ConversionHitChecker Class Reference

#include <ConversionHitChecker.h>

Public Member Functions
	ConversionHitChecker ()
std::pair< uint8_t, Measurement1DFloat >	nHitsBeforeVtx (const reco::TrackExtra &track, const reco::Vertex &vtx, float sigmaTolerance=3.0) const
uint8_t	nSharedHits (const reco::Track &trk1, const reco::Track &trk2) const
	~ConversionHitChecker ()

Detailed Description

Author

J.Bendavid

Version

Check hits along a Trajectory and count how many are before the vertex position. (taking into account the uncertainty in the vertex and hit positions. Also returns a the signed decay length and uncertainty from the closest hit on the track to the vertex position.

Definition at line 31 of file ConversionHitChecker.h.

Constructor & Destructor Documentation

ConversionHitChecker()

ConversionHitChecker::ConversionHitChecker ( )

inline

Definition at line 33 of file ConversionHitChecker.h.

{}

~ConversionHitChecker()

ConversionHitChecker::~ConversionHitChecker ( )

inline

Definition at line 34 of file ConversionHitChecker.h.

{}

Member Function Documentation

nHitsBeforeVtx()

std::pair< uint8_t, Measurement1DFloat > ConversionHitChecker::nHitsBeforeVtx	(	const reco::TrackExtra &	track,
		const reco::Vertex &	vtx,
		float	sigmaTolerance = 3.0
	)		const

Definition at line 8 of file ConversionHitChecker.cc.

                                                                                                        {
  // track hits are always inout
 
  GlobalPoint vtxPos(vtx.x(), vtx.y(), vtx.z());
 
  auto const &trajParams = track.trajParams();
 
  //iterate inside out, when distance to vertex starts increasing, we are at the closest hit
  // the first (and last, btw) hit is always valid... (apparntly not..., conversion is different????)
  TrackingRecHit const *recHit = *track.recHits().begin();
  unsigned int closest = 0;
  for (auto const &hit : track.recHits()) {
    if (hit->isValid()) {
      recHit = hit;
      break;
    }
    ++closest;
  }
  auto globalPosition = recHit->surface()->toGlobal(trajParams[0].position());
  auto distance2 = (vtxPos - globalPosition).mag2();
  int nhits = 1;
  for (unsigned int h = closest + 1; h < track.recHitsSize(); ++h) {
    //check if next valid hit is farther away from vertex than existing closest
    auto nextHit = track.recHit(h);
    if (!nextHit->isValid())
      continue;
    globalPosition = nextHit->surface()->toGlobal(trajParams[h].position());
    auto nextDistance2 = (vtxPos - globalPosition).mag2();
    if (nextDistance2 > distance2)
      break;
 
    distance2 = nextDistance2;
    ++nhits;
    closest = h;
  }
 
  //compute signed decaylength significance for closest hit and check if it is before the vertex
  //if not then we need to subtract it from the count of hits before the vertex, since it has been implicitly included
  recHit = track.recHit(closest).get();
  auto momDir = recHit->surface()->toGlobal(trajParams[closest].direction());
  globalPosition = recHit->surface()->toGlobal(trajParams[closest].position());
  float decayLengthHitToVtx = (vtxPos - globalPosition).dot(momDir);
 
  AlgebraicVector3 j;
  j[0] = momDir.x();
  j[1] = momDir.y();
  j[2] = momDir.z();
  float vertexError2 = ROOT::Math::Similarity(j, vtx.covariance());
  auto decayLenError = std::sqrt(vertexError2);
 
  Measurement1DFloat decayLength(decayLengthHitToVtx, decayLenError);
 
  if (decayLength.significance() <
      sigmaTolerance) {  //decay length is not (significantly) positive, so hit is consistent with the vertex position or late
                         //subtract it from wrong hits count
    --nhits;
  }
 
  return std::pair<unsigned int, Measurement1DFloat>(nhits, decayLength);
}

References listHistos::decayLength, dot(), h, dqmiolumiharvest::j, mag2(), nhits, position, rpcPointValidation_cfi::recHit, mathSSE::sqrt(), HLT_FULL_cff::track, and extraflags_cff::vtx.

Referenced by ConversionProducer::buildCollection().

nSharedHits()

uint8_t ConversionHitChecker::nSharedHits	(	const reco::Track &	trk1,
		const reco::Track &	trk2
	)		const

Definition at line 71 of file ConversionHitChecker.cc.

                                                                                            {
  uint8_t nShared = 0;
 
  for (trackingRecHit_iterator iHit1 = trk1.recHitsBegin(); iHit1 != trk1.recHitsEnd(); ++iHit1) {
    const TrackingRecHit *hit1 = (*iHit1);
    if (hit1->isValid()) {
      for (trackingRecHit_iterator iHit2 = trk2.recHitsBegin(); iHit2 != trk2.recHitsEnd(); ++iHit2) {
        const TrackingRecHit *hit2 = (*iHit2);
        if (hit2->isValid() && hit1->sharesInput(hit2, TrackingRecHit::some)) {
          ++nShared;
        }
      }
    }
  }
 
  return nShared;
}

References TrackingRecHit::isValid(), reco::Track::recHitsBegin(), reco::Track::recHitsEnd(), TrackingRecHit::sharesInput(), and TrackingRecHit::some.

Referenced by ConversionProducer::buildCollection().