| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class header file
30 //
31 //
32 // File name: G4eeTo3PiModel
33 //
34 // Author: Vladimir Ivanchenko
35 //
36 // Creation date: 25.10.2003
37 //
38 // Modifications:
39 //
40 //
41 // -------------------------------------------------------------------
42 //
43
44
45 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
46 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
47
48 #include "G4eeTo3PiModel.hh"
49 #include "Randomize.hh"
50 #include "G4SystemOfUnits.hh"
51 #include "G4PionPlus.hh"
52 #include "G4PionMinus.hh"
53 #include "G4PionZero.hh"
54 #include "G4DynamicParticle.hh"
55 #include "G4PhysicsVector.hh"
56 #include "G4PhysicsLinearVector.hh"
57 #include "G4eeCrossSections.hh"
58 #include "G4RandomDirection.hh"
59 #include <complex>
60
61 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
62
63 using namespace std;
64
65 G4eeTo3PiModel::G4eeTo3PiModel(G4eeCrossSections* cr,
66 G4double maxkinEnergy,
67 G4double binWidth)
68 : G4Vee2hadrons(cr,
69 0.41612*GeV, //threshold
70 maxkinEnergy,
71 binWidth)
72 {
73 G4cout << "####G4eeTo3PiModel####" << G4endl;
74
75 massPi = G4PionPlus::PionPlus()->GetPDGMass();
76 massPi0 = G4PionZero::PionZero()->GetPDGMass();
77 massOm = 782.62*MeV;
78 massPhi = 1019.46*MeV;
79 gmax = 3.0e-8;
80 }
81
82 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
83
84 G4eeTo3PiModel::~G4eeTo3PiModel()
85 {}
86
87 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
88
89 G4double G4eeTo3PiModel::PeakEnergy() const
90 {
91 G4double e = massOm;
92 if(HighEnergy() > massPhi) { e = massPhi; }
93 return e;
94 }
95
96 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
97
98 G4double G4eeTo3PiModel::ComputeCrossSection(G4double e) const
99 {
100 return cross->CrossSection3pi(e);
101 }
102
103 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
104
105 void G4eeTo3PiModel::SampleSecondaries(std::vector<G4DynamicParticle*>* newp,
106 G4double e, const G4ThreeVector& direction)
107 {
108
109 G4double x0 = massPi0/e;
110 G4double x1 = massPi/e;
111
112 G4LorentzVector w0(0.,0.,0.,0.), w1(0.,0.,0.,0.), w2(0.,0.,0.,0.);
113 G4ThreeVector dir0, dir1;
114 G4double e0, p0, e2, p, gg, m01, m02, m12;
115
116 // max pi0 energy
117 G4double edel = 0.5*e*(1.0 + x0*x0 - 4.0*x1*x1) - massPi0;
118
119 const G4int nmax = 200;
120 G4int nn = 0;
121 do {
122 ++nn;
123 // pi0 sample
124 e0 = edel*G4UniformRand() + massPi0;
125 p0 = sqrt(e0*e0 - massPi0*massPi0);
126 dir0 = G4RandomDirection();
127 w0 = G4LorentzVector(p0*dir0.x(),p0*dir0.y(),p0*dir0.z(),e0);
128
129 // pi+pi- pair
130 w1 = G4LorentzVector(-p0*dir0.x(),-p0*dir0.y(),-p0*dir0.z(),e-e0);
131 G4ThreeVector bst = w1.boostVector();
132 e2 = 0.25*w1.m2();
133
134 // pi+
135 p = sqrt(e2 - massPi*massPi);
136 dir1 = G4RandomDirection();
137 w2 = G4LorentzVector(p*dir1.x(),p*dir1.y(),p*dir1.z(),sqrt(e2));
138 // pi-
139 w1.set(-w2.px(), -w2.py(), -w2.pz(), w2.e());
140
141 w1.boost(bst);
142 w2.boost(bst);
143
144 G4double px2 = w2.x();
145 G4double py2 = w2.y();
146 G4double pz2 = w2.z();
147
148 G4double px1 = w1.x();
149 G4double py1 = w1.y();
150 G4double pz1 = w1.z();
151
152 m01 = w0*w1;
153 m02 = w0*w2;
154 m12 = w1*w2;
155
156 G4double px = py1*pz2 - py2*pz1;
157 G4double py = pz1*px2 - pz2*px1;
158 G4double pz = px1*py2 - px2*py1;
159
160 gg = (px*px + py*py + pz*pz)*
161 norm( 1.0/cross->DpRho(m01) + 1.0/cross->DpRho(m02)
162 + 1.0/cross->DpRho(m12) );
163
164 if(gg > gmax) {
165 G4cout << "G4eeTo3PiModel::SampleSecondaries WARNING matrix element g= "
166 << gg << " > " << gmax << " (majoranta)" << G4endl;
167 gmax = gg;
168 }
169 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
170 } while( gmax*G4UniformRand() > gg || nn < nmax);
171
172 w0.rotateUz(direction);
173 w1.rotateUz(direction);
174 w2.rotateUz(direction);
175
176 // create G4DynamicParticle objects
177 G4DynamicParticle* dp0 =
178 new G4DynamicParticle(G4PionZero::PionZero(), w0);
179 G4DynamicParticle* dp1 =
180 new G4DynamicParticle(G4PionPlus::PionPlus(), w1);
181 G4DynamicParticle* dp2 =
182 new G4DynamicParticle(G4PionMinus::PionMinus(), w2);
183 newp->push_back(dp0);
184 newp->push_back(dp1);
185 newp->push_back(dp2);
186 }
187
188 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
189
190