Herwig/PDT/SMHiggsMassGenerator.h

0001 // -*- C++ -*-
0002 //
0003 // SMHiggsMassGenerator.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_SMHiggsMassGenerator_H
0010 #define HERWIG_SMHiggsMassGenerator_H
0011 //
0012 // This is the declaration of the SMHiggsMassGenerator class.
0013 //
0014
0015 #include "GenericMassGenerator.h"
0016 #include "GenericWidthGenerator.h"
0017
0018 namespace Herwig {
0019
0020 using namespace ThePEG;
0021
0022 /**
0023  * The SMHiggsMassGenerator class implements the generation
0024  * of the Higgs boson mass according to the prescription of hep-ph/9505211
0025  *
0026  * @see \ref SMHiggsMassGeneratorInterfaces "The interfaces"
0027  * defined for SMHiggsMassGenerator.
0028  */
0029 class SMHiggsMassGenerator: public GenericMassGenerator {
0030
0031 public:
0032
0033   /**
0034    * The default constructor.
0035    */
0036   SMHiggsMassGenerator() : _shape(1) {}
0037
0038   /**
0039    * Weight for the factor for an off-shell mass
0040    * @param q The off-shell mass
0041    * @param shape The type of shape to use as for the BreitWignerShape interface
0042    * @return The weight.
0043    */
0044   virtual double weight(Energy q, int shape) const {
0045     Energy2 q2    = sqr(q);
0046     Energy2 mass2 = sqr(nominalMass());
0047     Energy2 mwidth= nominalMass()*nominalWidth();
0048     return BreitWignerWeight(q,shape)*(sqr(mass2-q2)+sqr(mwidth))/mwidth;
0049   }
0050
0051   /**
0052    * Return true if this mass generator can handle the given particle type.
0053    * @param part The particle data pointer of the particle.
0054    * @return True ig this class can handle the particle and false otherwise
0055    */
0056   bool accept(const ParticleData & part) const;
0057
0058   /**
0059    * output for the database
0060    */
0061   virtual void dataBaseOutput(ofstream &,bool);
0062
0063   /** @name Functions used by the persistent I/O system. */
0064   //@{
0065   /**
0066    * Function used to write out object persistently.
0067    * @param os the persistent output stream written to.
0068    */
0069   void persistentOutput(PersistentOStream & os) const;
0070
0071   /**
0072    * Function used to read in object persistently.
0073    * @param is the persistent input stream read from.
0074    * @param version the version number of the object when written.
0075    */
0076   void persistentInput(PersistentIStream & is, int version);
0077   //@}
0078
0079   /**
0080    * The standard Init function used to initialize the interfaces.
0081    * Called exactly once for each class by the class description system
0082    * before the main function starts or
0083    * when this class is dynamically loaded.
0084    */
0085   static void Init();
0086
0087 protected:
0088
0089   /**
0090    * Weight for the factor for an off-shell mass
0091    * @param q The off-shell mass
0092    * @param shape The type of shape to use as for the BreitWignerShape interface
0093    * @return The weight.
0094    */
0095   virtual InvEnergy2 BreitWignerWeight(Energy q,int shape) const {
0096     useMe();
0097     pair<Energy,Energy> widths = shape!=2 ? _hwidth->width(q,*particle()) :
0098       make_pair(nominalWidth(),nominalWidth());
0099     Energy2 q2 = sqr(q);
0100     Energy4 sq=sqr(q2-sqr(nominalMass()));
0101     Energy2 num = widths.first*q;
0102     double fact = 1.;
0103     if(_shape==1) fact *= pow<4,1>(nominalMass()/q);
0104     if( shape==3) num=GeV2;
0105     return num*fact/Constants::pi/(sq+sqr(widths.second*q)*fact);
0106   }
0107
0108 protected:
0109
0110   /** @name Clone Methods. */
0111   //@{
0112   /**
0113    * Make a simple clone of this object.
0114    * @return a pointer to the new object.
0115    */
0116   virtual IBPtr clone() const { return new_ptr(*this); }
0117
0118   /** Make a clone of this object, possibly modifying the cloned object
0119    * to make it sane.
0120    * @return a pointer to the new object.
0121    */
0122   virtual IBPtr fullclone() const { return new_ptr(*this); }
0123   //@}
0124
0125 protected:
0126
0127   /** @name Standard Interfaced functions. */
0128   //@{
0129   /**
0130    * Initialize this object after the setup phase before saving and
0131    * EventGenerator to disk.
0132    * @throws InitException if object could not be initialized properly.
0133    */
0134   virtual void doinit();
0135   //@}
0136
0137 private:
0138
0139   /**
0140    * The assignment operator is private and must never be called.
0141    * In fact, it should not even be implemented.
0142    */
0143   SMHiggsMassGenerator & operator=(const SMHiggsMassGenerator &) = delete;
0144
0145 private:
0146
0147   /**
0148    *  Option for the line-shape
0149    */
0150   unsigned int _shape;
0151
0152   /**
0153    *  The width generator
0154    */
0155   GenericWidthGeneratorPtr _hwidth;
0156
0157 };
0158
0159 }
0160
0161 #endif /* HERWIG_SMHiggsMassGenerator_H */