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