TruthMuonMakerAlg.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TruthMuonMakerAlg.h"
#include "MuonTruthAlgs/DecorUtils.h"
#include "StoreGate/WriteDecorHandle.h"
#include "xAODTruth/TruthParticleAuxContainer.h"
#include "xAODTruth/TruthParticleContainer.h"
#include "TruthUtils/HepMCHelpers.h"
 
namespace {
    using TruthLink_t = ElementLink<xAOD::TruthParticleContainer>;
}
namespace Muon {
 
    // Initialize method:
    StatusCode TruthMuonMakerAlg::initialize() {
        ATH_CHECK(m_truthRecordKey.initialize());
        ATH_CHECK(m_outTruthMuonKey.initialize());
        ATH_CHECK(m_truthOriginKey.initialize());
        ATH_CHECK(m_truthTypeKey.initialize());
        ATH_CHECK(m_truthLinkKey.initialize());
        ATH_CHECK(m_idHelperSvc.retrieve());
        ATH_CHECK(m_truthClassifier.retrieve());
        return StatusCode::SUCCESS;
    }
 
    // Execute method:
    StatusCode TruthMuonMakerAlg::execute(const EventContext& ctx) const {
        // skip if no input data found
        const xAOD::TruthParticleContainer* truthContainer{nullptr};
        ATH_CHECK(SG::get(truthContainer,m_truthRecordKey, ctx));
        // create output container
        SG::WriteHandle muonTruthContainer(m_outTruthMuonKey, ctx);
        ATH_CHECK(muonTruthContainer.record(std::make_unique<xAOD::TruthParticleContainer>(),
                                            std::make_unique<xAOD::TruthParticleAuxContainer>()));
        ATH_MSG_DEBUG("Recorded TruthParticleContainer with key: " << m_outTruthMuonKey);
 
        SG::WriteDecorHandle<xAOD::TruthParticleContainer, int> truthOrigin{m_truthOriginKey, ctx};
        SG::WriteDecorHandle<xAOD::TruthParticleContainer, int> truthType{m_truthTypeKey, ctx};
        SG::WriteDecorHandle<xAOD::TruthParticleContainer, TruthLink_t> truthLink{m_truthLinkKey, ctx};
 
        // loop over truth coll
        for (const xAOD::TruthParticle* truth : *truthContainer) {
            if (!MC::isStable(truth)     || !m_pdgIds.value().count(truth->absPdgId()) || truth->pt() < m_pt) continue;
            xAOD::TruthParticle* truthParticle = muonTruthContainer->push_back(std::make_unique<xAOD::TruthParticle>());
            truthParticle->setPdgId(truth->pdgId());
            truthParticle->setUid(HepMC::uniqueID(truth));
            truthParticle->setStatus(truth->status());
            truthParticle->setPx(truth->px());
            truthParticle->setPy(truth->py());
            truthParticle->setPz(truth->pz());
            truthParticle->setE(truth->e());
            truthParticle->setM(truth->m());
            if (truth->hasProdVtx()) truthParticle->setProdVtxLink(truth->prodVtxLink());
            
            TruthLink_t itruthLink(*truthContainer, truth->index());
            itruthLink.toPersistent();
            truthLink(*truthParticle) = itruthLink;
            ATH_MSG_DEBUG("Found stable muon: " << truth->pt() << " eta " << truth->eta() << " phi " << truth->phi() << " mass "
                          << truth->m() << " unique ID " << HepMC::uniqueID(truth) << " HepMC::uniqueID(truthParticle) "
                          << HepMC::uniqueID(truthParticle) << " HepMC::uniqueID(*itruthLink) " << HepMC::uniqueID(*itruthLink) << " "
                          << itruthLink);
            int iType{0}, iOrigin{0};
 
            // if configured look up truth classification
            if (!m_truthClassifier.empty()) {
                // if configured also get truth classification
                std::pair<MCTruthPartClassifier::ParticleType, MCTruthPartClassifier::ParticleOrigin> truthClass =
                    m_truthClassifier->particleTruthClassifier(truth);
                iType = truthClass.first;
                iOrigin = truthClass.second;
                ATH_MSG_VERBOSE("Got truth type  " << iType << "  origin " << iOrigin);
            }
            truthOrigin(*truthParticle) = iOrigin;
            truthType(*truthParticle) = iType;
 
            ATH_MSG_DEBUG("good muon with type " << iType << " and origin" << iOrigin);
        }
 
        ATH_MSG_DEBUG("Registered " << muonTruthContainer->size() << " truth muons ");
 
        return StatusCode::SUCCESS;
    }
 
}  // namespace Muon