particleGun/src/PrimaryGeneratorAction0.cc

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0025 //
0026 /// \file eventgenerator/particleGun/src/PrimaryGeneratorAction0.cc
0027 /// \brief Implementation of the PrimaryGeneratorAction0 class
0028 //
0029 //
0030 //
0031 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0032 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0033
0034 #include "PrimaryGeneratorAction0.hh"
0035
0036 #include "PrimaryGeneratorAction.hh"
0037
0038 #include "G4Event.hh"
0039 #include "G4ParticleGun.hh"
0040 #include "G4SystemOfUnits.hh"
0041 #include "Randomize.hh"
0042
0043 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0044
0045 PrimaryGeneratorAction0::PrimaryGeneratorAction0(G4ParticleGun* gun) : fParticleGun(gun)
0046 {
0047   // solid angle
0048   //
0049   G4double alphaMin = 0 * deg;  // alpha in [0,pi]
0050   G4double alphaMax = 60 * deg;
0051   fCosAlphaMin = std::cos(alphaMin);
0052   fCosAlphaMax = std::cos(alphaMax);
0053
0054   fPsiMin = 0 * deg;  // psi in [0, 2*pi]
0055   fPsiMax = 360 * deg;
0056 }
0057
0058 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0059
0060 void PrimaryGeneratorAction0::GeneratePrimaries(G4Event* anEvent)
0061 {
0062   // vertex position fixed
0063   //
0064   G4double x0 = 0 * mm, y0 = 0 * mm, z0 = 0 * mm;
0065   fParticleGun->SetParticlePosition(G4ThreeVector(x0, y0, z0));
0066
0067   // direction uniform in solid angle
0068   //
0069   G4double cosAlpha = fCosAlphaMin - G4UniformRand() * (fCosAlphaMin - fCosAlphaMax);
0070   G4double sinAlpha = std::sqrt(1. - cosAlpha * cosAlpha);
0071   G4double psi = fPsiMin + G4UniformRand() * (fPsiMax - fPsiMin);
0072
0073   G4double ux = sinAlpha * std::cos(psi), uy = sinAlpha * std::sin(psi), uz = cosAlpha;
0074
0075   fParticleGun->SetParticleMomentumDirection(G4ThreeVector(ux, uy, uz));
0076
0077   fParticleGun->GeneratePrimaryVertex(anEvent);
0078 }
0079
0080 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......