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MEGGto3P2.h
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// -*- C++ -*-
#ifndef Herwig_MEGGto3P2_H
#define Herwig_MEGGto3P2_H
//
// This is the declaration of the MEGGto3P2 class.
//
#include "Herwig/MatrixElement/HwMEBase.h"
#include "ThePEG/Helicity/WaveFunction/ScalarWaveFunction.h"
#include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
#include "Herwig/PDT/GenericMassGenerator.h"
#include "Herwig/MatrixElement/ProductionMatrixElement.h"
#include "OniumParameters.h"
namespace Herwig {
using namespace ThePEG;
/**
* The MEGGto3P2 class implements the colour singlet matrix element for \f$gg\to^3\!\!P_2\f$ quarkonium.
*
* @see \ref MEGGto3P2Interfaces "The interfaces"
* defined for MEGGto3P2.
*/
class MEGGto3P2: public HwMEBase {
public:
/** @name Standard constructors and destructors. */
//@{
/**
* The default constructor.
*/
MEGGto3P2() : O1_(ZERO), state_(ccbar), n_(1)
{}
//@}
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 2;
}
/**
* Return the order in \f$\alpha_{EW}\f$ in which this matrix
* element is given.
*/
virtual unsigned int orderInAlphaEW() const {
return 0;
}
/**
* 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;
/**
* 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;
/**
* 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 matrix element squared differential in the variables
* given by the last call to generateKinematics().
*/
virtual CrossSection dSigHatDR() 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;
/** 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;
//@}
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();
//@}
private:
/**
* The assignment operator is private and must never be called.
* In fact, it should not even be implemented.
*/
MEGGto3P2 & operator=(const MEGGto3P2 &) = delete;
private:
/**
* Parameters for the form-factors
*/
//@{
/**
* Access to the parameters for the quarkonium states
*/
OniumParametersPtr params_;
/**
* The \f$O_1\f$ colour-singlet coefficient
*/
Energy5 O1_;
/**
* Type of state
*/
OniumState state_;
/**
* Principal quantum number
*/
unsigned int n_;
/**
* The mass generator for the Higgs
*/
GenericMassGeneratorPtr massGen_;
//@}
};
}
#endif /* Herwig_MEGGto3P2_H */

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