Herwig/Decay/Hw64Decayer.h

0001 // -*- C++ -*-
0002 //
0003 // Hw64Decayer.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_Hw64Decayer_H
0010 #define HERWIG_Hw64Decayer_H
0011 //
0012 // This is the declaration of the Hw64Decayer class.
0013 //
0014 #include <ThePEG/Config/ThePEG.h>
0015 #include <HwDecayerBase.h>
0016 #include <ThePEG/Interface/Interfaced.h>
0017 #include <ThePEG/PDT/DecayMode.h>
0018 #include <ThePEG/Repository/Strategy.fh>
0019 #include <fstream>
0020
0021 namespace Herwig {
0022
0023 using namespace ThePEG;
0024
0025 /** \ingroup Decay
0026  *
0027  * <code>Hw64Decayer</code> is a class that defines all the general routines
0028  * used in HERWIG++ to imitate the HERWIG 6.4 decays. The goal is to have an exact
0029  * copy of HERWIG 6.4 decay routines. This will allow for easy 'callibration'
0030  * of the new C++ code with the old Fortran code.
0031  *
0032  *  This class handles the non-partonic decays. In general it is used for
0033  *  exclusive meson and baryon decays. Three different matrix elements are supported
0034  *
0035  *  - MECode=0 flat-phase space.
0036  *  - MECode=100 free V-A matrix element
0037  *  - MECode=101 bound V-A matrix element
0038  *
0039  * @see HeavyDecayer
0040  * @see QuarkoniumDecayer
0041  * @see Decayer
0042  *
0043  */
0044 class Hw64Decayer: public HwDecayerBase {
0045
0046 public:
0047
0048   /**
0049    * Default constructor
0050    */
0051   Hw64Decayer() : MECode(0),_masstry(50) {}
0052
0053   /**
0054    * return true if this decayer can perfom the decay specified by the
0055    * given decay mode.
0056    */
0057   virtual bool accept(tcPDPtr parent, const tPDVector & children) const;
0058
0059   /**
0060    * for a given decay mode and a given particle instance, perform the
0061    * decay and return the decay products.
0062    */
0063   virtual ParticleVector decay(const Particle & parent,
0064                    const tPDVector & children) const;
0065
0066   /**
0067    * Output the setup information for the particle database
0068    * @param os The stream to output the information to
0069    * @param header Whether or not to output the information for MySQL
0070    */
0071   virtual void dataBaseOutput(ofstream & os,bool header) const;
0072
0073 public:
0074
0075   /**
0076    * Standard Init function used to initialize the interface.
0077    */
0078   static void Init();
0079
0080   /** @name Functions used by the persistent I/O system. */
0081   //@{
0082   /**
0083    * Function used to write out object persistently.
0084    * @param os the persistent output stream written to.
0085    */
0086   void persistentOutput(PersistentOStream & os) const;
0087
0088   /**
0089    * Function used to read in object persistently.
0090    * @param is the persistent input stream read from.
0091    * @param version the version number of the object when written.
0092    */
0093   void persistentInput(PersistentIStream & is, int version);
0094   //@}
0095
0096 protected:
0097
0098   /** @name Clone Methods. */
0099   //@{
0100   /**
0101    * Make a simple clone of this object.
0102    * @return a pointer to the new object.
0103    */
0104   virtual IBPtr clone() const {return new_ptr(*this);}
0105
0106   /** Make a clone of this object, possibly modifying the cloned object
0107    * to make it sane.
0108    * @return a pointer to the new object.
0109    */
0110   virtual IBPtr fullclone() const {return new_ptr(*this);}
0111   //@}
0112
0113 private:
0114
0115   /**
0116    * Weighting of phase space for V-A matrix elements
0117    */
0118   static double VAWt(Energy2 t0, Energy2 t1, Energy2 t2, InvEnergy4 t3);
0119
0120   /**
0121    * Take an array of momenta and set the momentum member of the particles.
0122    * @param moms The input momenta to be assigned to the particles.
0123    * @param particles The particles whose momenta is to be set.
0124    * @param out The particles outputted with their momenta set.
0125    */
0126   void setParticleMomentum(ParticleVector & out, const cPDVector & particles,
0127                const vector<Lorentz5Momentum> & moms) const {
0128     unsigned int numProds = particles.size();
0129     for(unsigned int ix=0;ix<numProds;++ix)
0130       out.push_back(particles[ix]->produceParticle(moms[ix]));
0131   }
0132
0133 private:
0134
0135   /**
0136    *  Private and non-existent assignment operator.
0137    */
0138   const Hw64Decayer & operator=(const Hw64Decayer &) = delete;
0139
0140 private:
0141
0142   /**
0143    *  The code for the matrix element being used.
0144    */
0145   int MECode;
0146
0147   /**
0148    *  Maximum number of attempts to generate the off-shell masses
0149    */
0150   unsigned int _masstry;
0151 };
0152
0153 }
0154
0155 #endif /* HERWIG_Hw64Decayer_H */