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0001 // -*- C++ -*-
0002 #ifndef HERWIG_MEChargedCurrentDIS_H
0003 #define HERWIG_MEChargedCurrentDIS_H
0004 //
0005 // This is the declaration of the MEChargedCurrentDIS class.
0006 //
0007 
0008 #include "DISBase.h"
0009 #include "ThePEG/Helicity/Vertex/AbstractFFVVertex.fh"
0010 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
0011 #include "ThePEG/Helicity/WaveFunction/SpinorWaveFunction.h"
0012 #include "ThePEG/Helicity/WaveFunction/SpinorBarWaveFunction.h"
0013 
0014 namespace Herwig {
0015 
0016 using namespace ThePEG;
0017 
0018 /**
0019  * The MEChargedCurrentDIS class provides the matrix elements for
0020  * charged current DIS.
0021  *
0022  *  By default both the incoming and outgong quarks are assumed to be massless
0023  *  although the mass of the outgoing quark can be included if required. This
0024  *  option should be used if top production is included.
0025  *
0026  * @see \ref MEChargedCurrentDISInterfaces "The interfaces"
0027  * defined for MEChargedCurrentDIS.
0028  */
0029 class MEChargedCurrentDIS: public DISBase {
0030 
0031 public:
0032 
0033   /**
0034    * The default constructor.
0035    */
0036   MEChargedCurrentDIS();
0037 
0038   /** @name Virtual functions required by the MEBase class. */
0039   //@{
0040   /**
0041    * Return the order in \f$\alpha_S\f$ in which this matrix
0042    * element is given.
0043    */
0044   virtual unsigned int orderInAlphaS() const;
0045 
0046   /**
0047    * Return the order in \f$\alpha_{EW}\f$ in which this matrix
0048    * element is given.
0049    */
0050   virtual unsigned int orderInAlphaEW() const;
0051 
0052   /**
0053    * The matrix element for the kinematical configuration
0054    * previously provided by the last call to setKinematics(), suitably
0055    * scaled by sHat() to give a dimension-less number.
0056    * @return the matrix element scaled with sHat() to give a
0057    * dimensionless number.
0058    */
0059   virtual double me2() const;
0060 
0061   /**
0062    * Add all possible diagrams with the add() function.
0063    */
0064   virtual void getDiagrams() const;
0065 
0066   /**
0067    * Get diagram selector. With the information previously supplied with the
0068    * setKinematics method, a derived class may optionally
0069    * override this method to weight the given diagrams with their
0070    * (although certainly not physical) relative probabilities.
0071    * @param dv the diagrams to be weighted.
0072    * @return a Selector relating the given diagrams to their weights.
0073    */
0074   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
0075 
0076   /**
0077    * Return a Selector with possible colour geometries for the selected
0078    * diagram weighted by their relative probabilities.
0079    * @param diag the diagram chosen.
0080    * @return the possible colour geometries weighted by their
0081    * relative probabilities.
0082    */
0083   virtual Selector<const ColourLines *>
0084   colourGeometries(tcDiagPtr diag) const;
0085 
0086   /**
0087    *  Construct the vertex of spin correlations.
0088    */
0089   virtual void constructVertex(tSubProPtr);
0090   //@}
0091 
0092 
0093 public:
0094 
0095   /** @name Functions used by the persistent I/O system. */
0096   //@{
0097   /**
0098    * Function used to write out object persistently.
0099    * @param os the persistent output stream written to.
0100    */
0101   void persistentOutput(PersistentOStream & os) const;
0102 
0103   /**
0104    * Function used to read in object persistently.
0105    * @param is the persistent input stream read from.
0106    * @param version the version number of the object when written.
0107    */
0108   void persistentInput(PersistentIStream & is, int version);
0109   //@}
0110 
0111   /**
0112    * The standard Init function used to initialize the interfaces.
0113    * Called exactly once for each class by the class description system
0114    * before the main function starts or
0115    * when this class is dynamically loaded.
0116    */
0117   static void Init();
0118 
0119 protected:
0120 
0121   /**
0122    * Matrix element for \f$\ell q\to \gamma/Z \to \ell q\f$.
0123    * @param f1 Fermion on lepton line
0124    * @param a1 Anti-fermion on lepton line
0125    * @param f2 Fermion on quark line
0126    * @param a2 Anti-fermion on quark line
0127    * @param lorder The order of particles on the lepton line
0128    * @param qorder The order of particles on the quark line
0129    * @param me  Whether or not to calculate the matrix element for spin correlations
0130    */
0131   double helicityME(vector<SpinorWaveFunction>    & f1 ,
0132             vector<SpinorWaveFunction>    & f2,
0133             vector<SpinorBarWaveFunction> & a1 ,
0134             vector<SpinorBarWaveFunction> & a2,
0135             bool lorder, bool qorder,
0136             bool me) const;
0137 
0138   /**
0139    *  Calculate the coefficient A for the correlations in the hard
0140    *  radiation
0141    */
0142   virtual double A(tcPDPtr lin, tcPDPtr lout, tcPDPtr qin, tcPDPtr qout,
0143            Energy2 scale) const;
0144 
0145 protected:
0146 
0147   /** @name Clone Methods. */
0148   //@{
0149   /**
0150    * Make a simple clone of this object.
0151    * @return a pointer to the new object.
0152    */
0153   virtual IBPtr clone() const {return new_ptr(*this);}
0154 
0155   /** Make a clone of this object, possibly modifying the cloned object
0156    * to make it sane.
0157    * @return a pointer to the new object.
0158    */
0159   virtual IBPtr fullclone() const {return new_ptr(*this);}
0160   //@}
0161 
0162 protected:
0163 
0164   /** @name Standard Interfaced functions. */
0165   //@{
0166   /**
0167    * Initialize this object after the setup phase before saving an
0168    * EventGenerator to disk.
0169    * @throws InitException if object could not be initialized properly.
0170    */
0171   virtual void doinit();
0172   //@}
0173 
0174 private:
0175 
0176   /**
0177    * The assignment operator is private and must never be called.
0178    * In fact, it should not even be implemented.
0179    */
0180   MEChargedCurrentDIS & operator=(const MEChargedCurrentDIS &) = delete;
0181 
0182 private:
0183 
0184   /**
0185    *  Pointer to the vertex for the helicity calculations
0186    */
0187   AbstractFFVVertexPtr _theFFWVertex;
0188 
0189   /**
0190    *  The allowed flavours of the incoming quarks
0191    */
0192   unsigned int _maxflavour;
0193 
0194   /**
0195    *  Option for the mass of the outgoing quarks
0196    */
0197   unsigned int _massopt;
0198 
0199   /**
0200    * Matrix element for spin correlations
0201    */
0202   ProductionMatrixElement _me;
0203 
0204   /**
0205    *  Pointers to the intermediates resonances
0206    */
0207   //@{
0208   /**
0209    *  Pointer to the \f$W^+\f$
0210    */
0211   tcPDPtr _wp;
0212 
0213   /**
0214    *  Pointer to the \f$W^-\f$
0215    */
0216   tcPDPtr _wm;
0217   //@}
0218 };
0219 
0220 }
0221 
0222 #endif /* HERWIG_MEChargedCurrentDIS_H */