ThePEG/MatrixElement/MEQQ2GG.h

0001 // -*- C++ -*-
0002 //
0003 // MEQQ2GG.h is a part of ThePEG - Toolkit for HEP Event Generation
0004 // Copyright (C) 1999-2019 Leif Lonnblad
0005 //
0006 // ThePEG 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 ThePEG_MEQQ2GG_H
0010 #define ThePEG_MEQQ2GG_H
0011 // This is the declaration of the MEQQ2GG class.
0012
0013 #include "ThePEG/MatrixElement/ME2to2QCD.h"
0014
0015 namespace ThePEG {
0016
0017 /**
0018  * MEQQ2GG inherits from ME2to2QCD and implements the standard
0019  * \f$q\bar{q}\rightarrow gg\f$ matrix element.
0020  *
0021  * @see \ref MEQQ2GGInterfaces "The interfaces"
0022  * defined for MEQQ2GG.
0023  * @see ME2to2QCD
0024  */
0025 class MEQQ2GG: public ME2to2QCD {
0026
0027 public:
0028
0029   /** @name Virtual functions required by the MEBase class. */
0030   //@{
0031   /**
0032    * The matrix element for the kinematical configuration
0033    * previously provided by the last call to setKinematics(), suitably
0034    * scaled by sHat() to give a dimension-less number.
0035    * @return the matrix element scaled with sHat() to give a
0036    * dimensionless number.
0037    */
0038   virtual double me2() const;
0039
0040   /**
0041    * Add all possible diagrams with the add() function.
0042    */
0043   virtual void getDiagrams() const;
0044
0045   /**
0046    * Return a Selector with possible colour geometries for the selected
0047    * diagram weighted by their relative probabilities.
0048    * @param diag the diagram chosen.
0049    * @return the possible colour geometries weighted by their
0050    * relative probabilities.
0051    */
0052   virtual Selector<const ColourLines *>
0053   colourGeometries(tcDiagPtr diag) const;
0054
0055   /**
0056    * Get diagram selector. With the information previously supplied with the
0057    * setKinematics method, a derived class may optionally
0058    * override this method to weight the given diagrams with their
0059    * (although certainly not physical) relative probabilities.
0060    * @param dv the diagrams to be weighted.
0061    * @return a Selector relating the given diagrams to their weights.
0062    */
0063   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
0064   //@}
0065
0066 protected:
0067
0068   /** @name Internal functions returning the matrix element squared
0069    *  for different colour configurations. */
0070   //@{
0071   /**
0072    * Return the matrix element squared (without common pre-factors)
0073    * for the specific colour configuration.
0074    */
0075   double colA() const
0076   {
0077     return uHat()/tHat() - 2.0*sqr(uHat()/sHat());
0078   }
0079
0080
0081   /**
0082    * Return the matrix element squared (without common pre-factors)
0083    * for the specific colour configuration.
0084    */
0085   double colB() const
0086   {
0087     return tHat()/uHat() - 2.0*sqr(tHat()/sHat());
0088   }
0089
0090   //@}
0091
0092 public:
0093
0094   /**
0095    * Standard Init function used to initialize the interfaces.
0096    */
0097   static void Init();
0098
0099 protected:
0100
0101   /** @name Clone Methods. */
0102   //@{
0103   /**
0104    * Make a simple clone of this object.
0105    * @return a pointer to the new object.
0106    */
0107   virtual IBPtr clone() const;
0108
0109   /** Make a clone of this object, possibly modifying the cloned object
0110    * to make it sane.
0111    * @return a pointer to the new object.
0112    */
0113   virtual IBPtr fullclone() const;
0114   //@}
0115
0116 private:
0117
0118   /**
0119    * Describe a concrete class without persistent data.
0120    */
0121   static NoPIOClassDescription<MEQQ2GG> initMEQQ2GG;
0122
0123   /**
0124    *  Private and non-existent assignment operator.
0125    */
0126   MEQQ2GG & operator=(const MEQQ2GG &) = delete;
0127
0128 };
0129
0130 }
0131
0132
0133 namespace ThePEG {
0134
0135 /** @cond TRAITSPECIALIZATIONS */
0136
0137 /** This template specialization informs ThePEG about the
0138  *  base classes of MEQQ2GG. */
0139 template <>
0140 struct BaseClassTrait<MEQQ2GG,1>: public ClassTraitsType {
0141   /** Typedef of the first base class of MEQQ2GG. */
0142   typedef ME2to2QCD NthBase;
0143 };
0144
0145 /** This template specialization informs ThePEG about the name of
0146  *  the MEQQ2GG class and the shared object where it is defined. */
0147 template <>
0148 struct ClassTraits<MEQQ2GG>: public ClassTraitsBase<MEQQ2GG> {
0149   /** Return a platform-independent class name */
0150   static string className() { return "ThePEG::MEQQ2GG"; }
0151   /** Return the name of the shared library be loaded to get
0152    *  access to the MEQQ2GG class and every other class it uses
0153    *  (except the base class). */
0154   static string library() { return "MEQCD.so"; }
0155 };
0156
0157 /** @endcond */
0158
0159 }
0160
0161 #endif /* ThePEG_MEQQ2GG_H */