QTilde/Couplings/ShowerAlphaQED.h

0001 // -*- C++ -*-
0002 //
0003 // ShowerAlphaQED.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_ShowerAlphaQED_H
0010 #define HERWIG_ShowerAlphaQED_H
0011 //
0012 // This is the declaration of the ShowerAlphaQED class.
0013 //
0014
0015 #include "Herwig/Shower/ShowerAlpha.h"
0016
0017 namespace Herwig {
0018
0019 using namespace ThePEG;
0020
0021 /** \ingroup Shower
0022  *
0023  *  This concrete class provides the definition of the
0024  *  pure virtual function value(scale) for \f$\alpha_{\rm QED}\f$.
0025  *  N.B. as we always use \f$\alpha(0)\f$ for the radiation of photons
0026  *  this class is very simple.
0027  *
0028  *  @see ShowerAlpha
0029  *  @see ShowerAlphaQCD
0030  *
0031  * @see \ref ShowerAlphaQEDInterfaces "The interfaces"
0032  * defined for ShowerAlphaQED.
0033  */
0034 class ShowerAlphaQED: public ShowerAlpha {
0035
0036 public:
0037
0038   /** @name Standard constructors and destructors. */
0039   //@{
0040   /**
0041    * The default constructor.
0042    */
0043   ShowerAlphaQED() : ShowerAlpha(), _alpha(1./137.), couplingSource_(1)
0044   {}
0045   //@}
0046
0047 public:
0048
0049   /**
0050    * Methods to return the coupling.
0051    * The methods are equivalent to the QCD ones
0052    * and are necessary to make use of the virtuality of ShowerAlpha
0053    * at other places.
0054    */
0055   //@{
0056   /**
0057    * It returns the running coupling value evaluated at the input scale
0058    * multiplied by the scale factor scaleFactor().
0059    * @param scale The scale
0060    * @return The coupling
0061    */
0062   virtual double value(const Energy2 scale) const;
0063
0064   /**
0065    * It returns the overestimiate of the coupling
0066    * multiplied by the scale factor scaleFactor().
0067    */
0068   virtual double overestimateValue() const;
0069
0070   /**
0071    *  Return the ratio of the coupling at the scale to the overestimated value
0072    */
0073   virtual double ratio(const Energy2 scale,double factor=1.) const;
0074   //@}
0075
0076 public:
0077
0078   /** @name Functions used by the persistent I/O system. */
0079   //@{
0080   /**
0081    * Function used to write out object persistently.
0082    * @param os the persistent output stream written to.
0083    */
0084   void persistentOutput(PersistentOStream & os) const;
0085
0086   /**
0087    * Function used to read in object persistently.
0088    * @param is the persistent input stream read from.
0089    * @param version the version number of the object when written.
0090    */
0091   void persistentInput(PersistentIStream & is, int version);
0092   //@}
0093
0094   /**
0095    * The standard Init function used to initialize the interfaces.
0096    * Called exactly once for each class by the class description system
0097    * before the main function starts or
0098    * when this class is dynamically loaded.
0099    */
0100   static void Init();
0101
0102 protected:
0103
0104   /** @name Clone Methods. */
0105   //@{
0106   /**
0107    * Make a simple clone of this object.
0108    * @return a pointer to the new object.
0109    */
0110   inline virtual IBPtr clone() const {return new_ptr(*this);}
0111
0112   /** Make a clone of this object, possibly modifying the cloned object
0113    * to make it sane.
0114    * @return a pointer to the new object.
0115    */
0116   inline virtual IBPtr fullclone() const {return new_ptr(*this);}
0117   //@}
0118
0119 protected:
0120
0121   /**
0122    * Initialize this object after the setup phase before saving an
0123    * EventGenerator to disk.
0124    * @throws InitException if object could not be initialized properly.
0125    */
0126   virtual void doinit();
0127
0128 private:
0129
0130   /**
0131    * The static object used to initialize the description of this class.
0132    * Indicates that this is a concrete class with persistent data.
0133    */
0134   static ClassDescription<ShowerAlphaQED> initShowerAlphaQED;
0135
0136   /**
0137    * The assignment operator is private and must never be called.
0138    * In fact, it should not even be implemented.
0139    */
0140   ShowerAlphaQED & operator=(const ShowerAlphaQED &) = delete;
0141
0142 private:
0143
0144   /**
0145    *  The value of the coupling, as we are producing real photons
0146    *  this is always \f$\alpha(q^2=0)\f$.
0147    */
0148   double _alpha;
0149
0150   /**
0151    * Source of coupling value
0152    */
0153   unsigned int couplingSource_;
0154 };
0155
0156 }
0157
0158 #include "ThePEG/Utilities/ClassTraits.h"
0159
0160 namespace ThePEG {
0161
0162 /** @cond TRAITSPECIALIZATIONS */
0163
0164 /** This template specialization informs ThePEG about the
0165  *  base classes of ShowerAlphaQED. */
0166 template <>
0167 struct BaseClassTrait<Herwig::ShowerAlphaQED,1> {
0168   /** Typedef of the first base class of ShowerAlphaQED. */
0169   typedef Herwig::ShowerAlpha NthBase;
0170 };
0171
0172 /** This template specialization informs ThePEG about the name of
0173  *  the ShowerAlphaQED class and the shared object where it is defined. */
0174 template <>
0175 struct ClassTraits<Herwig::ShowerAlphaQED>
0176   : public ClassTraitsBase<Herwig::ShowerAlphaQED> {
0177   /** Return a platform-independent class name */
0178   static string className() { return "Herwig::ShowerAlphaQED"; }
0179   /**
0180    * The name of a file containing the dynamic library where the class
0181    * ShowerAlphaQED is implemented. It may also include several, space-separated,
0182    * libraries if the class ShowerAlphaQED depends on other classes (base classes
0183    * excepted). In this case the listed libraries will be dynamically
0184    * linked in the order they are specified.
0185    */
0186   static string library() { return "HwShower.so"; }
0187 };
0188
0189 /** @endcond */
0190
0191 }
0192
0193 #endif /* HERWIG_ShowerAlphaQED_H */