Decay/General/VVVDecayer.h

0001 // -*- C++ -*-
0002 //
0003 // VVVDecayer.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_VVVDecayer_H
0010 #define HERWIG_VVVDecayer_H
0011 //
0012 // This is the declaration of the VVVDecayer class.
0013 //
0014
0015 #include "GeneralTwoBodyDecayer.h"
0016 #include "ThePEG/Repository/EventGenerator.h"
0017 #include "ThePEG/Helicity/Vertex/Vector/VVVVertex.h"
0018 #include "ThePEG/Helicity/Vertex/AbstractVVVVVertex.h"
0019
0020 namespace Herwig {
0021 using namespace ThePEG;
0022 using Helicity::VVVVertexPtr;
0023
0024   /** \ingroup Decay
0025    * The VVVDecayer class implements the decay of a vector
0026    * to 2 vectors in a general model. It holds an VVVVertex pointer
0027    * that must be typecast from the VertexBase pointer held in
0028    * GeneralTwoBodyDecayer. It implents the virtual functions me2() and
0029    * partialWidth().
0030    *
0031    * @see GeneralTwoBodyDecayer
0032    */
0033 class VVVDecayer: public GeneralTwoBodyDecayer {
0034
0035 public:
0036
0037   /**
0038    * The default constructor.
0039    */
0040   VVVDecayer() {}
0041
0042   /** @name Virtual functions required by the Decayer class. */
0043   //@{
0044   /**
0045    * Return the matrix element squared for a given mode and phase-space channel.
0046    * @param ichan The channel we are calculating the matrix element for.
0047    * @param part The decaying Particle.
0048    * @param outgoing The particles produced in the decay
0049    * @param momenta  The momenta of the particles produced in the decay
0050    * @param meopt Option for the calculation of the matrix element
0051    * @return The matrix element squared for the phase-space configuration.
0052    */
0053   double me2(const int ichan,const Particle & part,
0054          const tPDVector & outgoing,
0055          const vector<Lorentz5Momentum> & momenta,
0056          MEOption meopt) const;
0057
0058   /**
0059    *   Construct the SpinInfos for the particles produced in the decay
0060    */
0061   virtual void constructSpinInfo(const Particle & part,
0062                  ParticleVector outgoing) const;
0063
0064   /**
0065    * Function to return partial Width
0066    * @param inpart The decaying particle.
0067    * @param outa One of the decay products.
0068    * @param outb The other decay product.
0069    */
0070   virtual Energy partialWidth(PMPair inpart, PMPair outa,
0071                   PMPair outb) const;
0072
0073   /**
0074    *  Set the information on the decay
0075    */
0076   virtual void setDecayInfo(PDPtr incoming, PDPair outgoing,
0077                 vector<VertexBasePtr>,
0078                 map<ShowerInteraction,VertexBasePtr> &,
0079                 const vector<map<ShowerInteraction,VertexBasePtr> > &,
0080                 map<ShowerInteraction,VertexBasePtr>);
0081
0082   /**
0083    *  Has a POWHEG style correction
0084    */
0085   virtual POWHEGType hasPOWHEGCorrection()  {
0086     POWHEGType output = FSR;
0087     for(auto vertex : vertex_) {
0088       if(vertex->orderInAllCouplings()!=1) {
0089     output = No;
0090     break;
0091       }
0092     }
0093     return output;
0094   }
0095
0096   /**
0097    *  Three-body matrix element including additional QCD radiation
0098    */
0099   virtual double threeBodyME(const int , const Particle & inpart,
0100                  const ParticleVector & decay,
0101                  ShowerInteraction inter, MEOption meopt);
0102   //@}
0103
0104 public:
0105
0106   /** @name Functions used by the persistent I/O system. */
0107   //@{
0108   /**
0109    * Function used to write out object persistently.
0110    * @param os the persistent output stream written to.
0111    */
0112   void persistentOutput(PersistentOStream & os) const;
0113
0114   /**
0115    * Function used to read in object persistently.
0116    * @param is the persistent input stream read from.
0117    * @param version the version number of the object when written.
0118    */
0119   void persistentInput(PersistentIStream & is, int version);
0120   //@}
0121
0122   /**
0123    * The standard Init function used to initialize the interfaces.
0124    * Called exactly once for each class by the class description system
0125    * before the main function starts or
0126    * when this class is dynamically loaded.
0127    */
0128   static void Init();
0129
0130 protected:
0131
0132   /** @name Clone Methods. */
0133   //@{
0134   /**
0135    * Make a simple clone of this object.
0136    * @return a pointer to the new object.
0137    */
0138   virtual IBPtr clone() const;
0139
0140   /** Make a clone of this object, possibly modifying the cloned object
0141    * to make it sane.
0142    * @return a pointer to the new object.
0143    */
0144   virtual IBPtr fullclone() const;
0145   //@}
0146
0147 protected:
0148
0149   /**
0150    *  Find the vertices for the decay
0151    */
0152   void identifyVertices(const Particle & inpart, const ParticleVector & decay,
0153             AbstractVVVVertexPtr & outgoingVertex1,
0154             AbstractVVVVertexPtr & outgoingVertex2,
0155             ShowerInteraction inter);
0156
0157 private:
0158
0159   /**
0160    * The assignment operator is private and must never be called.
0161    * In fact, it should not even be implemented.
0162    */
0163   VVVDecayer & operator=(const VVVDecayer &) = delete;
0164
0165 private:
0166
0167   /**
0168    *  Abstract pointer to AbstractVVVVertex
0169    */
0170   vector<AbstractVVVVertexPtr> vertex_;
0171
0172   /**
0173    * Pointer to the perturbative vertex
0174    */
0175   vector<VVVVertexPtr> perturbativeVertex_;
0176
0177   /**
0178    *  Abstract pointer to AbstractVVVVertex for QCD radiation from incoming vector
0179    */
0180   map<ShowerInteraction,AbstractVVVVertexPtr> incomingVertex_;
0181
0182   /**
0183    *  Abstract pointer to AbstractVVVVertex for QCD radiation from the first outgoing vector
0184    */
0185   map<ShowerInteraction,AbstractVVVVertexPtr> outgoingVertex1_;
0186
0187   /**
0188    *  Abstract pointer to AbstractVVVVertex for QCD radiation from the second outgoing vector
0189    */
0190   map<ShowerInteraction,AbstractVVVVertexPtr> outgoingVertex2_;
0191
0192   /**
0193    *  Abstract pointer to AbstractVVVVertex for QCD radiation from the 4-point vertex
0194    */
0195   map<ShowerInteraction,AbstractVVVVVertexPtr> fourPointVertex_;
0196
0197   /**
0198    *  Spin density matrix
0199    */
0200   mutable RhoDMatrix rho_;
0201
0202   /**
0203    * Vector wavefunctions
0204    */
0205   mutable vector<Helicity::VectorWaveFunction> vectors_[3];
0206
0207 private:
0208
0209   /**
0210    *  Members for the POWHEG correction
0211    */
0212   //@{
0213   /**
0214    *  Spin density matrix for 3 body decay
0215    */
0216   mutable RhoDMatrix rho3_;
0217
0218   /**
0219    *  Vector wavefunction for 3 body decay
0220    */
0221   mutable vector<Helicity::VectorWaveFunction> vector3_;
0222
0223   /**
0224    *  Vector wavefunctions
0225    */
0226   mutable vector<Helicity::VectorWaveFunction> vectors3_[2];
0227
0228     /**
0229    *  Vector wavefunction for 3 body decay
0230    */
0231   mutable vector<Helicity::VectorWaveFunction> gluon_;
0232   //@}
0233 };
0234
0235 }
0236
0237 #endif /* HERWIG_VVVDecayer_H */