SMHiggsMassGenerator.h

// -*- C++ -*-
//
// SMHiggsMassGenerator.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_SMHiggsMassGenerator_H
#define HERWIG_SMHiggsMassGenerator_H
//
// This is the declaration of the SMHiggsMassGenerator class.
//
 
#include "GenericMassGenerator.h"
#include "GenericWidthGenerator.h"
 
namespace Herwig {
 
using namespace ThePEG;
 
class SMHiggsMassGenerator: public GenericMassGenerator {
 
public:
 
  SMHiggsMassGenerator() : _shape(1) {}
 
  virtual double weight(Energy q, int shape) const {
    Energy2 q2    = sqr(q);
    Energy2 mass2 = sqr(nominalMass());
    Energy2 mwidth= nominalMass()*nominalWidth();
    return BreitWignerWeight(q,shape)*(sqr(mass2-q2)+sqr(mwidth))/mwidth;
  }
 
  bool accept(const ParticleData & part) const;
 
  virtual void dataBaseOutput(ofstream &,bool);
 
  void persistentOutput(PersistentOStream & os) const;
 
  void persistentInput(PersistentIStream & is, int version);
 
  static void Init();
 
protected:
 
  virtual InvEnergy2 BreitWignerWeight(Energy q,int shape) const {
    useMe();
    pair<Energy,Energy> widths = shape!=2 ? _hwidth->width(q,*particle()) :
      make_pair(nominalWidth(),nominalWidth());
    Energy2 q2 = sqr(q);
    Energy4 sq=sqr(q2-sqr(nominalMass()));
    Energy2 num = widths.first*q;
    double fact = 1.;
    if(_shape==1) fact *= pow<4,1>(nominalMass()/q);
    if( shape==3) num=GeV2;
    return num*fact/Constants::pi/(sq+sqr(widths.second*q)*fact);
  }
 
protected:
 
  virtual IBPtr clone() const { return new_ptr(*this); }
 
  virtual IBPtr fullclone() const { return new_ptr(*this); }
 
protected:
 
  virtual void doinit();
 
private:
 
  SMHiggsMassGenerator & operator=(const SMHiggsMassGenerator &) = delete;
 
private:
 
  unsigned int _shape;
 
  GenericWidthGeneratorPtr _hwidth;
 
};
 
}
 
#endif /* HERWIG_SMHiggsMassGenerator_H */