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diff --git a/MatrixElement/Hadron/MEPP2Higgs.cc b/MatrixElement/Hadron/MEPP2Higgs.cc
--- a/MatrixElement/Hadron/MEPP2Higgs.cc
+++ b/MatrixElement/Hadron/MEPP2Higgs.cc
@@ -1,1633 +1,1629 @@
// -*- C++ -*-
//
// MEPP2Higgs.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 MEPP2Higgs class.
//
#include "MEPP2Higgs.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Interface/Switch.h"
#include "ThePEG/Interface/Reference.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/PDT/EnumParticles.h"
#include "ThePEG/MatrixElement/Tree2toNDiagram.h"
#include "ThePEG/Handlers/StandardXComb.h"
#include "ThePEG/Cuts/Cuts.h"
#include "Herwig/MatrixElement/HardVertex.h"
#include "Herwig/Models/StandardModel/StandardModel.h"
#include "Herwig/Utilities/Maths.h"
#include "Herwig/Shower/Base/ShowerProgenitor.h"
#include "Herwig/Shower/Base/ShowerTree.h"
#include "Herwig/Shower/Base/Branching.h"
#include "Herwig/Shower/Base/HardTree.h"
using namespace Herwig;
const complex<Energy2>
MEPP2Higgs::epsi_ = complex<Energy2>(ZERO,-1.e-10*GeV2);
MEPP2Higgs::MEPP2Higgs() : scaleopt_(1), mu_F_(100.*GeV),
shapeOption_(2), processOption_(1),
minFlavour_(4), maxFlavour_(5),
mh_(ZERO), wh_(ZERO),
minLoop_(6),maxLoop_(6),massOption_(0),
mu_R_opt_(1),mu_F_opt_(1),
channelwgtA_(0.45),channelwgtB_(0.15),
ggPow_(1.6), qgPow_(1.6), enhance_(1.1),
nover_(0), ntry_(0), ngen_(0), maxwgt_(0.),
power_(2.0), pregg_(7.), preqg_(3.),
pregqbar_(3.), minpT_(2.*GeV),
spinCorrelations_(true)
{}
ClassDescription<MEPP2Higgs> MEPP2Higgs::initMEPP2Higgs;
// Definition of the static class description member.
void MEPP2Higgs::persistentOutput(PersistentOStream & os) const {
os << HGGVertex_ << HFFVertex_ << shapeOption_ << processOption_
<< minFlavour_ << maxFlavour_ << hmass_ << ounit(mh_,GeV)
<< ounit(wh_,GeV) << minLoop_ << maxLoop_ << massOption_
<< alpha_ << prefactor_ << power_ << pregg_ << preqg_
<< pregqbar_ << ounit( minpT_, GeV ) << ggPow_ << qgPow_
<< enhance_ << channelwgtA_ << channelwgtB_ << channelWeights_
<< mu_R_opt_ << mu_F_opt_ << spinCorrelations_;
}
void MEPP2Higgs::persistentInput(PersistentIStream & is, int) {
is >> HGGVertex_ >> HFFVertex_ >> shapeOption_ >> processOption_
>> minFlavour_ >> maxFlavour_ >> hmass_ >> iunit(mh_,GeV)
>> iunit(wh_,GeV) >> minLoop_ >> maxLoop_ >> massOption_
>> alpha_ >> prefactor_ >> power_ >> pregg_ >> preqg_
>> pregqbar_ >> iunit( minpT_, GeV ) >> ggPow_ >> qgPow_
>> enhance_ >> channelwgtA_ >> channelwgtB_ >> channelWeights_
>> mu_R_opt_ >> mu_F_opt_ >> spinCorrelations_;
}
void MEPP2Higgs::Init() {
static ClassDocumentation<MEPP2Higgs> documentation
("The MEPP2Higgs class implements the matrix elements for"
" Higgs production (with decay H->W-W+) in hadron-hadron collisions"
" including the generation of additional hard QCD radiation in "
"gg to h0 processes in the POWHEG scheme",
"Hard QCD radiation for $gg\\to h^0$ processes in the"
" POWHEG scheme \\cite{Hamilton:2009za}.",
"%\\cite{Hamilton:2009za}\n"
"\\bibitem{Hamilton:2009za}\n"
" K.~Hamilton, P.~Richardson and J.~Tully,\n"
" ``A Positive-Weight Next-to-Leading Order Monte Carlo Simulation for Higgs\n"
" Boson Production,''\n"
" JHEP {\\bf 0904}, 116 (2009)\n"
" [arXiv:0903.4345 [hep-ph]].\n"
" %%CITATION = JHEPA,0904,116;%%\n");
static Switch<MEPP2Higgs,unsigned int> interfaceFactorizationScaleOption
("FactorizationScaleOption",
"Option for the choice of factorization scale",
&MEPP2Higgs::scaleopt_, 1, false, false);
static SwitchOption interfaceDynamic
(interfaceFactorizationScaleOption,
"Dynamic",
"Dynamic factorization scale equal to the current sqrt(sHat())",
1);
static SwitchOption interfaceFixed
(interfaceFactorizationScaleOption,
"Fixed",
"Use a fixed factorization scale set with FactorizationScaleValue",
2);
static Parameter<MEPP2Higgs,Energy> interfaceFactorizationScaleValue
("FactorizationScaleValue",
"Value to use in the event of a fixed factorization scale",
&MEPP2Higgs::mu_F_, GeV, 100.0*GeV, 50.0*GeV, 500.0*GeV,
true, false, Interface::limited);
static Reference<MEPP2Higgs,ShowerAlpha> interfaceCoupling
("Coupling",
"Pointer to the object to calculate the coupling for the correction",
&MEPP2Higgs::alpha_, false, false, true, false, false);
static Switch<MEPP2Higgs,unsigned int> interfaceShapeOption
("ShapeScheme",
"Option for the treatment of the Higgs resonance shape",
&MEPP2Higgs::shapeOption_, 1, false, false);
static SwitchOption interfaceStandardShapeFixed
(interfaceShapeOption,
"FixedBreitWigner",
"Breit-Wigner s-channel resonanse",
1);
static SwitchOption interfaceStandardShapeRunning
(interfaceShapeOption,
"MassGenerator",
"Use the mass generator to give the shape",
2);
static Switch<MEPP2Higgs,unsigned int> interfaceProcess
("Process",
"Which subprocesses to include",
&MEPP2Higgs::processOption_, 1, false, false);
static SwitchOption interfaceProcessAll
(interfaceProcess,
"All",
"Include all subprocesses",
1);
static SwitchOption interfaceProcess1
(interfaceProcess,
"qqbar",
"Only include the incoming q qbar subprocess",
2);
static SwitchOption interfaceProcessgg
(interfaceProcess,
"gg",
"Only include the incoming gg subprocess",
3);
static Parameter<MEPP2Higgs,unsigned int> interfaceMinimumInLoop
("MinimumInLoop",
"The minimum flavour of the quarks to include in the loops",
&MEPP2Higgs::minLoop_, 6, 5, 6,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,unsigned int> interfaceMaximumInLoop
("MaximumInLoop",
"The maximum flavour of the quarks to include in the loops",
&MEPP2Higgs::maxLoop_, 6, 5, 6,
false, false, Interface::limited);
static Switch<MEPP2Higgs,unsigned int> interfaceMassOption
("MassOption",
"Option for the treatment of the masses in the loop diagrams",
&MEPP2Higgs::massOption_, 0, false, false);
static SwitchOption interfaceMassOptionFull
(interfaceMassOption,
"Full",
"Include the full mass dependence",
0);
static SwitchOption interfaceMassOptionLarge
(interfaceMassOption,
"Large",
"Use the heavy mass limit",
1);
static Parameter<MEPP2Higgs,int> interfaceMinimumFlavour
("MinimumFlavour",
"The minimum flavour of the incoming quarks in the hard process",
&MEPP2Higgs::minFlavour_, 4, 3, 5,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,int> interfaceMaximumFlavour
("MaximumFlavour",
"The maximum flavour of the incoming quarks in the hard process",
&MEPP2Higgs::maxFlavour_, 5, 3, 5,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfaceQGChannelWeight
("QGChannelWeight",
"The relative weights of the g g and q g channels for selection."
" This is a technical parameter for the phase-space generation and "
"should not affect the results only the efficiency and fraction"
" of events with weight > 1.",
&MEPP2Higgs::channelwgtA_, 0.45, 0., 1.e10,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfaceQbarGChannelWeight
("QbarGChannelWeight",
"The relative weights of the g g abd qbar g channels for selection."
" This is a technical parameter for the phase-space generation and "
"should not affect the results only the efficiency and fraction",
&MEPP2Higgs::channelwgtB_, 0.15, 0., 1.e10,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfaceGGPower
("GGPower",
"Power for the phase-space sampling of the gg channel",
&MEPP2Higgs::ggPow_, 1.6, 1.0, 3.0,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfaceQGPower
("QGPower",
"Power for the phase-space sampling of the qg and qbarg channels",
&MEPP2Higgs::qgPow_, 1.6, 1.0, 3.0,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfaceEnhancementFactor
("InitialEnhancementFactor",
"The enhancement factor for initial-state radiation in the shower to ensure"
" the weight for the matrix element correction is less than one.",
&MEPP2Higgs::enhance_, 1.1, 1.0, 10.0,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfacePower
("Power",
"The power for the sampling of the matrix elements",
&MEPP2Higgs::power_, 2.0, 1.0, 10.0,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfacePrefactorgg
("Prefactorgg",
"The prefactor for the sampling of the q qbar channel",
&MEPP2Higgs::pregg_, 7.0, 0.0, 1000.0,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfacePrefactorqg
("Prefactorqg",
"The prefactor for the sampling of the q g channel",
&MEPP2Higgs::preqg_, 3.0, 0.0, 1000.0,
false, false, Interface::limited);
static Parameter<MEPP2Higgs,double> interfacePrefactorgqbar
("Prefactorgqbar",
"The prefactor for the sampling of the g qbar channel",
&MEPP2Higgs::pregqbar_, 3.0, 0.0, 1000.0,
false, false, Interface::limited);
static Parameter<MEPP2Higgs, Energy> interfacePtMin
("minPt",
"The pt cut on hardest emision generation"
"2*(1-Beta)*exp(-sqr(intrinsicpT/RMS))/sqr(RMS)",
&MEPP2Higgs::minpT_, GeV, 2.*GeV, ZERO, 100000.0*GeV,
false, false, Interface::limited);
static Switch<MEPP2Higgs,unsigned int> interface_mu_R_Option
("mu_R_Option",
"Option to use pT or mT as the scale in alphaS",
&MEPP2Higgs::mu_R_opt_, 1, false, false);
static SwitchOption interface_mu_R_Option_mT
(interface_mu_R_Option,
"mT",
"Use mT as the scale in alpha_S",
0);
static SwitchOption interface_mu_R_Option_pT
(interface_mu_R_Option,
"pT",
"Use pT as the scale in alpha_S",
1);
static Switch<MEPP2Higgs,unsigned int> interface_mu_F_Option
("mu_F_Option",
"Option to use pT or mT as the factorization scale in the PDFs",
&MEPP2Higgs::mu_F_opt_, 1, false, false);
static SwitchOption interface_mu_F_Option_mT
(interface_mu_F_Option,
"mT",
"Use mT as the scale in the PDFs",
0);
static SwitchOption interface_mu_F_Option_pT
(interface_mu_F_Option,
"pT",
"Use pT as the scale in the PDFs",
1);
static Switch<MEPP2Higgs,bool> interfaceSpinCorrelations
("SpinCorrelations",
"Which on/off spin correlations in the hard process",
&MEPP2Higgs::spinCorrelations_, true, false, false);
static SwitchOption interfaceSpinCorrelationsYes
(interfaceSpinCorrelations,
"Yes",
"Switch correlations on",
true);
static SwitchOption interfaceSpinCorrelationsNo
(interfaceSpinCorrelations,
"No",
"Switch correlations off",
false);
}
void MEPP2Higgs::doinit() {
HwMEBase::doinit();
// get the vertex pointers from the SM object
tcHwSMPtr theSM = dynamic_ptr_cast<tcHwSMPtr>(standardModel());
// do the initialisation
if(!theSM) {
throw InitException() << "Wrong type of StandardModel object in MEPP2Higgs::doinit(),"
<< " the Herwig version must be used"
<< Exception::runerror;
}
HGGVertex_ = theSM->vertexHGG();
HFFVertex_ = theSM->vertexFFH();
// get the mass generator for the higgs
PDPtr h0 = getParticleData(ParticleID::h0);
mh_ = h0->mass();
wh_ = h0->generateWidth(mh_);
if(h0->massGenerator()) {
hmass_=dynamic_ptr_cast<GenericMassGeneratorPtr>(h0->massGenerator());
}
if(shapeOption_==2&&!hmass_) throw InitException()
<< "If using the mass generator for the line shape in MEPP2Higgs::doinit()"
<< "the mass generator must be an instance of the GenericMassGenerator class"
<< Exception::runerror;
// stuff for the ME correction
double total = 1.+channelwgtA_+channelwgtB_;
channelWeights_.push_back(1./total);
channelWeights_.push_back(channelWeights_.back()+channelwgtA_/total);
channelWeights_.push_back(channelWeights_.back()+channelwgtB_/total);
// insert the different prefactors in the vector for easy look up
prefactor_.push_back(pregg_);
prefactor_.push_back(preqg_);
prefactor_.push_back(preqg_);
prefactor_.push_back(pregqbar_);
prefactor_.push_back(pregqbar_);
}
void MEPP2Higgs::dofinish() {
HwMEBase::dofinish();
if(ntry_==0) return;
generator()->log() << "MEPP2Higgs when applying the hard correction "
<< "generated " << ntry_ << " trial emissions of which "
<< ngen_ << " were accepted\n";
if(nover_==0) return;
generator()->log() << "MEPP2Higgs when applying the hard correction "
<< nover_ << " weights larger than one were generated of which"
<< " the largest was " << maxwgt_ << "\n";
}
unsigned int MEPP2Higgs::orderInAlphaS() const {
return 2;
}
unsigned int MEPP2Higgs::orderInAlphaEW() const {
return 1;
}
Energy2 MEPP2Higgs::scale() const {
return scaleopt_ == 1 ? sHat() : sqr(mu_F_);
}
int MEPP2Higgs::nDim() const {
return 0;
}
bool MEPP2Higgs::generateKinematics(const double *) {
Lorentz5Momentum pout = meMomenta()[0] + meMomenta()[1];
pout.rescaleMass();
meMomenta()[2].setMass(pout.mass());
meMomenta()[2] = LorentzMomentum(pout.x(),pout.y(),pout.z(),pout.t());
jacobian(1.0);
// check whether it passes all the cuts: returns true if it does
vector<LorentzMomentum> out(1,meMomenta()[2]);
tcPDVector tout(1,mePartonData()[2]);
return lastCuts().passCuts(tout, out, mePartonData()[0], mePartonData()[1]);
}
void MEPP2Higgs::getDiagrams() const {
tcPDPtr h0=getParticleData(ParticleID::h0);
// gg -> H process
if(processOption_==1||processOption_==3) {
tcPDPtr g=getParticleData(ParticleID::g);
add(new_ptr((Tree2toNDiagram(2), g, g, 1, h0, -1)));
}
// q qbar -> H processes
if(processOption_==1||processOption_==2) {
for ( int i = minFlavour_; i <= maxFlavour_; ++i ) {
tcPDPtr q = getParticleData(i);
tcPDPtr qb = q->CC();
add(new_ptr((Tree2toNDiagram(2), q, qb, 1, h0, -2)));
}
}
}
CrossSection MEPP2Higgs::dSigHatDR() const {
using Constants::pi;
InvEnergy2 bwfact;
if(shapeOption_==1) {
bwfact = mePartonData()[2]->generateWidth(sqrt(sHat()))*sqrt(sHat())/pi/
(sqr(sHat()-sqr(mh_))+sqr(mh_*wh_));
}
else {
bwfact = hmass_->BreitWignerWeight(sqrt(sHat()));
}
double cs = me2() * jacobian() * pi * double(UnitRemoval::E4 * bwfact/sHat());
return UnitRemoval::InvE2 * sqr(hbarc) * cs;
}
double MEPP2Higgs::me2() const {
double output(0.0);
ScalarWaveFunction hout(meMomenta()[2],mePartonData()[2],outgoing);
// Safety code to garantee the reliable behaviour of Higgs shape limits
// (important for heavy and broad Higgs resonance).
Energy hmass = meMomenta()[2].m();
tcPDPtr h0 = mePartonData()[2];
Energy mass = h0->mass();
Energy halfmass = .5*mass;
if (.0*GeV > hmass) return 0.0;
// stricly speaking the condition is applicable if
// h0->widthUpCut() == h0->widthLoCut()...
if (h0->widthLoCut() > halfmass) {
if ( mass + h0->widthUpCut() < hmass ||
mass - h0->widthLoCut() > hmass ) return 0.0;
}
else {
if (mass + halfmass < hmass || halfmass > hmass) return 0.0;
}
if (mePartonData()[0]->id() == ParticleID::g &&
mePartonData()[1]->id() == ParticleID::g) {
VectorWaveFunction gin1(meMomenta()[0],mePartonData()[0],incoming);
VectorWaveFunction gin2(meMomenta()[1],mePartonData()[1],incoming);
vector<VectorWaveFunction> g1,g2;
for(unsigned int i = 0; i < 2; ++i) {
gin1.reset(2*i);
g1.push_back(gin1);
gin2.reset(2*i);
g2.push_back(gin2);
}
output = ggME(g1,g2,hout,false);
}
else {
if (mePartonData()[0]->id() == -mePartonData()[1]->id()) {
SpinorWaveFunction qin (meMomenta()[0],mePartonData()[0],incoming);
SpinorBarWaveFunction qbin(meMomenta()[1],mePartonData()[1],incoming);
vector<SpinorWaveFunction> fin;
vector<SpinorBarWaveFunction> ain;
for (unsigned int i = 0; i < 2; ++i) {
qin.reset(i);
fin.push_back(qin);
qbin.reset(i);
ain.push_back(qbin);
}
output = qqME(fin,ain,hout,false);
}
else assert(false);
}
return output;
}
Selector<MEBase::DiagramIndex> MEPP2Higgs::diagrams(const DiagramVector & diags) const {
Selector<DiagramIndex> sel;
for (DiagramIndex i = 0; i < diags.size(); ++i)
sel.insert(1.0, i);
return sel;
}
Selector<const ColourLines *> MEPP2Higgs::colourGeometries(tcDiagPtr diag) const {
// colour lines
static const ColourLines line1("1 -2,2 -1");
static const ColourLines line2("1 -2");
// select the colour flow
Selector<const ColourLines *> sel;
if (diag->id() == -1) {
sel.insert(1.0, &line1);
} else {
sel.insert(1.0, &line2);
}
// return the answer
return sel;
}
void MEPP2Higgs::constructVertex(tSubProPtr sub) {
if(!spinCorrelations_) return;
// 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]);
if(hard[0]->id() < hard[1]->id()) {
swap(hard[0],hard[1]);
}
// identify the process and calculate the matrix element
if(hard[0]->id() == ParticleID::g && hard[1]->id() == ParticleID::g) {
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);
ScalarWaveFunction hout(hard[2],outgoing,true);
g1[1] = g1[2];
g2[1] = g2[2];
ggME(g1,g2,hout,true);
}
else {
vector<SpinorWaveFunction> q1;
vector<SpinorBarWaveFunction> q2;
SpinorWaveFunction (q1,hard[0],incoming,false,true);
SpinorBarWaveFunction (q2,hard[1],incoming,false,true);
ScalarWaveFunction hout(hard[2],outgoing,true);
qqME(q1,q2,hout,true);
}
// 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 i = 0; i < 3; ++i)
hard[i]->spinInfo()->productionVertex(hardvertex);
}
double MEPP2Higgs::ggME(vector<VectorWaveFunction> g1,
vector<VectorWaveFunction> g2,
ScalarWaveFunction & in,
bool calc) const {
ProductionMatrixElement newme(PDT::Spin1,PDT::Spin1,PDT::Spin0);
Energy2 s(sHat());
double me2(0.0);
for(int i = 0; i < 2; ++i) {
for(int j = 0; j < 2; ++j) {
Complex diag = HGGVertex_->evaluate(s,g1[i],g2[j],in);
me2 += norm(diag);
if(calc) newme(2*i, 2*j, 0) = diag;
}
}
if(calc) me_.reset(newme);
// initial colour and spin factors: colour -> (8/64) and spin -> (1/4)
return me2/32.;
}
double MEPP2Higgs::qqME(vector<SpinorWaveFunction> & fin,
vector<SpinorBarWaveFunction> & ain,
ScalarWaveFunction & in,
bool calc) const {
ProductionMatrixElement newme(PDT::Spin1Half,PDT::Spin1Half,PDT::Spin0);
Energy2 s(scale());
double me2(0.0);
for(int i = 0; i < 2; ++i) {
for(int j = 0; j < 2; ++j) {
Complex diag = HFFVertex_->evaluate(s,fin[i],ain[j],in);
me2+=norm(diag);
if(calc) newme(i, j, 0) = diag;
}
}
if(calc) me_.reset(newme);
// final colour/spin factors
return me2/12.;
}
void MEPP2Higgs::applyHardMatrixElementCorrection(ShowerTreePtr tree) {
useMe();
assert(tree->outgoingLines().size()==1);
if(tree->incomingLines().begin()->second->id()!=ParticleID::g) return;
// get gluons and Higgs
// get the gluons
map<ShowerProgenitorPtr,ShowerParticlePtr>::const_iterator cit;
ShowerParticleVector incoming;
vector<tcBeamPtr> beams;
for(cit=tree->incomingLines().begin();cit!=tree->incomingLines().end();++cit) {
incoming.push_back(cit->first->progenitor());
beams.push_back(cit->first->beam());
}
if(incoming[0]->momentum().z()<ZERO) {
swap(incoming[0],incoming[1]);
swap(beams[0],beams[1]);
}
// get the Higgs
PPtr higgs;
higgs=tree->outgoingLines().begin()->first->copy();
// calculate the momenta
unsigned int iemit,itype;
vector<Lorentz5Momentum> pnew;
pair<double,double> xnew;
// if not accepted return
tPDPtr out;
if(!applyHard(incoming,beams,higgs,iemit,itype,pnew,xnew,out)) return;
// if applying ME correction create the new particles
if(itype==0) {
// ensure gluon can be put on shell
Lorentz5Momentum ptest(pnew[2]);
if(ptest.boost(-(pnew[0]+pnew[1]).boostVector()).e() <
getParticleData(ParticleID::g)->constituentMass()) return;
// create the new gluon
PPtr newg= getParticleData(ParticleID::g)->produceParticle(pnew[2]);
PPtr newg1,newg2;
ColinePtr col;
bool colour = UseRandom::rndbool();
// make the new particles
if(iemit==0) {
newg1 = incoming[0]->dataPtr()->produceParticle(pnew[0]);
if(colour) {
col = incoming[0]->colourLine();
incoming[0]->antiColourLine()->addAntiColoured(newg1);
}
else {
col = incoming[0]->antiColourLine();
incoming[0]->colourLine()->addColoured(newg1);
}
newg2 = new_ptr(Particle(*incoming[1]));
col->removeColoured(newg2,colour);
newg2->set5Momentum(pnew[1]);
}
else {
newg2 = incoming[1]->dataPtr()->produceParticle(pnew[1]);
if(colour) {
col= incoming[1]->antiColourLine();
incoming[1]->colourLine()->addColoured(newg2);
}
else {
col= incoming[1]->colourLine();
incoming[1]->antiColourLine()->addAntiColoured(newg2);
}
newg1 = new_ptr(Particle(*incoming[0]));
col->removeColoured(newg1,!colour);
newg1->set5Momentum(pnew[0]);
}
// set the colour lines
ColinePtr newline=new_ptr(ColourLine());
if(iemit==0) {
newline->addColoured(newg1,!colour);
newline->addColoured(newg ,!colour);
col ->addColoured(newg , colour);
col ->addColoured(newg2, colour);
}
else {
newline->addColoured(newg2, colour);
newline->addColoured(newg , colour);
col ->addColoured(newg ,!colour);
col ->addColoured(newg1,!colour);
}
// change the existing gluons
PPtr orig;
for(cit=tree->incomingLines().begin();cit!=tree->incomingLines().end();++cit) {
// remove old particles from colour line
ColinePtr l1=cit->first->copy()-> colourLine();
ColinePtr l2=cit->first->copy()->antiColourLine();
l1->removeColoured (cit->first->copy() );
l1->removeColoured (cit->first->progenitor());
l2->removeAntiColoured(cit->first->copy() );
l2->removeAntiColoured(cit->first->progenitor());
if(cit->first->progenitor()->momentum().z()/newg1->momentum().z()>0) {
// insert new particles
cit->first->copy(newg1);
ShowerParticlePtr sp(new_ptr(ShowerParticle(*newg1,1,false)));
sp->x(xnew.first);
cit->first->progenitor(sp);
tree->incomingLines()[cit->first]=sp;
cit->first->perturbative(iemit!=0);
if(iemit==0) orig=cit->first->original();
}
else {
// insert new particles
cit->first->copy(newg2);
ShowerParticlePtr sp(new_ptr(ShowerParticle(*newg2,1,false)));
sp->x(xnew.second);
cit->first->progenitor(sp);
tree->incomingLines()[cit->first]=sp;
cit->first->perturbative(iemit==0);
if(iemit==1) orig=cit->first->original();
}
}
// fix the momentum of the higgs
map<ShowerProgenitorPtr,tShowerParticlePtr>::const_iterator
cjt=tree->outgoingLines().begin();
Boost boostv=cjt->first->progenitor()->momentum().findBoostToCM();
LorentzRotation trans(pnew[3].boostVector());
trans *=LorentzRotation(boostv);
cjt->first->progenitor()->transform(trans);
cjt->first->copy()->transform(trans);
tree->hardMatrixElementCorrection(true);
// add the gluon
ShowerParticlePtr sg=new_ptr(ShowerParticle(*newg,1,true));
ShowerProgenitorPtr gluon=new_ptr(ShowerProgenitor(orig,newg,sg));
gluon->perturbative(false);
tree->outgoingLines().insert(make_pair(gluon,sg));
}
else if(itype==1) {
// ensure outgoing quark can be put on-shell
Lorentz5Momentum ptest(pnew[2]);
if(ptest.boost(-(pnew[0]+pnew[1]).boostVector()).e() <
out->constituentMass()) return;
// create the new particles
PPtr newqout = out->produceParticle(pnew[2]);
PPtr newqin,newg;
if(iemit==0) {
newqin = out ->produceParticle(pnew[0]);
newg = new_ptr(Particle(*incoming[1]));
newg->set5Momentum(pnew[1]);
incoming[0]->colourLine() ->addColoured(newqin);
incoming[0]->antiColourLine()->addColoured(newqout);
}
else {
newg = new_ptr(Particle(*incoming[0]));
newg->set5Momentum(pnew[0]);
newqin = out ->produceParticle(pnew[1]);
incoming[1]->colourLine() ->addColoured(newqin);
incoming[1]->antiColourLine()->addColoured(newqout);
}
// change the existing incoming partons
PPtr orig;
for(cit=tree->incomingLines().begin();cit!=tree->incomingLines().end();++cit) {
// remove old particles from colour line
ColinePtr l1=cit->first->copy()-> colourLine();
ColinePtr l2=cit->first->copy()->antiColourLine();
l1->removeColoured (cit->first->copy() );
l1->removeColoured (cit->first->progenitor());
l2->removeAntiColoured(cit->first->copy() );
l2->removeAntiColoured(cit->first->progenitor());
if(cit->first->progenitor()->momentum().z()/newqin->momentum().z()>0.) {
// insert new particles
cit->first->copy(newqin);
ShowerParticlePtr sp(new_ptr(ShowerParticle(*newqin,1,false)));
sp->x(iemit==0 ? xnew.first : xnew.second );
cit->first->progenitor(sp);
tree->incomingLines()[cit->first]=sp;
cit->first->perturbative(false);
orig=cit->first->original();
}
else {
// insert new particles
cit->first->copy(newg);
ShowerParticlePtr sp(new_ptr(ShowerParticle(*newg,1,false)));
sp->x(iemit==1 ? xnew.first : xnew.second );
cit->first->progenitor(sp);
tree->incomingLines()[cit->first]=sp;
cit->first->perturbative(true);
}
}
// fix the momentum of the higgs
map<ShowerProgenitorPtr,tShowerParticlePtr>::const_iterator
cjt=tree->outgoingLines().begin();
Boost boostv=cjt->first->progenitor()->momentum().findBoostToCM();
LorentzRotation trans(pnew[3].boostVector());
trans *=LorentzRotation(boostv);
cjt->first->progenitor()->transform(trans);
cjt->first->copy()->transform(trans);
tree->hardMatrixElementCorrection(true);
// add the outgoing quark
ShowerParticlePtr sout=new_ptr(ShowerParticle(*newqout,1,true));
ShowerProgenitorPtr out=new_ptr(ShowerProgenitor(orig,newqout,sout));
out->perturbative(false);
tree->outgoingLines().insert(make_pair(out,sout));
}
else if(itype==2) {
// ensure outgoing antiquark can be put on-shell
Lorentz5Momentum ptest(pnew[2]);
if(ptest.boost(-(pnew[0]+pnew[1]).boostVector()).e() <
incoming[0]->dataPtr()->constituentMass()) return;
// create the new particles
PPtr newqout = out->produceParticle(pnew[2]);
PPtr newqin,newg;
if(iemit==0) {
newqin = out ->produceParticle(pnew[0]);
newg = new_ptr(Particle(*incoming[1]));
newg->set5Momentum(pnew[1]);
incoming[0]->colourLine() ->addAntiColoured(newqout);
incoming[0]->antiColourLine()->addAntiColoured(newqin);
}
else {
newg = new_ptr(Particle(*incoming[0]));
newg->set5Momentum(pnew[0]);
newqin = out ->produceParticle(pnew[1]);
incoming[1]->colourLine() ->addAntiColoured(newqout);
incoming[1]->antiColourLine()->addAntiColoured(newqin);
}
// change the existing incoming partons
PPtr orig;
for(cit=tree->incomingLines().begin();cit!=tree->incomingLines().end();++cit) {
// remove old particles from colour line
ColinePtr l1=cit->first->copy()-> colourLine();
ColinePtr l2=cit->first->copy()->antiColourLine();
l1->removeColoured (cit->first->copy() );
l1->removeColoured (cit->first->progenitor());
l2->removeAntiColoured(cit->first->copy() );
l2->removeAntiColoured(cit->first->progenitor());
if(cit->first->progenitor()->momentum().z()/newqin->momentum().z()>0.) {
// insert new particles
cit->first->copy(newqin);
ShowerParticlePtr sp(new_ptr(ShowerParticle(*newqin,1,false)));
sp->x(iemit==0 ? xnew.first : xnew.second );
cit->first->progenitor(sp);
tree->incomingLines()[cit->first]=sp;
cit->first->perturbative(false);
orig=cit->first->original();
}
else {
// insert new particles
cit->first->copy(newg);
ShowerParticlePtr sp(new_ptr(ShowerParticle(*newg,1,false)));
sp->x(iemit==1 ? xnew.first : xnew.second );
cit->first->progenitor(sp);
tree->incomingLines()[cit->first]=sp;
cit->first->perturbative(true);
}
}
// fix the momentum of the higgs
map<ShowerProgenitorPtr,tShowerParticlePtr>::const_iterator
cjt=tree->outgoingLines().begin();
Boost boostv=cjt->first->progenitor()->momentum().findBoostToCM();
LorentzRotation trans(pnew[3].boostVector());
trans *=LorentzRotation(boostv);
cjt->first->progenitor()->transform(trans);
cjt->first->copy()->transform(trans);
tree->hardMatrixElementCorrection(true);
// add the outgoing antiquark
ShowerParticlePtr sout=new_ptr(ShowerParticle(*newqout,1,true));
ShowerProgenitorPtr out=new_ptr(ShowerProgenitor(orig,newqout,sout));
out->perturbative(false);
tree->outgoingLines().insert(make_pair(out,sout));
}
}
bool MEPP2Higgs::softMatrixElementVeto(ShowerProgenitorPtr initial,
ShowerParticlePtr parent,Branching br) {
if(parent->isFinalState()) return false;
// check if me correction should be applied
long id[2]={initial->id(),parent->id()};
// must have started as a gluon
if(id[0]!=ParticleID::g) return false;
// must be a gluon going into the hard process
if(br.ids[1]!=ParticleID::g) return false;
// get the pT
Energy pT=br.kinematics->pT();
// check if hardest so far
if(pT<initial->highestpT()) return false;
// compute the invariants
double kappa(sqr(br.kinematics->scale())/mh2_),z(br.kinematics->z());
Energy2 shat(mh2_/z*(1.+(1.-z)*kappa)),that(-(1.-z)*kappa*mh2_),uhat(-(1.-z)*shat);
// check which type of process
Energy2 me;
// g g
if(br.ids[0]==ParticleID::g&&br.ids[2]==ParticleID::g) {
double split = 6.*(z/(1.-z)+(1.-z)/z+z*(1.-z));
me = ggME(shat,that,uhat)/split;
}
// q g
else if(br.ids[0] >= 1 && br.ids[0] <= 5 && br.ids[2]==br.ids[0]) {
double split = 4./3./z*(1.+sqr(1.-z));
me = qgME(shat,uhat,that)/split;
}
// qbar g
else if(br.ids[0] <= -1 && br.ids[0] >= -5 && br.ids[2]==br.ids[0]) {
double split = 4./3./z*(1.+sqr(1.-z));
me = qbargME(shat,uhat,that)/split;
}
else {
return false;
}
InvEnergy2 pre = 0.125/Constants::pi/loME()*sqr(mh2_)*that/shat/(shat+uhat);
double wgt = -pre*me/enhance_;
if(wgt<.0||wgt>1.) generator()->log() << "Soft ME correction weight too large or "
<< "negative in MEPP2Higgs::"
<< "softMatrixElementVeto()\n soft weight "
<< " sbar = " << shat/mh2_
<< " tbar = " << that/mh2_
<< "weight = " << wgt << " for "
<< br.ids[0] << " " << br.ids[1] << " "
<< br.ids[2] << "\n";
// if not vetoed
if(UseRandom::rndbool(wgt)) return false;
// otherwise
parent->vetoEmission(br.type,br.kinematics->scale());
return true;
}
HardTreePtr MEPP2Higgs::generateHardest(ShowerTreePtr tree,
vector<ShowerInteraction::Type> inter) {
bool found = false;
// check if generating QCD radiation
for(unsigned int ix=0;ix<inter.size();++ix) {
found |= inter[ix]==ShowerInteraction::QCD;
}
if(!found) return HardTreePtr();
if(tree->incomingLines().begin()->second->id()!=ParticleID::g)
return HardTreePtr();
useMe();
// get the particles to be showered
beams_.clear();
partons_.clear();
// find the incoming particles
ShowerParticleVector incoming;
map<ShowerProgenitorPtr,ShowerParticlePtr>::const_iterator cit;
vector<ShowerProgenitorPtr> particlesToShower;
for( cit = tree->incomingLines().begin();
cit != tree->incomingLines().end(); ++cit ) {
incoming.push_back( cit->first->progenitor() );
beams_.push_back( cit->first->beam() );
partons_.push_back( cit->first->progenitor()->dataPtr() );
particlesToShower.push_back( cit->first );
}
// find the higgs boson
PPtr higgs;
if(tree->outgoingLines().size() == 1) {
higgs = tree->outgoingLines().begin()->first->copy();
}
else {
higgs = tree->outgoingLines().begin()->first->copy()->parents()[0];
}
// calculate the rapidity of the higgs
yh_ = 0.5 * log((higgs->momentum().e()+higgs->momentum().z())/
(higgs->momentum().e()-higgs->momentum().z()));
mass_=higgs->mass();
mh2_ = sqr(mass_);
vector<Lorentz5Momentum> pnew;
int emission_type(-1);
// generate the hard emission and return if no emission
if(!getEvent(pnew,emission_type)) {
for(unsigned int ix=0;ix<particlesToShower.size();++ix)
particlesToShower[ix]->maximumpT(minpT_,ShowerInteraction::QCD);
return HardTreePtr();
}
// construct the HardTree object needed to perform the showers
ShowerParticleVector newparticles(4);
// create the partons
int iemit=-1;
// g g -> h g
if(emission_type==0) {
newparticles[0] = new_ptr(ShowerParticle(partons_[0] ,false));
newparticles[1] = new_ptr(ShowerParticle(partons_[1] ,false));
iemit = pnew[0].z()/pnew[3].z()>0. ? 0 : 1;
}
// g q -> H q
else if(emission_type==1) {
newparticles[0] = new_ptr(ShowerParticle(partons_[0] ,false));
newparticles[1] = new_ptr(ShowerParticle(out_ ,false));
iemit = 1;
}
// q g -> H q
else if(emission_type==2) {
newparticles[0] = new_ptr(ShowerParticle(out_ ,false));
newparticles[1] = new_ptr(ShowerParticle(partons_[1] ,false));
iemit = 0;
}
// g qbar -> H qbar
else if(emission_type==3) {
newparticles[0] = new_ptr(ShowerParticle(partons_[0] ,false));
newparticles[1] = new_ptr(ShowerParticle(out_ ,false));
iemit = 1;
}
// qbar g -> H qbar
else if(emission_type==4) {
newparticles[0] = new_ptr(ShowerParticle(out_ ,false));
newparticles[1] = new_ptr(ShowerParticle(partons_[1] ,false));
iemit = 0;
}
unsigned int ispect = iemit==0 ? 1 : 0;
// create the jet
newparticles[3] = new_ptr(ShowerParticle(out_ , true));
// create the boson
newparticles[2] = new_ptr(ShowerParticle(higgs->dataPtr(),true));
// set the momenta
for(unsigned int ix=0;ix<4;++ix) newparticles[ix]->set5Momentum(pnew[ix]);
// create the off-shell particle
Lorentz5Momentum poff=pnew[iemit]-pnew[3];
poff.rescaleMass();
newparticles.push_back(new_ptr(ShowerParticle(partons_[iemit],false)));
newparticles.back()->set5Momentum(poff);
vector<HardBranchingPtr> inBranch,hardBranch; // create the branchings for the incoming particles
inBranch.push_back(new_ptr(HardBranching(newparticles[0],SudakovPtr(),
HardBranchingPtr(),HardBranching::Incoming)));
inBranch.push_back(new_ptr(HardBranching(newparticles[1],SudakovPtr(),
HardBranchingPtr(),HardBranching::Incoming)));
// intermediate IS particle
hardBranch.push_back(new_ptr(HardBranching(newparticles[4],SudakovPtr(),
inBranch[iemit],HardBranching::Incoming)));
inBranch[iemit]->addChild(hardBranch.back());
// create the branching for the emitted jet
inBranch[iemit]->addChild(new_ptr(HardBranching(newparticles[3],SudakovPtr(),
inBranch[iemit],HardBranching::Outgoing)));
ColinePtr cline1 = new_ptr(ColourLine());
ColinePtr cline2 = new_ptr(ColourLine());
ColinePtr cline3 = new_ptr(ColourLine());
if(newparticles[3]->id()<0||
(newparticles[3]->id()==ParticleID::g&&UseRandom::rndbool())) {
inBranch[iemit]->type(ShowerPartnerType::QCDColourLine);
- generator()->log() << "Higgs colour A1\n";
cline1->addAntiColoured(newparticles[3]);
cline1->addColoured (newparticles[4]);
cline1->addAntiColoured(newparticles[ispect]);
cline2->addColoured (newparticles[ispect]);
cline2->addAntiColoured(newparticles[4]);
cline2->addAntiColoured(newparticles[iemit]);
if(newparticles[3]->id()==ParticleID::g) {
- generator()->log() << "Higgs colour A2\n";
cline3->addColoured(newparticles[iemit]);
cline3->addColoured(newparticles[3]);
}
}
else {
inBranch[iemit]->type(ShowerPartnerType::QCDAntiColourLine);
- generator()->log() << "Higgs colour B1\n";
cline1->addColoured (newparticles[3]);
cline1->addAntiColoured(newparticles[4]);
cline1->addColoured (newparticles[ispect]);
cline2->addAntiColoured(newparticles[ispect]);
cline2->addColoured (newparticles[4]);
cline2->addColoured (newparticles[iemit]);
if(newparticles[3]->id()==ParticleID::g) {
- generator()->log() << "Higgs colour B2\n";
cline3->addAntiColoured(newparticles[iemit]);
cline3->addAntiColoured(newparticles[3]);
}
}
// set the colour partners
hardBranch.back()->colourPartner(inBranch[iemit==0 ? 1 : 0]);
inBranch[iemit==0 ? 1 : 0]->colourPartner(hardBranch.back());
// add other particle
hardBranch.push_back(inBranch[iemit==0 ? 1 : 0]);
// outgoing Higgs boson
hardBranch.push_back(new_ptr(HardBranching(newparticles[2],SudakovPtr(),
HardBranchingPtr(),HardBranching::Outgoing)));
// make the tree
HardTreePtr hardtree=new_ptr(HardTree(hardBranch,inBranch,ShowerInteraction::QCD));
// connect the ShowerParticles with the branchings
// and set the maximum pt for the radiation
set<HardBranchingPtr> hard=hardtree->branchings();
for(unsigned int ix=0;ix<particlesToShower.size();++ix) {
if( pt_ < minpT_ ) particlesToShower[ix]->maximumpT(minpT_,ShowerInteraction::QCD);
else particlesToShower[ix]->maximumpT(pt_,ShowerInteraction::QCD);
for(set<HardBranchingPtr>::const_iterator mit=hard.begin();
mit!=hard.end();++mit) {
if(particlesToShower[ix]->progenitor()->id()==(*mit)->branchingParticle()->id()&&
(( particlesToShower[ix]->progenitor()->isFinalState()&&
(**mit).status()==HardBranching::Outgoing)||
(!particlesToShower[ix]->progenitor()->isFinalState()&&
(**mit).status()==HardBranching::Incoming))) {
if(particlesToShower[ix]->progenitor()->momentum().z()/
(*mit)->branchingParticle()->momentum().z()<0.) continue;
hardtree->connect(particlesToShower[ix]->progenitor(),*mit);
if((**mit).status()==HardBranching::Incoming) {
(*mit)->beam(particlesToShower[ix]->original()->parents()[0]);
}
HardBranchingPtr parent=(*mit)->parent();
while(parent) {
parent->beam(particlesToShower[ix]->original()->parents()[0]);
parent=parent->parent();
};
}
}
}
// return the answer
return hardtree;
}
bool MEPP2Higgs::applyHard(ShowerParticleVector gluons,
vector<tcBeamPtr> beams,PPtr higgs,
unsigned int & iemit, unsigned int & itype,
vector<Lorentz5Momentum> & pnew,
pair<double,double> & xout, tPDPtr & out) {
++ntry_;
// calculate the limits on s
Energy mh(higgs->mass());
mh2_=sqr(mh);
Energy2 smin=mh2_;
Energy2 s=
(generator()->currentEvent()->incoming().first->momentum()+
generator()->currentEvent()->incoming().second->momentum()).m2();
Energy2 smax(s);
// calculate the rapidity of the higgs
double yH = 0.5*log((higgs->momentum().e()+higgs->momentum().z())/
(higgs->momentum().e()-higgs->momentum().z()));
// if no phase-space return
if(smax<smin) return false;
// get the evolution scales (this needs improving)
double kappa[2]={1.,1.};
// get the momentum fractions for the leading order process
// and the values of the PDF's
double x[2]={-99.99e99,-99.99e99},fx[2]={-99.99e99,-99.99e99};
tcPDFPtr pdf[2];
for(unsigned int ix=0;ix<gluons.size();++ix) {
x[ix]=gluons[ix]->x();
assert(beams[ix]);
pdf[ix]=beams[ix]->pdf();
assert(pdf[ix]);
fx[ix]=pdf[ix]->xfx(beams[ix],gluons[ix]->dataPtr(),mh2_,x[ix]);
}
// leading order ME
Energy4 lome = loME();
// select the type of process and generate the kinematics
double rn(UseRandom::rnd());
Energy2 shat(ZERO),uhat(ZERO),that(ZERO);
double weight(0.),xnew[2]={1.,1.};
// gg -> H g
if(rn<channelWeights_[0]) {
// generate the value of s according to 1/s^n
double rhomax(pow(smin/mh2_,1.-ggPow_)),rhomin(pow(smax/mh2_,1.-ggPow_));
double rho = rhomin+UseRandom::rnd()*(rhomax-rhomin);
shat = mh2_*pow(rho,1./(1.-ggPow_));
Energy2 jacobian = mh2_/(ggPow_-1.)*(rhomax-rhomin)*pow(shat/mh2_,ggPow_);
double sbar=shat/mh2_;
// calculate limits on that
Energy2 tmax=mh2_*kappa[0]*(1.-sbar)/(kappa[0]+sbar);
Energy2 tmin=shat*(1.-sbar)/(kappa[1]+sbar);
// calculate the limits on uhat
Energy2 umax(mh2_-shat-tmin),umin(mh2_-shat-tmax);
// check inside phase space
if(tmax<tmin||umax<umin) return false;
// generate t and u according to 1/t+1/u
// generate in 1/t
if(UseRandom::rndbool(0.5)) {
that=tmax*pow(tmin/tmax,UseRandom::rnd());
uhat=mh2_-shat-that;
jacobian *=log(tmin/tmax);
}
// generate in 1/u
else {
uhat=umax*pow(umin/umax,UseRandom::rnd());
that=mh2_-shat-uhat;
jacobian *=log(umin/umax);
}
Energy4 jacobian2 = jacobian * 2.*uhat*that/(shat-mh2_);
// new scale (this is mt^2=pt^2+mh^2)
Energy2 scale(uhat*that/shat+mh2_);
// the PDF's with the emitted gluon
double fxnew[2];
xnew[0]=exp(yH)/sqrt(s)*sqrt(shat*(mh2_-uhat)/(mh2_-that));
xnew[1]=shat/(s*xnew[0]);
if(xnew[0]<=0.||xnew[0]>=1.||xnew[1]<=0.||xnew[1]>=1.) return false;
for(unsigned int ix=0;ix<2;++ix)
fxnew[ix]=pdf[ix]->xfx(beams[ix],gluons[ix]->dataPtr(),scale,xnew[ix]);
// jacobian and me parts of the weight
weight = jacobian2*ggME(shat,uhat,that)/lome*mh2_/sqr(shat);
// pdf part of the weight
weight *=fxnew[0]*fxnew[1]*x[0]*x[1]/(fx[0]*fx[1]*xnew[0]*xnew[1]);
// finally coupling and different channel pieces
weight *= 1./16./sqr(Constants::pi)*alpha_->value(scale)/channelWeights_[0];
itype=0;
iemit = that>uhat ? 0 : 1;
out = getParticleData(ParticleID::g);
}
// incoming quark or antiquark
else {
// generate the value of s according to 1/s^n
double rhomax(pow(smin/mh2_,1.-qgPow_)),rhomin(pow(smax/mh2_,1.-qgPow_));
double rho = rhomin+UseRandom::rnd()*(rhomax-rhomin);
shat = mh2_*pow(rho,1./(1.-qgPow_));
Energy2 jacobian = mh2_/(qgPow_-1.)*(rhomax-rhomin)*pow(shat/mh2_,qgPow_);
double sbar=shat/mh2_;
// calculate limits on that
Energy2 tmax=mh2_*kappa[0]*(1.-sbar)/(kappa[0]+sbar);
Energy2 tmin=shat*(1.-sbar)/(kappa[1]+sbar);
// calculate the limits on uhat
Energy2 umax(mh2_-shat-tmin),umin(mh2_-shat-tmax);
// check inside phase space
if(tmax<tmin||umax<umin) return false;
// generate t
bool order(UseRandom::rndbool());
Energy4 jacobian2;
if(order) {
uhat=umax*pow(umin/umax,UseRandom::rnd());
that=mh2_-shat-uhat;
jacobian2 = jacobian * uhat*log(umax/umin);
}
else {
that=tmax*pow(tmin/tmax,UseRandom::rnd());
uhat=mh2_-shat-that;
jacobian2 = jacobian * that*log(tmax/tmin);
}
InvEnergy4 mewgt;
// new scale (this is mt^2=pt^2+mh^2)
Energy2 scale(uhat*that/shat+mh2_);
double fxnew[2];
xnew[0]=exp(yH)/sqrt(s)*sqrt(shat*(mh2_-uhat)/(mh2_-that));
xnew[1]=shat/(s*xnew[0]);
if(xnew[0]<=0.||xnew[0]>=1.||xnew[1]<=0.||xnew[1]>=1.) return false;
if(rn<channelWeights_[1]) {
itype = 1;
// q g -> H q
if(!order) {
out = quarkFlavour(pdf[0],scale,xnew[0],beams[0],fxnew[0],false);
fxnew[1]=pdf[1]->xfx(beams[1],gluons[1]->dataPtr(),scale,xnew[1]);
iemit = 0;
mewgt = out ? qgME(shat,uhat,that)/lome*mh2_/sqr(shat) : ZERO;
}
// g q -> H q
else {
fxnew[0]=pdf[0]->xfx(beams[0],gluons[0]->dataPtr(),scale,xnew[0]);
out = quarkFlavour(pdf[1],scale,xnew[1],beams[1],fxnew[1],false);
iemit = 1;
mewgt = out ? qgME(shat,that,uhat)/lome*mh2_/sqr(shat) : ZERO;
}
jacobian2 /= (channelWeights_[1]-channelWeights_[0]);
}
else {
itype=2;
// qbar g -> H qbar
if(!order) {
out = quarkFlavour(pdf[0],scale,xnew[0],beams[0],fxnew[0],true);
fxnew[1]=pdf[1]->xfx(beams[1],gluons[1]->dataPtr(),scale,xnew[1]);
iemit = 0;
mewgt = out ? qbargME(shat,uhat,that)/lome*mh2_/sqr(shat) : ZERO;
}
// g qbar -> H qbar
else {
fxnew[0]=pdf[0]->xfx(beams[0],gluons[0]->dataPtr(),scale,xnew[0]);
out = quarkFlavour(pdf[1],scale,xnew[1],beams[1],fxnew[1],true);
iemit = 1;
mewgt = out ? qbargME(shat,that,uhat)/lome*mh2_/sqr(shat) : ZERO;
}
jacobian2/=(channelWeights_[2]-channelWeights_[1]);
}
// weight (factor of 2 as pick q(bar)g or gq(bar)
weight = 2.*jacobian2*mewgt;
// pdf part of the weight
weight *=fxnew[0]*fxnew[1]*x[0]*x[1]/(fx[0]*fx[1]*xnew[0]*xnew[1]);
// finally coupling and different channel pieces
weight *= 1./16./sqr(Constants::pi)*alpha_->value(scale);
}
// if me correction should be applied
if(weight>1.) {
++nover_;
maxwgt_ = max( maxwgt_ , weight);
weight=1.;
}
if(UseRandom::rnd()>weight) return false;
++ngen_;
// construct the momenta
Energy roots = 0.5*sqrt(s);
Energy pt = sqrt(uhat*that/shat);
Energy mt = sqrt(uhat*that/shat+mh2_);
Lorentz5Momentum pin[2]={Lorentz5Momentum(ZERO,ZERO, xnew[0]*roots,xnew[0]*roots),
Lorentz5Momentum(ZERO,ZERO,-xnew[1]*roots,xnew[1]*roots)};
double phi = Constants::twopi*UseRandom::rnd();
Lorentz5Momentum pH(pt*cos(phi),pt*sin(phi),mt*sinh(yH),mt*cosh(yH));
Lorentz5Momentum pJ(pin[0]+pin[1]-pH);
// momenta to be returned
pnew.push_back(pin[0]);
pnew.push_back(pin[1]);
pnew.push_back(pJ);
pnew.push_back(pH);
xout.first = xnew[0];
xout.second = xnew[1];
return true;
}
Energy2 MEPP2Higgs::ggME(Energy2 s, Energy2 t, Energy2 u) {
Energy2 output;
if(massOption_==0) {
complex<Energy> me[2][2][2];
me[1][1][1] = ZERO;
me[1][1][0] = ZERO;
me[0][1][0] = ZERO;
me[0][1][1] = ZERO;
for(unsigned int ix=minLoop_; ix<=maxLoop_; ++ix ) {
Energy2 mf2=sqr(getParticleData(long(ix))->mass());
bi_[1]=B(s,mf2);
bi_[2]=B(u,mf2);
bi_[3]=B(t,mf2);
bi_[4]=B(mh2_,mf2);
bi_[1]=bi_[1]-bi_[4];
bi_[2]=bi_[2]-bi_[4];
bi_[3]=bi_[3]-bi_[4];
ci_[1]=C(s,mf2);
ci_[2]=C(u,mf2);
ci_[3]=C(t,mf2);
ci_[7]=C(mh2_,mf2);
ci_[4]=(s*ci_[1]-mh2_*ci_[7])/(s-mh2_);
ci_[5]=(u*ci_[2]-mh2_*ci_[7])/(u-mh2_);
ci_[6]=(t*ci_[3]-mh2_*ci_[7])/(t-mh2_);
di_[1]=D(t,u,s,mf2);
di_[2]=D(s,t,u,mf2);
di_[3]=D(s,u,t,mf2);
me[1][1][1]+=me1(s,u,t,mf2,1,2,3,4,5,6);
me[1][1][0]+=me2(s,u,t,mf2);
me[0][1][0]+=me1(u,s,t,mf2,2,1,3,5,4,6);
me[0][1][1]+=me1(t,u,s,mf2,3,2,1,6,5,4);
}
me[0][0][0]=-me[1][1][1];
me[0][0][1]=-me[1][1][0];
me[1][0][1]=-me[0][1][0];
me[1][0][0]=-me[0][1][1];
output = real(me[0][0][0]*conj(me[0][0][0])+
me[0][0][1]*conj(me[0][0][1])+
me[0][1][0]*conj(me[0][1][0])+
me[0][1][1]*conj(me[0][1][1])+
me[1][0][0]*conj(me[1][0][0])+
me[1][0][1]*conj(me[1][0][1])+
me[1][1][0]*conj(me[1][1][0])+
me[1][1][1]*conj(me[1][1][1]));
output *= 3./8.;
}
else {
output=32./3.*
(pow<4,1>(s)+pow<4,1>(t)+pow<4,1>(u)+pow<4,1>(mh2_))/s/t/u;
}
// spin and colour factors
return output/4./64.;
}
Energy2 MEPP2Higgs::qgME(Energy2 s, Energy2 t, Energy2 u) {
Energy2 output;
if(massOption_==0) {
complex<Energy2> A(ZERO);
Energy2 si(u-mh2_);
for(unsigned int ix=minLoop_;ix<=maxLoop_;++ix) {
Energy2 mf2=sqr(getParticleData(long(ix))->mass());
A += mf2*(2.+2.*double(u/si)*(B(u,mf2)-B(mh2_,mf2))
+double((4.*mf2-s-t)/si)*Complex(u*C(u,mf2)-mh2_*C(mh2_,mf2)));
}
output =-4.*(sqr(s)+sqr(t))/sqr(si)/u*real(A*conj(A));
}
else{
output =-4.*(sqr(s)+sqr(t))/u/9.;
}
// final colour/spin factors
return output/24.;
}
Energy2 MEPP2Higgs::qbargME(Energy2 s, Energy2 t, Energy2 u) {
Energy2 output;
if(massOption_==0) {
complex<Energy2> A(ZERO);
Energy2 si(u-mh2_);
for(unsigned int ix=minLoop_;ix<=maxLoop_;++ix) {
Energy2 mf2=sqr(getParticleData(long(ix))->mass());
A+=mf2*(2.+2.*double(u/si)*(B(u,mf2)-B(mh2_,mf2))
+double((4.*mf2-s-t)/si)*Complex(u*C(u,mf2)-mh2_*C(mh2_,mf2)));
}
output =-4.*(sqr(s)+sqr(t))/sqr(si)/u*real(A*conj(A));
}
else {
output =-4.*(sqr(s)+sqr(t))/u/9.;
}
// final colour/spin factors
return output/24.;
}
Energy4 MEPP2Higgs::loME() const {
Complex I(0);
if(massOption_==0) {
for(unsigned int ix=minLoop_;ix<=maxLoop_;++ix) {
double x = sqr(getParticleData(long(ix))->mass())/mh2_;
I += 3.*x*(2.+(4.*x-1.)*F(x));
}
}
else {
I = 1.;
}
return sqr(mh2_)/576./Constants::pi*norm(I);
}
tPDPtr MEPP2Higgs::quarkFlavour(tcPDFPtr pdf, Energy2 scale,
double x, tcBeamPtr beam,
double & pdfweight, bool anti) {
vector<double> weights;
vector<tPDPtr> partons;
pdfweight = 0.;
if(!anti) {
for(unsigned int ix=1;ix<=5;++ix) {
partons.push_back(getParticleData(long(ix)));
weights.push_back(max(0.,pdf->xfx(beam,partons.back(),scale,x)));
pdfweight += weights.back();
}
}
else {
for(unsigned int ix=1;ix<=5;++ix) {
partons.push_back(getParticleData(-long(ix)));
weights.push_back(max(0.,pdf->xfx(beam,partons.back(),scale,x)));
pdfweight += weights.back();
}
}
if(pdfweight==0.) return tPDPtr();
double wgt=UseRandom::rnd()*pdfweight;
for(unsigned int ix=0;ix<weights.size();++ix) {
if(wgt<=weights[ix]) return partons[ix];
wgt -= weights[ix];
}
assert(false);
return tPDPtr();
}
Complex MEPP2Higgs::B(Energy2 s,Energy2 mf2) const {
Complex output,pii(0.,Constants::pi);
double rat=s/(4.*mf2);
if(s<ZERO)
output=2.-2.*sqrt(1.-1./rat)*log(sqrt(-rat)+sqrt(1.-rat));
else if(s>=ZERO&&rat<1.)
output=2.-2.*sqrt(1./rat-1.)*asin(sqrt(rat));
else
output=2.-sqrt(1.-1./rat)*(2.*log(sqrt(rat)+sqrt(rat-1.))-pii);
return output;
}
complex<InvEnergy2> MEPP2Higgs::C(Energy2 s,Energy2 mf2) const {
complex<InvEnergy2> output;
Complex pii(0.,Constants::pi);
double rat=s/(4.*mf2);
if(s<ZERO)
output=2.*sqr(log(sqrt(-rat)+sqrt(1.-rat)))/s;
else if(s>=ZERO&&rat<1.)
output=-2.*sqr(asin(sqrt(rat)))/s;
else {
double cosh=log(sqrt(rat)+sqrt(rat-1.));
output=2.*(sqr(cosh)-sqr(Constants::pi)/4.-pii*cosh)/s;
}
return output;
}
Complex MEPP2Higgs::dIntegral(Energy2 a, Energy2 b, double y0) const {
Complex output;
if(b==ZERO) output=0.;
else {
Complex y1=0.5*(1.+sqrt(1.-4.*(a+epsi_)/b));
Complex y2=1.-y1;
Complex z1=y0/(y0-y1);
Complex z2=(y0-1.)/(y0-y1);
Complex z3=y0/(y0-y2);
Complex z4=(y0-1.)/(y0-y2);
output=Math::Li2(z1)-Math::Li2(z2)+Math::Li2(z3)-Math::Li2(z4);
}
return output;
}
complex<InvEnergy4> MEPP2Higgs::D(Energy2 s,Energy2 t, Energy2,
Energy2 mf2) const {
Complex output,pii(0.,Constants::pi);
Energy4 st=s*t;
Energy4 root=sqrt(sqr(st)-4.*st*mf2*(s+t-mh2_));
double xp=0.5*(st+root)/st,xm=1-xp;
output = 2.*(-dIntegral(mf2,s,xp)-dIntegral(mf2,t,xp)
+dIntegral(mf2,mh2_,xp)+log(-xm/xp)
*(log((mf2+epsi_)/GeV2)-log((mf2+epsi_-s*xp*xm)/GeV2)
+log((mf2+epsi_-mh2_*xp*xm)/GeV2)-log((mf2+epsi_-t*xp*xm)/GeV2)));
return output/root;
}
complex<Energy> MEPP2Higgs::me1(Energy2 s,Energy2 t,Energy2 u, Energy2 mf2,
unsigned int i ,unsigned int j ,unsigned int k ,
unsigned int i1,unsigned int j1,unsigned int k1) const {
Energy2 s1(s-mh2_),t1(t-mh2_),u1(u-mh2_);
return mf2*4.*sqrt(2.*s*t*u)*
(-4.*(1./(u*t)+1./(u*u1)+1./(t*t1))
-4.*((2.*s+t)*bi_[k]/sqr(u1)+(2.*s+u)*bi_[j]/sqr(t1))/s
-(s-4.*mf2)*(s1*ci_[i1]+(u-s)*ci_[j1]+(t-s)*ci_[k1])/(s*t*u)
-8.*mf2*(ci_[j1]/(t*t1)+ci_[k1]/(u*u1))
+0.5*(s-4.*mf2)*(s*t*di_[k]+u*s*di_[j]-u*t*di_[i])/(s*t*u)
+4.*mf2*di_[i]/s
-2.*(u*ci_[k]+t*ci_[j]+u1*ci_[k1]+t1*ci_[j1]-u*t*di_[i])/sqr(s));
}
complex<Energy> MEPP2Higgs::me2(Energy2 s,Energy2 t,Energy2 u,
Energy2 mf2) const {
Energy2 s1(s-mh2_),t1(t-mh2_),u1(u-mh2_);
return mf2*4.*sqrt(2.*s*t*u)*(4.*mh2_+(mh2_-4.*mf2)*(s1*ci_[4]+t1*ci_[5]+u1*ci_[6])
-0.5*(mh2_-4.*mf2)*(s*t*di_[3]+u*s*di_[2]+u*t*di_[1]) )/
(s*t*u);
}
Complex MEPP2Higgs::F(double x) const {
if(x<.25) {
double root = sqrt(1.-4.*x);
Complex pii(0.,Constants::pi);
return 0.5*sqr(log((1.+root)/(1.-root))-pii);
}
else {
return -2.*sqr(asin(0.5/sqrt(x)));
}
}
bool MEPP2Higgs::getEvent(vector<Lorentz5Momentum> & pnew,
int & emis_type){
// maximum pt (half of centre-of-mass energy)
Energy maxp = 0.5*generator()->maximumCMEnergy();
// set pt of emission to zero
pt_=ZERO;
//Working Variables
Energy pt;
double yj;
// limits on the rapidity of the jet
double minyj = -8.0,maxyj = 8.0;
bool reject;
double wgt;
emis_type=-1;
tcPDPtr outParton;
for(int j=0;j<5;++j) {
pt = maxp;
do {
double a = alpha_->overestimateValue()*prefactor_[j]*(maxyj-minyj)/(power_-1.);
// generate next pt
pt=GeV/pow(pow(GeV/pt,power_-1)-log(UseRandom::rnd())/a,1./(power_-1.));
// generate rapidity of the jet
yj=UseRandom::rnd()*(maxyj-minyj)+ minyj;
// calculate rejection weight
wgt=getResult(j,pt,yj,outParton);
wgt/= prefactor_[j]*pow(GeV/pt,power_);
reject = UseRandom::rnd()>wgt;
//no emission event if p goes past p min - basically set to outside
//of the histogram bounds (hopefully hist object just ignores it)
if(pt<minpT_){
pt=ZERO;
reject = false;
}
if(wgt>1.0) {
ostringstream s;
s << "MEPP2Higgs::getEvent weight for channel " << j
<< "is " << wgt << " which is greater than 1";
generator()->logWarning( Exception(s.str(), Exception::warning) );
}
}
while(reject);
// set pt of emission etc
if(pt>pt_){
emis_type = j;
pt_=pt;
yj_=yj;
out_ = outParton;
}
}
//was this an (overall) no emission event?
if(pt_<minpT_){
pt_=ZERO;
emis_type = 5;
}
if(emis_type==5) return false;
// generate the momenta of the particles
// hadron-hadron cmf
Energy2 s=sqr(generator()->maximumCMEnergy());
// transverse energy
Energy et=sqrt(mh2_+sqr(pt_));
// first calculate all the kinematic variables
// longitudinal real correction fractions
double x = pt_*exp( yj_)/sqrt(s)+et*exp( yh_)/sqrt(s);
double y = pt_*exp(-yj_)/sqrt(s)+et*exp(-yh_)/sqrt(s);
// that and uhat
// Energy2 th = -sqrt(s)*x*pt_*exp(-yj_);
// Energy2 uh = -sqrt(s)*y*pt_*exp( yj_);
// Energy2 sh = x*y*s;
// reconstruct the momenta
// incoming momenta
pnew.push_back(Lorentz5Momentum(ZERO,ZERO,
x*0.5*sqrt(s), x*0.5*sqrt(s),ZERO));
pnew.push_back(Lorentz5Momentum(ZERO,ZERO,
-y*0.5*sqrt(s), y*0.5*sqrt(s),ZERO));
// outgoing momenta
double phi(Constants::twopi*UseRandom::rnd());
double sphi(sin(phi)),cphi(cos(phi));
pnew.push_back(Lorentz5Momentum( cphi*pt_, sphi*pt_, et*sinh(yh_),
et*cosh(yh_), mass_));
pnew.push_back(Lorentz5Momentum(-cphi*pt_,-sphi*pt_,pt_*sinh(yj_),
pt_*cosh(yj_),ZERO));
return true;
}
double MEPP2Higgs::getResult(int emis_type, Energy pt, double yj,
tcPDPtr & outParton) {
Energy2 s=sqr(generator()->maximumCMEnergy());
Energy2 scale = mh2_+sqr(pt);
Energy et=sqrt(scale);
scale = mu_F_opt_==0 ? mh2_+sqr(pt) : sqr(pt) ;
// longitudinal real correction fractions
double x = pt*exp( yj)/sqrt(s)+et*exp( yh_)/sqrt(s);
double y = pt*exp(-yj)/sqrt(s)+et*exp(-yh_)/sqrt(s);
// reject if outside region
if(x<0.||x>1.||y<0.||y>1.||x*y<mh2_/s) return 0.;
// longitudinal born fractions
double x1 = mass_*exp( yh_)/sqrt(s);
double y1 = mass_*exp(-yh_)/sqrt(s);
// mandelstam variables
Energy2 th = -sqrt(s)*x*pt*exp(-yj);
Energy2 uh = -sqrt(s)*y*pt*exp( yj);
Energy2 sh = mh2_-th-uh;
InvEnergy2 res = InvEnergy2();
// pdf part of the cross section
double pdf[4] = {99.99e99,99.99e99,99.99e99,99.99e99};
if(mu_F_opt_==0) { // As in original version ...
pdf[0]=beams_[0]->pdf()->xfx(beams_[0],partons_[0],mh2_,x1);
pdf[1]=beams_[1]->pdf()->xfx(beams_[1],partons_[1],mh2_,y1);
} else { // As in Nason and Ridolfi paper ...
pdf[0]=beams_[0]->pdf()->xfx(beams_[0],partons_[0],scale,x1);
pdf[1]=beams_[1]->pdf()->xfx(beams_[1],partons_[1],scale,y1);
}
// g g -> H g
if(emis_type==0) {
outParton = partons_[1];
pdf[2]=beams_[0]->pdf()->xfx(beams_[0],partons_[0],scale,x);
pdf[3]=beams_[1]->pdf()->xfx(beams_[1],partons_[1],scale,y);
res = ggME(sh,uh,th)/loME();
}
// q g -> H q
else if(emis_type==1) {
outParton = quarkFlavour(beams_[0]->pdf(),scale,x,beams_[0],pdf[2],false);
pdf[3]=beams_[1]->pdf()->xfx(beams_[1],partons_[1],scale,y);
res = outParton ? qgME(sh,uh,th)/loME() : ZERO;
}
// g q -> H q
else if(emis_type==2) {
pdf[2]=beams_[0]->pdf()->xfx(beams_[0],partons_[0],scale,x);
outParton = quarkFlavour(beams_[1]->pdf(),scale,y,beams_[1],pdf[3],false);
res = outParton ? qgME(sh,th,uh)/loME() : ZERO;
}
// qbar g -> H qbar
else if(emis_type==3) {
outParton = quarkFlavour(beams_[0]->pdf(),scale,x,beams_[0],pdf[2],true);
pdf[3]=beams_[1]->pdf()->xfx(beams_[1],partons_[1],scale,y);
res = outParton ? qbargME(sh,uh,th)/loME() : ZERO;
}
// g qbar -> H qbar
else if(emis_type==4) {
pdf[2]=beams_[0]->pdf()->xfx(beams_[0],partons_[0],scale,x);
outParton = quarkFlavour(beams_[1]->pdf(),scale,y,beams_[1],pdf[3],true);
res = outParton ? qbargME(sh,th,uh)/loME() : ZERO;
}
//deals with pdf zero issue at large x
if(pdf[0]<=0.||pdf[1]<=0.||pdf[2]<=0.||pdf[3]<=0.) {
res = ZERO;
}
else {
res *= pdf[2]*pdf[3]/pdf[0]/pdf[1]*mh2_/sh;
}
scale = mu_R_opt_==0 ? mh2_+sqr(pt) : sqr(pt) ;
return alpha_->ratio(scale)/8./sqr(Constants::pi)*mh2_/sh*GeV*pt*res;
}
void MEPP2Higgs::initializeMECorrection(ShowerTreePtr tree, double & initial,
double & final) {
final = 1.;
initial = tree->incomingLines().begin()->second->id()==ParticleID::g ?
enhance_ : 1.;
}

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