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0001 // -*- C++ -*-
0002 //
0003 // MEff2vs.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_MEff2vs_H
0010 #define HERWIG_MEff2vs_H
0011 //
0012 // This is the declaration of the MEff2vs class.
0013 //
0014 
0015 #include "GeneralHardME.h"
0016 #include "ThePEG/Helicity/Vertex/AbstractFFSVertex.h"
0017 #include "ThePEG/Helicity/Vertex/AbstractFFVVertex.h"
0018 #include "ThePEG/Helicity/Vertex/AbstractVSSVertex.h"
0019 #include "ThePEG/Helicity/Vertex/AbstractVVSVertex.h"
0020 #include "ThePEG/Helicity/Vertex/AbstractFFVSVertex.h"
0021 #include "ThePEG/Helicity/WaveFunction/SpinorWaveFunction.h"
0022 #include "ThePEG/Helicity/WaveFunction/SpinorBarWaveFunction.h"
0023 #include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
0024 #include "ThePEG/Helicity/WaveFunction/ScalarWaveFunction.h"
0025 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
0026 
0027 namespace Herwig {
0028 using namespace ThePEG;
0029 using Helicity::SpinorWaveFunction;
0030 using Helicity::SpinorBarWaveFunction;
0031 using Helicity::VectorWaveFunction;
0032 using Helicity::ScalarWaveFunction;
0033 
0034 /**
0035  * The MEff2vs class is designed to implement the matrix element for a
0036  * fermion-antifermion to vector-scalar hard process. It inherits from 
0037  * GeneralHardME and implements the appropriate virtual functions for this 
0038  * specific spin combination.
0039  *
0040  * @see \ref MEff2vsInterfaces "The interfaces"
0041  * defined for MEff2vs.
0042  * @see GeneralHardME
0043  */
0044 class MEff2vs: public GeneralHardME {
0045 
0046 public:
0047 
0048   /** @name Typedefs */
0049   //@{
0050   /**
0051    * A vector of SpinorWaveFunctions 
0052    */
0053   typedef vector<SpinorWaveFunction> SpinorVector;
0054 
0055   /**
0056    * A vector of SpinorWaveBarFunctions 
0057    */
0058   typedef vector<SpinorBarWaveFunction> SpinorBarVector;
0059 
0060   /**
0061    * A vector of VectorWaveFunctions 
0062    */
0063   typedef vector<VectorWaveFunction> VBVector;
0064   //@}
0065 
0066 public:
0067 
0068   /**
0069    * The default constructor.
0070    */
0071   MEff2vs() : scalar_(0), vector_(0), fermion_(0) {}
0072 
0073   /** @name Virtual functions required by the MEBase class. */
0074   //@{
0075   /**
0076    * The matrix element for the kinematical configuration
0077    * previously provided by the last call to setKinematics(), suitably
0078    * scaled by sHat() to give a dimension-less number.
0079    * @return the matrix element scaled with sHat() to give a
0080    * dimensionless number.
0081    */
0082   virtual double me2() const;
0083   //@}
0084 
0085   /**
0086    * Construct the vertex information for the spin correlations
0087    * @param sub Pointer to the relevent SubProcess
0088    */
0089   virtual void constructVertex(tSubProPtr sub);
0090 
0091 public:
0092 
0093   /** @name Functions used by the persistent I/O system. */
0094   //@{
0095   /**
0096    * Function used to write out object persistently.
0097    * @param os the persistent output stream written to.
0098    */
0099   void persistentOutput(PersistentOStream & os) const;
0100 
0101   /**
0102    * Function used to read in object persistently.
0103    * @param is the persistent input stream read from.
0104    * @param version the version number of the object when written.
0105    */
0106   void persistentInput(PersistentIStream & is, int version);
0107   //@}
0108 
0109   /**
0110    * The standard Init function used to initialize the interfaces.
0111    * Called exactly once for each class by the class description system
0112    * before the main function starts or
0113    * when this class is dynamically loaded.
0114    */
0115   static void Init();
0116 
0117 protected:
0118 
0119   /** @name Standard Interfaced functions. */
0120   //@{
0121   /**
0122    * Initialize this object after the setup phase before saving an
0123    * EventGenerator to disk.
0124    * @throws InitException if object could not be initialized properly.
0125    */
0126   virtual void doinit();
0127   //@}
0128 
0129 protected:
0130 
0131   /** @name Clone Methods. */
0132   //@{
0133   /**
0134    * Make a simple clone of this object.
0135    * @return a pointer to the new object.
0136    */
0137   virtual IBPtr clone() const {return new_ptr(*this);}
0138 
0139   /** Make a clone of this object, possibly modifying the cloned object
0140    * to make it sane.
0141    * @return a pointer to the new object.
0142    */
0143   virtual IBPtr fullclone() const {return new_ptr(*this);}
0144   //@}
0145 
0146 private:
0147 
0148   /**
0149    * The assignment operator is private and must never be called.
0150    * In fact, it should not even be implemented.
0151    */
0152   MEff2vs & operator=(const MEff2vs &) = delete;
0153 
0154 private:
0155 
0156   /** @name Functions to compute the ProductionMatrixElement. */
0157   //@{
0158   /**
0159    * Compute the matrix element for \f$\Psi\bar{\Psi}\to\Psi\bar{\Psi}\f$
0160    * @param sp Spinors for first incoming particle
0161    * @param spbar SpinorBar Wavefunctions for second incoming particle
0162    * @param vec VectorWaveFunctions for outgoing vector
0163    * @param sca Outgoing ScalarWaveFunction
0164    * @param me2 colour averaged, spin summed ME
0165    * @param first Whether or not first call to decide if colour decomposition etc
0166    * should be calculated
0167    * @return ProductionMatrixElement containing results of 
0168    * helicity calculations
0169    */
0170   ProductionMatrixElement
0171   ffb2vsHeME(SpinorVector & sp, SpinorBarVector & spbar,
0172          VBVector & vec, ScalarWaveFunction & sca, 
0173          double & me2,bool first) const;
0174   //@}
0175 
0176 
0177 private:
0178 
0179   /**
0180    * Storage for dynamically cast vertices for a diagram with intermediate
0181    * scalar
0182    */
0183   vector<pair<AbstractFFSVertexPtr, AbstractVSSVertexPtr> > scalar_;
0184 
0185   /**
0186    * Storage for dynamically cast vertices for a diagram with intermediate
0187    * vector
0188    */
0189   vector<pair<AbstractFFVVertexPtr, AbstractVVSVertexPtr> > vector_;
0190   
0191   /**
0192    * Storage for dynamically cast vertices for a diagram with intermediate
0193    * fermion
0194    */
0195   vector<pair<AbstractFFVVertexPtr, AbstractFFSVertexPtr> > fermion_;
0196 
0197   /**
0198    *  Four point vertices
0199    */
0200   vector<AbstractFFVSVertexPtr> four_;
0201 };
0202 
0203 }
0204 
0205 #endif /* HERWIG_MEff2vs_H */