TransverseImpactPointExtrapolator Class Reference

#include <TransverseImpactPointExtrapolator.h>

Public Member Functions
TrajectoryStateOnSurface	extrapolate (const FreeTrajectoryState &fts, const GlobalPoint &vtx) const
	extrapolation with default (=geometrical) propagator More...
TrajectoryStateOnSurface	extrapolate (const TrajectoryStateOnSurface tsos, const GlobalPoint &vtx) const
	as above, but from TrajectoryStateOnSurface More...
TrajectoryStateOnSurface	extrapolate (const FreeTrajectoryState &fts, const GlobalPoint &vtx, const Propagator &u) const
	extrapolation with user-supplied propagator More...
TrajectoryStateOnSurface	extrapolate (const TrajectoryStateOnSurface tsos, const GlobalPoint &vtx, const Propagator &u) const
	as above, but from TrajectoryStateOnSurface More...
	TransverseImpactPointExtrapolator ()
	constructor with default geometrical propagator More...
	TransverseImpactPointExtrapolator (const MagneticField *field)
	constructor with default geometrical propagator More...
	TransverseImpactPointExtrapolator (const Propagator &u)
	constructor with user-supplied propagator More...

Private Member Functions
TrajectoryStateOnSurface	doExtrapolation (const TrajectoryStateOnSurface tsos, const GlobalPoint &vtx, const Propagator &u) const
	extrapolation of (multi) TSOS with (internal or user-supplied) propagator More...
TrajectoryStateOnSurface	doExtrapolation (const FreeTrajectoryState &fts, const GlobalPoint &vtx, const Propagator &u) const
	extrapolation of (single) FTS with (internal or user-supplied) propagator More...
ReferenceCountingPointer < BoundPlane >	tipSurface (const GlobalPoint &position, const GlobalVector &momentum, const double &signedTransverseRadius, const GlobalPoint &vtx) const
	computation of the TIP surface More...

Private Attributes
DeepCopyPointerByClone < Propagator >	thePropagator

Detailed Description

Extrapolate to impact point with respect to vtx, i.e. point of closest approach to vtx in 2D. The surface of the returned TrajectoryStateOnSurface is chosen centred on vtx; the axes of the local coordinate system (x_loc, y_loc, z_loc) are z_loc // trajectory direction in transverse plane at impact point; x_loc normal to trajectory and along impact vector (impact point - vtx); y_loc forms a right-handed system with the other axes.

Definition at line 26 of file TransverseImpactPointExtrapolator.h.

Constructor & Destructor Documentation

TransverseImpactPointExtrapolator::TransverseImpactPointExtrapolator

(

)

constructor with default geometrical propagator

Definition at line 15 of file TransverseImpactPointExtrapolator.cc.

                                                                      :
  thePropagator(0) {}

TransverseImpactPointExtrapolator::TransverseImpactPointExtrapolator

(

const MagneticField *

field

)

constructor with default geometrical propagator

Definition at line 19 of file TransverseImpactPointExtrapolator.cc.

                                                                                                :
  thePropagator(new AnalyticalPropagator(field, anyDirection)) {}

TransverseImpactPointExtrapolator::TransverseImpactPointExtrapolator

(

const Propagator &

u

)

constructor with user-supplied propagator

Definition at line 22 of file TransverseImpactPointExtrapolator.cc.

References anyDirection, Propagator::setPropagationDirection(), and thePropagator.

                                                                                         :
  thePropagator(u.clone()) 
{
  thePropagator->setPropagationDirection(anyDirection);
}

Member Function Documentation

TrajectoryStateOnSurface TransverseImpactPointExtrapolator::doExtrapolation ( const TrajectoryStateOnSurface  tsos, const GlobalPoint &  vtx, const Propagator &  u  ) const

private

extrapolation of (multi) TSOS with (internal or user-supplied) propagator

Definition at line 69 of file TransverseImpactPointExtrapolator.cc.

References Vector3DBase< T, FrameTag >::cross(), TrajectoryStateOnSurface::freeState(), TrajectoryStateOnSurface::globalMomentum(), TrajectoryStateOnSurface::globalPosition(), LogDebug, PlaneBuilder::plane(), Propagator::propagate(), idealTransformation::rotation, tipSurface(), FreeTrajectoryState::transverseCurvature(), TrajectoryStateOnSurface::transverseCurvature(), csvLumiCalc::unit, PV3DBase< T, PVType, FrameType >::x(), and PV3DBase< T, PVType, FrameType >::y().

Referenced by extrapolate().

{
  //
  // Compute tip surface
  //
  if (fabs(tsos.freeState()->transverseCurvature())<1.E-6){
    LogDebug("TransverseImpactPointExtrapolator")<< "negligeable curvature: using a trick to extrapolate:\n"<<tsos;

    //0T field probably
    //x is perpendicular to the momentum
    GlobalVector xLocal = GlobalVector(-tsos.globalMomentum().y(),tsos.globalMomentum().x(),0).unit();
    //y along global Z
    GlobalVector yLocal(0.,0.,1.);
    //z accordingly
    GlobalVector zLocal(xLocal.cross(yLocal));

    Surface::PositionType origin(vtx);
    Surface::RotationType rotation(xLocal,yLocal,zLocal);
    ReferenceCountingPointer<BoundPlane> surface =  PlaneBuilder().plane(origin,rotation);
    
    return p.propagate(*tsos.freeState(),*surface);
  }else{
  ReferenceCountingPointer<BoundPlane> surface = 
    tipSurface(tsos.globalPosition(),tsos.globalMomentum(),
           1./tsos.transverseCurvature(),vtx);
  //
  // propagate
  //
  return p.propagate(tsos,*surface);
  }
}

TrajectoryStateOnSurface TransverseImpactPointExtrapolator::doExtrapolation ( const FreeTrajectoryState &  fts, const GlobalPoint &  vtx, const Propagator &  u  ) const

private

extrapolation of (single) FTS with (internal or user-supplied) propagator

Definition at line 104 of file TransverseImpactPointExtrapolator.cc.

References Vector3DBase< T, FrameTag >::cross(), LogDebug, FreeTrajectoryState::momentum(), PlaneBuilder::plane(), FreeTrajectoryState::position(), Propagator::propagate(), idealTransformation::rotation, tipSurface(), FreeTrajectoryState::transverseCurvature(), csvLumiCalc::unit, PV3DBase< T, PVType, FrameType >::x(), and PV3DBase< T, PVType, FrameType >::y().

{
  //
  // Compute tip surface
  //
  if (fabs(fts.transverseCurvature())<1.E-6){
    LogDebug("TransverseImpactPointExtrapolator")<< "negligeable curvature: using a trick to extrapolate:\n"<<fts;

    //0T field probably
    //x is perpendicular to the momentum
    GlobalVector xLocal = GlobalVector(-fts.momentum().y(),fts.momentum().x(),0).unit();
    //y along global Z
    GlobalVector yLocal(0.,0.,1.);
    //z accordingly
    GlobalVector zLocal(xLocal.cross(yLocal));

    Surface::PositionType origin(vtx);
    Surface::RotationType rotation(xLocal,yLocal,zLocal);
    ReferenceCountingPointer<BoundPlane> surface =  PlaneBuilder().plane(origin,rotation);
    
    return p.propagate(fts,*surface);
  }else{
  ReferenceCountingPointer<BoundPlane> surface = 
    tipSurface(fts.position(),fts.momentum(),
           1./fts.transverseCurvature(),vtx);
  //
  // propagate
  //
  return p.propagate(fts,*surface);
  }
}

TrajectoryStateOnSurface TransverseImpactPointExtrapolator::extrapolate	(	const FreeTrajectoryState &	fts,
		const GlobalPoint &	vtx
	)		const

extrapolation with default (=geometrical) propagator

Definition at line 29 of file TransverseImpactPointExtrapolator.cc.

References doExtrapolation(), and thePropagator.

Referenced by GroupedCkfTrajectoryBuilder::advanceOneLayer(), reco::TransientTrackFromFTS::calculateTSOSAtVertex(), reco::TrackTransientTrack::calculateTSOSAtVertex(), reco::GsfTransientTrack::calculateTSOSAtVertex(), MuonCkfTrajectoryBuilder::collectMeasurement(), MultiRefittedTS::computeFreeTrajectoryState(), GsfConstraintAtVertex::constrainAtPoint(), SimpleNavigableLayer::crossingState(), MultiTrajectoryStateTransform::extrapolatedState(), GsfTrackProducerBase::fillMode(), CkfTrajectoryBuilder::findCompatibleMeasurements(), KFBasedPixelFitter::run(), reco::TransientTrackFromFTS::stateOnSurface(), reco::TrackTransientTrack::stateOnSurface(), reco::GsfTransientTrack::stateOnSurface(), and IPTools::transverseExtrapolate().

{
  return doExtrapolation(fts, vtx, *thePropagator);
}

TrajectoryStateOnSurface TransverseImpactPointExtrapolator::extrapolate	(	const TrajectoryStateOnSurface	tsos,
		const GlobalPoint &	vtx
	)		const

as above, but from TrajectoryStateOnSurface

Definition at line 36 of file TransverseImpactPointExtrapolator.cc.

References doExtrapolation(), TrajectoryStateOnSurface::isValid(), and thePropagator.

{
  if ( !tsos.isValid() )  return tsos;
  return doExtrapolation(tsos, vtx, *thePropagator);
}

TrajectoryStateOnSurface TransverseImpactPointExtrapolator::extrapolate	(	const FreeTrajectoryState &	fts,
		const GlobalPoint &	vtx,
		const Propagator &	u
	)		const

extrapolation with user-supplied propagator

Definition at line 44 of file TransverseImpactPointExtrapolator.cc.

References anyDirection, and doExtrapolation().

{
  //
  // set propagator for bidirectional propagation
  //
  SetPropagationDirection setter(p,anyDirection);
  return doExtrapolation(fts,vtx,p);
} 

TrajectoryStateOnSurface TransverseImpactPointExtrapolator::extrapolate	(	const TrajectoryStateOnSurface	tsos,
		const GlobalPoint &	vtx,
		const Propagator &	u
	)		const

as above, but from TrajectoryStateOnSurface

Definition at line 56 of file TransverseImpactPointExtrapolator.cc.

References anyDirection, doExtrapolation(), and TrajectoryStateOnSurface::isValid().

{
  if ( !tsos.isValid() )  return tsos;
  //
  // set propagator for bidirectional propagation
  //
  SetPropagationDirection setter(p,anyDirection);
  return doExtrapolation(tsos,vtx,p);
} 

ReferenceCountingPointer< BoundPlane > TransverseImpactPointExtrapolator::tipSurface ( const GlobalPoint &  position, const GlobalVector &  momentum, const double &  signedTransverseRadius, const GlobalPoint &  vtx  ) const

private

computation of the TIP surface

Definition at line 139 of file TransverseImpactPointExtrapolator.cc.

References Vector3DBase< T, FrameTag >::cross(), LogDebug, PV2DBase< T, PVType, FrameType >::mag(), PlaneBuilder::plane(), idealTransformation::rotation, PV3DBase< T, PVType, FrameType >::x(), and PV3DBase< T, PVType, FrameType >::y().

Referenced by doExtrapolation().

{

  LogDebug("TransverseImpactPointExtrapolator")<< position<<"\n"
                            <<momentum<<"\n"
                            <<"signedTransverseRadius : "<<signedTransverseRadius<<"\n"
                            <<vertex;

  typedef Point2DBase<double,GlobalTag> PositionType2D;
  typedef Vector2DBase<double,GlobalTag> DirectionType2D;
  
  PositionType2D x0(position.x(),position.y());
  DirectionType2D t0(-momentum.y(),momentum.x());
  t0 = t0/t0.mag();

  PositionType2D xc(x0+signedTransverseRadius*t0);

  DirectionType2D vtxDirection(xc.x()-vertex.x(),xc.y()-vertex.y());
  double vtxDistance = vtxDirection.mag();

  Surface::PositionType origin(vertex);
  GlobalVector xLocal(vtxDirection.x()/vtxDistance,
              vtxDirection.y()/vtxDistance,
              0.);
  if ( vtxDistance<fabs(signedTransverseRadius) ) {
    LogDebug("TransverseImpactPointExtrapolator")<<"Inverting the x axis.";
    xLocal = -xLocal;
  }
  GlobalVector yLocal(0.,0.,1.);
  GlobalVector zLocal(xLocal.cross(yLocal));
  if ( zLocal.dot(momentum)<0. ) {
    LogDebug("TransverseImpactPointExtrapolator")<<"Inverting the y,z frame.";
    yLocal = -yLocal;
    zLocal = -zLocal;
  }
  Surface::RotationType rotation(xLocal,yLocal,zLocal);
  
  LogDebug("TransverseImpactPointExtrapolator")<<"plane center: "<<origin<<"\n"
                           <<"plane rotation axis:\n"
                           <<xLocal<<"\n"
                           <<yLocal<<"\n"
                           <<zLocal<<"\n"
                           <<"x0: "<<x0<<"\n"
                           <<"t0: "<<t0<<"\n"
                           <<"xc: "<<xc<<"\n"
                           <<"vtxDirection: "<<vtxDirection;

  return PlaneBuilder().plane(origin,rotation);
}

Member Data Documentation

DeepCopyPointerByClone<Propagator> TransverseImpactPointExtrapolator::thePropagator

private

Definition at line 70 of file TransverseImpactPointExtrapolator.h.

Referenced by extrapolate(), and TransverseImpactPointExtrapolator().