JpsiPlus1Track.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
// ****************************************************************************
// ----------------------------------------------------------------------------
// JpsiPlus1Track
// James Catmore <James.Catmore@cern.ch>
// Results returned as a vector of xAOD::Vertex
// ----------------------------------------------------------------------------
// ****************************************************************************
 
#include "JpsiUpsilonTools/JpsiPlus1Track.h"
#include "xAODBPhys/BPhysHelper.h"
#include "TrkVertexFitterInterfaces/IVertexFitter.h"
#include "TrkVKalVrtFitter/TrkVKalVrtFitter.h"
#include "TrkToolInterfaces/ITrackSelectorTool.h"
#include "xAODTracking/TrackParticle.h"
#include "xAODTracking/Vertex.h"
#include "xAODTracking/VertexContainer.h"
#include "AthLinks/ElementLink.h"
#include "xAODTracking/TrackParticleContainer.h"
#include "InDetConversionFinderTools/VertexPointEstimator.h"
#include <memory>
#include "JpsiUpsilonTools/JpsiUpsilonCommon.h"
#include "TruthUtils/ParticleConstants.h"
#include "xAODEgamma/ElectronContainer.h"
#include <limits>
 
namespace Analysis {
 
 
    // Set masses
    constexpr double muMass = ParticleConstants::muonMassInMeV;
    constexpr double kMass = ParticleConstants::chargedKaonMassInMeV;
    constexpr double piMass = ParticleConstants::chargedPionMassInMeV;
 
    StatusCode JpsiPlus1Track::initialize() {
        
        // retrieving vertex Fitter
        ATH_CHECK(m_iVertexFitter.retrieve());
        m_VKVFitter = dynamic_cast<Trk::TrkVKalVrtFitter*>(&(*m_iVertexFitter));
        
        // Get the track selector tool from ToolSvc
        ATH_CHECK( m_trkSelector.retrieve());
        
        // Get the vertex point estimator tool from ToolSvc
        ATH_CHECK(m_jpsiCollectionKey.initialize());
        ATH_CHECK(m_TrkParticleCollection.initialize());
        if(m_MuonsUsedInJpsi.key() == "NONE") m_MuonsUsedInJpsi = "";//for backwards compatability
        ATH_CHECK(m_MuonsUsedInJpsi.initialize(!m_MuonsUsedInJpsi.key().empty()));
        ATH_CHECK(m_TrkParticleGSFCollection.initialize(!m_TrkParticleGSFCollection.key().empty()));
        ATH_CHECK(m_electronCollectionKey.initialize(SG::AllowEmpty));
 
        if (m_requiredNMuons > 0 && !m_excludeJpsiMuonsOnly) {
          ATH_MSG_FATAL("Invalid configuration");
          return StatusCode::FAILURE;
        }
 
        if(m_muonMasses.empty()){
          m_muonMasses.assign(2, muMass);
        }
 
        m_useGSFTrack.reset();
        for(int i : m_useGSFTrackIndices) m_useGSFTrack.set(i, true);
        ATH_MSG_DEBUG("Initialize successful");
        
        return StatusCode::SUCCESS;
        
    }
    
 
    JpsiPlus1Track::JpsiPlus1Track(const std::string& t, const std::string& n, const IInterface* p)  : AthAlgTool(t,n,p),
    m_piMassHyp(false),
    m_kMassHyp(true),
    m_trkThresholdPt(0.0),
    m_trkMaxEta(102.5),
    m_BThresholdPt(0.0),
    m_BMassUpper(0.0),
    m_BMassLower(0.0),
    m_jpsiCollectionKey("JpsiCandidates"),
    m_jpsiMassUpper(0.0),
    m_jpsiMassLower(0.0),
    m_TrkParticleCollection("TrackParticleCandidate"),
    m_MuonsUsedInJpsi(""),
    m_excludeJpsiMuonsOnly(true), 
    m_excludeCrossJpsiTracks(false),
    m_iVertexFitter("Trk::TrkVKalVrtFitter"),
    m_trkSelector("InDet::TrackSelectorTool"),
    m_useMassConst(true),
    m_altMassConst(-1.0),
    m_chi2cut(-1.0),
    m_trkTrippletMassUpper(-1.0),
    m_trkTrippletMassLower(-1.0),
    m_trkTrippletPt(-1.0),
    m_trkDeltaZ(-1.0),
    m_TrkParticleGSFCollection(""),
    m_electronCollectionKey(""),
    m_candidateLimit(std::numeric_limits<size_t>::max())
    {
        declareInterface<JpsiPlus1Track>(this);
        declareProperty("pionHypothesis",m_piMassHyp);
        declareProperty("kaonHypothesis",m_kMassHyp);
        declareProperty("trkThresholdPt",m_trkThresholdPt);
        declareProperty("trkMaxEta",m_trkMaxEta);
        declareProperty("BThresholdPt",m_BThresholdPt);
        declareProperty("BMassUpper",m_BMassUpper);
        declareProperty("BMassLower",m_BMassLower);
        declareProperty("JpsiContainerKey",m_jpsiCollectionKey);
        declareProperty("JpsiMassUpper",m_jpsiMassUpper);
        declareProperty("JpsiMassLower",m_jpsiMassLower);
        declareProperty("TrackParticleCollection",m_TrkParticleCollection);
        declareProperty("MuonsUsedInJpsi",m_MuonsUsedInJpsi);
        declareProperty("ExcludeJpsiMuonsOnly",m_excludeJpsiMuonsOnly);
        declareProperty("ExcludeCrossJpsiTracks",m_excludeCrossJpsiTracks); //Essential when trying to make vertices out of multiple muons (set to false)
        declareProperty("TrkVertexFitterTool",m_iVertexFitter);
        declareProperty("TrackSelectorTool", m_trkSelector);
        declareProperty("UseMassConstraint", m_useMassConst);
        declareProperty("AlternativeMassConstraint",m_altMassConst);
 
        // additional cuts by Daniel Scheirich copied from 2Tracks by Adam Barton
        declareProperty("Chi2Cut",m_chi2cut);
        declareProperty("TrkTrippletMassUpper"  ,m_trkTrippletMassUpper);
        declareProperty("TrkTrippletMassLower"  ,m_trkTrippletMassLower);
        declareProperty("TrkQuadrupletPt"       ,m_trkTrippletPt       );
        declareProperty("TrkDeltaZ"             ,m_trkDeltaZ           );
        declareProperty("RequireNMuonTracks"    ,m_requiredNMuons      );
        declareProperty("RequireNElectronTracks", m_requiredNElectrons );
        declareProperty("AlternativeMassConstraintTrack", m_muonMasses );
        declareProperty("UseGSFTrackIndices",    m_useGSFTrackIndices  );
        declareProperty("GSFCollection",         m_TrkParticleGSFCollection);
        declareProperty("ElectronCollection",    m_electronCollectionKey);
        declareProperty("SkipNoElectron",    m_skipNoElectron);
        declareProperty("CandidateLimit", m_candidateLimit);
    }
    
    JpsiPlus1Track::~JpsiPlus1Track() {}
    
    //-------------------------------------------------------------------------------------
    // Find the candidates
    //-------------------------------------------------------------------------------------
    StatusCode JpsiPlus1Track::performSearch(const EventContext& ctx, xAOD::VertexContainer& bContainer) const
    {
        ATH_MSG_DEBUG( "JpsiPlus1Track::performSearch" );
        
        // Get the J/psis from StoreGate
        const xAOD::VertexContainer* importedJpsiCollection(0);
        SG::ReadHandle<xAOD::VertexContainer> jpsiCollectionhandle(m_jpsiCollectionKey,ctx);
        if(!jpsiCollectionhandle.isValid()){
            ATH_MSG_ERROR("No VertexContainer with key " << m_jpsiCollectionKey.key() << " found in StoreGate. BCandidates will be EMPTY!");
            return StatusCode::FAILURE;
        }else{
            importedJpsiCollection = jpsiCollectionhandle.cptr();
            ATH_MSG_DEBUG("Found VxCandidate container with key "<<m_jpsiCollectionKey.key());
        }
        ATH_MSG_DEBUG("VxCandidate container size " << importedJpsiCollection->size());
        
        // Get tracks
        const xAOD::TrackParticleContainer* importedTrackCollection{nullptr};
        SG::ReadHandle<xAOD::TrackParticleContainer> TrkParticleHandle(m_TrkParticleCollection,ctx);
        if(!TrkParticleHandle.isValid()){
            ATH_MSG_ERROR("No track particle collection with name " << m_TrkParticleCollection << " found in StoreGate!");
            return StatusCode::FAILURE;
        } else {
            importedTrackCollection = TrkParticleHandle.cptr();
            ATH_MSG_DEBUG("Found track particle collection " << m_TrkParticleCollection << " in StoreGate!");
        }
        ATH_MSG_DEBUG("Track container size "<< importedTrackCollection->size());
 
        const xAOD::TrackParticleContainer* importedGSFTrackCollection(nullptr);
        if(m_useGSFTrack.any() && !m_TrkParticleGSFCollection.key().empty()){
           SG::ReadHandle<xAOD::TrackParticleContainer> h(m_TrkParticleGSFCollection,ctx);
           ATH_CHECK(h.isValid());
           importedGSFTrackCollection = h.cptr();
        }
 
 
        // Get the muon collection used to build the J/psis
        const xAOD::MuonContainer* importedMuonCollection(0);
        if (!m_MuonsUsedInJpsi.key().empty()) {
            SG::ReadHandle<xAOD::MuonContainer> h(m_MuonsUsedInJpsi,ctx);
            if (!h.isValid()){
                ATH_MSG_ERROR("No muon collection with name " << m_MuonsUsedInJpsi.key() << " found in StoreGate!");
                return StatusCode::FAILURE;
            } else {
                importedMuonCollection = h.cptr();
                ATH_MSG_DEBUG("Found muon collection " << m_MuonsUsedInJpsi.key() << " in StoreGate!");
            }
            ATH_MSG_DEBUG("Muon container size "<< importedMuonCollection->size());
        }
        
        // Get the electrons from StoreGate
        const xAOD::ElectronContainer* importedElectronCollection = nullptr;
        if (!m_electronCollectionKey.empty()){
            SG::ReadHandle<xAOD::ElectronContainer> h(m_electronCollectionKey,ctx);
            if (!h.isValid()){
                ATH_MSG_ERROR("No Electron collection with name " << m_electronCollectionKey.key() << " found in StoreGate!");
                return StatusCode::FAILURE;
            } else {
                importedElectronCollection = h.cptr();
                ATH_MSG_DEBUG("Found Electron collection " << m_electronCollectionKey.key() << " in StoreGate!");
            }
            ATH_MSG_DEBUG("Electron container size "<< importedElectronCollection->size());
        }
 
        
        // Typedef for vectors of tracks and VxCandidates
        typedef std::vector<const xAOD::TrackParticle*> TrackBag;
        typedef std::vector<const xAOD::Electron*> ElectronBag;
        
        // Select the inner detector tracks
        const xAOD::Vertex* vx = nullptr;
        TrackBag theIDTracksAfterSelection;
        for (auto trkPBItr=importedTrackCollection->cbegin(); trkPBItr!=importedTrackCollection->cend(); ++trkPBItr) {
            const xAOD::TrackParticle* tp (*trkPBItr);
            if ( tp->pt()<m_trkThresholdPt ) continue;
            if ( fabs(tp->eta())>m_trkMaxEta ) continue;
            if (importedMuonCollection!=NULL && !m_excludeJpsiMuonsOnly) {
                if (JpsiUpsilonCommon::isContainedIn(tp,importedMuonCollection)) continue;
            }
            if ( m_trkSelector->decision(*tp, vx) ) theIDTracksAfterSelection.push_back(tp);
        }
        
        // Add GSF tracks
        if(m_useGSFTrack.any()){
            ATH_MSG_DEBUG("importedTrackCollection contains GSF tracks " << importedGSFTrackCollection->size());
            for (auto trkPBItr=importedGSFTrackCollection->cbegin(); trkPBItr!=importedGSFTrackCollection->cend(); ++trkPBItr) {
            const xAOD::TrackParticle* tp (*trkPBItr);
            if ( tp->pt()<m_trkThresholdPt ) continue;
            if ( fabs(tp->eta())>m_trkMaxEta ) continue;
            if (!importedMuonCollection->empty() && !m_excludeJpsiMuonsOnly) {
               if (JpsiUpsilonCommon::isContainedIn(tp,importedMuonCollection)) continue;
            }
            if (m_trkSelector->decision(*tp, vx)) theIDTracksAfterSelection.push_back(tp);
          }
        }
        if (theIDTracksAfterSelection.empty()) return StatusCode::SUCCESS;
        ATH_MSG_DEBUG("Number of tracks after ID trkSelector: " << theIDTracksAfterSelection.size());
        
        // Loop over J/psi candidates, select, collect up tracks used to build a J/psi
        std::vector<const xAOD::Vertex*> selectedJpsiCandidates;
        std::vector<const xAOD::TrackParticle*> jpsiTracks;
        for(auto vxcItr=importedJpsiCollection->cbegin(); vxcItr!=importedJpsiCollection->cend(); ++vxcItr) {
            // Check J/psi candidate invariant mass and skip if need be
            if (m_jpsiMassUpper>0.0 || m_jpsiMassLower >0.0) {
                xAOD::BPhysHelper jpsiCandidate(*vxcItr);
                double jpsiMass = jpsiCandidate.totalP(m_muonMasses).M();
                bool pass = JpsiUpsilonCommon::cutRange(jpsiMass, m_jpsiMassLower, m_jpsiMassUpper);
                if (!pass) continue;
            }
            selectedJpsiCandidates.push_back(*vxcItr);
 
            // Collect up tracks
        if(m_excludeCrossJpsiTracks){
                // Extract tracks from J/psi
                const xAOD::TrackParticle* jpsiTP1 = (*vxcItr)->trackParticle(0);
                const xAOD::TrackParticle* jpsiTP2 = (*vxcItr)->trackParticle(1);
                jpsiTracks.push_back(jpsiTP1);
                jpsiTracks.push_back(jpsiTP2);
        }
        }
 
 
        std::vector<double>  massHypotheses;
        if (m_kMassHyp) massHypotheses.push_back(kMass);
        if (m_piMassHyp) massHypotheses.push_back(piMass);
        if (!m_kMassHyp && !m_piMassHyp && m_BMassUpper>0.0) {
            massHypotheses.push_back(kMass); massHypotheses.push_back(piMass);
        }        
        std::vector<double> tripletMasses(m_muonMasses);
        // Attempt to fit each track with the two tracks from the J/psi candidates
        // Loop over J/psis
 
        std::vector<double> massCuts;
 
        TrackBag muonTracks;
        if (importedMuonCollection && m_excludeJpsiMuonsOnly) {
          for(auto muon : *importedMuonCollection){
            auto track = muon->trackParticle( xAOD::Muon::TrackParticleType::InnerDetectorTrackParticle);
            if(track==nullptr) continue;
            if(!JpsiUpsilonCommon::isContainedIn(track, theIDTracksAfterSelection)) continue;
            muonTracks.push_back(track);
          }
        }
        
        TrackBag electronTracks;
        ElectronBag theElectronsAfterSelection;
        if (importedElectronCollection && !importedElectronCollection->empty()) {
          for(auto electron : *importedElectronCollection) {
              if (!electron->trackParticleLink().isValid()) continue; // No electrons without ID tracks
              const xAOD::TrackParticle* elTrk(0);
              elTrk = electron->trackParticleLink().cachedElement();
              if (!elTrk) continue;
              theElectronsAfterSelection.push_back(electron); 
              electronTracks.push_back(elTrk); 
          }
          if (m_skipNoElectron && theElectronsAfterSelection.size() == 0) return StatusCode::SUCCESS;
          ATH_MSG_DEBUG("Number of electrons after selection: " << theElectronsAfterSelection.size());
        }
        
        std::vector<const xAOD::TrackParticle*> tracks(3, nullptr);
 
        for(auto jpsiItr=selectedJpsiCandidates.cbegin(); jpsiItr!=selectedJpsiCandidates.cend(); ++jpsiItr) {
 
            // Extract tracks from J/psi
           
            const xAOD::TrackParticle* jpsiTP1 = tracks[0] =  (*jpsiItr)->trackParticle(0);
            const xAOD::TrackParticle* jpsiTP2 = tracks[1] =  (*jpsiItr)->trackParticle(1);
 
        //If requested, only exclude duplicates in the same triplet
            if(!m_excludeCrossJpsiTracks){
                jpsiTracks.resize(2);
                jpsiTracks[0] = jpsiTP1;
                jpsiTracks[1] = jpsiTP2;
            }
 
            // Loop over ID tracks, call vertexing
            for (auto trkItr=theIDTracksAfterSelection.cbegin(); trkItr!=theIDTracksAfterSelection.cend(); ++trkItr) {
                if(bContainer.size() >= m_candidateLimit ){
                    ATH_MSG_WARNING("Hard Limit exceeded N=" << bContainer.size());
                    return StatusCode::SUCCESS;
                }
                if (!m_excludeJpsiMuonsOnly && JpsiUpsilonCommon::isContainedIn(*trkItr,jpsiTracks)) continue; // remove tracks which were used to build J/psi
                int linkedMuonTrk = 0;
                if (m_excludeJpsiMuonsOnly) {
                  linkedMuonTrk = JpsiUpsilonCommon::isContainedIn(*trkItr, muonTracks);
                  if (linkedMuonTrk) ATH_MSG_DEBUG("This id track is a muon track!");
                  if (JpsiUpsilonCommon::isContainedIn(*trkItr,jpsiTracks)) {
                    if (linkedMuonTrk) ATH_MSG_DEBUG("ID track removed: id track is slected to build Jpsi!");
                    continue;
                    
                  }
                }
                if(!m_electronCollectionKey.empty()){
                   int linkedElectronTrk = 0;
                   linkedElectronTrk = JpsiUpsilonCommon::isContainedIn(*trkItr, electronTracks);
                   if (linkedElectronTrk) ATH_MSG_DEBUG("This id track is an electron track!");
                   if (JpsiUpsilonCommon::isContainedIn(*trkItr,jpsiTracks)) {
                       if (linkedElectronTrk) ATH_MSG_DEBUG("ID track removed: id track is selected to build Jpsi!");
                       continue;
                   }
                   if (linkedElectronTrk < m_requiredNElectrons) {
                       ATH_MSG_DEBUG("Skipping Tracks with Electron " << linkedElectronTrk << " Limited to " << m_requiredNElectrons);
                       continue;
                   }
                }
                
                // Convert to TrackParticleBase
                const xAOD::TrackParticle* theThirdTP = tracks[2] = *trkItr;
 
                if (m_trkTrippletPt>0 && JpsiUpsilonCommon::getPt(jpsiTP1, jpsiTP2, theThirdTP) < m_trkTrippletPt ) continue; // track tripplet pT cut (daniel Scheirich)
                if(m_trkDeltaZ>0 &&
                   fabs(theThirdTP->z0() + theThirdTP->vz() - (*jpsiItr)->z()) > m_trkDeltaZ )
                    continue;
                if (linkedMuonTrk < m_requiredNMuons) {
                  ATH_MSG_DEBUG("Skipping Tracks with Muons " << linkedMuonTrk << " Limited to " << m_requiredNMuons);
                    continue;
                }
                 
                // apply mass cut on track tripplet if requested
                bool passRoughMassCuts(true);
 
                if (m_trkTrippletMassUpper>0.0 || m_trkTrippletMassLower>0.0) {
                     massCuts.clear();
                     if(m_kMassHyp)  massCuts.push_back(JpsiUpsilonCommon::getInvariantMass(tracks, {{m_muonMasses[0], m_muonMasses[1], kMass}}));
                     if(m_piMassHyp) massCuts.push_back(JpsiUpsilonCommon::getInvariantMass(tracks, {{m_muonMasses[0], m_muonMasses[1], piMass}}));
                     passRoughMassCuts = JpsiUpsilonCommon::cutRangeOR(massCuts, m_trkTrippletMassLower, m_trkTrippletMassUpper);
                 }
                 if (!passRoughMassCuts) continue;
 
 
                //Managed pointer, "release" if you don't want it deleted. Automatically "deleted" otherwise
                std::unique_ptr<xAOD::Vertex> bVertex( fit(ctx, tracks, importedTrackCollection, importedGSFTrackCollection));
                if (bVertex) {
 
                        // Chi2/DOF cut
                    double bChi2DOF = bVertex->chiSquared()/bVertex->numberDoF();
                    ATH_MSG_DEBUG("Candidate chi2/DOF is " << bChi2DOF);
                        
                    bool chi2CutPassed = (m_chi2cut <= 0.0 || bChi2DOF < m_chi2cut);
                    if(!chi2CutPassed) { ATH_MSG_DEBUG("Chi Cut failed!"); continue; }
 
                    // create the helper class
                    xAOD::BPhysHelper bHelper(bVertex.get());
                    // setRefTrks needs to be called after BPhysHelper is created if you want to access refitted track parameters
                    bHelper.setRefTrks();
                    // Decide whether to keep the candidate
                    bool masspTpassed = true;
                    if (m_BMassUpper>0.0 || m_BThresholdPt >0.0 || m_BMassLower > 0.0) {
                        masspTpassed = false;
                        for (double masshypo3rd : massHypotheses) {
                            tripletMasses.push_back(masshypo3rd); //Add third mass
                            TLorentzVector bMomentum = bHelper.totalP(tripletMasses);//Calulcate result
                            tripletMasses.pop_back(); //Remove 3rd mass - now same as beginning
                            double bpt = bMomentum.Pt();
                            bool PtPassed =  m_BThresholdPt <= 0.0 || (bpt >= m_BThresholdPt);
                            double bMass = bMomentum.M();
                            ATH_MSG_DEBUG("candidate pt/mass under track mass hypothesis of " << masshypo3rd << " is " << bpt << " / " << bMass);
                            bool masscut =  JpsiUpsilonCommon::cutRange(bMass, m_BMassLower, m_BMassUpper);  //( bMass >= m_BMassLower && bMass <= m_BMassUpper );
                            if(masscut && PtPassed) { masspTpassed = true; break; } 
                        }
                    }
                    if (masspTpassed) {
                        // Set links to J/psi
                        std::vector<const xAOD::Vertex*> theJpsiPreceding;
                        theJpsiPreceding.push_back(*jpsiItr);
                        bHelper.setPrecedingVertices(theJpsiPreceding, importedJpsiCollection);
                        bContainer.push_back(bVertex.release());
                    } else {
                       ATH_MSG_DEBUG("Cuts failed!");
                    }
                } else {ATH_MSG_DEBUG("Fitter failed!");}
                
            } // End of loop over tracks                        
            
        } // End of loop over J/psis
        ATH_MSG_DEBUG("bContainer size " << bContainer.size());
        return StatusCode::SUCCESS;
        
    }
    
    // *********************************************************************************
    
    // ---------------------------------------------------------------------------------
    // fit - does the fit
    // ---------------------------------------------------------------------------------
    
    std::unique_ptr<xAOD::Vertex> JpsiPlus1Track::fit(const EventContext& ctx, const std::vector<const xAOD::TrackParticle*> &inputTracks, const xAOD::TrackParticleContainer* importedTrackCollection, const xAOD::TrackParticleContainer* gsfCollection) const {
        
        std::unique_ptr<Trk::IVKalState> state = m_VKVFitter->makeState(ctx);
        
        // Set the mass constraint if requested by user (default=true)
        // Can be set by user (m_altMassConstraint) - default is -1.0.
        // If < 0.0, uses J/psi (default)
        // If > 0.0, uses the value provided
        constexpr double jpsiTableMass = ParticleConstants::JpsiMassInMeV;
 
        if (m_useMassConst) {
            m_VKVFitter->setMassInputParticles(m_muonMasses, *state);
            std::array<int,2> indices = {1, 2};
            if (m_altMassConst<0.0) m_VKVFitter->setMassForConstraint(jpsiTableMass,indices, *state);
            if (m_altMassConst>0.0) m_VKVFitter->setMassForConstraint(m_altMassConst,indices, *state);
        }
        
        // Do the fit itself.......
        Amg::Vector3D startingPoint(0,0,0);
        StatusCode sc=m_VKVFitter->VKalVrtFitFast(inputTracks, startingPoint, *state);
        if(sc.isFailure()){
            startingPoint = Amg::Vector3D(0,0,0);
        }
        std::unique_ptr<xAOD::Vertex> theResult = m_VKVFitter->fit(inputTracks, startingPoint, *state);
 
        // Added by ASC
        if(theResult){
           std::vector<ElementLink<DataVector<xAOD::TrackParticle> > > newLinkVector;
           for(unsigned int i=0; i< theResult->trackParticleLinks().size(); i++)
           {
              ElementLink<DataVector<xAOD::TrackParticle> > mylink=theResult->trackParticleLinks()[i]; //makes a copy (non-const)
              mylink.setStorableObject( m_useGSFTrack[i] ?  *gsfCollection : *importedTrackCollection, true);
              newLinkVector.push_back( mylink );
           }
           theResult->clearTracks();
           theResult->setTrackParticleLinks( newLinkVector );
        }
 
    
        return theResult;
        
    }
    
    
 
    
} // End of namespace