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This commit is contained in:
Gabriele Cosmo
2019-04-17 10:39:02 +02:00
parent a7fdc52004
commit 28a70706e0
661 changed files with 55791 additions and 106984 deletions
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source/processes/electromagnetic/highenergy/src/G4GammaConversionToMuons.cc
+20 -13
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@@ -56,8 +56,9 @@ G4GammaConversionToMuons::G4GammaConversionToMuons(const G4String& processName,
: G4VDiscreteProcess (processName, type),
Mmuon(G4MuonPlus::MuonPlus()->GetPDGMass()),
Rc(elm_coupling/Mmuon),
LowestEnergyLimit (4.*Mmuon), // 4*Mmuon
HighestEnergyLimit(1e21*eV), // ok to 1e21eV=1e12GeV, then LPM suppression
LimitEnergy (5.*Mmuon),
LowestEnergyLimit (2.*Mmuon),
HighestEnergyLimit(1e12*GeV), // ok to 1e12GeV, then LPM suppression
CrossSecFactor(1.)
{
SetProcessSubType(fGammaConversionToMuMu);
@@ -116,12 +117,19 @@ G4GammaConversionToMuons::ComputeMeanFreePath(G4double GammaEnergy,
const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();
G4double SIGMA = 0.0;
G4double fact = 1.0;
G4double e = GammaEnergy;
// low energy approximation as in Bethe-Heitler model
if(e < LimitEnergy) {
G4double y = (e - LowestEnergyLimit)/(LimitEnergy - LowestEnergyLimit);
fact = y*y;
e = LimitEnergy;
}
for ( size_t i=0 ; i < aMaterial->GetNumberOfElements(); ++i)
{
SIGMA += NbOfAtomsPerVolume[i] *
ComputeCrossSectionPerAtom(GammaEnergy,
(*theElementVector)[i]->GetZasInt());
SIGMA += NbOfAtomsPerVolume[i] * fact *
ComputeCrossSectionPerAtom(e, (*theElementVector)[i]->GetZasInt());
}
return (SIGMA > 0.0) ? 1./SIGMA : DBL_MAX;
}
@@ -147,7 +155,7 @@ G4double G4GammaConversionToMuons::ComputeCrossSectionPerAtom(
// Total cross section parametrisation from H.Burkhardt
// It gives a good description at any energy (from 0 to 10**21 eV)
{
if(Egam <= LowestEnergyLimit) return 0.0; // below threshold return 0
if(Egam < LimitEnergy) return 0.0; // below threshold return 0
G4double CrossSection = 0.0;
G4NistManager* nist = G4NistManager::Instance();
@@ -235,11 +243,11 @@ G4VParticleChange* G4GammaConversionToMuons::PostStepDoIt(
G4double C2Term2=electron_mass_c2/(183.*Zthird*Mmuon);
G4double GammaMuonInv=Mmuon/Egam;
G4double sqrtx=sqrt(.25-GammaMuonInv);
G4double xmax=.5+sqrtx;
G4double xmin=.5-sqrtx;
// generate xPlus according to the differential cross section by rejection
G4double xmin=(Egam < LimitEnergy) ? GammaMuonInv : .5-sqrt(.25-GammaMuonInv);
G4double xmax=1.-xmin;
G4double Ds2=(Dn*sqrte-2.);
G4double sBZ=sqrte*B*Zthird/electron_mass_c2;
G4double LogWmaxInv=1./G4Log(Winfty*(1.+2.*Ds2*GammaMuonInv)
@@ -247,15 +255,14 @@ G4VParticleChange* G4GammaConversionToMuons::PostStepDoIt(
G4double xPlus,xMinus,xPM,result,W;
G4int nn = 0;
const G4int nmax = 1000;
do
{ xPlus=xmin+G4UniformRand()*(xmax-xmin);
do {
xPlus=xmin+G4UniformRand()*(xmax-xmin);
xMinus=1.-xPlus;
xPM=xPlus*xMinus;
G4double del=Mmuon*Mmuon/(2.*Egam*xPM);
W=Winfty*(1.+Ds2*del/Mmuon)/(1.+sBZ*del);
if(W<=1. || nn > nmax) { break; } // to avoid negative cross section at xmin
G4double xxp=1.-4./3.*xPM; // the main xPlus dependence
result=xxp*G4Log(W)*LogWmaxInv;
result=(xxp > 0.) ? xxp*G4Log(W)*LogWmaxInv : 0.0;
if(result>1.) {
G4cout << "G4GammaConversionToMuons::PostStepDoIt WARNING:"
<< " in dSigxPlusGen, result=" << result << " > 1" << G4endl;