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//
//
//         ------------ G4AnnihiToMuPair physics process ------
//         by H.Burkhardt, S. Kelner and R. Kokoulin, November 2002
// -----------------------------------------------------------------------------

// class description
//
// (high energy) e+ (atomic) e- ---> mu+ mu-
// inherit from G4VDiscreteProcess
//
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......//
//
// 04.02.03 : cosmetic simplifications (mma)
// 27.01.03 : first implementation (hbu)
//
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

#ifndef G4AnnihiToMuPair_h
#define G4AnnihiToMuPair_h 1

#include "G4VDiscreteProcess.hh"
#include "globals.hh"

class G4LossTableManager;
class G4ParticleDefinition;
class G4Track;
class G4Step;

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

class G4AnnihiToMuPair : public G4VDiscreteProcess
{
public:  // with description

  explicit G4AnnihiToMuPair(const G4String& processName ="AnnihiToMuPair",
			    G4ProcessType type = fElectromagnetic);

  ~G4AnnihiToMuPair() override;

  G4bool IsApplicable(const G4ParticleDefinition&) override;
  // true for positron only.

  void BuildPhysicsTable(const G4ParticleDefinition&) override;
  // here dummy, just calling PrintInfoDefinition
  // the total cross section is calculated analytically

  void PrintInfoDefinition();
  // Print few lines of informations about the process: validity range,
  // origine ..etc..
  // Invoked by BuildPhysicsTable().

  void SetCrossSecFactor(G4double fac);
  // Set the factor to artificially increase the crossSection (default 1)

  G4double GetCrossSecFactor() {return fCrossSecFactor;};
  // Get the factor to artificially increase the cross section

  G4double CrossSectionPerVolume(G4double positronEnergy, const G4Material*);

  G4double ComputeCrossSectionPerElectron(const G4double energy);

  G4double ComputeCrossSectionPerAtom(const G4double energy, const G4double Z);

  G4double GetMeanFreePath(const G4Track& aTrack,
			   G4double previousStepSize,
			   G4ForceCondition* ) override;
  // It returns the MeanFreePath of the process for the current track :
  // (energy, material)
  // The previousStepSize and G4ForceCondition* are not used.
  // This function overloads a virtual function of the base class.
  // It is invoked by the ProcessManager of the Particle.

  G4VParticleChange* PostStepDoIt(const G4Track& aTrack,
				  const G4Step& aStep) override;
  // It computes the final state of the process (at end of step),
  // returned as a ParticleChange object.
  // This function overloads a virtual function of the base class.
  // It is invoked by the ProcessManager of the Particle.

  // hide assignment operator as private
  G4AnnihiToMuPair& operator=(const G4AnnihiToMuPair &right) = delete;
  G4AnnihiToMuPair(const G4AnnihiToMuPair& ) = delete;

private:

  G4LossTableManager* fManager;
  const G4ParticleDefinition* part1;
  const G4ParticleDefinition* part2;
  G4double fMass;

  G4double fLowEnergyLimit;  // Energy threshold of e+
  G4double fHighEnergyLimit; // Limit of validity of the model
  G4double fCurrentSigma;    // the last value of cross section per volume 
  G4double fCrossSecFactor;  // factor to increase the cross section
  G4String fInfo = "e+e->mu+mu-";
};

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

#endif