ParticleDecayer.h

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef GENERATORMODULES_PARTICLEDECAYER_H
#define GENERATORMODULES_PARTICLEDECAYER_H
 
#include "GeneratorModules/GenModule.h" //inheritance
#include "GeneratorModules/GenData.h" //inheritance
#include "CLHEP/Vector/LorentzVector.h" //member
#include "AtlasHepMC/GenEvent.h" //typedef
#include "AtlasHepMC/GenVertex.h" //typedef for GenVertexPtr
#include "AtlasHepMC/SimpleVector.h" //typedef for FourVector
#include "AtlasHepMC/GenParticle.h" //typedef for GenParticlePtr
#include <vector>
 
 
namespace CLHEP{
  class HepRandomEngine;
}
 
 
 
class ParticleDecayer: public GenModule {
 
 public:
  
  ParticleDecayer(const std::string& name, ISvcLocator* pSvcLocator);
 
  ~ParticleDecayer() = default;
  
  StatusCode genInitialize();
  StatusCode fillEvt(HepMC::GenEvent*);
  
 private:
 
  //name of the MC truth container  
  std::string m_truthParticleContainerName;
  // LeptonJet type: 1 = one dark photon per LeptonJet, 2 = two dark pjotons per LeptonJet
  int m_LJType{};
  //new PDG ID of the scalar 
  int m_scalarPDGID{};
  //new mass of the scalar in MeV
  double m_scalarMass{};
  //mass of the dark photon (MeV)
  double m_particleMass{};
  //PDG ID of the dark photon 
  int m_particleID{};
  //lifetime of the dark photon
  double m_particleLifeTime{}; 
  //new PDG_ID of thedark photon 
  int m_particlePDGID{};
  //polarization of the dark photon
  int m_particlePolarization{}; 
  //opposite polarization switch in case of two dark photons
  bool m_oppositePolarization{};
  //BR of dark photon decay to electrons
  double m_BRElectron{};
  //BR of dark photon decay to muons 
  double m_BRMuon{};
  //BR of dark photon decay to pions 
  double m_BRPion{};
 
  bool   m_doUniformDecay{};
  bool   m_doExponentialDecay{};
  bool   m_expDecayDoVariableLifetime{};
  double m_expDecayFractionToKeep{};
  bool   m_expDecayDoTruncateLongDecays{};
  bool   m_decayOnlyStable{};
 
  double m_barrelRadius;
  double m_endCapDistance;
  double m_thetaEndCapBarrel;
 
  std::unique_ptr<GenData> m_gendata{nullptr};
 
  void       addParticle   (HepMC::GenVertexPtr, int pdg, HepMC::FourVector, int statusCode); //add particles to the evgen file
 
  double rnd_ExpLifetime(CLHEP::HepRandomEngine* engine, double ct);
  double rnd_DoubleRange(CLHEP::HepRandomEngine* engine, double a, double b);
  double cosgen(CLHEP::HepRandomEngine* engine, int itype);
 
  StatusCode DFTwoBodyDecay( CLHEP::HepRandomEngine* engine, HepMC::GenParticlePtr, int );
  StatusCode setDecayPosition ( CLHEP::HepRandomEngine* engine, HepMC::GenParticlePtr, HepMC::GenEvent*, bool doScalarDecay=false );
  StatusCode changeMass( HepMC::GenParticlePtr, double );
  StatusCode getDecayProducts( CLHEP::HepRandomEngine* engine, CLHEP::HepLorentzVector, double, std::vector<CLHEP::HepLorentzVector>&, int decayType = 0);
 
  //four momentum of the dark photon
  CLHEP::HepLorentzVector m_boostLV;
  //production vertex of the dark photon/scalar
  CLHEP::HepLorentzVector m_posLV;  
  //decay vertex of the first dark photon
  CLHEP::HepLorentzVector m_posLV1;  
  //decay vertex of the second dark photon
  CLHEP::HepLorentzVector m_posLV2;  
  //counter
  int m_eventCounter{};  
};
 
#endif