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26 // -------------------------------------------------------------------
27 //
28 // GEANT4 Class header file
29 //
30 //
31 // File name: G4UniversalFluctuation
32 //
33 // Author: V.Ivanchenko make a class with the Laszlo Urban model
34 //
35 // Creation date: 03.01.2002
36 //
37 // Modifications:
38 //
39 //
40 // Class Description:
41 //
42 // Implementation of energy loss fluctuations made by L.Urban in 2021
43
44 // -------------------------------------------------------------------
45 //
46
47 #ifndef G4UniversalFluctuation_h
48 #define G4UniversalFluctuation_h 1
49
50 #include "G4VEmFluctuationModel.hh"
51 #include "G4ParticleDefinition.hh"
52 #include "G4Poisson.hh"
53 #include <CLHEP/Random/RandomEngine.h>
54
55 class G4UniversalFluctuation : public G4VEmFluctuationModel
56 {
57
58 public:
59
60 explicit G4UniversalFluctuation(const G4String& nam = "UniFluc");
61
62 ~G4UniversalFluctuation() override;
63
64 G4double SampleFluctuations(const G4MaterialCutsCouple*,
65 const G4DynamicParticle*,
66 const G4double, const G4double,
67 const G4double, const G4double) override;
68
69 G4double Dispersion(const G4Material*,
70 const G4DynamicParticle*,
71 const G4double, const G4double,
72 const G4double) override;
73
74 // Initialisation for a new particle type
75 void InitialiseMe(const G4ParticleDefinition*) override;
76
77 // Initialisation prestep
78 void SetParticleAndCharge(const G4ParticleDefinition*,
79 G4double q2) override;
80
81 // hide assignment operator
82 G4UniversalFluctuation & operator=
83 (const G4UniversalFluctuation &right) = delete;
84 G4UniversalFluctuation(const G4UniversalFluctuation&) = delete;
85
86 protected:
87
88 virtual G4double SampleGlandz(CLHEP::HepRandomEngine* rndm,
89 const G4Material*, const G4double tcut);
90
91 inline void AddExcitation(CLHEP::HepRandomEngine* rndm,
92 const G4double ax, const G4double ex,
93 G4double& eav,
94 G4double& eloss, G4double& esig2);
95
96 inline void SampleGauss(CLHEP::HepRandomEngine* rndm,
97 const G4double eav, const G4double esig2,
98 G4double& eloss);
99
100 // particle properties
101 G4double particleMass = 0.0;
102 G4double m_Inv_particleMass = DBL_MAX;
103 G4double m_massrate = DBL_MAX;
104 G4double chargeSquare = 1.0;
105
106 // material properties
107 G4double ipotFluct = 0.0;
108 G4double ipotLogFluct = 0.0;
109 G4double e0 = 0.0;
110
111 // model parameters
112 G4double minNumberInteractionsBohr = 10.0;
113 G4double minLoss;
114 G4double nmaxCont = 8.0;
115 G4double rate = 0.56;
116 G4double fw = 4.0;
117 G4double a0 = 42.0;
118 G4double w2 = 0.0;
119 G4double meanLoss = 0.0;
120
121 const G4ParticleDefinition* particle = nullptr;
122 G4double* rndmarray = nullptr;
123 G4int sizearray = 30;
124 };
125
126 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
127
128 inline void
129 G4UniversalFluctuation::AddExcitation(CLHEP::HepRandomEngine* rndm,
130 const G4double ax, const G4double ex,
131 G4double& eav,
132 G4double& eloss, G4double& esig2)
133 {
134 if(ax > nmaxCont) {
135 eav += ax*ex;
136 esig2 += ax*ex*ex;
137 } else {
138 const G4int p = (G4int)G4Poisson(ax);
139 if(p > 0) { eloss += ((p + 1) - 2.*rndm->flat())*ex; }
140 }
141 }
142
143 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
144
145 inline void
146 G4UniversalFluctuation::SampleGauss(CLHEP::HepRandomEngine* rndm,
147 const G4double eav, const G4double esig2,
148 G4double& eloss)
149 {
150 G4double x = eav;
151 const G4double sig = std::sqrt(esig2);
152 if(eav < 0.25*sig) {
153 x += (2.*rndm->flat() - 1.)*eav;
154 } else {
155 do {
156 x = G4RandGauss::shoot(rndm, eav, sig);
157 } while (x < 0.0 || x > 2*eav);
158 // Loop checking, 23-Feb-2016, Vladimir Ivanchenko
159 }
160 eloss += x;
161 }
162
163 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
164
165 #endif
166
167