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// $Id: G4eCoulombScatteringModel.hh,v 1.5 2006/10/19 09:44:27 vnivanch Exp $
// GEANT4 tag $Name: geant4-08-02 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class header file
//
//
// File name:     G4eCoulombScatteringModel
//
// Author:        Vladimir Ivanchenko 
//
// Creation date: 19.02.2006
//
// Modifications:
// 01.08.06 V.Ivanchenko extend upper limit of table to TeV and review the
//          logic of building - only elements from G4ElementTable
// 08.08.06 V.Ivanchenko build internal table in ekin scale, introduce faclim
// 19.08.06 V.Ivanchenko add inline function ScreeningParameter and
//                       make some members protected
//
// Class Description:
//
// Implementation of eCoulombScattering of pointlike charge particle 
// on Atomic Nucleus for interval of scattering anles in Lab system 
// thetaMin - ThetaMax, nucleus recoil is neglected.
//   The model based on analysis of J.M.Fernandez-Varea et al. 
// NIM B73(1993)447 originated from G.Wentzel Z.Phys. 40(1927)590 with 
// screening parameter from H.A.Bethe Phys. Rev. 89 (1953) 1256.
// 

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

#ifndef G4eCoulombScatteringModel_h
#define G4eCoulombScatteringModel_h 1

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

class G4ParticleChangeForGamma;

class G4eCoulombScatteringModel : public G4VEmModel
{

public:

  G4eCoulombScatteringModel(G4double thetaMin = 0.0, G4double thetaMax = pi,
			   G4bool build = true, G4double tlim = TeV*TeV,
			   const G4String& nam = "eCoulombScattering");
 
  virtual ~G4eCoulombScatteringModel();

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

  virtual G4double ComputeCrossSectionPerAtom(
                                const G4ParticleDefinition*,
                                      G4double kinEnergy, 
                                      G4double Z, 
                                      G4double A, 
                                      G4double cut,
                                      G4double emax);

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

protected:

  G4double ScreeningParameter(G4double Z, G4double q2,
			      G4double mom2, G4double invbeta2);

private:

  G4double CalculateCrossSectionPerAtom(const G4ParticleDefinition*, 
					G4double kinEnergy, 
					G4double Z);

  // hide assignment operator
  G4eCoulombScatteringModel & operator=(const G4eCoulombScatteringModel &right);
  G4eCoulombScatteringModel(const  G4eCoulombScatteringModel&);

protected:

  G4ParticleChangeForGamma* fParticleChange;

  G4double                  coeff;
  G4double                  cosThetaMin;
  G4double                  cosThetaMax;
  G4double                  q2Limit;


private:

  G4PhysicsTable*           theCrossSectionTable; 

  G4double                  a0;
  G4double                  lowKEnergy;
  G4double                  highKEnergy;
  G4double                  alpha2;
  G4double                  faclim;

  G4int                     nbins;
  G4int                     nmax;
  G4int                     index[100];

  G4bool                    buildTable;             
  G4bool                    isInitialised;             
};

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

inline G4double G4eCoulombScatteringModel::ComputeCrossSectionPerAtom(
                const G4ParticleDefinition* p,
		G4double kinEnergy,
		G4double Z, G4double,
		G4double, G4double)
{
  G4double x;
  G4bool b;
  if(theCrossSectionTable) {
    x = std::exp((((*theCrossSectionTable)[index[G4int(Z)]]))
      ->GetValue(kinEnergy, b));
  } else x = CalculateCrossSectionPerAtom(p, kinEnergy, Z);

  //  G4cout << "G4eCoulombScatteringModel: e= " << kinEnergy 
  //         << "  cs= " << x << G4endl;
  return x;
}

inline G4double G4eCoulombScatteringModel::ScreeningParameter(
                G4double Z, 
                G4double q2, 
		G4double mom2, 
		G4double invbeta2)
{
  G4double a = invbeta2*Z*Z*q2*alpha2;
  return std::pow(Z,0.6666667)*a0*(1.13 + 3.76*a)/mom2;
}

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

#endif