PhotonxAODHelpers.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "xAODEgamma/PhotonxAODHelpers.h"
#include "xAODEgamma/ElectronxAODHelpers.h"
#include "xAODEgamma/EgammaDetails.h"
#include "xAODEgamma/Photon.h"
#include "xAODTracking/Vertex.h"
 
 
#include<cmath>
 
// ==================================================================
 
bool xAOD::EgammaHelpers::isConvertedPhoton(const xAOD::Photon *ph, bool excludeTRT) {
  if (!ph) return false;
  return EgammaDetails::isConvertedPhoton(excludeTRT, ph->eta(), ph->nVertices(), conversionType(ph));
}
 
xAOD::EgammaParameters::ConversionType xAOD::EgammaHelpers::conversionType(const xAOD::Photon *ph){
  if (!ph) return xAOD::EgammaParameters::NumberOfVertexConversionTypes;
  return conversionType(ph->vertex());
}
 
xAOD::EgammaParameters::ConversionType xAOD::EgammaHelpers::conversionType(const xAOD::Vertex *vx){
  if (!vx) return xAOD::EgammaParameters::unconverted;
 
  const TrackParticle *trk1 = ( vx->nTrackParticles() ? vx->trackParticle(0) : nullptr );
  const TrackParticle *trk2 = ( vx->nTrackParticles() > 1 ? vx->trackParticle(1) : nullptr );
  uint8_t nSiHits1 = numberOfSiHits(trk1);
  uint8_t nSiHits2 = numberOfSiHits(trk2);
 
  return EgammaDetails::conversionType (trk1 != nullptr, trk2 != nullptr, nSiHits1, nSiHits2);
}
 
// ==================================================================
 
std::size_t xAOD::EgammaHelpers::numberOfSiTracks(const xAOD::Photon *ph){
  if (!ph || !ph->vertex()) {return 0;}
  return numberOfSiTracks(ph->vertex());
}
 
std::size_t xAOD::EgammaHelpers::numberOfSiTracks(const xAOD::Vertex *vx){
  if (!vx) return 0;
  return numberOfSiTracks(conversionType(vx));
}
 
std::size_t xAOD::EgammaHelpers::numberOfSiTracks(const xAOD::EgammaParameters::ConversionType convType){
  if (convType == xAOD::EgammaParameters::doubleSi) {return 2;}
  if (convType == xAOD::EgammaParameters::singleSi ||
      convType == xAOD::EgammaParameters::doubleSiTRT) {return 1;}
  return 0;
}
 
// ==================================================================
 
float xAOD::EgammaHelpers::conversionRadius(const xAOD::Vertex* vx){
  if (!vx) return 9999.;
  return sqrt( vx->x()*vx->x() + vx->y()*vx->y() );
}
 
float xAOD::EgammaHelpers::conversionRadius(const xAOD::Photon* ph){
  if (!ph || !ph->vertex()) return 9999.;
  return conversionRadius(ph->vertex());
}
 
// ==================================================================
 
Amg::Vector3D xAOD::EgammaHelpers::momentumAtVertex(const xAOD::Photon *photon, bool debug){
  if (!photon || !photon->vertex()) return Amg::Vector3D(0., 0., 0.);
  return momentumAtVertex(*photon->vertex(), debug);
}
  
 
Amg::Vector3D xAOD::EgammaHelpers::momentumAtVertex(const xAOD::Vertex& vertex, bool debug){  
 
  static const SG::AuxElement::Accessor<float> accPx("px");
  static const SG::AuxElement::Accessor<float> accPy("py");
  static const SG::AuxElement::Accessor<float> accPz("pz");
  
  if (accPx.isAvailable(vertex) && 
      accPy.isAvailable(vertex) && 
      accPz.isAvailable(vertex)) 
    {
      return Amg::Vector3D(accPx(vertex), 
               accPy(vertex),  
               accPz(vertex)); 
    }
  if (debug){
    std::cout << "Vertex not decorated with momentum" << std::endl;
  }
  return Amg::Vector3D(0., 0., 0.);
}
 
// ==================================================================
std::set<const xAOD::TrackParticle*> xAOD::EgammaHelpers::getTrackParticles(const xAOD::Photon* ph,  
                                          bool useBremAssoc /* = true */){
 
  std::set<const xAOD::TrackParticle*> tps;
  if (!ph) return tps;
  for (unsigned int ivx = 0; ivx < ph->nVertices(); ++ivx)
  {
    const xAOD::Vertex* vx = ph->vertex(ivx);
    for (unsigned int i=0; vx && i < vx->nTrackParticles(); ++i){
      const xAOD::TrackParticle *tp = vx->trackParticle(i);
      tps.insert( useBremAssoc ? xAOD::EgammaHelpers::getOriginalTrackParticleFromGSF(tp) : tp );
    }
  }
  return tps;
}
// ==================================================================
std::vector<const xAOD::TrackParticle*> xAOD::EgammaHelpers::getTrackParticlesVec(const xAOD::Photon* ph,
                                            bool useBremAssoc /* = true */){
  std::vector<const xAOD::TrackParticle*> tps;
  if (!ph) return tps;
  for (unsigned int ivx = 0; ivx < ph->nVertices(); ++ivx)
  {
    const xAOD::Vertex* vx = ph->vertex(ivx);
    for (unsigned int i=0; vx && i < vx->nTrackParticles(); ++i){
      const xAOD::TrackParticle *tp = vx->trackParticle(i);
      tps.push_back( useBremAssoc ? xAOD::EgammaHelpers::getOriginalTrackParticleFromGSF(tp) : tp );
    }
  }
  return tps;
}