {
                quality = 2;
              }
            }
            break;

          } 

          case 2:{

            //Final association
            if ( assoc_ite == 1 ) {
              quality = 1;
            } else {
              if ( assoc_ite >= 2 ) {
                quality = 0;
              } else {
                if ( distance <= fin_70 ) {
                  quality = 4;
                } else {
                  if ( distance <= fin_50 ) {
                    quality = 3;
                  } else {
                    quality = 2;
                  }
                }
              }
            }
            break;

          } 

          default:{

            quality = -1;
            break;
          }        

        }

        return quality;

}