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// $Id: G4BetheHeitlerModel.hh,v 1.6 2007/05/22 17:34:36 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-02 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class header file
//
//
// File name:     G4BetheHeitlerModel
//
// Author:        Vladimir Ivanchenko on base of Michel Maire code
//
// Creation date: 19.04.2005
//
// Modifications:
// 02-02-06 Remove InitialiseCrossSectionPerAtom();
//
// Class Description:
//
// Implementation of gamma convertion to e+e- in the field of a nucleus 
// 

// -------------------------------------------------------------------
//

#ifndef G4BetheHeitlerModel_h
#define G4BetheHeitlerModel_h 1

#include "G4VEmModel.hh"
#include "G4PhysicsTable.hh"

class G4ParticleChangeForGamma;

class G4BetheHeitlerModel : public G4VEmModel
{

public:

  G4BetheHeitlerModel(const G4ParticleDefinition* p = 0, 
		      const G4String& nam = "Bethe-Heitler");
 
  virtual ~G4BetheHeitlerModel();

  virtual void Initialise(const G4ParticleDefinition*, const G4DataVector&);

  virtual G4double ComputeCrossSectionPerAtom(
                                const G4ParticleDefinition*,
                                      G4double kinEnergy, 
                                      G4double Z, 
                                      G4double A=0., 
                                      G4double cut=0.,
                                      G4double emax=DBL_MAX);

  virtual void SampleSecondaries(std::vector<G4DynamicParticle*>*,
				 const G4MaterialCutsCouple*,
				 const G4DynamicParticle*,
				 G4double tmin,
				 G4double maxEnergy);

private:

  G4double ScreenFunction1(G4double ScreenVariable);

  G4double ScreenFunction2(G4double ScreenVariable);

  // hide assignment operator
  G4BetheHeitlerModel & operator=(const G4BetheHeitlerModel &right);
  G4BetheHeitlerModel(const  G4BetheHeitlerModel&);

  G4ParticleDefinition*     theGamma;
  G4ParticleDefinition*     theElectron;
  G4ParticleDefinition*     thePositron;
  G4ParticleChangeForGamma* fParticleChange;
  G4PhysicsTable*           theCrossSectionTable; 

  G4double                  lowGammaEnergy;
  G4double                  highGammaEnergy;

  G4int                     nbins;
  size_t                    indexZ[120];
  
};

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

inline G4double G4BetheHeitlerModel::ScreenFunction1(G4double ScreenVariable)

// compute the value of the screening function 3*PHI1 - PHI2

{
   G4double screenVal;

   if (ScreenVariable > 1.)
     screenVal = 42.24 - 8.368*std::log(ScreenVariable+0.952);
   else
     screenVal = 42.392 - ScreenVariable*(7.796 - 1.961*ScreenVariable);

   return screenVal;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

inline G4double G4BetheHeitlerModel::ScreenFunction2(G4double ScreenVariable)

// compute the value of the screening function 1.5*PHI1 - 0.5*PHI2

{
   G4double screenVal;

   if (ScreenVariable > 1.)
     screenVal = 42.24 - 8.368*std::log(ScreenVariable+0.952);
   else
     screenVal = 41.405 - ScreenVariable*(5.828 - 0.8945*ScreenVariable);

   return screenVal;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

#endif
