Matchbox/Phasespace/FlatInvertibleLabframePhasespace.h

0001 // -*- C++ -*-
0002 //
0003 // FlatInvertiblePhasespaceLabFrame.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_FlatInvertibleLabframePhasespace_H
0010 #define Herwig_FlatInvertibleLabframePhasespace_H
0011 //
0012 // This is the declaration of the FlatInvertibleLabframePhasespace class.
0013 //
0014
0015 #include "Herwig/MatrixElement/Matchbox/Phasespace/FlatInvertiblePhasespace.h"
0016
0017 namespace Herwig {
0018
0019 using namespace ThePEG;
0020
0021 /**
0022  * \ingroup Matchbox
0023  * \author Michael Rauch
0024  *
0025  * \brief FlatInvertibleLabframePhasespace implements flat, invertible phase space generation in the lab frame
0026  *
0027  */
0028 class FlatInvertibleLabframePhasespace: public FlatInvertiblePhasespace {
0029
0030 public:
0031
0032   /**
0033    * The default constructor.
0034    */
0035   FlatInvertibleLabframePhasespace();
0036
0037 public:
0038
0039   /**
0040    * Generate a phase space point and return its weight.
0041    */
0042   virtual double generateTwoToNKinematics(const double*,
0043                       vector<Lorentz5Momentum>& momenta);
0044
0045   /**
0046    * Return the number of random numbers required to produce a given
0047    * multiplicity final state.
0048    */
0049   virtual int nDimPhasespace(int nFinal) const {
0050     if ( nFinal == 1 )
0051       return 3;
0052     return 3*nFinal - 2;
0053   }
0054
0055 public:
0056
0057   /**
0058    * Return true, if this phasespace generator will generate incoming
0059    * partons itself.
0060    */
0061   virtual bool haveX1X2() const { return true; }
0062
0063   /**
0064    * Return true, if this phase space generator expects
0065    * the incoming partons in their center-of-mass system
0066    */
0067   virtual bool wantCMS() const { return false; }
0068
0069   /**
0070    * Invert the given phase space point to the random numbers which
0071    * would have generated it.
0072    */
0073   virtual double invertTwoToNKinematics(const vector<Lorentz5Momentum>& momenta,
0074                     double* r) const;
0075
0076 private:
0077
0078   /**
0079    * True if SHat should be generated flat in log(SHat/S),
0080    * false if SHat should be generated flat in SHat.
0081    */
0082   bool theLogSHat;
0083
0084 public:
0085
0086   /** @name Functions used by the persistent I/O system. */
0087   //@{
0088   /**
0089    * Function used to write out object persistently.
0090    * @param os the persistent output stream written to.
0091    */
0092   void persistentOutput(PersistentOStream & os) const;
0093
0094   /**
0095    * Function used to read in object persistently.
0096    * @param is the persistent input stream read from.
0097    * @param version the version number of the object when written.
0098    */
0099   void persistentInput(PersistentIStream & is, int version);
0100   //@}
0101
0102   /**
0103    * The standard Init function used to initialize the interfaces.
0104    * Called exactly once for each class by the class description system
0105    * before the main function starts or
0106    * when this class is dynamically loaded.
0107    */
0108   static void Init();
0109
0110 protected:
0111
0112   /** @name Clone Methods. */
0113   //@{
0114   /**
0115    * Make a simple clone of this object.
0116    * @return a pointer to the new object.
0117    */
0118   virtual IBPtr clone() const;
0119
0120   /** Make a clone of this object, possibly modifying the cloned object
0121    * to make it sane.
0122    * @return a pointer to the new object.
0123    */
0124   virtual IBPtr fullclone() const;
0125   //@}
0126
0127
0128 // If needed, insert declarations of virtual function defined in the
0129 // InterfacedBase class here (using ThePEG-interfaced-decl in Emacs).
0130
0131
0132 private:
0133
0134   /**
0135    * The assignment operator is private and must never be called.
0136    * In fact, it should not even be implemented.
0137    */
0138   FlatInvertibleLabframePhasespace & operator=(const FlatInvertibleLabframePhasespace &) = delete;
0139
0140 };
0141
0142 }
0143
0144 #endif /* Herwig_FlatInvertiblePhasespace_H */