include/Geant4/G4PolarizedComptonXS.hh

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0025 //
0026 // Geant4 Class file
0027 //
0028 // File name:     G4PolarizedComptonXS
0029 //
0030 // Author:        Andreas Schaelicke
0031 //
0032 // Class Description:
0033 //   determine the  polarization of the final state
0034 //   in a Compton scattering process employing the differential
0035 //   cross section by F.W.Lipps & H.A.Tolhoek
0036 //   ( Physica 20 (1954) 395 )
0037
0038 #ifndef G4PolarizedComptonXS_h
0039 #define G4PolarizedComptonXS_h 1
0040
0041 #include "globals.hh"
0042 #include "G4StokesVector.hh"
0043 #include "G4VPolarizedXS.hh"
0044
0045 class G4PolarizedComptonXS : public G4VPolarizedXS
0046 {
0047  public:
0048   G4PolarizedComptonXS();
0049   ~G4PolarizedComptonXS() override;
0050
0051   // prepares the ingredients for the calculation of a polarization
0052   // dependent differential cross section
0053   // the kinematics is fixed (X - incoming photon energy in units of electron
0054   // mass, eps - outgoing photon energy in unit of incoming photon energy,
0055   // and polarization of the incoming particles fixed (p0, p1)
0056   // a flag specifies the extent to which polarization is taken into account
0057   void Initialize(G4double eps, G4double X, G4double phi,
0058                   const G4StokesVector& p0, const G4StokesVector& p1,
0059                   G4int flag = 0) override;
0060
0061   // returns the differential cross section for a given polarisation state
0062   // of the final state particles to be used in the calculation of the
0063   // polarization transfer the calculation has to be initialised by calling
0064   // Initialize() prior to the first call of this function (see above)
0065   G4double XSection(const G4StokesVector& pol2,
0066                     const G4StokesVector& pol3) override;
0067   // total cross section
0068   G4double TotalXSection(G4double xmin, G4double xmax, G4double y,
0069                          const G4StokesVector& pol0,
0070                          const G4StokesVector& pol1) override;
0071
0072   // return expected mean polarisation
0073   G4StokesVector GetPol2() override;
0074   G4StokesVector GetPol3() override;
0075
0076   G4PolarizedComptonXS& operator=(const G4PolarizedComptonXS& right) = delete;
0077   G4PolarizedComptonXS(const G4PolarizedComptonXS&)                  = delete;
0078
0079  private:
0080   void DefineCoefficients(const G4StokesVector& pol0,
0081                           const G4StokesVector& pol1);
0082
0083   static constexpr G4double re2 =
0084     CLHEP::classic_electr_radius * CLHEP::classic_electr_radius *
0085     (4. * CLHEP::pi / CLHEP::hbarc) * (4. * CLHEP::pi / CLHEP::hbarc);
0086
0087   // these variables store the information necessary to evaluate the
0088   // differential cross section for arbitrary final state
0089   // polarizations (used in XSection):
0090   // - part depending on the polarization of the final photon
0091   G4ThreeVector fPhi2;
0092   // - part depending on the polarization of the final electron
0093   G4ThreeVector fPhi3;
0094   // - polarization independent part
0095   G4double fPhi0;
0096   // - product of polarizations of initial particles
0097   G4double polxx, polyy, polzz, polxz, polzx, polyz, polzy, polxy, polyx;
0098
0099   // G4double diffXSFactor, totalXSFactor;
0100   G4double fPolXS, fUnpXS;
0101 };
0102
0103 #endif