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G4eeToTwoPiModel.cc
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26 // $Id: G4eeToTwoPiModel.cc 66996 2013-01-29 14:50:52Z gcosmo $
27 //
28 // -------------------------------------------------------------------
29 //
30 // GEANT4 Class header file
31 //
32 //
33 // File name: G4eeToTwoPiModel
34 //
35 // Author: Vladimir Ivanchenko
36 //
37 // Creation date: 25.10.2003
38 //
39 // Modifications:
40 //
41 //
42 // -------------------------------------------------------------------
43 //
44 
45 
46 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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48 
49 #include "G4eeToTwoPiModel.hh"
50 #include "Randomize.hh"
51 #include "G4PhysicalConstants.hh"
52 #include "G4SystemOfUnits.hh"
53 #include "G4PionPlus.hh"
54 #include "G4PionMinus.hh"
55 #include "G4DynamicParticle.hh"
56 #include "G4PhysicsVector.hh"
57 #include "G4PhysicsLinearVector.hh"
58 #include "G4eeCrossSections.hh"
59 
60 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
61 
62 using namespace std;
63 
64 G4eeToTwoPiModel::G4eeToTwoPiModel(G4eeCrossSections* cr):
65  cross(cr)
66 {
67  massPi = G4PionPlus::PionPlus()->GetPDGMass();
68  massRho = 775.5*MeV;
69 }
70 
71 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
72 
73 G4eeToTwoPiModel::~G4eeToTwoPiModel()
74 {}
75 
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77 
78 G4double G4eeToTwoPiModel::ThresholdEnergy() const
79 {
80  return 2.0*massPi;
81 }
82 
83 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
84 
85 G4double G4eeToTwoPiModel::PeakEnergy() const
86 {
87  return massRho;
88 }
89 
90 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
91 
92 G4double G4eeToTwoPiModel::ComputeCrossSection(G4double e) const
93 {
94  G4double ee = std::min(HighEnergy(),e);
95  return cross->CrossSection2pi(ee);
96 }
97 
98 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
99 
100 G4PhysicsVector* G4eeToTwoPiModel::PhysicsVector(G4double emin,
101  G4double emax) const
102 {
103  G4double tmin = std::max(emin, 2.0*massPi);
104  G4double tmax = std::max(tmin, emax);
105  G4int nbins = (G4int)((tmax - tmin)/(5.*MeV));
106  G4PhysicsVector* v = new G4PhysicsLinearVector(emin,emax,nbins);
107  v->SetSpline(true);
108  return v;
109 }
110 
111 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
112 
113 void G4eeToTwoPiModel::SampleSecondaries(std::vector<G4DynamicParticle*>* newp,
114  G4double e, const G4ThreeVector& direction)
115 {
116 
117  G4double tkin = 0.5*e - massPi;
118  if(tkin < 0.0) tkin = 0.0;
119  G4double cost;
120  do {
121  cost = 2.0*G4UniformRand() - 1.0;
122  } while( G4UniformRand() > 1.0 - cost*cost );
123 
124  G4double sint = sqrt(1.0 - cost*cost);
125  G4double phi = twopi * G4UniformRand();
126 
127  G4ThreeVector dir(sint*cos(phi),sint*sin(phi), cost);
128  dir.rotateUz(direction);
129 
130  // create G4DynamicParticle objects
131  G4DynamicParticle* pip =
132  new G4DynamicParticle(G4PionPlus::PionPlus(),dir,tkin);
133  G4DynamicParticle* pin =
134  new G4DynamicParticle(G4PionMinus::PionMinus(),-dir,tkin);
135  newp->push_back(pip);
136  newp->push_back(pin);
137 }
138 
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140 
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