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MEPP2HiggsVBF.h
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MEPP2HiggsVBF.h
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// -*- C++ -*-
#ifndef HERWIG_MEPP2HiggsVBF_H
#define HERWIG_MEPP2HiggsVBF_H
//
// This is the declaration of the MEPP2HiggsVBF class.
//
#include "Herwig/MatrixElement/MEfftoffH.h"
#include "Herwig/Shower/Couplings/ShowerAlpha.h"
namespace Herwig {
using namespace ThePEG;
/**
* The MEPP2HiggsVBF class provides the matrix elements for the
* production of the Higgs boson via the vector boson fusion mechanism
* in hadron collisions
*
* @see \ref MEPP2HiggsVBFInterfaces "The interfaces"
* defined for MEPP2HiggsVBF.
*/
class MEPP2HiggsVBF: public MEfftoffH {
/**
* Struct to contain the hadronic system
*/
struct tChannelPair{
/**
* The hadron
*/
PPtr hadron;
/**
* The beam particle data object
*/
tcBeamPtr beam;
/**
* The incoming particle
*/
ShowerParticlePtr incoming;
/**
* The outgoing particle
*/
ShowerParticlePtr outgoing;
/**
* The PDF
*/
tcPDFPtr pdf;
};
public:
/**
* The default constructor.
*/
MEPP2HiggsVBF();
/** @name Virtual functions required by the MEBase class. */
//@{
/**
* Add all possible diagrams with the add() function.
*/
virtual void getDiagrams() const;
//@}
/**
* Virtual members to be overridden by inheriting classes
* which implement hard corrections
*/
//@{
/**
* Has a POWHEG style correction
*/
virtual POWHEGType hasPOWHEGCorrection() {return Both;}
/**
* Has an old fashioned ME correction
*/
virtual bool hasMECorrection() {return true;}
/**
* Initialize the ME correction
*/
virtual void initializeMECorrection(ShowerTreePtr , double & ,
double & );
/**
* Apply the hard matrix element correction to a given hard process or decay
*/
virtual void applyHardMatrixElementCorrection(ShowerTreePtr);
/**
* Apply the soft matrix element correction
* @param initial The particle from the hard process which started the
* shower
* @param parent The initial particle in the current branching
* @param br The branching struct
* @return If true the emission should be vetoed
*/
virtual bool softMatrixElementVeto(ShowerProgenitorPtr,
ShowerParticlePtr,Branching);
/**
* Apply the POWHEG style correction
*/
virtual HardTreePtr generateHardest(ShowerTreePtr,
vector<ShowerInteraction::Type>);
//@}
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:
/**
* Generate the hardest emission in the POWHEG approach
*/
//@{
/**
* Generate a Compton process
*/
void generateCompton(unsigned int system);
/**
* Generate a BGF process
*/
void generateBGF(unsigned int system);
/**
* Matrix element piece for the Compton process
*/
double comptonME(unsigned int system,
double xT,double xp, double zp, double phi);
/**
* Matrix element piece for the Compton process
*/
double BGFME(unsigned int system,
double xT,double xp, double zp, double phi);
/**
* Leading order matrix element
*/
Energy4 loMatrixElement(const Lorentz5Momentum &p1,
const Lorentz5Momentum &p2,
const Lorentz5Momentum &q1,
const Lorentz5Momentum &q2,
double G1, double G2) const;
//@}
/**
* Generate the hard emission in the old-fashioned matrix element correction approach
*/
//@{
/**
* Generate the values of \f$x_p\f$ and \f$z_p\f$
* @param xp The value of xp, output
* @param zp The value of zp, output
*/
double generateComptonPoint(double &xp, double & zp);
/**
* Generate the values of \f$x_p\f$ and \f$z_p\f$
* @param xp The value of xp, output
* @param zp The value of zp, output
*/
double generateBGFPoint(double &xp, double & zp);
/**
* Return the coefficients for the matrix element piece for
* the QCD compton case. The output is the \f$a_i\f$ coefficients to
* give the function as
* \f$a_0+a_1\cos\phi+a_2\sin\phi+a_3\cos^2\phi+a_4\sin^2\phi\f$
* @param xp \f$x_p\f$
* @param x2 \f$x_2\f$
* @param xperp \f$x_\perp\f$
* @param l Scaled momentum of incoming spectator
* @param m Scaled momentum of outgoing spectator
*
*/
vector<double> ComptonME(double xp, double x2, double xperp,
LorentzVector<double> l,
LorentzVector<double> m);
/**
* Return the coefficients for the matrix element piece for
* the QCD compton case. The output is the \f$a_i\f$ coefficients to
* give the function as
* \f$a_0+a_1\cos\phi+a_2\sin\phi+a_3\cos^2\phi+a_4\sin^2\phi\f$
* @param xp \f$x_p\f$
* @param x2 \f$x_3\f$
* @param x3 \f$x_2\f$
* @param xperp \f$x_\perp\f$
* @param l Scaled momentum of incoming spectator
* @param m Scaled momentum of outgoing spectator
*
*/
vector<double> BGFME(double xp, double x2, double x3, double xperp,
LorentzVector<double> l,
LorentzVector<double> m);
/**
* Calculate the coefficient A for the correlations
*/
double A(tcPDPtr qin1, tcPDPtr qout1, tcPDPtr qin2, tcPDPtr qout2);
//@}
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();
/**
* Finalize this object. Called in the run phase just after a
* run has ended. Used eg. to write out statistics.
*/
virtual void dofinish();
//@}
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<MEPP2HiggsVBF> initMEPP2HiggsVBF;
/**
* The assignment operator is private and must never be called.
* In fact, it should not even be implemented.
*/
MEPP2HiggsVBF & operator=(const MEPP2HiggsVBF &);
private:
/**
* Parameters for the hard POWHEG emission
*/
//@{
/**
* Pointer to the object calculating the strong coupling
*/
ShowerAlphaPtr alpha_;
/**
* Weight for the compton channel
*/
double comptonWeight_;
/**
* Weight for the BGF channel
*/
double BGFWeight_;
/**
* Minimum value of \f$p_T\f$
*/
Energy pTmin_;
/**
* Gluon particle data object
*/
PDPtr gluon_;
//@}
/**
* Properties of the emission
*/
//@{
/**
* Beam particle
*/
tcBeamPtr beam_[2];
/**
* PDF object
*/
tcPDFPtr pdf_[2];
/**
* Partons
*/
tcPDPtr partons_[2][4];
/**
* q
*/
Lorentz5Momentum q_[2];
/**
* \f$Q^2\f$
*/
Energy2 q2_[2];
/**
* Coupling factor
*/
double acoeff_;
/**
* Lorentz vectors for the matrix element
*/
LorentzVector<double> l_;
/**
* Lorentz vectors for the matrix element
*/
LorentzVector<double> m_;
/**
* Born momentum fraction
*/
double xB_[2];
/**
* Rotation to the Breit frame
*/
LorentzRotation rot_[2];
/**
* Quark momenta for spectator system
*/
Lorentz5Momentum pother_[2][2];
/**
* Quark momenta for emitting system
*/
Lorentz5Momentum psystem_[2][2];
/**
* Higgs momenta
*/
Lorentz5Momentum phiggs_[2];
/**
* Transverse momenta for the compton emissions
*/
Energy pTCompton_[2];
/**
* Transverse momenta for the BGF emissions
*/
Energy pTBGF_[2];
/**
* Whether the Compton radiation is ISR or FSR
*/
bool ComptonISFS_[2];
/**
* Momenta of the particles for a compton emission
*/
vector<Lorentz5Momentum> ComptonMomenta_[2];
/**
* Momenta of the particles for a BGF emission
*/
vector<Lorentz5Momentum> BGFMomenta_[2];
/**
* the systems
*/
vector<tChannelPair> systems_;
/**
* Higgs boson
*/
ShowerParticlePtr higgs_;
//@}
/**
* Parameters for the matrix element correction
*/
//@{
/**
* Enchancement factor for ISR
*/
double initial_;
/**
* Enchancement factor for FSR
*/
double final_;
/**
* Relative fraction of compton and BGF processes to generate
*/
double procProb_;
/**
* Integral for compton process
*/
double comptonInt_;
/**
* Integral for BGF process
*/
double bgfInt_;
/**
* Number of weights greater than 1
*/
unsigned int nover_;
/**
* Maximum weight
*/
pair<double,double> maxwgt_;
//@}
};
}
#include "ThePEG/Utilities/ClassTraits.h"
namespace ThePEG {
/** @cond TRAITSPECIALIZATIONS */
/** This template specialization informs ThePEG about the
* base classes of MEPP2HiggsVBF. */
template <>
struct BaseClassTrait<Herwig::MEPP2HiggsVBF,1> {
/** Typedef of the first base class of MEPP2HiggsVBF. */
typedef Herwig::MEfftoffH NthBase;
};
/** This template specialization informs ThePEG about the name of
* the MEPP2HiggsVBF class and the shared object where it is defined. */
template <>
struct ClassTraits<Herwig::MEPP2HiggsVBF>
: public ClassTraitsBase<Herwig::MEPP2HiggsVBF> {
/** Return a platform-independent class name */
static string className() { return "Herwig::MEPP2HiggsVBF"; }
/**
* The name of a file containing the dynamic library where the class
* MEPP2HiggsVBF is implemented. It may also include several, space-separated,
* libraries if the class MEPP2HiggsVBF 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"; }
};
/** @endcond */
}
#endif /* HERWIG_MEPP2HiggsVBF_H */

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