1 | // |
---|
2 | // ******************************************************************** |
---|
3 | // * License and Disclaimer * |
---|
4 | // * * |
---|
5 | // * The Geant4 software is copyright of the Copyright Holders of * |
---|
6 | // * the Geant4 Collaboration. It is provided under the terms and * |
---|
7 | // * conditions of the Geant4 Software License, included in the file * |
---|
8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
---|
9 | // * include a list of copyright holders. * |
---|
10 | // * * |
---|
11 | // * Neither the authors of this software system, nor their employing * |
---|
12 | // * institutes,nor the agencies providing financial support for this * |
---|
13 | // * work make any representation or warranty, express or implied, * |
---|
14 | // * regarding this software system or assume any liability for its * |
---|
15 | // * use. Please see the license in the file LICENSE and URL above * |
---|
16 | // * for the full disclaimer and the limitation of liability. * |
---|
17 | // * * |
---|
18 | // * This code implementation is the result of the scientific and * |
---|
19 | // * technical work of the GEANT4 collaboration. * |
---|
20 | // * By using, copying, modifying or distributing the software (or * |
---|
21 | // * any work based on the software) you agree to acknowledge its * |
---|
22 | // * use in resulting scientific publications, and indicate your * |
---|
23 | // * acceptance of all terms of the Geant4 Software license. * |
---|
24 | // ******************************************************************** |
---|
25 | // |
---|
26 | // |
---|
27 | // $Id: G4MuonNucleusInteractionModel.cc,v 1.6 2006/06/29 20:57:36 gunter Exp $ |
---|
28 | // GEANT4 tag $Name: geant4-09-04-beta-01 $ |
---|
29 | // |
---|
30 | // -------------------------------------------------------------- |
---|
31 | // G4MuonNucleusInteractionModel.cc |
---|
32 | // |
---|
33 | // M.Takahata (Makoto.Takahata@cern.ch) |
---|
34 | |
---|
35 | #include "G4MuonNucleusInteractionModel.hh" |
---|
36 | |
---|
37 | |
---|
38 | //----------------------------------------------------------------------------- |
---|
39 | G4MuonNucleusInteractionModel::G4MuonNucleusInteractionModel() |
---|
40 | : G4LeptonHadronInteractionModel() |
---|
41 | //----------------------------------------------------------------------------- |
---|
42 | { |
---|
43 | // build the physics vector |
---|
44 | Nbin = 90; |
---|
45 | kEmin = 1.0e-5*GeV; |
---|
46 | kEmax = 1.0e+4*GeV; |
---|
47 | cascadeModelMarginalEnergy = 25.0*GeV; |
---|
48 | theCoefficientVector = new G4PhysicsLogVector(kEmin, kEmax, Nbin); |
---|
49 | makePhysicsVector(); |
---|
50 | |
---|
51 | // construct variables |
---|
52 | LEPionMinusInelastic = new G4LEPionMinusInelastic; |
---|
53 | LEPionPlusInelastic = new G4LEPionPlusInelastic; |
---|
54 | HEPionMinusInelastic = new G4HEPionMinusInelastic; |
---|
55 | HEPionPlusInelastic = new G4HEPionPlusInelastic; |
---|
56 | } |
---|
57 | |
---|
58 | |
---|
59 | //----------------------------------------------------------------------------- |
---|
60 | G4MuonNucleusInteractionModel::~G4MuonNucleusInteractionModel() |
---|
61 | //----------------------------------------------------------------------------- |
---|
62 | { |
---|
63 | delete LEPionMinusInelastic; |
---|
64 | delete LEPionPlusInelastic; |
---|
65 | delete HEPionMinusInelastic; |
---|
66 | delete HEPionPlusInelastic; |
---|
67 | |
---|
68 | delete theCoefficientVector; |
---|
69 | } |
---|
70 | |
---|
71 | |
---|
72 | //----------------------------------------------------------------------------- |
---|
73 | G4double G4MuonNucleusInteractionModel::tetal[35] = { |
---|
74 | //----------------------------------------------------------------------------- |
---|
75 | 1.0000000, 0.9999995, 0.9999990, 0.9999981, 0.9999962, |
---|
76 | 0.9999943, 0.9999905, 0.9999847, 0.9999752, 0.9999599, |
---|
77 | 0.9999352, 0.9998951, 0.9998302, 0.9997253, 0.9995556, |
---|
78 | 0.9992810, 0.9988368, 0.9981183, 0.9969561, 0.9950773, |
---|
79 | 0.9920409, 0.9871377, 0.9792297, 0.9665010, 0.9460785, |
---|
80 | 0.9134827, 0.8618938, 0.7813507, 0.6583430, 0.4770452, |
---|
81 | 0.2247237, -0.0955139, -0.4461272, -0.7495149, -0.9900000 |
---|
82 | }; |
---|
83 | |
---|
84 | |
---|
85 | //----------------------------------------------------------------------------- |
---|
86 | G4double G4MuonNucleusInteractionModel::xeml[23] = { |
---|
87 | //----------------------------------------------------------------------------- |
---|
88 | 1.000, 0.998, 0.997, 0.996, 0.995, 0.994, 0.992, 0.990, |
---|
89 | 0.970, 0.950, 0.920, 0.890, 0.850, 0.800, 0.750, 0.700, |
---|
90 | 0.600, 0.500, 0.400, 0.300, 0.200, 0.100, 0.050 |
---|
91 | }; |
---|
92 | |
---|
93 | |
---|
94 | //----------------------------------------------------------------------------- |
---|
95 | G4double G4MuonNucleusInteractionModel::computeMicroscopicCrossSection |
---|
96 | (const G4Track &muonTrack) |
---|
97 | //----------------------------------------------------------------------------- |
---|
98 | { |
---|
99 | const G4DynamicParticle *muonDynamics = muonTrack.GetDynamicParticle(); |
---|
100 | G4double kineticEnergy = muonDynamics->GetKineticEnergy(); |
---|
101 | G4double muonMass = muonDynamics->GetDefinition()->GetPDGMass(); |
---|
102 | |
---|
103 | G4double totalEnergy = kineticEnergy + muonMass; |
---|
104 | |
---|
105 | G4double microscopicCrossSection; |
---|
106 | if(totalEnergy <= 30.0*GeV) { |
---|
107 | microscopicCrossSection |
---|
108 | = 0.0003*millibarn; |
---|
109 | } else { |
---|
110 | microscopicCrossSection |
---|
111 | = 0.0003*std::pow((totalEnergy/(30.0*GeV)), 0.25)*millibarn; |
---|
112 | } |
---|
113 | |
---|
114 | return microscopicCrossSection; |
---|
115 | } |
---|
116 | |
---|
117 | |
---|
118 | //----------------------------------------------------------------------------- |
---|
119 | void G4MuonNucleusInteractionModel::makePhysicsVector() |
---|
120 | //----------------------------------------------------------------------------- |
---|
121 | { |
---|
122 | G4double Ei, Ef; // initial and final energy of incident muon; |
---|
123 | G4double muonMass = G4MuonMinus::MuonMinus()->GetPDGMass(); |
---|
124 | |
---|
125 | for (G4int i=0; i<=(Nbin-1); i++) |
---|
126 | { |
---|
127 | G4double totalCrossSection = 0.0; |
---|
128 | Ei = theCoefficientVector->GetLowEdgeEnergy(i) + muonMass; |
---|
129 | for (G4int j=1; j<=34; j++) |
---|
130 | { |
---|
131 | cosTheta = 0.5 * (tetal[j] + tetal[j-1]); |
---|
132 | for (G4int k=1; k<=22; k++) |
---|
133 | { |
---|
134 | Ef = 0.5 * Ei * (xeml[k]+xeml[k-1]); |
---|
135 | G4double dsigma = computeDifferentialCrossSection(Ei,Ef,cosTheta); |
---|
136 | totalCrossSection = totalCrossSection |
---|
137 | + Ei * (tetal[j-1]-tetal[j])*(xeml[k-1]-xeml[k]) * dsigma; |
---|
138 | } |
---|
139 | } |
---|
140 | theCoefficientVector->PutValue(i, totalCrossSection); |
---|
141 | } |
---|
142 | } |
---|
143 | |
---|
144 | |
---|
145 | //----------------------------------------------------------------------------- |
---|
146 | G4VParticleChange* G4MuonNucleusInteractionModel::applyInteractionModel |
---|
147 | (const G4Track &muonTrack, G4Nucleus &targetNucleus ) |
---|
148 | //----------------------------------------------------------------------------- |
---|
149 | { |
---|
150 | G4int icos=0, ie1=0; |
---|
151 | G4double E1=0., P1=0.; |
---|
152 | G4double rndm[3]; |
---|
153 | G4bool isOutRange; |
---|
154 | |
---|
155 | // Initialization |
---|
156 | aParticleChange.Initialize(muonTrack); |
---|
157 | |
---|
158 | const G4DynamicParticle *muonDynamics = muonTrack.GetDynamicParticle(); |
---|
159 | G4double kineticEnergy = muonDynamics->GetKineticEnergy(); |
---|
160 | G4double totalMomentum = muonDynamics->GetTotalMomentum(); |
---|
161 | G4double totalEnergy = muonDynamics->GetTotalEnergy(); |
---|
162 | G4double muonMass = muonDynamics->GetDefinition()->GetPDGMass(); |
---|
163 | |
---|
164 | |
---|
165 | G4double W2 = 0.0; G4int W2try = 0; |
---|
166 | while (W2 <= 0.0) |
---|
167 | { |
---|
168 | G4double totalCrossSection = 0.0; |
---|
169 | G4bool interpolated = false; |
---|
170 | G4double fRndm = G4UniformRand(); |
---|
171 | G4double Hmax |
---|
172 | = theCoefficientVector->GetValue(kineticEnergy, isOutRange); |
---|
173 | for (G4int i=1; i<=34; i++) |
---|
174 | { |
---|
175 | cosTheta = 0.5 * (tetal[i] + tetal[i-1]); |
---|
176 | for (G4int j=1; j<=22; j++) |
---|
177 | { |
---|
178 | E1 = 0.5 * totalEnergy * (xeml[j]+xeml[j-1]); |
---|
179 | G4double dsigma |
---|
180 | = computeDifferentialCrossSection(totalEnergy, E1, cosTheta); |
---|
181 | totalCrossSection = totalCrossSection |
---|
182 | + totalEnergy*(tetal[i-1]-tetal[i])*(xeml[j-1]-xeml[j])*dsigma; |
---|
183 | |
---|
184 | if((fRndm*Hmax)<totalCrossSection) { |
---|
185 | interpolated = true; |
---|
186 | icos = i; ie1 = j; |
---|
187 | break; |
---|
188 | } |
---|
189 | } |
---|
190 | |
---|
191 | if(interpolated) { |
---|
192 | // calculate energy, momentum and angle of outgoing muon |
---|
193 | CLHEP::RandFlat::shootArray(3, rndm); |
---|
194 | G4double theta = std::acos(tetal[icos-1]) |
---|
195 | + rndm[0]*(std::acos(tetal[icos])-std::acos(tetal[icos-1])); |
---|
196 | cosTheta = std::cos(theta); |
---|
197 | E1 = (xeml[ie1] + rndm[1]*(xeml[ie1-1]-xeml[ie1])) * totalEnergy; |
---|
198 | if(E1<muonMass) E1 = muonMass + 0.0001*GeV; |
---|
199 | P1 = std::sqrt(std::abs(E1*E1-muonMass*muonMass)); |
---|
200 | |
---|
201 | // invariant mass of final hadron state must be greater than zero |
---|
202 | W2 = proton_mass_c2*proton_mass_c2 |
---|
203 | +2.0*proton_mass_c2*(totalEnergy-E1) |
---|
204 | -2.0*(totalEnergy*E1-totalMomentum*P1*cosTheta-muonMass*muonMass); |
---|
205 | |
---|
206 | break; |
---|
207 | } |
---|
208 | } |
---|
209 | |
---|
210 | W2try++; |
---|
211 | if (W2try>100) return &aParticleChange; |
---|
212 | } |
---|
213 | |
---|
214 | // calculate momentum of outgoing muon / pion(photon) |
---|
215 | G4double sinTheta = std::sqrt(std::abs(1.0 - cosTheta*cosTheta)); |
---|
216 | G4double phi = rndm[2]*twopi; |
---|
217 | G4ThreeVector muonDirection(sinTheta*std::cos(phi),sinTheta*std::sin(phi),cosTheta); |
---|
218 | G4ThreeVector muonDirectionInit = muonTrack.GetMomentumDirection(); |
---|
219 | muonDirection.rotateUz(muonDirectionInit); |
---|
220 | |
---|
221 | G4ParticleMomentum pionMomentum |
---|
222 | = muonDynamics->GetMomentum() - P1*muonDirection; |
---|
223 | G4double muonKineticEnergy |
---|
224 | = std::sqrt(P1*P1 + muonMass*muonMass) - muonMass; |
---|
225 | aParticleChange.ProposeMomentumDirection(muonDirection); |
---|
226 | aParticleChange.ProposeEnergy(muonKineticEnergy); |
---|
227 | aParticleChange.ProposeTrackStatus(fAlive); |
---|
228 | |
---|
229 | |
---|
230 | // virtual photon is exchanged with a pion of same Q2 |
---|
231 | // select pi+/pi- randomly and generate pion track |
---|
232 | G4ParticleDefinition* pdPion; |
---|
233 | if(CLHEP::RandBit::shootBit()) |
---|
234 | pdPion = G4PionMinus::PionMinusDefinition(); |
---|
235 | else |
---|
236 | pdPion = G4PionPlus::PionPlusDefinition(); |
---|
237 | |
---|
238 | G4DynamicParticle* pionDynamics |
---|
239 | = new G4DynamicParticle(pdPion, pionMomentum); |
---|
240 | |
---|
241 | G4Track* pionTrack = new G4Track(pionDynamics, |
---|
242 | muonTrack.GetGlobalTime(), |
---|
243 | muonTrack.GetPosition() ); |
---|
244 | pionTrack->SetStep(muonTrack.GetStep()); |
---|
245 | |
---|
246 | // Invoke pion-nucleus inelastic process |
---|
247 | invokePionNucleus(*pionTrack, targetNucleus); |
---|
248 | |
---|
249 | // Termination |
---|
250 | delete pionTrack; |
---|
251 | |
---|
252 | return &aParticleChange; |
---|
253 | } |
---|
254 | |
---|
255 | |
---|
256 | //----------------------------------------------------------------------------- |
---|
257 | void G4MuonNucleusInteractionModel::invokePionNucleus |
---|
258 | (const G4Track &pionTrack, G4Nucleus &targetNucleus ) |
---|
259 | //----------------------------------------------------------------------------- |
---|
260 | { |
---|
261 | // force interaction of pion with target nucleus |
---|
262 | G4double pionKineticEnergy = pionTrack.GetKineticEnergy(); |
---|
263 | if(pionTrack.GetDefinition()->GetParticleName() == "pi-") { |
---|
264 | if(pionKineticEnergy <= cascadeModelMarginalEnergy) |
---|
265 | pionChange |
---|
266 | = LEPionMinusInelastic->ApplyYourself(pionTrack, targetNucleus); |
---|
267 | else |
---|
268 | pionChange |
---|
269 | = HEPionMinusInelastic->ApplyYourself(pionTrack, targetNucleus); |
---|
270 | } else if(pionTrack.GetDefinition()->GetParticleName() == "pi+") { |
---|
271 | if(pionKineticEnergy <= cascadeModelMarginalEnergy) |
---|
272 | pionChange |
---|
273 | = LEPionPlusInelastic->ApplyYourself(pionTrack, targetNucleus); |
---|
274 | else |
---|
275 | pionChange |
---|
276 | = HEPionPlusInelastic->ApplyYourself(pionTrack, targetNucleus); |
---|
277 | } |
---|
278 | |
---|
279 | |
---|
280 | // add local energy deposit |
---|
281 | G4double localEnergyDeposited = 0.0; |
---|
282 | localEnergyDeposited = pionChange->GetLocalEnergyDeposit(); |
---|
283 | aParticleChange.ProposeLocalEnergyDeposit(localEnergyDeposited); |
---|
284 | |
---|
285 | |
---|
286 | // register secondary particles |
---|
287 | G4int numSecondaries = pionChange->GetNumberOfSecondaries(); |
---|
288 | aParticleChange.SetNumberOfSecondaries(numSecondaries); |
---|
289 | |
---|
290 | G4ParticleMomentum secondaryMomentum = G4ThreeVector(0.,0.,0.); |
---|
291 | for(G4int iS=0; iS<=(numSecondaries-1); iS++) { |
---|
292 | secondaryMomentum |
---|
293 | = secondaryMomentum + pionChange->GetSecondary(iS)->GetParticle()->GetMomentum(); |
---|
294 | aParticleChange.AddSecondary(pionChange->GetSecondary(iS)->GetParticle()); |
---|
295 | } |
---|
296 | pionChange->Clear(); |
---|
297 | |
---|
298 | return; |
---|
299 | } |
---|
300 | |
---|
301 | |
---|
302 | //----------------------------------------------------------------------------- |
---|
303 | G4double G4MuonNucleusInteractionModel::computeDifferentialCrossSection |
---|
304 | (G4double initialEnergy, G4double finalEnergy, G4double aCosTheta) |
---|
305 | //----------------------------------------------------------------------------- |
---|
306 | { |
---|
307 | G4double muonMass = G4MuonMinus::MuonMinus()->GetPDGMass(); |
---|
308 | |
---|
309 | if(finalEnergy < muonMass) return(0.0); |
---|
310 | if(aCosTheta >= 1.0) return DBL_MAX; |
---|
311 | |
---|
312 | G4double initialMomentum |
---|
313 | = std::sqrt(initialEnergy*initialEnergy - muonMass*muonMass); |
---|
314 | G4double finalMomentum |
---|
315 | = std::sqrt(finalEnergy*finalEnergy - muonMass*muonMass); |
---|
316 | |
---|
317 | |
---|
318 | // calculate momentum transfer (Q2) |
---|
319 | // and invariant mass of final state of hadrons (W2) |
---|
320 | G4double Q2 |
---|
321 | = 2.0*(initialEnergy*finalEnergy |
---|
322 | -initialMomentum*finalMomentum*aCosTheta-muonMass*muonMass); |
---|
323 | if(Q2 < 0.0) return(0.0); |
---|
324 | |
---|
325 | G4double W2 |
---|
326 | = proton_mass_c2*proton_mass_c2 |
---|
327 | +2.0*proton_mass_c2*(initialEnergy-finalEnergy)-Q2; |
---|
328 | if(W2 < 0.0) return(0.0); |
---|
329 | |
---|
330 | |
---|
331 | // calculate factors |
---|
332 | // Nu : energy transfer |
---|
333 | // K : incident flux of photon |
---|
334 | // Epsilon : virtual photon polarization |
---|
335 | G4double fNu = initialEnergy-finalEnergy; |
---|
336 | G4double fK = fNu+Q2/(2.0*fNu); |
---|
337 | G4double fEpsilon |
---|
338 | = 1.0/(1.0+2.0*((1.0-aCosTheta)/(1.0+aCosTheta))*(Q2+fNu*fNu)/Q2); |
---|
339 | if(fEpsilon > 1.0) return DBL_MAX; |
---|
340 | |
---|
341 | |
---|
342 | // calculate photoabsorption cross sections |
---|
343 | // fGamma : flux of transverse photons |
---|
344 | // sigma_t : for transverse photons |
---|
345 | // sigma_l : for longitudinal photons |
---|
346 | G4double fGamma |
---|
347 | = fine_structure_const*fK*finalEnergy |
---|
348 | / (pi*Q2*initialEnergy*(1.0 - fEpsilon)); |
---|
349 | G4double sigma_t = 0.12*millibarn; |
---|
350 | G4double sigma_l = 0.3*(1.0-Q2/(1.868*GeV*fNu))*sigma_t; |
---|
351 | if(sigma_l < 0.) sigma_l = 0.; |
---|
352 | |
---|
353 | return fGamma*(sigma_t+fEpsilon*sigma_l); |
---|
354 | } |
---|