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25 //
26 /// \file medical/fanoCavity2/src/MyMollerBhabhaModel.cc
27 /// \brief Implementation of the MyMollerBhabhaModel class
28 //
29 //
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32
33 #include "MyMollerBhabhaModel.hh"
34
35 #include "G4PhysicalConstants.hh"
36 #include "G4SystemOfUnits.hh"
37
38 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
39
40 using namespace std;
41
42 MyMollerBhabhaModel::MyMollerBhabhaModel(const G4ParticleDefinition* p, const G4String& nam)
43 : G4MollerBhabhaModel(p, nam)
44 {}
45
46 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
47
48 MyMollerBhabhaModel::~MyMollerBhabhaModel() {}
49
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51
52 G4double MyMollerBhabhaModel::ComputeDEDXPerVolume(const G4Material* material,
53 const G4ParticleDefinition* p,
54 G4double kineticEnergy, G4double cutEnergy)
55 {
56 if (!particle) SetParticle(p);
57 // calculate the dE/dx due to the ionization by Seltzer-Berger formula
58
59 G4double electronDensity = material->GetElectronDensity();
60 G4double Zeff = electronDensity / material->GetTotNbOfAtomsPerVolume();
61 G4double th = 0.25 * sqrt(Zeff) * keV;
62 G4double tkin = kineticEnergy;
63 G4bool lowEnergy = false;
64 if (kineticEnergy < th) {
65 tkin = th;
66 lowEnergy = true;
67 }
68 G4double tau = tkin / electron_mass_c2;
69 G4double gam = tau + 1.0;
70 G4double gamma2 = gam * gam;
71 G4double beta2 = 1. - 1. / gamma2;
72 // G4double bg2 = beta2*gamma2;
73
74 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
75 eexc /= electron_mass_c2;
76 G4double eexc2 = eexc * eexc;
77
78 G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin)) / electron_mass_c2;
79 G4double dedx;
80
81 // electron
82 if (isElectron) {
83 dedx = log(2.0 * (tau + 2.0) / eexc2) - 1.0 - beta2 + log((tau - d) * d) + tau / (tau - d)
84 + (0.5 * d * d + (2.0 * tau + 1.) * log(1. - d / tau)) / gamma2;
85
86 // positron
87 }
88 else {
89 G4double d2 = d * d * 0.5;
90 G4double d3 = d2 * d / 1.5;
91 G4double d4 = d3 * d * 3.75;
92 G4double y = 1.0 / (1.0 + gam);
93 dedx =
94 log(2.0 * (tau + 2.0) / eexc2) + log(tau * d)
95 - beta2 * (tau + 2.0 * d - y * (3.0 * d2 + y * (d - d3 + y * (d2 - tau * d3 + d4)))) / tau;
96 }
97
98 // do not apply density correction
99 // G4double cden = material->GetIonisation()->GetCdensity();
100 // G4double mden = material->GetIonisation()->GetMdensity();
101 // G4double aden = material->GetIonisation()->GetAdensity();
102 // G4double x0den = material->GetIonisation()->GetX0density();
103 // G4double x1den = material->GetIonisation()->GetX1density();
104 // G4double x = log(bg2)/twoln10;
105
106 // if (x >= x0den) {
107 // dedx -= twoln10*x - cden;
108 // if (x < x1den) dedx -= aden*pow(x1den-x, mden);
109 // }
110
111 // now you can compute the total ionization loss
112 dedx *= twopi_mc2_rcl2 * electronDensity / beta2;
113 if (dedx < 0.0) dedx = 0.0;
114
115 // lowenergy extrapolation
116
117 if (lowEnergy) {
118 if (kineticEnergy >= lowLimit)
119 dedx *= sqrt(tkin / kineticEnergy);
120 else
121 dedx *= sqrt(tkin * kineticEnergy) / lowLimit;
122 }
123 return dedx;
124 }
125
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127