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 // -*- C++ -*-
 #ifndef HERWIG_MEfftoffH_H
 #define HERWIG_MEfftoffH_H
 //
 // This is the declaration of the MEfftoffH class.
 //
 
 #include "HwMEBase.h"
 #include "ThePEG/Helicity/Vertex/AbstractFFVVertex.h"
 #include "ThePEG/Helicity/Vertex/AbstractVVSVertex.h"
 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
 #include "Herwig/PDT/GenericMassGenerator.h"
 
 namespace Herwig {
 
 using namespace ThePEG;
 
 /**
  * The MEfftoffH class is the base class for vector boson fusion type
  * processes in Herwig.
  *
  * @see \ref MEfftoffHInterfaces "The interfaces"
  * defined for MEfftoffH.
  */
 class MEfftoffH: public HwMEBase {
 
 public:
 
   /**
    * The default constructor.
    */
   MEfftoffH() : _shapeopt(2), _maxflavour(5), _minflavour(1), _process(0), 
         _mh(), _wh(), _swap(false) {}
   
   /** @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;
 
   /**
    * Return the scale associated with the last set phase space point.
    */
   virtual Energy2 scale() const;
 
   /**
    * Set the typed and momenta of the incoming and outgoing partons to
    * be used in subsequent calls to me() and colourGeometries()
    * according to the associated XComb object. If the function is
    * overridden in a sub class the new function must call the base
    * class one first.
    */
   virtual void setKinematics();
 
   /**
    * The number of internal degrees of freedom used in the matrix
    * element.
    */
   virtual int nDim() const;
 
   /**
    * Generate internal degrees of freedom given nDim() uniform
    * random numbers in the interval \f$ ]0,1[ \f$. To help the phase space
    * generator, the dSigHatDR should be a smooth function of these
    * numbers, although this is not strictly necessary.
    * @param r a pointer to the first of nDim() consecutive random numbers.
    * @return true if the generation succeeded, otherwise false.
    */
   virtual bool generateKinematics(const double * r);
 
   /**
    * Return the matrix element squared differential in the variables
    * given by the last call to generateKinematics().
    */
   virtual CrossSection dSigHatDR() 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$ff\to h^0\to ff h^0\f$.
    * @param f1  Spinors for first  incoming fermion
    * @param f2  Spinors for second incoming fermion
    * @param a1  Spinors for first  outgoing fermion
    * @param a2  Spinors for second outgoing fermion
    * @param swap1 Whether or not to swap the order for the first fermion line
    * @param swap2 Whether or not to swap the order for the second fermion 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 swap1, bool swap2,
             bool me) const;
 
   /**
    *  Access to the vector ParticleData objects
    */
   //@{
   /**
    *  Access to the \f$W^+\f$ data
    */ 
   PDPtr WPlus() const {return _wplus;}
 
   /**
    *  Access to the \f$W^-\f$ data
    */ 
   PDPtr WMinus() const {return _wminus;}
 
   /**
    *  Access to the \f$Z^0\f$ data
    */ 
   PDPtr Z0() const {return _z0;}
 
   /**
    *  Access to the Higgs boson
    */
   PDPtr higgs() const {return _higgs;}
 
   /**
    *  Set the Higgs boson
    */
   void higgs(PDPtr in) {_higgs=in;}
   //@}
 
   /**
    *  Set the pointer to the vector-vector-Higgs vertex
    */
   void setWWHVertex(AbstractVVSVertexPtr in) {
     _vertexWWH = in;
   }
 
   /**
    *  Set the line shape treatment
    */
   void lineShape(unsigned int in) {_shapeopt=in;}
 
   /**
    *  Which process to generate
    */
   unsigned int process() const {return _process;}
 
   /**
    *  Whether momenta are swapped
    */
   bool swapOrder() {return _swap;}
 
   /**
    *  Which process to generate
    */
   void process(unsigned int in) {_process = in;}
 
   /**
    *  Maximum flavour of the incoming partons
    */
   unsigned int maxFlavour() const {return _maxflavour;}
 
   /**
    *  Minimum flavour of the incoming partons
    */
   unsigned int minFlavour() const {return _minflavour;}
 
 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();
   //@}
 
 private:
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   MEfftoffH & operator=(const MEfftoffH &) = delete;
 
 private:
 
   /**
    * Defines the Higgs resonance shape
    */
   unsigned int _shapeopt;
 
   /**
    *  Maximum flavour of the quarks involved 
    */
   unsigned int _maxflavour;
 
   /**
    *  Minimum flavour of the quarks involved 
    */
   unsigned int _minflavour;
 
   /**
    *  Whether to include $WW$ and $ZZ$ processes or both
    */
   unsigned int _process;
 
   /**
    *  The intermediate vector bosons
    */
   //@{
   /**
    *  \f$W^+\f$
    */
   PDPtr _wplus;
 
   /**
    *  \f$W^-\f$
    */
   PDPtr _wminus;
 
   /**
    *  \f$Z^0\f$
    */
   PDPtr _z0;
 
   /**
    *  Higgs boson
    */
   PDPtr _higgs;
   //@}
 
   /**
    *  The vertices for the calculation of the matrix element
    */
   //@{
   /**
    *  Vertex for fermion-fermion-W
    */
   AbstractFFVVertexPtr _vertexFFW;
 
   /**
    *  Vertex for fermion-fermion-Z
    */
   AbstractFFVVertexPtr _vertexFFZ;
 
   /**
    *  Vertex for vector-vector-Higgs
    */
   AbstractVVSVertexPtr _vertexWWH;
   //@}
 
   /**
    *  On-shell mass for the higgs
    */
   Energy _mh;
 
   /**
    *  On-shell width for the higgs
    */
   Energy _wh;
 
   /**
    *  The mass generator for the Higgs
    */
   GenericMassGeneratorPtr _hmass;
 
 
   /**
    * Matrix element for spin correlations
    */
   mutable ProductionMatrixElement _me;
 
   /**
    *  if order swaped
    */
   bool _swap;
 };
 
 }
 
 #endif /* HERWIG_MEfftoffH_H */

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