Z0PVTrackCompatibilityEstimator.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
 
#include "TrkVertexFitterUtils/Z0PVTrackCompatibilityEstimator.h"
 
#include "TrkTrack/Track.h"
 
#include "TrkParticleBase/TrackParticleBase.h"
 
#include "TrkParameters/TrackParameters.h"
 
#include "VxVertex/VxTrackAtVertex.h"
 
 
 
namespace Trk{
 
  Z0PVTrackCompatibilityEstimator::Z0PVTrackCompatibilityEstimator(const std::string& type, 
                                   const std::string& name,
                                   const IInterface* parent) :
    base_class(type, name, parent),
    m_ipEstimator("Trk::TrackToVertexIPEstimator"),
    m_z0SignificanceMax(30.)
  {
    declareProperty("IPEstimator", m_ipEstimator, "Impact parameter estimator tool");
    declareProperty("Z0SignificanceMax", m_z0SignificanceMax);
  }
 
  Z0PVTrackCompatibilityEstimator::~Z0PVTrackCompatibilityEstimator()= default;
 
 
  StatusCode Z0PVTrackCompatibilityEstimator::initialize(){
    
    ATH_MSG_INFO( "Initializing Z0PVTrackCompatibilityEstimator" );
 
    StatusCode sc = m_ipEstimator.retrieve();
    if( !sc.isSuccess() ){
      msg(MSG::FATAL) << "Unable to retrieve impact parameter estimator tool" << endmsg;
      return sc;
    }
 
    return StatusCode::SUCCESS; 
  }
 
 
  StatusCode Z0PVTrackCompatibilityEstimator::finalize(){
 
    ATH_MSG_INFO( "Finalizing Z0PVTrackCompatibilityEstimator" );
 
    return StatusCode::SUCCESS; 
  } 
 
 
 
  bool Z0PVTrackCompatibilityEstimator::isCompatible(const xAOD::TrackParticle* track,
                                                     const xAOD::VertexContainer* primaryVertexContainer, unsigned int index) const{
 
    return isCompatible( &(track->perigeeParameters()), primaryVertexContainer, index );
  }
 
  bool Z0PVTrackCompatibilityEstimator::isCompatible(const TrackParameters* track,
                             const xAOD::VertexContainer* primaryVertexContainer, unsigned int index) const{
    
    // TODO: do we want to doRemoval here? (I have it as false for now) 
    std::unique_ptr<ImpactParametersAndSigma> ip =  m_ipEstimator->estimate(Gaudi::Hive::currentContext(),
          track, track, (*primaryVertexContainer)[index], false);
    
    bool pileup = false;
  
    double sumptPV = 0;
    
    
    // TODO: perhaps calculate sumptPV using VxTracksAtVertex in xAOD::Vertex? -David S.
    for(unsigned int i = 0; i < (*primaryVertexContainer)[index]->nTrackParticles(); ++i){
 
      sumptPV += (*primaryVertexContainer)[index]->trackParticle(i)->perigeeParameters().momentum().perp();
    }
 
    for(unsigned int i = 0; i < primaryVertexContainer->size(); i++){
      
      double sumpt = 0.;
      
      if( i != index &&
      (*primaryVertexContainer)[i]->vertexType() != xAOD::VxType::NoVtx ){
        
 
        // TODO: perhaps calculate sumptPV using VxTracksAtVertex in xAOD::Vertex? -David S.
        for(unsigned int itrk = 0; itrk < (*primaryVertexContainer)[i]->nTrackParticles(); ++itrk){
 
          sumpt += (*primaryVertexContainer)[i]->trackParticle(itrk)->perigeeParameters().momentum().perp();
        }
        if ((sumpt + sumptPV) == 0.)[[unlikely]]{
          ATH_MSG_ERROR("isCompatible: Divisor 'sumpt + sumptPV' is zero.");
          return false;
        }
    double vxReach = 
      std::abs((*primaryVertexContainer)[i]->position().z()
           - (*primaryVertexContainer)[index]->position().z()) * sumpt / (sumpt + sumptPV);
    
    if(std::abs(ip->IPz0 + (*primaryVertexContainer)[index]->position().z() -
            (*primaryVertexContainer)[i]->position().z()) < vxReach){
      
      pileup = true;
    }
      }
    }
  
    return std::abs(ip->IPz0) / ip->sigmaz0 < m_z0SignificanceMax && !pileup;
  }
 
}