ThePEG/PDT/V2PPDecayer.h

0001 // -*- C++ -*-
0002 //
0003 // V2PPDecayer.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_V2PPDecayer_H
0010 #define THEPEG_V2PPDecayer_H
0011 // This is the declaration of the V2PPDecayer class.
0012
0013 #include "ThePEG/PDT/FlatDecayer.h"
0014
0015 namespace ThePEG {
0016
0017 /**
0018  * The V2PPDecayer class performs the decay of a vector meson into two
0019  * pseudo-scalars according to a flat phase space. If, however the
0020  * decaying particle comes from a pseudo-scalar and has only one
0021  * sibling which is a pseudo-scalar (or a photon) the decay is
0022  * reweighted with \f$\cos^2\f$ (\f$\sin^2\f$ for photon) of the angle
0023  * between one of the decay products and its grand parent.
0024  *
0025  * @see \ref V2PPDecayerInterfaces "The interfaces"
0026  * defined for V2PPDecayer.
0027  * @see FlatDecayer
0028  * @see ParticleData
0029  */
0030 class V2PPDecayer: public FlatDecayer {
0031
0032 public:
0033
0034   /** @name Virtual functions required by the Decayer class.
0035    */
0036   //@{
0037   /**
0038    * Check if this decayer can perfom the decay specified by the
0039    * given decay mode.
0040    * @param dm the DecayMode describing the decay.
0041    * @return true if this decayer can handle the given mode, otherwise false.
0042    */
0043   virtual bool accept(const DecayMode & dm) const;
0044
0045   /**
0046    * Perform a decay for a given DecayMode and a given Particle instance.
0047    * @param dm the DecayMode describing the decay.
0048    * @param p the Particle instance to be decayed.
0049    * @return a ParticleVector containing the decay products.
0050    */
0051   virtual ParticleVector decay(const DecayMode & dm, const Particle & p) const;
0052
0053   /**
0054    * Give a weight to a phase space point. To be overridden by
0055    * subclasses. For a given decay mode, \a dm, decaying \a parent
0056    * particle and decayproducts, \a children, distributed according to
0057    * a flat distribution in phase space, return a weight (less or
0058    * equal to unity) modifying the flat distribution to the desired
0059    * one. Note that the chosen phase space point may be rejected, but
0060    * the chosen decay channel will not. This means that the weight
0061    * returned by this function does not influence the branching
0062    * ratios.
0063    */
0064   virtual double reweight(const DecayMode & dm, const Particle & parent,
0065               const ParticleVector & children) const;
0066   //@}
0067
0068 public:
0069
0070
0071   /** @name Functions used by the persistent I/O system. */
0072   //@{
0073   /**
0074    * Function used to write out object persistently.
0075    * @param os the persistent output stream written to.
0076    */
0077   void persistentOutput(PersistentOStream & os) const;
0078
0079   /**
0080    * Function used to read in object persistently.
0081    * @param is the persistent input stream read from.
0082    * @param version the version number of the object when written.
0083    */
0084   void persistentInput(PersistentIStream & is, int version);
0085   //@}
0086
0087   /**
0088    * Standard Init function used to initialize the interfaces.
0089    */
0090   static void Init();
0091
0092 protected:
0093
0094
0095 protected:
0096
0097   /** @name Clone Methods. */
0098   //@{
0099   /**
0100    * Make a simple clone of this object.
0101    * @return a pointer to the new object.
0102    */
0103   virtual IBPtr clone() const;
0104
0105   /** Make a clone of this object, possibly modifying the cloned object
0106    * to make it sane.
0107    * @return a pointer to the new object.
0108    */
0109   virtual IBPtr fullclone() const;
0110   //@}
0111
0112 private:
0113
0114   /**
0115    * The grand parent in case reweighting should be done.
0116    */
0117   mutable tPPtr grandParent;
0118
0119   /**
0120    * The decaying particles sibling in case reweighting should be done.
0121    */
0122   mutable tPPtr sibling;
0123
0124 private:
0125
0126   /**
0127    * Describe a concrete class with persistent data.
0128    */
0129   static ClassDescription<V2PPDecayer> initV2PPDecayer;
0130
0131   /**
0132    * Private and non-existent assignment operator.
0133    */
0134   V2PPDecayer & operator=(const V2PPDecayer &) = delete;
0135
0136 };
0137
0138 }
0139
0140
0141 namespace ThePEG {
0142
0143 /** @cond TRAITSPECIALIZATIONS */
0144
0145 /** This template specialization informs ThePEG about the base classes
0146  *  of V2PPDecayer. */
0147 template <>
0148 struct BaseClassTrait<V2PPDecayer,1>: public ClassTraitsType {
0149   /** Typedef of the first base class of . */
0150   typedef FlatDecayer NthBase;
0151 };
0152
0153 /** This template specialization informs ThePEG about the name of the
0154  *  V2PPDecayer class and the shared object where it is
0155  *  defined. */
0156 template <>
0157 struct ClassTraits<V2PPDecayer>
0158   : public ClassTraitsBase<V2PPDecayer> {
0159   /** Return a platform-independent class name */
0160   static string className() { return "ThePEG::V2PPDecayer"; }
0161   /** Return the name of the shared library be loaded to get access to
0162    *  the V2PPDecayer class and every other class it uses
0163    *  (except the base class). */
0164   static string library() { return "V2PPDecayer.so"; }
0165 };
0166
0167 /** @endcond */
0168
0169 }
0170
0171 #endif /* THEPEG_V2PPDecayer_H */