G4AnnihiToMuPair Class Reference

#include <G4AnnihiToMuPair.hh>

Inheritance diagram for G4AnnihiToMuPair:

G4VDiscreteProcess G4VProcess

Public Member Functions

 G4AnnihiToMuPair (const G4String &processName="AnnihiToMuPair", G4ProcessType type=fElectromagnetic)
 ~G4AnnihiToMuPair ()
G4bool IsApplicable (const G4ParticleDefinition &)
void BuildPhysicsTable (const G4ParticleDefinition &)
void PrintInfoDefinition ()
void SetCrossSecFactor (G4double fac)
G4double GetCrossSecFactor ()
G4double CrossSectionPerVolume (G4double PositronEnergy, const G4Material *)
G4double ComputeCrossSectionPerAtom (G4double PositronEnergy, G4double AtomicZ)
G4double GetMeanFreePath (const G4Track &aTrack, G4double previousStepSize, G4ForceCondition *)
G4VParticleChangePostStepDoIt (const G4Track &aTrack, const G4Step &aStep)

Detailed Description

Definition at line 57 of file G4AnnihiToMuPair.hh.


Constructor & Destructor Documentation

G4AnnihiToMuPair::G4AnnihiToMuPair ( const G4String processName = "AnnihiToMuPair",
G4ProcessType  type = fElectromagnetic 
)

Definition at line 58 of file G4AnnihiToMuPair.cc.

References G4ParticleDefinition::GetPDGMass(), G4MuonPlus::MuonPlus(), and G4VProcess::SetProcessSubType().

00059                        :G4VDiscreteProcess (processName, type)
00060 {
00061  //e+ Energy threshold
00062  const G4double Mu_massc2 = G4MuonPlus::MuonPlus()->GetPDGMass();
00063  LowestEnergyLimit  = 2*Mu_massc2*Mu_massc2/electron_mass_c2 - electron_mass_c2;
00064  
00065  //modele ok up to 1000 TeV due to neglected Z-interference
00066  HighestEnergyLimit = 1000*TeV;
00067  
00068  CurrentSigma = 0.0;
00069  CrossSecFactor = 1.;
00070  SetProcessSubType(6);
00071 
00072 }

G4AnnihiToMuPair::~G4AnnihiToMuPair (  ) 

Definition at line 76 of file G4AnnihiToMuPair.cc.

00077 { }


Member Function Documentation

void G4AnnihiToMuPair::BuildPhysicsTable ( const G4ParticleDefinition  )  [virtual]

Reimplemented from G4VProcess.

Definition at line 88 of file G4AnnihiToMuPair.cc.

References PrintInfoDefinition().

00091 {
00092   CurrentSigma = 0.0;
00093   PrintInfoDefinition();
00094 }

G4double G4AnnihiToMuPair::ComputeCrossSectionPerAtom ( G4double  PositronEnergy,
G4double  AtomicZ 
)

Definition at line 108 of file G4AnnihiToMuPair.cc.

References G4ParticleDefinition::GetPDGMass(), G4MuonPlus::MuonPlus(), and G4INCL::Math::pi.

Referenced by CrossSectionPerVolume().

00111 {
00112   static const G4double Mmuon = G4MuonPlus::MuonPlus()->GetPDGMass();
00113   static const G4double Rmuon = elm_coupling/Mmuon; //classical particle radius
00114   static const G4double Sig0  = pi*Rmuon*Rmuon/3.;  //constant in crossSection
00115 
00116   G4double CrossSection = 0.;
00117   if (Epos < LowestEnergyLimit) return CrossSection;
00118    
00119   G4double xi = LowestEnergyLimit/Epos;
00120   G4double SigmaEl = Sig0*xi*(1.+xi/2.)*sqrt(1.-xi); // per electron
00121   CrossSection = SigmaEl*Z;         // number of electrons per atom
00122   return CrossSection;
00123 }

G4double G4AnnihiToMuPair::CrossSectionPerVolume ( G4double  PositronEnergy,
const G4Material  
)

Definition at line 127 of file G4AnnihiToMuPair.cc.

References ComputeCrossSectionPerAtom(), G4Material::GetElementVector(), G4Material::GetNumberOfElements(), and G4Material::GetVecNbOfAtomsPerVolume().

Referenced by GetMeanFreePath(), and PostStepDoIt().

00129 {
00130   const G4ElementVector* theElementVector = aMaterial->GetElementVector();
00131   const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();
00132 
00133   G4double SIGMA = 0.0;
00134 
00135   for ( size_t i=0 ; i < aMaterial->GetNumberOfElements() ; ++i )
00136   {
00137     G4double AtomicZ = (*theElementVector)[i]->GetZ();
00138     SIGMA += NbOfAtomsPerVolume[i] *
00139       ComputeCrossSectionPerAtom(PositronEnergy,AtomicZ);
00140   }
00141   return SIGMA;
00142 }

G4double G4AnnihiToMuPair::GetCrossSecFactor (  )  [inline]

Definition at line 81 of file G4AnnihiToMuPair.hh.

00081 {return CrossSecFactor;};

G4double G4AnnihiToMuPair::GetMeanFreePath ( const G4Track aTrack,
G4double  previousStepSize,
G4ForceCondition  
) [virtual]

Implements G4VDiscreteProcess.

Definition at line 146 of file G4AnnihiToMuPair.cc.

References CrossSectionPerVolume(), DBL_MAX, DBL_MIN, G4Track::GetDynamicParticle(), G4DynamicParticle::GetKineticEnergy(), and G4Track::GetMaterial().

00151 {
00152   const G4DynamicParticle* aDynamicPositron = aTrack.GetDynamicParticle();
00153   G4double PositronEnergy = aDynamicPositron->GetKineticEnergy()
00154                                               +electron_mass_c2;
00155   G4Material* aMaterial = aTrack.GetMaterial();
00156   CurrentSigma = CrossSectionPerVolume(PositronEnergy, aMaterial);
00157 
00158   // increase the CrossSection by CrossSecFactor (default 1)
00159   G4double mfp = DBL_MAX;
00160   if(CurrentSigma > DBL_MIN) mfp = 1.0/(CurrentSigma*CrossSecFactor);
00161 
00162   return mfp;
00163 }

G4bool G4AnnihiToMuPair::IsApplicable ( const G4ParticleDefinition  )  [virtual]

Reimplemented from G4VProcess.

Definition at line 81 of file G4AnnihiToMuPair.cc.

References G4Positron::Positron().

00082 {
00083   return ( &particle == G4Positron::Positron() );
00084 }

G4VParticleChange * G4AnnihiToMuPair::PostStepDoIt ( const G4Track aTrack,
const G4Step aStep 
) [virtual]

Reimplemented from G4VDiscreteProcess.

Definition at line 167 of file G4AnnihiToMuPair.cc.

References G4ParticleChange::AddSecondary(), G4VProcess::aParticleChange, CrossSectionPerVolume(), fStopAndKill, G4UniformRand, G4Track::GetDynamicParticle(), G4DynamicParticle::GetKineticEnergy(), G4Track::GetMaterial(), G4DynamicParticle::GetMomentumDirection(), G4ParticleDefinition::GetPDGMass(), G4ParticleChange::Initialize(), G4MuonMinus::MuonMinus(), G4MuonPlus::MuonPlus(), G4INCL::Math::pi, G4VDiscreteProcess::PostStepDoIt(), G4ParticleChange::ProposeEnergy(), G4VParticleChange::ProposeTrackStatus(), and G4VParticleChange::SetNumberOfSecondaries().

00172 {
00173 
00174   aParticleChange.Initialize(aTrack);
00175   static const G4double Mele=electron_mass_c2;
00176   static const G4double Mmuon=G4MuonPlus::MuonPlus()->GetPDGMass();
00177 
00178   // current Positron energy and direction, return if energy too low
00179   const G4DynamicParticle *aDynamicPositron = aTrack.GetDynamicParticle();
00180   G4double Epos = aDynamicPositron->GetKineticEnergy() + Mele; 
00181 
00182   // test of cross section
00183   if(CurrentSigma*G4UniformRand() > 
00184      CrossSectionPerVolume(Epos, aTrack.GetMaterial())) 
00185     {
00186       return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
00187     }
00188 
00189   if (Epos < LowestEnergyLimit) {
00190      return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
00191   }
00192 
00193   G4ParticleMomentum PositronDirection = 
00194                                        aDynamicPositron->GetMomentumDirection();
00195   G4double xi = LowestEnergyLimit/Epos; // xi is always less than 1,
00196                                         // goes to 0 at high Epos
00197 
00198   // generate cost
00199   //
00200   G4double cost;
00201   do cost = 2.*G4UniformRand()-1.;
00202   while (2.*G4UniformRand() > 1.+xi+cost*cost*(1.-xi) ); 
00203                                                        //1+cost**2 at high Epos
00204   G4double sint = sqrt(1.-cost*cost);
00205 
00206   // generate phi
00207   //
00208   G4double phi=2.*pi*G4UniformRand();
00209 
00210   G4double Ecm   = sqrt(0.5*Mele*(Epos+Mele));
00211   G4double Pcm   = sqrt(Ecm*Ecm-Mmuon*Mmuon);
00212   G4double beta  = sqrt((Epos-Mele)/(Epos+Mele));
00213   G4double gamma = Ecm/Mele;                    // =sqrt((Epos+Mele)/(2.*Mele));
00214   G4double Pt    = Pcm*sint;
00215   
00216   // energy and momentum of the muons in the Lab
00217   //
00218   G4double EmuPlus   = gamma*(     Ecm+cost*beta*Pcm);
00219   G4double EmuMinus  = gamma*(     Ecm-cost*beta*Pcm);
00220   G4double PmuPlusZ  = gamma*(beta*Ecm+cost*     Pcm);
00221   G4double PmuMinusZ = gamma*(beta*Ecm-cost*     Pcm);
00222   G4double PmuPlusX  = Pt*cos(phi);
00223   G4double PmuPlusY  = Pt*sin(phi);
00224   G4double PmuMinusX =-Pt*cos(phi);
00225   G4double PmuMinusY =-Pt*sin(phi);
00226   // absolute momenta
00227   G4double PmuPlus  = sqrt(Pt*Pt+PmuPlusZ *PmuPlusZ );
00228   G4double PmuMinus = sqrt(Pt*Pt+PmuMinusZ*PmuMinusZ);
00229 
00230   // mu+ mu- directions for Positron in z-direction
00231   //
00232   G4ThreeVector
00233     MuPlusDirection ( PmuPlusX/PmuPlus, PmuPlusY/PmuPlus,  PmuPlusZ/PmuPlus  );
00234   G4ThreeVector
00235     MuMinusDirection(PmuMinusX/PmuMinus,PmuMinusY/PmuMinus,PmuMinusZ/PmuMinus);
00236 
00237   // rotate to actual Positron direction
00238   //
00239   MuPlusDirection.rotateUz(PositronDirection);
00240   MuMinusDirection.rotateUz(PositronDirection);
00241 
00242   aParticleChange.SetNumberOfSecondaries(2);
00243   // create G4DynamicParticle object for the particle1
00244   G4DynamicParticle* aParticle1= new G4DynamicParticle(
00245                          G4MuonPlus::MuonPlus(),MuPlusDirection,EmuPlus-Mmuon);
00246   aParticleChange.AddSecondary(aParticle1);
00247   // create G4DynamicParticle object for the particle2
00248   G4DynamicParticle* aParticle2= new G4DynamicParticle(
00249                      G4MuonMinus::MuonMinus(),MuMinusDirection,EmuMinus-Mmuon);
00250   aParticleChange.AddSecondary(aParticle2);
00251 
00252   // Kill the incident positron 
00253   //
00254   aParticleChange.ProposeEnergy(0.); 
00255   aParticleChange.ProposeTrackStatus(fStopAndKill);
00256 
00257   return &aParticleChange;
00258 }

void G4AnnihiToMuPair::PrintInfoDefinition (  ) 

Definition at line 262 of file G4AnnihiToMuPair.cc.

References G4cout, G4endl, G4VProcess::GetProcessName(), and G4VProcess::GetProcessSubType().

Referenced by BuildPhysicsTable().

00263 {
00264   G4String comments ="e+e->mu+mu- annihilation, atomic e- at rest, SubType=.";
00265   G4cout << G4endl << GetProcessName() << ":  " << comments 
00266          << GetProcessSubType() << G4endl;
00267   G4cout << "        threshold at " << LowestEnergyLimit/GeV << " GeV"
00268          << " good description up to "
00269          << HighestEnergyLimit/TeV << " TeV for all Z." << G4endl;
00270 }

void G4AnnihiToMuPair::SetCrossSecFactor ( G4double  fac  ) 

Definition at line 98 of file G4AnnihiToMuPair.cc.

References G4cout, and G4endl.

00100 { 
00101   CrossSecFactor = fac;
00102   G4cout << "The cross section for AnnihiToMuPair is artificially "
00103          << "increased by the CrossSecFactor=" << CrossSecFactor << G4endl;
00104 }


The documentation for this class was generated from the following files:
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