ThePEG/MatrixElement/MEQG2QG.h

0001 // -*- C++ -*-
0002 //
0003 // MEQG2QG.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_MEQG2QG_H
0010 #define ThePEG_MEQG2QG_H
0011 // This is the declaration of the MEQG2QG class.
0012
0013 #include "ThePEG/MatrixElement/ME2to2QCD.h"
0014
0015 namespace ThePEG {
0016
0017 /**
0018  * MEQG2QG inherits from ME2to2QCD and implements the
0019  * standard \f$qg\rightarrow qg\f$ matrix element.
0020  *
0021  * @see \ref MEQG2QGInterfaces "The interfaces"
0022  * defined for MEQG2QG.
0023  * @see ME2to2QCD
0024  */
0025 class MEQG2QG: 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 colA1() const
0076   {
0077     return ( interference()? 2.25: 2.0 )*sqr(uHat()/tHat());
0078   }
0079
0080   /**
0081    * Return the matrix element squared (without common pre-factors)
0082    * for the specific colour configuration.
0083    */
0084   double colB1() const
0085   {
0086     return ( interference()? 2.25: 2.0 )*sqr(sHat()/tHat());
0087   }
0088
0089   /**
0090    * Return the matrix element squared (without common pre-factors)
0091    * for the specific colour configuration.
0092    */
0093   double colA2() const { return  -uHat()/sHat(); }
0094
0095   /**
0096    * Return the matrix element squared (without common pre-factors)
0097    * for the specific colour configuration.
0098    */
0099   double colB2() const { return -sHat()/uHat(); }
0100   //@}
0101
0102 public:
0103
0104   /**
0105    * Standard Init function used to initialize the interfaces.
0106    */
0107   static void Init();
0108
0109 protected:
0110
0111   /** @name Clone Methods. */
0112   //@{
0113   /**
0114    * Make a simple clone of this object.
0115    * @return a pointer to the new object.
0116    */
0117   virtual IBPtr clone() const;
0118
0119   /** Make a clone of this object, possibly modifying the cloned object
0120    * to make it sane.
0121    * @return a pointer to the new object.
0122    */
0123   virtual IBPtr fullclone() const;
0124   //@}
0125
0126 private:
0127
0128   /**
0129    * Describe a concrete class without persistent data.
0130    */
0131   static NoPIOClassDescription<MEQG2QG> initMEQG2QG;
0132
0133   /**
0134    *  Private and non-existent assignment operator.
0135    */
0136   MEQG2QG & operator=(const MEQG2QG &) = delete;
0137
0138 };
0139
0140 }
0141
0142
0143 namespace ThePEG {
0144
0145 /** @cond TRAITSPECIALIZATIONS */
0146
0147 /** This template specialization informs ThePEG about the
0148  *  base classes of MEQG2QG. */
0149 template <>
0150 struct BaseClassTrait<MEQG2QG,1>: public ClassTraitsType {
0151   /** Typedef of the first base class of MEQG2QG. */
0152   typedef ME2to2QCD NthBase;
0153 };
0154
0155 /** This template specialization informs ThePEG about the name of
0156  *  the MEQG2QG class and the shared object where it is defined. */
0157 template <>
0158 struct ClassTraits<MEQG2QG>: public ClassTraitsBase<MEQG2QG> {
0159   /** Return a platform-independent class name */
0160   static string className() { return "ThePEG::MEQG2QG"; }
0161   /** Return the name of the shared library be loaded to get
0162    *  access to the MEQG2QG class and every other class it uses
0163    *  (except the base class). */
0164   static string library() { return "MEQCD.so"; }
0165 };
0166
0167 /** @endcond */
0168
0169 }
0170
0171 #endif /* ThePEG_MEQG2QG_H */