fanoCavity2/src/MyMollerBhabhaModel.cc

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0026 /// \file medical/fanoCavity2/src/MyMollerBhabhaModel.cc
0027 /// \brief Implementation of the MyMollerBhabhaModel class
0028 //
0029 //
0030 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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0032
0033 #include "MyMollerBhabhaModel.hh"
0034
0035 #include "G4PhysicalConstants.hh"
0036 #include "G4SystemOfUnits.hh"
0037
0038 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0039
0040 using namespace std;
0041
0042 MyMollerBhabhaModel::MyMollerBhabhaModel(const G4ParticleDefinition* p, const G4String& nam)
0043   : G4MollerBhabhaModel(p, nam)
0044 {}
0045
0046 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0047
0048 MyMollerBhabhaModel::~MyMollerBhabhaModel() {}
0049
0050 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0051
0052 G4double MyMollerBhabhaModel::ComputeDEDXPerVolume(const G4Material* material,
0053                                                    const G4ParticleDefinition* p,
0054                                                    G4double kineticEnergy, G4double cutEnergy)
0055 {
0056   if (!particle) SetParticle(p);
0057   // calculate the dE/dx due to the ionization by Seltzer-Berger formula
0058
0059   G4double electronDensity = material->GetElectronDensity();
0060   G4double Zeff = electronDensity / material->GetTotNbOfAtomsPerVolume();
0061   G4double th = 0.25 * sqrt(Zeff) * keV;
0062   G4double tkin = kineticEnergy;
0063   G4bool lowEnergy = false;
0064   if (kineticEnergy < th) {
0065     tkin = th;
0066     lowEnergy = true;
0067   }
0068   G4double tau = tkin / electron_mass_c2;
0069   G4double gam = tau + 1.0;
0070   G4double gamma2 = gam * gam;
0071   G4double beta2 = 1. - 1. / gamma2;
0072   // G4double bg2   = beta2*gamma2;
0073
0074   G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
0075   eexc /= electron_mass_c2;
0076   G4double eexc2 = eexc * eexc;
0077
0078   G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin)) / electron_mass_c2;
0079   G4double dedx;
0080
0081   // electron
0082   if (isElectron) {
0083     dedx = log(2.0 * (tau + 2.0) / eexc2) - 1.0 - beta2 + log((tau - d) * d) + tau / (tau - d)
0084            + (0.5 * d * d + (2.0 * tau + 1.) * log(1. - d / tau)) / gamma2;
0085
0086     // positron
0087   }
0088   else {
0089     G4double d2 = d * d * 0.5;
0090     G4double d3 = d2 * d / 1.5;
0091     G4double d4 = d3 * d * 3.75;
0092     G4double y = 1.0 / (1.0 + gam);
0093     dedx =
0094       log(2.0 * (tau + 2.0) / eexc2) + log(tau * d)
0095       - beta2 * (tau + 2.0 * d - y * (3.0 * d2 + y * (d - d3 + y * (d2 - tau * d3 + d4)))) / tau;
0096   }
0097
0098   // do not apply density correction
0099   // G4double cden  = material->GetIonisation()->GetCdensity();
0100   // G4double mden  = material->GetIonisation()->GetMdensity();
0101   // G4double aden  = material->GetIonisation()->GetAdensity();
0102   // G4double x0den = material->GetIonisation()->GetX0density();
0103   // G4double x1den = material->GetIonisation()->GetX1density();
0104   // G4double x     = log(bg2)/twoln10;
0105
0106   // if (x >= x0den) {
0107   //   dedx -= twoln10*x - cden;
0108   //   if (x < x1den) dedx -= aden*pow(x1den-x, mden);
0109   // }
0110
0111   // now you can compute the total ionization loss
0112   dedx *= twopi_mc2_rcl2 * electronDensity / beta2;
0113   if (dedx < 0.0) dedx = 0.0;
0114
0115   // lowenergy extrapolation
0116
0117   if (lowEnergy) {
0118     if (kineticEnergy >= lowLimit)
0119       dedx *= sqrt(tkin / kineticEnergy);
0120     else
0121       dedx *= sqrt(tkin * kineticEnergy) / lowLimit;
0122   }
0123   return dedx;
0124 }
0125
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