Herwig/PDT/TwoBodyAllOnCalculator.h

0001 // -*- C++ -*-
0002 //
0003 // TwoBodyAllOnCalculator.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_TwoBodyAllOnCalculator_H
0010 #define HERWIG_TwoBodyAllOnCalculator_H
0011 // This is the declaration of the TwoBodyAllOnCalculator class.
0012
0013 #include "WidthCalculatorBase.h"
0014 #include "TwoBodyAllOnCalculator.fh"
0015 #include "GenericWidthGenerator.h"
0016
0017 namespace Herwig {
0018 using namespace ThePEG;
0019
0020 /** \ingroup PDT
0021  *
0022  *  The <code>TwoBodyAllOnCalculator</code> class is a wrapped around the the
0023  *  simple two body decay matrix elements in the <code>GenericWidthGenerator</code>
0024  *  class and is designed to allow these matrix elements to be integrated
0025  *  if the external particles can be off-shell.
0026  *
0027  * @see TwoBodyAllOnCalculator
0028  *
0029  */
0030 class TwoBodyAllOnCalculator: public WidthCalculatorBase {
0031
0032 public:
0033
0034   /**
0035    * The GenericWidthGenerator class is a friend to allow easier access for the
0036    * integration of the two body partial widths.
0037    */
0038   friend class GenericWidthGenerator;
0039
0040 public:
0041
0042   /**
0043    * Constructor.
0044    * @param inwidth Pointer to the  GenericWidthGenerator class.
0045    * @param imode The mode in the GenericWidthGenerator class we are integrating
0046    * @param m1 The mass of the first particle.
0047    * @param m2 The mass of the second particle.
0048    */
0049   TwoBodyAllOnCalculator(tGenericWidthGeneratorPtr inwidth,int imode,
0050              Energy m1,Energy m2)
0051     : _mode(imode),_mass1(m1),_mass2(m2),_widthgen(inwidth)
0052   {}
0053
0054   /**
0055    * member to calculate the partial width.
0056    * @param scale The mass squared for the decaying particle.
0057    * @return The partial width.
0058    */
0059   Energy partialWidth(Energy2 scale) const;
0060
0061   /**
0062    * Get the mass of one of the decay products.  This must be
0063    * implemented in classes inheriting from this one.
0064    * @param imass The mass required.
0065    * @param mass The new value.
0066    * @return The mass required.
0067    */
0068   void resetMass(int imass,Energy mass) {
0069     if(imass==1)      _mass1=mass;
0070     else if(imass==2) _mass2=mass;
0071     else throw Exception() << "Unknown particle in "
0072                << "TwoBodyAllOnCalculator::resetMass()"
0073                << Exception::runerror;
0074   }
0075
0076   /**
0077    * Get the mass of one of the decay products.  This must be
0078    * implemented in classes inheriting from this one.
0079    * @param imass The mass required.
0080    * @return The mass required.
0081    */
0082   Energy getMass(const int imass) const {
0083     if(imass==1)      return _mass1;
0084     else if(imass==2) return _mass2;
0085     else throw Exception() << "Unknown particle in "
0086                << "TwoBodyAllOnCalculator::getMass()"
0087                << Exception::runerror;
0088   }
0089
0090   /**
0091    * Get the masses of all bar the one specified. Used to get the limits
0092    * for integration.
0093    * @param imass The particle not needed
0094    * @return The sum of the other masses.
0095    */
0096   Energy otherMass(const int imass) const {
0097     if(imass==1)      return _mass2;
0098     else if(imass==2) return _mass1;
0099     else throw Exception() << "Unknown particle in "
0100                << "TwoBodyAllOnCalculator::otherMass()"
0101                << Exception::runerror;
0102   }
0103
0104 private:
0105
0106   /**
0107    * Private and non-existent assignment operator.
0108    */
0109   TwoBodyAllOnCalculator & operator=(const TwoBodyAllOnCalculator &) = delete;
0110
0111 private:
0112
0113   /**
0114    * the mode
0115    */
0116   int _mode;
0117
0118   /**
0119    * Mass of the first particle.
0120    */
0121   Energy _mass1;
0122
0123   /**
0124    * Mass of the second particle.
0125    */
0126   Energy _mass2;
0127
0128   /**
0129    * the width generator
0130    */
0131   GenericWidthGeneratorPtr _widthgen;
0132
0133 };
0134
0135 }
0136
0137 #endif /* HERWIG_TwoBodyAllOnCalculator_H */