MatrixElement/Lepton/MEee2Mesons.h

0001 // -*- C++ -*-
0002 #ifndef Herwig_MEee2Mesons_H
0003 #define Herwig_MEee2Mesons_H
0004 //
0005 // This is the declaration of the MEee2Mesons class.
0006 //
0007
0008 #include "Herwig/MatrixElement/MEMultiChannel.h"
0009 #include "Herwig/Decay/WeakCurrents/WeakCurrent.h"
0010 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
0011
0012 namespace Herwig {
0013
0014 using namespace ThePEG;
0015
0016 /**
0017  * The MEee2Mesons class implements \f$e^+e^-\f$ annhilation to mesons at low energy
0018  * using hadronic currents.
0019  *
0020  * @see \ref MEee2MesonsInterfaces "The interfaces"
0021  * defined for MEee2Mesons.
0022  */
0023 class MEee2Mesons: public MEMultiChannel {
0024
0025 public:
0026
0027   /**
0028    * The default constructor.
0029    */
0030   MEee2Mesons();
0031
0032 public:
0033
0034   /** @name Virtual functions required by the MEBase class. */
0035   //@{
0036   /**
0037    * Return the order in \f$\alpha_S\f$ in which this matrix
0038    * element is given.
0039    */
0040   virtual unsigned int orderInAlphaS() const;
0041
0042   /**
0043    * Return the order in \f$\alpha_{EW}\f$ in which this matrix
0044    * element is given.
0045    */
0046   virtual unsigned int orderInAlphaEW() const;
0047
0048   /**
0049    * Return the scale associated with the last set phase space point.
0050    */
0051   virtual Energy2 scale() const;
0052   //@}
0053
0054   /**
0055    *  Construct the vertex of spin correlations.
0056    */
0057   virtual void constructVertex(tSubProPtr);
0058
0059
0060 public:
0061
0062   /** @name Functions used by the persistent I/O system. */
0063   //@{
0064   /**
0065    * Function used to write out object persistently.
0066    * @param os the persistent output stream written to.
0067    */
0068   void persistentOutput(PersistentOStream & os) const;
0069
0070   /**
0071    * Function used to read in object persistently.
0072    * @param is the persistent input stream read from.
0073    * @param version the version number of the object when written.
0074    */
0075   void persistentInput(PersistentIStream & is, int version);
0076   //@}
0077
0078   /**
0079    * The standard Init function used to initialize the interfaces.
0080    * Called exactly once for each class by the class description system
0081    * before the main function starts or
0082    * when this class is dynamically loaded.
0083    */
0084   static void Init();
0085
0086
0087 protected:
0088
0089   /**
0090    * Return the matrix element squared for a given mode and phase-space channel.
0091    * @param ichan The channel we are calculating the matrix element for.
0092    */
0093   virtual double me2(const int ichan) const;
0094
0095   /**
0096    * Return the matrix element squared for a given mode and phase-space channel,
0097    * with the helicities amplitudes
0098    * @param ichan The channel we are calculating the matrix element for.
0099    */
0100   virtual double helicityME(const int ichan, const cPDVector & particles,
0101                 const vector<Lorentz5Momentum> & momenta) const;
0102
0103 protected:
0104
0105   /** @name Clone Methods. */
0106   //@{
0107   /**
0108    * Make a simple clone of this object.
0109    * @return a pointer to the new object.
0110    */
0111   virtual IBPtr clone() const;
0112
0113   /** Make a clone of this object, possibly modifying the cloned object
0114    * to make it sane.
0115    * @return a pointer to the new object.
0116    */
0117   virtual IBPtr fullclone() const;
0118   //@}
0119
0120 protected:
0121
0122   /** @name Standard Interfaced functions. */
0123   //@{
0124   /**
0125    * Initialize this object after the setup phase before saving an
0126    * EventGenerator to disk.
0127    * @throws InitException if object could not be initialized properly.
0128    */
0129   virtual void doinit();
0130
0131   /**
0132    * Initialize this object. Called in the run phase just before
0133    * a run begins.
0134    */
0135   virtual void doinitrun();
0136   //@}
0137
0138   /**
0139    *  Set up the flavours allowed in the current
0140    */
0141   void setFlavour();
0142
0143 private:
0144
0145   /**
0146    * The assignment operator is private and must never be called.
0147    * In fact, it should not even be implemented.
0148    */
0149   MEee2Mesons & operator=(const MEee2Mesons &) = delete;
0150
0151 private :
0152
0153   /**
0154    *  Option for the flavour of the particles in the current
0155    */
0156   unsigned int flavOpt_;
0157
0158   /**
0159    * the hadronic current
0160    */
0161   WeakCurrentPtr current_;
0162
0163   /**
0164    *  The matrix element
0165    */
0166   mutable ProductionMatrixElement me_;
0167
0168   /**
0169    *  Map for the modes
0170    */
0171   map<int,int>  modeMap_;
0172
0173   /**
0174    *  The flavour of the hadronic system
0175    */
0176   FlavourInfo flavour_;
0177 };
0178
0179 }
0180
0181 #endif /* Herwig_MEee2Mesons_H */