MatrixElement/Lepton/MEee2Higgs2SM.h

0001 // -*- C++ -*-
0002 //
0003 // MEee2Higgs2SM.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_MEee2Higgs2SM_H
0010 #define HERWIG_MEee2Higgs2SM_H
0011 //
0012 // This is the declaration of the MEee2Higgs2SM class.
0013 //
0014
0015 #include "ThePEG/MatrixElement/ME2to2Base.h"
0016 #include "Herwig/Models/StandardModel/StandardModel.h"
0017 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
0018 #include "ThePEG/Helicity/WaveFunction/SpinorWaveFunction.h"
0019 #include "ThePEG/Helicity/WaveFunction/SpinorBarWaveFunction.h"
0020
0021 namespace Herwig {
0022
0023 using namespace ThePEG;
0024
0025 /**
0026  * The MEee2Higgs2SM class implements the production of an \f$s\f$-channel
0027  * Higgs in \f$e^+e^-\f$ collisions in order to allow easy tests of Higgs
0028  * decays. It should not be used for physics studies.
0029  *
0030  * @see \ref MEee2Higgs2SMInterfaces "The interfaces"
0031  * defined for MEee2Higgs2SM.
0032  */
0033 class MEee2Higgs2SM: public ME2to2Base {
0034
0035 public:
0036
0037   /**
0038    * The default constructor.
0039    */
0040   inline MEee2Higgs2SM() : allowed_(0) {}
0041
0042   /** @name Virtual functions required by the MEBase class. */
0043   //@{
0044   /**
0045    * Return the order in \f$\alpha_S\f$ in which this matrix
0046    * element is given.
0047    */
0048   virtual unsigned int orderInAlphaS() const;
0049
0050   /**
0051    * Return the order in \f$\alpha_{EW}\f$ in which this matrix
0052    * element is given.
0053    */
0054   virtual unsigned int orderInAlphaEW() const;
0055
0056   /**
0057    * The matrix element for the kinematical configuration
0058    * previously provided by the last call to setKinematics(), suitably
0059    * scaled by sHat() to give a dimension-less number.
0060    * @return the matrix element scaled with sHat() to give a
0061    * dimensionless number.
0062    */
0063   virtual double me2() const;
0064
0065   /**
0066    * Return the scale associated with the last set phase space point.
0067    */
0068   virtual Energy2 scale() const;
0069
0070   /**
0071    * Add all possible diagrams with the add() function.
0072    */
0073   virtual void getDiagrams() const;
0074
0075   /**
0076    * Get diagram selector. With the information previously supplied with the
0077    * setKinematics method, a derived class may optionally
0078    * override this method to weight the given diagrams with their
0079    * (although certainly not physical) relative probabilities.
0080    * @param dv the diagrams to be weighted.
0081    * @return a Selector relating the given diagrams to their weights.
0082    */
0083   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
0084
0085   /**
0086    * Return a Selector with possible colour geometries for the selected
0087    * diagram weighted by their relative probabilities.
0088    * @param diag the diagram chosen.
0089    * @return the possible colour geometries weighted by their
0090    * relative probabilities.
0091    */
0092   virtual Selector<const ColourLines *>
0093   colourGeometries(tcDiagPtr diag) const;
0094
0095   /**
0096    * set up the spin correlations
0097    */
0098   virtual void constructVertex(tSubProPtr sub);
0099   //@}
0100
0101 public:
0102
0103   /** @name Functions used by the persistent I/O system. */
0104   //@{
0105   /**
0106    * Function used to write out object persistently.
0107    * @param os the persistent output stream written to.
0108    */
0109   void persistentOutput(PersistentOStream & os) const;
0110
0111   /**
0112    * Function used to read in object persistently.
0113    * @param is the persistent input stream read from.
0114    * @param version the version number of the object when written.
0115    */
0116   void persistentInput(PersistentIStream & is, int version);
0117   //@}
0118
0119   /**
0120    * The standard Init function used to initialize the interfaces.
0121    * Called exactly once for each class by the class description system
0122    * before the main function starts or
0123    * when this class is dynamically loaded.
0124    */
0125   static void Init();
0126
0127 protected:
0128
0129   /** @name Clone Methods. */
0130   //@{
0131   /**
0132    * Make a simple clone of this object.
0133    * @return a pointer to the new object.
0134    */
0135   inline virtual IBPtr clone() const {return new_ptr(*this);}
0136
0137   /** Make a clone of this object, possibly modifying the cloned object
0138    * to make it sane.
0139    * @return a pointer to the new object.
0140    */
0141   inline virtual IBPtr fullclone() const {return new_ptr(*this);}
0142   //@}
0143
0144 protected:
0145
0146   /** @name Standard Interfaced functions. */
0147   //@{
0148   /**
0149    * Initialize this object after the setup phase before saving an
0150    * EventGenerator to disk.
0151    * @throws InitException if object could not be initialized properly.
0152    */
0153   virtual void doinit();
0154
0155   /**
0156    * Rebind pointer to other Interfaced objects. Called in the setup phase
0157    * after all objects used in an EventGenerator has been cloned so that
0158    * the pointers will refer to the cloned objects afterwards.
0159    * @param trans a TranslationMap relating the original objects to
0160    * their respective clones.
0161    * @throws RebindException if no cloned object was found for a given
0162    * pointer.
0163    */
0164   virtual void rebind(const TranslationMap & trans)
0165    ;
0166
0167   /**
0168    * Return a vector of all pointers to Interfaced objects used in this
0169    * object.
0170    * @return a vector of pointers.
0171    */
0172   virtual IVector getReferences();
0173   //@}
0174
0175 private:
0176
0177   /**
0178    *  The matrix element
0179    * @param fin The incoming spinor wavefunction
0180    * @param ain The incoming spinorbar wavefunction
0181    * @param fout The outgoing spinor bar wavefunction
0182    * @param aout The outgoing spinor wavefunction
0183    * @param me The spin averaged matrix element
0184    */
0185   ProductionMatrixElement HelicityME(vector<SpinorWaveFunction> fin,
0186                      vector<SpinorBarWaveFunction> ain,
0187                      vector<SpinorBarWaveFunction> fout,
0188                      vector<SpinorWaveFunction> aout,double& me) const;
0189   /**
0190    *  \f$H\to gg\f$ matrix element
0191    * @param fin The incoming spinor wavefunction
0192    * @param ain The incoming spinorbar wavefunction
0193    * @param g1 Outgoing gluon wavefunction
0194    * @param g2 Outgoing gluon wavefunction
0195    * @param me The spin averaged matrix element
0196    */
0197   ProductionMatrixElement ggME(vector<SpinorWaveFunction> fin,
0198                    vector<SpinorBarWaveFunction> ain,
0199                    vector<VectorWaveFunction> g1,
0200                    vector<VectorWaveFunction> g2,
0201                    double & me) const;
0202   /**
0203    *  \f$H\to WW\f$ matrix element
0204    * @param fin The incoming spinor wavefunction
0205    * @param ain The incoming spinorbar wavefunction
0206    * @param g1 Outgoing W wavefunction
0207    * @param g2 Outgoing W wavefunction
0208    * @param me The spin averaged matrix element
0209    */
0210   ProductionMatrixElement WWME(vector<SpinorWaveFunction> fin,
0211                    vector<SpinorBarWaveFunction> ain,
0212                    vector<VectorWaveFunction> g1,
0213                    vector<VectorWaveFunction> g2,
0214                    double & me) const;
0215
0216 private:
0217
0218   /**
0219    * The assignment operator is private and must never be called.
0220    * In fact, it should not even be implemented.
0221    */
0222   MEee2Higgs2SM & operator=(const MEee2Higgs2SM &) = delete;
0223
0224 private:
0225
0226   /**
0227    *  Pointer to the Higgs fermion-antifermion vertex
0228    */
0229   AbstractFFSVertexPtr FFHVertex_;
0230
0231   /**
0232    *  Pointer to Higgs-gluon-gluon vertex
0233    */
0234   AbstractVVSVertexPtr HGGVertex_;
0235
0236   /**
0237    *  Pointer to Higgs-WW vertex
0238    */
0239   AbstractVVSVertexPtr HWWVertex_;
0240
0241   /**
0242    * Allowed outgoing particles
0243    */
0244   int allowed_;
0245
0246   /**
0247    *  Pointer to the Higgs ParticleData object
0248    */
0249   PDPtr h0_;
0250 };
0251
0252 }
0253
0254 #endif /* HERWIG_MEee2Higgs2SM_H */