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//
// GEANT4 Class header file G4ChargeExchangeXS
//
// Author V.Ivanchenko 
//
// Modified: 09.08.2023 Tim Lok Chau, CERN summer student program 
//
 
// This is a class for charge exchange hadronic cross sections:
// pi- + N(Z, A) -> X + N(Z-1, A)
// pi+ + N(Z, A) -> X + N(Z+1, A)
//
// where X = pi0, eta, etaP, omega, f2
// V. Lyubovitsky, NA64 Collaboration (CERN)
//
// K- + N(Z, A) -> Y  + N(Z-1, A)
// K+ + N(Z, A) -> Y  + N(Z+1, A)
// KL + N(Z, A) -> K+ + N(Z-1, A)
// KL + N(Z, A) -> K- + N(Z+1, A)
//
// where Y = KS, KL
// 

#ifndef G4CHARGEEXCHANGEXS_HH
#define G4CHARGEEXCHANGEXS_HH

#include "G4VCrossSectionDataSet.hh"
#include "globals.hh"
#include <vector>

class G4DynamicParticle;
class G4ParticleDefinition;
class G4Isotope;
class G4Element;
class G4Material;
class G4Pow;

class G4ChargeExchangeXS final : public G4VCrossSectionDataSet
{
public: 

  G4ChargeExchangeXS();

  ~G4ChargeExchangeXS() override = default;

  G4bool IsElementApplicable(const G4DynamicParticle*, G4int Z, 
                             const G4Material*) final;

  G4double GetElementCrossSection(const G4DynamicParticle*, G4int Z,
                                  const G4Material*) final;

  void CrossSectionDescription(std::ostream&) const final;

  const G4ParticleDefinition*
  SampleSecondaryType(const G4ParticleDefinition*, const G4Material*,
		      G4int Z, G4int A, G4double etot);

  G4double GetPartialPionXS(G4int idx) const;
  
  void SetEnergyLimit(G4double val) { fEnergyLimit = val; };

  void SetPionCrossSectionFactor(G4double val) { fFactorPi = val; };

  void SetKaonCrossSectionFactor(G4double val) { fFactorK = val; };
  
  G4double GetCrossSectionFactor() const { return fFactor; };
  
  G4bool isPion() const { return findex >= 0; };

  G4double SampleTforPion(const G4double etot,
			  const G4double tmax) const;

  G4ChargeExchangeXS & operator=(const G4ChargeExchangeXS &right) = delete;
  G4ChargeExchangeXS(const G4ChargeExchangeXS&) = delete;
  
private:

  G4double GetCrossSection(const G4ParticleDefinition*, const G4Material*,
			   G4int Z, G4double etot);

  G4double ComputeDeuteronFraction(const G4Material*) const;

  G4Pow* g4calc;
  G4int findex{-1};
  const G4ParticleDefinition* fPionSecPD[5];
  G4double fXSecPion[5] = {0.0, 0.0, 0.0, 0.0, 0.0};
  G4double fEnergyLimit{0.0};
  G4double fFactorPi{1.0};
  G4double fFactorK{1.0};
  G4double fFactor{1.0};
  G4double fMassPi;
};

#endif