FastCaloSim.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
// Header include
#include "FastCaloSim.h"
 
// FastCaloSim includes
#include "ISF_FastCaloSimEvent/TFCSSimulationState.h"
#include "ISF_FastCaloSimEvent/TFCSTruthState.h"
#include "ISF_FastCaloSimEvent/TFCSExtrapolationState.h"
#include "MCTruth/AtlasG4EventUserInfo.h"
 
// Geant4 particle includes
#include "G4Gamma.hh"
#include "G4Electron.hh"
#include "G4Positron.hh"
#include "G4PionPlus.hh"
#include "G4PionMinus.hh"
 
//Geant4
#include "G4ParticleTable.hh"
#include "Randomize.hh"
 
// HepMCHelpers include
#include "TruthUtils/HepMCHelpers.h"
 
#include "GaudiKernel/ThreadLocalContext.h"
 
// G4 sensitive detector includes
#include "G4SDManager.hh"
#include "ISF_FastCaloSimParametrization/CaloCellContainerSD.h"
 
#undef FCS_DEBUG
 
FastCaloSim::FastCaloSim(const std::string& name,
                         G4Region* region,
                         const PublicToolHandle<IFastCaloSimCaloTransportation>& FastCaloSimCaloTransportation,
                         const PublicToolHandle<IFastCaloSimCaloExtrapolation>& FastCaloSimCaloExtrapolation,
                         const PublicToolHandle<IG4CaloTransportTool>& G4CaloTransportTool,
                         const PublicToolHandle<IPunchThroughSimWrapper>& PunchThroughSimWrapper,
                         const ServiceHandle<ISF::IFastCaloSimParamSvc>& FastCaloSimSvc,
                         const std::string& CaloCellContainerSDName,
                         bool doG4Transport,
                         bool doPunchThrough,
                         FastCaloSimTool * /*FastCaloSimTool*/)
 
: G4VFastSimulationModel(name, region),
  m_FastCaloSimCaloTransportation(FastCaloSimCaloTransportation), 
  m_FastCaloSimCaloExtrapolation(FastCaloSimCaloExtrapolation),
  m_G4CaloTransportTool(G4CaloTransportTool),
  m_PunchThroughSimWrapper(PunchThroughSimWrapper),
  m_FastCaloSimSvc(FastCaloSimSvc),
  m_CaloCellContainerSDName(CaloCellContainerSDName),
  m_doG4Transport(doG4Transport),
  m_doPunchThrough(doPunchThrough)
{
}
 
 
G4bool FastCaloSim::IsApplicable(const G4ParticleDefinition& particleType)
{
  // Check whether we can simulate the particle with FastCaloSim
  bool isPhoton   = &particleType == G4Gamma::GammaDefinition();
  bool isElectron = &particleType == G4Electron::ElectronDefinition();
  bool isPositron = &particleType == G4Positron::PositronDefinition();
  bool isHadron   = MC::isHadron(particleType.GetPDGEncoding());
 
  // FastCaloSim is applicable if it is photon, electron, positron or any hadron
  bool isApplicable = isPhoton || isElectron || isPositron || isHadron;
 
  #ifdef FCS_DEBUG
    const std::string pName = particleType.GetParticleName();
    G4cout<< "[FastCaloSim::IsApplicable] Got " << pName <<G4endl;
    if(isApplicable) G4cout<<"[FastCaloSim::IsApplicable] APPLICABLE"<<G4endl;
    else G4cout<<"[FastCaloSim::IsApplicable] NOT APPLICABLE"<<G4endl;
  #endif
 
 
  return isApplicable;
}
 
G4bool FastCaloSim::ModelTrigger(const G4FastTrack& fastTrack)
{
 
  #ifdef FCS_DEBUG
    G4cout<<"[FastCaloSim::ModelTrigger] Got particle with "                                                      <<"\n"
                                    <<" pdg=" <<fastTrack.GetPrimaryTrack() -> GetDefinition()->GetPDGEncoding()  <<"\n"
                                    <<" Ekin="<<fastTrack.GetPrimaryTrack() -> GetKineticEnergy()                 <<"\n"
                                    <<" p="   <<fastTrack.GetPrimaryTrack() -> GetMomentum().mag()                <<"\n"
                                    <<" x="   <<fastTrack.GetPrimaryTrack() -> GetPosition().x()                  <<"\n"
                                    <<" y="   <<fastTrack.GetPrimaryTrack() -> GetPosition().y()                  <<"\n"
                                    <<" z="   <<fastTrack.GetPrimaryTrack() -> GetPosition().z()                  <<"\n"
                                    <<" r="   <<fastTrack.GetPrimaryTrack() -> GetPosition().perp()               <<"\n"
                                    <<" eta=" <<fastTrack.GetPrimaryTrack() -> GetMomentum().eta()                <<"\n"
                                    <<" phi=" <<fastTrack.GetPrimaryTrack() -> GetMomentum().phi()                <<"\n"
                                    <<G4endl;
  #endif
 
 
  // Simulate particles below 50 keV with Geant4 to have same config as ISF implementation 
  if (fastTrack.GetPrimaryTrack() -> GetKineticEnergy() < 0.05) {
      #ifdef FCS_DEBUG
        G4cout<<"[FastCaloSim::ModelTrigger] Particle below 50 keV threshold. Passing to G4. "<<G4endl;
      #endif
    return false;
  }
 
  // Check if triggered particle is really on the ID-Calo (parametrization) boundary
  if (!passedIDCaloBoundary(fastTrack)) {
    #ifdef FCS_DEBUG
      G4cout<<"[FastCaloSim::ModelTrigger] Particle failed passedIDCaloBoundary z="<<fastTrack.GetPrimaryTrack() -> GetPosition().z()<<" r="<<fastTrack.GetPrimaryTrack() -> GetPosition().perp()<<G4endl;
    #endif
    return false;
  }
 
  // Set minimum kinetic energy of pions and other hadrons required to be passed to FastCaloSim
  float minEkinPions = 200;
  float minEkinOtherHadrons = 400;
 
  // Get particle definition 
  const G4ParticleDefinition * G4Particle = fastTrack.GetPrimaryTrack() -> GetDefinition();
  // Get particle kinetic energy
  const float Ekin = fastTrack.GetPrimaryTrack() -> GetKineticEnergy();
  
  // Check particle type
  bool isPhoton    = G4Particle == G4Gamma::Definition();
  bool isElectron  = G4Particle == G4Electron::Definition();
  bool isPositron  = G4Particle == G4Positron::Definition();
  bool isPionPlus  = G4Particle == G4PionPlus::Definition();
  bool isPionMinus = G4Particle == G4PionMinus::Definition();
 
  // Pass all photons, electrons and positrons to FastCaloSim
  if (isPhoton || isElectron || isPositron){
    #ifdef FCS_DEBUG
      G4cout<<"[FastCaloSim::ModelTrigger] Model triggered"<<G4endl;
    #endif
    return true;
  }
 
  // Require minimum kinetic energy of pions needed to be passed to FastCaloSim
  if (isPionPlus || isPionMinus){
    bool passMinEkinPions = Ekin > minEkinPions;
    
    #ifdef FCS_DEBUG
      if(passMinEkinPions) G4cout<<"[FastCaloSim::ModelTrigger] Model triggered"<<G4endl;
      else G4cout<<"[FastCaloSim::ModelTrigger] Pion with Ekin="<<Ekin<<" below the minimum "<<minEkinPions<<" MeV threshold. Model not triggered."<<G4endl;
    #endif
 
    return passMinEkinPions;
  
  }
 
  // Require minimum kinetic energy of other hadrons needed to be passed to FastCaloSim
  bool passMinEkinOtherHadrons = Ekin > minEkinOtherHadrons;
 
  #ifdef FCS_DEBUG
    if(passMinEkinOtherHadrons) G4cout<<"[FastCaloSim::ModelTrigger] Model triggered"<<G4endl;
    else G4cout<<"[FastCaloSim::ModelTrigger] Other hadron with Ekin="<<Ekin<<" below the minimum "<<minEkinOtherHadrons<<" MeV threshold. Model not triggered."<<G4endl;
  #endif
 
  return passMinEkinOtherHadrons;
}
 
void FastCaloSim::DoIt(const G4FastTrack& fastTrack, G4FastStep& fastStep)
{
  if (auto* eventInfo = AtlasG4EventUserInfo::GetEventUserInfo()) {
    Gaudi::Hive::setCurrentContext(eventInfo->GetEventContext());
  }
 
  TFCSSimulationState simState(G4Random::getTheEngine());
  TFCSTruthState truthState;
  TFCSExtrapolationState extrapolState;
  
  // Get Geant4 primary track
  const G4Track * G4PrimaryTrack = fastTrack.GetPrimaryTrack(); 
  // Get Geant4 particle definition
  const G4ParticleDefinition * G4Particle = G4PrimaryTrack -> GetDefinition();
  // Get Geant4 particle pdgID
  signed int pdgID = G4Particle -> GetPDGEncoding();
 
  // Do not simulate particles below 10 MeV
  if(G4PrimaryTrack -> GetKineticEnergy() < 10){
    #ifdef FCS_DEBUG
      G4cout<<"[FastCaloSim::DoIt] Skipping particle with Ekin: " << G4PrimaryTrack -> GetKineticEnergy() <<" MeV. Below the 10 MeV threshold"<<G4endl;
    #endif 
    fastStep.KillPrimaryTrack();
    return;
  }
  // Decide on which FastCaloSim parametrization to use (electron, photon or pion)
  if(G4Particle == G4Electron::Definition() ||  G4Particle == G4Positron::Definition() || G4Particle == G4Gamma::Definition())
  { 
    // Use egamma parametrization for simulation of electrons and photons
    truthState.set_pdgid(pdgID);
  }
  else{
    // Use pion parametrization for simulation of all hadrons
    truthState.set_pdgid(G4PionPlus::Definition() -> GetPDGEncoding());
  }
 
  // Set the kinematics of the FastCaloSim truth state
  truthState.SetPtEtaPhiM(G4PrimaryTrack -> GetMomentum().perp(), 
                          G4PrimaryTrack -> GetMomentum().eta(), 
                          G4PrimaryTrack -> GetMomentum().phi(), 
                          G4Particle -> GetPDGMass());
  
  // Set the vertex of the FastCaloSim truth state
  truthState.set_vertex(G4PrimaryTrack -> GetPosition().x(), 
                        G4PrimaryTrack -> GetPosition().y(), 
                        G4PrimaryTrack -> GetPosition().z());
 
 
  /* For anti protons and anti-neutrons the kinetic energy should be
  calculated as Ekin = E() + M() instead of E() - M() this is 
  achieved by setting an Ekin offset of 2*M() to the truth state */
  if(pdgID == -2212 || pdgID == -2112) truthState.set_Ekin_off(2 * G4Particle -> GetPDGMass());
 
 
  // Perform particle transportation through calorimeter system eiher with ATLAS tracking tools or with Geant4
  std::vector<G4FieldTrack> caloSteps = m_doG4Transport ? m_G4CaloTransportTool -> transport(*G4PrimaryTrack) 
                                                        : m_FastCaloSimCaloTransportation -> transport(&truthState, false);
 
  // Extrapolate transported stepos to ID-Calo boundary and all layers of the calorimeter system
  m_FastCaloSimCaloExtrapolation->extrapolate(extrapolState, &truthState, caloSteps);
  
  // Do not simulate further if extrapolation to ID - Calo boundary fails
  if(extrapolState.IDCaloBoundary_eta() == -999){
    #ifdef FCS_DEBUG
      G4cout<<"[FastCaloSim::DoIt] Killing particle as extrapolation failed"<<G4endl;
    #endif
    fastStep.KillPrimaryTrack();
    return;
  }
  // Perform the actual FastCaloSim simulation
  if(m_FastCaloSimSvc->simulate(simState, &truthState, &extrapolState).isFailure()){
    G4Exception("FastCaloSimSvc", "FailedSimulationCall", FatalException, "FastCaloSimSvc: Simulation call failed.");
    abort(); 
  }
 
  #ifdef FCS_DEBUG
    G4cout<<"[FastCaloSim::DoIt] pdgID of G4PrimaryTrack: " << pdgID << G4endl;
    G4cout<<"[FastCaloSim::DoIt] Energy returned: " << simState.E() << G4endl;
    G4cout<<"[FastCaloSim::DoIt] Energy fraction for layer: " << G4endl;
    for (int s = 0; s < 24; s++) G4cout<<"[FastCaloSim::DoIt]   Sampling " << s << " energy " << simState.E(s) << G4endl;
  #endif
 
  // Retrieve the associated CaloCellContainer sensitive detector
  CaloCellContainerSD * caloCellContainerSD = getCaloCellContainerSD();
  // Record the cells 
  caloCellContainerSD->recordCells(simState);
 
  // Do punchthrough here (secondaries), after the main simulation
  if (m_doPunchThrough){
    // necessary for determining particle type and properties (mass etc)
    G4ParticleTable *ptable = G4ParticleTable::GetParticleTable(); 
    
    // Get simulated energy
    const double simE = simState.E();
 
    // Get energy fraction in layers into vector
    std::vector<double> simEfrac;
    for (unsigned int i = 0; i < 24; i++){simEfrac.push_back(simState.Efrac(i));}
 
    // run actual method (no return, it will do fastStep.CreateSecondaryTrack(...) under the hood)
    m_PunchThroughSimWrapper->DoPunchThroughSim(*ptable, G4Random::getTheEngine(), simE, std::move(simEfrac), fastTrack, fastStep);
  }
 
  // Clean up the auxiliary info from the simulation state
  simState.DoAuxInfoCleanup();
 
  // Finally kill the primary track after all simulation steps done
  fastStep.KillPrimaryTrack();
  fastStep.ProposePrimaryTrackPathLength(0.0);
}
 
CaloCellContainerSD * FastCaloSim::getCaloCellContainerSD(){
  
  G4SDManager *sdm = G4SDManager::GetSDMpointer();
  G4VSensitiveDetector * vsd = sdm->FindSensitiveDetector((G4String)m_CaloCellContainerSDName);
 
  if (!vsd){
    G4Exception("FastCaloSimSvc", "FailedFindSensitiveDetector", FatalException, "FastCaloSimSvc: Failed getting CaloCellContainer SD.");
    abort();
  }
  // Cast G4VSensitiveDetector to CaloCellContainerSD
  CaloCellContainerSD * caloCellContainerSD = dynamic_cast<CaloCellContainerSD*>(vsd);
  
  if (!caloCellContainerSD){
    G4Exception("FastCaloSimSvc", "FailedCastSensitiveDetector", FatalException, "FastCaloSimSvc: Failed casting G4VSensitiveDetector.");
    abort();
  }
  return caloCellContainerSD;
}
 
 
G4bool FastCaloSim::passedIDCaloBoundary(const G4FastTrack& fastTrack){
 
 
  /* Method checks if particle has crossed the ID-Calo boundary, defined using three cylinders with pairs of r/z values 
  We also perform a directional check to make sure that the particle does not originate from any backscatter from the MS or CALO */
 
  // NOTE:
  // For the inner beam pipe section, innerBeamPipeZ = 4185 corresponds to original AFII boundary, while 
  // innerBeamPipeZ = 4587 corresponds to the CALO::CALO boundary which should be used instead as there 
  // is no triggering volume at this point and we will trigger slightly later than the AFII boundary, so 
  // passedIDCaloBoundary would fail and we would simulate this part with Geant4
 
  // Barrel
  const float barrelR = 1148;
  const float barrelZ = 3549.5;
  // Inner beam pipe section
  const float innerBeamPipeR = 120;
  const float innerBeamPipeZ = 4587;
  // Outer beam pipe section
  const float outerBeamPipeR = 41;
  const float outerBeamPipeZ = 6783;
 
  // Get particle position
  const G4ThreeVector particlePosition = fastTrack.GetPrimaryTrack() -> GetPosition();
  // Get r and z values of position
  const float r = particlePosition.perp();
  const float z = particlePosition.z();
  // Get direction of particle 
  const G4ThreeVector particleDirection = fastTrack.GetPrimaryTrack() -> GetMomentum();
  // Construct the helper line to decide if particle comes from ID or is backscatter from CALO
  const G4ThreeVector helperLine = particlePosition + particleDirection;
 
  // Set 5cm trigger tolerance, i.e. the 'width' of the trigger boundary
  // be careful not to set this too low, else Geant4 might overjump your trigger boundary and simulate everything with G4
  const float triggerTolerance = 50;
 
  // Barrel boundary (horizontal surfaces)
  if (std::abs(z) <= barrelZ + triggerTolerance) {
    if (r >= barrelR && r < barrelR + triggerTolerance) return helperLine.perp() >= barrelR;
  }
  // Beam pipe boundary (horizontal surfaces)
  if (std::abs(z) >= barrelZ && std::abs(z) <= innerBeamPipeZ + triggerTolerance){
    if (r >= innerBeamPipeR && r < innerBeamPipeR + triggerTolerance) return helperLine.perp() >= innerBeamPipeR;
  }
  if (std::abs(z) >= innerBeamPipeZ && std::abs(z) <= outerBeamPipeZ){
    if (r >= outerBeamPipeR && r < outerBeamPipeR + triggerTolerance) return helperLine.perp() >= outerBeamPipeR;
  }
  // Barrel boundary (vertical surfaces)
  if (r >= outerBeamPipeR && r<= innerBeamPipeR){
    if (std::abs(z) >= innerBeamPipeZ && std::abs(z) < innerBeamPipeZ + triggerTolerance) return std::abs(helperLine.z()) >= innerBeamPipeZ;
  }
  // Beam pipe boundary (vertical surfaces)
  if (r >= innerBeamPipeR && r <= barrelR){
    if (std::abs(z) >= barrelZ && std::abs(z) < barrelZ + triggerTolerance) return std::abs(helperLine.z()) >= barrelZ;
  }
  
  return false;
 
}