TrackLeptonDecoratorAlg.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
 
#include "FlavorTagDiscriminants/TrackLeptonDecoratorAlg.h"
 
#include "StoreGate/WriteDecorHandle.h"
#include "StoreGate/ReadDecorHandle.h"
 
#include "xAODTracking/TrackParticleContainer.h"
 
#include "xAODEgamma/ElectronxAODHelpers.h"
#include "ElectronPhotonSelectorTools/ElectronSelectorHelpers.h"
 
 
namespace FlavorTagDiscriminants {
 
  TrackLeptonDecoratorAlg::TrackLeptonDecoratorAlg(
    const std::string& name, ISvcLocator* loc )
    : AthReentrantAlgorithm(name, loc) {}
 
  StatusCode TrackLeptonDecoratorAlg::initialize() {
    ATH_MSG_INFO( "Inizializing " << name() << "... " );
 
    // Initialize Container keys
    ATH_MSG_DEBUG( "Inizializing containers:"            );
    ATH_MSG_DEBUG( "    ** " << m_TrackContainerKey      );
    ATH_MSG_DEBUG( "    ** " << m_ElectronContainerKey   );
    ATH_MSG_DEBUG( "    ** " << m_MuonContainerKey       );
 
    ATH_CHECK( m_TrackContainerKey.initialize() );
    ATH_CHECK( m_ElectronContainerKey.initialize() );
    ATH_CHECK( m_MuonContainerKey.initialize() );
 
    // Initialise electron ID tool
    ATH_CHECK(m_electronID_tool.retrieve());
 
    // Initialise muon ID tool
    ATH_CHECK(m_muonID_tool.retrieve());
 
    // Initialize decorators
    ATH_MSG_DEBUG( "Inizializing decorators:"  );
    ATH_MSG_DEBUG( "    ** " << m_dec_lepton_id );
    ATH_MSG_DEBUG( "    ** " << m_dec_muon_quality );
    ATH_MSG_DEBUG( "    ** " << m_dec_muon_qOverPratio );
    ATH_MSG_DEBUG( "    ** " << m_dec_muon_momentumBalanceSignificance );
    ATH_MSG_DEBUG( "    ** " << m_dec_muon_scatteringNeighbourSignificance );
 
    ATH_CHECK( m_dec_lepton_id.initialize() );
    ATH_CHECK( m_dec_muon_quality.initialize() );
    ATH_CHECK( m_dec_muon_qOverPratio.initialize() );
    ATH_CHECK( m_dec_muon_momentumBalanceSignificance.initialize() );
    ATH_CHECK( m_dec_muon_scatteringNeighbourSignificance.initialize() );
 
    return StatusCode::SUCCESS;
  }
 
  StatusCode TrackLeptonDecoratorAlg::execute(const EventContext& ctx) const {
    ATH_MSG_DEBUG( "Executing " << name() << "... " );
 
    // read collections
    SG::ReadHandle<xAOD::TrackParticleContainer> tracks(
      m_TrackContainerKey,ctx);
    CHECK( tracks.isValid() );
    ATH_MSG_DEBUG( "Retrieved " << tracks->size() << " tracks..." );
    SG::ReadHandle<xAOD::ElectronContainer> electrons(
      m_ElectronContainerKey,ctx);
    CHECK( tracks.isValid() );
    ATH_MSG_DEBUG( "Retrieved " << electrons->size() << " electrons..." );
    SG::ReadHandle<xAOD::MuonContainer> muons(
      m_MuonContainerKey,ctx);
    CHECK( tracks.isValid() );
    ATH_MSG_DEBUG( "Retrieved " << muons->size() << " muons..." );
 
    using TPC = xAOD::TrackParticleContainer;
    SG::WriteDecorHandle<TPC, char> decor_lepton_id(m_dec_lepton_id, ctx);
    SG::WriteDecorHandle<TPC, char> decor_muon_quality(m_dec_muon_quality, ctx);
    SG::WriteDecorHandle<TPC, float> decor_muon_qOverPratio(m_dec_muon_qOverPratio, ctx);
    SG::WriteDecorHandle<TPC, float> decor_muon_momentumBalanceSignificance(m_dec_muon_momentumBalanceSignificance, ctx);
    SG::WriteDecorHandle<TPC, float> decor_muon_scatteringNeighbourSignificance(m_dec_muon_scatteringNeighbourSignificance, ctx);
 
    // give all tracks a default starting value
    for ( const xAOD::TrackParticle* track : *tracks ) {
      decor_lepton_id(*track) = 0;
      decor_muon_quality(*track) = -1;
      decor_muon_qOverPratio(*track) = -99.;
      decor_muon_momentumBalanceSignificance(*track) = -99.;
      decor_muon_scatteringNeighbourSignificance(*track) = -99.;
    }
 
    // loop over electrons
    for ( const auto electron : *electrons ) {
 
      // get associated InDet track (not the GSF track which is likely to have improved parameters,
      // more info: https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/EGammaD3PDtoxAOD#TrackParticle)
      const xAOD::TrackParticle* track = xAOD::EgammaHelpers::getOriginalTrackParticle(electron);
      if ( !track ) { continue; }
 
      // apply electron ID requirement
      bool LH_selection = bool{m_electronID_tool->accept(electron)};
      if (!LH_selection) { continue; }
 
      // decorate the track
      decor_lepton_id(*track) = -11 * electron->charge();
    }
 
    // loop over muons - do it last in case we have a track that was used in the 
    // reconstruction of an electron and a muon (which can happen in rare cases)
    for ( const auto muon : *muons ) {
 
      if ( !m_muonID_tool->accept(*muon) ) {
        continue;
      }
      // get associated InDet track
      auto track_link = muon->inDetTrackParticleLink();
      if ( !track_link.isValid() ) { continue; }
      auto track = *track_link;
 
      // get associated muon spectrometer track
      auto ms_track_link = muon->extrapolatedMuonSpectrometerTrackParticleLink();
      if ( !ms_track_link.isValid() ) { continue; }
      auto ms_track = *ms_track_link;
 
      float momBalSig = 0.;
      float scatNeighSig = 0.;
      muon->parameter(momBalSig, xAOD::Muon::momentumBalanceSignificance);
      muon->parameter(scatNeighSig, xAOD::Muon::scatteringNeighbourSignificance);
 
      // decorate the track
      decor_lepton_id(*track) = -13 * muon->charge();
      decor_muon_quality(*track) = m_muonID_tool->getQuality(*muon);
      decor_muon_qOverPratio(*track) = track->qOverP() / ms_track->qOverP();
      decor_muon_momentumBalanceSignificance(*track) = momBalSig;
      decor_muon_scatteringNeighbourSignificance(*track) = scatNeighSig;
    }
 
    return StatusCode::SUCCESS;
  }
 
}