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Geant4/processes/hadronic/stopping/src/G4MuMinusCapturePrecompound.cc

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 26 //
 27 //-----------------------------------------------------------------------------
 28 //
 29 // GEANT4 Class file 
 30 //
 31 // File name:  G4MuMinusCapturePrecompound
 32 //
 33 // Author:        V.Ivanchenko (Vladimir.Ivantchenko@cern.ch)
 34 // 
 35 // Creation date: 22 April 2012 on base of G4MuMinusCaptureCascade
 36 //
 37 //
 38 //-----------------------------------------------------------------------------
 39 //
 40 // Modifications: 
 41 //
 42 //-----------------------------------------------------------------------------
 43 
 44 #include "G4MuMinusCapturePrecompound.hh"
 45 #include "Randomize.hh" 
 46 #include "G4RandomDirection.hh"
 47 #include "G4PhysicalConstants.hh"
 48 #include "G4SystemOfUnits.hh"
 49 #include "G4MuonMinus.hh"
 50 #include "G4NeutrinoMu.hh"
 51 #include "G4Neutron.hh"
 52 #include "G4Proton.hh"
 53 #include "G4Triton.hh"
 54 #include "G4LorentzVector.hh"
 55 #include "G4ParticleDefinition.hh"
 56 #include "G4NucleiProperties.hh"
 57 #include "G4VPreCompoundModel.hh"
 58 #include "G4PreCompoundModel.hh"
 59 #include "G4HadronicInteractionRegistry.hh"
 60 
 61 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
 62 
 63 G4MuMinusCapturePrecompound::G4MuMinusCapturePrecompound(
 64     G4VPreCompoundModel* ptr)
 65   : G4HadronicInteraction("muMinusNuclearCapture")
 66 { 
 67   fMuMass = G4MuonMinus::MuonMinus()->GetPDGMass(); 
 68   fProton = G4Proton::Proton();
 69   fNeutron = G4Neutron::Neutron();
 70   fThreshold = 10*MeV;
 71   fTime = 0.0;
 72   fPreCompound = ptr;
 73   if(!ptr) { 
 74     G4HadronicInteraction* p =
 75       G4HadronicInteractionRegistry::Instance()->FindModel("PRECO");
 76     ptr = static_cast<G4VPreCompoundModel*>(p); 
 77     fPreCompound = ptr;
 78     if(!ptr) { fPreCompound = new G4PreCompoundModel(); }
 79   }
 80 }
 81 
 82 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
 83 
 84 G4MuMinusCapturePrecompound::~G4MuMinusCapturePrecompound()
 85 {
 86   result.Clear();
 87 }
 88 
 89 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
 90 
 91 G4HadFinalState* 
 92 G4MuMinusCapturePrecompound::ApplyYourself(const G4HadProjectile& projectile, 
 93              G4Nucleus& targetNucleus)
 94 {
 95   result.Clear();
 96   result.SetStatusChange(stopAndKill);
 97   fTime = projectile.GetGlobalTime();
 98   G4double time0 = fTime;
 99 
100   G4double muBindingEnergy = projectile.GetBoundEnergy();
101 
102   G4int Z = targetNucleus.GetZ_asInt(); 
103   G4int A = targetNucleus.GetA_asInt();
104   G4double massA = G4NucleiProperties::GetNuclearMass(A, Z);
105 
106   /*
107   G4cout << "G4MuMinusCapturePrecompound::ApplyYourself: Emu= "
108    << muBindingEnergy << G4endl;
109   */
110   // Energy on K-shell
111   G4double muEnergy = fMuMass + muBindingEnergy;
112   G4double muMom =std::sqrt(muBindingEnergy*(muBindingEnergy + 2.0*fMuMass));
113   G4double availableEnergy = massA + fMuMass - muBindingEnergy;
114   G4double residualMass = G4NucleiProperties::GetNuclearMass(A, Z - 1);
115 
116   G4ThreeVector vmu = muMom*G4RandomDirection();
117   G4LorentzVector aMuMom(vmu, muEnergy);
118 
119   const G4double nenergy = keV;    
120 
121   // p or 3He as a target 
122   // two body reaction mu- + A(Z,A) -> nuMu + A(Z-1,A)
123   if((1 == Z && 1 == A) || (2 == Z && 3 == A)) {
124 
125     const G4ParticleDefinition* pd = 0;
126     if(1 == Z) { pd = fNeutron; }
127     else { pd = G4Triton::Triton(); }
128 
129     //
130     //  Computation in assumption of CM reaction
131     //  
132     G4double e = 0.5*(availableEnergy - 
133           residualMass*residualMass/availableEnergy);
134 
135     G4ThreeVector nudir = G4RandomDirection();
136     AddNewParticle(G4NeutrinoMu::NeutrinoMu(), nudir, e);
137     nudir *= -1.0;
138     AddNewParticle(pd, nudir, availableEnergy - e - residualMass);
139 
140   // d or 4He as a target 
141   // three body reaction mu- + A(Z,A) -> nuMu + n + A(Z-1,A)
142   // extra neutron produced at rest
143   } else if((1 == Z && 2 == A) || (2 == Z && 4 == A)) {
144 
145     const G4ParticleDefinition* pd = 0;
146     if(1 == Z) { pd = fNeutron; }
147     else { pd = G4Triton::Triton(); }
148 
149     availableEnergy -= neutron_mass_c2 - nenergy;
150     residualMass = pd->GetPDGMass();
151 
152     //
153     //  Computation in assumption of CM reaction
154     //  
155     G4double e = 0.5*(availableEnergy - 
156           residualMass*residualMass/availableEnergy);
157 
158     G4ThreeVector nudir = G4RandomDirection();
159     AddNewParticle(G4NeutrinoMu::NeutrinoMu(), nudir, e);
160     nudir *= -1.0;
161     AddNewParticle(pd, nudir, availableEnergy - e - residualMass);
162 
163     // extra low-energy neutron
164     nudir = G4RandomDirection();
165     AddNewParticle(fNeutron, nudir, nenergy);
166 
167   } else {
168     // sample mu- + p -> nuMu + n reaction in CM of muonic atom
169 
170     // nucleus
171     G4LorentzVector momInitial(0.0,0.0,0.0,availableEnergy);
172     G4LorentzVector momResidual, momNu;
173 
174     // pick random proton inside nucleus 
175     G4double eEx;
176     fNucleus.Init(A, Z);
177     const std::vector<G4Nucleon>& nucleons= fNucleus.GetNucleons();
178     const G4ParticleDefinition* pDef;
179 
180     G4int reentryCount = 0;
181   
182     do {
183       ++reentryCount;
184       G4int index = 0;
185       do {
186   index=G4int(A*G4UniformRand());
187   pDef = nucleons[index].GetDefinition();
188       } while(pDef != fProton);
189       G4LorentzVector momP = nucleons[index].Get4Momentum();
190 
191       // Get CMS kinematics
192       G4LorentzVector theCMS = momP + aMuMom;
193       G4ThreeVector bst = theCMS.boostVector();
194 
195       G4double Ecms = theCMS.mag();
196       G4double Enu  = 0.5*(Ecms - neutron_mass_c2*neutron_mass_c2/Ecms);
197       eEx = 0.0;
198 
199       if(Enu > 0.0) {
200   // make the nu, and transform to lab;
201   momNu.set(Enu*G4RandomDirection(), Enu);
202 
203   // nu in lab.
204   momNu.boost(bst);
205   momResidual = momInitial - momNu;
206   eEx = momResidual.mag() - residualMass;
207         if(eEx < 0.0 && eEx + nenergy >= 0.0) {
208           momResidual.set(0.0, 0.0, 0.0, residualMass);
209           eEx = 0.0;
210   }
211       }
212       // in the case of many iterations stop the loop
213       // with zero excitation energy
214       if(reentryCount > 100 && eEx < 0.0) {
215   G4ExceptionDescription ed;
216   ed << "Call for " << GetModelName() << G4endl;
217   ed << "Target  Z= " << Z  
218      << "  A= " << A << "  Eex(MeV)= " << eEx/MeV << G4endl;
219   ed << " ApplyYourself does not completed after 100 attempts -"
220      << " excitation energy is set to zero";
221   G4Exception("G4MuMinusCapturePrecompound::ApplyYourself", "had006", 
222         JustWarning, ed);
223   momResidual.set(0.0, 0.0, 0.0, residualMass);
224   eEx = 0.0;
225       }
226       // Loop checking, 06-Aug-2015, Vladimir Ivanchenko
227     } while(eEx <= 0.0);
228 
229     G4ThreeVector dir = momNu.vect().unit();
230     AddNewParticle(G4NeutrinoMu::NeutrinoMu(), dir, momNu.e());
231 
232     G4Fragment initialState(A, Z-1, momResidual);
233     initialState.SetNumberOfExcitedParticle(2,0);
234     initialState.SetNumberOfHoles(1,1);
235 
236     // decay time for pre-compound/de-excitation starts from zero
237     G4ReactionProductVector* rpv = fPreCompound->DeExcite(initialState);
238     size_t n = rpv->size();
239     for(size_t i=0; i<n; ++i) {
240       G4ReactionProduct* rp = (*rpv)[i];
241 
242       // reaction time
243       fTime = time0 + rp->GetTOF();
244       G4ThreeVector direction = rp->GetMomentum().unit();
245       AddNewParticle(rp->GetDefinition(), direction, rp->GetKineticEnergy());
246       delete rp;
247     }
248     delete rpv;
249   } 
250   if(verboseLevel > 1)
251     G4cout << "G4MuMinusCapturePrecompound::ApplyYourself:  Nsec= " 
252      << result.GetNumberOfSecondaries() 
253      <<" E0(MeV)= " <<availableEnergy/MeV
254      <<" Mres(GeV)= " <<residualMass/GeV
255      <<G4endl;
256 
257   return &result;
258 }
259 
260 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
261 
262 void G4MuMinusCapturePrecompound::ModelDescription(std::ostream& outFile) const
263 {
264   outFile << "Sampling of mu- capture by atomic nucleus from K-shell"
265     << " mesoatom orbit.\n"
266     << "Primary reaction mu- + p -> n + neutrino, neutron providing\n"
267     << "  initial excitation of the target nucleus and PreCompound"
268     << " model samples final state\n";
269 }
270 
271 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
272