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25 //
26 // Geant4 Class file
27 //
28 // File name: G4PolarizedComptonXS
29 //
30 // Author: Andreas Schaelicke
31 //
32 // Class Description:
33 // determine the polarization of the final state
34 // in a Compton scattering process employing the differential
35 // cross section by F.W.Lipps & H.A.Tolhoek
36 // ( Physica 20 (1954) 395 )
37
38 #ifndef G4PolarizedComptonXS_h
39 #define G4PolarizedComptonXS_h 1
40
41 #include "globals.hh"
42 #include "G4StokesVector.hh"
43 #include "G4VPolarizedXS.hh"
44
45 class G4PolarizedComptonXS : public G4VPolarizedXS
46 {
47 public:
48 G4PolarizedComptonXS();
49 ~G4PolarizedComptonXS() override;
50
51 // prepares the ingredients for the calculation of a polarization
52 // dependent differential cross section
53 // the kinematics is fixed (X - incoming photon energy in units of electron
54 // mass, eps - outgoing photon energy in unit of incoming photon energy,
55 // and polarization of the incoming particles fixed (p0, p1)
56 // a flag specifies the extent to which polarization is taken into account
57 void Initialize(G4double eps, G4double X, G4double phi,
58 const G4StokesVector& p0, const G4StokesVector& p1,
59 G4int flag = 0) override;
60
61 // returns the differential cross section for a given polarisation state
62 // of the final state particles to be used in the calculation of the
63 // polarization transfer the calculation has to be initialised by calling
64 // Initialize() prior to the first call of this function (see above)
65 G4double XSection(const G4StokesVector& pol2,
66 const G4StokesVector& pol3) override;
67 // total cross section
68 G4double TotalXSection(G4double xmin, G4double xmax, G4double y,
69 const G4StokesVector& pol0,
70 const G4StokesVector& pol1) override;
71
72 // return expected mean polarisation
73 G4StokesVector GetPol2() override;
74 G4StokesVector GetPol3() override;
75
76 G4PolarizedComptonXS& operator=(const G4PolarizedComptonXS& right) = delete;
77 G4PolarizedComptonXS(const G4PolarizedComptonXS&) = delete;
78
79 private:
80 void DefineCoefficients(const G4StokesVector& pol0,
81 const G4StokesVector& pol1);
82
83 static constexpr G4double re2 =
84 CLHEP::classic_electr_radius * CLHEP::classic_electr_radius *
85 (4. * CLHEP::pi / CLHEP::hbarc) * (4. * CLHEP::pi / CLHEP::hbarc);
86
87 // these variables store the information necessary to evaluate the
88 // differential cross section for arbitrary final state
89 // polarizations (used in XSection):
90 // - part depending on the polarization of the final photon
91 G4ThreeVector fPhi2;
92 // - part depending on the polarization of the final electron
93 G4ThreeVector fPhi3;
94 // - polarization independent part
95 G4double fPhi0;
96 // - product of polarizations of initial particles
97 G4double polxx, polyy, polzz, polxz, polzx, polyz, polzy, polxy, polyx;
98
99 // G4double diffXSFactor, totalXSFactor;
100 G4double fPolXS, fUnpXS;
101 };
102
103 #endif
104