TrackExtrapolator.cc

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#include "RecoJets/JetAssociationProducers/interface/TrackExtrapolator.h"

#include <vector>

//
// constructors and destructor
//
TrackExtrapolator::TrackExtrapolator(const edm::ParameterSet& iConfig)
    : tracksSrc_(consumes(iConfig.getParameter<edm::InputTag>("trackSrc"))),
      fieldToken_(esConsumes()),
      propagatorToken_(esConsumes(edm::ESInputTag("", "SteppingHelixPropagatorAlong"))),
      ecalDetIdAssociatorToken_(esConsumes(edm::ESInputTag("", "EcalDetIdAssociator"))),
      trackQuality_(reco::TrackBase::qualityByName(iConfig.getParameter<std::string>("trackQuality"))) {
  if (trackQuality_ == reco::TrackBase::undefQuality) {  // we have a problem
    throw cms::Exception("InvalidInput") << "Unknown trackQuality value '"
                                         << iConfig.getParameter<std::string>("trackQuality")
                                         << "'. See possible values in 'reco::TrackBase::qualityByName'";
  }

  produces<std::vector<reco::TrackExtrapolation>>();
}

TrackExtrapolator::~TrackExtrapolator() {}

//
// member functions
//

// ------------ method called on each new Event  ------------
void TrackExtrapolator::produce(edm::Event& iEvent, const edm::EventSetup& iSetup) {
  // get stuff from Event Setup
  auto const& field = iSetup.getData(fieldToken_);
  auto const& propagator = iSetup.getData(propagatorToken_);
  FiducialVolume const& ecalvolume = iSetup.getData(ecalDetIdAssociatorToken_).volume();

  // get stuff from Event
  edm::Handle<reco::TrackCollection> tracks_h;
  iEvent.getByToken(tracksSrc_, tracks_h);

  auto extrapolations = std::make_unique<std::vector<reco::TrackExtrapolation>>();

  // Get list of tracks we want to extrapolate
  std::vector<reco::TrackRef> goodTracks;
  for (reco::TrackCollection::const_iterator trkBegin = tracks_h->begin(), trkEnd = tracks_h->end(), itrk = trkBegin;
       itrk != trkEnd;
       ++itrk) {
    reco::TrackBase::TrackQuality trackQuality = reco::TrackBase::TrackQuality(trackQuality_);

    // Cut on track quality
    if (itrk->quality(trackQuality)) {
      goodTracks.push_back(reco::TrackRef(tracks_h, itrk - trkBegin));
    }
  }
  std::vector<reco::TrackBase::Point> vresultPos(1);
  std::vector<reco::TrackBase::Vector> vresultMom(1);

  // Now loop through the list of tracks and extrapolate them
  for (std::vector<reco::TrackRef>::const_iterator trkBegin = goodTracks.begin(),
                                                   trkEnd = goodTracks.end(),
                                                   itrk = trkBegin;
       itrk != trkEnd;
       ++itrk) {
    if (propagateTrackToVolume(**itrk, field, propagator, ecalvolume, vresultPos[0], vresultMom[0])) {
      extrapolations->push_back(reco::TrackExtrapolation(*itrk, vresultPos, vresultMom));
    }
  }
  iEvent.put(std::move(extrapolations));
}

// -----------------------------------------------------------------------------
//
bool TrackExtrapolator::propagateTrackToVolume(const reco::Track& fTrack,
                                               const MagneticField& fField,
                                               const Propagator& fPropagator,
                                               const FiducialVolume& volume,
                                               reco::TrackBase::Point& resultPos,
                                               reco::TrackBase::Vector& resultMom) {
  GlobalPoint trackPosition(fTrack.vx(), fTrack.vy(), fTrack.vz());   // reference point
  GlobalVector trackMomentum(fTrack.px(), fTrack.py(), fTrack.pz());  // reference momentum
  if (fTrack.extra().isAvailable()) {                                 // use outer point information, if available
    trackPosition = GlobalPoint(fTrack.outerX(), fTrack.outerY(), fTrack.outerZ());
    trackMomentum = GlobalVector(fTrack.outerPx(), fTrack.outerPy(), fTrack.outerPz());
  }

  GlobalTrajectoryParameters trackParams(trackPosition, trackMomentum, fTrack.charge(), &fField);
  FreeTrajectoryState trackState(trackParams);

  TrajectoryStateOnSurface propagatedInfo = fPropagator.propagate(
      trackState, *Cylinder::build(volume.minR(), Surface::PositionType(0, 0, 0), Surface::RotationType()));

  // if the track went through either side of the endcaps, repropagate the track
  double minz = volume.minZ();
  if (propagatedInfo.isValid() && propagatedInfo.globalPosition().z() > minz) {
    propagatedInfo =
        fPropagator.propagate(trackState, *Plane::build(Surface::PositionType(0, 0, minz), Surface::RotationType()));

  } else if (propagatedInfo.isValid() && propagatedInfo.globalPosition().z() < -minz) {
    propagatedInfo =
        fPropagator.propagate(trackState, *Plane::build(Surface::PositionType(0, 0, -minz), Surface::RotationType()));
  }

  if (propagatedInfo.isValid()) {
    resultPos = propagatedInfo.globalPosition();
    resultMom = propagatedInfo.globalMomentum();
    return true;
  } else {
    return false;
  }
}

//define this as a plug-in
DEFINE_FWK_MODULE(TrackExtrapolator);