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// -*- C++ -*-
//
// SMHiggsMassGenerator.h is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2011 The Herwig Collaboration
//
// Herwig++ is licenced under version 2 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;
/**
* The SMHiggsMassGenerator class implements the generation
* of the Higgs boson mass according to the prescription of hep-ph/9505211
*
* @see \ref SMHiggsMassGeneratorInterfaces "The interfaces"
* defined for SMHiggsMassGenerator.
*/
class SMHiggsMassGenerator: public GenericMassGenerator {
public:
/**
* The default constructor.
*/
SMHiggsMassGenerator() : _shape(1) {}
/**
* Weight for the factor for an off-shell mass
* @param q The off-shell mass
* @param shape The type of shape to use as for the BreitWignerShape interface
* @return The weight.
*/
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;
}
/**
* Return true if this mass generator can handle the given particle type.
* @param part The particle data pointer of the particle.
* @return True ig this class can handle the particle and false otherwise
*/
bool accept(const ParticleData & part) const;
/**
* output for the database
*/
virtual void dataBaseOutput(ofstream &,bool);
/** @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:
/**
* Weight for the factor for an off-shell mass
* @param q The off-shell mass
* @param shape The type of shape to use as for the BreitWignerShape interface
* @return The weight.
*/
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:
/** @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 and
* EventGenerator to disk.
* @throws InitException if object could not be initialized properly.
*/
virtual void doinit();
//@}
private:
/**
* The static object used to initialize the description of this class.
* Indicates that this is a concrete class with persistent data.
*/
static ClassDescription<SMHiggsMassGenerator> initSMHiggsMassGenerator;
/**
* The assignment operator is private and must never be called.
* In fact, it should not even be implemented.
*/
SMHiggsMassGenerator & operator=(const SMHiggsMassGenerator &);
private:
/**
* Option for the line-shape
*/
unsigned int _shape;
/**
* The width generator
*/
GenericWidthGeneratorPtr _hwidth;
};
}
#include "ThePEG/Utilities/ClassTraits.h"
namespace ThePEG {
/** @cond TRAITSPECIALIZATIONS */
/** This template specialization informs ThePEG about the
* base classes of SMHiggsMassGenerator. */
template <>
struct BaseClassTrait<Herwig::SMHiggsMassGenerator,1> {
/** Typedef of the first base class of SMHiggsMassGenerator. */
typedef Herwig::GenericMassGenerator NthBase;
};
/** This template specialization informs ThePEG about the name of
* the SMHiggsMassGenerator class and the shared object where it is defined. */
template <>
struct ClassTraits<Herwig::SMHiggsMassGenerator>
: public ClassTraitsBase<Herwig::SMHiggsMassGenerator> {
/** Return a platform-independent class name */
static string className() { return "Herwig::SMHiggsMassGenerator"; }
};
/** @endcond */
}
#endif /* HERWIG_SMHiggsMassGenerator_H */
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