NeutralPFOClusterMLCorrectionTool.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "NeutralPFOClusterMLCorrectionTool.h"
 
NeutralPFOClusterMLCorrectionTool::NeutralPFOClusterMLCorrectionTool(const std::string &type, const std::string &name, const IInterface *parent) 
  : base_class(type, name, parent) {}
 
StatusCode NeutralPFOClusterMLCorrectionTool::initialize() {
  ATH_MSG_DEBUG("Initializing with ClusterMLCorrectedEnergyDecorationKey: " << m_clusterMLCorrectedEnergyKey.value());
  ATH_MSG_DEBUG("Initializing with MaxAllowedChargedCorrectionFraction: " << m_max_allowed_charged_correction_fraction.value());
  ATH_MSG_DEBUG("Initializing with MinAllowedEMEnergyMeV: " << m_min_allowed_em_energy.value());
  return StatusCode::SUCCESS;
}
 
void NeutralPFOClusterMLCorrectionTool::correctContainer(xAOD::FlowElementContainer &neutral_pfos, xAOD::FlowElementContainer &/*charged_pfos*/) const
{
  for (xAOD::FlowElement *neutral_pfo : neutral_pfos)
  { correctNeutralFlowElement(*neutral_pfo); }
}
 
 
void NeutralPFOClusterMLCorrectionTool::correctNeutralFlowElement(xAOD::FlowElement &neutral_pfo) const
{
  // The correction is applied only if link to cluster exists.
  // If no link exists, it can be due to negative cell subtraction. In this case, no correction is applied.
  // The corrected neutral pfo energy is calculated from ML-corrected cluster energy
  if (neutral_pfo.isCharged())
  {
    throw std::runtime_error("Charged FlowElement found in neutral FlowElementContainer with index " + std::to_string(neutral_pfo.index()));
  }
  const xAOD::CaloCluster *cls = getLinkedCluster(neutral_pfo);
  if (cls == nullptr)
  { return; }
 
  const double cluster_EM_energy = cls->rawE();
 
  bool apply_ML_correction = (std::abs(neutral_pfo.e() - cluster_EM_energy) <= std::abs(m_max_allowed_charged_correction_fraction.value() * cluster_EM_energy));
  apply_ML_correction = (cluster_EM_energy > m_min_allowed_em_energy.value());
  if (apply_ML_correction)
  {
    const double cluster_ML_energy = getClusterMLCorrectedEnergy(*cls);
    neutral_pfo.setP4(cluster_ML_energy / cosh(neutral_pfo.eta()), neutral_pfo.eta(), neutral_pfo.phi(), neutral_pfo.m());
  }
 
}
 
 
const xAOD::CaloCluster *NeutralPFOClusterMLCorrectionTool::getLinkedCluster(const xAOD::FlowElement &neutral_pfo) const
{
  // Returns xAOD::Type::CaloCluster type link. There should be at most one such link.
  // It can happen that no such link exists. This can happen due to negative cells subtraction.
  // Empty link is returned if no valid cluster link is found.
  const std::vector<ElementLink<xAOD::IParticleContainer>> &otherObjectLinks = neutral_pfo.otherObjectLinks();
  if (otherObjectLinks.size() > 1)
    throw std::runtime_error("NeutralPFOClusterMLCorrectionTool: Multiple links found for neutral FlowElement with index " + std::to_string(neutral_pfo.index()));
 
  bool hasValidLink = !otherObjectLinks.empty() && otherObjectLinks[0].isValid();
  if (!hasValidLink)
  { return nullptr; }
 
  if ((**otherObjectLinks[0]).type() != xAOD::Type::CaloCluster)
    throw std::runtime_error("NeutralPFOClusterMLCorrectionTool: Link for neutral FlowElement with index " + std::to_string(neutral_pfo.index()) + " is not of type CaloCluster");
 
  return static_cast<const xAOD::CaloCluster *>(*otherObjectLinks[0]);
}
 
double NeutralPFOClusterMLCorrectionTool::getClusterMLCorrectedEnergy(const xAOD::CaloCluster &cls) const
{
  const SG::Accessor<double> clusterMLCorrectedEnergyAccessor(m_clusterMLCorrectedEnergyKey.value());
  if (!clusterMLCorrectedEnergyAccessor.isAvailable(cls))
  {
    throw std::runtime_error("No ML energy decoration '" + m_clusterMLCorrectedEnergyKey.value()
              + "' found for cluster with index " + std::to_string(cls.index())
              + ". Returning EM energy.");
  }
  return clusterMLCorrectedEnergyAccessor(cls);
}