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G4UniversalFluctuation.hh
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26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class header file
30 //
31 //
32 // File name: G4UniversalFluctuation
33 //
34 // Author: V.Ivanchenko make a class with the Laszlo Urban model
35 //
36 // Creation date: 03.01.2002
37 //
38 // Modifications:
39 //
40 //
41 // Class Description:
42 //
43 // Implementation of energy loss fluctuations
44 
45 // -------------------------------------------------------------------
46 //
47 
48 #ifndef G4UniversalFluctuation_h
49 #define G4UniversalFluctuation_h 1
50 
51 
52 #include "G4VEmFluctuationModel.hh"
53 #include "G4ParticleDefinition.hh"
54 #include "G4Poisson.hh"
56 
58 {
59 
60 public:
61 
62  explicit G4UniversalFluctuation(const G4String& nam = "UniFluc");
63 
64  virtual ~G4UniversalFluctuation();
65 
67  const G4DynamicParticle*,
68  G4double,
69  G4double,
70  G4double) override;
71 
72  virtual G4double Dispersion(const G4Material*,
73  const G4DynamicParticle*,
74  G4double,
75  G4double) override;
76 
77  virtual void InitialiseMe(const G4ParticleDefinition*) final;
78 
79  // Initialisation prestep
80  virtual void SetParticleAndCharge(const G4ParticleDefinition*,
81  G4double q2) final;
82 
83 private:
84 
85  inline void AddExcitation(CLHEP::HepRandomEngine* rndm,
86  G4double a, G4double e, G4double& eav,
87  G4double& eloss, G4double& esig2);
88 
89  inline void SampleGauss(CLHEP::HepRandomEngine* rndm,
90  G4double eav, G4double esig2,
91  G4double& eloss);
92 
93  // hide assignment operator
96 
99 
101 
102  // Derived quantities
106 
107  // data members to speed up the fluctuation calculation
110 
120 
122 
127 
130 
131 };
132 
133 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
134 
135 
136 inline void
138  G4double ax, G4double ex, G4double& eav,
139  G4double& eloss, G4double& esig2)
140 {
141  if(ax > nmaxCont) {
142  eav += ax*ex;
143  esig2 += ax*ex*ex;
144  } else {
145  G4int p = G4Poisson(ax);
146  if(p > 0) { eloss += ((p + 1) - 2.*rndm->flat())*ex; }
147  }
148 }
149 
150 inline void
152  G4double eav, G4double esig2,
153  G4double& eloss)
154 {
155  G4double x = eav;
156  G4double sig = std::sqrt(esig2);
157  if(eav < 0.25*sig) {
158  x += (2.*rndm->flat() - 1.)*eav;
159  } else {
160  do {
161  x = G4RandGauss::shoot(rndm, eav, sig);
162  } while (x < 0.0 || x > 2*eav);
163  // Loop checking, 23-Feb-2016, Vladimir Ivanchenko
164  }
165  eloss += x;
166 }
167 
168 #endif
169