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MEPP2QQ.cc
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// -*- C++ -*-
//
// MEPP2QQ.cc 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.
//
//
// This is the implementation of the non-inlined, non-templated member
// functions of the MEPP2QQ class.
//
#include "MEPP2QQ.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Interface/Switch.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "Herwig++/Models/StandardModel/StandardModel.h"
#include "ThePEG/PDT/EnumParticles.h"
#include "ThePEG/MatrixElement/Tree2toNDiagram.h"
#include "ThePEG/Handlers/StandardXComb.h"
#include "Herwig++/MatrixElement/HardVertex.h"
#include "ThePEG/Repository/EventGenerator.h"
using namespace Herwig;
MEPP2QQ::MEPP2QQ() : _quarkflavour(6), _process(0),
_bottomopt(1), _topopt(1), _maxflavour(5) {
}
void MEPP2QQ::rebind(const TranslationMap & trans) {
_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]);
HwMEBase::rebind(trans);
}
IVector MEPP2QQ::getReferences() {
IVector ret = HwMEBase::getReferences();
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 MEPP2QQ::doinit() {
HwMEBase::doinit();
// handling of masses
if(_quarkflavour==6) {
massOption(vector<unsigned int>(2,_topopt));
}
else {
massOption(vector<unsigned int>(2,_bottomopt));
}
// get the vertex pointers from the SM object
tcHwSMPtr hwsm= dynamic_ptr_cast<tcHwSMPtr>(standardModel());
// do the initialisation
if(hwsm) {
_qqgvertex = hwsm->vertexFFG();
_gggvertex = hwsm->vertexGGG();
}
else throw InitException()
<< "Wrong type of StandardModel object in "
<< "MEPP2QQ::doinit() the Herwig++ version must be used"
<< Exception::runerror;
// get the particle data objects
_gluon=getParticleData(ParticleID::g);
for(int ix=1;ix<=6;++ix) {
_quark.push_back( getParticleData( ix));
_antiquark.push_back(getParticleData(-ix));
}
}
Energy2 MEPP2QQ::scale() const {
Energy2 mq2 = max(meMomenta()[2].mass2(),meMomenta()[3].mass2());
Energy2 s(0.5*sHat()),u(0.5*(uHat()-mq2)),t(0.5*(tHat()-mq2));
return 4.*s*t*u/(s*s+t*t+u*u);
}
void MEPP2QQ::persistentOutput(PersistentOStream & os) const {
os << _gggvertex << _qqgvertex << _quarkflavour << _bottomopt << _topopt
<< _process << _gluon << _quark << _antiquark << _maxflavour;
}
void MEPP2QQ::persistentInput(PersistentIStream & is, int) {
is >> _gggvertex >> _qqgvertex >> _quarkflavour >> _bottomopt >> _topopt
>> _process >> _gluon >> _quark >> _antiquark >> _maxflavour;
}
unsigned int MEPP2QQ::orderInAlphaS() const {
return 2;
}
unsigned int MEPP2QQ::orderInAlphaEW() const {
return 0;
}
ClassDescription<MEPP2QQ> MEPP2QQ::initMEPP2QQ;
// Definition of the static class description member.
void MEPP2QQ::Init() {
static ClassDocumentation<MEPP2QQ> documentation
("The MEPP2QQ class implements the matrix element for"
" heavy quark pair production");
static Switch<MEPP2QQ,unsigned int> interfaceQuarkType
("QuarkType",
"The type of quark",
&MEPP2QQ::_quarkflavour, 6, false, false);
static SwitchOption interfaceQuarkTypeCharm
(interfaceQuarkType,
"Charm",
"Produce charm-anticharm",
4);
static SwitchOption interfaceQuarkTypeBottom
(interfaceQuarkType,
"Bottom",
"Produce bottom-antibottom",
5);
static SwitchOption interfaceQuarkTypeTop
(interfaceQuarkType,
"Top",
"Produce top-antitop",
6);
static Switch<MEPP2QQ,unsigned int> interfaceProcess
("Process",
"Which subprocesses to include",
&MEPP2QQ::_process, 0, false, false);
static SwitchOption interfaceProcessAll
(interfaceProcess,
"All",
"Include all subprocesses",
0);
static SwitchOption interfaceProcessPair
(interfaceProcess,
"Pair",
"Only include quark-antiquark pair production subprocesses",
1);
static SwitchOption interfaceProcess1
(interfaceProcess,
"gg2qqbar",
"Include only gg -> q qbar processes",
2);
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);
static Switch<MEPP2QQ,unsigned int> interfaceTopMassOption
("TopMassOption",
"Option for the treatment of the top quark mass",
&MEPP2QQ::_topopt, 1, false, false);
static SwitchOption interfaceTopMassOptionOnMassShell
(interfaceTopMassOption,
"OnMassShell",
"The top is produced on its mass shell",
1);
static SwitchOption interfaceTopMassOption2
(interfaceTopMassOption,
"OffShell",
"The top is generated off-shell using the mass and width generator.",
2);
static Switch<MEPP2QQ,unsigned int> interfaceBottomMassOption
("CharmBottomMassOption",
"Option for the treatment of bottom and lighter quark masses",
&MEPP2QQ::_bottomopt, 1, false, false);
static SwitchOption interfaceBottomMassOptionOnMassShell
(interfaceBottomMassOption,
"OnMassShell",
"The bottom is produced on its mass shell, this mass used everywhere",
1);
static SwitchOption interfaceBottomMassOptionZeroMass
(interfaceBottomMassOption,
"ZeroMass",
"The bottom is generated on mass shell, but zero mass is used in"
" the matrix element",
0);
static Parameter<MEPP2QQ,unsigned int> interfaceMaximumFlavour
("MaximumFlavour",
"The maximum flavour of the quarks in the process",
&MEPP2QQ::_maxflavour, 5, 1, 5,
false, false, Interface::limited);
}
Selector<MEBase::DiagramIndex>
MEPP2QQ::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 MEPP2QQ::gg2qqbarME(vector<VectorWaveFunction> &g1,
vector<VectorWaveFunction> &g2,
vector<SpinorBarWaveFunction> & q,
vector<SpinorWaveFunction> & qbar,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
Energy mass = q[0].mass();
// 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,3,qbar[ohel2].particle(),
qbar[ohel2],g2[ihel2],mass);
diag[0]=_qqgvertex->evaluate(mt,inters,q[ohel1],g1[ihel1]);
//second t-channel diagram
inters =_qqgvertex->evaluate(mt,3,qbar[ohel2].particle(),
qbar[ohel2],g1[ihel1],mass);
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];
}
}
}
}
// 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
// Energy2 mq2=sqr(getParticleData(6)->mass());
// double tau1=(tHat()-mq2)/sHat(),tau2=(uHat()-mq2)/sHat(),rho=4*mq2/sHat();
// double test=(1./6./tau1/tau2-3./8.)*sqr(4.*pi*SM().alphaS(mt))*
// (sqr(tau1)+sqr(tau2)+rho-0.25*sqr(rho)/tau1/tau2);
// cerr << "testing matrix element "
// << output/48./test << "\n";
return output/48.;
}
double MEPP2QQ::qg2qgME(vector<SpinorWaveFunction> & qin,
vector<VectorWaveFunction> &g2,
vector<SpinorBarWaveFunction> & qout,
vector<VectorWaveFunction> &g4,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
Energy mass = qout[0].mass();
// 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,3,qin[ihel1].particle()->CC(),
qin[ihel1],g2[ihel2],mass);
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,3,qin[ihel1].particle()->CC(),
qin[ihel1],g4[ohel2],mass);
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 MEPP2QQ::qbarg2qbargME(vector<SpinorBarWaveFunction> & qin,
vector<VectorWaveFunction> &g2,
vector<SpinorWaveFunction> & qout,
vector<VectorWaveFunction> &g4,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
Energy mass = qout[0].mass();
// 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,3,qin[ihel1].particle()->CC(),
qin[ihel1],g2[ihel2],mass);
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,3,qin[ihel1].particle()->CC(),
qin[ihel1],g4[ohel2],mass);
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 MEPP2QQ::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 MEPP2QQ::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 MEPP2QQ::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];
}
}
}
}
//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
// Energy2 mq2=sqr(getParticleData(6)->mass());
// double tau1=(tHat()-mq2)/sHat(),tau2=(uHat()-mq2)/sHat(),rho=4*mq2/sHat();
// cerr << "testing matrix element "
// << output/18./(4./9.*sqr(4.*pi*SM().alphaS(mt))*(sqr(tau1)+sqr(tau2)+0.5*rho))
// << "\n";
return output/18.;
}
void MEPP2QQ::getDiagrams() const {
// gg -> q qbar subprocesses
if(_process==0||_process==1||_process==2) {
// first t-channel
add(new_ptr((Tree2toNDiagram(3),_gluon,_antiquark[_quarkflavour-1],_gluon,
1,_quark[_quarkflavour-1], 2,_antiquark[_quarkflavour-1],-4)));
// interchange
add(new_ptr((Tree2toNDiagram(3),_gluon,_antiquark[_quarkflavour-1],_gluon,
2,_quark[_quarkflavour-1], 1,_antiquark[_quarkflavour-1],-5)));
// s-channel
add(new_ptr((Tree2toNDiagram(2),_gluon,_gluon, 1, _gluon,
3,_quark[_quarkflavour-1], 3, _antiquark[_quarkflavour-1], -6)));
}
// q g -> q g subprocesses
if(_process==0||_process==4) {
// s-channel
add(new_ptr((Tree2toNDiagram(2),_quark[_quarkflavour-1], _gluon,
1, _quark[_quarkflavour-1],
3, _quark[_quarkflavour-1], 3, _gluon,-10)));
// quark t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[_quarkflavour-1],
_quark[_quarkflavour-1],_gluon,
2,_quark[_quarkflavour-1],1,_gluon,-11)));
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[_quarkflavour-1],_gluon,_gluon,
1,_quark[_quarkflavour-1],2,_gluon,-12)));
}
// qbar g -> qbar g subprocesses
if(_process==0||_process==5) {
// s-channel
add(new_ptr((Tree2toNDiagram(2),_antiquark[_quarkflavour-1], _gluon,
1, _antiquark[_quarkflavour-1],
3, _antiquark[_quarkflavour-1], 3, _gluon,-13)));
// quark t-channel
add(new_ptr((Tree2toNDiagram(3),_antiquark[_quarkflavour-1],
_antiquark[_quarkflavour-1],_gluon,
2,_antiquark[_quarkflavour-1],1,_gluon,-14)));
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_antiquark[_quarkflavour-1],_gluon,_gluon,
1,_antiquark[_quarkflavour-1],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[_quarkflavour-1],_gluon,_quark[iy],
1,_quark[_quarkflavour-1],2,_quark[iy],-16)));
// exchange for identical quarks
if(_quarkflavour-1==iy)
add(new_ptr((Tree2toNDiagram(3),_quark[_quarkflavour-1],_gluon,_quark[iy],
2,_quark[_quarkflavour-1],1,_quark[iy],-17)));
}
// qbar qbar -> qbar qbar subprocesses
if(_process==0||_process==7) {
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_antiquark[_quarkflavour-1],_gluon,_antiquark[iy],
1,_antiquark[_quarkflavour-1],2,_antiquark[iy],-18)));
// exchange for identical quarks
if(_quarkflavour-1==iy)
add(new_ptr((Tree2toNDiagram(3),_antiquark[_quarkflavour-1],_gluon,_antiquark[iy],
2,_antiquark[_quarkflavour-1],1,_antiquark[iy],-19)));
}
// q qbar -> q qbar
if(_process==0||_process==1||_process==8) {
// gluon s-channel
add(new_ptr((Tree2toNDiagram(2),_quark[iy], _antiquark[iy],
1, _gluon, 3, _quark[_quarkflavour-1],
3, _antiquark[_quarkflavour-1],-20)));
if(_process!=1) {
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[iy],_gluon,_antiquark[_quarkflavour-1],
1,_quark[iy],2,_antiquark[_quarkflavour-1],-21)));
// gluon t-channel
add(new_ptr((Tree2toNDiagram(3),_quark[_quarkflavour-1],_gluon,_antiquark[iy],
1,_quark[_quarkflavour-1],2,_antiquark[iy],-21)));
}
}
}
}
Selector<const ColourLines *>
MEPP2QQ::colourGeometries(tcDiagPtr diag) const {
// 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 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 -> 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 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 MEPP2QQ::me2() const {
// total matrix element
double me(0.);
// gg initiated processes
if(mePartonData()[0]->id()==ParticleID::g&&mePartonData()[1]->id()==ParticleID::g) {
VectorWaveFunction g1w(rescaledMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction g2w(rescaledMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction qw(rescaledMomenta()[2],mePartonData()[2],outgoing);
SpinorWaveFunction qbarw(rescaledMomenta()[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(rescaledMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction g2w(rescaledMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction qoutw(rescaledMomenta()[2],mePartonData()[2],outgoing);
VectorWaveFunction g4w(rescaledMomenta()[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);
}
// q qbar to q qbar
else if(mePartonData()[1]->id()<0) {
SpinorWaveFunction q1w(rescaledMomenta()[0],mePartonData()[0],incoming);
SpinorBarWaveFunction q2w(rescaledMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction q3w(rescaledMomenta()[2],mePartonData()[2],outgoing);
SpinorWaveFunction q4w(rescaledMomenta()[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(rescaledMomenta()[0],mePartonData()[0],incoming);
SpinorWaveFunction q2w(rescaledMomenta()[1],mePartonData()[1],incoming);
SpinorBarWaveFunction q3w(rescaledMomenta()[2],mePartonData()[2],outgoing);
SpinorBarWaveFunction q4w(rescaledMomenta()[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(rescaledMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction g2w(rescaledMomenta()[1],mePartonData()[1],incoming);
SpinorWaveFunction qoutw(rescaledMomenta()[2],mePartonData()[2],outgoing);
VectorWaveFunction g4w(rescaledMomenta()[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(rescaledMomenta()[0],mePartonData()[0],incoming);
SpinorBarWaveFunction q2w(rescaledMomenta()[1],mePartonData()[1],incoming);
SpinorWaveFunction q3w(rescaledMomenta()[2],mePartonData()[2],outgoing);
SpinorWaveFunction q4w(rescaledMomenta()[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 MEPP2QQ::me2()"
<< Exception::abortnow;
// return the answer
return me;
}
void MEPP2QQ::constructVertex(tSubProPtr sub) {
// 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]);
// identify the process and calculate the matrix element
if(hard[0]->id()==ParticleID::g&&hard[1]->id()==ParticleID::g) {
if(hard[2]->id()<0) swap(hard[2],hard[3]);
vector<VectorWaveFunction> g1,g2;
vector<SpinorBarWaveFunction> q;
vector<SpinorWaveFunction> qbar;
// off-shell wavefunctions for the spin correlations
VectorWaveFunction( g1,hard[0],incoming,false,true,true);
VectorWaveFunction( g2,hard[1],incoming,false,true,true);
SpinorBarWaveFunction(q ,hard[2],outgoing,true ,true);
SpinorWaveFunction( qbar,hard[3],outgoing,true ,true);
g1[1]=g1[2];g2[1]=g2[2];
// on-shell for matrix element
vector<Lorentz5Momentum> momenta;
cPDVector data;
for(unsigned int ix=0;ix<4;++ix) {
momenta.push_back(hard[ix]->momentum());
data .push_back(hard[ix]->dataPtr());
}
rescaleMomenta(momenta,data);
VectorWaveFunction g1w(rescaledMomenta()[0],data[0],incoming);
VectorWaveFunction g2w(rescaledMomenta()[1],data[1],incoming);
SpinorBarWaveFunction qw(rescaledMomenta()[2],data[2],outgoing);
SpinorWaveFunction qbarw(rescaledMomenta()[3],data[3],outgoing);
for(unsigned int ix=0;ix<2;++ix) {
g1w.reset(2*ix); g1 [ix] = g1w ;
g2w.reset(2*ix); g2 [ix] = g2w ;
qw.reset(ix); q [ix] = qw ;
qbarw.reset(ix); qbar[ix] = qbarw;
}
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(hard[0],hard[1]);
if(hard[2]->id()==ParticleID::g) swap(hard[2],hard[3]);
// on-shell for matrix element
vector<Lorentz5Momentum> momenta;
cPDVector data;
for(unsigned int ix=0;ix<4;++ix) {
momenta.push_back(hard[ix]->momentum());
data .push_back(hard[ix]->dataPtr());
}
rescaleMomenta(momenta,data);
vector<VectorWaveFunction> g2,g4;
VectorWaveFunction(g2,hard[1],incoming,false,true,true);
VectorWaveFunction(g4,hard[3],outgoing,true ,true,true);
VectorWaveFunction gin (rescaledMomenta()[1],data[1],incoming);
VectorWaveFunction gout(rescaledMomenta()[3],data[3],outgoing);
for(unsigned int ix=0;ix<2;++ix) {
gin .reset(2*ix); g2 [ix] = gin ;
gout.reset(2*ix); g4 [ix] = gout;
}
// q g -> q g
if(hard[0]->id()>0) {
vector<SpinorWaveFunction> q1;
vector<SpinorBarWaveFunction> q3;
SpinorWaveFunction( q1,hard[0],incoming,false,true);
SpinorBarWaveFunction(q3,hard[2],outgoing,true ,true);
SpinorWaveFunction qin (rescaledMomenta()[0],data[0],incoming);
SpinorBarWaveFunction qout(rescaledMomenta()[2],data[2],outgoing);
for(unsigned int ix=0;ix<2;++ix) {
qin .reset(ix); q1[ix] = qin ;
qout.reset(ix); q3[ix] = qout;
}
qg2qgME(q1,g2,q3,g4,_flow);
}
// qbar g -> qbar g
else {
vector<SpinorBarWaveFunction> q1;
vector<SpinorWaveFunction> q3;
SpinorBarWaveFunction(q1,hard[0],incoming,false,true);
SpinorWaveFunction( q3,hard[2],outgoing,true ,true);
SpinorBarWaveFunction qin (rescaledMomenta()[0],data[0],incoming);
SpinorWaveFunction qout(rescaledMomenta()[2],data[2],outgoing);
for(unsigned int ix=0;ix<2;++ix) {
qin .reset(ix); q1[ix] = qin ;
qout.reset(ix); q3[ix] = qout;
}
qbarg2qbargME(q1,g2,q3,g4,_flow);
}
}
else if(hard[0]->id()>0||hard[1]->id()>0) {
// q q -> q q
if(hard[0]->id()>0&&hard[1]->id()>0) {
if(hard[2]->id()!=hard[0]->id()) swap(hard[2],hard[3]);
vector<SpinorWaveFunction> q1,q2;
vector<SpinorBarWaveFunction> q3,q4;
SpinorWaveFunction( q1,hard[0],incoming,false,true);
SpinorWaveFunction( q2,hard[1],incoming,false,true);
SpinorBarWaveFunction(q3,hard[2],outgoing,true ,true);
SpinorBarWaveFunction(q4,hard[3],outgoing,true ,true);
// on-shell for matrix element
vector<Lorentz5Momentum> momenta;
cPDVector data;
for(unsigned int ix=0;ix<4;++ix) {
momenta.push_back(hard[ix]->momentum());
data .push_back(hard[ix]->dataPtr());
}
rescaleMomenta(momenta,data);
SpinorWaveFunction q1w(rescaledMomenta()[0],data[0],incoming);
SpinorWaveFunction q2w(rescaledMomenta()[1],data[1],incoming);
SpinorBarWaveFunction q3w(rescaledMomenta()[2],data[2],outgoing);
SpinorBarWaveFunction q4w(rescaledMomenta()[3],data[3],outgoing);
for(unsigned int ix=0;ix<2;++ix) {
q1w.reset(ix);q1[ix] = q1w;
q2w.reset(ix);q2[ix] = q2w;
q3w.reset(ix);q3[ix] = q3w;
q4w.reset(ix);q4[ix] = q4w;
}
qq2qqME(q1,q2,q3,q4,_flow);
}
// q qbar -> q qbar
else {
if(hard[0]->id()<0) swap(hard[0],hard[1]);
if(hard[2]->id()<0) swap(hard[2],hard[3]);
vector<SpinorWaveFunction> q1,q4;
vector<SpinorBarWaveFunction> q2,q3;
// off-shell for spin correlations
SpinorWaveFunction( q1,hard[0],incoming,false,true);
SpinorBarWaveFunction(q2,hard[1],incoming,false,true);
SpinorBarWaveFunction(q3,hard[2],outgoing,true ,true);
SpinorWaveFunction( q4,hard[3],outgoing,true ,true);
// on-shell for matrix element
vector<Lorentz5Momentum> momenta;
cPDVector data;
for(unsigned int ix=0;ix<4;++ix) {
momenta.push_back(hard[ix]->momentum());
data .push_back(hard[ix]->dataPtr());
}
rescaleMomenta(momenta,data);
SpinorWaveFunction q1w(rescaledMomenta()[0],data[0],incoming);
SpinorBarWaveFunction q2w(rescaledMomenta()[1],data[1],incoming);
SpinorBarWaveFunction q3w(rescaledMomenta()[2],data[2],outgoing);
SpinorWaveFunction q4w(rescaledMomenta()[3],data[3],outgoing);
for(unsigned int ix=0;ix<2;++ix) {
q1w.reset(ix);q1[ix] = q1w;
q2w.reset(ix);q2[ix] = q2w;
q3w.reset(ix);q3[ix] = q3w;
q4w.reset(ix);q4[ix] = q4w;
}
qqbar2qqbarME(q1,q2,q3,q4,_flow);
}
}
else if (hard[0]->id()<0&&hard[1]->id()<0) {
if(hard[2]->id()!=hard[0]->id()) swap(hard[2],hard[3]);
vector<SpinorBarWaveFunction> q1,q2;
vector<SpinorWaveFunction> q3,q4;
SpinorBarWaveFunction(q1,hard[0],incoming,false,true);
SpinorBarWaveFunction(q2,hard[1],incoming,false,true);
SpinorWaveFunction( q3,hard[2],outgoing,true ,true);
SpinorWaveFunction( q4,hard[3],outgoing,true ,true);
// on-shell for matrix element
vector<Lorentz5Momentum> momenta;
cPDVector data;
for(unsigned int ix=0;ix<4;++ix) {
momenta.push_back(hard[ix]->momentum());
data .push_back(hard[ix]->dataPtr());
}
rescaleMomenta(momenta,data);
SpinorBarWaveFunction q1w(rescaledMomenta()[0],data[0],incoming);
SpinorBarWaveFunction q2w(rescaledMomenta()[1],data[1],incoming);
SpinorWaveFunction q3w(rescaledMomenta()[2],data[2],outgoing);
SpinorWaveFunction q4w(rescaledMomenta()[3],data[3],outgoing);
for(unsigned int ix=0;ix<2;++ix) {
q1w.reset(ix);q1[ix] = q1w;
q2w.reset(ix);q2[ix] = q2w;
q3w.reset(ix);q3[ix] = q3w;
q4w.reset(ix);q4[ix] = q4w;
}
qbarqbar2qbarqbarME(q1,q2,q3,q4,_flow);
}
else throw Exception() << "Unknown process in MEPP2QQ::constructVertex()"
<< Exception::runerror;
// 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)
hard[ix]->spinInfo()->productionVertex(hardvertex);
}

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