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GluinotoGluinoGSplitFn.cc
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GluinotoGluinoGSplitFn.cc
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// -*- C++ -*-
//
// GluinotoGluinoGSplitFn.cc is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2007 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.
//
//
// This is the implementation of the non-inlined, non-templated member
// functions of the GluinotoGluinoGSplitFn class.
//
#include "GluinotoGluinoGSplitFn.h"
#include "ThePEG/PDT/ParticleData.h"
#include "ThePEG/PDT/EnumParticles.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "Herwig++/Shower/Base/ShowerParticle.h"
#include "ThePEG/Repository/UseRandom.h"
#include <cassert>
using namespace Herwig;
NoPIOClassDescription<GluinotoGluinoGSplitFn>
GluinotoGluinoGSplitFn::initGluinotoGluinoGSplitFn;
// Definition of the static class description member.
void GluinotoGluinoGSplitFn::Init() {
static ClassDocumentation<GluinotoGluinoGSplitFn> documentation
("The GluinotoGluinoGSplitFn class implements the splitting function for "
"gluino -> gluino g");
}
double GluinotoGluinoGSplitFn::P(const double z, const Energy2 t,
const IdList &ids, const bool mass) const {
double val = (1. + sqr(z))/(1.-z);
if(mass) {
Energy m = getParticleData(ids[0])->mass();
val -= 2.*sqr(m)/t;
}
return 3.*val;
}
double GluinotoGluinoGSplitFn::overestimateP(const double z, const IdList &) const {
return 6./(1.-z);
}
double GluinotoGluinoGSplitFn::ratioP(const double z, const Energy2 t,
const IdList &ids, const bool mass) const {
double val = 1. + sqr(z);
if(mass) {
Energy m = getParticleData(ids[0])->mass();
val -= 2.*sqr(m)*(1.-z)/t;
}
return 0.5*val;
}
double GluinotoGluinoGSplitFn::integOverP(const double z, const IdList & ,
unsigned int PDFfactor) const {
switch(PDFfactor) {
case 0:
return -6.*log(1.-z);
case 1:
case 2:
case 3:
default:
throw Exception() << "GluinotoGluinoGSplitFn::integOverP() invalid PDFfactor = "
<< PDFfactor << Exception::runerror;
}
}
double GluinotoGluinoGSplitFn::invIntegOverP(const double r, const IdList & ,
unsigned int PDFfactor) const {
switch(PDFfactor) {
case 0:
return 1. - exp(-r/6.);
case 1:
case 2:
case 3:
default:
throw Exception() << "GluinotoGluinoGSplitFn::integOverP() invalid PDFfactor = "
<< PDFfactor << Exception::runerror;
}
}
void GluinotoGluinoGSplitFn::colourConnection(tShowerParticlePtr parent,
tShowerParticlePtr first,
tShowerParticlePtr second,
const bool back) const {
if(!back) {
ColinePair cparent = ColinePair(parent->colourLine(),
parent->antiColourLine());
// ensure input consistency
assert(cparent.first&&cparent.second);
// Randomly decide which of the two gluon products take the
// colour line passing for the colour of the parent gluon
// (the other will take the one passing for the anticolour of
// the parent gluon).
if(UseRandom::rndbool()) {
ColinePtr newline=new_ptr(ColourLine());
cparent.first->addColoured(first);
cparent.second->addAntiColoured(second);
newline->addColoured(second);
newline->addAntiColoured(first);
}
else {
ColinePtr newline=new_ptr(ColourLine());
cparent.first->addColoured(second);
cparent.second->addAntiColoured(first);
newline->addColoured(first);
newline->addAntiColoured(second);
}
}
else {
ColinePair cfirst = ColinePair(first->colourLine(),
first->antiColourLine());
// ensure input consistency
assert(cfirst.first&&cfirst.second);
// Randomly decide which of the two gluon products take the
// colour line passing for the colour of the parent gluon
// (the other will take the one passing for the anticolour of
// the parent gluon).
if (UseRandom::rndbool()) {
ColinePtr newline=new_ptr(ColourLine());
cfirst.first->addColoured(parent);
cfirst.second->addColoured(second);
newline->addAntiColoured(second);
newline->addAntiColoured(parent);
}
else {
ColinePtr newline=new_ptr(ColourLine());
cfirst.first->addAntiColoured(second);
cfirst.second->addAntiColoured(parent);
newline->addColoured(parent);
newline->addColoured(second);
}
}
}
bool GluinotoGluinoGSplitFn::accept(const IdList &ids) const {
if(ids.size()!=3) return false;
if(ids[0]!=ids[1]||ids[2]!=ParticleID::g) return false;
tcPDPtr q=getParticleData(ids[0]);
return q->iSpin()==PDT::Spin1Half&&q->iColour()==PDT::Colour8;
}

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