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//
/// \file PrimaryGeneratorAction.cc
/// \brief Implementation of the PrimaryGeneratorAction class
//
//

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#include "PrimaryGeneratorAction.hh"
#include "G4Event.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "globals.hh"
#include "G4SystemOfUnits.hh"

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PrimaryGeneratorAction::PrimaryGeneratorAction() : G4VUserPrimaryGeneratorAction(),
                                                   fParticleGun( nullptr ) {
  G4int n_particle = 1;
  fParticleGun = new G4ParticleGun( n_particle );
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  //***LOOKHERE*** Default particle, tau-, and energy, 500 GeV
  fParticleGun->SetParticleDefinition( particleTable->FindParticle( "tau-" ) );
  fParticleGun->SetParticleEnergy( 500.0*GeV );
  SetGunPosition();
}

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

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void PrimaryGeneratorAction::SetGunPosition() const {
  // Shoot the particle from the origin
  fParticleGun->SetParticlePosition( G4ThreeVector( 0.0, 0.0, 0.0 ) );  //***LOOKHERE***
}

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void PrimaryGeneratorAction::GeneratePrimaries( G4Event* anEvent ) {
  G4ThreeVector v( 1.0, 0.0, 0.0 );  //***LOOKHERE*** default shoot along the x-axis
  fParticleGun->SetParticleMomentumDirection( v );
  fParticleGun->GeneratePrimaryVertex( anEvent );
}

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