MEGammaGamma2PiPi.h

// -*- C++ -*-
#ifndef Herwig_MEGammaGamma2PiPi_H
#define Herwig_MEGammaGamma2PiPi_H
//
// This is the declaration of the MEGammaGamma2PiPi class.
//
 
#include "Herwig/MatrixElement/HwMEBase.h"
#include "Herwig/MatrixElement/ProductionMatrixElement.h"
#include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
 
namespace Herwig {
 
using namespace ThePEG;
using ThePEG::Helicity::VectorWaveFunction;
 
class MEGammaGamma2PiPi: public HwMEBase {
 
public:
 
  MEGammaGamma2PiPi();
 
public:
 
  virtual unsigned int orderInAlphaS() const;
 
  virtual unsigned int orderInAlphaEW() const;
 
  virtual double me2() const;
 
  virtual Energy2 scale() const;
 
  virtual void getDiagrams() const;
 
  virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
 
  virtual Selector<const ColourLines *>
  colourGeometries(tcDiagPtr diag) const;
 
  virtual void constructVertex(tSubProPtr);
 
public:
 
  static void Init();
 
protected:
 
  double helicityME(vector<VectorWaveFunction> &p1,vector<VectorWaveFunction> &p2,
                    const vector<Lorentz5Momentum> & momenta,
                    bool calc) const;
 
protected:
 
  virtual IBPtr clone() const;
 
  virtual IBPtr fullclone() const;
 
private:
 
  MEGammaGamma2PiPi & operator=(const MEGammaGamma2PiPi &) = delete;
 
private:
 
  mutable ProductionMatrixElement me_;
 
};
 
}
 
#endif /* Herwig_MEGammaGamma2PiPi_H */