xAODTruthHelpers.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
// Core EDM include(s):
#include "AthLinks/ElementLink.h"
#include "AthContainers/AuxElement.h"
 
// xAOD include(s):
#include "xAODBase/IParticle.h"
 
// Local include(s):
#include "xAODTruth/xAODTruthHelpers.h"
#include "xAODTruth/TruthParticle.h"
#include "xAODTruth/TruthParticleContainer.h"
 
namespace xAOD {
 
   namespace TruthHelpers {

      const xAOD::TruthParticle* getTruthParticle( const xAOD::IParticle& p ) {

         using Link_t = ElementLink<xAOD::TruthParticleContainer>;

         static const SG::AuxElement::ConstAccessor< Link_t > acc( "truthParticleLink" );
 
         // Check if such a link exists on the object:
         if( acc.isAvailable( p ) ) {
            // Get the link:
            const Link_t& link = acc( p );
 
            // Check if the link is valid:
            if( link.isValid() ) {
               // Everything has passed, let's return the pointer:
               return *link;
            }
         }

         static const SG::AuxElement::ConstAccessor< Link_t > acc_alt( "TruthLink" );
 
         // Check if such a link exists on the object:
         if( acc_alt.isAvailable( p ) ) {
            // Get the link:
            const Link_t& link_alt = acc_alt( p );
 
            // Check if the link is valid:
            if( link_alt.isValid() ) {
               // Everything has passed, let's return the pointer:
               return *link_alt;
            }
         }
 
         // Everything has failed, nothing to return
         return nullptr;
      }
 

      const xAOD::TruthParticle* getFinalCopy( const xAOD::TruthParticle& particle ) {
 
         // Loop over the children
         for( size_t i{}; i < particle.nChildren(); ++i ) {
 
            // Check if particle pointer exists and it is the same particle (same PDG ID)
            if( particle.child( i ) != nullptr && particle.child( i )->pdgId() == particle.pdgId() ) {
               // Recursively check again
               // It is fine to return when we find first copy candidate as there can only be one
               return getFinalCopy( *particle.child( i ) );
            }
         }
 
         // Return the same particle if no copies found
         return &particle;
      }
 

      int getParticleTruthType( const xAOD::IParticle& p ) {

         static const SG::AuxElement::ConstAccessor< int > acc( "truthType" );
 
         // Check if such a variable exists on the object:
         if( ! acc.isAvailable( p ) ) {
            return 0;
         }
 
         // Let's return the value:
         return acc( p );
      }

      int getParticleTruthOrigin( const xAOD::IParticle& p ) {

         static const SG::AuxElement::ConstAccessor< int > acc( "truthOrigin" );
 
         // Check if such a variable exists on the object:
         if( ! acc.isAvailable( p ) ) {
            return 0;
         }
 
         // Let's return the value:
         return acc( p );
      }

      int getParticleTruthClassification( const xAOD::IParticle& p ) {

         static const SG::AuxElement::ConstAccessor< unsigned int > acc( "truthClassification" );
         static const SG::AuxElement::ConstAccessor< unsigned int > accLegacy( "Classification" );
 
         // Check if such a variable exists on the object:
         if( ! acc.isAvailable( p ) ) {
           if( ! accLegacy.isAvailable( p ) ) {
             return 0;
           }
 
           // Let's return the value:
           return accLegacy( p );
         }
 
         // Let's return the value:
         return acc( p );
      }
 
   } // namespace TruthHelpers
 
} // namespace xAOD