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G4eeToPGammaModel.cc
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26 // $Id: G4eeToPGammaModel.cc 66996 2013-01-29 14:50:52Z gcosmo $
27 //
28 // -------------------------------------------------------------------
29 //
30 // GEANT4 Class header file
31 //
32 //
33 // File name: G4eeToPGammaModel
34 //
35 // Author: Vladimir Ivanchenko
36 //
37 // Creation date: 25.10.2003
38 //
39 // Modifications:
40 //
41 //
42 // -------------------------------------------------------------------
43 //
44 
45 
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48 
49 #include "G4eeToPGammaModel.hh"
50 #include "Randomize.hh"
51 #include "G4PhysicalConstants.hh"
52 #include "G4SystemOfUnits.hh"
53 #include "G4PionZero.hh"
54 #include "G4Eta.hh"
55 #include "G4Gamma.hh"
56 #include "G4DynamicParticle.hh"
57 #include "G4PhysicsVector.hh"
58 #include "G4PhysicsLinearVector.hh"
59 #include "G4eeCrossSections.hh"
60 
61 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
62 
63 using namespace std;
64 
65 G4eeToPGammaModel::G4eeToPGammaModel(G4eeCrossSections* cr, const G4String& npart):
66  cross(cr)
67 {
68  pi0 = G4PionZero::PionZero();
69  if(npart == "pi0") {
70  massR = 782.62*MeV;
71  particle = pi0;
72  } else {
73  massR = 1019.46*MeV;
74  particle = G4Eta::Eta();
75  }
76  massP = particle->GetPDGMass();
77 }
78 
79 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
80 
81 G4eeToPGammaModel::~G4eeToPGammaModel()
82 {}
83 
84 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
85 
86 G4double G4eeToPGammaModel::ThresholdEnergy() const
87 {
88  return LowEnergy();
89 }
90 
91 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
92 
93 G4double G4eeToPGammaModel::PeakEnergy() const
94 {
95  return massR;
96 }
97 
98 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
99 
100 G4double G4eeToPGammaModel::ComputeCrossSection(G4double e) const
101 {
102  G4double ee = std::min(HighEnergy(),e);
103  G4double xs;
104  if(particle == pi0) xs = cross->CrossSectionPi0G(ee);
105  else xs = cross->CrossSectionEtaG(ee);
106  return xs;
107 }
108 
109 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
110 
111 G4PhysicsVector* G4eeToPGammaModel::PhysicsVector(G4double emin,
112  G4double emax) const
113 {
114  G4double tmin = std::max(emin, ThresholdEnergy());
115  G4double tmax = std::max(tmin, emax);
116  G4int nbins = (G4int)((tmax - tmin)/(5.*MeV));
117  G4PhysicsVector* v = new G4PhysicsLinearVector(emin,emax,nbins);
118  v->SetSpline(true);
119  return v;
120 }
121 
122 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
123 
124 void G4eeToPGammaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* newp,
125  G4double e, const G4ThreeVector& direction)
126 {
127  G4double egam = 0.5*e*(1.0 - massP*massP/(massR*massR));
128  G4double tkin = e - egam - massP;
129  if(tkin < 0.0) tkin = 0.0;
130  G4double cost;
131  do {
132  cost = 2.0*G4UniformRand() - 1.0;
133  } while( 2.0*G4UniformRand() > 1.0 + cost*cost );
134 
135  G4double sint = sqrt(1.0 - cost*cost);
136  G4double phi = twopi * G4UniformRand();
137 
138  G4ThreeVector dir(sint*cos(phi),sint*sin(phi), cost);
139  dir.rotateUz(direction);
140 
141  // create G4DynamicParticle objects
142  G4DynamicParticle* p1 =
143  new G4DynamicParticle(particle,dir,tkin);
144  G4DynamicParticle* p2 =
145  new G4DynamicParticle(G4Gamma::Gamma(),-dir,egam);
146  newp->push_back(p1);
147  newp->push_back(p2);
148 }
149 
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151 
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