TrackToVertexIPEstimator.cxx

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/*
  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TrkVertexFitterUtils/TrackToVertexIPEstimator.h"
#include "TrkTrack/Track.h"
#include "VxVertex/VxTrackAtVertex.h"
#include "TrkParticleBase/TrackParticleBase.h"
#include "TrkParameters/TrackParameters.h"
#include "TrkTrackLink/ITrackLink.h"
 
#include "xAODTracking/TrackParticle.h"
#include "xAODTracking/TrackParticleContainer.h"
#include "xAODTracking/Vertex.h"
 
namespace Trk
{
 
 TrackToVertexIPEstimator::TrackToVertexIPEstimator(const std::string& t, const std::string& n, const IInterface*  p):
  base_class(t,n,p)
 {
 }
 
 TrackToVertexIPEstimator::~TrackToVertexIPEstimator()= default;
 
 StatusCode TrackToVertexIPEstimator::initialize()
 {
 
  // uploading the corresponding tools
  // extrapolator
  if ( m_extrapolator.empty() ) {
      ATH_MSG_DEBUG("Extrapolator is None/Empty. Tool-dependent features will be disabled.");
  } else {
      // Only try to retrieve if a name was actually provided
      if ( m_extrapolator.retrieve().isFailure() ) {
          ATH_MSG_FATAL("Failed to retrieve tool " << m_extrapolator);
          return StatusCode::FAILURE;
      }
  }
  // updator
  if (m_Updator.retrieve().isFailure()) {
    ATH_MSG_FATAL("Failed to retrieve tool " << m_Updator);
    return StatusCode::FAILURE;
  }
 
  // linearized track factory
  if ( m_linFactory.retrieve().isFailure() )
  {
    ATH_MSG_FATAL("Failed to retrieve tool " << m_linFactory );
    return StatusCode::FAILURE;
  }
 
  return StatusCode::SUCCESS;
 }//end of initialize method
 
 
 std::unique_ptr<ImpactParametersAndSigma> TrackToVertexIPEstimator::estimate(const EventContext &ctx, const xAOD::TrackParticle * track, const xAOD::Vertex * vtx, bool doRemoval) const
 {
  if(track && vtx)
  {
   return estimate(ctx, &(track->perigeeParameters()),&(track->perigeeParameters()),vtx,doRemoval);
  }
  ATH_MSG_INFO( "Empty TrackParticle or Vertex pointer passed. Returning zero " );
  return nullptr;
  //end of track particle validity check
 }//end of method using track particles
 
 std::unique_ptr<ImpactParametersAndSigma> TrackToVertexIPEstimator::estimate(const EventContext &ctx, const xAOD::TrackParticle * track, const xAOD::TrackParticle * newtrack, const xAOD::Vertex * vtx, bool doRemoval) const
 {
  if(track && vtx)
  {
    return estimate(ctx, &(track->perigeeParameters()),&(newtrack->perigeeParameters()),vtx,doRemoval);
  }
   ATH_MSG_INFO( "Empty TrackParticle or Vertex pointer passed. Returning zero " );
   return nullptr;
  //end of track particle validity check
 }//end of method using track particles
 
 
 
 
 std::unique_ptr<ImpactParametersAndSigma> TrackToVertexIPEstimator::estimate(
        const EventContext &ctx,
        const TrackParameters * track, const xAOD::Vertex * vtx, bool doRemoval) const
 {
   if(track && vtx){
     return estimate(ctx, track,track,vtx,doRemoval);
   }
   ATH_MSG_INFO( "Empty TrackParticle or Vertex pointer passed. Returning zero " );
   return nullptr;
   //end of track particle validity check
 
 }//end of parameterBase estimate method
 
 std::unique_ptr<ImpactParametersAndSigma> TrackToVertexIPEstimator::estimate(
             const EventContext &ctx,
             const TrackParameters * track, const TrackParameters * newtrack, const xAOD::Vertex * vtx, bool doRemoval) const
 {
 
   if (vtx==nullptr)
   {
     ATH_MSG_WARNING("Vertex is zero pointer. Will not estimate IP of track.");
     return nullptr;
   }
 
   const xAOD::Vertex *newVertex = vtx;
   if (doRemoval)
   {
     newVertex = getUnbiasedVertex(track,vtx);
     if (newVertex == nullptr) {
       ATH_MSG_WARNING("Unbiasing of vertex failed. Will not estimate IP of track.");
       return nullptr;
     }
   }
 
   std::unique_ptr<ImpactParametersAndSigma>  IPandSigma=calculate(ctx, newtrack,*newVertex);
 
   if (doRemoval)
   {
     delete newVertex;
     newVertex=nullptr;
   }
 
   return IPandSigma;
 
 }//end of parameterBase estimate method
 
 
 std::unique_ptr<ImpactParametersAndSigma> TrackToVertexIPEstimator::calculate(const EventContext &ctx, const TrackParameters * track, const xAOD::Vertex& vtx) const
 {
  //estimating the d0 and its significance by propagating the trajectory state towards
  //the vertex position. By this time the vertex should NOT contain this trajectory anymore
 
  //estrapolating to the  perigee of the reconstructed vertex
  const Amg::Vector3D & lp = vtx.position();
  PerigeeSurface perigeeSurface(lp);
  const Trk::Perigee* extrapolatedParameters =
    dynamic_cast<const Trk::Perigee*>(
      m_extrapolator
        ->extrapolate(ctx, *track, perigeeSurface)
        .release());
  if (extrapolatedParameters && extrapolatedParameters->covariance()) {
 
    //actual calculation of d0 and sigma.
    const AmgVector(5) & par = extrapolatedParameters->parameters();
    const double d0  = par[Trk::d0];
    const double z0  = par[Trk::z0];
    const double phi = par[Trk::phi];
    const double theta = par[Trk::theta];
 
    AmgSymMatrix(2) vrtXYCov = vtx.covariancePosition().block<2,2>(0,0);
 
    const AmgSymMatrix(5) & perigeeCov = *(extrapolatedParameters->covariance());
    //   std::cout<<"Perigee covariance: "<<perigeeCov<<std::endl;
 
    //d0phi->cartesian Jacobian
    Amg::Vector2D d0JacXY(-sin(phi), cos(phi));
 
 
    auto newIPandSigma=std::make_unique<ImpactParametersAndSigma>();
    newIPandSigma->IPd0=d0;
    double d0_PVcontrib=d0JacXY.transpose()*(vrtXYCov*d0JacXY);
    if (d0_PVcontrib>=0)
    {
      newIPandSigma->sigmad0=sqrt(d0_PVcontrib+perigeeCov(Trk::d0,Trk::d0));
      newIPandSigma->PVsigmad0=sqrt(d0_PVcontrib);
    }
    else
    {
      msg(MSG::WARNING) << " The contribution to d0_err: " << d0_PVcontrib << " from PV is negative: critical error in PV error matrix! Removing contribution from PV ... "  << endmsg;
      newIPandSigma->sigmad0=sqrt(perigeeCov(Trk::d0,Trk::d0));
      newIPandSigma->PVsigmad0=0;
    }
 
    AmgSymMatrix(2) covPerigeeZ0Theta;
   covPerigeeZ0Theta(0,0)=perigeeCov(Trk::z0,Trk::z0);
   covPerigeeZ0Theta(0,1)=perigeeCov(Trk::z0,Trk::theta);
   covPerigeeZ0Theta(1,0)=perigeeCov(Trk::theta,Trk::z0);
   covPerigeeZ0Theta(1,1)=perigeeCov(Trk::theta,Trk::theta);
 
   double vrtZZCov = vtx.covariancePosition()(Trk::z,Trk::z);
 
   Amg::Vector2D IPz0JacZ0Theta (sin(theta), z0*cos(theta));
   if (vrtZZCov>=0)
   {
     newIPandSigma->IPz0SinTheta=z0*sin(theta);
     newIPandSigma->sigmaz0SinTheta=
         sqrt(IPz0JacZ0Theta.transpose()*(covPerigeeZ0Theta*IPz0JacZ0Theta)+sin(theta)*vrtZZCov*sin(theta));
     newIPandSigma->PVsigmaz0SinTheta=sqrt(sin(theta)*vrtZZCov*sin(theta));
     newIPandSigma->IPz0 = z0;
     newIPandSigma->sigmaz0 = std::sqrt( vrtZZCov + perigeeCov(Trk::z0,Trk::z0) );
     newIPandSigma->PVsigmaz0 = std::sqrt( vrtZZCov );
   }
   else
   {
     ATH_MSG_WARNING(" The contribution to z0_err: " << vrtZZCov << " from PV is negative: critical error in PV error matrix! Removing contribution from PV ... ");
     newIPandSigma->IPz0SinTheta=z0*sin(theta);
     double temp = (IPz0JacZ0Theta.transpose()*(covPerigeeZ0Theta*IPz0JacZ0Theta));
     newIPandSigma->sigmaz0SinTheta=sqrt(temp);
     newIPandSigma->PVsigmaz0SinTheta=0;
 
     newIPandSigma->IPz0 = z0;
     newIPandSigma->sigmaz0 = std::sqrt( perigeeCov(Trk::z0,Trk::z0) );
     newIPandSigma->PVsigmaz0 = 0;
   }
 
 
   delete extrapolatedParameters;
   return newIPandSigma;
  }
    ATH_MSG_DEBUG ("Cannot extrapolate the trajectory state. Returning null. ");
    return nullptr;
  //end of successfull extrapolation check
 }//end of actual calculation method
 
 
 
  double TrackToVertexIPEstimator::get3DLifetimeSignOfTrack(const EventContext &ctx, const TrackParameters & track,
                                                            const Amg::Vector3D & jetMomentum,
                                                            const xAOD::Vertex & primaryVertex) const
  {
    const Amg::Vector3D & lp = primaryVertex.position();
    PerigeeSurface perigeeSurface(lp);
 
    std::unique_ptr<const Trk::TrackParameters> extrapolatedParameters =
      m_extrapolator->extrapolate(
        ctx, track, perigeeSurface);
 
    if (!extrapolatedParameters) return 0.;
 
    const Amg::Vector3D & primaryPos=primaryVertex.position();
    const Amg::Vector3D & trackPos=extrapolatedParameters->position();
    const Amg::Vector3D & trackMom=extrapolatedParameters->momentum();
 
    double sign=(jetMomentum.cross(trackMom)).dot(trackMom.cross(primaryPos-trackPos));
 
    return sign>=0.?1.:-1;
  }
 
  double TrackToVertexIPEstimator::get2DLifetimeSignOfTrack(const EventContext &ctx,
                                                            const TrackParameters & track,
                                                            const Amg::Vector3D & jetMomentum,
                                                            const xAOD::Vertex & primaryVertex) const
  {
    const Amg::Vector3D & lp = primaryVertex.position();
    PerigeeSurface perigeeSurface(lp);
 
    std::unique_ptr<const Trk::TrackParameters> extrapolatedParameters =
      m_extrapolator->extrapolate(
        ctx, track, perigeeSurface);
 
    if (!extrapolatedParameters) return 0.;
 
    double trackD0  = extrapolatedParameters->parameters()[Trk::d0];
    double trackPhi = extrapolatedParameters->parameters()[Trk::phi];
    double vs = sinf( atan2(jetMomentum.y(),jetMomentum.x()) - trackPhi )*trackD0;
 
    return (vs>=0. ? 1. : -1.);
  }
 
 
  double TrackToVertexIPEstimator::getZLifetimeSignOfTrack(const EventContext &ctx,
                                                           const TrackParameters & track,
                                                           const Amg::Vector3D & jetMomentum,
                                                           const xAOD::Vertex & primaryVertex) const
  {
 
    const Amg::Vector3D & lp = primaryVertex.position();
    PerigeeSurface perigeeSurface(lp);
 
    std::unique_ptr<const Trk::TrackParameters> extrapolatedParameters =
      m_extrapolator->extrapolate(
        ctx, track, perigeeSurface);
 
    if (!extrapolatedParameters) return 0.;
 
    double trackTheta  = extrapolatedParameters->parameters()[Trk::theta];
    double trackZ0 = extrapolatedParameters->parameters()[Trk::z0];
    double trackEta = -logf(tanf(trackTheta/2.));
    double jetEta = jetMomentum.eta();
    double zs = (jetEta - trackEta)*trackZ0;
    return (zs>=0. ? 1. : -1.);
  }
 

 
xAOD::Vertex * TrackToVertexIPEstimator::getUnbiasedVertex(const xAOD::TrackParticle * track, const xAOD::Vertex * vtx ) const
 {
  if(track)
  {
   return getUnbiasedVertex(&(track->perigeeParameters()),vtx);
  }
   msg(MSG::INFO) << "Empty xAOD::TrackParticle pointer passed. Returning zero " << endmsg;
   return nullptr;
  //end of track particle validity check
 }
 
xAOD::Vertex * TrackToVertexIPEstimator::getUnbiasedVertex(const TrackParameters * track, const xAOD::Vertex * vtx ) const
 {
   if (!track) {
     msg(MSG::INFO) << "Empty Trk::TrackParameter pointer passed. Returning zero " << endmsg;
     return nullptr;
   }
   if (!vtx) {
     msg(MSG::INFO) << "Empty xAOD::Vertex pointer passed. Returning zero " << endmsg;
     return nullptr;
   }
 
   if (vtx->nTrackParticles() == 0)
    {
      ATH_MSG_DEBUG("This vertex has no associated tracks. Normal if beam spot is used. Vertex already unbiased");
      return new xAOD::Vertex(*vtx);
    }
 
   //create new vertex for output
   xAOD::Vertex *outputVertex = new xAOD::Vertex(*vtx);
   outputVertex->clearTracks(); //remove all tracks -> will add them back one by one
   if (outputVertex->vxTrackAtVertexAvailable()) outputVertex->vxTrackAtVertex().clear(); //remove all VxTrackAtVertex
 
   bool tmpLinTrack = false; //do we created a new linearised track?
 
   //loop over tracks
   const Amg::Vector3D & pos = track->position();
   const Amg::Vector3D & mom = track->momentum();
   for (unsigned int itrk=0; itrk < vtx->nTrackParticles(); ++itrk) {
     const Perigee& testTP = vtx->trackParticle(itrk)->perigeeParameters();
     if ((testTP.position() == pos) and (testTP.momentum() == mom)) {
       //track found, now unbias the vertex using linearized track
       const LinearizedTrack *linTrack = nullptr;
       double trackWeight(0.0);
       //first check if a VxTrackAtVertex is already available with linearized track
       if (vtx->vxTrackAtVertexAvailable()) {
     if (vtx->vxTrackAtVertex().size() > itrk) {
       linTrack = vtx->vxTrackAtVertex()[itrk].linState();
       trackWeight = vtx->vxTrackAtVertex()[itrk].weight();
     }
       }
       //if linearized track is not available, create it
       if (!linTrack) {
     linTrack = m_linFactory->linearizedTrack(track, vtx->position());
     trackWeight = vtx->trackWeight(itrk);
     if (!linTrack) {
       ATH_MSG_INFO("Failing to linearized track. Returning biased vertex.");
       outputVertex->addTrackAtVertex(vtx->trackParticleLinks()[itrk], vtx->trackWeight(itrk));
       if (vtx->vxTrackAtVertexAvailable()) {
         outputVertex->vxTrackAtVertex().push_back(vtx->vxTrackAtVertex()[itrk]);//will clone everything inside -> output vertex owns all the memory
       }
       continue;
     }
     tmpLinTrack = true;
       }
       //now update vertex position removing the linearized track, and do not add the track back to the output vertex
       const IVertexUpdator::positionUpdateOutcome & reducedVertex = m_Updator->positionUpdate(*vtx, linTrack, trackWeight,IVertexUpdator::removeTrack);
 
       //calculate updated chi2
       double chi2 = vtx->chiSquared();
       double trk_chi = m_Updator->trackParametersChi2( reducedVertex, linTrack );
       chi2 += -1 * (m_Updator->vertexPositionChi2(*vtx, reducedVertex) + trackWeight * trk_chi);
 
       //calculate updated ndf
       double ndf = vtx->numberDoF();
       ndf += -1 * trackWeight * (2.0);
 
       //reducedVertex has the updated position and covariance
       outputVertex->setPosition(reducedVertex.position);
       outputVertex->setCovariancePosition(reducedVertex.covariancePosition);
 
       //chi2 and ndf now store the updated FitQuality
       outputVertex->setFitQuality( chi2, ndf );
 
       if (tmpLinTrack) delete linTrack; //only delete if it was created new, and doesn't belong to a vertex
     } else {
       //track not to be removed. Add back the track to the vertex collection
       outputVertex->addTrackAtVertex(vtx->trackParticleLinks()[itrk], vtx->trackWeight(itrk));
       if (vtx->vxTrackAtVertexAvailable()) {
     outputVertex->vxTrackAtVertex().push_back(vtx->vxTrackAtVertex()[itrk]);//will clone everything inside -> output vertex owns all the memory
       }
     }
   }
   return outputVertex;
 
 }
 
 
 
 std::unique_ptr<ImpactParametersAndSigma> TrackToVertexIPEstimator::estimate(const EventContext &ctx,
                                                                      const xAOD::TrackParticle * track,
                                                                      const xAOD::Vertex* vtx)const
 {
 
   if(track && vtx ){
     return estimate(ctx, &(track->perigeeParameters()), vtx);
   }
   return nullptr;
 
 }
 
 std::unique_ptr<ImpactParametersAndSigma> TrackToVertexIPEstimator::estimate(
                                                                      const EventContext &ctx,
                                                                      const TrackParameters * track,
                                                                      const xAOD::Vertex* vtx)const
 {
 
   if(track && vtx ){
     return calculate(ctx, track , *vtx);
   }
   return nullptr;
 
 }
 
}//end of namespace definitions