Models/Transplanckian/METRP2to2.h

0001 // -*- C++ -*-
0002 //
0003 // METRP2to2.h is a part of Herwig - A multi-purpose Monte Carlo event generator
0004 // Copyright (C) 2009-2019 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_METRP2to2_H
0010 #define HERWIG_METRP2to2_H
0011 //
0012 // This is the declaration of the METRP2to2 class.
0013 //
0014 // The implementation of this process is based upon hep-ph/0112161 by G.F. Giudice, R. Rattazzi, J.D. Wells.
0015
0016 #include "Herwig/MatrixElement/HwMEBase.h"
0017 #include "ThePEG/Repository/UseRandom.h"
0018 #include "Herwig/Utilities/Interpolator.h"
0019
0020
0021 namespace Herwig {
0022 using namespace ThePEG;
0023
0024 /**
0025  * The METRP2to2 class implements the matrix elements for
0026  * Transplanckian \f$2\to2\f$ scattering process
0027  *
0028  * @see \ref METRP2to2Interfaces "The interfaces" defined for METRP2to2.
0029  */
0030 class METRP2to2: public HwMEBase {
0031
0032 public:
0033
0034   /**
0035    * The default constructor.
0036    */
0037   METRP2to2();
0038
0039   /** @name Virtual functions required by the MEBase class. */
0040   //@{
0041   /**
0042    * Return the order in \f$\alpha_S\f$ in which this matrix
0043    * element is given.
0044    */
0045   virtual unsigned int orderInAlphaS() const { return 0; }
0046
0047   /**
0048    * Return the order in \f$\alpha_{EW}\f$ in which this matrix
0049    * element is given.
0050    */
0051   virtual unsigned int orderInAlphaEW() const { return 0; }
0052
0053   /**
0054    * Return the scale associated with the last set phase space point.
0055    */
0056   virtual Energy2 scale() const;
0057
0058   /**
0059    * Add all possible diagrams with the add() function.
0060    */
0061   virtual void getDiagrams() const;
0062
0063   /**
0064    * Get diagram selector. With the information previously supplied with the
0065    * setKinematics method, a derived class may optionally
0066    * override this method to weight the given diagrams with their
0067    * (although certainly not physical) relative probabilities.
0068    * @param dv the diagrams to be weighted.
0069    * @return a Selector relating the given diagrams to their weights.
0070    */
0071   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
0072
0073   /**
0074    * Return a Selector with possible colour geometries for the selected
0075    * diagram weighted by their relative probabilities.
0076    * @param diag the diagram chosen.
0077    * @return the possible colour geometries weighted by their
0078    * relative probabilities.
0079    */
0080   virtual Selector<const ColourLines *>
0081   colourGeometries(tcDiagPtr diag) const;
0082
0083   /**
0084    * The matrix element for the kinematical configuration
0085    * previously provided by the last call to setKinematics(), suitably
0086    * scaled by sHat() to give a dimension-less number.
0087    * @return the matrix element scaled with sHat() to give a
0088    * dimensionless number.
0089    */
0090   virtual double me2() const;
0091   //@}
0092
0093
0094
0095 protected:
0096
0097   /** @name Standard Interfaced functions. */
0098   //@{
0099   /**
0100    * Initialize this object after the setup phase before saving an
0101    * EventGenerator to disk.
0102    * @throws InitException if object could not be initialized properly.
0103    */
0104   virtual void doinit();
0105
0106   /**
0107    * Rebind pointer to other Interfaced objects. Called in the setup phase
0108    * after all objects used in an EventGenerator has been cloned so that
0109    * the pointers will refer to the cloned objects afterwards.
0110    * @param trans a TranslationMap relating the original objects to
0111    * their respective clones.
0112    * @throws RebindException if no cloned object was found for a given
0113    * pointer.
0114    */
0115   virtual void rebind(const TranslationMap & trans);
0116
0117   /**
0118    * Return a vector of all pointers to Interfaced objects used in this
0119    * object.
0120    * @return a vector of pointers.
0121    */
0122   virtual IVector getReferences();
0123   //@}
0124
0125 public:
0126
0127   /** @name Functions used by the persistent I/O system. */
0128   //@{
0129   /**
0130    * Function used to write out object persistently.
0131    * @param os the persistent output stream written to.
0132    */
0133   void persistentOutput(PersistentOStream & os) const;
0134
0135   /**
0136    * Function used to read in object persistently.
0137    * @param is the persistent input stream read from.
0138    * @param version the version number of the object when written.
0139    */
0140   void persistentInput(PersistentIStream & is, int version);
0141   //@}
0142
0143   /**
0144    * The standard Init function used to initialize the interfaces.
0145    * Called exactly once for each class by the class description system
0146    * before the main function starts or
0147    * when this class is dynamically loaded.
0148    */
0149   static void Init();
0150
0151 protected:
0152
0153   /** @name Clone Methods. */
0154   //@{
0155   /**
0156    * Make a simple clone of this object.
0157    * @return a pointer to the new object.
0158    */
0159   virtual IBPtr clone() const;
0160
0161   /** Make a clone of this object, possibly modifying the cloned object
0162    * to make it sane.
0163    * @return a pointer to the new object.
0164    */
0165   virtual IBPtr fullclone() const;
0166   //@}
0167
0168 protected:
0169
0170   /** @name Helper functions for me2. */
0171   //@{
0172   /**
0173    * The function which calculates b_c according to hep-ph/0112161, eq.(18)
0174    */
0175   InvEnergy bccalc(Energy2 s) const;
0176
0177   /**
0178    * A_ny calculates part of the matrix element squared (divided by 16 * pi^2) according to hep-ph/0112161. eq.(19)
0179    */
0180   double A_ny(Energy2 s, Energy2 t) const;
0181
0182   /**
0183    * fpoint initializes the matrix of pre-calculated points for the functions F_n(y) (hep-ph/0112161, eq.(20)
0184    */
0185   double fpoint(double x) const;
0186
0187   /**
0188    * The asymptotic form of the F_n(y) functions, used for y>20, according to hep-ph/0112161, eq. (25)
0189    */
0190   double fnyasympt(double y) const;
0191   //@}
0192
0193   /**
0194    * Setup the interpolator
0195    */
0196   void setup_interpolator();
0197
0198 private:
0199
0200   /**
0201    * The assignment operator is private and must never be called.
0202    * In fact, it should not even be implemented.
0203    */
0204   METRP2to2 & operator=(const METRP2to2 &) = delete;
0205
0206 private:
0207
0208   /**
0209    * Interpolator
0210    */
0211   Interpolator<double, double>::Ptr _interpol;
0212
0213   /**
0214    *  Maximum number of quark flavours to include
0215    */
0216   unsigned int _maxflavour;
0217
0218   /**
0219    *  Number of Extra dimensions (>=2)
0220    */
0221   unsigned int _ndim;
0222
0223   /**
0224    *  The Extra-dimensional Planck mass
0225    */
0226   Energy _planckmass;
0227
0228
0229   /**
0230    *  Processes to include
0231    */
0232   unsigned int _process;
0233 };
0234
0235 }
0236
0237 #endif /* HERWIG_METRP2to2_H */