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G4PhotoElectricAngularGeneratorSauterGavrila.cc
Go to the documentation of this file. Or view the newest version in sPHENIX GitHub for file G4PhotoElectricAngularGeneratorSauterGavrila.cc
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27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4PhotoElectricAngularGeneratorSauterGavrila
33 //
34 // Creation date: 10 May 2004
35 //
36 // Modifications:
37 // 10 May 2003 P. Rodrigues First implementation acording with new design
38 //
39 // Class Description:
40 //
41 // Concrete class for PhotoElectric Electron Angular Distribution Generation
42 // This model is a re-implementation of the Photolectric angular distribution
43 // developed my M. Maire for the Standard EM Physics G4PhotoElectricEffect
44 //
45 // Class Description: End
46 //
47 // -------------------------------------------------------------------
48 //
49 
50 #include "G4PhotoElectricAngularGeneratorSauterGavrila.hh"
51 #include "G4PhysicalConstants.hh"
52 #include "Randomize.hh"
53 
54 G4PhotoElectricAngularGeneratorSauterGavrila::G4PhotoElectricAngularGeneratorSauterGavrila():
55  G4VEmAngularDistribution("AngularGenSauterGavrilaLowE")
56 {}
57 
58 G4PhotoElectricAngularGeneratorSauterGavrila::~G4PhotoElectricAngularGeneratorSauterGavrila()
59 {}
60 
61 G4ThreeVector&
62 G4PhotoElectricAngularGeneratorSauterGavrila::SampleDirection(
63  const G4DynamicParticle* dp,
64  G4double, G4int, const G4Material*)
65 {
66 
67  // Compute Theta distribution of the emitted electron, with respect to the
68  // incident Gamma.
69  // The Sauter-Gavrila distribution for the K-shell is used.
70 
71  G4double costeta = 1.;
72  G4double Phi = twopi * G4UniformRand();
73  G4double cosphi = std::cos(Phi);
74  G4double sinphi = std::sin(Phi);
75  G4double sinteta = 0;
76  G4double gamma = 1. + dp->GetKineticEnergy()/electron_mass_c2;
77 
78  if (gamma > 5.) {
79  fLocalDirection = dp->GetMomentumDirection();
80  return fLocalDirection;
81  // Bugzilla 1120
82  // SI on 05/09/2010 as suggested by JG 04/09/10
83  }
84 
85  G4double beta = std::sqrt((gamma - 1)*(gamma + 1))/gamma;
86  G4double b = 0.5*gamma*(gamma - 1)*(gamma - 2);
87 
88  G4double rndm,term,greject,grejsup;
89  if (gamma < 2.) grejsup = gamma*gamma*(1.+b-beta*b);
90  else grejsup = gamma*gamma*(1.+b+beta*b);
91 
92  do { rndm = 1.-2*G4UniformRand();
93  costeta = (rndm+beta)/(rndm*beta+1.);
94  term = 1.-beta*costeta;
95  greject = (1.-costeta*costeta)*(1.+b*term)/(term*term);
96  } while(greject < G4UniformRand()*grejsup);
97 
98  sinteta = std::sqrt((1 - costeta)*(1 + costeta));
99  fLocalDirection.set(sinteta*cosphi, sinteta*sinphi, costeta);
100  fLocalDirection.rotateUz(dp->GetMomentumDirection());
101  return fLocalDirection;
102 }
103 
104 void G4PhotoElectricAngularGeneratorSauterGavrila::PrintGeneratorInformation() const
105 {
106  G4cout << "\n" << G4endl;
107  G4cout << "" << G4endl;
108  G4cout << "Re-implementation of the photolectric angular distribution" << G4endl;
109  G4cout << "developed my M. Maire for the Standard EM Physics G4PhotoElectricEffect" << G4endl;
110  G4cout << "It computes the theta distribution of the emitted electron, with respect to the" << G4endl;
111  G4cout << "incident Gamma, using the Sauter-Gavrila distribution for the K-shell\n" << G4endl;
112 }