ChargedTracksFilter.cxx

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/*
  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
*/
 
#include "GeneratorFilters/ChargedTracksFilter.h"
#include "TruthUtils/HepMCHelpers.h"
 
 
ChargedTracksFilter::ChargedTracksFilter(const std::string& name, ISvcLocator* pSvcLocator)
  : GenFilter(name, pSvcLocator)
{
  declareProperty("Ptcut", m_Ptmin = 50.0);
  declareProperty("Etacut", m_EtaRange = 2.5);
  declareProperty("NTracks", m_NTracks = 40);
  declareProperty("NTracksMax", m_NTracksMax = -1);
 
}
 
 
StatusCode ChargedTracksFilter::filterEvent() {
  int nChargedTracks = 0;
 
  // Loop over all events in McEventCollection
  for (McEventCollection::const_iterator itr = events()->begin(); itr != events()->end(); ++itr) {
    const HepMC::GenEvent* genEvt = *itr;
 
  for (const auto& part: *genEvt){
      // We only care about stable particles
      if (!MC::isGenStable(part)) continue;
 
      // Particle's charge
      int pID = part->pdg_id();
      double pCharge = MC::charge(pID);
 
      // Count tracks in specified acceptance
      const double pT = part->momentum().perp();
      const double eta = part->momentum().pseudoRapidity();
      if (pT >= m_Ptmin && std::abs(eta) <= m_EtaRange && pCharge != 0) {
        ATH_MSG_DEBUG("Found particle, " <<
                      " pT = " << pT <<
                      " eta = " << eta <<
                      " pdg id = " << pID <<
                      " charge = " << pCharge << " in acceptance");
        nChargedTracks += 1;
      }
    }
  }
 
  // Summarise event
  ATH_MSG_DEBUG("# of tracks " << nChargedTracks <<
                " with pT >= " << m_Ptmin <<
                " |eta| < " << m_EtaRange <<
                " minNTracks = " << m_NTracks <<
        " maxNTracks = " << m_NTracksMax);
 
  // Record passed status  
  setFilterPassed( ((m_NTracksMax == -1) || (nChargedTracks <= m_NTracksMax)) && 
           ((m_NTracks    == -1) || (nChargedTracks >= m_NTracks   )) );
 
  return StatusCode::SUCCESS;
}