lars/geant4
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
d93e1e39a93a5c9436b466088567f01189d7d643
geant4/source/processes/electromagnetic/muons/src/G4MuPairProductionModel.cc
T
Gabriele Cosmo d93e1e39a9 Import Geant4 7.1.0 source tree
2016-06-09 12:11:21 +02:00

600 lines
20 KiB
C++
Raw Blame History

//
// ********************************************************************
// * DISCLAIMER *
// * *
// * The following disclaimer summarizes all the specific disclaimers *
// * of contributors to this software. The specific disclaimers,which *
// * govern, are listed with their locations in: *
// * http://cern.ch/geant4/license *
// * *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work make any representation or warranty, express or implied, *
// * regarding this software system or assume any liability for its *
// * use. *
// * *
// * This code implementation is the intellectual property of the *
// * GEANT4 collaboration. *
// * By copying, distributing or modifying the Program (or any work *
// * based on the Program) you indicate your acceptance of this *
// * statement, and all its terms. *
// ********************************************************************
//
// $Id: G4MuPairProductionModel.cc,v 1.25 2005/04/12 18:12:33 vnivanch Exp $
// GEANT4 tag $Name: geant4-07-01 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name: G4MuPairProductionModel
//
// Author: Vladimir Ivanchenko on base of Laszlo Urban code
//
// Creation date: 24.06.2002
//
// Modifications:
//
// 04-12-02 Change G4DynamicParticle constructor in PostStep (V.Ivanchenko)
// 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
// 24-01-03 Fix for compounds (V.Ivanchenko)
// 27-01-03 Make models region aware (V.Ivanchenko)
// 13-02-03 Add model (V.Ivanchenko)
// 06-06-03 Fix in cross section calculation for high energy (V.Ivanchenko)
// 20-10-03 2*xi in ComputeDDMicroscopicCrossSection (R.Kokoulin)
// 8 integration points in ComputeDMicroscopicCrossSection
// 12-01-04 Take min cut of e- and e+ not its sum (V.Ivanchenko)
// 10-02-04 Update parameterisation using R.Kokoulin model (V.Ivanchenko)
// 28-04-04 For complex materials repeat calculation of max energy for each
// material (V.Ivanchenko)
// 01-11-04 Fix bug in expression inside ComputeDMicroscopicCrossSection (R.Kokoulin)
// 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
//
// Class Description:
//
//
// -------------------------------------------------------------------
//
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
#include "G4MuPairProductionModel.hh"
#include "G4Electron.hh"
#include "G4Positron.hh"
#include "G4MuonMinus.hh"
#include "G4MuonPlus.hh"
#include "Randomize.hh"
#include "G4Material.hh"
#include "G4Element.hh"
#include "G4ElementVector.hh"
#include "G4ProductionCutsTable.hh"
#include "G4ParticleChangeForLoss.hh"
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
// static members
//
G4double G4MuPairProductionModel::zdat[]={1.,4.,13.,29.,92.};
G4double G4MuPairProductionModel::adat[]={1.01,9.01,26.98,63.55,238.03};
G4double G4MuPairProductionModel::tdat[]={1.e3,1.e4,1.e5,1.e6,1.e7,1.e8,1.e9,1.e10};
G4double G4MuPairProductionModel::xgi[]={ 0.0199,0.1017,0.2372,0.4083,0.5917,0.7628,0.8983,0.9801 };
G4double G4MuPairProductionModel::wgi[]={ 0.0506,0.1112,0.1569,0.1813,0.1813,0.1569,0.1112,0.0506 };
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
using namespace std;
G4MuPairProductionModel::G4MuPairProductionModel(const G4ParticleDefinition*,
const G4String& nam)
: G4VEmModel(nam),
minPairEnergy(4.*electron_mass_c2),
lowestKinEnergy(1.*GeV),
factorForCross(4.*fine_structure_const*fine_structure_const
*classic_electr_radius*classic_electr_radius/(3.*pi)),
sqrte(sqrt(exp(1.))),
particleMass(G4MuonPlus::MuonPlus()->GetPDGMass()),
currentZ(0),
particle(G4MuonPlus::MuonPlus()),
nzdat(5),
ntdat(8),
nbiny(1000),
nmaxElements(0),
ymin(-5.),
ymax(0.),
dy((ymax-ymin)/nbiny),
samplingTablesAreFilled(false)
{
SetLowEnergyLimit(minPairEnergy);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4MuPairProductionModel::~G4MuPairProductionModel()
{}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MuPairProductionModel::MinEnergyCut(const G4ParticleDefinition*,
const G4MaterialCutsCouple* )
{
return minPairEnergy;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4MuPairProductionModel::Initialise(const G4ParticleDefinition*,
const G4DataVector&)
{
if (!samplingTablesAreFilled) MakeSamplingTables();
theElectron = G4Electron::Electron();
thePositron = G4Positron::Positron();
if(pParticleChange)
fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
else
fParticleChange = new G4ParticleChangeForLoss();
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MuPairProductionModel::ComputeDEDXPerVolume(
const G4Material* material,
const G4ParticleDefinition*,
G4double kineticEnergy,
G4double cutEnergy)
{
G4double dedx = 0.0;
if (cutEnergy <= minPairEnergy || kineticEnergy <= lowestKinEnergy) return dedx;
const G4ElementVector* theElementVector = material->GetElementVector();
const G4double* theAtomicNumDensityVector =
material->GetAtomicNumDensityVector();
// loop for elements in the material
for (size_t i=0; i<material->GetNumberOfElements(); i++) {
G4double Z = (*theElementVector)[i]->GetZ();
SetCurrentElement(Z);
G4double tmax = MaxSecondaryEnergy(particle, kineticEnergy);
G4double loss = ComputMuPairLoss(Z, kineticEnergy, cutEnergy, tmax);
dedx += loss*theAtomicNumDensityVector[i];
}
if (dedx < 0.) dedx = 0.;
return dedx;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MuPairProductionModel::ComputMuPairLoss(G4double Z,
G4double tkin, G4double cutEnergy,
G4double tmax)
{
SetCurrentElement(Z);
G4double loss = 0.0;
G4double cut = min(cutEnergy,tmax);
if(cut <= minPairEnergy) return loss;
// calculate the rectricted loss
// numerical integration in log(PairEnergy)
G4double ak1=6.9;
G4double ak2=1.0;
G4double aaa = log(minPairEnergy);
G4double bbb = log(cut);
G4int kkk = (G4int)((bbb-aaa)/ak1+ak2);
if (kkk > 8) kkk = 8;
G4double hhh = (bbb-aaa)/(G4double)kkk;
G4double x = aaa;
for (G4int l=0 ; l<kkk; l++)
{
for (G4int ll=0; ll<8; ll++)
{
G4double ep = exp(x+xgi[ll]*hhh);
loss += wgi[ll]*ep*ep*ComputeDMicroscopicCrossSection(tkin, Z, ep);
}
x += hhh;
}
loss *= hhh;
if (loss < 0.) loss = 0.;
return loss;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MuPairProductionModel::ComputeMicroscopicCrossSection(
G4double tkin,
G4double Z,
G4double cut)
{
G4double cross = 0. ;
SetCurrentElement(Z);
G4double tmax = MaxSecondaryEnergy(particle, tkin);
if (tmax <= cut) return cross;
G4double ak1=6.9 ;
G4double ak2=1.0 ;
G4double aaa = log(cut);
G4double bbb = log(tmax);
G4int kkk = (G4int)((bbb-aaa)/ak1 + ak2);
if(kkk > 8) kkk = 8;
G4double hhh = (bbb-aaa)/float(kkk);
G4double x = aaa;
for(G4int l=0; l<kkk; l++)
{
for(G4int i=0; i<8; i++)
{
G4double ep = exp(x + xgi[i]*hhh);
cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
}
x += hhh;
}
cross *=hhh;
if(cross < 0.0) cross = 0.0;
return cross;
}
G4double G4MuPairProductionModel::ComputeDMicroscopicCrossSection(
G4double tkin,
G4double Z,
G4double pairEnergy)
// Calculates the differential (D) microscopic cross section
// using the cross section formula of R.P. Kokoulin (18/01/98)
// Code modified by R.P. Kokoulin, V.N. Ivanchenko (27/01/04)
{
G4double bbbtf= 183. ;
G4double bbbh = 202.4 ;
G4double g1tf = 1.95e-5 ;
G4double g2tf = 5.3e-5 ;
G4double g1h = 4.4e-5 ;
G4double g2h = 4.8e-5 ;
G4double totalEnergy = tkin + particleMass;
G4double residEnergy = totalEnergy - pairEnergy;
G4double massratio = particleMass/electron_mass_c2 ;
G4double massratio2 = massratio*massratio ;
G4double cross = 0.;
SetCurrentElement(Z);
G4double c3 = 0.75*sqrte*particleMass;
if (residEnergy <= c3*z13) return cross;
G4double c7 = 4.*electron_mass_c2;
G4double c8 = 6.*particleMass*particleMass;
G4double alf = c7/pairEnergy;
G4double a3 = 1. - alf;
if (a3 <= 0.) return cross;
// zeta calculation
G4double bbb,g1,g2;
if( Z < 1.5 ) { bbb = bbbh ; g1 = g1h ; g2 = g2h ; }
else { bbb = bbbtf; g1 = g1tf; g2 = g2tf; }
G4double zeta = 0;
G4double zeta1 = 0.073 * log(totalEnergy/(particleMass+g1*z23*totalEnergy))-0.26 ;
if ( zeta1 > 0.)
{
G4double zeta2 = 0.058*log(totalEnergy/(particleMass+g2*z13*totalEnergy))-0.14 ;
zeta = zeta1/zeta2 ;
}
G4double z2 = Z*(Z+zeta);
G4double screen0 = 2.*electron_mass_c2*sqrte*bbb/(z13*pairEnergy);
G4double a0 = totalEnergy*residEnergy;
G4double a1 = pairEnergy*pairEnergy/a0;
G4double bet = 0.5*a1;
G4double xi0 = 0.25*massratio2*a1;
G4double del = c8/a0;
G4double rta3 = sqrt(a3);
G4double tmnexp = alf/(1. + rta3) + del*rta3;
if(tmnexp >= 1.0) return cross;
G4double tmn = log(tmnexp);
G4double sum = 0.;
// Gaussian integration in ln(1-ro) ( with 8 points)
for (G4int i=0; i<8; i++)
{
G4double a4 = exp(tmn*xgi[i]); // a4 = (1.-asymmetry)
G4double a5 = a4*(2.-a4) ;
G4double a6 = 1.-a5 ;
G4double a7 = 1.+a6 ;
G4double a9 = 3.+a6 ;
G4double xi = xi0*a5 ;
G4double xii = 1./xi ;
G4double xi1 = 1.+xi ;
G4double screen = screen0*xi1/a5 ;
G4double yeu = 5.-a6+4.*bet*a7 ;
G4double yed = 2.*(1.+3.*bet)*log(3.+xii)-a6-a1*(2.-a6) ;
G4double ye1 = 1.+yeu/yed ;
G4double ale=log(bbb/z13*sqrt(xi1*ye1)/(1.+screen*ye1)) ;
G4double cre = 0.5*log(1.+2.25*z23*xi1*ye1/massratio2) ;
G4double be;
if (xi <= 1.e3) be = ((2.+a6)*(1.+bet)+xi*a9)*log(1.+xii)+(a5-bet)/xi1-a9;
else be = (3.-a6+a1*a7)/(2.*xi);
G4double fe = (ale-cre)*be;
if ( fe < 0.) fe = 0. ;
G4double ymu = 4.+a6 +3.*bet*a7 ;
G4double ymd = a7*(1.5+a1)*log(3.+xi)+1.-1.5*a6 ;
G4double ym1 = 1.+ymu/ymd ;
G4double alm_crm = log(bbb*massratio/(1.5*z23*(1.+screen*ym1)));
G4double a10,bm;
if ( xi >= 1.e-3)
{
a10 = (1.+a1)*a5 ;
bm = (a7*(1.+1.5*bet)-a10*xii)*log(xi1)+xi*(a5-bet)/xi1+a10;
} else {
bm = (5.-a6+bet*a9)*(xi/2.);
}
G4double fm = alm_crm*bm;
if ( fm < 0.) fm = 0. ;
sum += wgi[i]*a4*(fe+fm/massratio2);
}
cross = -tmn*sum*factorForCross*z2*residEnergy/(totalEnergy*pairEnergy);
return cross;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MuPairProductionModel::CrossSectionPerVolume(
const G4Material* material,
const G4ParticleDefinition*,
G4double kineticEnergy,
G4double cutEnergy,
G4double maxEnergy)
{
G4double cross = 0.0;
if (kineticEnergy <= lowestKinEnergy) return cross;
maxEnergy += particleMass;
const G4ElementVector* theElementVector = material->GetElementVector();
const G4double* theAtomNumDensityVector = material->GetAtomicNumDensityVector();
for (size_t i=0; i<material->GetNumberOfElements(); i++) {
G4double Z = (*theElementVector)[i]->GetZ();
SetCurrentElement(Z);
G4double tmax = min(maxEnergy,MaxSecondaryEnergy(particle, kineticEnergy));
G4double cut = max(minPairEnergy,cutEnergy);
if(cut < tmax) {
G4double cr = ComputeMicroscopicCrossSection(kineticEnergy, Z, cut)
- ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
cross += theAtomNumDensityVector[i] * cr;
}
}
return cross;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4MuPairProductionModel::MakeSamplingTables()
{
for (G4int iz=0; iz<nzdat; iz++)
{
G4double Z = zdat[iz];
SetCurrentElement(Z);
for (G4int it=0; it<ntdat; it++)
{
G4double kineticEnergy = tdat[it];
G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
G4double CrossSection = 0.0 ;
G4double y = ymin - 0.5*dy ;
G4double yy = ymin - dy ;
G4double x = exp(y);
G4double fac = exp(dy);
G4double dx = exp(yy)*(fac - 1.0);
G4double c = log(maxPairEnergy/minPairEnergy);
for (G4int i=0 ; i<nbiny; i++)
{
y += dy ;
if(c > 0.0) {
x *= fac;
dx*= fac;
G4double ep = minPairEnergy*exp(c*x) ;
CrossSection += ep*dx*ComputeDMicroscopicCrossSection(
kineticEnergy, Z, ep);
}
ya[i] = y;
proba[iz][it][i] = CrossSection;
}
ya[nbiny]=ymax;
proba[iz][it][nbiny] = CrossSection;
}
}
samplingTablesAreFilled = true;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
vector<G4DynamicParticle*>* G4MuPairProductionModel::SampleSecondaries(
const G4MaterialCutsCouple* couple,
const G4DynamicParticle* aDynamicParticle,
G4double cut,
G4double tmax)
{
G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
G4double totalEnergy = kineticEnergy + particleMass ;
G4ParticleMomentum ParticleDirection = aDynamicParticle->GetMomentumDirection();
G4int it;
for(it=1; it<ntdat; it++) {if(kineticEnergy <= tdat[it]) break;}
if(it == ntdat) it--;
G4double dt = log(kineticEnergy/tdat[it-1])/log(tdat[it]/tdat[it-1]);
// select randomly one element constituing the material
G4int iymin = 0;
G4int iymax = nbiny-1;
const G4Element* anElement = SelectRandomAtom(kineticEnergy, dt, it, couple);
SetCurrentElement(anElement->GetZ());
G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
G4double maxEnergy = min(tmax, maxPairEnergy);
G4double minEnergy = min(maxEnergy, cut);
if( minEnergy > minPairEnergy)
{
G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
iymin = (G4int)((log(xc) - ymin)/dy);
if(iymin >= nbiny) iymin = nbiny-1;
xc = log(maxEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
iymax = (G4int)((log(xc) - ymin)/dy) + 1;
if(iymax >= nbiny) iymax = nbiny-1;
}
// sample e-e+ energy, pair energy first
G4int iz, iy;
for(iz=1; iz<nzdat; iz++) {if(currentZ <= zdat[iz]) break;}
if(iz == nzdat) iz--;
G4double dz = log(currentZ/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
G4double pmin = InterpolatedIntegralCrossSection(dt, dz, iz, it, iymin, currentZ);
G4double pmax = InterpolatedIntegralCrossSection(dt, dz, iz, it, iymax, currentZ);
G4double p = pmin+G4UniformRand()*(pmax - pmin);
// interpolate sampling vector;
G4double p1 = pmin;
G4double p2 = pmin;
for(iy=iymin+1; iy<=iymax; iy++) {
p1 = p2;
p2 = InterpolatedIntegralCrossSection(dt, dz, iz, it, iy, currentZ);
if(p <= p2) break;
}
G4double y = ya[iy-1] + dy*(p - p1)/(p2 - p1);
G4double PairEnergy = minPairEnergy*exp(exp(y)*log(maxPairEnergy/minPairEnergy));
if(PairEnergy < minEnergy) PairEnergy = minEnergy;
if(PairEnergy > maxEnergy) PairEnergy = maxEnergy;
// sample r=(E+-E-)/PairEnergy ( uniformly .....)
G4double rmax =
(1.-6.*particleMass*particleMass/(totalEnergy*(totalEnergy-PairEnergy)))
*sqrt(1.-minPairEnergy/PairEnergy);
G4double r = rmax * (-1.+2.*G4UniformRand()) ;
// compute energies from PairEnergy,r
G4double ElectronEnergy = (1.-r)*PairEnergy*0.5;
G4double PositronEnergy = PairEnergy - ElectronEnergy;
// angles of the emitted particles ( Z - axis along the parent particle)
// (mean theta for the moment)
G4double Teta = electron_mass_c2/totalEnergy ;
G4double Phi = twopi * G4UniformRand() ;
G4double dirx = sin(Teta)*cos(Phi);
G4double diry = sin(Teta)*sin(Phi);
G4double dirz = cos(Teta) ;
//G4double finalPx,finalPy,finalPz ;
G4double ElectKineEnergy = ElectronEnergy - electron_mass_c2 ;
G4ThreeVector ElectDirection ( dirx, diry, dirz );
ElectDirection.rotateUz(ParticleDirection);
// create G4DynamicParticle object for the particle1
G4DynamicParticle* aParticle1= new G4DynamicParticle(theElectron,
ElectDirection,
ElectKineEnergy);
G4double PositKineEnergy = PositronEnergy - electron_mass_c2 ;
G4ThreeVector PositDirection ( -dirx, -diry, dirz );
PositDirection.rotateUz(ParticleDirection);
// create G4DynamicParticle object for the particle2
G4DynamicParticle* aParticle2= new G4DynamicParticle(thePositron,
PositDirection,
PositKineEnergy);
// primary change
kineticEnergy -= (ElectKineEnergy + PositKineEnergy + 2.0*electron_mass_c2);
fParticleChange->SetProposedKineticEnergy(kineticEnergy);
vector<G4DynamicParticle*>* vdp = new vector<G4DynamicParticle*>;
vdp->push_back(aParticle1);
vdp->push_back(aParticle2);
return vdp;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
const G4Element* G4MuPairProductionModel::SelectRandomAtom(
G4double kinEnergy, G4double dt, G4int it,
const G4MaterialCutsCouple* couple)
{
// select randomly 1 element within the material
const G4Material* material = couple->GetMaterial();
size_t nElements = material->GetNumberOfElements();
const G4ElementVector* theElementVector = material->GetElementVector();
if (nElements == 1) return (*theElementVector)[0];
if(nElements > nmaxElements) {
nmaxElements = nElements;
partialSum.resize(nmaxElements);
}
const G4double* theAtomNumDensityVector=material->GetAtomicNumDensityVector();
G4double sum = 0.0;
size_t i;
for (i=0; i<nElements; i++) {
G4double Z = ((*theElementVector)[i])->GetZ();
SetCurrentElement(Z);
G4double maxPairEnergy = MaxSecondaryEnergy(particle,kinEnergy);
G4int iz;
for(iz=1; iz<nzdat; iz++) {if(Z <= zdat[iz]) break;}
if(iz == nzdat) iz--;
G4double dz = log(Z/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
G4double xc = log(kinEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
G4int iy = (G4int)((log(xc) - ymin)/dy);
if(iy >= nbiny) iy = nbiny-1;
G4double sigtot = InterpolatedIntegralCrossSection(dt, dz, iz, it, nbiny, Z);
G4double sigcut = InterpolatedIntegralCrossSection(dt, dz, iz, it, iy, Z);
sum += (sigtot - sigcut)*theAtomNumDensityVector[i];
partialSum[i] = sum;
}
G4double rval = G4UniformRand()*sum;
for (i=0; i<nElements; i++) {if(rval<=partialSum[i]) break;}
return (*theElementVector)[i];
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
Reference in New Issue View Git Blame Copy Permalink