MCTrueSeedFinder.cxx

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/*
  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
*/
 
/*********************************************************************
          MCTrueSeedFinder.cxx - Description in header file
*********************************************************************/
 
#include <utility>
 
#include "TrkVertexSeedFinderTools/MCTrueSeedFinder.h"
#include "TrkTrack/Track.h"
#include "TrkEventPrimitives/ParamDefs.h"
#include "TrkParameters/TrackParameters.h"
#include "GeoPrimitives/GeoPrimitives.h"
 
#include "AtlasHepMC/GenEvent.h"
#include "AtlasHepMC/GenParticle.h"
#include "AtlasHepMC/GenVertex.h"
#include "TruthUtils/MagicNumbers.h"
#include "TruthUtils/HepMCHelpers.h"
#include "GeneratorObjects/HepMcParticleLink.h"
 
namespace {
    class Interactions_pair {
    public:
      float first; 
      Amg::Vector3D second; 
      Interactions_pair(float p1, Amg::Vector3D p2)
    : first(p1), second(std::move(p2)) {};
      bool operator> (const Interactions_pair& other) const
      {return first < other.first;}
      bool operator< (const Interactions_pair& other) const
      {return first > other.first;}
    };
}
 
namespace Trk
{
 
  MCTrueSeedFinder::MCTrueSeedFinder(const std::string& t, const std::string& n, const IInterface*  p) : 
    base_class(t,n,p),
    m_removeInTimePileUp(false),
    m_removeHardScattering(false)
  {   
    declareProperty("RemoveHardScattering", m_removeHardScattering, "Do not consider hard-scattering");
    declareProperty("RemoveInTimePileUp", m_removeInTimePileUp, "Do not consider in-time pile-up");
  }
  
  
  MCTrueSeedFinder::~MCTrueSeedFinder()
  = default;
 
 
  StatusCode MCTrueSeedFinder::initialize() 
  { 
    ATH_CHECK( m_mcEventCollectionKey.initialize() );
    return StatusCode::SUCCESS;
  }
 
 
  Amg::Vector3D
  MCTrueSeedFinder::findSeed(const std::vector<const Trk::Track*>& perigeeList,
                             const xAOD::Vertex* constraint) const
  {
    std::vector<Amg::Vector3D> seeds = findMultiSeeds (perigeeList, constraint);
    if (seeds.empty()) {
      return Amg::Vector3D(0.,0.,0.);
    }
    return seeds[0];
  }
  
 
  Amg::Vector3D
  MCTrueSeedFinder::findSeed(const std::vector<const Trk::TrackParameters*>& vectorTrk,
                             const xAOD::Vertex* constraint) const
  {
    std::vector<Amg::Vector3D> seeds = findMultiSeeds (vectorTrk, constraint);
    if (seeds.empty()) {
      return Amg::Vector3D(0.,0.,0.);
    }
    return seeds[0];
  }
 
 
  std::vector<Amg::Vector3D> MCTrueSeedFinder::findMultiSeeds(const std::vector<const Trk::TrackParameters*>& /* perigeeList */,const xAOD::Vertex * /* constraint */) const
  {
    std::vector<Amg::Vector3D> seeds;
    if( retrieveInteractionsInfo (seeds).isFailure() ) {
      seeds.clear();
    }
 
    return seeds;
  }
 
 
  std::vector<Amg::Vector3D> MCTrueSeedFinder::findMultiSeeds(const std::vector<const Trk::Track*>& /* vectorTrk */,const xAOD::Vertex * /* constraint */) const
  {
    std::vector<Amg::Vector3D> seeds;
    if( retrieveInteractionsInfo (seeds).isFailure() ) {
      seeds.clear();
    }
 
    return seeds;
  }
 
  StatusCode
  MCTrueSeedFinder::retrieveInteractionsInfo (std::vector<Amg::Vector3D>& interactions) const
  {
    ATH_MSG_DEBUG("Retrieving interactions information");
    msg(MSG::DEBUG) << "StoreGate Step: MCTrueSeedFinder retrieves -- " << m_mcEventCollectionKey.key() << endmsg;
    SG::ReadHandle<McEventCollection> mcEventCollection( m_mcEventCollectionKey );
    if ( !mcEventCollection.isValid() ) {
      msg(MSG::DEBUG)
    << "Could not retrieve McEventCollection/" << m_mcEventCollectionKey.key() << " from StoreGate."  << endmsg;
      return StatusCode::FAILURE;
    }
 
    interactions.clear();    
    std::vector<Interactions_pair> interactionsColl;
    McEventCollection::const_iterator itr = mcEventCollection->begin();
    for ( ; itr != mcEventCollection->end(); ++itr ) {
      const HepMC::GenEvent* myEvent=(*itr);
      if(!pass( myEvent, mcEventCollection.cptr())) continue; //checked if events is acceptable
      
      
      //get "intensity" (scalar sum ot p_T^2)
      double sum_pt2(0.0);
      for (const auto& part: *myEvent) {
    if(!pass(part, mcEventCollection.cptr())) continue; //select stable charged particles
    sum_pt2 += part->momentum().perp2();
      }
      ATH_MSG_DEBUG("Calculated Sum P_T^2 = " << sum_pt2);
      
      //get position of interaction from first non-zero vertex
      Amg::Vector3D vtxPosition;
      auto Vert = myEvent->vertices().begin();
      msg(MSG::DEBUG) << "Retrieved position  x: " << (*Vert)->position().x()  << 
    " y: " << (*Vert)->position().y() << 
    " z: " << (*Vert)->position().z() << endmsg;
      vtxPosition = Amg::Vector3D((*Vert)->position().x(),
                  (*Vert)->position().y(),
                  (*Vert)->position().z());
      
      //now store info about position and "intensity" (here: scalar sum of p_T^2)
      interactionsColl.emplace_back(sum_pt2, vtxPosition );
    } // end loop over GenEvent
 
    //now sort the container and store results to interactions
    std::sort(interactionsColl.begin(), interactionsColl.end());
    std::vector<Interactions_pair>::iterator itIp = interactionsColl.begin();
    ATH_MSG_DEBUG("Sorted collection:");
    for (; itIp < interactionsColl.end(); ++itIp) {
      interactions.push_back(itIp->second);
      ATH_MSG_DEBUG("(" << itIp->second.x() << ", " << itIp->second.y() << ", " 
            << itIp->second.z() << "), SumPt2 = " << itIp->first);
    }
 
    ATH_MSG_DEBUG("New interactions info stored successfully: " << interactions.size() << " interactions found.");
    return StatusCode::SUCCESS;
 
  }
 
  bool MCTrueSeedFinder::pass( const HepMC::GenEvent* evt,
                   const McEventCollection* coll ) const {
 
    //we select in-time pile-up interactions and hard-scattering, if valid
 
 
    bool isEmpty = ( evt->particles_size() == 0 );
    bool isDummy = ( ( evt->event_number() == -1 ) &&
             ( HepMC::signal_process_id(evt) == 0 ) );
    if( isDummy ) isEmpty = false;
 
    if( isEmpty ) return false;
    if( isDummy ) return false;
 
    // We can't do the further selection without the full truth record:
    if( ! coll ) return true;
 
    McEventCollection::const_iterator iter = coll->begin();
    McEventCollection::const_iterator end = coll->end();
 
    if( *iter == evt ) {
      //this is the hard-scattering event (first of the collection)
      return ! m_removeHardScattering;
    }
 
    int gotzero = 1;
    for( ; iter != end; ++iter ) {
      if( ( ( ( *iter )->event_number() == -1 ) &&
            ( HepMC::signal_process_id( *iter ) == 0 ) ) ) {
    ++gotzero;
      }
      if( evt == *iter ) break;
    }
 
    if( gotzero == 1 && m_removeInTimePileUp ) return false;
    if( gotzero == 2 ) return false; //remove2BCPileUp
    if( gotzero == 3 ) return false; //remove800nsPileUp
    if( gotzero == 4 ) return false; //removeCavernBkg
 
    return true;
  }
 
  bool MCTrueSeedFinder::pass( const HepMC::ConstGenParticlePtr& part,
                   const McEventCollection* coll ) const {
 
    // Check if the particle is coming from a "good" GenEvent:
    if( ! pass( part->parent_event(), coll ) ) return false;
 
    // Now check for stable particles
    if (!HepMC::is_simulation_particle(part)) {
      if( ! MC::isGenStable( part ) ) return false;
      if( ! MC::isSimInteracting( part ) ) return false;
    }
 
    // finally require it to be charged
    int pdg = part->pdg_id();

    if( std::abs(pdg) < 7 || std::abs(pdg) == 21 ) return false;
 
    float charge = MC::charge(pdg);
 
    return std::abs( charge ) >= 1E-5;
  }
 
 
}