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MEPP2QQHiggs.cc
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MEPP2QQHiggs.cc
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// -*- C++ -*-
//
// This is the implementation of the non-inlined, non-templated member
// functions of the MEPP2QQH class.
//
#include "MEPP2QQHiggs.h"
#include "ThePEG/Interface/Switch.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/PDT/EnumParticles.h"
#include "ThePEG/MatrixElement/Tree2toNDiagram.h"
#include "Herwig++/Models/StandardModel/StandardModel.h"
#include "ThePEG/Utilities/SimplePhaseSpace.h"
#include "Herwig++/Utilities/Kinematics.h"
#include "ThePEG/Cuts/Cuts.h"
#include "Herwig++/MatrixElement/HardVertex.h"
using namespace Herwig;
MEPP2QQHiggs::MEPP2QQHiggs() : quarkFlavour_(6), process_(0), shapeOpt_(2),
mh_(), wh_(), alpha_(1.1)
{}
ClassDescription<MEPP2QQHiggs> MEPP2QQHiggs::initMEPP2QQHiggs;
// Definition of the static class description member.
void MEPP2QQHiggs::Init() {
static ClassDocumentation<MEPP2QQHiggs> documentation
("The MEPP2QQHiggs class implements the matrix elements for the "
"production of the Higgs boson in association with a heavy quark-antiquark pair");
static Switch<MEPP2QQHiggs,unsigned int> interfaceQuarkType
("QuarkType",
"The type of quark",
&MEPP2QQHiggs::quarkFlavour_, 6, false, false);
static SwitchOption interfaceQuarkTypeBottom
(interfaceQuarkType,
"Bottom",
"Produce bottom-antibottom",
5);
static SwitchOption interfaceQuarkTypeTop
(interfaceQuarkType,
"Top",
"Produce top-antitop",
6);
static Switch<MEPP2QQHiggs,unsigned int> interfaceProcess
("Process",
"Which subprocesses to include",
&MEPP2QQHiggs::process_, 0, false, false);
static SwitchOption interfaceProcessAll
(interfaceProcess,
"All",
"Include all subprocesses",
0);
static SwitchOption interfaceProcess1
(interfaceProcess,
"gg",
"Include only gg -> QQbarH processes",
1);
static SwitchOption interfaceProcessqbarqbarqbarqbar
(interfaceProcess,
"qqbar",
"Include only qbar qbar -> QQbarH processes",
2);
static Switch<MEPP2QQHiggs,unsigned int> interfaceShapeOption
("ShapeScheme",
"Option for the treatment of the Higgs resonance shape",
&MEPP2QQHiggs::shapeOpt_, 2, false, false);
static SwitchOption interfaceStandardShapeFixed
(interfaceShapeOption,
"FixedBreitWigner",
"Breit-Wigner s-channel resonance",
1);
static SwitchOption interfaceStandardShapeRunning
(interfaceShapeOption,
"MassGenerator",
"Use the mass generator to give the shape",
2);
static SwitchOption interfaceStandardShapeOnShell
(interfaceShapeOption,
"OnShell",
"Produce an on-shell Higgs boson",
0);
static Parameter<MEPP2QQHiggs,double> interfaceAlpha
("Alpha",
"Power for the generation of the tranverse mass in the pT mapping",
&MEPP2QQHiggs::alpha_, 1.1, 0.0, 10.0,
false, false, Interface::limited);
}
Energy2 MEPP2QQHiggs::scale() const {
return sHat();
// return sqr(mePartonData()[2]->mass()+mePartonData()[3]->mass()+
// mePartonData()[4]->mass());
}
int MEPP2QQHiggs::nDim() const {
return 4 + int(shapeOpt_>0);
}
unsigned int MEPP2QQHiggs::orderInAlphaS() const {
return 2;
}
unsigned int MEPP2QQHiggs::orderInAlphaEW() const {
return 1;
}
IBPtr MEPP2QQHiggs::clone() const {
return new_ptr(*this);
}
IBPtr MEPP2QQHiggs::fullclone() const {
return new_ptr(*this);
}
void MEPP2QQHiggs::setKinematics() {
HwMEBase::setKinematics();
}
void MEPP2QQHiggs::persistentOutput(PersistentOStream & os) const {
os << quarkFlavour_ << process_ << shapeOpt_
<< ounit(mh_,GeV) << ounit(wh_,GeV) << hmass_
<< GGGVertex_ << QQGVertex_ << QQHVertex_
<< gluon_ << higgs_ << quark_ << antiquark_
<< alpha_;
}
void MEPP2QQHiggs::persistentInput(PersistentIStream & is, int) {
is >> quarkFlavour_ >> process_ >> shapeOpt_
>> iunit(mh_,GeV) >> iunit(wh_,GeV) >> hmass_
>> GGGVertex_ >> QQGVertex_ >> QQHVertex_
>> gluon_ >> higgs_ >> quark_ >> antiquark_
>> alpha_;
}
void MEPP2QQHiggs::doinit() {
HwMEBase::doinit();
// stuff for the higgs mass
higgs_=getParticleData(ParticleID::h0);
mh_ = higgs_->mass();
wh_ = higgs_->width();
if(higgs_->massGenerator()) {
hmass_=dynamic_ptr_cast<GenericMassGeneratorPtr>(higgs_->massGenerator());
}
if(shapeOpt_==2&&!hmass_)
throw InitException()
<< "If using the mass generator for the line shape in MEPP2QQHiggs::doinit()"
<< "the mass generator must be an instance of the GenericMassGenerator class"
<< Exception::runerror;
// get the vertex pointers from the SM object
tcHwSMPtr hwsm= dynamic_ptr_cast<tcHwSMPtr>(standardModel());
// do the initialisation
if(!hwsm) throw InitException() << "Wrong type of StandardModel object in "
<< "MEPP2QQHiggs::doinit() the Herwig++"
<< " version must be used"
<< Exception::runerror;
GGGVertex_ = hwsm->vertexGGG();
QQGVertex_ = hwsm->vertexFFG();
QQHVertex_ = hwsm->vertexFFH();
// 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));
}
}
bool MEPP2QQHiggs::generateKinematics(const double * r) {
jacobian(1.);
// CMS energy
Energy rs = sqrt(sHat());
// quark mass
Energy mq(quark_[quarkFlavour_-1]->mass());
// generate the higgs mass
Energy mh(mh_);
if(shapeOpt_!=0) {
Energy mhmax = min(rs-2.*mq,higgs_->massMax());
Energy mhmin = max(ZERO ,higgs_->massMin());
if(mhmax<=mhmin) return false;
double rhomin = atan2((sqr(mhmin)-sqr(mh_)), mh_*wh_);
double rhomax = atan2((sqr(mhmax)-sqr(mh_)), mh_*wh_);
mh = sqrt(mh_*wh_*tan(rhomin+r[4]*(rhomax-rhomin))+sqr(mh_));
jacobian(jacobian()*(rhomax-rhomin));
}
if(rs<mh+2.*mq) return false;
// limits for virtual quark mass
Energy2 mmin(sqr(mq+mh)),mmax(sqr(rs-mq));
double rhomin,rhomax;
if(alpha_==0.) {
rhomin = mmin/sqr(mq);
rhomax = mmax/sqr(mq);
}
else if(alpha_==1.) {
rhomax = log((mmax-sqr(mq))/sqr(mq));
rhomin = log((mmin-sqr(mq))/sqr(mq));
}
else {
rhomin = pow((mmax-sqr(mq))/sqr(mq),1.-alpha_);
rhomax = pow((mmin-sqr(mq))/sqr(mq),1.-alpha_);
jacobian(jacobian()/(alpha_-1.));
}
// branch for mass smoothing
Energy2 m132,m232;
Energy p1,p2;
// first branch
if(r[1]<=0.5) {
double rtemp = 2.*r[1];
double rho = rhomin+rtemp*(rhomax-rhomin);
if(alpha_==0)
m132 = sqr(mq)*rho;
else if(alpha_==1)
m132 = sqr(mq)*(exp(rho)+1.);
else
m132 = sqr(mq)*(pow(rho,1./(1.-alpha_))+1.);
Energy m13 = sqrt(m132);
try {
p1 = SimplePhaseSpace::getMagnitude(sHat(), m13, mq);
p2 = SimplePhaseSpace::getMagnitude(m132,mq,mh);
} catch ( ImpossibleKinematics ) {
return false;
}
Energy ptmin = lastCuts().minKT(mePartonData()[3]);
double ctmin = -1.0, ctmax = 1.0;
if ( ptmin > ZERO ) {
double ctm = 1.0 - sqr(ptmin/p1);
if ( ctm <= 0.0 ) return false;
ctmin = max(ctmin, -sqrt(ctm));
ctmax = min(ctmax, sqrt(ctm));
}
double cos1 = getCosTheta(ctmin,ctmax,r[0]);
double sin1(sqrt(1.-sqr(cos1)));
double phi1 = Constants::twopi*UseRandom::rnd();
Lorentz5Momentum p13(sin1*p1*cos(phi1),sin1*p1*sin(phi1),cos1*p1,
sqrt(sqr(p1)+m132),m13);
meMomenta()[3].setVect(Momentum3(-sin1*p1*cos(phi1),-sin1*p1*sin(phi1),-cos1*p1));
meMomenta()[3].setMass(mq);
meMomenta()[3].rescaleEnergy();
bool test=Kinematics::twoBodyDecay(p13,mq,mh,-1.+2*r[2],r[3]*Constants::twopi,
meMomenta()[2],meMomenta()[4]);
if(!test) return false;
m232 = (meMomenta()[3]+meMomenta()[4]).m2();
double D = 2./(pow(sqr(mq)/(m132-sqr(mq)),alpha_)+
pow(sqr(mq)/(m232-sqr(mq)),alpha_));
jacobian(0.5*jacobian()*rs/m13*sqr(mq)*D*(rhomax-rhomin)/sHat());
}
// second branch
else {
double rtemp = 2.*(r[1]-0.5);
double rho = rhomin+rtemp*(rhomax-rhomin);
if(alpha_==0)
m232 = sqr(mq)*rho;
else if(alpha_==1)
m232 = sqr(mq)*(exp(rho)+1.);
else
m232 = sqr(mq)*(pow(rho,1./(1.-alpha_))+1.);
Energy m23 = sqrt(m232);
try {
p1 = SimplePhaseSpace::getMagnitude(sHat(), m23, mq);
p2 = SimplePhaseSpace::getMagnitude(m232,mq,mh);
} catch ( ImpossibleKinematics ) {
return false;
}
Energy ptmin = lastCuts().minKT(mePartonData()[2]);
double ctmin = -1.0, ctmax = 1.0;
if ( ptmin > ZERO ) {
double ctm = 1.0 - sqr(ptmin/p1);
if ( ctm <= 0.0 ) return false;
ctmin = max(ctmin, -sqrt(ctm));
ctmax = min(ctmax, sqrt(ctm));
}
double cos1 = getCosTheta(ctmin,ctmax,r[0]);
double sin1(sqrt(1.-sqr(cos1)));
double phi1 = Constants::twopi*UseRandom::rnd();
Lorentz5Momentum p23(-sin1*p1*cos(phi1),-sin1*p1*sin(phi1),-cos1*p1,
sqrt(sqr(p1)+m232),m23);
meMomenta()[2].setVect(Momentum3(sin1*p1*cos(phi1),sin1*p1*sin(phi1),cos1*p1));
meMomenta()[2].setMass(mq);
meMomenta()[2].rescaleEnergy();
bool test=Kinematics::twoBodyDecay(p23,mq,mh,-1.+2*r[2],r[3]*Constants::twopi,
meMomenta()[3],meMomenta()[4]);
if(!test) return false;
m132 = (meMomenta()[2]+meMomenta()[4]).m2();
double D = 2./(pow(sqr(mq)/(m132-sqr(mq)),alpha_)+
pow(sqr(mq)/(m232-sqr(mq)),alpha_));
jacobian(0.5*jacobian()*rs/m23*sqr(mq)*D*(rhomax-rhomin)/sHat());
}
// calculate jacobian
jacobian(0.125*jacobian()*p1*p2/sHat());
// check cuts
vector<LorentzMomentum> out;
tcPDVector tout;
for(unsigned int ix=2;ix<5;++ix) {
out .push_back(meMomenta()[ix]);
tout.push_back(mePartonData()[ix]);
}
return lastCuts().passCuts(tout, out, mePartonData()[0], mePartonData()[1]);
}
CrossSection MEPP2QQHiggs::dSigHatDR() const {
using Constants::pi;
// jacobian factor for the higgs
InvEnergy2 bwfact;
Energy moff = meMomenta()[4].mass();
if(shapeOpt_==1) {
bwfact = mePartonData()[4]->generateWidth(moff)*moff/pi/
(sqr(sqr(moff)-sqr(mh_))+sqr(mh_*wh_));
}
else {
bwfact = hmass_->BreitWignerWeight(moff);
}
double jac1 = shapeOpt_==0 ?
1. : double(bwfact*(sqr(sqr(moff)-sqr(mh_))+sqr(mh_*wh_))/(mh_*wh_));
return sqr(hbarc)*me2()*jacobian()*jac1/sHat()/pow(Constants::twopi,3);
}
void MEPP2QQHiggs::getDiagrams() const {
tPDPtr Q = quark_[quarkFlavour_-1];
tPDPtr QB = antiquark_[quarkFlavour_-1];
// gg -> q qbar h0 subprocesses
if(process_==0||process_==1) {
// first t-channel
add(new_ptr((Tree2toNDiagram(3), gluon_, QB, gluon_,
1, Q, 4, Q , 2, QB, 4, higgs_, -1)));
add(new_ptr((Tree2toNDiagram(4), gluon_, QB, QB, gluon_,
1, Q, 3, QB, 2, higgs_, -2)));
add(new_ptr((Tree2toNDiagram(3),gluon_,QB,gluon_,
1, Q, 2, QB, 5, QB, 5, higgs_, -3)));
// interchange
add(new_ptr((Tree2toNDiagram(3),gluon_,Q,gluon_,
2, Q, 4, Q , 1, QB, 4, higgs_, -4)));
add(new_ptr((Tree2toNDiagram(4),gluon_,Q,Q,gluon_,
3, Q, 1, QB, 2, higgs_, -5)));
add(new_ptr((Tree2toNDiagram(3),gluon_,Q,gluon_,
2, Q, 1, QB, 5, QB, 5, higgs_, -6)));
// s-channel
add(new_ptr((Tree2toNDiagram(2),gluon_,gluon_, 1, gluon_,
3, Q, 4, Q, 3, QB, 4, higgs_, -7)));
add(new_ptr((Tree2toNDiagram(2),gluon_,gluon_, 1, gluon_,
3,Q, 3, QB, 5, QB, 5, higgs_, -8)));
}
// q qbar -> q qbar
if(process_==0||process_==2) {
for(unsigned int ix=1;ix<5;++ix) {
// gluon s-channel
add(new_ptr((Tree2toNDiagram(2),quark_[ix-1], antiquark_[ix-1],
1, gluon_, 3, Q, 4, Q , 3, QB, 4, higgs_, -9)));
add(new_ptr((Tree2toNDiagram(2),quark_[ix-1], antiquark_[ix-1],
1, gluon_, 3, Q, 3, QB, 5, QB, 5, higgs_, -10)));
}
}
}
double MEPP2QQHiggs::me2() const {
// total matrix element
double me(0.);
// gg initiated processes
if(mePartonData()[0]->id()==ParticleID::g) {
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);
ScalarWaveFunction higgs(meMomenta()[4],mePartonData()[4],1.,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=ggME(g1,g2,q,qbar,higgs,0);
}
// q qbar initiated
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);
ScalarWaveFunction higgs(meMomenta()[4],mePartonData()[4],1.,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 = qqME(q1,q2,q3,q4,higgs,0);
}
return me*sHat()*UnitRemoval::InvE2;
}
double MEPP2QQHiggs::ggME(vector<VectorWaveFunction> &g1,
vector<VectorWaveFunction> &g2,
vector<SpinorBarWaveFunction> & q,
vector<SpinorWaveFunction> & qbar,
ScalarWaveFunction & hwave,
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,
PDT::Spin0));
// calculate the matrix element
double output(0.),sumflow[2]={0.,0.};
double sumdiag[8]={0.,0.,0.,0.,0.,0.,0.,0.};
Complex diag[8],flow[2];
VectorWaveFunction interv;
SpinorWaveFunction inters,QBoff;
SpinorBarWaveFunction intersb,Qoff;
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) {
Qoff = QQHVertex_->evaluate(mt,3,q[ohel1].particle(),
q[ohel1],hwave,mass);
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
QBoff = QQHVertex_->evaluate(mt,3,qbar[ohel2].particle(),
qbar[ohel2],hwave,mass);
// 1st diagram
inters = QQGVertex_->evaluate(mt,1,qbar[ohel2].particle(),
qbar[ohel2],g2[ihel2],mass);
diag[0] = QQGVertex_->evaluate(mt,inters,Qoff,g1[ihel1]);
// 2nd diagram
intersb = QQGVertex_->evaluate(mt,1,q[ohel1].particle(),
q[ohel1],g1[ihel1],mass);
diag[1] = QQHVertex_->evaluate(mt,inters,intersb,hwave);
// 3rd diagram
diag[2] = QQGVertex_->evaluate(mt,QBoff,intersb,g2[ihel2]);
// 4th diagram
inters = QQGVertex_->evaluate(mt,1,qbar[ohel2].particle(),
qbar[ohel2],g1[ihel1],mass);
diag[3] = QQGVertex_->evaluate(mt,inters,Qoff,g2[ihel2]);
// 5th diagram
intersb = QQGVertex_->evaluate(mt,1,q[ohel1].particle(),
q[ohel1],g2[ihel2],mass);
diag[4] = QQHVertex_->evaluate(mt,inters,intersb,hwave);
// 6th diagram
diag[5] = QQGVertex_->evaluate(mt,QBoff,intersb,g1[ihel1]);
// 7th diagram
diag[6] = QQGVertex_->evaluate(mt,qbar[ohel2],Qoff ,interv);
// 8th diagram
diag[7] = QQGVertex_->evaluate(mt,QBoff ,q[ohel1],interv);
// colour flows
flow[0]=diag[0]+diag[1]+diag[2]+(diag[6]+diag[7]);
flow[1]=diag[3]+diag[4]+diag[5]-(diag[6]+diag[7]);
// sums
for(unsigned int ix=0;ix<8;++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,ohel2,0)=flow[iflow-1];
}
}
}
}
// select a colour flow
flow_ = 1 + UseRandom::rnd2(sumflow[0],sumflow[1]);
if(flow_==1) sumdiag[0]=sumdiag[1]=sumdiag[2]=0.;
else sumdiag[3]=sumdiag[4]=sumdiag[5]=0.;
// select a diagram from that flow
double prob = UseRandom::rnd();
for(unsigned int ix=0;ix<8;++ix) {
if(prob<=sumdiag[ix]) {
diagram_=1+ix;
break;
}
prob -= sumdiag[ix];
}
// final part of colour and spin factors
return output/48.;
}
double MEPP2QQHiggs::qqME(vector<SpinorWaveFunction> & q1,
vector<SpinorBarWaveFunction> & q2,
vector<SpinorBarWaveFunction> & q3,
vector<SpinorWaveFunction> & q4,
ScalarWaveFunction & hwave,
unsigned int iflow) const {
// scale
Energy2 mt(scale());
Energy mass = q3[0].mass();
// matrix element to be stored
if(iflow!=0) me_.reset(ProductionMatrixElement(PDT::Spin1Half,PDT::Spin1Half,
PDT::Spin1Half,PDT::Spin1Half,
PDT::Spin0));
// calculate the matrix element
double output(0.),sumdiag[2]={0.,0.};
Complex diag[2];
VectorWaveFunction interv;
SpinorWaveFunction QBoff;
SpinorBarWaveFunction Qoff;
for(unsigned int ihel1=0;ihel1<2;++ihel1) {
for(unsigned int ihel2=0;ihel2<2;++ihel2) {
interv = QQGVertex_->evaluate(mt,5,gluon_,q1[ihel1],q2[ihel2]);
for(unsigned int ohel1=0;ohel1<2;++ohel1) {
Qoff = QQHVertex_->evaluate(mt,3,q3[ohel1].particle(),
q3[ohel1],hwave,mass);
for(unsigned int ohel2=0;ohel2<2;++ohel2) {
QBoff = QQHVertex_->evaluate(mt,3,q4[ohel2].particle(),
q4[ohel2],hwave,mass);
// 1st diagram
diag[0] = QQGVertex_->evaluate(mt,q4[ohel2],Qoff,interv);
// 2nd diagram
diag[1] = QQGVertex_->evaluate(mt,QBoff,q3[ohel1],interv);
// sum of diagrams
for(unsigned int ix=0;ix<2;++ix) sumdiag[ix] += norm(diag[ix]);
diag[0] += diag[1];
output += norm(diag[0]);
if(iflow!=0) me_(ihel1,ihel2,ohel1,ohel2,0) = diag[0];
}
}
}
}
// only 1 colour flow
flow_=1;
// select a diagram
diagram_ = 9+UseRandom::rnd2(sumdiag[0],sumdiag[1]);
// final part of colour and spin factors
return output/18.;
}
Selector<const ColourLines *>
MEPP2QQHiggs::colourGeometries(tcDiagPtr diag) const {
// colour lines for gg -> Q Qbar H
static const ColourLines cgg[10]=
{ColourLines("1 4 5, -1 -2 3 , -3 -6 "),
ColourLines("1 5 , -1 -2 -3 4, -4 -6 "),
ColourLines("1 4 , -1 -2 3 , -3 -5 -6"),
ColourLines("3 4 5, 1 2 -3 , -1 -6 "),
ColourLines("4 5 , 1 2 3 -4, -1 -6"),
ColourLines("3 4 , 1 2 -3 , -1 -5 -6"),
ColourLines("1 3 4 5, -1 2, -2 -3 -6"),
ColourLines("2 3 4 5, 1 -2, -1 -3 -6"),
ColourLines("1 3 4, -1 2, -2 -3 -5 -6"),
ColourLines("2 3 4, 1 -2, -1 -3 -5 -6")};
// colour lines for q qbar -> Q Qbar H
static const ColourLines cqq[2]=
{ColourLines("1 3 4 5, -2 -3 -6"),
ColourLines("1 3 4 , -2 -3 -5 -6")};
// select the colour flow (as all ready picked just insert answer)
Selector<const ColourLines *> sel;
switch(abs(diag->id())) {
// gg -> q qbar subprocess
case 1: case 2: case 3: case 4: case 5: case 6:
sel.insert(1.0, &cgg[abs(diag->id())-1]);
break;
case 7:
sel.insert(1.0, &cgg[5 + flow_]);
break;
case 8:
sel.insert(1.0, &cgg[7 + flow_]);
break;
// q qbar -> q qbar subprocess
case 9: case 10:
sel.insert(1.0, &cqq[abs(diag->id())-9]);
break;
}
return sel;
}
Selector<MEBase::DiagramIndex>
MEPP2QQHiggs::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;
}
void MEPP2QQHiggs::constructVertex(tSubProPtr sub) {
// extract the particles in the hard process
ParticleVector hard;
hard.push_back(sub->incoming().first);
hard.push_back(sub->incoming().second);
for(unsigned int ix=0;ix<3;++ix) hard.push_back(sub->outgoing()[ix]);
// identify the process and calculate the matrix element
if(hard[0]->id()<0) swap(hard[0],hard[1]);
if(hard[2]->id()==ParticleID::h0) swap(hard[2],hard[4]);
if(hard[3]->id()==ParticleID::h0) swap(hard[3],hard[4]);
if(hard[2]->id()<0) swap(hard[2],hard[3]);
if(hard[0]->id()==ParticleID::g) {
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);
ScalarWaveFunction hwave( hard[4],outgoing,true);
g1[1]=g1[2];g2[1]=g2[2];
ggME(g1,g2,q,qbar,hwave,flow_);
}
// q qbar -> Q Qbar Higgs
else {
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);
ScalarWaveFunction hwave( hard[4],outgoing,true);
qqME(q1,q2,q3,q4,hwave,flow_);
}
// 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<5;++ix)
hard[ix]->spinInfo()->productionVertex(hardvertex);
}
double MEPP2QQHiggs::getCosTheta(double ctmin, double ctmax, double r) {
double cth = 0.0;
static const double eps = 1.0e-6;
if ( 1.0 + ctmin <= eps && 1.0 - ctmax <= eps ) {
cth = ctmin + r*(ctmax-ctmin);
jacobian(jacobian()*(ctmax - ctmin));
} else if ( 1.0 + ctmin <= eps ) {
cth = 1.0 - (1.0 - ctmax)*pow((1.0 - ctmin)/(1.0 - ctmax), r);
jacobian(jacobian()*log((1.0 - ctmin)/(1.0 - ctmax))*(1.0 - cth));
} else if ( 1.0 - ctmax <= eps ) {
cth = -1.0 + (1.0 + ctmin)*pow((1.0 + ctmax)/(1.0 + ctmin), r);
jacobian(jacobian()*log((1.0 + ctmax)/(1.0 + ctmin))*(1.0 + cth));
} else {
double zmin = 0.5*(1.0 - ctmax);
double zmax = 0.5*(1.0 - ctmin);
double A1 = -ctmin/(zmax*(1.0-zmax));
double A0 = -ctmax/(zmin*(1.0-zmin));
double A = r*(A1 - A0) + A0;
double z = A < 2.0? 2.0/(sqrt(sqr(A) + 4.0) + 2 - A):
0.5*(A - 2.0 + sqrt(sqr(A) + 4.0))/A;
cth = 1.0 - 2.0*z;
jacobian(jacobian()*2.0*(A1 - A0)*sqr(z)*sqr(1.0 - z)/(sqr(z) + sqr(1.0 - z)));
}
return cth;
}

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