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 // -*- C++ -*-
 //
 // VVTVertex.h is a part of ThePEG - Toolkit for HEP Event Generation
 // Copyright (C) 2003-2019 Peter Richardson, Leif Lonnblad
 //
 // ThePEG is licenced under version 3 of the GPL, see COPYING for details.
 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
 //
 #ifndef ThePEG_VVTVertex_H
 #define ThePEG_VVTVertex_H
 //
 // This is the declaration of the VVTVertex class.
 
 #include "ThePEG/Helicity/Vertex/AbstractVVTVertex.h"
 #include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
 #include "ThePEG/Helicity/WaveFunction/TensorWaveFunction.h"
 #include "VVTVertex.fh"
 
 namespace ThePEG {
 namespace Helicity {
 
 /** \ingroup Helicity
  *
  *  The VVTVertex class is the implementation of the 
  *  vector-vector-tensor vertex. 
  *  It inherits from the AbstractVVTVertex class for the storage of the particles
  *  interacting at the vertex and implements the helicity amplitude calculations.
  *
  *  All implementations of this vertex should inherit from it and implement the
  *  virtual setCoupling member.
  *
  *  The vertex has the form
  *  \f[
  *    \left[m^2_v+k_1\cdot k_2)C_{\mu\nu,\rho\sigma}+D_{\mu\nu,\rho\sigma}\right]
  *    \epsilon_1^\rho\epsilon_2^\sigma \epsilon_3^{\mu\nu}
  *  \f]
  *  where
  * - \f$C_{\mu\nu,\rho\sigma}=g_{\mu\rho}g_{\nu\sigma}+g_{\mu\sigma}g_{\nu\rho}
  *         -g_{\mu\nu}g_{\rho\sigma}\f$
  * - \f$D_{\mu\nu,\rho\sigma}=
  *    g_{\mu\nu}k_{1\sigma}k_{2\rho}-\left[g_{\mu\sigma}k_{1\nu}k_{2\rho}+g_{\mu\rho}k_{1\sigma}k_{2\nu}-g_{\rho\sigma}k_{1\mu}k_{2\nu}+(\mu\leftrightarrow\nu)\right]
  *   \f$
  *
  *  @see AbstractVVTVertex
  */
 class VVTVertex: public AbstractVVTVertex {
   
 public:
 
   /**
    * Standard Init function used to initialize the interfaces.
    */
   static void Init();
   
 public:
 
   /**
    * Members to calculate the helicity amplitude expressions for vertices
    * and off-shell particles.
    */
   //@{
   /**
    * Evalulate the vertex.
    * @param q2 The scale \f$q^2\f$ for the coupling at the vertex.
    * @param vec1  The wavefunction for the first  vector.
    * @param vec2  The wavefunction for the second vector.
    * @param ten3  The wavefunction for the tensor.
    * @param vmass The mass of the vector boson.
    */
   Complex evaluate(Energy2 q2,const VectorWaveFunction & vec1,
            const VectorWaveFunction & vec2,
            const TensorWaveFunction & ten3,
            Energy vmass=-GeV);
 
   /**
    * Evaluate the off-shell tensor coming from the vertex.
    * @param q2 The scale \f$q^2\f$ for the coupling at the vertex.
    * @param iopt Option of the shape of the Breit-Wigner for the off-shell tensor.
    * @param out The ParticleData pointer for the off-shell tensor.
    * @param vec1  The wavefunction for the first  vector.
    * @param vec2  The wavefunction for the second vector.
    * @param vmass The mass of the vector boson.
    * @param mass The mass of the off-shell particle if not taken from the ParticleData
    * object
    * @param width The width of the off-shell particle if not taken from the ParticleData
    * object
    */
   TensorWaveFunction evaluate(Energy2 q2,int iopt, tcPDPtr out,
                   const VectorWaveFunction & vec1,
                   const VectorWaveFunction & vec2,
                   Energy vmass=-GeV,
                   complex<Energy> mass=-GeV, complex<Energy> width=-GeV);
 
   /**
    * Evaluate the off-shell vector coming from the vertex.
    * @param q2 The scale \f$q^2\f$ for the coupling at the vertex.
    * @param iopt Option of the shape of the Breit-Wigner for the off-shell vector.
    * @param out The ParticleData pointer for the off-shell vector.
    * @param vec1  The wavefunction for the first vector.
    * @param ten3  The wavefunction for the tensor.
    * @param mass The mass of the off-shell particle if not taken from the ParticleData
    * object
    * @param width The width of the off-shell particle if not taken from the ParticleData
    * object
    */
   VectorWaveFunction evaluate(Energy2 q2,int iopt, tcPDPtr out,
                   const VectorWaveFunction & vec1,
                   const TensorWaveFunction & ten3,
                   complex<Energy> mass=-GeV, complex<Energy> width=-GeV);
   //@}
 
   /**
    *   Set coupling methods
    */
   //@{
   /**
    * Calculate the couplings for a three point interaction.
    * This method is virtual and must be implemented in 
    * classes inheriting from this.
    * @param q2 The scale \f$q^2\f$ for the coupling at the vertex.
    * @param part1 The ParticleData pointer for the first  particle.
    * @param part2 The ParticleData pointer for the second particle.
    * @param part3 The ParticleData pointer for the third  particle.
    */
   virtual void setCoupling(Energy2 q2,tcPDPtr part1,
                tcPDPtr part2,tcPDPtr part3)=0;
 
   /**
    * Dummy setCouplings for a four point interaction 
    * This method is virtual and must be implemented in 
    * classes inheriting from this.
    */
   virtual void setCoupling(Energy2,tcPDPtr,tcPDPtr,tcPDPtr,tcPDPtr) {
     assert(false);
   }
   
 private:
   
   /**
    * Private and non-existent assignment operator.
    */
   VVTVertex & operator=(const VVTVertex &) = delete;
   
 };
 
 }
 
 }
 #endif /* ThePEG_VVTVertex_H */

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