GluonMassGenerator.h

// -*- C++ -*-
//
// GluonMassGenerator.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_GluonMassGenerator_H
#define Herwig_GluonMassGenerator_H
//
// This is the declaration of the GluonMassGenerator class.
//
 
#include "ThePEG/Handlers/HandlerBase.h"
#include "ThePEG/EventRecord/Particle.h"
 
namespace Herwig {
 
using namespace ThePEG;
 
class GluonMassGenerator: public HandlerBase {
 
public:
 
  virtual Energy generate(Energy, Energy) const {
    return generate();
  }
 
  virtual Energy generate(Energy) const {
    return generate();
  }                             
 
  virtual Energy generate() const {
    return getParticleData(ThePEG::ParticleID::g)->constituentMass();
  }
 
  list<Energy> generateMany(size_t n, Energy QMax) const {
    list<Energy> res;
    Energy m0, mu, md, ms, mg, summg;
 
    mu=getParticleData(ThePEG::ParticleID::u)->constituentMass();
    md=getParticleData(ThePEG::ParticleID::d)->constituentMass();
    ms=getParticleData(ThePEG::ParticleID::s)->constituentMass();
 
    m0=md;
    if(mu<m0){m0=mu;}
    if(ms<m0){m0=ms;}
 
    if( QMax<2.0*m0*n ){
      throw Exception() << "cannot reshuffle to constituent mass shells" << Exception::eventerror;
    }
 
    bool repeat=true;
 
    while( repeat ){
      repeat=false;
      summg = 0.0*GeV;
      res.clear();
      for( size_t k = 0; k < n; ++k ){ 
        mg = generate();
        res.push_back(mg);
        summg += mg;
        if( summg > QMax - 2.0*m0*(n-k-1) ){
          repeat=true;
          break;
        }
      }
    }
 
    return res;
    
  }
 
public:
 
  void persistentOutput(PersistentOStream & os) const;
 
  void persistentInput(PersistentIStream & is, int version);
 
  static void Init();
 
protected:
 
  virtual IBPtr clone() const;
 
  virtual IBPtr fullclone() const;
 
private:
 
  GluonMassGenerator & operator=(const GluonMassGenerator &) = delete;
 
};
 
}
 
#endif /* Herwig_GluonMassGenerator_H */