EIC code displayed by LXR master/​include/​Herwig/​Decay/​VectorMeson/​OniumToOniumPiPiDecayer.h	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

File indexing completed on 2026-08-06 09:24:03

 // -*- C++ -*-
 //
 // OniumToOniumPiPiDecayer.h is a part of Herwig - A multi-purpose Monte Carlo event generator
 // Copyright (C) 2002-2019 The Herwig Collaboration
 //
 // Herwig is licenced under version 3 of the GPL, see COPYING for details.
 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
 //
 #ifndef HERWIG_OniumToOniumPiPiDecayer_H
 #define HERWIG_OniumToOniumPiPiDecayer_H
 //
 // This is the declaration of the OniumToOniumPiPiDecayer class.
 //
 
 #include "Herwig/Decay/DecayIntegrator.h"
 #include "ThePEG/Helicity/LorentzPolarizationVector.h"
 
 namespace Herwig {
 
 using namespace ThePEG;
 
 /** \ingroup Decay
  *  The OniumToOniumPiPiDecayer class uses the matrix element of 
  *  Brown and Cahn PRL35, 1 (1975) for the decay of onium resonaces to
  *  lighter states and pion pairs. The matrix element is given by
  * \f[\mathcal{M} = \epsilon'\cdot\epsilon\left[
  *    \mathcal{A}\left(q^2-2m^2_\pi\right)+\mathcal{B}E_1E_2\right]
  *    +\mathcal{C}\left((\epsilon'\cdot q_1)(\epsilon\cdot q_2)+
  *                     (\epsilon'\cdot q_2)(\epsilon\cdot q_1)\right),\f]
  * where \f$\epsilon'\f$ is the polarization vector of the decaying onium resonance,
  *       \f$\epsilon\f$  is the polarization vector of the outgoing onium resonance,
  *    \f$\mathcal{A}\f$, \f$\mathcal{B}\f$ and \f$\mathcal{C}\f$ are complex couplings,
  *    \f$m_\pi\f$ is the pion mass, \f$E_{1,2}\f$ are the pion energies, \f$q_{1,2}\f$ 
  *    are the pion momenta and \f$q\f$ is the momentum of the \f$\pi\pi\f$ system.
  * 
  * The results of hep-ex/9909038 are used for \f$\psi'\to J/\psi\f$ and arXiv:0706.2317
  * for \f$\Upsilon(3S)\f$ and \f$\Upsilon(2S)\f$ decays.
  * The remaining parameters are choosen
  * to approximately reproduce the distributions from hep-ex/0604031 and hep-ex/0508023.
  *
  * @see \ref OniumToOniumPiPiDecayerInterfaces "The interfaces"
  * defined for OniumToOniumPiPiDecayer.
  */
 class OniumToOniumPiPiDecayer: public DecayIntegrator {
 
 public:
 
   /**
    * The default constructor.
    */
   OniumToOniumPiPiDecayer() {
     // don't generate the intermediates in the phase-space
     generateIntermediates(false);
   }
 
   /**
    * Which of the possible decays is required
    * @param cc Is this mode the charge conjugate
    * @param parent The decaying particle
    * @param children The decay products
    */
   virtual int modeNumber(bool & cc, tcPDPtr parent, 
              const tPDVector & children) const;
 
   /**
    * Return the matrix element squared for a given mode and phase-space channel.
    * @param ichan The channel we are calculating the matrix element for. 
    * @param part The decaying Particle.
    * @param outgoing The particles produced in the decay
    * @param momenta  The momenta of the particles produced in the decay
    * @param meopt Option for the calculation of the matrix element
    * @return The matrix element squared for the phase-space configuration.
    */
   double me2(const int ichan,const Particle & part,
          const tPDVector & outgoing,
          const vector<Lorentz5Momentum> & momenta,
          MEOption meopt) const;
 
   /**
    *   Construct the SpinInfos for the particles produced in the decay
    */
   virtual void constructSpinInfo(const Particle & part,
                  ParticleVector outgoing) const;
 
   /**
    * Method to return an object to calculate the 3 body partial width.
    * @param dm The DecayMode
    * @return A pointer to a WidthCalculatorBase object capable of calculating the width
    */
   virtual WidthCalculatorBasePtr threeBodyMEIntegrator(const DecayMode & dm) const;
 
   /**
    * The matrix element to be integrated for the three-body decays as a function
    * of the invariant masses of pairs of the outgoing particles.
    * @param imode The mode for which the matrix element is needed.
    * @param q2 The scale, \e i.e. the mass squared of the decaying particle.
    * @param s3 The invariant mass squared of particles 1 and 2, \f$s_3=m^2_{12}\f$.
    * @param s2 The invariant mass squared of particles 1 and 3, \f$s_2=m^2_{13}\f$.
    * @param s1 The invariant mass squared of particles 2 and 3, \f$s_1=m^2_{23}\f$.
    * @param m1 The mass of the first  outgoing particle.
    * @param m2 The mass of the second outgoing particle.
    * @param m3 The mass of the third  outgoing particle.
    * @return The matrix element
    */
   virtual double threeBodyMatrixElement(const int imode, const Energy2 q2,
                     const  Energy2 s3, const Energy2 s2, const 
                     Energy2 s1, const Energy m1,
                     const Energy m2, const Energy m3) const;
 
   /**
    * Output the setup information for the particle database
    * @param os The stream to output the information to
    * @param header Whether or not to output the information for MySQL
    */
   virtual void dataBaseOutput(ofstream & os,bool header) const;
 
 public:
 
   /** @name Functions used by the persistent I/O system. */
   //@{
   /**
    * Function used to write out object persistently.
    * @param os the persistent output stream written to.
    */
   void persistentOutput(PersistentOStream & os) const;
 
   /**
    * Function used to read in object persistently.
    * @param is the persistent input stream read from.
    * @param version the version number of the object when written.
    */
   void persistentInput(PersistentIStream & is, int version);
   //@}
 
   /**
    * The standard Init function used to initialize the interfaces.
    * Called exactly once for each class by the class description system
    * before the main function starts or
    * when this class is dynamically loaded.
    */
   static void Init();
 
 protected:
 
   /** @name Clone Methods. */
   //@{
   /**
    * Make a simple clone of this object.
    * @return a pointer to the new object.
    */
   virtual IBPtr clone() const {return new_ptr(*this);}
 
   /** Make a clone of this object, possibly modifying the cloned object
    * to make it sane.
    * @return a pointer to the new object.
    */
   virtual IBPtr fullclone() const {return new_ptr(*this);}
   //@}
 
 protected:
 
   /** @name Standard Interfaced functions. */
   //@{
   /**
    * Initialize this object after the setup phase before saving an
    * EventGenerator to disk.
    * @throws InitException if object could not be initialized properly.
    */
   virtual void doinit();
 
   /**
    * Initialize this object to the begining of the run phase.
    */
   virtual void doinitrun();
   //@}
 
 private:
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   OniumToOniumPiPiDecayer & operator=(const OniumToOniumPiPiDecayer &) = delete;
 
 public:
 
   /**
    *   Set the parameters for a decay mode
    */
   string setUpDecayMode(string arg);
 
 private:
 
   /**
    * the PDG codes for the incoming onium resonace
    */
   vector<long> incoming_;
 
   /**
    * the PDG codes for the outgoing onium resonance
    */
   vector<long> outgoing_;
 
   /**
    * the maximum weight for the integration
    */
   vector<double> maxWeight_;
 
   /**
    *  The couplings for the decays
    */
   //@{
   /**
    *  Overall normalisation
    */
   vector<double> coupling_;
 
   /**
    *  The complex \f$A\f$ coupling
    */
   vector<complex<InvEnergy2> > cA_;
 
   /**
    *  The complex \f$B\f$ coupling
    */
   vector<complex<InvEnergy2> > cB_;
 
   /**
    *  The complex \f$C\f$ coupling
    */
   vector<complex<InvEnergy2> > cC_;
   //@}
 
   /**
    *  Spin density matrix
    */
   mutable RhoDMatrix rho_;
 
   /**
    *  Polarization vectors for the incomng and outgoing onium resonances
    */
   mutable vector<Helicity::LorentzPolarizationVector> vectors_[2];
 
 };
 
 }
 
 #endif /* HERWIG_OniumToOniumPiPiDecayer_H */

This page was automatically generated by the 2.3.7 LXR engine. The LXR team