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SignedTransverseImpactParameter Class Reference

Transverse track impact parameter signed according to the jet direction. More...

#include <RecoBTag/BTagTools/interface/SignedTransverseImpactParameter.h>

List of all members.

Public Member Functions
std::pair< bool, Measurement1D >	apply (const reco::TransientTrack &, const GlobalVector &, const reco::Vertex &) const
	SignedTransverseImpactParameter ()
std::pair< bool, Measurement1D >	zImpactParameter (const reco::TransientTrack &, const GlobalVector &, const reco::Vertex &) const

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Detailed Description

Transverse track impact parameter signed according to the jet direction.

Definition at line 16 of file SignedTransverseImpactParameter.h.

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Constructor & Destructor Documentation

SignedTransverseImpactParameter::SignedTransverseImpactParameter

(

)

[inline]

Definition at line 22 of file SignedTransverseImpactParameter.h.

{};

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Member Function Documentation

pair< bool, Measurement1D > SignedTransverseImpactParameter::apply	(	const reco::TransientTrack &	track,
		const GlobalVector &	direction,
		const reco::Vertex &	vertex
	)			const

Definition at line 20 of file SignedTransverseImpactParameter.cc.

References funct::A, funct::abs(), reco::Vertex::covariance(), reco::TransientTrack::field(), TrajectoryStateOnSurface::freeState(), reco::TransientTrack::impactPointState(), LogDebug, funct::sqrt(), PV3DBase< T, PVType, FrameType >::x(), reco::Vertex::x(), x, PV3DBase< T, PVType, FrameType >::y(), reco::Vertex::y(), PV3DBase< T, PVType, FrameType >::z(), and reco::Vertex::z().

Referenced by ImpactParameterAlgorithm::tag().

       {

  TrajectoryStateOnSurface stateOnSurface = track.impactPointState();

  FreeTrajectoryState * FTS =  stateOnSurface.freeState(); //aRecTrack.stateAtFirstPoint().freeTrajectoryState());

  GlobalPoint vertexPosition(vertex.x(),vertex.y(),vertex.z());
 
  double theValue;
  double theError;
  TransverseImpactPointExtrapolator TIPE(track.field());
  TrajectoryStateOnSurface TSOS = TIPE.extrapolate(*FTS, vertexPosition);

  if(!TSOS.isValid()){
    theValue=0.;
    theError=0.;
  }
  else{
    
    GlobalPoint D0(TSOS.globalPosition());
    
    GlobalVector DD0(D0.x()-vertex.x(),D0.y()-vertex.y(),0.);
    GlobalVector JetDir(direction);
    double ps = DD0.dot(JetDir);
    theValue = DD0.mag()*(ps/abs(ps));

    //error calculation
    
    AlgebraicVector6 deriv;
    AlgebraicVector3 deriv_v;
    GlobalVector dd0 = DD0.unit();//check
    
    deriv_v[0] = - dd0.x();
    deriv_v[1] = - dd0.y();
    deriv_v[2] = - dd0.z();
    
    deriv[0] = dd0.x();
    deriv[1] = dd0.y();
    deriv[2] = dd0.z();
    deriv[3] =  0.;
    deriv[4] =  0.;
    deriv[5] =  0.;
    //cout << TSOS.cartesianError().matrix() << endl;
    //cout << deriv << endl;   
    double E1 = ROOT::Math::Similarity(deriv,TSOS.cartesianError().matrix());
    double E2 = ROOT::Math::Similarity(deriv_v,vertex.covariance());
             // (aJet.vertex().positionError().matrix()).similarity(deriv_v);
    theError = sqrt(E1+E2);
    LogDebug("BTagTools") << "Tk error : " << E1 << " , Vtx error : " << E2 << "  tot : " << theError;

 }//end if
  
  bool x = true;
  
  Measurement1D A(theValue, theError);
  return pair<bool,Measurement1D>(x,A);
}// end constructor declaration

pair< bool, Measurement1D > SignedTransverseImpactParameter::zImpactParameter	(	const reco::TransientTrack &	track,
		const GlobalVector &	direction,
		const reco::Vertex &	vertex
	)			const

Definition at line 82 of file SignedTransverseImpactParameter.cc.

References reco::Vertex::covariance(), reco::TransientTrack::field(), reco::TransientTrack::impactPointState(), LogDebug, funct::sqrt(), true, PV3DBase< T, PVType, FrameType >::x(), reco::Vertex::x(), PV3DBase< T, PVType, FrameType >::y(), reco::Vertex::y(), PV3DBase< T, PVType, FrameType >::z(), and reco::Vertex::z().

                                                                     {
  
  TransverseImpactPointExtrapolator TIPE(track.field()) ;
  TrajectoryStateOnSurface TSOS  = track.impactPointState();

  if ( !TSOS.isValid() ) {
    LogDebug("BTagTools") << "====>>>> SignedTransverseImpactParameter::zImpactParameter : TSOS not valid"  ;
    return pair<bool,Measurement1D> (false,Measurement1D(0.0,0.0)) ;
  }

  GlobalPoint PV(vertex.x(),vertex.y(),vertex.z());
  TrajectoryStateOnSurface statePCA = TIPE.extrapolate( TSOS , PV ) ;

  if ( !statePCA.isValid() ) {
    LogDebug("BTagTools") << "====>>>> SignedTransverseImpactParameter::zImpactParameter : statePCA not valid"  ;
    return pair<bool,Measurement1D> (false,Measurement1D(0.0,0.0)) ;
  }

  GlobalPoint PCA = statePCA.globalPosition() ;

  // sign as in rphi
  GlobalVector PVPCA ( PCA.x()-PV.x() , PCA.y()-PV.y() , 0. );
  GlobalVector JetDir(direction);
  double sign = PVPCA.dot(JetDir);
  sign /= fabs(sign) ;

  // z IP
  double deltaZ = fabs(PCA.z()-PV.z()) * sign ;
  
  // error
  double errPvZ2 = vertex.covariance()(2,2) ;
  //CW  cout << "CW number or rows and columns : " << statePCA.cartesianError().matrix().num_row() << " , "
  //CW                                             << statePCA.cartesianError().matrix().num_col() << endl ;
  double errTrackZ2 =  statePCA.cartesianError().matrix()(2,2) ;
  double errZ = sqrt ( errPvZ2 + errTrackZ2 ) ;

  // CW alt. -> gives the same!!
  //  double errTZAlt = statePCA.localError().matrix()[4][4] ;
  //CW
  
  return pair<bool,Measurement1D> ( true , Measurement1D( deltaZ , errZ ) ) ;
}

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The documentation for this class was generated from the following files:

• RecoBTag/BTagTools/interface/SignedTransverseImpactParameter.h
• RecoBTag/BTagTools/src/SignedTransverseImpactParameter.cc

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