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// -*- C++ -*-
//
// FFggxDipole.cc is a part of Herwig - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2019 The Herwig Collaboration
//
// Herwig is licenced under version 3 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
//
// This is the implementation of the non-inlined, non-templated member
// functions of the FFggxDipole class.
//
#include "FFggxDipole.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Utilities/DescribeClass.h"
#include "ThePEG/MatrixElement/Tree2toNDiagram.h"
#include "ThePEG/StandardModel/StandardModelBase.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "Herwig/MatrixElement/Matchbox/Base/DipoleRepository.h"
#include "Herwig/MatrixElement/Matchbox/Utility/SpinCorrelationTensor.h"
#include "Herwig/MatrixElement/Matchbox/Phasespace/FFLightTildeKinematics.h"
#include "Herwig/MatrixElement/Matchbox/Phasespace/FFLightInvertedTildeKinematics.h"
using namespace Herwig;
FFggxDipole::FFggxDipole()
: SubtractionDipole() {}
IBPtr FFggxDipole::clone() const {
return new_ptr(*this);
}
IBPtr FFggxDipole::fullclone() const {
return new_ptr(*this);
}
bool FFggxDipole::canHandle(const cPDVector& partons,
int emitter, int emission, int spectator) const {
return
emitter > 1 && spectator > 1 &&
partons[emission]->id() == ParticleID::g &&
partons[emitter]->id() == ParticleID::g &&
partons[spectator]->hardProcessMass() == ZERO;
}
double FFggxDipole::me2Avg(double ccme2) const {
if ( jacobian() == 0.0 )
return 0.0;
double y = subtractionParameters()[0];
double z = subtractionParameters()[1];
Energy2 prop =
2.*((realEmissionME()->lastXComb().meMomenta()[realEmitter()])*
(realEmissionME()->lastXComb().meMomenta()[realEmission()]));
double res =
1./(1.-z*(1.-y)) + 1./(1.-(1.-z)*(1.-y)) - 2. + z*(1.-z);
res *= -ccme2;
res *= 16.*Constants::pi*SM().Nc()*(realEmissionME()->lastXComb().lastSHat())*
(underlyingBornME()->lastXComb().lastAlphaS())/prop;
res *=
realEmissionME()->finalStateSymmetry() /
underlyingBornME()->finalStateSymmetry();
return res;
}
double FFggxDipole::me2() const {
if ( jacobian() == 0.0 )
return 0.0;
double y = subtractionParameters()[0];
double z = subtractionParameters()[1];
if ( alpha() < y )
return 0.0;
Energy2 prop =
2.*((realEmissionME()->lastXComb().meMomenta()[realEmitter()])*
(realEmissionME()->lastXComb().meMomenta()[realEmission()]));
double diag = 1./(1.-z*(1.-y))+1./(1.-(1.-z)*(1.-y))-2.;
Lorentz5Momentum pc =
z*realEmissionME()->lastXComb().meMomenta()[realEmitter()] -
(1.-z)*realEmissionME()->lastXComb().meMomenta()[realEmission()];
SpinCorrelationTensor corr(-diag,pc,prop/2.);
double res = -underlyingBornME()->spinColourCorrelatedME2(make_pair(bornEmitter(),bornSpectator()),
corr);
res *= 16.*Constants::pi*SM().Nc()*(realEmissionME()->lastXComb().lastSHat())*
(underlyingBornME()->lastXComb().lastAlphaS())/prop;
res *=
realEmissionME()->finalStateSymmetry() /
underlyingBornME()->finalStateSymmetry();
return res;
}
void FFggxDipole::persistentOutput(PersistentOStream &) const {
}
void FFggxDipole::persistentInput(PersistentIStream &, int) {
}
void FFggxDipole::Init() {
static ClassDocumentation<FFggxDipole> documentation
("FFggxDipole");
DipoleRepository::registerDipole<0,FFggxDipole,FFLightTildeKinematics,FFLightInvertedTildeKinematics>
("FFggxDipole","FFLightTildeKinematics","FFLightInvertedTildeKinematics");
}
// *** Attention *** The following static variable is needed for the type
// description system in ThePEG. Please check that the template arguments
// are correct (the class and its base class), and that the constructor
// arguments are correct (the class name and the name of the dynamically
// loadable library where the class implementation can be found).
DescribeClass<FFggxDipole,SubtractionDipole>
describeHerwigFFggxDipole("Herwig::FFggxDipole", "Herwig.so");

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