SplittingFunction.h

// -*- C++ -*-
//
// SplittingFunction.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_SplittingFunction_H
#define HERWIG_SplittingFunction_H
//
// This is the declaration of the SplittingFunction class.
//
 
#include "ThePEG/Interface/Interfaced.h"
#include "Herwig/Shower/QTilde/ShowerConfig.h"
#include "ThePEG/EventRecord/RhoDMatrix.h"
#include "Herwig/Decay/DecayMatrixElement.h"
#include "Herwig/Shower/QTilde/Kinematics/ShowerKinematics.fh"
#include "ThePEG/EventRecord/ColourLine.h"
#include "ThePEG/PDT/ParticleData.h"
#include "SplittingFunction.fh"
 
namespace Herwig {
 
using namespace ThePEG;
 
  enum ColourStructure {Undefined=0,
                        TripletTripletOctet  = 1,OctetOctetOctet    =2,
                        OctetTripletTriplet  = 3,TripletOctetTriplet=4,
                        SextetSextetOctet    = 5,
                        ChargedChargedNeutral=-1,ChargedNeutralCharged=-2,
                        NeutralChargedCharged=-3,EW=-4};
 
class SplittingFunction: public Interfaced {
 
public:
 
  SplittingFunction()
    : Interfaced(), _interactionType(ShowerInteraction::UNDEFINED),
      _colourStructure(Undefined), _colourFactor(-1.),
      angularOrdered_(true), scaleChoice_(2), strictAO_(true) {}
 
public:
 
  ShowerInteraction interactionType() const {return _interactionType;}
 
  ColourStructure colourStructure() const {return _colourStructure;}
 
  double colourFactor(const IdList &ids) const {
    if(_colourStructure>0)
      return _colourFactor;
    else if(_colourStructure<0) {
      if(_colourStructure==ChargedChargedNeutral ||
         _colourStructure==ChargedNeutralCharged) {
        return sqr(double(ids[0]->iCharge())/3.);
      }
      else if(_colourStructure==NeutralChargedCharged) {
        double fact = sqr(double(ids[1]->iCharge())/3.);
        if(ids[1]->coloured())
          fact *= abs(double(ids[1]->iColour()));
        return fact;
      }
      else if(_colourStructure==EW) {
        return 1.;
      }
      else {
        assert(false);
        return 0.;
      }
    }
    else {
      assert(false);
      return 0.;
    }
  }
 
  virtual bool accept(const IdList & ids) const = 0;
 
  virtual bool checkColours(const IdList & ids) const;
 
  virtual double P(const double z, const Energy2 t, const IdList & ids,
                   const bool mass, const RhoDMatrix & rho) const = 0;
 
  virtual double overestimateP(const double z, const IdList & ids) const = 0; 
 
  virtual double ratioP(const double z, const Energy2 t, const IdList & ids,
                        const bool mass, const RhoDMatrix & rho) const = 0;
 
  virtual double integOverP(const double z, const IdList & ids, 
                            unsigned int PDFfactor=0) const = 0; 
 
  virtual double invIntegOverP(const double r, const IdList & ids, 
                               unsigned int PDFfactor=0) const = 0;
 
  virtual void colourConnection(tShowerParticlePtr parent,
                                tShowerParticlePtr first,
                                tShowerParticlePtr second,
                                ShowerPartnerType partnerType, 
                                const bool back) const;
 
  virtual vector<pair<int,Complex> > 
  generatePhiForward(const double z, const Energy2 t, const IdList & ids,
                     const RhoDMatrix &) = 0;
 
  virtual vector<pair<int,Complex> > 
  generatePhiBackward(const double z, const Energy2 t, const IdList & ids,
                      const RhoDMatrix &) = 0;
 
  virtual DecayMEPtr matrixElement(const double z, const Energy2 t, 
                                   const IdList & ids, const double phi,
                                   bool timeLike) = 0;
 
  bool angularOrdered() const {return angularOrdered_;}
 
  bool pTScale() const {
    return scaleChoice_ == 2 ? angularOrdered_ : scaleChoice_ == 0;
  }
 
  void evaluateFinalStateScales(ShowerPartnerType type,
                                Energy scale, double z,
                                tShowerParticlePtr parent,
                                tShowerParticlePtr first,
                                tShowerParticlePtr second);
  void evaluateInitialStateScales(ShowerPartnerType type,
                                  Energy scale, double z,
                                  tShowerParticlePtr parent,
                                  tShowerParticlePtr first,
                                  tShowerParticlePtr second);
 
  void evaluateDecayScales(ShowerPartnerType type,
                           Energy scale, double z,
                           tShowerParticlePtr parent,
                           tShowerParticlePtr first,
                           tShowerParticlePtr second);
 
public:
 
  void persistentOutput(PersistentOStream & os) const;
 
  void persistentInput(PersistentIStream & is, int version);
 
  static void Init();
 
protected:
 
  virtual void doinit();
 
protected:
 
  void colourFactor(double in) {_colourFactor=in;}
 
private:
 
  SplittingFunction & operator=(const SplittingFunction &) = delete;
 
private:
 
  ShowerInteraction _interactionType;
 
  ColourStructure _colourStructure;
 
  double _colourFactor;
 
  bool angularOrdered_;
 
  unsigned int scaleChoice_;
 
  bool strictAO_;
 
};
 
}
 
#endif /* HERWIG_SplittingFunction_H */