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 // -*- C++ -*-
 #ifndef HERWIG_MENeutralCurrentDIS_H
 #define HERWIG_MENeutralCurrentDIS_H
 //
 // This is the declaration of the MENeutralCurrentDIS class.
 //
 
 #include "DISBase.h"
 #include "ThePEG/Helicity/Vertex/AbstractFFVVertex.fh"
 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
 #include "ThePEG/Helicity/WaveFunction/SpinorWaveFunction.h"
 #include "ThePEG/Helicity/WaveFunction/SpinorBarWaveFunction.h"
 
 namespace Herwig {
 
 using namespace ThePEG;
 
 /**
  * The MENeutralCurrentDIS class provides the matrix elements for
  * neutral current DIS.
  *
  *  For consistency both the incoming and outgoing quarks are assumed to be massless.
  *
  * @see \ref MENeutralCurrentDISInterfaces "The interfaces"
  * defined for MENeutralCurrentDIS.
  */
 class MENeutralCurrentDIS: public DISBase {
 
 public:
 
   /**
    * The default constructor.
    */
   MENeutralCurrentDIS();
 
   /** @name Virtual functions required by the MEBase class. */
   //@{
   /**
    * Return the order in \f$\alpha_S\f$ in which this matrix
    * element is given.
    */
   virtual unsigned int orderInAlphaS() const;
 
   /**
    * Return the order in \f$\alpha_{EW}\f$ in which this matrix
    * element is given.
    */
   virtual unsigned int orderInAlphaEW() const;
 
   /**
    * The matrix element for the kinematical configuration
    * previously provided by the last call to setKinematics(), suitably
    * scaled by sHat() to give a dimension-less number.
    * @return the matrix element scaled with sHat() to give a
    * dimensionless number.
    */
   virtual double me2() const;
 
   /**
    * Add all possible diagrams with the add() function.
    */
   virtual void getDiagrams() const;
 
   /**
    * Get diagram selector. With the information previously supplied with the
    * setKinematics method, a derived class may optionally
    * override this method to weight the given diagrams with their
    * (although certainly not physical) relative probabilities.
    * @param dv the diagrams to be weighted.
    * @return a Selector relating the given diagrams to their weights.
    */
   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
 
   /**
    * Return a Selector with possible colour geometries for the selected
    * diagram weighted by their relative probabilities.
    * @param diag the diagram chosen.
    * @return the possible colour geometries weighted by their
    * relative probabilities.
    */
   virtual Selector<const ColourLines *>
   colourGeometries(tcDiagPtr diag) const;
 
   /**
    *  Construct the vertex of spin correlations.
    */
   virtual void constructVertex(tSubProPtr);
   //@}
 
 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:
 
   /**
    * Matrix element for \f$\ell q\to \gamma/Z \to \ell q\f$.
    * @param f1 Fermion on lepton line
    * @param a1 Anti-fermion on lepton line
    * @param f2 Fermion on quark line
    * @param a2 Anti-fermion on quark line
    * @param lorder The order of particles on the lepton line
    * @param qorder The order of particles on the quark line
    * @param me  Whether or not to calculate the matrix element for spin correlations
    */
   double helicityME(vector<SpinorWaveFunction>    & f1 ,
             vector<SpinorWaveFunction>    & f2,
             vector<SpinorBarWaveFunction> & a1 ,
             vector<SpinorBarWaveFunction> & a2,
             bool lorder, bool qorder,
             bool me) const;
 
 
   /**
    *  Option for treatment of \f$\gamma/Z\f$ terms
    */
   inline unsigned int gammaZOption() const {return _gammaZ;}
 
   /**
    *  Calculate the coefficient A for the correlations in the hard
    *  radiation
    */
   virtual double A(tcPDPtr lin, tcPDPtr lout, tcPDPtr qin, tcPDPtr qout,
            Energy2 scale) const;
 
 protected:
 
   /** @name Standard Interfaced functions. */
   //@{
   /**
    * Initialize this object after the setup phase before saving an
    * EventGenerator to disk.
    * @throws InitException if object could not be initialized properly.
    */
   virtual void doinit();
   //@}
 
 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);}
   //@}
 
 private:
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   MENeutralCurrentDIS & operator=(const MENeutralCurrentDIS &) = delete;
 
 private:
 
   /**
    *  Pointer to the vertices for the helicity calculations
    */
   //@{
   /**
    *  Pointer to the Z vertex
    */
   AbstractFFVVertexPtr _theFFZVertex;
 
   /**
    *  Pointer to the photon vertex
    */
   AbstractFFVVertexPtr _theFFPVertex;
   //@}
 
   /**
    *  Pointers to the intermediate resonances
    */
   //@{
   /**
    *  Pointer to the Z ParticleData object
    */
   tcPDPtr _z0;
 
   /**
    *  Pointer to the photon ParticleData object
    */
   tcPDPtr _gamma;
   //@}
 
   /**
    *  Switches to control the particles in the hard process
    */
   //@{
   /**
    *  Minimumflavour of the incoming quarks
    */
   int _minflavour;
 
   /**
    *  Maximum flavour of the incoming quarks
    */
   int _maxflavour;
 
   /**
    *  Whether to include both \f$Z^0\f$ and \f$\gamma\f$ or only one
    */
   unsigned int _gammaZ;
   //@}
 
   /**
    * Matrix element for spin correlations
    */
   ProductionMatrixElement _me;
 
   /**
    *  Electroweak parameters
    */
   //@{
   /**
    *  \f$\sin\theta_W\f$
    */
   double _sinW;
 
   /**
    *  \f$\cos\theta_W\f$
    */
   double _cosW;
 
   /**
    *  The square of the Z mass
    */
   Energy2 _mz2;
   //@}
 
 };
 
 }
 
 #endif /* HERWIG_MENeutralCurrentDIS_H */

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