particleGun/src/PrimaryGeneratorAction3.cc

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0025 //
0026 /// \file eventgenerator/particleGun/src/PrimaryGeneratorAction3.cc
0027 /// \brief Implementation of the PrimaryGeneratorAction3 class
0028 //
0029 //
0030 //
0031 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0032 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0033
0034 #include "PrimaryGeneratorAction3.hh"
0035
0036 #include "PrimaryGeneratorAction.hh"
0037
0038 #include "G4Event.hh"
0039 #include "G4ParticleDefinition.hh"
0040 #include "G4ParticleGun.hh"
0041 #include "G4ParticleTable.hh"
0042 #include "G4PhysicalConstants.hh"
0043 #include "G4SystemOfUnits.hh"
0044 #include "Randomize.hh"
0045
0046 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0047
0048 PrimaryGeneratorAction3::PrimaryGeneratorAction3(G4ParticleGun* gun) : fParticleGun(gun)
0049 {
0050   // direction
0051   //
0052   G4double theta = 90 * deg, phi = 45 * deg;
0053   fNewUz = G4ThreeVector(std::sin(theta) * std::cos(phi), std::sin(theta) * std::sin(phi),
0054                          std::cos(theta));
0055
0056   fAlphaMax = 15 * deg;
0057 }
0058
0059 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0060
0061 void PrimaryGeneratorAction3::GeneratePrimaries(G4Event* anEvent)
0062 {
0063   // particle direction uniform around fNewUz axis
0064   //
0065   // 1- in World frame
0066   // cosAlpha uniform in [cos(0), cos(fAlphaMax)]
0067   G4double cosAlpha = 1. - G4UniformRand() * (1. - std::cos(fAlphaMax));
0068   G4double sinAlpha = std::sqrt(1. - cosAlpha * cosAlpha);
0069   G4double psi = twopi * G4UniformRand();  // psi uniform in [0, 2*pi]
0070   G4ThreeVector dir(sinAlpha * std::cos(psi), sinAlpha * std::sin(psi), cosAlpha);
0071
0072   // 2- rotate dir   (rotateUz transforms uz to fNewUz)
0073   dir.rotateUz(fNewUz);
0074
0075   fParticleGun->SetParticleMomentumDirection(dir);
0076
0077   // set energy
0078   //
0079   fParticleGun->SetParticleEnergy(1 * MeV);
0080
0081   // create vertex
0082   //
0083   fParticleGun->GeneratePrimaryVertex(anEvent);
0084 }
0085
0086 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......