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//
// ------------------------------------------------------------
//      GEANT 4 class header file
//
//      History:
//               30 July 2007 P.Gumplinger
//               Samples Radiative Pion Decay
//               Reference: 
//                    TRIUMF/PIENU Technote: 
//                    "Inclusion of pi->enug in the Monte Carlo" 
//                    by M. Blecher
//
// ------------------------------------------------------------
//
//
//
//

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#ifndef G4PionRadiativeDecayChannel_h
#define G4PionRadiativeDecayChannel_h 1

#include "globals.hh"
#include "Randomize.hh"
#include "G4ThreeVector.hh"
#include "G4VDecayChannel.hh"

class G4PionRadiativeDecayChannel : public G4VDecayChannel
{
  // Class Decription
  // This class describes radiative pion decay kinemtics, but
  // gives incorrect energy spectrum for neutrino

  public:  // With Description

    //Constructors 
    G4PionRadiativeDecayChannel(const G4String& theParentName,
                                G4double        theBR);
    //  Destructor
    virtual ~G4PionRadiativeDecayChannel();

  protected:
    // Copy constructor and assignment operator
    G4PionRadiativeDecayChannel(const G4PionRadiativeDecayChannel &);
    G4PionRadiativeDecayChannel & operator=(const G4PionRadiativeDecayChannel &);

  protected:
      G4PionRadiativeDecayChannel();

  public:  // With Description

    virtual G4DecayProducts *DecayIt(G4double);

  private:

    G4double beta;

    G4double cib;
    G4double csdp;
    G4double csdm;
    G4double cif;
    G4double cig;

    G4double xl, yl, xu, yu, d2wmax;

    G4double D2W(const G4double x, const G4double y);

};

inline G4double G4PionRadiativeDecayChannel::D2W(const G4double x, 
                                                 const G4double y)
{
  G4double d2w = cib*(1.-y)*(1.+((1.-x)*(1.-x)))/((x*x)*(x+y-1.)) +
                 csdp*(1.-x)*((x+y-1.)*(x+y-1.)) +
                 csdm*(1.-x)*((1.-y)*(1.-y)) +
                 cif*(x-1.)*(1.-y)/x +
                 cig*(1.-y)*(1.-x+(x*x)/(x+y-1.))/x;
  return d2w;
}

#endif