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25 //
26 // Author: Alexei Sytov
27 // Co-author: Gianfranco Paterno (testing)
28 // Using the key points of G4BaierKatkov and developments of V.V. Tikhomirov,
29 // partially described in L. Bandiera et al. Eur. Phys. J. C 82, 699 (2022)
30
31 #ifndef G4CoherentPairProduction_h
32 #define G4CoherentPairProduction_h 1
33
34 #include "G4VDiscreteProcess.hh"
35
36 #include <vector>
37 #include <CLHEP/Units/SystemOfUnits.h>
38 #include <CLHEP/Units/PhysicalConstants.h>
39 #include <CLHEP/Vector/TwoVector.h>
40
41 #include "G4ChannelingFastSimCrystalData.hh"
42 #include "G4LogicalVolume.hh"
43 #include "G4ParticleTable.hh"
44
45 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
46
47 class G4CoherentPairProduction : public G4VDiscreteProcess
48 {
49 public:
50 G4CoherentPairProduction(const G4String& processName = "cpp",
51 G4ProcessType aType = fElectromagnetic);
52
53 ~G4CoherentPairProduction() = default;
54
55 G4VParticleChange* PostStepDoIt(const G4Track&, const G4Step&) override;
56
57 G4bool IsApplicable(const G4ParticleDefinition& aPD) override
58 {
59 return(aPD.GetParticleName() == "gamma");
60 }
61
62 // print documentation in html format
63 void ProcessDescription(std::ostream&) const override;
64
65 ///special functions
66 void Input(const G4Material* crystal,
67 const G4String &lattice)
68 {Input(crystal,lattice,"");}
69
70 void Input(const G4Material* crystal,
71 const G4String &lattice,
72 const G4String &filePath);
73
74 // an option to use crystal data already created outside this class
75 void Input(const G4ChannelingFastSimCrystalData* crystalData);
76
77 ///activate incoherent scattering
78 ///(standard gamma conversion should be switched off in physics list)
79 void ActivateIncoherentScattering(){fIncoherentScattering = true;}
80
81 G4ChannelingFastSimCrystalData* GetCrystalData() {return fCrystalData;}
82
83 ///get cuts
84 // minimal energy for non-zero cross section
85 G4double ModelMinPrimaryEnergy() { return fLowEnergyLimit;}
86 G4double GetHighAngleLimit() {return fHighAngleLimit;}
87 G4double GetPPKineticEnergyCut() {return fPPKineticEnergyCut;}
88
89 /// get the number of pairs in sampling of Baier-Katkov Integral
90 /// (MC integration by e+- energy and angles <=> e+- momentum)
91 G4int GetSamplingPairsNumber(){return fNMCPairs;}
92
93 /// get the number of particle angles 1/gamma in pair production
94 /// defining the width of the angular distribution of pair sampling
95 /// in the Baier-Katkov Integral
96 G4double GetChargeParticleAngleFactor(){return fChargeParticleAngleFactor;}
97
98 /// get number of trajectory steps of a single particle (e- or e+)
99 G4double GetNTrajectorySteps(){return fNTrajectorySteps;}
100
101 /// get effective radiation length
102 /// (due to coherent process of pair production)
103 /// simulated for the current photon
104 G4double GetEffectiveLrad(){return fEffectiveLrad;}
105
106 ///get the name of G4Region in which the model is applicable
107 G4String GetG4RegionName() {return fG4RegionName;}
108
109 ///set cuts
110 void SetLowEnergyLimit(G4double energy){fLowEnergyLimit=energy;}
111 void SetHighAngleLimit(G4double angle) {fHighAngleLimit=angle;}
112 void SetPPKineticEnergyCut(G4double kineticEnergyCut) {fPPKineticEnergyCut=kineticEnergyCut;}
113
114 /// set the number of pairs in sampling of Baier-Katkov Integral
115 /// (MC integration by e+- energy and angles <=> e+- momentum)
116 void SetSamplingPairsNumber(G4int nPairs){fNMCPairs = nPairs;}
117
118 /// set the number of particle angles 1/gamma in pair production
119 /// defining the width of the angular distribution of pair sampling
120 /// in the Baier-Katkov Integral
121 void SetChargeParticleAngleFactor(G4double chargeParticleAngleFactor)
122 {fChargeParticleAngleFactor = chargeParticleAngleFactor;}
123
124 /// set number of trajectory steps of a single particle (e- or e+)
125 void SetNTrajectorySteps(G4int nTrajectorySteps)
126 {fNTrajectorySteps = nTrajectorySteps;}
127
128 ///set the name of G4Region in which the model is applicable
129 void SetG4RegionName(const G4String& nameG4Region){fG4RegionName=nameG4Region;}
130
131 G4double GetMeanFreePath(const G4Track& aTrack,
132 G4double,
133 G4ForceCondition* condition) override;
134
135 private:
136
137 G4int FindVectorIndex(std::vector<G4double> &myvector, G4double value);
138
139 G4ChannelingFastSimCrystalData* fCrystalData{nullptr};
140
141 //collection of etotal
142 std::vector <CLHEP::Hep2Vector> fullVectorEtotal;
143
144 //collection of x
145 std::vector <CLHEP::Hep2Vector> fullVectorX;
146
147 //collection of y
148 std::vector <CLHEP::Hep2Vector> fullVectorY;
149
150 //collection of tx
151 std::vector <CLHEP::Hep2Vector> fullVectorTX;
152
153 //collection of tx
154 std::vector <CLHEP::Hep2Vector> fullVectorTY;
155
156 //the vector of the discrete CDF of the production of sampling e+e- pairs
157 //(in reality per distance along the photon direction)
158 std::vector <G4double> fPairProductionCDFdz;
159
160 G4double fLowEnergyLimit = 1*CLHEP::GeV;
161 G4double fHighAngleLimit = 50*CLHEP::mrad;
162
163 ///minimal kinetic energy of a charged particle produced
164 G4double fPPKineticEnergyCut = 1*CLHEP::MeV;
165
166 ///Monte Carlo statistics of e+- pair sampling in Baier-Katkov for 1 photon
167 G4int fNMCPairs = 150;
168
169 G4double fChargeParticleAngleFactor = 4; // number of particle angles 1/gamma:
170 // more fChargeParticleAngleFactor => higher paramParticleAngle
171
172 ///number of trajectory steps of a single particle (e- or e+)
173 G4int fNTrajectorySteps=250;
174
175 ///effective radiation length (due to coherent process of pair production)
176 G4double fEffectiveLrad = 0.;
177
178 ///the name of G4Region in which the model is applicable
179 G4String fG4RegionName = "Crystal";
180
181 ///charged particle mass
182 const G4double fMass = CLHEP::electron_mass_c2;
183
184 ///flag of simulation of incoherent scattering
185 G4bool fIncoherentScattering = false;
186
187 };
188
189 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
190
191 #endif
192
193