[819] | 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 | // |
---|
[961] | 27 | // $Id: G4AnnihiToMuPair.cc,v 1.5 2008/10/16 14:29:48 vnivanch Exp $ |
---|
| 28 | // GEANT4 tag $Name: geant4-09-02-ref-02 $ |
---|
[819] | 29 | // |
---|
| 30 | // ------------ G4AnnihiToMuPair physics process ------ |
---|
| 31 | // by H.Burkhardt, S. Kelner and R. Kokoulin, November 2002 |
---|
| 32 | // ----------------------------------------------------------------------------- |
---|
| 33 | // |
---|
| 34 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......// |
---|
| 35 | // |
---|
| 36 | // 27.01.03 : first implementation (hbu) |
---|
| 37 | // 04.02.03 : cosmetic simplifications (mma) |
---|
| 38 | // 25.10.04 : migrade to new interfaces of ParticleChange (vi) |
---|
| 39 | // |
---|
| 40 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 41 | |
---|
| 42 | #include "G4AnnihiToMuPair.hh" |
---|
| 43 | |
---|
| 44 | #include "G4ios.hh" |
---|
| 45 | #include "Randomize.hh" |
---|
| 46 | |
---|
| 47 | #include "G4Positron.hh" |
---|
| 48 | #include "G4MuonPlus.hh" |
---|
| 49 | #include "G4MuonMinus.hh" |
---|
| 50 | #include "G4Material.hh" |
---|
| 51 | #include "G4Step.hh" |
---|
| 52 | |
---|
| 53 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 54 | |
---|
| 55 | using namespace std; |
---|
| 56 | |
---|
| 57 | G4AnnihiToMuPair::G4AnnihiToMuPair(const G4String& processName, |
---|
| 58 | G4ProcessType type):G4VDiscreteProcess (processName, type) |
---|
| 59 | { |
---|
| 60 | //e+ Energy threshold |
---|
| 61 | const G4double Mu_massc2 = G4MuonPlus::MuonPlus()->GetPDGMass(); |
---|
| 62 | LowestEnergyLimit = 2*Mu_massc2*Mu_massc2/electron_mass_c2 - electron_mass_c2; |
---|
| 63 | |
---|
| 64 | //modele ok up to 1000 TeV due to neglected Z-interference |
---|
| 65 | HighestEnergyLimit = 1000*TeV; |
---|
| 66 | |
---|
| 67 | CrossSecFactor = 1.; |
---|
[961] | 68 | SetProcessSubType(6); |
---|
| 69 | |
---|
[819] | 70 | } |
---|
| 71 | |
---|
| 72 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 73 | |
---|
| 74 | G4AnnihiToMuPair::~G4AnnihiToMuPair() // (empty) destructor |
---|
| 75 | { } |
---|
| 76 | |
---|
| 77 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 78 | |
---|
| 79 | G4bool G4AnnihiToMuPair::IsApplicable(const G4ParticleDefinition& particle) |
---|
| 80 | { |
---|
| 81 | return ( &particle == G4Positron::Positron() ); |
---|
| 82 | } |
---|
| 83 | |
---|
| 84 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 85 | |
---|
| 86 | void G4AnnihiToMuPair::BuildPhysicsTable(const G4ParticleDefinition&) |
---|
| 87 | // Build cross section and mean free path tables |
---|
| 88 | //here no tables, just calling PrintInfoDefinition |
---|
| 89 | { |
---|
| 90 | PrintInfoDefinition(); |
---|
| 91 | } |
---|
| 92 | |
---|
| 93 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 94 | |
---|
| 95 | void G4AnnihiToMuPair::SetCrossSecFactor(G4double fac) |
---|
| 96 | // Set the factor to artificially increase the cross section |
---|
| 97 | { |
---|
| 98 | CrossSecFactor = fac; |
---|
| 99 | G4cout << "The cross section for AnnihiToMuPair is artificially " |
---|
| 100 | << "increased by the CrossSecFactor=" << CrossSecFactor << G4endl; |
---|
| 101 | } |
---|
| 102 | |
---|
| 103 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 104 | |
---|
| 105 | G4double G4AnnihiToMuPair::ComputeCrossSectionPerAtom(G4double Epos, G4double Z) |
---|
| 106 | // Calculates the microscopic cross section in GEANT4 internal units. |
---|
| 107 | // It gives a good description from threshold to 1000 GeV |
---|
| 108 | { |
---|
| 109 | static const G4double Mmuon = G4MuonPlus::MuonPlus()->GetPDGMass(); |
---|
| 110 | static const G4double Rmuon = elm_coupling/Mmuon; //classical particle radius |
---|
| 111 | static const G4double Sig0 = pi*Rmuon*Rmuon/3.; //constant in crossSection |
---|
| 112 | |
---|
| 113 | G4double CrossSection = 0.; |
---|
| 114 | if (Epos < LowestEnergyLimit) return CrossSection; |
---|
| 115 | |
---|
| 116 | G4double xi = LowestEnergyLimit/Epos; |
---|
| 117 | G4double SigmaEl = Sig0*xi*(1.+xi/2.)*sqrt(1.-xi); // per electron |
---|
| 118 | CrossSection = SigmaEl*Z; // number of electrons per atom |
---|
| 119 | CrossSection *= CrossSecFactor; //increase the CrossSection by (default 1) |
---|
| 120 | return CrossSection; |
---|
| 121 | } |
---|
| 122 | |
---|
| 123 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 124 | |
---|
| 125 | G4double G4AnnihiToMuPair::GetMeanFreePath(const G4Track& aTrack, |
---|
| 126 | G4double, G4ForceCondition*) |
---|
| 127 | |
---|
| 128 | // returns the positron mean free path in GEANT4 internal units |
---|
| 129 | |
---|
| 130 | { |
---|
| 131 | const G4DynamicParticle* aDynamicPositron = aTrack.GetDynamicParticle(); |
---|
| 132 | G4double PositronEnergy = aDynamicPositron->GetKineticEnergy() |
---|
| 133 | +electron_mass_c2; |
---|
| 134 | G4Material* aMaterial = aTrack.GetMaterial(); |
---|
| 135 | const G4ElementVector* theElementVector = aMaterial->GetElementVector(); |
---|
| 136 | const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume(); |
---|
| 137 | |
---|
| 138 | G4double SIGMA = 0 ; |
---|
| 139 | |
---|
| 140 | for ( size_t i=0 ; i < aMaterial->GetNumberOfElements() ; i++ ) |
---|
| 141 | { |
---|
| 142 | G4double AtomicZ = (*theElementVector)[i]->GetZ(); |
---|
| 143 | SIGMA += NbOfAtomsPerVolume[i] * |
---|
| 144 | ComputeCrossSectionPerAtom(PositronEnergy,AtomicZ); |
---|
| 145 | } |
---|
| 146 | return SIGMA > DBL_MIN ? 1./SIGMA : DBL_MAX; |
---|
| 147 | } |
---|
| 148 | |
---|
| 149 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 150 | |
---|
| 151 | G4VParticleChange* G4AnnihiToMuPair::PostStepDoIt(const G4Track& aTrack, |
---|
| 152 | const G4Step& aStep) |
---|
| 153 | // |
---|
| 154 | // generation of e+e- -> mu+mu- |
---|
| 155 | // |
---|
| 156 | { |
---|
| 157 | |
---|
| 158 | aParticleChange.Initialize(aTrack); |
---|
| 159 | static const G4double Mele=electron_mass_c2; |
---|
| 160 | static const G4double Mmuon=G4MuonPlus::MuonPlus()->GetPDGMass(); |
---|
| 161 | |
---|
| 162 | // current Positron energy and direction, return if energy too low |
---|
| 163 | const G4DynamicParticle *aDynamicPositron = aTrack.GetDynamicParticle(); |
---|
| 164 | G4double Epos = aDynamicPositron->GetKineticEnergy()+Mele; |
---|
| 165 | |
---|
| 166 | if (Epos < LowestEnergyLimit) |
---|
| 167 | { G4cout |
---|
| 168 | << "error in G4AnnihiToMuPair::PostStepDoIt called with energy below" |
---|
| 169 | " threshold Epos= " |
---|
| 170 | << Epos << G4endl; // shoud never happen |
---|
| 171 | G4Exception(10); |
---|
| 172 | } |
---|
| 173 | |
---|
| 174 | if (Epos < LowestEnergyLimit) |
---|
| 175 | return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep); |
---|
| 176 | |
---|
| 177 | G4ParticleMomentum PositronDirection = |
---|
| 178 | aDynamicPositron->GetMomentumDirection(); |
---|
| 179 | G4double xi = LowestEnergyLimit/Epos; // xi is always less than 1, |
---|
| 180 | // goes to 0 at high Epos |
---|
| 181 | |
---|
| 182 | // generate cost |
---|
| 183 | // |
---|
| 184 | G4double cost; |
---|
| 185 | do cost = 2.*G4UniformRand()-1.; |
---|
| 186 | while (2.*G4UniformRand() > 1.+xi+cost*cost*(1.-xi) ); |
---|
| 187 | //1+cost**2 at high Epos |
---|
| 188 | G4double sint = sqrt(1.-cost*cost); |
---|
| 189 | |
---|
| 190 | // generate phi |
---|
| 191 | // |
---|
| 192 | G4double phi=2.*pi*G4UniformRand(); |
---|
| 193 | |
---|
| 194 | G4double Ecm = sqrt(0.5*Mele*(Epos+Mele)); |
---|
| 195 | G4double Pcm = sqrt(Ecm*Ecm-Mmuon*Mmuon); |
---|
| 196 | G4double beta = sqrt((Epos-Mele)/(Epos+Mele)); |
---|
| 197 | G4double gamma = Ecm/Mele; // =sqrt((Epos+Mele)/(2.*Mele)); |
---|
| 198 | G4double Pt = Pcm*sint; |
---|
| 199 | |
---|
| 200 | // energy and momentum of the muons in the Lab |
---|
| 201 | // |
---|
| 202 | G4double EmuPlus = gamma*( Ecm+cost*beta*Pcm); |
---|
| 203 | G4double EmuMinus = gamma*( Ecm-cost*beta*Pcm); |
---|
| 204 | G4double PmuPlusZ = gamma*(beta*Ecm+cost* Pcm); |
---|
| 205 | G4double PmuMinusZ = gamma*(beta*Ecm-cost* Pcm); |
---|
| 206 | G4double PmuPlusX = Pt*cos(phi); |
---|
| 207 | G4double PmuPlusY = Pt*sin(phi); |
---|
| 208 | G4double PmuMinusX =-Pt*cos(phi); |
---|
| 209 | G4double PmuMinusY =-Pt*sin(phi); |
---|
| 210 | // absolute momenta |
---|
| 211 | G4double PmuPlus = sqrt(Pt*Pt+PmuPlusZ *PmuPlusZ ); |
---|
| 212 | G4double PmuMinus = sqrt(Pt*Pt+PmuMinusZ*PmuMinusZ); |
---|
| 213 | |
---|
| 214 | // mu+ mu- directions for Positron in z-direction |
---|
| 215 | // |
---|
| 216 | G4ThreeVector |
---|
| 217 | MuPlusDirection ( PmuPlusX/PmuPlus, PmuPlusY/PmuPlus, PmuPlusZ/PmuPlus ); |
---|
| 218 | G4ThreeVector |
---|
| 219 | MuMinusDirection(PmuMinusX/PmuMinus,PmuMinusY/PmuMinus,PmuMinusZ/PmuMinus); |
---|
| 220 | |
---|
| 221 | // rotate to actual Positron direction |
---|
| 222 | // |
---|
| 223 | MuPlusDirection.rotateUz(PositronDirection); |
---|
| 224 | MuMinusDirection.rotateUz(PositronDirection); |
---|
| 225 | |
---|
| 226 | aParticleChange.SetNumberOfSecondaries(2); |
---|
| 227 | // create G4DynamicParticle object for the particle1 |
---|
| 228 | G4DynamicParticle* aParticle1= new G4DynamicParticle( |
---|
| 229 | G4MuonPlus::MuonPlus(),MuPlusDirection,EmuPlus-Mmuon); |
---|
| 230 | aParticleChange.AddSecondary(aParticle1); |
---|
| 231 | // create G4DynamicParticle object for the particle2 |
---|
| 232 | G4DynamicParticle* aParticle2= new G4DynamicParticle( |
---|
| 233 | G4MuonMinus::MuonMinus(),MuMinusDirection,EmuMinus-Mmuon); |
---|
| 234 | aParticleChange.AddSecondary(aParticle2); |
---|
| 235 | |
---|
| 236 | // Kill the incident positron |
---|
| 237 | // |
---|
| 238 | aParticleChange.ProposeEnergy(0.); |
---|
| 239 | aParticleChange.ProposeTrackStatus(fStopAndKill); |
---|
| 240 | |
---|
| 241 | return &aParticleChange; |
---|
| 242 | } |
---|
| 243 | |
---|
| 244 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 245 | |
---|
| 246 | void G4AnnihiToMuPair::PrintInfoDefinition() |
---|
| 247 | { |
---|
[961] | 248 | G4String comments ="e+e->mu+mu- annihilation, atomic e- at rest, SubType=."; |
---|
| 249 | G4cout << G4endl << GetProcessName() << ": " << comments |
---|
| 250 | << GetProcessSubType() << G4endl; |
---|
| 251 | G4cout << " threshold at " << LowestEnergyLimit/GeV << " GeV" |
---|
[819] | 252 | << " good description up to " |
---|
| 253 | << HighestEnergyLimit/TeV << " TeV for all Z." << G4endl; |
---|
| 254 | } |
---|
| 255 | |
---|
| 256 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|