MuonIdTruthInfo.cc

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#include "RecoMuon/MuonIdentification/interface/MuonIdTruthInfo.h"
#include "SimDataFormats/Track/interface/SimTrackContainer.h"
#include "SimDataFormats/TrackingHit/interface/PSimHitContainer.h"
#include "DataFormats/MuonDetId/interface/CSCDetId.h"
#include "DataFormats/MuonDetId/interface/DTChamberId.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "Geometry/Records/interface/GlobalTrackingGeometryRecord.h"
#include "Geometry/CommonDetUnit/interface/GeomDet.h"
#include "FWCore/Framework/interface/ConsumesCollector.h"

void MuonIdTruthInfo::registerConsumes(edm::ConsumesCollector& iC) {
  iC.mayConsume<edm::SimTrackContainer>(edm::InputTag("g4SimHits", ""));
  iC.mayConsume<edm::PSimHitContainer>(edm::InputTag("g4SimHits", "MuonDTHits"));
  iC.mayConsume<edm::PSimHitContainer>(edm::InputTag("g4SimHits", "MuonCSCHits"));
}

void MuonIdTruthInfo::truthMatchMuon(const edm::Event& iEvent, const edm::EventSetup& iSetup, reco::Muon& aMuon) {
  // get a list of simulated track and find a track with the best match to
  // the muon.track(). Use its id and chamber id to localize hits
  // If a hit has non-zero local z coordinate, it's position wrt
  // to the center of a chamber is extrapolated by a straight line

  edm::Handle<edm::SimTrackContainer> simTracks;
  iEvent.getByLabel<edm::SimTrackContainer>("g4SimHits", "", simTracks);
  if (!simTracks.isValid()) {
    LogTrace("MuonIdentification") << "No tracks found";
    return;
  }

  // get the tracking Geometry
  edm::ESHandle<GlobalTrackingGeometry> geometry;
  iSetup.get<GlobalTrackingGeometryRecord>().get(geometry);
  if (!geometry.isValid())
    throw cms::Exception("FatalError") << "Unable to find GlobalTrackingGeometryRecord in event!\n";

  float bestMatchChi2 = 9999;  //minimization creteria
  unsigned int bestMatch = 0;
  const unsigned int offset = 0;  // kludge to fix a problem in trackId matching between tracks and hits.

  for (edm::SimTrackContainer::const_iterator simTrk = simTracks->begin(); simTrk != simTracks->end(); simTrk++) {
    float chi2 = matchChi2(*aMuon.track().get(), *simTrk);
    if (chi2 > bestMatchChi2)
      continue;
    bestMatchChi2 = chi2;
    bestMatch = simTrk->trackId();
  }

  bestMatch -= offset;

  std::vector<reco::MuonChamberMatch>& matches = aMuon.matches();
  int numberOfTruthMatchedChambers = 0;

  // loop over chambers
  for (std::vector<reco::MuonChamberMatch>::iterator chamberMatch = matches.begin(); chamberMatch != matches.end();
       chamberMatch++) {
    if (chamberMatch->id.det() != DetId::Muon) {
      edm::LogWarning("MuonIdentification") << "Detector id of a muon chamber corresponds to not a muon detector";
      continue;
    }
    reco::MuonSegmentMatch bestSegmentMatch;
    double distance = 99999;

    if (chamberMatch->id.subdetId() == MuonSubdetId::DT) {
      DTChamberId detId(chamberMatch->id.rawId());

      edm::Handle<edm::PSimHitContainer> simHits;
      iEvent.getByLabel("g4SimHits", "MuonDTHits", simHits);
      if (simHits.isValid()) {
        for (edm::PSimHitContainer::const_iterator hit = simHits->begin(); hit != simHits->end(); hit++)
          if (hit->trackId() == bestMatch)
            checkSimHitForBestMatch(bestSegmentMatch, distance, *hit, detId, geometry);
      } else
        LogTrace("MuonIdentification") << "No DT simulated hits are found";
    }

    if (chamberMatch->id.subdetId() == MuonSubdetId::CSC) {
      CSCDetId detId(chamberMatch->id.rawId());

      edm::Handle<edm::PSimHitContainer> simHits;
      iEvent.getByLabel("g4SimHits", "MuonCSCHits", simHits);
      if (simHits.isValid()) {
        for (edm::PSimHitContainer::const_iterator hit = simHits->begin(); hit != simHits->end(); hit++)
          if (hit->trackId() == bestMatch)
            checkSimHitForBestMatch(bestSegmentMatch, distance, *hit, detId, geometry);
      } else
        LogTrace("MuonIdentification") << "No CSC simulated hits are found";
    }
    if (distance < 9999) {
      chamberMatch->truthMatches.push_back(bestSegmentMatch);
      numberOfTruthMatchedChambers++;
      LogTrace("MuonIdentification") << "Best truth matched hit:"
                                     << "\tDetId: " << chamberMatch->id.rawId() << "\n"
                                     << "\tprojection: ( " << bestSegmentMatch.x << ", " << bestSegmentMatch.y
                                     << " )\n";
    }
  }
  LogTrace("MuonIdentification") << "Truth matching summary:\n\tnumber of chambers: " << matches.size()
                                 << "\n\tnumber of truth matched chambers: " << numberOfTruthMatchedChambers << "\n";
}

void MuonIdTruthInfo::checkSimHitForBestMatch(reco::MuonSegmentMatch& segmentMatch,
                                              double& distance,
                                              const PSimHit& hit,
                                              const DetId& chamberId,
                                              const edm::ESHandle<GlobalTrackingGeometry>& geometry) {
  printf("DONT FORGET TO CALL REGISTERCONSUMES()\n");

  // find the hit position projection at the reference surface of the chamber:
  // first get entry and exit point of the hit in the global coordinates, then
  // get local coordinates of these points wrt the chamber and then find the
  // projected X-Y coordinates

  const GeomDet* chamberGeometry = geometry->idToDet(chamberId);
  const GeomDet* simUnitGeometry = geometry->idToDet(DetId(hit.detUnitId()));

  if (chamberGeometry && simUnitGeometry) {
    LocalPoint entryPoint = chamberGeometry->toLocal(simUnitGeometry->toGlobal(hit.entryPoint()));
    LocalPoint exitPoint = chamberGeometry->toLocal(simUnitGeometry->toGlobal(hit.exitPoint()));
    LocalVector direction = exitPoint - entryPoint;
    if (fabs(direction.z()) > 0.001) {
      LocalPoint projection = entryPoint - direction * (entryPoint.z() / direction.z());
      if (fabs(projection.z()) > 0.001)
        edm::LogWarning("MuonIdentification") << "z coordinate of the hit projection must be zero and it's not!\n";

      double new_distance = 99999;
      if (entryPoint.z() * exitPoint.z() < -1)  // changed sign, so the reference point is inside
        new_distance = 0;
      else {
        if (fabs(entryPoint.z()) < fabs(exitPoint.z()))
          new_distance = fabs(entryPoint.z());
        else
          new_distance = fabs(exitPoint.z());
      }

      if (new_distance < distance) {
        // find a SimHit closer to the reference surface, update segmentMatch
        segmentMatch.x = projection.x();
        segmentMatch.y = projection.y();
        segmentMatch.xErr = 0;
        segmentMatch.yErr = 0;
        segmentMatch.dXdZ = direction.x() / direction.z();
        segmentMatch.dYdZ = direction.y() / direction.z();
        segmentMatch.dXdZErr = 0;
        segmentMatch.dYdZErr = 0;
        distance = new_distance;
        LogTrace("MuonIdentificationVerbose")
            << "Better truth matched segment found:\n"
            << "\tDetId: " << chamberId.rawId() << "\n"
            << "\tentry point: ( " << entryPoint.x() << ", " << entryPoint.y() << ", " << entryPoint.z() << " )\n"
            << "\texit point: ( " << exitPoint.x() << ", " << exitPoint.y() << ", " << exitPoint.z() << " )\n"
            << "\tprojection: ( " << projection.x() << ", " << projection.y() << ", " << projection.z() << " )\n";
      }
    }
  } else {
    if (!chamberGeometry)
      edm::LogWarning("MuonIdentification") << "Cannot get chamber geomtry for DetId: " << chamberId.rawId();
    if (!simUnitGeometry)
      edm::LogWarning("MuonIdentification") << "Cannot get detector unit geomtry for DetId: " << hit.detUnitId();
  }
}

double MuonIdTruthInfo::matchChi2(const reco::Track& recoTrk, const SimTrack& simTrk) {
  double deltaPhi = fabs(recoTrk.phi() - simTrk.momentum().phi());
  if (deltaPhi > 1.8 * 3.1416)
    deltaPhi = 2 * 3.1416 - deltaPhi;  // take care of phi discontinuity
  return pow((recoTrk.p() - simTrk.momentum().rho()) / simTrk.momentum().rho(), 2) + pow(deltaPhi / (2 * 3.1416), 2) +
         pow((recoTrk.theta() - simTrk.momentum().theta()) / 3.1416, 2);
}