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/// \file field/field05/src/F05PrimaryGeneratorAction.cc
/// \brief Implementation of the F05PrimaryGeneratorAction class
//

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#include "F05PrimaryGeneratorAction.hh"

#include "F05DetectorConstruction.hh"

#include "G4Event.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "Randomize.hh"
#include "G4SystemOfUnits.hh"

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F05PrimaryGeneratorAction::F05PrimaryGeneratorAction(void)
{
  G4int n_particle = 1;
  fParticleGun  = new G4ParticleGun(n_particle);
  
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* particle = particleTable->FindParticle("mu+");

  fParticleGun->SetParticleDefinition(particle);
}

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F05PrimaryGeneratorAction::~F05PrimaryGeneratorAction()
{
  delete fParticleGun;
}

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void F05PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
  //

  G4double Pmu = 517.6*MeV;
  G4double mu_mass = 105.658*MeV;
  G4double Emu = std::sqrt(Pmu*Pmu + mu_mass*mu_mass);
  G4double Kmu = Emu - mu_mass;

  G4double x0 = -6.99*m;
  G4double y0 =  0.00*m; 
  G4double z0 =  0.00*m;

  fParticleGun->SetParticleEnergy(Kmu);
  fParticleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));
  fParticleGun->SetParticlePolarization(G4ThreeVector(0.,1.,0.));
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(0.,1.,0.));

  fParticleGun->GeneratePrimaryVertex(anEvent);
}

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