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0001 // -*- C++ -*-
0002 //
0003 // MEvv2vv.h is a part of Herwig - A multi-purpose Monte Carlo event generator
0004 // Copyright (C) 2002-2019 The Herwig Collaboration
0005 //
0006 // Herwig is licenced under version 3 of the GPL, see COPYING for details.
0007 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
0008 //
0009 #ifndef HERWIG_MEvv2vv_H
0010 #define HERWIG_MEvv2vv_H
0011 //
0012 // This is the declaration of the MEvv2vv class.
0013 //
0014 
0015 #include "GeneralHardME.h"
0016 #include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
0017 #include "ThePEG/Helicity/Vertex/AbstractVVVVertex.h"
0018 #include "ThePEG/Helicity/Vertex/AbstractVVTVertex.h"
0019 #include "ThePEG/Helicity/Vertex/AbstractVVSVertex.h"
0020 #include "ThePEG/Helicity/Vertex/AbstractVVVVVertex.h"
0021 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
0022 
0023 namespace Herwig {
0024 using namespace ThePEG;
0025 using Helicity::VectorWaveFunction;
0026 
0027 /**
0028  * This is the implementation of the matrix element for 
0029  * \f$2\to 2\f$ massless vector-boson pair to vector-boson pair. It inherits from
0030  * GeneralHardME and implements the appropriate virtual member functions.
0031  *
0032  * @see \ref MEvv2vvInterfaces "The interfaces"
0033  * defined for MEvv2vv.
0034  */
0035 class MEvv2vv: public GeneralHardME {
0036 
0037 public:
0038 
0039   /**
0040    *  Typedef for VectorWaveFunction
0041    */
0042   typedef vector<VectorWaveFunction> VBVector;
0043 
0044 public:
0045 
0046   /** @name Virtual functions required by the GeneralHardME class. */
0047   //@{
0048   /**
0049    * The matrix element for the kinematical configuration
0050    * previously provided by the last call to setKinematics(), suitably
0051    * scaled by sHat() to give a dimension-less number.
0052    * @return the matrix element scaled with sHat() to give a
0053    * dimensionless number.
0054    */
0055   virtual double me2() const;
0056   //@}
0057 
0058   /**
0059    * Construct the vertex information for the spin correlations
0060    * @param sub Pointer to the relevent SubProcess
0061    */
0062   virtual void constructVertex(tSubProPtr sub);
0063 
0064 private:
0065 
0066   /**
0067    * Compute the matrix element for \f$V\, V\to V\, V\f$
0068    * @param vin1 VectorWaveFunctions for first incoming particle
0069    * @param vin2 VectorWaveFunctions for second incoming particle
0070    * @param vout1 VectorWaveFunctions for first outgoing particle
0071    * @param mc Whether vout1 is massless or not
0072    * @param vout2  VectorWaveFunctions for outgoing particle
0073    * @param md Whether vout2 is massless or not
0074    * @param me2 colour averaged, spin summed ME
0075    * @param first Whether or not first call to decide if colour decomposition etc
0076    * should be calculated
0077    * @return ProductionMatrixElement containing results of 
0078    * helicity calculations
0079    */
0080   ProductionMatrixElement 
0081   vv2vvHeME(VBVector & vin1, VBVector & vin2, 
0082         VBVector & vout1, bool mc, VBVector & vout2, bool md,
0083         double & me2, bool first ) const;
0084 
0085 protected:
0086   
0087   /**
0088    * A debugging function to test the value of me2 against an
0089    * analytic function.
0090    * @param me2 The value of the \f$ |\bar{\mathcal{M}}|^2 \f$
0091    */
0092   virtual void debug(double me2) const;
0093 
0094 public:
0095 
0096   /** @name Functions used by the persistent I/O system. */
0097   //@{
0098   /**
0099    * Function used to write out object persistently.
0100    * @param os the persistent output stream written to.
0101    */
0102   void persistentOutput(PersistentOStream & os) const;
0103 
0104   /**
0105    * Function used to read in object persistently.
0106    * @param is the persistent input stream read from.
0107    * @param version the version number of the object when written.
0108    */
0109   void persistentInput(PersistentIStream & is, int version);
0110   //@}
0111 
0112   /**
0113    * The standard Init function used to initialize the interfaces.
0114    * Called exactly once for each class by the class description system
0115    * before the main function starts or
0116    * when this class is dynamically loaded.
0117    */
0118   static void Init();
0119 
0120 protected:
0121 
0122   /** @name Clone Methods. */
0123   //@{
0124   /**
0125    * Make a simple clone of this object.
0126    * @return a pointer to the new object.
0127    */
0128   virtual IBPtr clone() const {return new_ptr(*this);}
0129 
0130   /** Make a clone of this object, possibly modifying the cloned object
0131    * to make it sane.
0132    * @return a pointer to the new object.
0133    */
0134   virtual IBPtr fullclone() const {return new_ptr(*this);}
0135   //@}
0136 
0137 protected:
0138 
0139   /** @name Standard Interfaced functions. */
0140   //@{
0141   /**
0142    * Initialize this object after the setup phase before saving an
0143    * EventGenerator to disk.
0144    * @throws InitException if object could not be initialized properly.
0145    */
0146   virtual void doinit();
0147   //@}
0148 
0149 private:
0150 
0151   /**
0152    * The assignment operator is private and must never be called.
0153    * In fact, it should not even be implemented.
0154    */
0155   MEvv2vv & operator=(const MEvv2vv &) = delete;
0156 
0157 private:
0158 
0159   /**
0160    * Store the dynamically casted VVSVertex pointers
0161    */
0162   vector<pair<AbstractVVSVertexPtr, AbstractVVSVertexPtr> > scalar_;
0163 
0164   /**
0165    * Store the dynamically casted VVVVertex pointers
0166    */
0167   vector<pair<AbstractVVVVertexPtr, AbstractVVVVertexPtr> > vector_;
0168 
0169   /**
0170    * Store the dynamically casted VVTVertex pointers
0171    */
0172   vector<pair<AbstractVVTVertexPtr, AbstractVVTVertexPtr> > tensor_;
0173 
0174   /**
0175    * Store the dynamically casted VVVVVertex pointer
0176    */
0177   vector<AbstractVVVVVertexPtr> four_;
0178 
0179   /**
0180    *   Four points for colour flows
0181    */
0182   map<unsigned int,vector<pair<unsigned int,double> > > fourFlow_;
0183   
0184 };
0185 
0186 }
0187 
0188 #endif /* HERWIG_MEvv2vv_H */