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 ( )

inline

Definition at line 35 of file ConversionHitChecker.h.

{}

ConversionHitChecker::~ConversionHitChecker ( )

inline

Definition at line 36 of file ConversionHitChecker.h.

References nHitsBeforeVtx(), nSharedHits(), and HiIsolationCommonParameters_cff::track.

{}

Member Function Documentation

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

Definition at line 9 of file ConversionHitChecker.cc.

References reco::Vertex::covariance(), listHistos::decayLength, dot(), h, hcalSimParameters_cfi::hb, j, mag2(), nhits, position, rpcPointValidation_cfi::recHit, reco::TrackExtraBase::recHitsBegin(), reco::TrackExtraBase::recHitsSize(), Measurement1DFloat::significance(), mathSSE::sqrt(), reco::TrackExtraBase::trajParams(), reco::Vertex::x(), reco::Vertex::y(), and reco::Vertex::z().

Referenced by ConversionProducer::buildCollection(), and ~ConversionHitChecker().

                                                                                                                                                        {

  // 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????)
  auto hb = track.recHitsBegin();
  unsigned int ih=0;
  for(;ih<track.recHitsSize();++ih) {
    auto recHit = *(hb+ih);
    if (recHit->isValid()) break; 
  }
  auto recHit = *(hb+ih);
  unsigned int closest=ih;
  auto globalPosition = recHit->surface()->toGlobal(trajParams[0].position());
  auto distance2 = (vtxPos - globalPosition).mag2();
  int nhits = 1;
  for(unsigned int h=ih+1;h<track.recHitsSize();++h){

    //check if next valid hit is farther away from vertex than existing closest
    auto nextHit = *(hb+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 = *(hb+closest);
  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);

}

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

Definition at line 69 of file ConversionHitChecker.cc.

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

Referenced by ConversionProducer::buildCollection(), and ~ConversionHitChecker().

                                                                                            {
 
  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;

}