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PrimaryGeneratorAction3.cc
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33 
34 #include "PrimaryGeneratorAction3.hh"
35 #include "PrimaryGeneratorAction.hh"
36 
37 #include "G4Event.hh"
38 #include "G4ParticleGun.hh"
39 #include "G4ParticleTable.hh"
40 #include "G4ParticleDefinition.hh"
41 #include "G4PhysicalConstants.hh"
42 #include "G4SystemOfUnits.hh"
43 #include "Randomize.hh"
44 
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46 
47 PrimaryGeneratorAction3::PrimaryGeneratorAction3(G4ParticleGun* gun)
48 : fParticleGun(gun)
49 {
50  // direction
51  //
52  G4double theta = 90*deg, phi = 45*deg;
53  fNewUz = G4ThreeVector(std::sin(theta)*std::cos(phi),
54  std::sin(theta)*std::sin(phi),
55  std::cos(theta));
56 
57  fAlphaMax = 15*deg;
58 }
59 
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62 PrimaryGeneratorAction3::~PrimaryGeneratorAction3()
63 { }
64 
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66 
67 void PrimaryGeneratorAction3::GeneratePrimaries(G4Event* anEvent)
68 {
69  //particle direction uniform around fNewUz axis
70  //
71  //1- in World frame
72  //cosAlpha uniform in [cos(0), cos(fAlphaMax)]
73  G4double cosAlpha = 1. - G4UniformRand()*(1.- std::cos(fAlphaMax));
74  G4double sinAlpha = std::sqrt(1. - cosAlpha*cosAlpha);
75  G4double psi = twopi*G4UniformRand(); //psi uniform in [0, 2*pi]
76  G4ThreeVector dir(sinAlpha*std::cos(psi),sinAlpha*std::sin(psi),cosAlpha);
77 
78  //2- rotate dir (rotateUz transforms uz to fNewUz)
79  dir.rotateUz(fNewUz);
80 
81  fParticleGun->SetParticleMomentumDirection(dir);
82 
83  //set energy
84  //
85  fParticleGun->SetParticleEnergy(1*MeV);
86 
87  //create vertex
88  //
89  fParticleGun->GeneratePrimaryVertex(anEvent);
90 }
91 
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