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MEPP2ZHPowheg.h
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MEPP2ZHPowheg.h
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// -*- C++ -*-
#ifndef HERWIG_MEPP2ZHPowheg_H
#define HERWIG_MEPP2ZHPowheg_H
//
// This is the declaration of the MEPP2ZHPowheg class.
//
#include "Herwig++/MatrixElement/Hadron/MEPP2ZH.h"
#include "ThePEG/PDF/BeamParticleData.h"
namespace Herwig {
using namespace ThePEG;
/**
* The MEPP2ZHPowheg class implements the matrix element
* for \f$q\bar{q}\to Z^0h^0\f$.
*
* @see \ref MEPP2ZHPowhegInterfaces "The interfaces"
* defined for MEPP2ZHPowheg.
*/
class MEPP2ZHPowheg: public MEPP2ZH {
public:
/**
* The default constructor.
*/
MEPP2ZHPowheg();
/** @name Virtual functions required by the MEBase class. */
//@{
/**
* Return the scale associated with the last set phase space point.
*/
virtual Energy2 scale() const;
/**
* The number of internal degreed of freedom used in the matrix
* element.
*/
virtual int nDim() const;
/**
* Generate internal degrees of freedom given 'nDim()' uniform
* random numbers in the interval ]0,1[. To help the phase space
* generator, the 'dSigHatDR()' should be a smooth function of these
* numbers, although this is not strictly necessary. Return
* false if the chosen points failed the kinematical cuts.
*/
virtual bool generateKinematics(const double * r);
/**
* Return the matrix element for the kinematical configuation
* previously provided by the last call to setKinematics(). Uses
* me().
*/
virtual CrossSection dSigHatDR() const;
//@}
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:
/**
* Calculate the correction weight with which leading-order
* configurations are re-weighted.
*/
double NLOweight() const;
/**
* Calculate the variable \f$x=M_{B}^2/s\f$ from the integration variables.
*/
double x(double xt, double v) const;
/**
* Calculate the momentum fraction of the first parton.
*/
double x_a(double x, double v) const;
/**
* Calculate the momentum fraction of second parton.
*/
double x_b(double x, double v) const;
/**
* Calculate the minimum of \f$x\f$.
*/
double xbar(double v) const;
/**
* Calculate the ratio of the radiative luminosity funcion to the
* Born luminosity function for the \f$qg\f$ initiated channel.
*/
double Ltilde_qg(double x, double v) const;
/**
* Calculate the ratio of the radiative luminosity funcion to the
* Born luminosity function for the \f$g\bar{q}\f$ initiated channel.
*/
double Ltilde_gq(double x, double v) const;
/**
* Calculate the ratio of the radiative luminosity funcion to the
* Born luminosity function for the \f$q\bar{q}\f$ initiated channel.
*/
double Ltilde_qq(double x, double v) const;
/**
* Calculate the soft-virtual contribution to the NLO weight.
*/
double Vtilde_qq() const;
/**
* Function for calculation of the \f$g\bar{q}\f$ and \f$g\bar{q}\f$
* initiated real contribution.
*/
double Ccalbar_qg(double x) const;
/**
* Function for calculation of the \f$qg\f$
* initiated real contribution.
*/
double Fcal_qg(double x, double v) const;
/**
* Function for calculation of the \f$g\bar{q}\f$ initiated real
* contribution.
*/
double Fcal_gq(double x, double v) const;
/**
* Function for calculation of the \f$q\bar{q}\f$ initiated real
* contribution.
*/
double Fcal_qq(double x, double v) const;
/**
* Function for calculation of the \f$qg\f$ initiated real
* contribution.
*/
double Ftilde_qg(double xt, double v) const;
/**
* Function for calculation of the \f$g\bar{q}\f$ initiated real
* contribution.
*/
double Ftilde_gq(double xt, double v) const;
/**
* Function for calculation of the \f$q\bar{q}\f$ initiated real
* contribution.
*/
double Ftilde_qq(double xt, double v) const;
/**
* Function for calculation of the \f$qg\f$ initiated real
* contribution.
*/
double Ctilde_qg(double x, double v) const;
/**
* Function for calculation of the \f$g\bar{q}\f$ initiated real
* contribution.
*/
double Ctilde_gq(double x, double v) const;
/**
* Function for calculation of the \f$q\bar{q}\f$ initiated real
* contribution.
*/
double Ctilde_qq(double x, double v) const;
protected:
/** @name Clone Methods. */
//@{
/**
* Make a simple clone of this object.
* @return a pointer to the new object.
*/
inline 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.
*/
inline 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();
//@}
private:
/**
* The static object used to initialize the description of this class.
* Indicates that this is a concrete class with persistent data.
*/
static ClassDescription<MEPP2ZHPowheg> initMEPP2ZHPowheg;
/**
* The assignment operator is private and must never be called.
* In fact, it should not even be implemented.
*/
MEPP2ZHPowheg & operator=(const MEPP2ZHPowheg &);
private:
/**
* The momentum fraction of the first parton in the Born process
*/
mutable double _xb_a;
/**
* The momentum fraction of the second parton in the Born process
*/
mutable double _xb_b;
/**
* The ParticleData object for the first parton in the Born process
*/
mutable tcPDPtr _parton_a;
/**
* The ParticleData object for the second parton in the Born process
*/
mutable tcPDPtr _parton_b;
/**
* The BeamParticleData object for the first hadron
*/
mutable Ptr<BeamParticleData>::transient_const_pointer _hadron_A;
/**
* The BeamParticleData object for the second hadron
*/
mutable Ptr<BeamParticleData>::transient_const_pointer _hadron_B;
/**
* the ParticleData object for the gluon
*/
tcPDPtr _gluon;
/**
* The \f$T_R\f$ colour factor
*/
const double _TR;
/**
* The \f$C_F\f$ colour factor
*/
const double _CF;
/**
* The value of \f$\frac{\alpha_S}{2\pi}\f$ used for the calculation
*/
mutable double _alphaS2Pi;
/**
* The mass squared of the lepton pair
*/
mutable Energy2 _mll2;
/**
* The renormalization/factorization scale
*/
mutable Energy2 _mu2;
/**
* Parameters for the NLO weight
*/
//@{
/**
* Whether to generate the positive, negative or leading order contribution
*/
unsigned int _contrib;
/**
* Whether to use a fixed or a running QCD coupling for the NLO weight
*/
unsigned int _nlo_alphaS_opt;
/**
* The value of alphaS to use for the nlo weight if _nloalphaSopt=1
*/
double _fixed_alphaS;
/**
* The magnitude of the correction term to reduce the negative contribution
*/
double _a;
/**
* The power of the correction term to reduce the negative contribution
*/
double _p;
/**
* Cut-off for the correction function
*/
double _eps;
//@}
/**
* Choice of the scale
*/
//@{
/**
* Type of scale
*/
unsigned int _scaleopt;
/**
* Fixed scale if used
*/
Energy _fixedScale;
/**
* Prefactor if variable scale used
*/
double _scaleFact;
//@}
/**
* Radiation variables
*/
//@{
/**
* The \f$\tilde{x}\f$ variable
*/
double _xt;
/**
* The \f$v\f$ angular variable
*/
double _v;
//@}
/**
* Values of the PDF's before radiation
*/
//@{
/**
* For the quark
*/
mutable double _oldq;
/**
* For the antiquark
*/
mutable double _oldqbar;
//@}
};
}
#include "ThePEG/Utilities/ClassTraits.h"
namespace ThePEG {
/** @cond TRAITSPECIALIZATIONS */
/** This template specialization informs ThePEG about the
* base classes of MEPP2ZHPowheg. */
template <>
struct BaseClassTrait<Herwig::MEPP2ZHPowheg,1> {
/** Typedef of the first base class of MEPP2ZHPowheg. */
typedef Herwig::MEPP2ZH NthBase;
};
/** This template specialization informs ThePEG about the name of
* the MEPP2ZHPowheg class and the shared object where it is defined. */
template <>
struct ClassTraits<Herwig::MEPP2ZHPowheg>
: public ClassTraitsBase<Herwig::MEPP2ZHPowheg> {
/** Return a platform-independent class name */
static string className() { return "Herwig::MEPP2ZHPowheg"; }
/**
* The name of a file containing the dynamic library where the class
* MEPP2ZHPowheg is implemented. It may also include several, space-separated,
* libraries if the class MEPP2ZHPowheg depends on other classes (base classes
* excepted). In this case the listed libraries will be dynamically
* linked in the order they are specified.
*/
static string library() { return "HwMEHadron.so HwPowhegME.so"; }
};
/** @endcond */
}
#endif /* HERWIG_MEPP2ZHPowheg_H */

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