source: trunk/source/processes/electromagnetic/standard/include/G4PairProductionRelModel.hh@ 1347

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1//
2// ********************************************************************
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4// * *
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15// * use. Please see the license in the file LICENSE and URL above *
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18// * This code implementation is the result of the scientific and *
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24// ********************************************************************
25//
26// $Id: G4PairProductionRelModel.hh,v 1.9 2010/10/26 10:35:22 vnivanch Exp $
27// GEANT4 tag $Name: emstand-V09-03-24 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class header file
32//
33//
34// File name: G4PairProductionRelModel
35//
36// Author: Andreas Schaelicke
37//
38// Creation date: 02.04.2009
39//
40// Modifications:
41//
42// Class Description:
43//
44// Implementation of gamma convertion to e+e- in the field of a nucleus
45// relativistic approximation
46//
47
48// -------------------------------------------------------------------
49//
50
51#ifndef G4PairProductionRelModel_h
52#define G4PairProductionRelModel_h 1
53
54#include "G4VEmModel.hh"
55#include "G4PhysicsTable.hh"
56#include "G4NistManager.hh"
57
58class G4ParticleChangeForGamma;
59
60class G4PairProductionRelModel : public G4VEmModel
61{
62
63public:
64
65 G4PairProductionRelModel(const G4ParticleDefinition* p = 0,
66 const G4String& nam = "BetheHeitlerLPM");
67
68 virtual ~G4PairProductionRelModel();
69
70 virtual void Initialise(const G4ParticleDefinition*, const G4DataVector&);
71
72 virtual G4double ComputeCrossSectionPerAtom(
73 const G4ParticleDefinition*,
74 G4double kinEnergy,
75 G4double Z,
76 G4double A=0.,
77 G4double cut=0.,
78 G4double emax=DBL_MAX);
79
80 virtual void SampleSecondaries(std::vector<G4DynamicParticle*>*,
81 const G4MaterialCutsCouple*,
82 const G4DynamicParticle*,
83 G4double tmin,
84 G4double maxEnergy);
85
86 virtual void SetupForMaterial(const G4ParticleDefinition*,
87 const G4Material*,G4double);
88
89 // * fast inline functions *
90 inline void SetCurrentElement(G4double /*Z*/);
91
92 // set / get methods
93 inline void SetLPMconstant(G4double val);
94 inline G4double LPMconstant() const;
95
96 inline void SetLPMflag(G4bool);
97 inline G4bool LPMflag() const;
98
99protected:
100 // screening functions
101 inline G4double Phi1(G4double delta) const;
102 inline G4double Phi2(G4double delta) const;
103 inline G4double DeltaMax() const;
104 inline G4double DeltaMin(G4double) const;
105 // lpm functions
106 void CalcLPMFunctions(G4double k, G4double eplus);
107
108 // obsolete
109 G4double ScreenFunction1(G4double ScreenVariable);
110 G4double ScreenFunction2(G4double ScreenVariable);
111
112 G4double ComputeXSectionPerAtom(G4double totalEnergy, G4double Z);
113
114 G4double ComputeDXSectionPerAtom(G4double eplusEnergy, G4double totalEnergy, G4double Z);
115 G4double ComputeRelDXSectionPerAtom(G4double eplusEnergy, G4double totalEnergy, G4double Z);
116
117 // hide assignment operator
118 G4PairProductionRelModel & operator=(const G4PairProductionRelModel &right);
119 G4PairProductionRelModel(const G4PairProductionRelModel&);
120
121 G4NistManager* nist;
122
123 G4ParticleDefinition* theGamma;
124 G4ParticleDefinition* theElectron;
125 G4ParticleDefinition* thePositron;
126 G4ParticleChangeForGamma* fParticleChange;
127
128 G4double fLPMconstant;
129 G4bool fLPMflag;
130
131 // cash
132 G4double z13, z23, lnZ;
133 G4double Fel, Finel, fCoulomb;
134 G4double currentZ;
135
136 // LPM effect
137 G4double lpmEnergy;
138 G4double xiLPM, phiLPM, gLPM;
139
140 // consts
141 G4bool use_completescreening;
142
143 static const G4double xgi[8], wgi[8];
144 static const G4double Fel_light[5];
145 static const G4double Finel_light[5];
146 static const G4double facFel;
147 static const G4double facFinel;
148
149 static const G4double preS1, logTwo;
150
151};
152
153
154//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
155
156inline
157void G4PairProductionRelModel::SetLPMconstant(G4double val)
158{
159 fLPMconstant = val;
160}
161
162//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
163
164inline
165G4double G4PairProductionRelModel::LPMconstant() const
166{
167 return fLPMconstant;
168}
169
170//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
171
172inline
173void G4PairProductionRelModel::SetLPMflag(G4bool val)
174{
175 fLPMflag = val;
176}
177
178//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
179
180inline
181G4bool G4PairProductionRelModel::LPMflag() const
182{
183 return fLPMflag;
184}
185
186//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
187
188inline void G4PairProductionRelModel::SetCurrentElement(G4double Z)
189{
190 if(Z != currentZ) {
191 currentZ = Z;
192
193 G4int iz = G4int(Z);
194 z13 = nist->GetZ13(iz);
195 z23 = z13*z13;
196 lnZ = nist->GetLOGZ(iz);
197
198 if (iz <= 4) {
199 Fel = Fel_light[iz];
200 Finel = Finel_light[iz] ;
201 }
202 else {
203 Fel = facFel - lnZ/3. ;
204 Finel = facFinel - 2.*lnZ/3. ;
205 }
206 fCoulomb=GetCurrentElement()->GetfCoulomb();
207 }
208}
209
210//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
211
212inline G4double G4PairProductionRelModel::Phi1(G4double delta) const
213{
214 G4double screenVal;
215
216 if (delta > 1.)
217 screenVal = 21.12 - 4.184*std::log(delta+0.952);
218 else
219 screenVal = 20.868 - delta*(3.242 - 0.625*delta);
220
221 return screenVal;
222}
223
224//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
225
226inline G4double G4PairProductionRelModel::Phi2(G4double delta) const
227{
228 G4double screenVal;
229
230 if (delta > 1.)
231 screenVal = 21.12 - 4.184*std::log(delta+0.952);
232 else
233 screenVal = 20.209 - delta*(1.930 + 0.086*delta);
234
235 return screenVal;
236}
237
238inline G4double G4PairProductionRelModel::ScreenFunction1(G4double ScreenVariable)
239
240// compute the value of the screening function 3*PHI1 - PHI2
241
242{
243 G4double screenVal;
244
245 if (ScreenVariable > 1.)
246 screenVal = 42.24 - 8.368*std::log(ScreenVariable+0.952);
247 else
248 screenVal = 42.392 - ScreenVariable*(7.796 - 1.961*ScreenVariable);
249
250 return screenVal;
251}
252
253//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
254
255inline G4double G4PairProductionRelModel::ScreenFunction2(G4double ScreenVariable)
256
257// compute the value of the screening function 1.5*PHI1 + 0.5*PHI2
258
259{
260 G4double screenVal;
261
262 if (ScreenVariable > 1.)
263 screenVal = 42.24 - 8.368*std::log(ScreenVariable+0.952);
264 else
265 screenVal = 41.405 - ScreenVariable*(5.828 - 0.8945*ScreenVariable);
266
267 return screenVal;
268}
269
270//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
271
272
273inline G4double G4PairProductionRelModel::DeltaMax() const
274{
275 // k > 50 MeV
276 G4double FZ = 8.*(lnZ/3. + fCoulomb);
277 return std::exp( (42.24-FZ)/8.368 ) + 0.952;
278}
279
280inline G4double G4PairProductionRelModel::DeltaMin(G4double k) const
281{
282 return 4.*136./z13*(electron_mass_c2/k);
283}
284
285
286
287#endif
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