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 // -*- C++ -*-
 //
 // KPiCurrent.h is a part of Herwig - A multi-purpose Monte Carlo event generator
 // Copyright (C) 2002-2019 The Herwig Collaboration
 //
 // Herwig is licenced under version 3 of the GPL, see COPYING for details.
 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
 //
 #ifndef HERWIG_KPiCurrent_H
 #define HERWIG_KPiCurrent_H
 //
 // This is the declaration of the KPiCurrent class.
 //
 
 #include "WeakCurrent.h"
 #include "Herwig/Utilities/Kinematics.h"
 
 namespace Herwig {
 
 using namespace ThePEG;
 
 /**
  * Here is the documentation of the KPiCurrent class.
  *
  * @see \ref KPiCurrentInterfaces "The interfaces"
  * defined for KPiCurrent.
  */
 class KPiCurrent: public WeakCurrent {
 
 public:
 
   /**
    * The default constructor.
    */
   KPiCurrent();
 
 
   /** @name Methods for the construction of the phase space integrator. */
   //@{
   /**
    * Complete the construction of the decay mode for integration.classes inheriting
    * from this one.
    * This method is purely virtual and must be implemented in the classes inheriting
    * from WeakCurrent.
    * @param icharge   The total charge of the outgoing particles in the current.
    * @param resonance If specified only include terms with this particle
    * @param flavour Information on the required flavours of the quarks
    * @param imode     The mode in the current being asked for.
    * @param mode      The phase space mode for the integration
    * @param iloc      The location of the of the first particle from the current in
    *                  the list of outgoing particles.
    * @param ires      The location of the first intermediate for the current.
    * @param phase     The prototype phase space channel for the integration.
    * @param upp       The maximum possible mass the particles in the current are
    *                  allowed to have.
    * @return Whether the current was sucessfully constructed.
    */
   virtual bool createMode(int icharge, tcPDPtr resonance,
               FlavourInfo flavour,
               unsigned int imode,PhaseSpaceModePtr mode,
               unsigned int iloc,int ires,
               PhaseSpaceChannel phase, Energy upp );
 
   /**
    * The particles produced by the current. This just returns the two pseudoscalar
    * mesons and the photon.
    * @param icharge The total charge of the particles in the current.
    * @param imode The mode for which the particles are being requested
    * @param iq The PDG code for the quark
    * @param ia The PDG code for the antiquark
    * @return The external particles for the current.
    */
   virtual tPDVector particles(int icharge, unsigned int imode, int iq, int ia);
   //@}
 
 
   /**
    * Hadronic current. This method is purely virtual and must be implemented in
    * all classes inheriting from this one.
    * @param resonance If specified only include terms with this particle
    * @param flavour Information on the required flavours of the quarks
    * @param imode The mode
    * @param ichan The phase-space channel the current is needed for.
    * @param scale The invariant mass of the particles in the current.
    * @param outgoing The particles produced in the decay
    * @param momenta  The momenta of the particles produced in the decay
    * @param meopt Option for the calculation of the matrix element
    * @return The current. 
    */
   virtual vector<LorentzPolarizationVectorE> 
   current(tcPDPtr resonance,
       FlavourInfo flavour,
       const int imode, const int ichan,Energy & scale,
       const tPDVector & outgoing,
       const vector<Lorentz5Momentum> & momenta,
       DecayIntegrator::MEOption meopt) const;
 
   /**
    * Accept the decay. Checks the particles are the allowed mode.
    * @param id The id's of the particles in the current.
    * @return Can this current have the external particles specified.
    */
   virtual bool accept(vector<int> id);
 
   /**
    * Return the decay mode number for a given set of particles in the current. 
    * @param id The id's of the particles in the current.
    * @return The number of the mode
    */
   virtual unsigned int decayMode(vector<int> id);
 
   /**
    * Output the setup information for the particle database
    * @param os The stream to output the information to
    * @param header Whether or not to output the information for MySQL
    * @param create Whether or not to add a statement creating the object
    */
   virtual void dataBaseOutput(ofstream & os,bool header,bool create) const;
 
 public:
 
   /** @name Functions used by the persistent I/O system. */
   //@{
   /**
    * Function used to write out object persistently.
    * @param os the persistent output stream written to.
    */
   void persistentOutput(PersistentOStream & os) const;
 
   /**
    * Function used to read in object persistently.
    * @param is the persistent input stream read from.
    * @param version the version number of the object when written.
    */
   void persistentInput(PersistentIStream & is, int version);
   //@}
 
   /**
    * The standard Init function used to initialize the interfaces.
    * Called exactly once for each class by the class description system
    * before the main function starts or
    * when this class is dynamically loaded.
    */
   static void Init();
 
 protected:
 
   /**
    * Breit-Wigner distributions
    */
   //@{
   /**
    * s-wave Breit-Wigner for the scalar resonances
    * @param q2 The scale
    * @param ires The resonances
    */
   Complex sWaveBreitWigner(Energy2 q2,unsigned int ires) const {
     Energy q=sqrt(q2),gam(ZERO);
     Energy2 m2=sqr(_scamass[ires]);
     if(q>_mK+_mpi) {
       Energy pX=Kinematics::pstarTwoBodyDecay(_scamass[ires],_mK,_mpi);
       Energy p =Kinematics::pstarTwoBodyDecay( q            ,_mK,_mpi);
       gam = _scawidth[ires]*m2/q2*p/pX;
     }
     return m2/(m2-q2-Complex(0.,1.)*q*gam);
   }
   
   /**
    *  p-wave Breit-Wigner for the vector resonances
    * @param q2 The scale
    * @param ires The resonances
    */
   Complex pWaveBreitWigner(Energy2 q2,unsigned int ires) const {
     Energy q=sqrt(q2),gam(ZERO);
     Energy2 m2=sqr(_vecmass[ires]);
     if(q>_mK+_mpi) {
       Energy pX=Kinematics::pstarTwoBodyDecay(_vecmass[ires],_mK,_mpi);
       Energy p =Kinematics::pstarTwoBodyDecay( q            ,_mK,_mpi);
       double ratio=p/pX;
       gam = _vecwidth[ires]*m2/q2*ratio*sqr(ratio);
     }
     return m2/(m2-q2-Complex(0.,1.)*q*gam);
   }
   //@}
 
 protected:
 
   /** @name Clone Methods. */
   //@{
   /**
    * Make a simple clone of this object.
    * @return a pointer to the new object.
    */
   virtual IBPtr clone() const {return new_ptr(*this);}
   
   /** Make a clone of this object, possibly modifying the cloned object
    * to make it sane.
    * @return a pointer to the new object.
    */
   virtual IBPtr fullclone() const {return new_ptr(*this);}
   //@}
 
 protected:
 
   /** @name Standard Interfaced functions. */
   //@{
 
   /**
    * Initialize this object after the setup phase before saving and
    * EventGenerator to disk.
    * @throws InitException if object could not be initialized properly.
    */
   virtual void doinit();
   //@}
 
 private:
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   KPiCurrent & operator=(const KPiCurrent &) = delete;
 
 private:
 
   /**
    *  Use local value of the parameters not those from the ParticleData objects
    */
   bool _localparameters;
 
   /**
    *  Whether to use \f$m^2\f$ or \f$Q^2\f$ in the projection operator.
    */
   bool _transverse;
 
   /**
    *  Normalizations of the vector and scalar pieces
    */
   //@{
   /**
    * \f$c_V\f$, normalization of the vector piece.
    */
   double _cV;
 
   /**
    * \f$c_S\f$, normalization of the scalar piece
    */
   double _cS;
   //@}
 
   /**
    * Parameters for the vector resonances
    */
   //@{
   /**
    *  Magnitude of the vector weights
    */
   vector<double> _vecmag;
 
   /**
    *  Phase of the vector weights
    */
   vector<double> _vecphase;
 
   /**
    *  Weights for the vector resonaces
    */
   vector<Complex> _vecwgt;
 
   /**
    *  Masses of the vector resonances
    */
   vector<Energy> _vecmass;
 
   /**
    *  Widths of the vector resonances
    */
   vector<Energy> _vecwidth;
   //@}
 
   /**
    * Parameters for the scalar resonances
    */
   //@{
   /**
    *  Magnitude of the scalar weights
    */
   vector<double> _scamag;
 
   /**
    *  Phase of the scalar weights
    */
   vector<double> _scaphase;
 
   /**
    *  Weights for the scalar resonances
    */
   vector<Complex> _scawgt;
 
   /**
    *  Masses of the scalar resonances
    */
   vector<Energy> _scamass;
 
   /**
    *  Widths of the scalar resonances
    */
   vector<Energy> _scawidth;
   //@}
 
   /**
    *  Masses for calculating the running widths
    */
   //@{
   /**
    * The pion mass
    */
   Energy _mpi;
 
   /**
    * The kaon mass
    */
   Energy _mK;
   //@}
 
   /**
    *  Map for the resonances
    */
   vector<int> _resmap;
 };
 
 }
 
 #endif /* HERWIG_KPiCurrent_H */

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