DiTauTrackParticleThinning.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/

// DiTauTrackParticleThinning.cxx, (c) ATLAS Detector software
// Author: James Catmore (James.Catmore@cern.ch)
// This is a trivial example of an implementation of a thinning tool
// which removes all ID tracks which do not pass a user-defined cut
 
#include "DerivationFrameworkInDet/DiTauTrackParticleThinning.h"
#include "xAODTracking/TrackParticleContainer.h"
#include "StoreGate/ThinningHandle.h"
#include <vector>
#include <string>
 
// Constructor
DerivationFramework::DiTauTrackParticleThinning::DiTauTrackParticleThinning(const std::string& t,
                                                                            const std::string& n,
                                                                            const IInterface* p ) :
base_class(t,n,p)
{}
 
// Destructor
DerivationFramework::DiTauTrackParticleThinning::~DiTauTrackParticleThinning() = default;
 
// Athena initialize and finalize
StatusCode DerivationFramework::DiTauTrackParticleThinning::initialize()
{
    // Decide which collections need to be checked for ID TrackParticles
    ATH_MSG_VERBOSE("initialize() ...");
    ATH_CHECK( m_ditauKey.initialize () );
    ATH_CHECK( m_inDetSGKey.initialize (m_streamName) );
    ATH_MSG_INFO("Using " << m_inDetSGKey.key() << "as the source collection for inner detector track particles");
    ATH_MSG_INFO("Inner detector track particles associated with objects in " << m_ditauKey.key() << " will be retained in this format with the rest being thinned away");
 
    // Set up the text-parsing machinery for selectiong the ditau directly according to user cuts
    if (!m_selectionString.empty()) {
       ATH_CHECK(initializeParser(m_selectionString));
    }
    return StatusCode::SUCCESS;
}
 
StatusCode DerivationFramework::DiTauTrackParticleThinning::finalize()
{
    ATH_MSG_VERBOSE("finalize() ...");
    ATH_MSG_INFO("Processed "<< m_ntot <<" tracks, "<< m_npass<< " were retained ");
    ATH_CHECK( finalizeParser() );
    return StatusCode::SUCCESS;
}
 
// The thinning itself
StatusCode DerivationFramework::DiTauTrackParticleThinning::doThinning(const EventContext& ctx) const
{
 
 
    // Retrieve main TrackParticle collection
    SG::ThinningHandle<xAOD::TrackParticleContainer> importedTrackParticles
      (m_inDetSGKey, ctx);
    
    // Check the event contains tracks
    unsigned int nTracks = importedTrackParticles->size();
    if (nTracks==0) return StatusCode::SUCCESS;
    
    // Set up a mask with the same entries as the full TrackParticle collection
    std::vector<bool> mask(nTracks);
    m_ntot += nTracks;
    
    // Retrieve containers
    // ... ditaus
    SG::ReadHandle<xAOD::DiTauJetContainer> importedDiTaus(m_ditauKey,ctx);
    if (!importedDiTaus.isValid()) {
        ATH_MSG_ERROR("No ditau collection with name " << m_ditauKey.key() << " found in StoreGate!");
        return StatusCode::FAILURE;
    }
    unsigned int nDiTaus(importedDiTaus->size());
    std::vector<const xAOD::DiTauJet*> ditauToCheck; ditauToCheck.clear();
    
    // Execute the text parser if requested
    if (!m_selectionString.empty()) {
        std::vector<int> entries =  m_parser->evaluateAsVector();
        unsigned int nEntries = entries.size();
        // check the sizes are compatible
        if (nDiTaus != nEntries ) {
          ATH_MSG_ERROR("Sizes incompatible! Are you sure your selection string used ditaus??");
            return StatusCode::FAILURE;
        } else {
          // identify which ditaus to keep for the thinning check
          for (unsigned int i=0; i<nDiTaus; ++i) if (entries[i]==1) ditauToCheck.push_back((*importedDiTaus)[i]);
        }
    }
    
    // Set elements in the mask to true if there is a corresponding ElementLink from a reconstructed object
    // ... ditaus
    if (m_selectionString=="") { // check all ditaus as user didn't provide a selection string
      for (const auto *ditauIt : *importedDiTaus) {
        for (unsigned int i=0; i<ditauIt->nTracks(); ++i) {
          std::size_t index = ditauIt->trackLinks().at(i).index();
          mask.at(index) = true;
        }
        for (unsigned int i=0; i<ditauIt->nIsoTracks(); ++i) {
          std::size_t index = ditauIt->isoTrackLinks().at(i).index();
          mask.at(index) = true;
        }
      }
    } else { // check only ditaus passing user selection string
        for (auto & ditauIt : ditauToCheck) {
          for (unsigned int i=0; i<ditauIt->nTracks(); ++i) {
              std::size_t index = ditauIt->trackLinks().at(i).index();
              mask.at(index) = true;
          }
          for (unsigned int i=0; i<ditauIt->nIsoTracks(); ++i) {
              std::size_t index = ditauIt->isoTrackLinks().at(i).index();
              mask.at(index) = true;
          }
        }
    }
 
    // Count up the mask contents
    unsigned int n_pass=0;
    for (unsigned int i=0; i<nTracks; ++i) {
        if (mask[i]) ++n_pass;
    }
    m_npass += n_pass;
 
    // Execute the thinning service based on the mask. Finish.
    importedTrackParticles.keep (mask);
 
    return StatusCode::SUCCESS;
}