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geant4/source/processes/electromagnetic/standard/src/G4BetheHeitler5DModel.cc
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Gabriele Cosmo 8c87fe78c4 Import Geant4 10.6.1 source tree
2020-02-14 15:32:52 +01:00

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//
// ********************************************************************
// * License and Disclaimer *
// * *
// * The Geant4 software is copyright of the Copyright Holders of *
// * the Geant4 Collaboration. It is provided under the terms and *
// * conditions of the Geant4 Software License, included in the file *
// * LICENSE and available at http://cern.ch/geant4/license . These *
// * include a list of copyright holders. *
// * *
// * 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. Please see the license in the file LICENSE and URL above *
// * for the full disclaimer and the limitation of liability. *
// * *
// * This code implementation is the result of the scientific and *
// * technical work of the GEANT4 collaboration. *
// * By using, copying, modifying or distributing the software (or *
// * any work based on the software) you agree to acknowledge its *
// * use in resulting scientific publications, and indicate your *
// * acceptance of all terms of the Geant4 Software license. *
// ********************************************************************
//
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name: G4BetheHeitler5DModel.cc
//
// Authors:
// Igor Semeniouk and Denis Bernard,
// LLR, Ecole polytechnique & CNRS/IN2P3, 91128 Palaiseau, France
//
// Acknowledgement of the support of the French National Research Agency
// (ANR-13-BS05-0002).
//
// Reference: Nucl. Instrum. Meth. A 899 (2018) 85 (arXiv:1802.08253 [hep-ph])
// Nucl. Instrum. Meth., A 936 (2019) 290
//
// Class Description:
//
// Generates the conversion of a high-energy photon to an e+e- pair, either in the field of an
// atomic electron (triplet) or nucleus (nuclear).
// Samples the five-dimensional (5D) differential cross-section analytical expression:
// . Non polarized conversion:
// H.A. Bethe, W. Heitler, Proc. R. Soc. Lond. Ser. A 146 (1934) 83.
// . Polarized conversion:
// T. H. Berlin and L. Madansky, Phys. Rev. 78 (1950) 623,
// M. M. May, Phys. Rev. 84 (1951) 265,
// J. M. Jauch and F. Rohrlich, The theory of photons and electrons, 1976.
//
// All the above expressions are named "Bethe-Heitler" here.
//
// Bethe & Heitler, put in Feynman diagram parlance, compute only the two dominant diagrams of
// the first order Born development, which is an excellent approximation for nuclear conversion
// and for high-energy triplet conversion.
//
// Only the linear polarisation of the incoming photon takes part in these expressions.
// The circular polarisation of the incoming photon does not (take part) and no polarisation
// is transfered to the final leptons.
//
// In case conversion takes place in the field of an isolated nucleus or electron, the bare
// Bethe-Heitler expression is used.
//
// In case the nucleus or the electron are part of an atom, the screening of the target field
// by the other electrons of the atom is described by a simple form factor, function of q2:
// . nuclear: N.F. Mott, H.S.W. Massey, The Theory of Atomic Collisions, 1934.
// . triplet: J.A. Wheeler and W.E. Lamb, Phys. Rev. 55 (1939) 858.
//
// The nuclear form factor that affects the probability of very large-q2 events, is not considered.
//
// In principle the code is valid from threshold, that is from 2 * m_e c^2 for nuclear and from
// 4 * m_e c^2 for triplet, up to infinity, while in pratice the divergence of the differential
// cross section at small q2 and, at high-energy, at small polar angle, make it break down at
// some point that depends on machine precision.
//
// Very-high-energy (above a few tens of TeV) LPM suppression effects in the normalized differential
// cross-section are not considered.
//
// The 5D differential cross section is sampled without any high-energy nor small
// angle approximation(s).
// The generation is strictly energy-momentum conserving when all particles in the final state
// are taken into account, that is, including the recoiling target.
// (In contrast with the BH expressions taken at face values, for which the electron energy is
// taken to be EMinus = GammaEnergy - EPlus)
//
// Tests include the examination of 1D distributions: see TestEm15
//
// Total cross sections are not computed (we inherit from other classes).
// We just convert a photon on a target when asked to do so.
//
// Pure nuclear, pure triplet and 1/Z triplet/nuclear mixture can be generated.
//
// -------------------------------------------------------------------
#include "G4BetheHeitler5DModel.hh"
#include "G4EmParameters.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4Electron.hh"
#include "G4Positron.hh"
#include "G4Gamma.hh"
#include "G4MuonPlus.hh"
#include "G4MuonMinus.hh"
#include "G4IonTable.hh"
#include "G4NucleiProperties.hh"
#include "Randomize.hh"
#include "G4ParticleChangeForGamma.hh"
#include "G4Pow.hh"
#include "G4Log.hh"
#include "G4Exp.hh"
#include "G4LorentzVector.hh"
#include "G4ThreeVector.hh"
#include "G4RotationMatrix.hh"
#include <cassert>
// // Q : Use enum G4EmProcessSubType hire ?
// enum G45DConversionMode
// {
// kEPair, kMuPair
// };
const G4int kEPair = 0;
const G4int kMuPair = 1;
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4BetheHeitler5DModel::G4BetheHeitler5DModel(const G4ParticleDefinition* pd,
const G4String& nam)
: G4PairProductionRelModel(pd, nam),fVerbose(1),fConversionType(0),
iraw(false),
fLepton1(G4Electron::Definition()),fLepton2(G4Positron::Definition()),
fConvMode(kEPair),
fTheMuPlus(G4MuonPlus::Definition()),fTheMuMinus(G4MuonMinus::Definition())
{
theIonTable = G4IonTable::GetIonTable();
//Q: Do we need this on Model
SetLowEnergyLimit(2*fTheElectron->GetPDGMass());
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4BetheHeitler5DModel::~G4BetheHeitler5DModel()
{}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
void G4BetheHeitler5DModel::Initialise(const G4ParticleDefinition* part,
const G4DataVector& vec)
{
G4PairProductionRelModel::Initialise(part, vec);
G4EmParameters* theManager = G4EmParameters::Instance();
// place to initialise model parameters
// Verbosity levels: ( Can redefine as needed, but some consideration )
// 0 = nothing
// > 2 print results
// > 3 print rejection warning from transformation (fix bug from gammaray .. )
// > 4 print photon direction & polarisation
fVerbose = theManager->Verbose();
fConversionType = theManager->GetConversionType();
//////////////////////////////////////////////////////////////
// iraw :
// true : isolated electron or nucleus.
// false : inside atom -> screening form factor
iraw = theManager->OnIsolated();
// G4cout << "BH5DModel::Initialise verbose " << fVerbose
// << " isolated " << iraw << " ctype "<< fConversionType << G4endl;
//Q: Do we need this on Model
// The Leptons defined via SetLeptonPair(..) method
SetLowEnergyLimit(2*CLHEP::electron_mass_c2);
if (fConvMode == kEPair) {
assert(fLepton1->GetPDGEncoding() == fTheElectron->GetPDGEncoding()) ;
if (fVerbose > 3)
G4cout << "BH5DModel::Initialise conversion to e+ e-" << G4endl;
}
if (fConvMode == kMuPair) {
assert(fLepton1->GetPDGEncoding() == fTheMuMinus->GetPDGEncoding()) ;
if (fVerbose > 3)
G4cout << "BH5DModel::Initialise conversion to mu+ mu-" << G4endl;
}
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
void G4BetheHeitler5DModel::SetLeptonPair(const G4ParticleDefinition* p1,
const G4ParticleDefinition* p2)
{
// Lepton1 - nagative charged particle
if ( p1->GetPDGEncoding() < 0 ){
if ( p1->GetPDGEncoding() ==
G4Positron::Definition()->GetPDGEncoding() ) {
SetConversionMode(kEPair);
fLepton1 = p2;
fLepton2 = p1;
// if (fVerbose)
G4cout << "G4BetheHeitler5DModel::SetLeptonPair conversion to e+ e-"
<< G4endl;
} else if ( p1->GetPDGEncoding() ==
G4MuonPlus::Definition()->GetPDGEncoding() ) {
SetConversionMode(kMuPair);
fLepton1 = p2;
fLepton2 = p1;
// if (fVerbose)
G4cout << "G4BetheHeitler5DModel::SetLeptonPair conversion to mu+ mu-"
<< G4endl;
} else {
// Exception
G4ExceptionDescription ed;
ed << "Model not applicable to particle(s) "
<< p1->GetParticleName() << ", "
<< p2->GetParticleName();
G4Exception("G4BetheHeitler5DModel::SetLeptonPair","em0002",
FatalException, ed);
}
} else {
if ( p1->GetPDGEncoding() ==
G4Electron::Definition()->GetPDGEncoding() ) {
SetConversionMode(kEPair);
fLepton1 = p1;
fLepton2 = p2;
// if (fVerbose)
G4cout << "G4BetheHeitler5DModel::SetLeptonPair conversion to e+ e-"
<< G4endl;
} else if ( p1->GetPDGEncoding() ==
G4MuonMinus::Definition()->GetPDGEncoding() ) {
SetConversionMode(kMuPair);
fLepton1 = p1;
fLepton2 = p2;
// if (fVerbose)
G4cout << "G4BetheHeitler5DModel::SetLeptonPair conversion to mu+ mu-"
<< G4endl;
} else {
// Exception
G4ExceptionDescription ed;
ed << "Model not applicable to particle(s) "
<< p1->GetParticleName() << ", "
<< p2->GetParticleName();
G4Exception("G4BetheHeitler5DModel::SetLeptonPair","em0002",
FatalException, ed);
}
}
if ( fLepton1->GetPDGEncoding() != fLepton2->GetAntiPDGEncoding() ) {
G4Exception("G4BetheHeitler5DModel::SetLeptonPair","em0007",
FatalErrorInArgument, "pair must be particle, antiparticle ");
G4cerr << "BH5DModel::SetLeptonPair BAD paricle/anti particle pair"
<< fLepton1->GetParticleName() << ", "
<< fLepton2->GetParticleName() << G4endl;
}
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4BetheHeitler5DModel::MaxDiffCrossSection(const G4double* par,
G4double Z,
G4double e,
G4double loge) const
{
const G4double Q = e/par[9];
return par[0] * G4Exp((par[2]+loge*par[4])*loge)
/ (par[1]+ G4Exp(par[3]*loge)+G4Exp(par[5]*loge))
* (1+par[7]*G4Exp(par[8]*G4Log(Z))*Q/(1+Q));
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
void
G4BetheHeitler5DModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
const G4MaterialCutsCouple* couple,
const G4DynamicParticle* aDynamicGamma,
G4double, G4double)
{
// MeV
static const G4double ElectronMass = CLHEP::electron_mass_c2;
const G4double LeptonMass = fLepton1->GetPDGMass();
const G4double LeptonMass2 = LeptonMass*LeptonMass;
static const G4double alpha0 = CLHEP::fine_structure_const;
// mm
static const G4double r0 = CLHEP::classic_electr_radius;
// mbarn
static const G4double r02 = r0*r0*1.e+25;
static const G4double twoPi = CLHEP::twopi;
static const G4double factor = alpha0 * r02 / (twoPi*twoPi);
// static const G4double factor1 = pow((6.0 * pi),(1.0/3.0))/(8.*alpha0*ElectronMass);
static const G4double factor1 = 2.66134007899/(8.*alpha0*ElectronMass);
//
G4double PairInvMassMin = 2.*LeptonMass;
G4double TrThreshold = 2.0 * ( (LeptonMass2)/ElectronMass + LeptonMass);
//
static const G4double nu[2][10] = {
//electron
{ 0.0227436, 0.0582046, 3.0322675, 2.8275065, -0.0034004,
1.1212766, 1.8989468, 68.3492750, 0.0211186, 14.4},
//muon
{0.67810E-06, 0.86037E+05, 2.0008395, 1.6739719, -0.0057279,
1.4222, 0.0, 263230.0, 0.0521, 51.1338}
};
static const G4double tr[2][10] = {
//electron
{ 0.0332350, 4.3942537, 2.8515925, 2.6351695, -0.0031510,
1.5737305, 1.8104647, 20.6434021, -0.0272586, 28.9},
//muon
{0.10382E-03, 0.14408E+17, 4.1368679, 3.2662121, -0.0163091,
0.0000, 0.0, 0.0, 0.0000, 1.0000}
};
//
static const G4double para[2][3][2] = {
//electron
{ {11., -16.},{-1.17, -2.95},{-2., -0.5} },
//muon
{ {17.5, 1.},{-1.17, -2.95},{2., 6.} }
};
//
static const G4double correctionIndex = 1.4;
//
const G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
// Protection, Will not be true tot cross section = 0
if ( GammaEnergy <= PairInvMassMin) { return; }
const G4double GammaEnergy2 = GammaEnergy*GammaEnergy;
//////////////////////////////////////////////////////////////
const G4ParticleMomentum GammaDirection =
aDynamicGamma->GetMomentumDirection();
G4ThreeVector GammaPolarization = aDynamicGamma->GetPolarization();
// The protection polarization perpendicular to the direction vector,
// as it done in G4LivermorePolarizedGammaConversionModel,
// assuming Direction is unitary vector
// (projection to plane) p_proj = p - (p o d)/(d o d) x d
if ( GammaPolarization.howOrthogonal(GammaDirection) != 0) {
GammaPolarization -= GammaPolarization.dot(GammaDirection) * GammaDirection;
}
// End of Protection
//
const G4double GammaPolarizationMag = GammaPolarization.mag();
//////////////////////////////////////////////////////////////
// target element
// select randomly one element constituting the material
const G4Element* anElement = SelectTargetAtom(couple, fTheGamma, GammaEnergy,
aDynamicGamma->GetLogKineticEnergy() );
// Atomic number
const G4int Z = anElement->GetZasInt();
const G4int A = SelectIsotopeNumber(anElement);
const G4double iZ13 = 1./anElement->GetIonisation()->GetZ3();
const G4double targetMass = G4NucleiProperties::GetNuclearMass(A, Z);
const G4double NuThreshold = 2.0 * ( (LeptonMass2)/targetMass + LeptonMass);
// No conversion possible below nuclear threshold
if ( GammaEnergy <= NuThreshold) { return; }
CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
// itriplet : true -- triplet, false -- nuclear.
G4bool itriplet = false;
if (fConversionType == 1) {
itriplet = false;
} else if (fConversionType == 2) {
itriplet = true;
if ( GammaEnergy <= TrThreshold ) return;
} else if ( GammaEnergy > TrThreshold ) {
// choose triplet or nuclear from a triplet/nuclear=1/Z
// total cross section ratio.
// approximate at low energies !
if(rndmEngine->flat()*(Z+1) < 1.) {
itriplet = true;
}
}
//
const G4double RecoilMass = itriplet ? ElectronMass : targetMass;
const G4double RecoilMass2 = RecoilMass*RecoilMass;
const G4double sCMS = 2.*RecoilMass*GammaEnergy + RecoilMass2;
const G4double sCMSPlusRM2 = sCMS + RecoilMass2;
const G4double sqrts = std::sqrt(sCMS);
const G4double isqrts2 = 1./(2.*sqrts);
//
const G4double PairInvMassMax = sqrts-RecoilMass;
const G4double PairInvMassRange = PairInvMassMax/PairInvMassMin;
const G4double lnPairInvMassRange = G4Log(PairInvMassRange);
// initial state. Defines z axis of "0" frame as along photon propagation.
// Since CMS(0., 0., GammaEnergy, GammaEnergy+RecoilMass) set some constants
const G4double betaCMS = G4LorentzVector(0.0,0.0,GammaEnergy,GammaEnergy+RecoilMass).beta();
// maximum value of pdf
const G4double EffectiveZ = iraw ? 0.5 : Z;
const G4double Threshold = itriplet ? TrThreshold : NuThreshold;
const G4double AvailableEnergy = GammaEnergy - Threshold;
const G4double LogAvailableEnergy = G4Log(AvailableEnergy);
//
const G4double MaxDiffCross = itriplet
? MaxDiffCrossSection(tr[fConvMode],
EffectiveZ, AvailableEnergy, LogAvailableEnergy)
: MaxDiffCrossSection(nu[fConvMode],
EffectiveZ, AvailableEnergy, LogAvailableEnergy);
//
// 50% safety marging factor
const G4double ymax = 1.5 * MaxDiffCross;
// x1 bounds
const G4double xu1 = (LogAvailableEnergy > para[fConvMode][2][0])
? para[fConvMode][0][0] +
para[fConvMode][1][0]*LogAvailableEnergy
: para[fConvMode][0][0] +
para[fConvMode][2][0]*para[fConvMode][1][0];
const G4double xl1 = (LogAvailableEnergy > para[fConvMode][2][1])
? para[fConvMode][0][1] +
para[fConvMode][1][1]*LogAvailableEnergy
: para[fConvMode][0][1] +
para[fConvMode][2][1]*para[fConvMode][1][1];
//
G4LorentzVector Recoil;
G4LorentzVector LeptonPlus;
G4LorentzVector LeptonMinus;
G4double pdf = 0.;
G4double rndmv6[6];
// START Sampling
do {
rndmEngine->flatArray(6, rndmv6);
//////////////////////////////////////////////////
// pdf pow(x,c) with c = 1.4
// integral y = pow(x,(c+1))/(c+1) @ x = 1 => y = 1 /(1+c)
// invCdf exp( log(y /* *( c + 1.0 )/ (c + 1.0 ) */ ) /( c + 1.0) )
//////////////////////////////////////////////////
const G4double X1 =
G4Exp(G4Log(rndmv6[0])/(correctionIndex + 1.0));
const G4double x0 = G4Exp(xl1 + (xu1 - xl1)*rndmv6[1]);
const G4double dum0 = 1./(1.+x0);
const G4double cosTheta = (x0-1.)*dum0;
const G4double sinTheta = std::sqrt(4.*x0)*dum0;
const G4double PairInvMass = PairInvMassMin*G4Exp(X1*X1*lnPairInvMassRange);
// G4double rndmv3[3];
// rndmEngine->flatArray(3, rndmv3);
// cos and sin theta-lepton
const G4double cosThetaLept = std::cos(pi*rndmv6[2]);
// sin(ThetaLept) is always in [0,+1] if ThetaLept is in [0,pi]
const G4double sinThetaLept = std::sqrt((1.-cosThetaLept)*(1.+cosThetaLept));
// cos and sin phi-lepton
const G4double cosPhiLept = std::cos(twoPi*rndmv6[3]-pi);
// sin(PhiLept) is in [-1,0] if PhiLept in [-pi,0) and
// is in [0,+1] if PhiLept in [0,+pi]
const G4double sinPhiLept = std::copysign(std::sqrt((1.-cosPhiLept)*(1.+cosPhiLept)),rndmv6[3]-0.5);
// cos and sin phi
const G4double cosPhi = std::cos(twoPi*rndmv6[4]-pi);
const G4double sinPhi = std::copysign(std::sqrt((1.-cosPhi)*(1.+cosPhi)),rndmv6[4]-0.5);
//////////////////////////////////////////////////
// frames:
// 3 : the laboratory Lorentz frame, Geant4 axes definition
// 0 : the laboratory Lorentz frame, axes along photon direction and polarisation
// 1 : the center-of-mass Lorentz frame
// 2 : the pair Lorentz frame
//////////////////////////////////////////////////
// in the center-of-mass frame
const G4double RecEnergyCMS = (sCMSPlusRM2-PairInvMass*PairInvMass)*isqrts2;
const G4double LeptonEnergy2 = PairInvMass*0.5;
// New way of calucaltion thePRecoil to avoid underflow
G4double abp = std::max((2.0*GammaEnergy*RecoilMass -
PairInvMass*PairInvMass + 2.0*PairInvMass*RecoilMass)*
(2.0*GammaEnergy*RecoilMass -
PairInvMass*PairInvMass - 2.0*PairInvMass*RecoilMass),0.0);
G4double thePRecoil = std::sqrt(abp) * isqrts2;
// back to the center-of-mass frame
Recoil.set( thePRecoil*sinTheta*cosPhi,
thePRecoil*sinTheta*sinPhi,
thePRecoil*cosTheta,
RecEnergyCMS);
// in the pair frame
const G4double thePLepton = std::sqrt( (LeptonEnergy2-LeptonMass)
*(LeptonEnergy2+LeptonMass));
LeptonPlus.set(thePLepton*sinThetaLept*cosPhiLept,
thePLepton*sinThetaLept*sinPhiLept,
thePLepton*cosThetaLept,
LeptonEnergy2);
LeptonMinus.set(-LeptonPlus.x(),
-LeptonPlus.y(),
-LeptonPlus.z(),
LeptonEnergy2);
// Normalisation of final state phase space:
// Section 47 of Particle Data Group, Chin. Phys. C, 40, 100001 (2016)
// const G4double Norme = Recoil1.vect().mag() * LeptonPlus2.vect().mag();
const G4double Norme = Recoil.vect().mag() * LeptonPlus.vect().mag();
// e+, e- to CMS frame from pair frame
// boost vector from Pair to CMS
const G4ThreeVector pair2cms =
G4LorentzVector( -Recoil.x(), -Recoil.y(), -Recoil.z(),
sqrts-RecEnergyCMS).boostVector();
LeptonPlus.boost(pair2cms);
LeptonMinus.boost(pair2cms);
// back to the laboratory frame (make use of the CMS(0,0,Eg,Eg+RM)) form
Recoil.boostZ(betaCMS);
LeptonPlus.boostZ(betaCMS);
LeptonMinus.boostZ(betaCMS);
// Jacobian factors
const G4double Jacob0 = x0*dum0*dum0;
const G4double Jacob1 = 2.*X1*lnPairInvMassRange*PairInvMass;
const G4double Jacob2 = std::abs(sinThetaLept);
const G4double EPlus = LeptonPlus.t();
const G4double PPlus = LeptonPlus.vect().mag();
const G4double sinThetaPlus = LeptonPlus.vect().perp()/PPlus;
const G4double cosThetaPlus = LeptonPlus.vect().cosTheta();
const G4double pPX = LeptonPlus.x();
const G4double pPY = LeptonPlus.y();
const G4double dum1 = 1./std::sqrt( pPX*pPX + pPY*pPY );
const G4double cosPhiPlus = pPX*dum1;
const G4double sinPhiPlus = pPY*dum1;
// denominators:
// the two cancelling leading terms for forward emission at high energy, removed
const G4double elMassCTP = LeptonMass*cosThetaPlus;
const G4double ePlusSTP = EPlus*sinThetaPlus;
const G4double DPlus = (elMassCTP*elMassCTP + ePlusSTP*ePlusSTP)
/(EPlus + PPlus*cosThetaPlus);
const G4double EMinus = LeptonMinus.t();
const G4double PMinus = LeptonMinus.vect().mag();
const G4double sinThetaMinus = LeptonMinus.vect().perp()/PMinus;
const G4double cosThetaMinus = LeptonMinus.vect().cosTheta();
const G4double ePX = LeptonMinus.x();
const G4double ePY = LeptonMinus.y();
const G4double dum2 = 1./std::sqrt( ePX*ePX + ePY*ePY );
const G4double cosPhiMinus = ePX*dum2;
const G4double sinPhiMinus = ePY*dum2;
const G4double elMassCTM = LeptonMass*cosThetaMinus;
const G4double eMinSTM = EMinus*sinThetaMinus;
const G4double DMinus = (elMassCTM*elMassCTM + eMinSTM*eMinSTM)
/(EMinus + PMinus*cosThetaMinus);
// cos(phiMinus-PhiPlus)
const G4double cosdPhi = cosPhiPlus*cosPhiMinus + sinPhiPlus*sinPhiMinus;
const G4double PRec = Recoil.vect().mag();
const G4double q2 = PRec*PRec;
const G4double BigPhi = -LeptonMass2 / (GammaEnergy*GammaEnergy2 * q2*q2);
G4double FormFactor = 1.;
if (!iraw) {
if (itriplet) {
const G4double qun = factor1*iZ13*iZ13;
const G4double nun = qun * PRec;
if (nun < 1.) {
FormFactor = (nun < 0.01) ? (13.8-55.4*std::sqrt(nun))*nun
: std::sqrt(1-(nun-1)*(nun-1));
} // else FormFactor = 1 by default
} else {
const G4double dum3 = 217.*PRec*iZ13;
const G4double AFF = 1./(1. + dum3*dum3);
FormFactor = (1.-AFF)*(1-AFF);
}
} // else FormFactor = 1 by default
G4double betheheitler;
if (GammaPolarizationMag==0.) {
const G4double pPlusSTP = PPlus*sinThetaPlus;
const G4double pMinusSTM = PMinus*sinThetaMinus;
const G4double pPlusSTPperDP = pPlusSTP/DPlus;
const G4double pMinusSTMperDM = pMinusSTM/DMinus;
const G4double dunpol = BigPhi*(
pPlusSTPperDP *pPlusSTPperDP *(4.*EMinus*EMinus-q2)
+ pMinusSTMperDM*pMinusSTMperDM*(4.*EPlus*EPlus - q2)
+ 2.*pPlusSTPperDP*pMinusSTMperDM*cosdPhi
*(4.*EPlus*EMinus + q2 - 2.*GammaEnergy2)
- 2.*GammaEnergy2*(pPlusSTP*pPlusSTP+pMinusSTM*pMinusSTM)/(DMinus*DPlus));
betheheitler = dunpol * factor;
} else {
const G4double pPlusSTP = PPlus*sinThetaPlus;
const G4double pMinusSTM = PMinus*sinThetaMinus;
const G4double pPlusSTPCPPperDP = pPlusSTP*cosPhiPlus/DPlus;
const G4double pMinusSTMCPMperDM = pMinusSTM*cosPhiMinus/DMinus;
const G4double caa = 2.*(EPlus*pMinusSTMCPMperDM+EMinus*pPlusSTPCPPperDP);
const G4double cbb = pMinusSTMCPMperDM-pPlusSTPCPPperDP;
const G4double ccc = (pPlusSTP*pPlusSTP + pMinusSTM*pMinusSTM
+2.*pPlusSTP*pMinusSTM*cosdPhi)/ (DMinus*DPlus);
const G4double dtot= 2.*BigPhi*( caa*caa - q2*cbb*cbb - GammaEnergy2*ccc);
betheheitler = dtot * factor;
}
//
const G4double cross = Norme * Jacob0 * Jacob1 * Jacob2 * betheheitler
* FormFactor * RecoilMass / sqrts;
pdf = cross * (xu1 - xl1) / G4Exp(correctionIndex*G4Log(X1)); // cond1;
} while ( pdf < ymax * rndmv6[5] );
// END of Sampling
if ( fVerbose > 2 ) {
G4double recul = std::sqrt(Recoil.x()*Recoil.x()+Recoil.y()*Recoil.y()
+Recoil.z()*Recoil.z());
G4cout << "BetheHeitler5DModel GammaEnergy= " << GammaEnergy
<< " PDF= " << pdf << " ymax= " << ymax
<< " recul= " << recul << G4endl;
}
// back to Geant4 system
if ( fVerbose > 4 ) {
G4cout << "BetheHeitler5DModel GammaDirection " << GammaDirection << G4endl;
G4cout << "BetheHeitler5DModel GammaPolarization " << GammaPolarization << G4endl;
G4cout << "BetheHeitler5DModel GammaEnergy " << GammaEnergy << G4endl;
G4cout << "BetheHeitler5DModel Conv "
<< (itriplet ? "triplet" : "nucl") << G4endl;
}
if (GammaPolarizationMag == 0.0) {
// set polarization axis orthohonal to direction
GammaPolarization = GammaDirection.orthogonal().unit();
} else {
// GammaPolarization not a unit vector
GammaPolarization /= GammaPolarizationMag;
}
// The unit norm vector that is orthogonal to the two others
G4ThreeVector yGrec = GammaDirection.cross(GammaPolarization);
// rotation from gamma ref. sys. to World
G4RotationMatrix GtoW(GammaPolarization,yGrec,GammaDirection);
Recoil.transform(GtoW);
LeptonPlus.transform(GtoW);
LeptonMinus.transform(GtoW);
if ( fVerbose > 2 ) {
G4cout << "BetheHeitler5DModel Recoil " << Recoil.x() << " " << Recoil.y() << " " << Recoil.z()
<< " " << Recoil.t() << " " << G4endl;
G4cout << "BetheHeitler5DModel LeptonPlus " << LeptonPlus.x() << " " << LeptonPlus.y() << " "
<< LeptonPlus.z() << " " << LeptonPlus.t() << " " << G4endl;
G4cout << "BetheHeitler5DModel LeptonMinus " << LeptonMinus.x() << " " << LeptonMinus.y() << " "
<< LeptonMinus.z() << " " << LeptonMinus.t() << " " << G4endl;
}
// Create secondaries
G4DynamicParticle* aParticle1 = new G4DynamicParticle(fLepton1,LeptonMinus);
G4DynamicParticle* aParticle2 = new G4DynamicParticle(fLepton2,LeptonPlus);
// create G4DynamicParticle object for the particle3 ( recoil )
G4ParticleDefinition* RecoilPart;
if (itriplet) {
// triplet
RecoilPart = fTheElectron;
} else{
RecoilPart = theIonTable->GetIon(Z, A, 0);
}
G4DynamicParticle* aParticle3 = new G4DynamicParticle(RecoilPart,Recoil);
// Fill output vector
fvect->push_back(aParticle1);
fvect->push_back(aParticle2);
fvect->push_back(aParticle3);
// kill incident photon
fParticleChange->SetProposedKineticEnergy(0.);
fParticleChange->ProposeTrackStatus(fStopAndKill);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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