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MEPP2HiggsPowheg.h
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MEPP2HiggsPowheg.h
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// -*- C++ -*-
//
// MEPP2HiggsPowheg.h is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2011 The Herwig Collaboration
//
// Herwig++ is licenced under version 2 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
#ifndef HERWIG_MEPP2HiggsPowheg_H
#define HERWIG_MEPP2HiggsPowheg_H
//
// This is the declaration of the MEPP2HiggsPowheg class.
//
#include "Herwig++/MatrixElement/Hadron/MEPP2Higgs.h"
#include "ThePEG/PDF/BeamParticleData.h"
namespace Herwig {
using namespace ThePEG;
using namespace ThePEG::Helicity;
/**
* The MEPP2HiggsPowheg 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 MEPP2HiggsPowhegInterfaces "The interfaces"
* defined for MEPP2HiggsPowheg.
*/
class MEPP2HiggsPowheg: public MEPP2Higgs {
public:
/**
* The default constructor.
*/
MEPP2HiggsPowheg();
public:
/** @name Virtual functions required by the MEBase class. */
//@{
/**
* 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;
//@}
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();
/**
* Function to set the born variables.
*/
void get_born_variables() const;
/**
* Calculate the correction weight with which leading-order
* configurations are re-weighted.
*/
double NLOweight() const;
/**
* Invariant required for the evaluation of next-to-leading order
* quantities (Frixione et al. NPB.383 WZ production at colliders).
*/
Energy2 s(double xt, double y) const {
return p2_/x(xt,y);
}
/**
* Invariant required for the evaluation of next-to-leading order
* quantities (Frixione et al. NPB.383 WZ production at colliders).
*/
Energy2 tk(double xt, double y) const {
double x_xt_y(x(xt,y));
return -0.5*p2_/x_xt_y*(1.- x_xt_y)*(1.-y);
}
/**
* Invariant required for the evaluation of next-to-leading order
* quantities (Frixione et al. NPB.383 WZ production at colliders).
*/
Energy2 uk(double xt, double y) const {
double x_xt_y(x(xt,y));
return -0.5*p2_/x_xt_y*(1.- x_xt_y)*(1.+y);
}
/**
* Calculate the minimum of \f$x\f$.
*/
double xbar(double y) const;
/**
* Calculate auxiliary function of \f$\bar{x}(y)\f$, \f$\bar{\eta}(y)\f$.
*/
double etabar(double y) const;
/**
* Calculate the variable \f$x=p^{2}/s\f$ from the integration variables.
*/
double x(double xt, double y) const {
double x0(xbar(y));
return x0+(1.-x0)*xt;
}
/**
* Calculate the momentum fraction of the plus parton.
*/
double xp(double x, double y) const;
/**
* Calculate the momentum fraction of the minus parton.
*/
double xm(double x, double y) const;
/**
* Calculate the ratio of the NLO luminosity to the LO
* luminosity function for the \f$q\bar{q}\f$ initiated channel.
*/
double Lhat_ab(tcPDPtr a, tcPDPtr b, double x, double y) const;
/**
* Calculate the universal soft-virtual contribution to the NLO weight.
*/
double Vtilde_universal() const;
/**
* Function for calculation of the \f$gg\f$ initiated real
* contribution.
*/
double Ctilde_Ltilde_gg_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
/**
* Function for calculation of the \f$qg\f$ initiated real
* contribution.
*/
double Ctilde_Ltilde_qg_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
/**
* Function for calculation of the \f$gq\f$ initiated real
* contribution.
*/
double Ctilde_Ltilde_gq_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
/**
* The regular part of the virtual correction matrix element(s)
*/
double M_V_regular() const;
/**
* The matrix element q + qbar -> n + g times tk*uk
*/
Energy2 t_u_M_R_qqbar(double xt, double y) const;
/**
* The matrix element qbar + q -> n + g times tk*uk
*/
Energy2 t_u_M_R_qbarq(double xt, double y) const;
/**
* The matrix element g + g -> n + g times tk*uk
*/
Energy2 t_u_M_R_gg(double xt, double y) const;
/**
* The matrix element q + g -> n + q times tk*uk
*/
Energy2 t_u_M_R_qg(double xt, double y) const;
/**
* The matrix element g + q -> n + q times tk*uk
*/
Energy2 t_u_M_R_gq(double xt, double y) const;
/**
* Function for calculation of the \f$q\bar{q}\f$ initiated real
* contribution.
*/
double Rtilde_Ltilde_qqbar_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
/**
* Function for calculation of the \f$\bar{q}q\f$ initiated real
* contribution.
*/
double Rtilde_Ltilde_qbarq_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
/**
* Function for calculation of the \f$qq\f$
* initiated real contribution.
*/
double Rtilde_Ltilde_gg_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
/**
* Function for calculation of the \f$qg\f$ initiated real
* contribution.
*/
double Rtilde_Ltilde_qg_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
/**
* Function for calculation of the \f$gq\f$ initiated real
* contribution.
*/
double Rtilde_Ltilde_gq_on_x(tcPDPtr a,tcPDPtr b,double xt,double y) const;
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); }
//@}
private:
/**
* The static object used to initialize the description of this class.
* Indicates that this is a concrete class with persistent data.
*/
static ClassDescription<MEPP2HiggsPowheg> initMEPP2HiggsPowheg;
/**
* The assignment operator is private and must never be called.
* In fact, it should not even be implemented.
*/
MEPP2HiggsPowheg & operator=(const MEPP2HiggsPowheg &);
private:
/**
* Parameters for the NLO weight
*/
//@{
/**
* The colour factors
*/
const double CF_ , CA_ , TR_;
/**
* Number of light flavours (in the beta function beta0_)
*/
const int nlf_;
/**
* (Proportional to) The beta function
*/
const double beta0_;
/**
* 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 nlo_alphaS_opt_=1
*/
double fixed_alphaS_;
//@}
/**
* Radiation variables
*/
//@{
/**
* The \f$\tilde{x}\f$ variable
*/
double xt_;
/**
* The \f$y\f$ angular variable
*/
double y_;
//@}
/**
* Values of the PDF's before radiation
*/
mutable double lo_lumi_;
/**
* The value of the leading order gg->H matrix element
*/
mutable double lo_ggME_;
/**
* The invariant mass of the lo final state.
*/
mutable Energy2 p2_ ;
/**
* The invariant mass of the lo final state.
*/
mutable Energy2 s2_ ;
/**
* The momentum fraction of the plus parton in the Born process
*/
mutable double xbp_;
/**
* The momentum fraction of the minus parton in the Born process
*/
mutable double xbm_;
/**
* The sqrt(1-xbp_)
*/
mutable double etabarp_;
/**
* The sqrt(1-xbm_)
*/
mutable double etabarm_;
/**
* The ParticleData object for the plus lo parton
*/
mutable tcPDPtr a_lo_;
/**
* The ParticleData object for the minus lo parton
*/
mutable tcPDPtr b_lo_;
/**
* The BeamParticleData object for the plus direction hadron
*/
mutable Ptr<BeamParticleData>::transient_const_pointer hadron_A_;
/**
* The BeamParticleData object for the minus direction hadron
*/
mutable Ptr<BeamParticleData>::transient_const_pointer hadron_B_;
/**
* The value of \f$\alpha_S\f$ used for the calculation
*/
mutable double alphaS_;
/**
* Selects a dynamic (sHat) or fixed factorization scale
*/
unsigned int scaleopt_;
/**
* The factorization scale
*/
Energy mu_F_;
/**
* The renormalization scale
*/
Energy mu_UV_;
/**
* Prefactor if variable scale used
*/
double scaleFact_;
};
}
#include "ThePEG/Utilities/ClassTraits.h"
namespace ThePEG {
/** @cond TRAITSPECIALIZATIONS */
/** This template specialization informs ThePEG about the base classes of MEPP2HiggsPowheg. */
template <>
struct BaseClassTrait<Herwig::MEPP2HiggsPowheg,1> {
/** Typedef of the first base class of MEPP2HiggsPowheg. */
typedef Herwig::MEPP2Higgs NthBase;
};
/** This template specialization informs ThePEG about the name of
* the MEPP2HiggsPowheg class and the shared object where it is defined. */
template <>
struct ClassTraits<Herwig::MEPP2HiggsPowheg>
: public ClassTraitsBase<Herwig::MEPP2HiggsPowheg> {
/** Return a platform-independent class name */
static string className() { return "Herwig::MEPP2HiggsPowheg"; }
/**
* The name of a file containing the dynamic library where the class
* MEPP2HiggsPowheg is implemented. It may also include several, space-separated,
* libraries if the class MEPP2HiggsPowheg 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 HwPowhegMEHadron.so"; }
};
/** @endcond */
}
#endif /* HERWIG_MEPP2HiggsPowheg_H */

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