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src/MyMollerBhabhaModel.cc
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29 // $Id: MyMollerBhabhaModel.cc 86064 2014-11-07 08:49:32Z gcosmo $
30 //
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33 
34 #include "MyMollerBhabhaModel.hh"
35 
36 #include "G4PhysicalConstants.hh"
37 #include "G4SystemOfUnits.hh"
38 
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40 
41 using namespace std;
42 
44  const G4String& nam)
45  : G4MollerBhabhaModel(p,nam)
46 {}
47 
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49 
51 {}
52 
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54 
56  const G4Material* material,
57  const G4ParticleDefinition* p,
59  G4double cutEnergy)
60 {
61  if(!particle) SetParticle(p);
62  // calculate the dE/dx due to the ionization by Seltzer-Berger formula
63 
64  G4double electronDensity = material->GetElectronDensity();
65  G4double Zeff = electronDensity/material->GetTotNbOfAtomsPerVolume();
66  G4double th = 0.25*sqrt(Zeff)*keV;
67  G4double tkin = kineticEnergy;
68  G4bool lowEnergy = false;
69  if (kineticEnergy < th) {
70  tkin = th;
71  lowEnergy = true;
72  }
73  G4double tau = tkin/electron_mass_c2;
74  G4double gam = tau + 1.0;
75  G4double gamma2= gam*gam;
76  G4double beta2 = 1. - 1./gamma2;
77  //G4double bg2 = beta2*gamma2;
78 
79  G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
80  eexc /= electron_mass_c2;
81  G4double eexc2 = eexc*eexc;
82 
83  G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2;
84  G4double dedx;
85 
86  // electron
87  if (isElectron) {
88 
89  dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2
90  + log((tau-d)*d) + tau/(tau-d)
91  + (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2;
92 
93  //positron
94  } else {
95 
96  G4double d2 = d*d*0.5;
97  G4double d3 = d2*d/1.5;
98  G4double d4 = d3*d*3.75;
99  G4double y = 1.0/(1.0 + gam);
100  dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d)
101  - beta2*(tau + 2.0*d - y*(3.0*d2
102  + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau;
103  }
104 
105  //do not apply density correction
106  //G4double cden = material->GetIonisation()->GetCdensity();
107  //G4double mden = material->GetIonisation()->GetMdensity();
108  //G4double aden = material->GetIonisation()->GetAdensity();
109  //G4double x0den = material->GetIonisation()->GetX0density();
110  //G4double x1den = material->GetIonisation()->GetX1density();
111  //G4double x = log(bg2)/twoln10;
112 
113  //if (x >= x0den) {
114  // dedx -= twoln10*x - cden;
115  // if (x < x1den) dedx -= aden*pow(x1den-x, mden);
116  //}
117 
118  // now you can compute the total ionization loss
119  dedx *= twopi_mc2_rcl2*electronDensity/beta2;
120  if (dedx < 0.0) dedx = 0.0;
121 
122  // lowenergy extrapolation
123 
124  if (lowEnergy) {
125 
126  if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy);
127  else dedx *= sqrt(tkin*kineticEnergy)/lowLimit;
128 
129  }
130  return dedx;
131 }
132 
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static constexpr double keV
Definition: G4SIunits.hh:216
static constexpr double twopi_mc2_rcl2
Float_t y
Definition: compare.C:6
void SetParticle(const G4ParticleDefinition *p)
const char * p
Definition: xmltok.h:285
virtual G4double ComputeDEDXPerVolume(const G4Material *, const G4ParticleDefinition *, G4double kineticEnergy, G4double cutEnergy)
double G4double
Definition: G4Types.hh:76
bool G4bool
Definition: G4Types.hh:79
static const G4double d2
static constexpr double electron_mass_c2
Float_t d
G4double GetMeanExcitationEnergy() const
virtual G4double MaxSecondaryEnergy(const G4ParticleDefinition *, G4double kinEnergy) final
G4IonisParamMat * GetIonisation() const
Definition: G4Material.hh:227
const G4ParticleDefinition * particle
G4double GetTotNbOfAtomsPerVolume() const
Definition: G4Material.hh:210
G4double GetElectronDensity() const
Definition: G4Material.hh:218
MyMollerBhabhaModel(const G4ParticleDefinition *p=0, const G4String &nam="myMollerBhabha")
T min(const T t1, const T t2)
brief Return the smallest of the two arguments