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25 // 25 //
26 // ------------------------------------------- 26 // --------------------------------------------------------------------
27 /// 27 ///
28 // 28 //
29 // 29 //
30 // ------------------------------------------- 30 // --------------------------------------------------------------
31 // 31 //
32 // Author: A. Forti 32 // Author: A. Forti
33 // Maria Grazia Pia (Maria.Grazia.Pia@ 33 // Maria Grazia Pia (Maria.Grazia.Pia@cern.ch)
34 // 34 //
35 // History: 35 // History:
36 // -------- 36 // --------
37 // 02/03/1999 A. Forti 1st implementation 37 // 02/03/1999 A. Forti 1st implementation
38 // 14.03.2000 Veronique Lefebure; 38 // 14.03.2000 Veronique Lefebure;
39 // Change initialisation of lowestEnergyLimit 39 // Change initialisation of lowestEnergyLimit from 1.22 to 1.022.
40 // Note that the hard coded value 1.022 should 40 // Note that the hard coded value 1.022 should be used instead of
41 // 2*electron_mass_c2 in order to agree with t 41 // 2*electron_mass_c2 in order to agree with the value of the data bank EPDL97
42 // 24.04.01 V.Ivanchenko remove RogueWave 42 // 24.04.01 V.Ivanchenko remove RogueWave
43 // 27.07.01 F.Longo correct bug in energy dist 43 // 27.07.01 F.Longo correct bug in energy distribution
44 // 21.01.03 V.Ivanchenko Cut per region 44 // 21.01.03 V.Ivanchenko Cut per region
45 // 25.03.03 F.Longo fix in angular distributio 45 // 25.03.03 F.Longo fix in angular distribution of e+/e-
46 // 24.04.03 V.Ivanchenko - Cut per region mfpt 46 // 24.04.03 V.Ivanchenko - Cut per region mfpt
47 // 47 //
48 // ------------------------------------------- 48 // --------------------------------------------------------------
49 49
50 #include "G4LowEnergyGammaConversion.hh" 50 #include "G4LowEnergyGammaConversion.hh"
51 51
52 #include "Randomize.hh" 52 #include "Randomize.hh"
53 #include "G4PhysicalConstants.hh" 53 #include "G4PhysicalConstants.hh"
54 #include "G4SystemOfUnits.hh" 54 #include "G4SystemOfUnits.hh"
55 #include "G4ParticleDefinition.hh" 55 #include "G4ParticleDefinition.hh"
56 #include "G4Track.hh" 56 #include "G4Track.hh"
57 #include "G4Step.hh" 57 #include "G4Step.hh"
58 #include "G4ForceCondition.hh" 58 #include "G4ForceCondition.hh"
59 #include "G4Gamma.hh" 59 #include "G4Gamma.hh"
60 #include "G4Electron.hh" 60 #include "G4Electron.hh"
61 #include "G4DynamicParticle.hh" 61 #include "G4DynamicParticle.hh"
62 #include "G4VParticleChange.hh" 62 #include "G4VParticleChange.hh"
63 #include "G4ThreeVector.hh" 63 #include "G4ThreeVector.hh"
64 #include "G4Positron.hh" 64 #include "G4Positron.hh"
65 #include "G4IonisParamElm.hh" 65 #include "G4IonisParamElm.hh"
66 #include "G4Material.hh" 66 #include "G4Material.hh"
67 #include "G4RDVCrossSectionHandler.hh" 67 #include "G4RDVCrossSectionHandler.hh"
68 #include "G4RDCrossSectionHandler.hh" 68 #include "G4RDCrossSectionHandler.hh"
69 #include "G4RDVEMDataSet.hh" 69 #include "G4RDVEMDataSet.hh"
70 #include "G4RDVDataSetAlgorithm.hh" 70 #include "G4RDVDataSetAlgorithm.hh"
71 #include "G4RDLogLogInterpolation.hh" 71 #include "G4RDLogLogInterpolation.hh"
72 #include "G4RDVRangeTest.hh" 72 #include "G4RDVRangeTest.hh"
73 #include "G4RDRangeTest.hh" 73 #include "G4RDRangeTest.hh"
74 #include "G4MaterialCutsCouple.hh" 74 #include "G4MaterialCutsCouple.hh"
75 75
76 G4LowEnergyGammaConversion::G4LowEnergyGammaCo 76 G4LowEnergyGammaConversion::G4LowEnergyGammaConversion(const G4String& processName)
77 : G4VDiscreteProcess(processName), 77 : G4VDiscreteProcess(processName),
78 lowEnergyLimit(1.022000*MeV), 78 lowEnergyLimit(1.022000*MeV),
79 highEnergyLimit(100*GeV), 79 highEnergyLimit(100*GeV),
80 intrinsicLowEnergyLimit(1.022000*MeV), 80 intrinsicLowEnergyLimit(1.022000*MeV),
81 intrinsicHighEnergyLimit(100*GeV), 81 intrinsicHighEnergyLimit(100*GeV),
82 smallEnergy(2.*MeV) 82 smallEnergy(2.*MeV)
83 83
84 { 84 {
85 if (lowEnergyLimit < intrinsicLowEnergyLimit 85 if (lowEnergyLimit < intrinsicLowEnergyLimit ||
86 highEnergyLimit > intrinsicHighEnergyLim 86 highEnergyLimit > intrinsicHighEnergyLimit)
87 { 87 {
88 G4Exception("G4LowEnergyGammaConversion: 88 G4Exception("G4LowEnergyGammaConversion::G4LowEnergyGammaConversion()",
89 "OutOfRange", FatalException 89 "OutOfRange", FatalException,
90 "Energy limit outside intrin 90 "Energy limit outside intrinsic process validity range!");
91 } 91 }
92 92
93 // The following pointer is owned by G4DataH 93 // The following pointer is owned by G4DataHandler
94 94
95 crossSectionHandler = new G4RDCrossSectionHa 95 crossSectionHandler = new G4RDCrossSectionHandler();
96 crossSectionHandler->Initialise(0,1.0220*MeV 96 crossSectionHandler->Initialise(0,1.0220*MeV,100.*GeV,400);
97 meanFreePathTable = 0; 97 meanFreePathTable = 0;
98 rangeTest = new G4RDRangeTest; 98 rangeTest = new G4RDRangeTest;
99 99
100 if (verboseLevel > 0) 100 if (verboseLevel > 0)
101 { 101 {
102 G4cout << GetProcessName() << " is crea 102 G4cout << GetProcessName() << " is created " << G4endl
103 << "Energy range: " 103 << "Energy range: "
104 << lowEnergyLimit / MeV << " MeV - " 104 << lowEnergyLimit / MeV << " MeV - "
105 << highEnergyLimit / GeV << " GeV" 105 << highEnergyLimit / GeV << " GeV"
106 << G4endl; 106 << G4endl;
107 } 107 }
108 } 108 }
109 109
110 G4LowEnergyGammaConversion::~G4LowEnergyGammaC 110 G4LowEnergyGammaConversion::~G4LowEnergyGammaConversion()
111 { 111 {
112 delete meanFreePathTable; 112 delete meanFreePathTable;
113 delete crossSectionHandler; 113 delete crossSectionHandler;
114 delete rangeTest; 114 delete rangeTest;
115 } 115 }
116 116
117 void G4LowEnergyGammaConversion::BuildPhysicsT 117 void G4LowEnergyGammaConversion::BuildPhysicsTable(const G4ParticleDefinition& )
118 { 118 {
119 119
120 crossSectionHandler->Clear(); 120 crossSectionHandler->Clear();
121 G4String crossSectionFile = "pair/pp-cs-"; 121 G4String crossSectionFile = "pair/pp-cs-";
122 crossSectionHandler->LoadData(crossSectionFi 122 crossSectionHandler->LoadData(crossSectionFile);
123 123
124 delete meanFreePathTable; 124 delete meanFreePathTable;
125 meanFreePathTable = crossSectionHandler->Bui 125 meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
126 } 126 }
127 127
128 G4VParticleChange* G4LowEnergyGammaConversion: 128 G4VParticleChange* G4LowEnergyGammaConversion::PostStepDoIt(const G4Track& aTrack,
129 const G4Step& aStep) 129 const G4Step& aStep)
130 { 130 {
131 // The energies of the e+ e- secondaries are s 131 // The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
132 // cross sections with Coulomb correction. A m 132 // cross sections with Coulomb correction. A modified version of the random
133 // number techniques of Butcher & Messel is us 133 // number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).
134 134
135 // Note 1 : Effects due to the breakdown of th 135 // Note 1 : Effects due to the breakdown of the Born approximation at low
136 // energy are ignored. 136 // energy are ignored.
137 // Note 2 : The differential cross section imp 137 // Note 2 : The differential cross section implicitly takes account of
138 // pair creation in both nuclear and atomic el 138 // pair creation in both nuclear and atomic electron fields. However triplet
139 // prodution is not generated. 139 // prodution is not generated.
140 140
141 aParticleChange.Initialize(aTrack); 141 aParticleChange.Initialize(aTrack);
142 142
143 const G4MaterialCutsCouple* couple = aTrack. 143 const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
144 144
145 const G4DynamicParticle* incidentPhoton = aT 145 const G4DynamicParticle* incidentPhoton = aTrack.GetDynamicParticle();
146 G4double photonEnergy = incidentPhoton->GetK 146 G4double photonEnergy = incidentPhoton->GetKineticEnergy();
147 G4ParticleMomentum photonDirection = inciden 147 G4ParticleMomentum photonDirection = incidentPhoton->GetMomentumDirection();
148 148
149 G4double epsilon ; 149 G4double epsilon ;
150 G4double epsilon0 = electron_mass_c2 / photo 150 G4double epsilon0 = electron_mass_c2 / photonEnergy ;
151 151
152 // Do it fast if photon energy < 2. MeV 152 // Do it fast if photon energy < 2. MeV
153 if (photonEnergy < smallEnergy ) 153 if (photonEnergy < smallEnergy )
154 { 154 {
155 epsilon = epsilon0 + (0.5 - epsilon0) * 155 epsilon = epsilon0 + (0.5 - epsilon0) * G4UniformRand();
156 } 156 }
157 else 157 else
158 { 158 {
159 // Select randomly one element in the cu 159 // Select randomly one element in the current material
160 const G4Element* element = crossSectionH 160 const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);
161 161
162 if (element == 0) 162 if (element == 0)
163 { 163 {
164 G4cout << "G4LowEnergyGammaConversion::Pos 164 G4cout << "G4LowEnergyGammaConversion::PostStepDoIt - element = 0" << G4endl;
165 } 165 }
166 G4IonisParamElm* ionisation = element->G 166 G4IonisParamElm* ionisation = element->GetIonisation();
167 if (ionisation == 0) 167 if (ionisation == 0)
168 { 168 {
169 G4cout << "G4LowEnergyGammaConversion::Pos 169 G4cout << "G4LowEnergyGammaConversion::PostStepDoIt - ionisation = 0" << G4endl;
170 } 170 }
171 171
172 // Extract Coulomb factor for this Eleme 172 // Extract Coulomb factor for this Element
173 G4double fZ = 8. * (ionisation->GetlogZ3 173 G4double fZ = 8. * (ionisation->GetlogZ3());
174 if (photonEnergy > 50. * MeV) fZ += 8. * 174 if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());
175 175
176 // Limits of the screening variable 176 // Limits of the screening variable
177 G4double screenFactor = 136. * epsilon0 177 G4double screenFactor = 136. * epsilon0 / (element->GetIonisation()->GetZ3()) ;
178 G4double screenMax = std::exp ((42.24 - 178 G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
179 G4double screenMin = std::min(4.*screenF 179 G4double screenMin = std::min(4.*screenFactor,screenMax) ;
180 180
181 // Limits of the energy sampling 181 // Limits of the energy sampling
182 G4double epsilon1 = 0.5 - 0.5 * std::sqr 182 G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
183 G4double epsilonMin = std::max(epsilon0, 183 G4double epsilonMin = std::max(epsilon0,epsilon1);
184 G4double epsilonRange = 0.5 - epsilonMin 184 G4double epsilonRange = 0.5 - epsilonMin ;
185 185
186 // Sample the energy rate of the created 186 // Sample the energy rate of the created electron (or positron)
187 G4double screen; 187 G4double screen;
188 G4double gReject ; 188 G4double gReject ;
189 189
190 G4double f10 = ScreenFunction1(screenMin 190 G4double f10 = ScreenFunction1(screenMin) - fZ;
191 G4double f20 = ScreenFunction2(screenMin 191 G4double f20 = ScreenFunction2(screenMin) - fZ;
192 G4double normF1 = std::max(f10 * epsilon 192 G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
193 G4double normF2 = std::max(1.5 * f20,0.) 193 G4double normF2 = std::max(1.5 * f20,0.);
194 194
195 do { 195 do {
196 if (normF1 / (normF1 + normF2) > G4UniformRa 196 if (normF1 / (normF1 + normF2) > G4UniformRand() )
197 { 197 {
198 epsilon = 0.5 - epsilonRange * std::pow( 198 epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ;
199 screen = screenFactor / (epsilon * (1. - 199 screen = screenFactor / (epsilon * (1. - epsilon));
200 gReject = (ScreenFunction1(screen) - fZ) 200 gReject = (ScreenFunction1(screen) - fZ) / f10 ;
201 } 201 }
202 else 202 else
203 { 203 {
204 epsilon = epsilonMin + epsilonRange * G4 204 epsilon = epsilonMin + epsilonRange * G4UniformRand();
205 screen = screenFactor / (epsilon * (1 - 205 screen = screenFactor / (epsilon * (1 - epsilon));
206 gReject = (ScreenFunction2(screen) - fZ) 206 gReject = (ScreenFunction2(screen) - fZ) / f20 ;
207 } 207 }
208 } while ( gReject < G4UniformRand() ); 208 } while ( gReject < G4UniformRand() );
209 209
210 } // End of epsilon sampling 210 } // End of epsilon sampling
211 211
212 // Fix charges randomly 212 // Fix charges randomly
213 213
214 G4double electronTotEnergy; 214 G4double electronTotEnergy;
215 G4double positronTotEnergy; 215 G4double positronTotEnergy;
216 216
217 if (CLHEP::RandBit::shootBit()) 217 if (CLHEP::RandBit::shootBit())
218 { 218 {
219 electronTotEnergy = (1. - epsilon) * pho 219 electronTotEnergy = (1. - epsilon) * photonEnergy;
220 positronTotEnergy = epsilon * photonEner 220 positronTotEnergy = epsilon * photonEnergy;
221 } 221 }
222 else 222 else
223 { 223 {
224 positronTotEnergy = (1. - epsilon) * pho 224 positronTotEnergy = (1. - epsilon) * photonEnergy;
225 electronTotEnergy = epsilon * photonEner 225 electronTotEnergy = epsilon * photonEnergy;
226 } 226 }
227 227
228 // Scattered electron (positron) angles. ( Z 228 // Scattered electron (positron) angles. ( Z - axis along the parent photon)
229 // Universal distribution suggested by L. Ur 229 // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
230 // derived from Tsai distribution (Rev. Mod. 230 // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)
231 231
232 G4double u; 232 G4double u;
233 const G4double a1 = 0.625; 233 const G4double a1 = 0.625;
234 G4double a2 = 3. * a1; 234 G4double a2 = 3. * a1;
235 // G4double d = 27. ; 235 // G4double d = 27. ;
236 236
237 // if (9. / (9. + d) > G4UniformRand()) 237 // if (9. / (9. + d) > G4UniformRand())
238 if (0.25 > G4UniformRand()) 238 if (0.25 > G4UniformRand())
239 { 239 {
240 u = - std::log(G4UniformRand() * G4Unifo 240 u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
241 } 241 }
242 else 242 else
243 { 243 {
244 u = - std::log(G4UniformRand() * G4Unifo 244 u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
245 } 245 }
246 246
247 G4double thetaEle = u*electron_mass_c2/elect 247 G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
248 G4double thetaPos = u*electron_mass_c2/posit 248 G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
249 G4double phi = twopi * G4UniformRand(); 249 G4double phi = twopi * G4UniformRand();
250 250
251 G4double dxEle= std::sin(thetaEle)*std::cos( 251 G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
252 G4double dxPos=-std::sin(thetaPos)*std::cos( 252 G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
253 253
254 254
255 // Kinematics of the created pair: 255 // Kinematics of the created pair:
256 // the electron and positron are assumed to 256 // the electron and positron are assumed to have a symetric angular
257 // distribution with respect to the Z axis a 257 // distribution with respect to the Z axis along the parent photon
258 258
259 G4double localEnergyDeposit = 0. ; 259 G4double localEnergyDeposit = 0. ;
260 260
261 aParticleChange.SetNumberOfSecondaries(2) ; 261 aParticleChange.SetNumberOfSecondaries(2) ;
262 G4double electronKineEnergy = std::max(0.,el 262 G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
263 263
264 // Generate the electron only if with large 264 // Generate the electron only if with large enough range w.r.t. cuts and safety
265 265
266 G4double safety = aStep.GetPostStepPoint()-> 266 G4double safety = aStep.GetPostStepPoint()->GetSafety();
267 267
268 if (rangeTest->Escape(G4Electron::Electron() 268 if (rangeTest->Escape(G4Electron::Electron(),couple,electronKineEnergy,safety))
269 { 269 {
270 G4ThreeVector electronDirection (dxEle, 270 G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
271 electronDirection.rotateUz(photonDirecti 271 electronDirection.rotateUz(photonDirection);
272 272
273 G4DynamicParticle* particle1 = new G4Dyn 273 G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
274 electronDirection, 274 electronDirection,
275 electronKineEnergy); 275 electronKineEnergy);
276 aParticleChange.AddSecondary(particle1) 276 aParticleChange.AddSecondary(particle1) ;
277 } 277 }
278 else 278 else
279 { 279 {
280 localEnergyDeposit += electronKineEnergy 280 localEnergyDeposit += electronKineEnergy ;
281 } 281 }
282 282
283 // The e+ is always created (even with kinet 283 // The e+ is always created (even with kinetic energy = 0) for further annihilation
284 G4double positronKineEnergy = std::max(0.,po 284 G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
285 285
286 // Is the local energy deposit correct, if t 286 // Is the local energy deposit correct, if the positron is always created?
287 if (! (rangeTest->Escape(G4Positron::Positro 287 if (! (rangeTest->Escape(G4Positron::Positron(),couple,positronKineEnergy,safety)))
288 { 288 {
289 localEnergyDeposit += positronKineEnergy 289 localEnergyDeposit += positronKineEnergy ;
290 positronKineEnergy = 0. ; 290 positronKineEnergy = 0. ;
291 } 291 }
292 292
293 G4ThreeVector positronDirection (dxPos, dyPo 293 G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
294 positronDirection.rotateUz(photonDirection); 294 positronDirection.rotateUz(photonDirection);
295 295
296 // Create G4DynamicParticle object for the p 296 // Create G4DynamicParticle object for the particle2
297 G4DynamicParticle* particle2 = new G4Dynamic 297 G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
298 positronDirection, positron 298 positronDirection, positronKineEnergy);
299 aParticleChange.AddSecondary(particle2) ; 299 aParticleChange.AddSecondary(particle2) ;
300 300
301 aParticleChange.ProposeLocalEnergyDeposit(lo 301 aParticleChange.ProposeLocalEnergyDeposit(localEnergyDeposit) ;
302 302
303 // Kill the incident photon 303 // Kill the incident photon
304 aParticleChange.ProposeMomentumDirection(0., 304 aParticleChange.ProposeMomentumDirection(0.,0.,0.) ;
305 aParticleChange.ProposeEnergy(0.) ; 305 aParticleChange.ProposeEnergy(0.) ;
306 aParticleChange.ProposeTrackStatus(fStopAndK 306 aParticleChange.ProposeTrackStatus(fStopAndKill) ;
307 307
308 // Reset NbOfInteractionLengthLeft and retu 308 // Reset NbOfInteractionLengthLeft and return aParticleChange
309 return G4VDiscreteProcess::PostStepDoIt(aTra 309 return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
310 } 310 }
311 311
312 G4bool G4LowEnergyGammaConversion::IsApplicabl 312 G4bool G4LowEnergyGammaConversion::IsApplicable(const G4ParticleDefinition& particle)
313 { 313 {
314 return ( &particle == G4Gamma::Gamma() ); 314 return ( &particle == G4Gamma::Gamma() );
315 } 315 }
316 316
317 G4double G4LowEnergyGammaConversion::GetMeanFr 317 G4double G4LowEnergyGammaConversion::GetMeanFreePath(const G4Track& track,
318 G4double, // previousStepSize 318 G4double, // previousStepSize
319 G4ForceCondition*) 319 G4ForceCondition*)
320 { 320 {
321 const G4DynamicParticle* photon = track.GetD 321 const G4DynamicParticle* photon = track.GetDynamicParticle();
322 G4double energy = photon->GetKineticEnergy() 322 G4double energy = photon->GetKineticEnergy();
323 const G4MaterialCutsCouple* couple = track.G 323 const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
324 size_t materialIndex = couple->GetIndex(); 324 size_t materialIndex = couple->GetIndex();
325 325
326 G4double meanFreePath; 326 G4double meanFreePath;
327 if (energy > highEnergyLimit) meanFreePath = 327 if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
328 else if (energy < lowEnergyLimit) meanFreePa 328 else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
329 else meanFreePath = meanFreePathTable->FindV 329 else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
330 return meanFreePath; 330 return meanFreePath;
331 } 331 }
332 332
333 G4double G4LowEnergyGammaConversion::ScreenFun 333 G4double G4LowEnergyGammaConversion::ScreenFunction1(G4double screenVariable)
334 { 334 {
335 // Compute the value of the screening functi 335 // Compute the value of the screening function 3*phi1 - phi2
336 336
337 G4double value; 337 G4double value;
338 338
339 if (screenVariable > 1.) 339 if (screenVariable > 1.)
340 value = 42.24 - 8.368 * std::log(screenVar 340 value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
341 else 341 else
342 value = 42.392 - screenVariable * (7.796 - 342 value = 42.392 - screenVariable * (7.796 - 1.961 * screenVariable);
343 343
344 return value; 344 return value;
345 } 345 }
346 346
347 G4double G4LowEnergyGammaConversion::ScreenFun 347 G4double G4LowEnergyGammaConversion::ScreenFunction2(G4double screenVariable)
348 { 348 {
349 // Compute the value of the screening functi 349 // Compute the value of the screening function 1.5*phi1 - 0.5*phi2
350 350
351 G4double value; 351 G4double value;
352 352
353 if (screenVariable > 1.) 353 if (screenVariable > 1.)
354 value = 42.24 - 8.368 * std::log(screenVar 354 value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
355 else 355 else
356 value = 41.405 - screenVariable * (5.828 - 356 value = 41.405 - screenVariable * (5.828 - 0.8945 * screenVariable);
357 357
358 return value; 358 return value;
359 } 359 }
360 360