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MEQCD2to2.cc
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// -*- C++ -*-
//
// MEQCD2to2.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 MEQCD2to2 class.
//
#include "MEQCD2to2.h"
#include "ThePEG/Utilities/SimplePhaseSpace.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Interface/Switch.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/Repository/EventGenerator.h"
#include "ThePEG/PDT/EnumParticles.h"
#include "ThePEG/MatrixElement/Tree2toNDiagram.h"
#include "Herwig++/Models/StandardModel/StandardModel.h"
#include "ThePEG/Handlers/StandardXComb.h"
#include "ThePEG/Cuts/Cuts.h"
#include "Herwig++/MatrixElement/HardVertex.h"
using namespace Herwig;MEQCD2to2::MEQCD2to2():_maxflavour(5),_process(0) {
massOption(true ,0);
massOption(false,0);
}
void MEQCD2to2::rebind(const TranslationMap & trans)
{
_ggggvertex = trans.translate(_ggggvertex);
_gggvertex = trans.translate( _gggvertex);
_qqgvertex = trans.translate( _qqgvertex);
_gluon = trans.translate( _gluon);
for(unsigned int ix=0;ix<_quark.size();++ix)
{_quark[ix]=trans.translate(_quark[ix]);}
for(unsigned int ix=0;ix<_antiquark.size();++ix)
{_antiquark[ix]=trans.translate(_quark[ix]);}
HwME2to2Base::rebind(trans);
}
IVector MEQCD2to2::getReferences() {
IVector ret = HwME2to2Base::getReferences();
ret.push_back(_ggggvertex);
ret.push_back(_gggvertex);
ret.push_back(_qqgvertex);
ret.push_back(_gluon);
for(unsigned int ix=0;ix<_quark.size();++ix)
{ret.push_back(_quark[ix]);}
for(unsigned int ix=0;ix<_antiquark.size();++ix)
{ret.push_back(_antiquark[ix]);}
return ret;
}
void MEQCD2to2::doinit() {
// call the base class
HwME2to2Base::doinit();
// get the vedrtex pointers from the SM object
tcHwSMPtr hwsm= dynamic_ptr_cast<tcHwSMPtr>(standardModel());
// do the initialisation
if(hwsm) {
_qqgvertex = hwsm->vertexFFG();
_gggvertex = hwsm->vertexGGG();
_ggggvertex = hwsm->vertexGGGG();
}
else throw InitException() << "Wrong type of StandardModel object in "
<< "MEQCD2to2::doinit() the Herwig++ version must be used"
<< Exception::runerror;
// get the particle data objects
_gluon=getParticleData(ParticleID::g);
for(int ix=1;ix<=int(_maxflavour);++ix) {
_quark.push_back( getParticleData( ix));
_antiquark.push_back(getParticleData(-ix));
}
}
Energy2 MEQCD2to2::scale() const {
Energy2 s(sHat()),u(uHat()),t(tHat());
return 2.*s*t*u/(s*s+t*t+u*u);
}
void MEQCD2to2::persistentOutput(PersistentOStream & os) const {
os << _ggggvertex << _gggvertex << _qqgvertex << _maxflavour
<< _process << _gluon << _quark << _antiquark;
}
void MEQCD2to2::persistentInput(PersistentIStream & is, int) {
is >> _ggggvertex >> _gggvertex >> _qqgvertex >> _maxflavour
>> _process >> _gluon >> _quark >> _antiquark;
}
unsigned int MEQCD2to2::orderInAlphaS() const {
return 2;
}
unsigned int MEQCD2to2::orderInAlphaEW() const {
return 0;
}
ClassDescription<MEQCD2to2> MEQCD2to2::initMEQCD2to2;
// Definition of the static class description member.
void MEQCD2to2::Init() {
static ClassDocumentation<MEQCD2to2> documentation
("The MEQCD2to2 class implements the QCD 2->2 processes in hadron-hadron"
" collisions");
static Parameter<MEQCD2to2,unsigned int> interfaceMaximumFlavour
("MaximumFlavour",
"The maximum flavour of the quarks in the process",
&MEQCD2to2::_maxflavour, 5, 1, 5,
false, false, Interface::limited);
static Switch<MEQCD2to2,unsigned int> interfaceProcess
("Process",
"Which subprocesses to include",
&MEQCD2to2::_process, 0, false, false);
static SwitchOption interfaceProcessAll
(interfaceProcess,
"All",
"Include all subprocesses",
0);
static SwitchOption interfaceProcess1
(interfaceProcess,
"gg2gg",
"Include only gg->gg subprocesses",
1);
static SwitchOption interfaceProcess2
(interfaceProcess,
"gg2qqbar",
"Include only gg -> q qbar processes",
2);
static SwitchOption interfaceProcessqqbargg
(interfaceProcess,
"qqbar2gg",
"Include only q qbar -> gg processes",
3);
static SwitchOption interfaceProcessqgqg
(interfaceProcess,
"qg2qg",
"Include only q g -> q g processes",
4);
static SwitchOption interfaceProcessqbargqbarg
(interfaceProcess,
"qbarg2qbarg",
"Include only qbar g -> qbar g processes",
5);
static SwitchOption interfaceProcessqqqq
(interfaceProcess,
"qq2qq",
"Include only q q -> q q processes",
6);
static SwitchOption interfaceProcessqbarqbarqbarqbar
(interfaceProcess,
"qbarqbar2qbarqbar",
"Include only qbar qbar -> qbar qbar processes",
7);
static SwitchOption interfaceProcessqqbarqqbar
(interfaceProcess,
"qqbar2qqbar",
"Include only q qbar -> q qbar processes",
8);
}
Selector<MEBase::DiagramIndex>
MEQCD2to2::diagrams(const DiagramVector & diags) const {
// select the diagram, this is easy for us as we have already done it
Selector<DiagramIndex> sel;
for ( DiagramIndex i = 0; i < diags.size(); ++i ) {
if(diags[i]->id()==-int(_diagram)) sel.insert(1.0, i);
else sel.insert(0., i);
}
return sel;
}
double MEQCD2to2::gg2qqbarME(vector<VectorWaveFunction> &g1,
vector<VectorWaveFunction> &g2,
vector<SpinorBarWaveFunction> & q,
vector<SpinorWaveFunction> & qbar,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
// matrix element to be stored
if(iflow!=0) _me.reset(ProductionMatrixElement(PDT::Spin1,PDT::Spin1,
PDT::Spin1Half,PDT::Spin1Half));
// calculate the matrix element
double output(0.),sumdiag[3]={0.,0.,0.},sumflow[2]={0.,0.};
Complex diag[3],flow[2];
VectorWaveFunction interv;
SpinorWaveFunction inters;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
interv=_gggvertex->evaluate(mt,5,_gluon,g1[ihel1],g2[ihel2]);
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
//first t-channel diagram
inters =_qqgvertex->evaluate(mt,5,qbar[ohel2].particle(),
qbar[ohel2],g2[ihel2]);
diag[0]=_qqgvertex->evaluate(mt,inters,q[ohel1],g1[ihel1]);
//second t-channel diagram
inters =_qqgvertex->evaluate(mt,5,qbar[ohel2].particle(),
qbar[ohel2],g1[ihel1]);
diag[1]=_qqgvertex->evaluate(mt,inters,q[ohel1],g2[ihel2]);
// s-channel diagram
diag[2]=_qqgvertex->evaluate(mt,qbar[ohel2],q[ohel1],interv);
// colour flows
flow[0]=diag[0]+diag[2];
flow[1]=diag[1]-diag[2];
// sums
for(unsigned int ix=0;ix<3;++ix) sumdiag[ix] += norm(diag[ix]);
for(unsigned int ix=0;ix<2;++ix) sumflow[ix] += norm(flow[ix]);
// total
output +=real(flow[0]*conj(flow[0])+flow[1]*conj(flow[1])
-0.25*flow[0]*conj(flow[1]));
// store the me if needed
if(iflow!=0) _me(2*ihel1,2*ihel2,ohel1,ohel2)=flow[iflow-1];
}
}
}
}
// test code vs me from ESW
//Energy2 u(uHat()),t(tHat()),s(sHat());
//double alphas(4.*pi*SM().alphaS(mt));
//cerr << "testing matrix element "
// << 48.*(1./6./u/t-3./8./s/s)*(t*t+u*u)*sqr(alphas)/output << endl;
// select a colour flow
_flow=1+UseRandom::rnd2(sumflow[0],sumflow[1]);
// select a diagram ensuring it is one of those in the selected colour flow
sumdiag[_flow%2]=0.;
_diagram=4+UseRandom::rnd3(sumdiag[0],sumdiag[1],sumdiag[2]);
// final part of colour and spin factors
return output/48.;
}
double MEQCD2to2::qqbar2ggME(vector<SpinorWaveFunction> & q,
vector<SpinorBarWaveFunction> & qbar,
vector<VectorWaveFunction> &g1,
vector<VectorWaveFunction> &g2,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
// matrix element to be stored
if(iflow!=0) _me.reset(ProductionMatrixElement(PDT::Spin1Half,PDT::Spin1Half,
PDT::Spin1,PDT::Spin1));
// calculate the matrix element
double output(0.),sumdiag[3]={0.,0.,0.},sumflow[2]={0.,0.};
Complex diag[3],flow[2];
VectorWaveFunction interv;
SpinorWaveFunction inters;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
interv=_qqgvertex->evaluate(mt,5,_gluon,q[ihel1],qbar[ihel2]);
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
// first t-channel diagram
inters=_qqgvertex->evaluate(mt,5,q[ihel1].particle()->CC(),
q[ihel1],g1[ohel1]);
diag[0]=_qqgvertex->evaluate(mt,inters,qbar[ihel2],g2[ohel2]);
// second t-channel diagram
inters=_qqgvertex->evaluate(mt,5,q[ihel1].particle()->CC(),
q[ihel1],g2[ohel2]);
diag[1]=_qqgvertex->evaluate(mt,inters,qbar[ihel2],g1[ohel1]);
// s-channel diagram
diag[2]=_gggvertex->evaluate(mt,g1[ohel1],g2[ohel2],interv);
// colour flows
flow[0]=diag[0]-diag[2];
flow[1]=diag[1]+diag[2];
// sums
for(unsigned int ix=0;ix<3;++ix) sumdiag[ix] += norm(diag[ix]);
for(unsigned int ix=0;ix<2;++ix) sumflow[ix] += norm(flow[ix]);
// total
output +=real(flow[0]*conj(flow[0])+flow[1]*conj(flow[1])
-0.25*flow[0]*conj(flow[1]));
// store the me if needed
if(iflow!=0) _me(ihel1,ihel2,2*ohel1,2*ohel2)=flow[iflow-1];
}
}
}
}
// test code vs me from ESW
//Energy2 u(uHat()),t(tHat()),s(sHat());
//double alphas(4.*pi*SM().alphaS(mt));
//cerr << "testing matrix element "
// << 27./2.*0.5*(32./27./u/t-8./3./s/s)*(t*t+u*u)*sqr(alphas)/output << endl;
//select a colour flow
_flow=1+UseRandom::rnd2(sumflow[0],sumflow[1]);
// select a diagram ensuring it is one of those in the selected colour flow
sumdiag[_flow%2]=0.;
_diagram=7+UseRandom::rnd3(sumdiag[0],sumdiag[1],sumdiag[2]);
// final part of colour and spin factors
return 2.*output/27.;
}
double MEQCD2to2::qg2qgME(vector<SpinorWaveFunction> & qin,
vector<VectorWaveFunction> &g2,
vector<SpinorBarWaveFunction> & qout,
vector<VectorWaveFunction> &g4,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
// matrix element to be stored
if(iflow!=0) _me.reset(ProductionMatrixElement(PDT::Spin1Half,PDT::Spin1,
PDT::Spin1Half,PDT::Spin1));
// calculate the matrix element
double output(0.),sumdiag[3]={0.,0.,0.},sumflow[2]={0.,0.};
Complex diag[3],flow[2];
VectorWaveFunction interv;
SpinorWaveFunction inters,inters2;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
inters=_qqgvertex->evaluate(mt,5,qin[ihel1].particle()->CC(),
qin[ihel1],g2[ihel2]);
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
// s-channel diagram
diag[0]=_qqgvertex->evaluate(mt,inters,qout[ohel1],g4[ohel2]);
// first t-channel
inters2=_qqgvertex->evaluate(mt,5,qin[ihel1].particle()->CC(),
qin[ihel1],g4[ohel2]);
diag[1]=_qqgvertex->evaluate(mt,inters2,qout[ohel1],g2[ihel2]);
// second t-channel
interv=_qqgvertex->evaluate(mt,5,_gluon,qin[ihel1],qout[ohel1]);
diag[2]=_gggvertex->evaluate(mt,g2[ihel2],g4[ohel2],interv);
// colour flows
flow[0]=diag[0]-diag[2];
flow[1]=diag[1]+diag[2];
// sums
for(unsigned int ix=0;ix<3;++ix) sumdiag[ix] += norm(diag[ix]);
for(unsigned int ix=0;ix<2;++ix) sumflow[ix] += norm(flow[ix]);
// total
output +=real(flow[0]*conj(flow[0])+flow[1]*conj(flow[1])
-0.25*flow[0]*conj(flow[1]));
// store the me if needed
if(iflow!=0) _me(ihel1,2*ihel2,ohel1,2*ohel2)=flow[iflow-1];
}
}
}
}
// test code vs me from ESW
//Energy2 u(uHat()),t(tHat()),s(sHat());
//double alphas(4.*pi*SM().alphaS(mt));
//cerr << "testing matrix element "
// << 18./output*(-4./9./s/u+1./t/t)*(s*s+u*u)*sqr(alphas) << endl;
//select a colour flow
_flow=1+UseRandom::rnd2(sumflow[0],sumflow[1]);
// select a diagram ensuring it is one of those in the selected colour flow
sumdiag[_flow%2]=0.;
_diagram=10+UseRandom::rnd3(sumdiag[0],sumdiag[1],sumdiag[2]);
// final part of colour and spin factors
return output/18.;
}
double MEQCD2to2::gg2ggME(vector<VectorWaveFunction> &g1,vector<VectorWaveFunction> &g2,
vector<VectorWaveFunction> &g3,vector<VectorWaveFunction> &g4,
unsigned int iflow) const {
// colour factors for different flows
static const double c1 = 4.*( sqr(9.)/8.-3.*9./8.+1.-0.75/9.);
static const double c2 = 4.*(-0.25*9. +1.-0.75/9.);
// scale
Energy2 mt(scale());
// // matrix element to be stored
if(iflow!=0) _me.reset(ProductionMatrixElement(PDT::Spin1,PDT::Spin1,
PDT::Spin1,PDT::Spin1));
// calculate the matrix element
double output(0.),sumdiag[3]={0.,0.,0.},sumflow[3]={0.,0.,0.};
Complex diag[3],flow[3];
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
// s-channel diagram
diag[0]=_ggggvertex->evaluate(mt,1,g3[ohel1],g1[ihel1],
g4[ohel2],g2[ihel2]);
// t-channel
diag[1]=_ggggvertex->evaluate(mt,1,g1[ihel1],g2[ihel2],
g3[ohel1],g4[ohel2]);
// u-channel
diag[2]=_ggggvertex->evaluate(mt,1,g2[ihel2],g1[ihel1],
g3[ohel1],g4[ohel2]);
// colour flows
flow[0] = diag[0]-diag[2];
flow[1] = -diag[0]-diag[1];
flow[2] = diag[1]+diag[2];
// sums
for(unsigned int ix=0;ix<3;++ix) {
sumdiag[ix] += norm(diag[ix]);
sumflow[ix] += norm(flow[ix]);
}
// total
output += c1*(norm(flow[0])+norm(flow[1])+norm(flow[2]))
+2.*c2*real(flow[0]*conj(flow[1])+flow[0]*conj(flow[2])+
flow[1]*conj(flow[2]));
// store the me if needed
if(iflow!=0) _me(2*ihel1,2*ihel2,2*ohel1,2*ohel2)=flow[iflow-1];
}
}
}
}
// spin, colour and identical particle factorsxs
output /= 4.*64.*2.;
// test code vs me from ESW
// Energy2 u(uHat()),t(tHat()),s(sHat());
// using Constants::pi;
// double alphas(4.*pi*SM().alphaS(mt));
// cerr << "testing matrix element "
// << 1./output*9./4.*(3.-t*u/s/s-s*u/t/t-s*t/u/u)*sqr(alphas) << endl;
// select a colour flow
_flow=1+UseRandom::rnd3(sumflow[0],sumflow[1],sumflow[2]);
// and diagram
if(_flow==1) _diagram = 1+2*UseRandom::rnd2(sumdiag[0],sumdiag[2]);
else if(_flow==2) _diagram = 1+ UseRandom::rnd2(sumdiag[0],sumdiag[1]);
else if(_flow==3) _diagram = 2+ UseRandom::rnd2(sumdiag[1],sumdiag[2]);
// final part of colour and spin factors
return output;
}
double MEQCD2to2::qbarg2qbargME(vector<SpinorBarWaveFunction> & qin,
vector<VectorWaveFunction> &g2,
vector<SpinorWaveFunction> & qout,
vector<VectorWaveFunction> &g4,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
// matrix element to be stored
if(iflow!=0) _me.reset(ProductionMatrixElement(PDT::Spin1Half,PDT::Spin1,
PDT::Spin1Half,PDT::Spin1));
// calculate the matrix element
double output(0.),sumdiag[3]={0.,0.,0.},sumflow[2]={0.,0.};
Complex diag[3],flow[2];
VectorWaveFunction interv;
SpinorBarWaveFunction inters,inters2;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
inters=_qqgvertex->evaluate(mt,5,qin[ihel1].particle()->CC(),
qin[ihel1],g2[ihel2]);
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
// s-channel diagram
diag[0]=_qqgvertex->evaluate(mt,qout[ohel1],inters,g4[ohel2]);
// first t-channel
inters2=_qqgvertex->evaluate(mt,5,qin[ihel1].particle()->CC(),
qin[ihel1],g4[ohel2]);
diag[1]=_qqgvertex->evaluate(mt,qout[ohel1],inters2,g2[ihel2]);
// second t-channel
interv=_qqgvertex->evaluate(mt,5,_gluon,qout[ohel1],qin[ihel1]);
diag[2]=_gggvertex->evaluate(mt,g2[ihel2],g4[ohel2],interv);
// colour flows
flow[0]=diag[0]+diag[2];
flow[1]=diag[1]-diag[2];
// sums
for(unsigned int ix=0;ix<3;++ix) sumdiag[ix] += norm(diag[ix]);
for(unsigned int ix=0;ix<2;++ix) sumflow[ix] += norm(flow[ix]);
// total
output +=real(flow[0]*conj(flow[0])+flow[1]*conj(flow[1])
-0.25*flow[0]*conj(flow[1]));
// store the me if needed
if(iflow!=0) _me(ihel1,2*ihel2,ohel1,2*ohel2)=flow[iflow-1];
}
}
}
}
// test code vs me from ESW
//Energy2 u(uHat()),t(tHat()),s(sHat());
//double alphas(4.*pi*SM().alphaS(mt));
//cerr << "testing matrix element "
// << 18./output*(-4./9./s/u+1./t/t)*(s*s+u*u)*sqr(alphas) << endl;
//select a colour flow
_flow=1+UseRandom::rnd2(sumflow[0],sumflow[1]);
// select a diagram ensuring it is one of those in the selected colour flow
sumdiag[_flow%2]=0.;
_diagram=13+UseRandom::rnd3(sumdiag[0],sumdiag[1],sumdiag[2]);
// final part of colour and spin factors
return output/18.;
}
double MEQCD2to2::qq2qqME(vector<SpinorWaveFunction> & q1,
vector<SpinorWaveFunction> & q2,
vector<SpinorBarWaveFunction> & q3,
vector<SpinorBarWaveFunction> & q4,
unsigned int iflow) const {
// identify special case of identical quarks
bool identical(q1[0].id()==q2[0].id());
// scale
Energy2 mt(scale());
// matrix element to be stored
if(iflow!=0) _me.reset(ProductionMatrixElement(PDT::Spin1Half,PDT::Spin1Half,
PDT::Spin1Half,PDT::Spin1Half));
// calculate the matrix element
double output(0.),sumdiag[2]={0.,0.};
Complex diag[2];
VectorWaveFunction interv;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
// first diagram
interv = _qqgvertex->evaluate(mt,5,_gluon,q1[ihel1],q3[ohel1]);
diag[0] = _qqgvertex->evaluate(mt,q2[ihel2],q4[ohel2],interv);
// second diagram if identical
if(identical) {
interv = _qqgvertex->evaluate(mt,5,_gluon,q1[ihel1],q4[ohel2]);
diag[1]=_qqgvertex->evaluate(mt,q2[ihel2],q3[ohel1],interv);
}
else diag[1]=0.;
// sum of diagrams
for(unsigned int ix=0;ix<2;++ix) sumdiag[ix] += norm(diag[ix]);
// total
output +=real(diag[0]*conj(diag[0])+diag[1]*conj(diag[1])
+2./3.*diag[0]*conj(diag[1]));
// store the me if needed
if(iflow!=0) _me(ihel1,ihel2,ohel1,ohel2)=diag[iflow-1];
}
}
}
}
// identical particle symmetry factor if needed
if(identical) output*=0.5;
// test code vs me from ESW
//Energy2 u(uHat()),t(tHat()),s(sHat());
//double alphas(4.*pi*SM().alphaS(mt));
//if(identical)
// {cerr << "testing matrix element A "
// << 18./output*0.5*(4./9.*((s*s+u*u)/t/t+(s*s+t*t)/u/u)
// -8./27.*s*s/u/t)*sqr(alphas) << endl;}
//else
// {cerr << "testing matrix element B "
// << 18./output*(4./9.*(s*s+u*u)/t/t)*sqr(alphas) << endl;}
//select a colour flow
_flow=1+UseRandom::rnd2(sumdiag[0],sumdiag[1]);
// select a diagram ensuring it is one of those in the selected colour flow
sumdiag[_flow%2]=0.;
_diagram=16+UseRandom::rnd2(sumdiag[0],sumdiag[1]);
// final part of colour and spin factors
return output/18.;
}
double MEQCD2to2::qbarqbar2qbarqbarME(vector<SpinorBarWaveFunction> & q1,
vector<SpinorBarWaveFunction> & q2,
vector<SpinorWaveFunction> & q3,
vector<SpinorWaveFunction> & q4,
unsigned int iflow) const {
// identify special case of identical quarks
bool identical(q1[0].id()==q2[0].id());
// scale
Energy2 mt(scale());
// matrix element to be stored
if(iflow!=0)
{_me.reset(ProductionMatrixElement(PDT::Spin1Half,PDT::Spin1Half,
PDT::Spin1Half,PDT::Spin1Half));}
// calculate the matrix element
double output(0.),sumdiag[2]={0.,0.};
Complex diag[2];
VectorWaveFunction interv;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
// first diagram
interv = _qqgvertex->evaluate(mt,5,_gluon,q3[ohel1],q1[ihel1]);
diag[0] = _qqgvertex->evaluate(mt,q4[ohel2],q2[ihel2],interv);
// second diagram if identical
if(identical) {
interv = _qqgvertex->evaluate(mt,5,_gluon,q4[ohel2],q1[ihel1]);
diag[1]=_qqgvertex->evaluate(mt,q3[ohel1],q2[ihel2],interv);
}
else diag[1]=0.;
// sum of diagrams
for(unsigned int ix=0;ix<2;++ix) sumdiag[ix] += norm(diag[ix]);
// total
output +=real(diag[0]*conj(diag[0])+diag[1]*conj(diag[1])
+2./3.*diag[0]*conj(diag[1]));
// store the me if needed
if(iflow!=0) _me(ihel1,ihel2,ohel1,ohel2)=diag[iflow-1];
}
}
}
}
// identical particle symmetry factor if needed
if(identical){output*=0.5;}
// test code vs me from ESW
// Energy2 u(uHat()),t(tHat()),s(sHat());
// double alphas(4.*pi*SM().alphaS(mt));
// if(identical)
// {cerr << "testing matrix element A "
// << 18./output*0.5*(4./9.*((s*s+u*u)/t/t+(s*s+t*t)/u/u)
// -8./27.*s*s/u/t)*sqr(alphas) << endl;}
// else
// {cerr << "testing matrix element B "
// << 18./output*(4./9.*(s*s+u*u)/t/t)*sqr(alphas) << endl;}
//select a colour flow
_flow=1+UseRandom::rnd2(sumdiag[0],sumdiag[1]);
// select a diagram ensuring it is one of those in the selected colour flow
sumdiag[_flow%2]=0.;
_diagram=18+UseRandom::rnd2(sumdiag[0],sumdiag[1]);
// final part of colour and spin factors
return output/18.;
}
double MEQCD2to2::qqbar2qqbarME(vector<SpinorWaveFunction> & q1,
vector<SpinorBarWaveFunction> & q2,
vector<SpinorBarWaveFunction> & q3,
vector<SpinorWaveFunction> & q4,
unsigned int iflow) const {
// type of process
bool diagon[2]={q1[0].id()== -q2[0].id(),
q1[0].id()== -q3[0].id()};
// scale
Energy2 mt(scale());
// matrix element to be stored
if(iflow!=0) _me.reset(ProductionMatrixElement(PDT::Spin1Half,PDT::Spin1Half,
PDT::Spin1Half,PDT::Spin1Half));
// calculate the matrix element
double output(0.),sumdiag[2]={0.,0.};
Complex diag[2];
VectorWaveFunction interv;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
// first diagram
if(diagon[0]) {
interv = _qqgvertex->evaluate(mt,5,_gluon,q1[ihel1],q2[ihel2]);
diag[0] = _qqgvertex->evaluate(mt,q4[ohel2],q3[ohel1],interv);
}
else diag[0]=0.;
// second diagram
if(diagon[1]) {
interv = _qqgvertex->evaluate(mt,5,_gluon,q1[ihel1],q3[ohel1]);
diag[1]=_qqgvertex->evaluate(mt,q4[ohel2],q2[ihel2],interv);
}
else diag[1]=0.;
// sum of diagrams
for(unsigned int ix=0;ix<2;++ix) sumdiag[ix] += norm(diag[ix]);
// total
output +=real(diag[0]*conj(diag[0])+diag[1]*conj(diag[1])
+2./3.*diag[0]*conj(diag[1]));
// store the me if needed
if(iflow!=0){_me(ihel1,ihel2,ohel1,ohel2)=diag[iflow-1];}
}
}
}
}
// test code vs me from ESW
// Energy2 u(uHat()),t(tHat()),s(sHat());
// double alphas(4.*pi*SM().alphaS(mt));
// if(diagon[0]&&diagon[1]) {
// cerr << "testing matrix element A "
// << q1[0].id() << " " << q2[0].id() << " -> "
// << q3[0].id() << " " << q4[0].id() << " "
// << 18./output*0.5*(4./9.*((s*s+u*u)/t/t+(u*u+t*t)/s/s)
// -8./27.*u*u/s/t)*sqr(alphas) << endl;
// }
// else if(diagon[0]) {
// cerr << "testing matrix element B "
// << q1[0].id() << " " << q2[0].id() << " -> "
// << q3[0].id() << " " << q4[0].id() << " "
// << 18./output*(4./9.*(t*t+u*u)/s/s)*sqr(alphas) << endl;
// }
// else if(diagon[1]) {
// cerr << "testing matrix element C "
// << q1[0].id() << " " << q2[0].id() << " -> "
// << q3[0].id() << " " << q4[0].id() << " "
// << 18./output*(4./9.*(s*s+u*u)/t/t)*sqr(alphas) << endl;
// }
//select a colour flow
_flow=1+UseRandom::rnd2(sumdiag[0],sumdiag[1]);
// select a diagram ensuring it is one of those in the selected colour flow
sumdiag[_flow%2]=0.;
_diagram=20+UseRandom::rnd2(sumdiag[0],sumdiag[1]);
// final part of colour and spin factors
return output/18.;
}
void MEQCD2to2::getDiagrams() const {
// gg-> gg subprocess
if(_process==0||_process==1) {
// s-channel
add(new_ptr((Tree2toNDiagram(2),_gluon,_gluon, 1, _gluon,
3,_gluon, 3, _gluon, -1)));
// first t-channel
add(new_ptr((Tree2toNDiagram(3),_gluon,_gluon,_gluon,
1,_gluon, 2,_gluon,-2)));
// second t-channel
add(new_ptr((Tree2toNDiagram(3),_gluon,_gluon,_gluon,
2,_gluon, 1,_gluon,-3)));
}
// processes involving one quark line
for(unsigned int ix=0;ix<_maxflavour;++ix) {
// gg -> q qbar subprocesses
if(_process==0||_process==2) {
// first t-channel
add(new_ptr((Tree2toNDiagram(3),_gluon,_antiquark[ix],_gluon,
1,_quark[ix], 2,_antiquark[ix],-4)));
// interchange
add(new_ptr((Tree2toNDiagram(3),_gluon,_antiquark[ix],_gluon,
2,_quark[ix], 1,_antiquark[ix],-5)));
// s-channel
add(new_ptr((Tree2toNDiagram(2),_gluon,_gluon, 1, _gluon,
3,_quark[ix], 3, _antiquark[ix], -6)));
}
// q qbar -> g g subprocesses
if(_process==0||_process==3) {
// first t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[ix],_antiquark[ix],_antiquark[ix],
1,_gluon, 2,_gluon,-7)));
// second t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[ix],_antiquark[ix],_antiquark[ix],
2,_gluon, 1,_gluon,-8)));
// s-channel
add(new_ptr((Tree2toNDiagram(2),_quark[ix], _antiquark[ix],
1, _gluon, 3, _gluon, 3, _gluon,-9)));
}
// q g -> q g subprocesses
if(_process==0||_process==4) {
// s-channel
add(new_ptr((Tree2toNDiagram(2),_quark[ix], _gluon,
1, _quark[ix], 3, _quark[ix], 3, _gluon,-10)));
// quark t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[ix],_quark[ix],_gluon,
2,_quark[ix],1,_gluon,-11)));
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[ix],_gluon,_gluon,
1,_quark[ix],2,_gluon,-12)));
}
// qbar g -> qbar g subprocesses
if(_process==0||_process==5) {
// s-channel
add(new_ptr((Tree2toNDiagram(2),_antiquark[ix], _gluon,
1, _antiquark[ix], 3, _antiquark[ix], 3, _gluon,-13)));
// quark t-channel
add(new_ptr((Tree2toNDiagram(3),_antiquark[ix],_antiquark[ix],_gluon,
2,_antiquark[ix],1,_gluon,-14)));
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_antiquark[ix],_gluon,_gluon,
1,_antiquark[ix],2,_gluon,-15)));
}
// processes involving two quark lines
for(unsigned int iy=0;iy<_maxflavour;++iy) {
// q q -> q q subprocesses
if(_process==0||_process==6) {
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[ix],_gluon,_quark[iy],
1,_quark[ix],2,_quark[iy],-16)));
// exchange for identical quarks
if(ix==iy)
add(new_ptr((Tree2toNDiagram(3),_quark[ix],_gluon,_quark[iy],
2,_quark[ix],1,_quark[iy],-17)));
}
// qbar qbar -> qbar qbar subprocesses
if(_process==0||_process==7) {
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_antiquark[ix],_gluon,_antiquark[iy],
1,_antiquark[ix],2,_antiquark[iy],-18)));
// exchange for identical quarks
if(ix==iy)
add(new_ptr((Tree2toNDiagram(3),_antiquark[ix],_gluon,_antiquark[iy],
2,_antiquark[ix],1,_antiquark[iy],-19)));
}
// q qbar -> q qbar
if(_process==0||_process==8) {
// gluon s-channel
add(new_ptr((Tree2toNDiagram(2),_quark[ix], _antiquark[ix],
1, _gluon, 3, _quark[iy], 3, _antiquark[iy],-20)));
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[ix],_gluon,_antiquark[iy],
1,_quark[ix],2,_antiquark[iy],-21)));
}
}
}
}
Selector<const ColourLines *>
MEQCD2to2::colourGeometries(tcDiagPtr diag) const {
// colour lines for gg to gg
static const ColourLines cgggg[12]={ColourLines("1 -2, -1 -3 -5, 5 -4, 2 3 4"),// A_2 s
ColourLines("-1 2, 1 3 5, -5 4, -2 -3 -4"),// A_1 s
ColourLines("1 5, -1 -2 3, -3 -4, -5 2 4"),// A_1 u
ColourLines("-1 -5, 1 2 -3, 3 4, 5 -2 -4"),// A_2 u
ColourLines("1 -2, -1 -3 -4, 4 -5, 2 3 5"),// B_2 s
ColourLines("-1 2, 1 3 4, -4 5, -2 -3 -5"),// B_1 s
ColourLines("1 4, -1 -2 3, -3 -5, -4 2 5"),// B_1 t
ColourLines("-1 -4, 1 2 -3, 3 5, 4 -2 -5"),// B_2 t
ColourLines("1 4, -1 -2 -5, 3 5, -3 2 -4"),// C_1 t
ColourLines("-1 -4, 1 2 5, -3 -5, 3 -2 4"),// C_2 t
ColourLines("1 5, -1 -2 -4, 3 4, -3 2 -5"),// C_1 u
ColourLines("-1 -5, 1 2 4, -3 -4, 3 -2 5") // C_2 u
};
// colour lines for gg to q qbar
static const ColourLines cggqq[4]={ColourLines("1 4, -1 -2 3, -3 -5"),
ColourLines("3 4, -3 -2 1, -1 -5"),
ColourLines("2 -1, 1 3 4, -2 -3 -5"),
ColourLines("1 -2, -1 -3 -5, 2 3 4")};
// colour lines for q qbar to gg
static const ColourLines cqqgg[4]={ColourLines("1 4, -4 -2 5, -3 -5"),
ColourLines("1 5, -3 -4, 4 -2 -5"),
ColourLines("1 3 4, -4 5, -2 -3 -5"),
ColourLines("1 3 5, -5 4, -2 -3 -4")};
// colour lines for q g to q g
static const ColourLines cqgqg[4]={ColourLines("1 -2, 2 3 5, 4 -5"),
ColourLines("1 5, 3 4,-3 2 -5 "),
ColourLines("1 2 -3, 3 5, -5 -2 4"),
ColourLines("1 -2 5,3 2 4,-3 -5")};
// colour lines for qbar g -> qbar g
static const ColourLines cqbgqbg[4]={ColourLines("-1 2, -2 -3 -5, -4 5"),
ColourLines("-1 -5, -3 -4, 3 -2 5"),
ColourLines("-1 -2 3, -3 -5, 5 2 -4"),
ColourLines("-1 2 -5,-3 -2 -4, 3 5")};
// colour lines for q q -> q q
static const ColourLines cqqqq[2]={ColourLines("1 2 5,3 -2 4"),
ColourLines("1 2 4,3 -2 5")};
// colour lines for qbar qbar -> qbar qbar
static const ColourLines cqbqbqbqb[2]={ColourLines("-1 -2 -5,-3 2 -4"),
ColourLines("-1 -2 -4,-3 2 -5")};
// colour lines for q qbar -> q qbar
static const ColourLines cqqbqqb[2]={ColourLines("1 3 4,-2 -3 -5"),
ColourLines("1 2 -3,4 -2 -5")};
// select the colour flow (as all ready picked just insert answer)
Selector<const ColourLines *> sel;
switch(abs(diag->id())) {
// gg -> gg subprocess
case 1:
if(_flow==1) {
sel.insert(0.5, &cgggg[0]);
sel.insert(0.5, &cgggg[1]);
}
else {
sel.insert(0.5, &cgggg[4]);
sel.insert(0.5, &cgggg[5]);
}
break;
case 2:
if(_flow==2) {
sel.insert(0.5, &cgggg[6]);
sel.insert(0.5, &cgggg[7]);
}
else {
sel.insert(0.5, &cgggg[8]);
sel.insert(0.5, &cgggg[9]);
}
break;
case 3:
if(_flow==1) {
sel.insert(0.5, &cgggg[2]);
sel.insert(0.5, &cgggg[3]);
}
else {
sel.insert(0.5, &cgggg[10]);
sel.insert(0.5, &cgggg[11]);
}
break;
// gg -> q qbar subprocess
case 4: case 5:
sel.insert(1.0, &cggqq[abs(diag->id())-4]);
break;
case 6:
sel.insert(1.0, &cggqq[1+_flow]);
break;
// q qbar -> gg subprocess
case 7: case 8:
sel.insert(1.0, &cqqgg[abs(diag->id())-7]);
break;
case 9:
sel.insert(1.0, &cqqgg[1+_flow]);
break;
// q g -> q g subprocess
case 10: case 11:
sel.insert(1.0, &cqgqg[abs(diag->id())-10]);
break;
case 12:
sel.insert(1.0, &cqgqg[1+_flow]);
break;
// q g -> q g subprocess
case 13: case 14:
sel.insert(1.0, &cqbgqbg[abs(diag->id())-13]);
break;
case 15:
sel.insert(1.0, &cqbgqbg[1+_flow]);
break;
// q q -> q q subprocess
case 16: case 17:
sel.insert(1.0, &cqqqq[abs(diag->id())-16]);
break;
// qbar qbar -> qbar qbar subprocess
case 18: case 19:
sel.insert(1.0, &cqbqbqbqb[abs(diag->id())-18]);
break;
// q qbar -> q qbar subprocess
case 20: case 21:
sel.insert(1.0, &cqqbqqb[abs(diag->id())-20]);
break;
}
return sel;
}
double MEQCD2to2::me2() const {
// total matrix element
double me(0.);
// gg initiated processes
if(mePartonData()[0]->id()==ParticleID::g&&mePartonData()[1]->id()==ParticleID::g) {
// gg -> gg
if(mePartonData()[2]->id()==ParticleID::g) {
VectorWaveFunction g1w(meMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction g2w(meMomenta()[1],mePartonData()[1],incoming);
VectorWaveFunction g3w(meMomenta()[2],mePartonData()[2],outgoing);
VectorWaveFunction g4w(meMomenta()[3],mePartonData()[3],outgoing);
vector<VectorWaveFunction> g1,g2,g3,g4;
for(unsigned int ix=0;ix<2;++ix) {
g1w.reset(2*ix);g1.push_back(g1w);
g2w.reset(2*ix);g2.push_back(g2w);
g3w.reset(2*ix);g3.push_back(g3w);
g4w.reset(2*ix);g4.push_back(g4w);
}
// calculate the matrix element
me = gg2ggME(g1,g2,g3,g4,0);
}
// gg -> q qbar
else {
VectorWaveFunction g1w(meMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction g2w(meMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction qw(meMomenta()[2],mePartonData()[2],outgoing);
SpinorWaveFunction qbarw(meMomenta()[3],mePartonData()[3],outgoing);
vector<VectorWaveFunction> g1,g2;
vector<SpinorBarWaveFunction> q;
vector<SpinorWaveFunction> qbar;
for(unsigned int ix=0;ix<2;++ix) {
g1w.reset(2*ix);g1.push_back(g1w);
g2w.reset(2*ix);g2.push_back(g2w);
qw.reset(ix);q.push_back(qw);
qbarw.reset(ix);qbar.push_back(qbarw);
}
// calculate the matrix element
me=gg2qqbarME(g1,g2,q,qbar,0);
}
}
// quark first processes
else if(mePartonData()[0]->id()>0) {
// q g -> q g
if(mePartonData()[1]->id()==ParticleID::g) {
SpinorWaveFunction qinw(meMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction g2w(meMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction qoutw(meMomenta()[2],mePartonData()[2],outgoing);
VectorWaveFunction g4w(meMomenta()[3],mePartonData()[3],outgoing);
vector<VectorWaveFunction> g2,g4;
vector<SpinorWaveFunction> qin;
vector<SpinorBarWaveFunction> qout;
for(unsigned int ix=0;ix<2;++ix) {
qinw.reset(ix);qin.push_back(qinw);
g2w.reset(2*ix);g2.push_back(g2w);
qoutw.reset(ix);qout.push_back(qoutw);
g4w.reset(2*ix);g4.push_back(g4w);
}
// calculate the matrix element
me = qg2qgME(qin,g2,qout,g4,0);
}
else if(mePartonData()[1]->id()<0) {
// q qbar initiated processes( q qbar -> gg)
if(mePartonData()[2]->id()==ParticleID::g) {
SpinorWaveFunction qw(meMomenta()[0],mePartonData()[0],incoming);
SpinorBarWaveFunction qbarw(meMomenta()[1],mePartonData()[1],incoming);
VectorWaveFunction g1w(meMomenta()[2],mePartonData()[2],outgoing);
VectorWaveFunction g2w(meMomenta()[3],mePartonData()[3],outgoing);
vector<VectorWaveFunction> g1,g2;
vector<SpinorWaveFunction> q;
vector<SpinorBarWaveFunction> qbar;
for(unsigned int ix=0;ix<2;++ix) {
qw.reset(ix);q.push_back(qw);
qbarw.reset(ix);qbar.push_back(qbarw);
g1w.reset(2*ix);g1.push_back(g1w);
g2w.reset(2*ix);g2.push_back(g2w);
}
// calculate the matrix element
me = qqbar2ggME(q,qbar,g1,g2,0);
}
// q qbar to q qbar
else {
SpinorWaveFunction q1w(meMomenta()[0],mePartonData()[0],incoming);
SpinorBarWaveFunction q2w(meMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction q3w(meMomenta()[2],mePartonData()[2],outgoing);
SpinorWaveFunction q4w(meMomenta()[3],mePartonData()[3],outgoing);
vector<SpinorWaveFunction> q1,q4;
vector<SpinorBarWaveFunction> q2,q3;
for(unsigned int ix=0;ix<2;++ix) {
q1w.reset(ix);q1.push_back(q1w);
q2w.reset(ix);q2.push_back(q2w);
q3w.reset(ix);q3.push_back(q3w);
q4w.reset(ix);q4.push_back(q4w);
}
// calculate the matrix element
me = qqbar2qqbarME(q1,q2,q3,q4,0);
}
}
// q q -> q q
else if(mePartonData()[1]->id()>0) {
SpinorWaveFunction q1w(meMomenta()[0],mePartonData()[0],incoming);
SpinorWaveFunction q2w(meMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction q3w(meMomenta()[2],mePartonData()[2],outgoing);
SpinorBarWaveFunction q4w(meMomenta()[3],mePartonData()[3],outgoing);
vector<SpinorWaveFunction> q1,q2;
vector<SpinorBarWaveFunction> q3,q4;
for(unsigned int ix=0;ix<2;++ix) {
q1w.reset(ix);q1.push_back(q1w);
q2w.reset(ix);q2.push_back(q2w);
q3w.reset(ix);q3.push_back(q3w);
q4w.reset(ix);q4.push_back(q4w);
}
// calculate the matrix element
me = qq2qqME(q1,q2,q3,q4,0);
}
}
// antiquark first processes
else if(mePartonData()[0]->id()<0) {
// qbar g -> qbar g
if(mePartonData()[1]->id()==ParticleID::g) {
SpinorBarWaveFunction qinw(meMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction g2w(meMomenta()[1],mePartonData()[1],incoming);
SpinorWaveFunction qoutw(meMomenta()[2],mePartonData()[2],outgoing);
VectorWaveFunction g4w(meMomenta()[3],mePartonData()[3],outgoing);
vector<VectorWaveFunction> g2,g4;
vector<SpinorBarWaveFunction> qin;
vector<SpinorWaveFunction> qout;
for(unsigned int ix=0;ix<2;++ix) {
qinw.reset(ix);qin.push_back(qinw);
g2w.reset(2*ix);g2.push_back(g2w);
qoutw.reset(ix);qout.push_back(qoutw);
g4w.reset(2*ix);g4.push_back(g4w);
}
// calculate the matrix element
me = qbarg2qbargME(qin,g2,qout,g4,0);
}
// qbar qbar -> qbar qbar
else if(mePartonData()[1]->id()<0) {
SpinorBarWaveFunction q1w(meMomenta()[0],mePartonData()[0],incoming);
SpinorBarWaveFunction q2w(meMomenta()[1],mePartonData()[1],incoming);
SpinorWaveFunction q3w(meMomenta()[2],mePartonData()[2],outgoing);
SpinorWaveFunction q4w(meMomenta()[3],mePartonData()[3],outgoing);
vector<SpinorBarWaveFunction> q1,q2;
vector<SpinorWaveFunction> q3,q4;
for(unsigned int ix=0;ix<2;++ix) {
q1w.reset(ix);q1.push_back(q1w);
q2w.reset(ix);q2.push_back(q2w);
q3w.reset(ix);q3.push_back(q3w);
q4w.reset(ix);q4.push_back(q4w);
}
// calculate the matrix element
me = qbarqbar2qbarqbarME(q1,q2,q3,q4,0);
}
}
else throw Exception() << "Unknown process in MEQCD2to2::me2()"
<< Exception::abortnow;
// return the answer
return me;
}
void MEQCD2to2::constructVertex(tSubProPtr sub) {
SpinfoPtr spin[4];
// extract the particles in the hard process
ParticleVector hard;
hard.push_back(sub->incoming().first);hard.push_back(sub->incoming().second);
hard.push_back(sub->outgoing()[0]);hard.push_back(sub->outgoing()[1]);
// order of particles
unsigned int order[4]={0,1,2,3};
// identify the process and calculate the matrix element
if(hard[0]->id()==ParticleID::g&&hard[1]->id()==ParticleID::g) {
// gg -> gg
if(hard[2]->id()==ParticleID::g) {
vector<VectorWaveFunction> g1,g2,g3,g4;
VectorWaveFunction(g1,hard[0],incoming,false,true,true);
VectorWaveFunction(g2,hard[1],incoming,false,true,true);
VectorWaveFunction(g3,hard[2],outgoing,true ,true,true);
VectorWaveFunction(g4,hard[3],outgoing,true ,true,true);
g1[1]=g1[2];g2[1]=g2[2];g3[1]=g3[2];g4[1]=g4[2];
gg2ggME(g1,g2,g3,g4,_flow);
}
// gg -> q qbar
else {
if(hard[2]->id()<0) swap(order[2],order[3]);
vector<VectorWaveFunction> g1,g2;
vector<SpinorBarWaveFunction> q;
vector<SpinorWaveFunction> qbar;
VectorWaveFunction( g1,hard[ 0 ],incoming,false,true,true);
VectorWaveFunction( g2,hard[ 1 ],incoming,false,true,true);
SpinorBarWaveFunction(q ,hard[order[2]],outgoing,true ,true);
SpinorWaveFunction( qbar,hard[order[3]],outgoing,true ,true);
g1[1]=g1[2];g2[1]=g2[2];
gg2qqbarME(g1,g2,q,qbar,_flow);
}
}
else if(hard[0]->id()==ParticleID::g||hard[1]->id()==ParticleID::g) {
if(hard[0]->id()==ParticleID::g) swap(order[0],order[1]);
if(hard[2]->id()==ParticleID::g) swap(order[2],order[3]);
// q g -> q g
if(hard[order[0]]->id()>0) {
vector<VectorWaveFunction> g2,g4;
vector<SpinorWaveFunction> qin;
vector<SpinorBarWaveFunction> qout;
SpinorWaveFunction( qin,hard[order[0]],incoming,false,true);
VectorWaveFunction( g2,hard[order[1]],incoming,false,true,true);
SpinorBarWaveFunction(qout,hard[order[2]],outgoing,true ,true);
VectorWaveFunction( g4,hard[order[3]],outgoing,true ,true,true);
g2[1]=g2[2];g4[1]=g4[2];
qg2qgME(qin,g2,qout,g4,_flow);
}
// qbar g -> qbar g
else {
vector<VectorWaveFunction> g2,g4;
vector<SpinorBarWaveFunction> qin;
vector<SpinorWaveFunction> qout;
SpinorBarWaveFunction( qin,hard[order[0]],incoming,false,true);
VectorWaveFunction( g2,hard[order[1]],incoming,false,true,true);
SpinorWaveFunction( qout,hard[order[2]],outgoing,true ,true);
VectorWaveFunction( g4,hard[order[3]],outgoing,true ,true,true);
g2[1]=g2[2];g4[1]=g4[2];
qbarg2qbargME(qin,g2,qout,g4,_flow);
}
}
else if(hard[0]->id()>0||hard[1]->id()>0) {
if(hard[2]->id()==ParticleID::g) {
if(hard[0]->id()<0) swap(order[0],order[1]);
vector<SpinorBarWaveFunction> qbar;
vector<SpinorWaveFunction> q;
vector<VectorWaveFunction> g3,g4;
SpinorWaveFunction( q ,hard[order[0]],incoming,false,true);
SpinorBarWaveFunction(qbar,hard[order[1]],incoming,false,true);
VectorWaveFunction( g3,hard[ 2 ],outgoing,true ,true,true);
VectorWaveFunction( g4,hard[ 3 ],outgoing,true ,true,true);
g3[1]=g3[2];g4[1]=g4[2];
qqbar2ggME(q,qbar,g3,g4,_flow);
}
// q q -> q q
else if(hard[0]->id()>0&&hard[1]->id()>0) {
if(hard[2]->id()!=hard[0]->id()) swap(order[2],order[3]);
vector<SpinorWaveFunction> q1,q2;
vector<SpinorBarWaveFunction> q3,q4;
SpinorWaveFunction( q1,hard[order[0]],incoming,false,true);
SpinorWaveFunction( q2,hard[order[1]],incoming,false,true);
SpinorBarWaveFunction(q3,hard[order[2]],outgoing,true ,true);
SpinorBarWaveFunction(q4,hard[order[3]],outgoing,true ,true);
qq2qqME(q1,q2,q3,q4,_flow);
}
// q qbar -> q qbar
else {
if(hard[0]->id()<0) swap(order[0],order[1]);
if(hard[2]->id()<0) swap(order[2],order[3]);
vector<SpinorWaveFunction> q1,q4;
vector<SpinorBarWaveFunction> q2,q3;
SpinorWaveFunction( q1,hard[order[0]],incoming,false,true);
SpinorBarWaveFunction(q2,hard[order[1]],incoming,false,true);
SpinorBarWaveFunction(q3,hard[order[2]],outgoing,true ,true);
SpinorWaveFunction( q4,hard[order[3]],outgoing,true ,true);
qqbar2qqbarME(q1,q2,q3,q4,_flow);
}
}
else if (hard[0]->id()<0&&hard[1]->id()<0) {
if(hard[2]->id()!=hard[0]->id()) swap(order[2],order[3]);
vector<SpinorBarWaveFunction> q1,q2;
vector<SpinorWaveFunction> q3,q4;
SpinorBarWaveFunction(q1,hard[order[0]],incoming,false,true);
SpinorBarWaveFunction(q2,hard[order[1]],incoming,false,true);
SpinorWaveFunction( q3,hard[order[2]],outgoing,true ,true);
SpinorWaveFunction( q4,hard[order[3]],outgoing,true ,true);
qbarqbar2qbarqbarME(q1,q2,q3,q4,_flow);
}
else throw Exception() << "Unknown process in MEQCD2to2::constructVertex()"
<< Exception::runerror;
// get the spin info objects
for(unsigned int ix=0;ix<4;++ix)
spin[ix]=dynamic_ptr_cast<SpinfoPtr>(hard[order[ix]]->spinInfo());
// construct the vertex
HardVertexPtr hardvertex=new_ptr(HardVertex());
// set the matrix element for the vertex
hardvertex->ME(_me);
// set the pointers and to and from the vertex
for(unsigned int ix=0;ix<4;++ix) spin[ix]->setProductionVertex(hardvertex);
}

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