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 // -*- C++ -*-
 //
 // MEPP2Higgs.h is a part of Herwig - A multi-purpose Monte Carlo event generator
 // Copyright (C) 2002-2019 The Herwig Collaboration
 //
 // Herwig is licenced under version 3 of the GPL, see COPYING for details.
 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
 //
 #ifndef HERWIG_MEPP2Higgs_H
 #define HERWIG_MEPP2Higgs_H
 //
 // This is the declaration of the MEPP2Higgs class.
 //
 
 #include "Herwig/MatrixElement/HwMEBase.h"
 #include "ThePEG/Helicity/WaveFunction/ScalarWaveFunction.h"
 #include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
 #include "ThePEG/Helicity/WaveFunction/SpinorWaveFunction.h"
 #include "ThePEG/Helicity/WaveFunction/SpinorBarWaveFunction.h"
 #include "ThePEG/Helicity/Vertex/AbstractFFSVertex.h"
 #include "ThePEG/Helicity/Vertex/AbstractVVSVertex.h"
 #include "Herwig/PDT/GenericMassGenerator.h"
 #include "Herwig/MatrixElement/ProductionMatrixElement.h"
 #include "Herwig/Shower/ShowerAlpha.h"
 
 namespace Herwig {
 using namespace ThePEG;
 using namespace ThePEG::Helicity;
 
 /**
  * The MEPP2Higgs class implements the matrix element for the process
  * pp->Higgs with different Higgs shape prescriptions (see details in hep-ph/9505211)
  * and the NLL corrected Higgs width (see details in the FORTRAN HERWIG manual).
  *
  * @see \ref MEPP2HiggsInterfaces "The interfaces"
  * defined for MEPP2Higgs.
  */
 class MEPP2Higgs: public HwMEBase {
 
 public:
 
   /**
    * The default constructor.
    */
   MEPP2Higgs();
 
   /**
    * Return the matrix element for the kinematical configuation
    * previously provided by the last call to setKinematics(). Uses
    * me().
    */
   virtual CrossSection dSigHatDR() const;
 
   /**
    * Set the typed and momenta of the incoming and outgoing partons to
    * be used in subsequent calls to me() and colourGeometries()
    * according to the associated XComb object.
    */
   virtual void setKinematics() {
     HwMEBase::setKinematics();
     mh2_ = sHat();
   }
 
 public:
  
   /** @name Member functions for the generation of hard QCD radiation */
   //@{
   /**
    *  Has a POWHEG style correction
    */
   virtual POWHEGType hasPOWHEGCorrection() {return ISR;}
 
   /**
    *  Has an old fashioned ME correction
    */
   virtual bool hasMECorrection() {return true;}
 
   /**
    *  Initialize the ME correction
    */
   virtual void initializeMECorrection(RealEmissionProcessPtr, double &,
                       double & );
 
   /**
    *  Apply the hard matrix element correction to a given hard process or decay
    */
   virtual RealEmissionProcessPtr applyHardMatrixElementCorrection(RealEmissionProcessPtr);
 
   /**
    * Apply the soft matrix element correction
    * @param parent The initial particle in the current branching
    * @param progenitor The progenitor particle of the jet
    * @param fs Whether the emission is initial or final-state
    * @param highestpT The highest pT so far in the shower
    * @param ids ids of the particles produced in the branching
    * @param z The momentum fraction of the branching
    * @param scale the evolution scale of the branching
    * @param pT The transverse momentum of the branching
    * @return If true the emission should be vetoed
    */
   virtual bool softMatrixElementVeto(PPtr parent,
                      PPtr progenitor,
                      const bool & fs,
                      const Energy & highestpT,
                      const vector<tcPDPtr> & ids,
                      const double & z,
                      const Energy & scale,
                      const Energy & pT);
 
   /**
    *  Apply the POWHEG style correction
    */
   virtual RealEmissionProcessPtr generateHardest(RealEmissionProcessPtr,
                          ShowerInteraction);
   //@}
 
 public:
 
   /** @name Virtual functions required by the MEBase class. */
   //@{
   /**
    * Return the order in \f$\alpha_S\f$ in which this matrix
    * element is given.
    */
   virtual unsigned int orderInAlphaS() const;
 
   /**
    * Return the order in \f$\alpha_{EW}\f$ in which this matrix
    * element is given.
    */
   virtual unsigned int orderInAlphaEW() const;
 
   /**
    * The matrix element for the kinematical configuration
    * previously provided by the last call to setKinematics(), suitably
    * scaled by sHat() to give a dimension-less number.
    * @return the matrix element scaled with sHat() to give a
    * dimensionless number.
    */
   virtual double me2() const;
 
   /**
    * Generate internal degrees of freedom given nDim() uniform
    * random numbers in the interval \f$ ]0,1[ \f$. To help the phase space
    * generator, the dSigHatDR should be a smooth function of these
    * numbers, although this is not strictly necessary.
    * @param r a pointer to the first of nDim() consecutive random numbers.
    * @return true if the generation succeeded, otherwise false.
    */
   virtual bool generateKinematics(const double * r);
 
   /**
    * Return the scale associated with the last set phase space point.
    */
   virtual Energy2 scale() const;
 
   /**
    * The number of internal degrees of freedom used in the matrix
    * element.
    */
   virtual int nDim() const;
 
   /**
    * Add all possible diagrams with the add() function.
    */
   virtual void getDiagrams() const;
 
   /**
    * Get diagram selector. With the information previously supplied with the
    * setKinematics method, a derived class may optionally
    * override this method to weight the given diagrams with their
    * (although certainly not physical) relative probabilities.
    * @param dv the diagrams to be weighted.
    * @return a Selector relating the given diagrams to their weights.
    */
   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
 
   /**
    * Return a Selector with possible colour geometries for the selected
    * diagram weighted by their relative probabilities.
    * @param diag the diagram chosen.
    * @return the possible colour geometries weighted by their
    * relative probabilities.
    */
   virtual Selector<const ColourLines *> colourGeometries(tcDiagPtr diag) const;
 
   /**
    *  Construct the vertex of spin correlations.
    */
   virtual void constructVertex(tSubProPtr);
   //@}
 
 public:
 
   /** @name Functions used by the persistent I/O system. */
   //@{
   /**
    * Function used to write out object persistently.
    * @param os the persistent output stream written to.
    */
   void persistentOutput(PersistentOStream & os) const;
 
   /**
    * Function used to read in object persistently.
    * @param is the persistent input stream read from.
    * @param version the version number of the object when written.
    */
   void persistentInput(PersistentIStream & is, int version);
   //@}
 
   /**
    * The standard Init function used to initialize the interfaces.
    * Called exactly once for each class by the class description system
    * before the main function starts or
    * when this class is dynamically loaded.
    */
   static void Init();
 
 protected:
 
   /** @name Clone Methods. */
   //@{
   /**
    * Make a simple clone of this object.
    * @return a pointer to the new object.
    */
   virtual IBPtr clone() const { return new_ptr(*this); }
 
   /** Make a clone of this object, possibly modifying the cloned object
    * to make it sane.
    * @return a pointer to the new object.
    */
   virtual IBPtr fullclone() const { return new_ptr(*this); }
   //@}
 
 protected:
 
   /** @name Standard Interfaced functions. */
   //@{
   /**
    * Initialize this object after the setup phase before saving an
    * EventGenerator to disk.
    * @throws InitException if object could not be initialized properly.
    */
   virtual void doinit();
  
   /**
    * Finalize this object. Called in the run phase just after a
    * run has ended. Used eg. to write out statistics.
    */
   virtual void dofinish();
   //@}
 
 protected:
   
   /**
    *   Members to calculate the real emission matrix elements
    */
   //@{
   /**
    *  The leading-order matrix element for \f$gg\to H\f$
    */
   Energy4 loME() const;
 
   /**
    *  The matrix element for \f$gg\to H g\f$
    */
   Energy2 ggME(Energy2 s, Energy2 t, Energy2 u);
 
   /**
    *  The matrix element for \f$qg\to H q\f$
    */
   Energy2 qgME(Energy2 s, Energy2 t, Energy2 u);
 
   /**
    *  The matrix element for \f$qbarg\to H qbar\f$
    */
   Energy2 qbargME(Energy2 s, Energy2 t, Energy2 u);
   //@}
 
   /**
    *  Members to calculate the functions for the loop diagrams
    */
   //@{
   /**
    *  The \f$B(s)\f$ function of NBP339 (1990) 38-66
    * @param s The scale
    * @param mf2 The fermion mass squared.
    */
   Complex B(Energy2 s,Energy2 mf2) const;
 
   /**
    *  The \f$C(s)\f$ function of NBP339 (1990) 38-66
    * @param s The scale
    * @param mf2 The fermion mass squared.
    */
   complex<InvEnergy2> C(Energy2 s,Energy2 mf2) const;
 
   /**
    *  The \f$C(s)\f$ function of NBP339 (1990) 38-66
    * @param s The \f$s\f$ invariant
    * @param t The \f$t\f$ invariant
    * @param u The \f$u\f$ invariant
    * @param mf2 The fermion mass squared
    */
   complex<InvEnergy4> D(Energy2 s,Energy2 t, Energy2 u,Energy2 mf2) const;
 
   /**
    * The integral \f$\int\frac{dy}{y-y_0}\log(a-i\epsilon-b y(1-y))\f$
    * from NBP339 (1990) 38-66.
    * @param a  The parameter \f$a\f$.
    * @param b  The parameter \f$b\f$.
    * @param y0 The parameter \f$y_0\f$.
    */
   Complex dIntegral(Energy2 a, Energy2 b, double y0) const;
 
   /**
    *  The \f$M_{+++}\f$ matrix element of NBP339 (1990) 38-66.
    * @param s   The \f$s\f$ invariant
    * @param t   The \f$t\f$ invariant
    * @param u   The \f$u\f$ invariant
    * @param mf2 The fermion mass squared.
    * @param i Which of the stored values to use for \f$D(u,t)\f$.
    * @param j Which of the stored values to use for \f$D(u,s)\f$.
    * @param k Which of the stored values to use for \f$D(s,t)\f$.
    * @param i1 Which of the stored values to use for \f$C_1(s)\f$.
    * @param j1 Which of the stored values to use for \f$C_1(t)\f$.
    * @param k1 Which of the stored values to use for \f$C_1(u)\f$.
    */
   complex<Energy> me1(Energy2 s,Energy2 t,Energy2 u, Energy2 mf2,
                  unsigned int i,unsigned int j, unsigned int k,
                  unsigned int i1,unsigned int j1, unsigned int k1) const;
 
   /**
    *  The \f$M_{++-}\f$ matrix element of NBP339 (1990) 38-66.
    * @param s   The \f$s\f$ invariant
    * @param t   The \f$t\f$ invariant
    * @param u   The \f$u\f$ invariant
    * @param mf2 The fermion mass squared.
    */
   complex<Energy> me2(Energy2 s,Energy2 t,Energy2 u, Energy2 mf2) const;
 
   /**
    *  The \f$F(x)\f$ function for the leading-order result
    */
   Complex F(double x) const;
   //@}
 
   /**
    *  Method to extract the PDF weight for quark/antiquark
    * initiated processes and select the quark flavour
    */  
   tPDPtr quarkFlavour(tcPDFPtr pdf, Energy2 scale, double x, tcBeamPtr beam, 
               double & pdfweight, bool anti);
 
   /**
    * Return the momenta and type of hard matrix element correction
    * @param gluons The original incoming particles.
    * @param beams The BeamParticleData objects
    * @param higgs The original outgoing higgs
    * @param iemit Whether the first (0) or second (1) particle emitted
    * the radiation
    * @param itype The type of radiated particle (0 is gluon, 1 is quark 
    *              and 2 is antiquark)
    * @param pnew The momenta of the new particles
    * @param xnew The new values of the momentuym fractions
    * @param out The ParticleData object for the outgoing parton
    * @return Whether or not the matrix element correction needs to be applied
    */
   bool applyHard(ParticleVector gluons,
          vector<tcBeamPtr> beams,
          PPtr higgs,unsigned int & iemit,
          unsigned int & itype,vector<Lorentz5Momentum> & pnew,
          pair<double,double> & xnew,
          tPDPtr & out);
 
   /**
    *  generates the hardest emission (yj,p)
    * @param pnew The momenta of the new particles
    * @param emissiontype The type of emission, as for getResult
    * @return Whether not an emission was generated
    */
   bool getEvent(vector<Lorentz5Momentum> & pnew,int & emissiontype);
 
   /**
    * Returns the matrix element for a given type of process,
    * rapidity of the jet \f$y_j\f$ and transverse momentum \f$p_T\f$
    * @param emis_type the type of emission,
    * (0 is \f$gg\to h^0g\f$, 1 is \f$qg\to h^0q\f$ and 2 is \f$g\bar{q}\to h^0\bar{q}\f$)
    * @param pt The transverse momentum of the jet
    * @param yj The rapidity of the jet
    * @param outParton the outgoing parton
    */
   double getResult(int emis_type, Energy pt, double yj,tcPDPtr & outParton);
 
 private:
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   MEPP2Higgs & operator=(const MEPP2Higgs &) = delete;
   //@}
 
   /**
    *  Members to return the matrix elements for the different subprocesses
    */
   //@{
   /**
    * Calculates the matrix element for the process g,g->h (via quark loops)
    * @param g1 a vector of wave functions of the first incoming gluon
    * @param g2 a vector of wave functions of the second incoming gluon
    * @param calc Whether or not to calculate the matrix element for spin correlations
    * @return the amlitude value.
    */
   double ggME(vector<VectorWaveFunction> g1,
               vector<VectorWaveFunction> g2,
               ScalarWaveFunction &, 
               bool calc) const;
 
   /**
    * Calculates the matrix element for the process q,qbar->h
    * @param fin a vector of quark spinors
    * @param ain a vector of anti-quark spinors
    * @param calc Whether or not to calculate the matrix element for spin correlations
    * @return the amlitude value.
    */
   double qqME(vector<SpinorWaveFunction> & fin, 
               vector<SpinorBarWaveFunction> & ain, 
               ScalarWaveFunction &, 
               bool calc) const;
   //@}
 
 private:
 
   /**
    * Selects a dynamic (sHat) or fixed factorization scale
    */
   unsigned int scaleopt_;
 
   /**
    * The value associated to the fixed factorization scale option
    */
   Energy mu_F_;
 
   /**
    * Defines the Higgs resonance shape
    */
   unsigned int shapeOption_;
 
   /**
    * The processes to be included (GG->H and/or qq->H)
    */
   unsigned int processOption_;
 
   /**
    * Minimum flavour of incoming quarks
    */
   int minFlavour_;
 
   /**
    * Maximum flavour of incoming quarks
    */
   int maxFlavour_;
 
   /**
    * Matrix element for spin correlations
    */
   ProductionMatrixElement me_;
 
   /**
    * Pointer to the H-> 2 gluon vertex (used in gg->H)
    */
   AbstractVVSVertexPtr HGGVertex_;
 
   /**
    * Pointer to the fermion-fermion Higgs vertex (used in qq->H)
    */
   AbstractFFSVertexPtr HFFVertex_;
 
   /**
    *  The mass generator for the Higgs
    */
   GenericMassGeneratorPtr hmass_;
 
   /**
    *  On-shell mass for the higgs
    */
   Energy mh_;
 
   /**
    *  On-shell width for the higgs
    */
   Energy wh_;
 
   /**
    *  Stuff for the ME correction
    */
   //@{
   /**
    *  Parameters for the evaluation of the loops for the 
    *  matrix elements
    */
   //@{
   /**
    *  Minimum flavour of quarks to include in the loops
    */
   unsigned int minLoop_;
 
   /**
    *  Maximum flavour of quarks to include in the loops
    */
   unsigned int maxLoop_;
 
   /**
    *  Option for treatment of the fermion loops
    */
   unsigned int massOption_;
 
   /**
    *  Option for dynamic scale choice in alpha_S (0=mT,>0=pT)
    */
   unsigned int mu_R_opt_;
 
   /**
    *  Option for dynamic scale choice in PDFs    (0=mT,>0=pT)
    */
   unsigned int mu_F_opt_;
   //@}
 
   //@}
 
   /**
    *  Small complex number to regularize some integrals
    */
   static const complex<Energy2> epsi_;
 
   /**
    *  Storage of the loop functions
    */
   //@{
   /**
    *  B functions
    */
   mutable Complex bi_[5];
 
   /**
    *  C functions
    */
   mutable complex<InvEnergy2> ci_[8];
 
   /**
    *  D functions
    */
   mutable complex<InvEnergy4> di_[4];
   //@}
 
   /**
    *  Pointer to the object calculating the strong coupling
    */
   ShowerAlphaPtr alpha_;
 
   /**
    *  Mass squared of Higgs
    */  
   Energy2 mh2_;
 
   /**
    *  Relative weight of the \f$qg\f$ to the \f$gg\f$  channel
    */
   double channelwgtA_;
 
   /**
    *  Relative weight for the \f$\bar{q}g\f$ to the \f$gg\f$  channel
    */
   double channelwgtB_;
 
   /**
    *  Weights for the channels as a vector
    */
   vector<double> channelWeights_;
 
   /**
    *  Power for the \f$\frac{{\rm d}\hat{s}}{\hat{s}^n}\f$ importance sampling
    *  of the \f$gg\f$ component 
    */
   double ggPow_;
 
   /**
    *  Power for the \f$\frac{{\rm d}\hat{s}}{\hat{s}^n}\f$ importance sampling
    *  of the \f$qg\f$ and \f$\bar{q}g\f$ components 
    */
   double qgPow_;
 
   /**
    *  The enhancement factor for initial-state radiation
    */
   double enhance_;
   
   /**
    *  Number of weights greater than 1
    */
   unsigned int nover_;
 
   /**
    *  Number of attempts
    */
   unsigned int ntry_;
 
   /**
    *  Number which suceed
    */
   unsigned int ngen_;
 
   /**
    *  Maximum weight
    */
   double maxwgt_;
   //@}
 
   /**
    *  Constants for the sampling. The distribution is assumed to have the
    *  form \f$\frac{c}{{\rm GeV}}\times\left(\frac{{\rm GeV}}{p_T}\right)^n\f$ 
    */
   //@{
   /**
    * The power, \f$n\f$, for the sampling
    */
   double power_;
 
   /**
    *  The prefactor, \f$c\f$ for the \f$gg\f$ channel
    */
   double pregg_;
 
   /**
    *  The prefactor, \f$c\f$ for the \f$qg\f$ channel
    */
   double preqg_;
 
   /**
    *  The prefactor, \f$c\f$ for the \f$g\bar{q}\f$ channel
    */
   double pregqbar_;
 
   /**
    *  The prefactors as a vector for easy use
    */
   vector<double> prefactor_;
   //@}
 
   /**
    *  The transverse momentum of the jet
    */
   Energy minpT_;
 
   /**
    *  Properties of the incoming particles
    */
   //@{
   /**
    *  Pointers to the BeamParticleData objects
    */
   vector<tcBeamPtr> beams_;
   
   /**
    *  Pointers to the ParticleDataObjects for the partons
    */
   vector<tcPDPtr> partons_;
   //@}
 
   /**
    *  Properties of the boson and jets
    */
   //@{
   /**
    *  The rapidity of the Higgs boson
    */
   double yh_;
 
   /**
    *  The mass of the Higgs boson
    */
   Energy mass_;
 
   /**
    *  the rapidity of the jet
    */
   double yj_;
 
   /**
    *  The transverse momentum of the jet
    */
   Energy pt_;
 
   /**
    *  The outgoing parton
    */
   tcPDPtr out_;
   //@}
 
   /**
    *  Whether of not to construct the vertex for spin correlations
    */
   bool spinCorrelations_;
 
 };
 
 }
 
 #endif /* HERWIG_MEPP2Higgs_H */

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