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PerturbativeDecayer.cc
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// -*- C++ -*-
//
// This is the implementation of the non-inlined, non-templated member
// functions of the PerturbativeDecayer class.
//
#include "PerturbativeDecayer.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/EventRecord/Particle.h"
#include "ThePEG/Repository/UseRandom.h"
#include "ThePEG/Repository/EventGenerator.h"
#include "ThePEG/Utilities/DescribeClass.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/Interface/Reference.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Interface/Switch.h"
#include "ThePEG/Utilities/EnumIO.h"
using namespace Herwig;
void PerturbativeDecayer::persistentOutput(PersistentOStream & os) const {
os << ounit(pTmin_,GeV) << oenum(inter_) << alphaS_ << alphaEM_
<< useMEforT2_ << C_ << ymax_ << phaseOpt_;
}
void PerturbativeDecayer::persistentInput(PersistentIStream & is, int) {
is >> iunit(pTmin_,GeV) >> ienum(inter_) >> alphaS_ >> alphaEM_
>> useMEforT2_ >> C_ >> ymax_ >> phaseOpt_;
}
// The following static variable is needed for the type
// description system in ThePEG.
DescribeAbstractClass<PerturbativeDecayer,DecayIntegrator>
describeHerwigPerturbativeDecayer("Herwig::PerturbativeDecayer",
"Herwig.so HwPerturbativeDecay.so");
void PerturbativeDecayer::Init() {
static ClassDocumentation<PerturbativeDecayer> documentation
("The PerturbativeDecayer class is the mase class for "
"perturbative decays in Herwig");
static Parameter<PerturbativeDecayer,Energy> interfacepTmin
("pTmin",
"Minimum transverse momentum from gluon radiation",
&PerturbativeDecayer::pTmin_, GeV, 1.0*GeV, 0.0*GeV, 10.0*GeV,
false, false, Interface::limited);
static Switch<PerturbativeDecayer,ShowerInteraction> interfaceInteractions
("Interactions",
"which interactions to include for the hard corrections",
&PerturbativeDecayer::inter_, ShowerInteraction::QCD, false, false);
static SwitchOption interfaceInteractionsQCD
(interfaceInteractions,
"QCD",
"QCD Only",
ShowerInteraction::QCD);
static SwitchOption interfaceInteractionsQED
(interfaceInteractions,
"QED",
"QED only",
ShowerInteraction::QED);
static SwitchOption interfaceInteractionsQCDandQED
(interfaceInteractions,
"QCDandQED",
"Both QCD and QED",
ShowerInteraction::QEDQCD);
static Reference<PerturbativeDecayer,ShowerAlpha> interfaceAlphaS
("AlphaS",
"Object for the coupling in the generation of hard QCD radiation",
&PerturbativeDecayer::alphaS_, false, false, true, true, false);
static Reference<PerturbativeDecayer,ShowerAlpha> interfaceAlphaEM
("AlphaEM",
"Object for the coupling in the generation of hard QED radiation",
&PerturbativeDecayer::alphaEM_, false, false, true, true, false);
static Switch<PerturbativeDecayer,bool> interfaceUseMEForT2
("UseMEForT2",
"Use the matrix element correction, if available to fill the T2"
" region for the decay shower and don't fill using the shower",
&PerturbativeDecayer::useMEforT2_, true, false, false);
static SwitchOption interfaceUseMEForT2Shower
(interfaceUseMEForT2,
"Shower",
"Use the shower to fill the T2 region",
false);
static SwitchOption interfaceUseMEForT2ME
(interfaceUseMEForT2,
"ME",
"Use the Matrix element to fill the T2 region",
true);
static Parameter<PerturbativeDecayer,double> interfacePrefactor
("Prefactor",
"The prefactor for the sampling of the powheg Sudakov",
&PerturbativeDecayer::C_, 6.3, 0.0, 1e10,
false, false, Interface::limited);
static Parameter<PerturbativeDecayer,double> interfaceYMax
("YMax",
"The maximum value for the rapidity",
&PerturbativeDecayer::ymax_, 10., 0.0, 100.,
false, false, Interface::limited);
static Switch<PerturbativeDecayer,unsigned int> interfacePhaseSpaceOption
("PhaseSpaceOption",
"Option for the phase-space sampling",
&PerturbativeDecayer::phaseOpt_, 0, false, false);
static SwitchOption interfacePhaseSpaceOptionFixedYLimits
(interfacePhaseSpaceOption,
"FixedYLimits",
"Use a fixed limit for the rapidity",
0);
static SwitchOption interfacePhaseSpaceOptionVariableYLimits
(interfacePhaseSpaceOption,
"VariableYLimits",
"Change limit for the rapidity with pT",
1);
}
double PerturbativeDecayer::matrixElementRatio(const Particle & ,
const ParticleVector & ,
const ParticleVector & ,
MEOption ,
ShowerInteraction ) {
throw Exception() << "Base class PerturbativeDecayer::matrixElementRatio() "
<< "called, should have an implementation in the inheriting class"
<< Exception::runerror;
return 0.;
}
RealEmissionProcessPtr PerturbativeDecayer::generateHardest(RealEmissionProcessPtr born) {
return getHardEvent(born,false,inter_);
}
RealEmissionProcessPtr PerturbativeDecayer::applyHardMatrixElementCorrection(RealEmissionProcessPtr born) {
return getHardEvent(born,true,ShowerInteraction::QCD);
}
RealEmissionProcessPtr PerturbativeDecayer::getHardEvent(RealEmissionProcessPtr born,
bool inDeadZone,
ShowerInteraction inter) {
// check one incoming
assert(born->bornIncoming().size()==1);
// search for coloured/charged particles
bool colouredParticles=born->bornIncoming()[0]->dataPtr()->coloured();
bool chargedParticles=born->bornIncoming()[0]->dataPtr()->charged();
for(unsigned int ix=0;ix<born->bornOutgoing().size();++ix) {
if(born->bornOutgoing()[ix]->dataPtr()->coloured())
colouredParticles=true;
if(born->bornOutgoing()[ix]->dataPtr()->charged())
chargedParticles=true;
}
// if no coloured/charged particles return
if ( !colouredParticles && !chargedParticles ) return RealEmissionProcessPtr();
if ( !colouredParticles && inter==ShowerInteraction::QCD ) return RealEmissionProcessPtr();
if ( ! chargedParticles && inter==ShowerInteraction::QED ) return RealEmissionProcessPtr();
// check exactly two outgoing particles
if(born->bornOutgoing().size()!=2) return RealEmissionProcessPtr();
// for decay b -> a c
// set progenitors
PPtr cProgenitor = born->bornOutgoing()[0];
PPtr aProgenitor = born->bornOutgoing()[1];
// get the decaying particle
PPtr bProgenitor = born->bornIncoming()[0];
// identify which dipoles are required
vector<DipoleType> dipoles;
if(!identifyDipoles(dipoles,aProgenitor,bProgenitor,cProgenitor,inter)) {
return RealEmissionProcessPtr();
}
Energy trialpT = pTmin_;
LorentzRotation eventFrame;
vector<Lorentz5Momentum> momenta;
vector<Lorentz5Momentum> trialMomenta(4);
PPtr finalEmitter, finalSpectator;
PPtr trialEmitter, trialSpectator;
DipoleType finalType(FFa,ShowerInteraction::QCD);
for (int i=0; i<int(dipoles.size()); ++i) {
if(dipoles[i].type==FFg) continue;
// assign emitter and spectator based on current dipole
if (dipoles[i].type==FFc || dipoles[i].type==IFc || dipoles[i].type==IFbc) {
trialEmitter = cProgenitor;
trialSpectator = aProgenitor;
}
else if (dipoles[i].type==FFa || dipoles[i].type==IFa || dipoles[i].type==IFba) {
trialEmitter = aProgenitor;
trialSpectator = cProgenitor;
}
// find rotation from lab to frame with the spectator along -z
LorentzRotation trialEventFrame(bProgenitor->momentum().findBoostToCM());
Lorentz5Momentum pspectator = (trialEventFrame*trialSpectator->momentum());
trialEventFrame.rotateZ( -pspectator.phi() );
trialEventFrame.rotateY( -pspectator.theta() - Constants::pi );
// invert it
trialEventFrame.invert();
// try to generate an emission
pT_ = pTmin_;
vector<Lorentz5Momentum> trialMomenta
= hardMomenta(bProgenitor, trialEmitter, trialSpectator,
dipoles, i, inDeadZone);
// select dipole which gives highest pT emission
if(pT_>trialpT) {
trialpT = pT_;
momenta = trialMomenta;
eventFrame = trialEventFrame;
finalEmitter = trialEmitter;
finalSpectator = trialSpectator;
finalType = dipoles[i];
if (dipoles[i].type==FFc || dipoles[i].type==FFa ) {
if((momenta[3]+momenta[1]).m2()-momenta[1].m2()>
(momenta[3]+momenta[2]).m2()-momenta[2].m2()) {
swap(finalEmitter,finalSpectator);
swap(momenta[1],momenta[2]);
}
}
}
}
pT_ = trialpT;
// if no emission return
if(momenta.empty()) {
if(inter==ShowerInteraction::ALL || inter==ShowerInteraction::QEDQCD || inter==ShowerInteraction::QCD)
born->pT()[ShowerInteraction::QCD] = pTmin_;
if(inter==ShowerInteraction::ALL || inter==ShowerInteraction::QEDQCD || inter==ShowerInteraction::QED)
born->pT()[ShowerInteraction::QED] = pTmin_;
return born;
}
// rotate momenta back to the lab
for(unsigned int ix=0;ix<momenta.size();++ix) {
momenta[ix] *= eventFrame;
}
// set maximum pT for subsequent branchings
if(inter==ShowerInteraction::ALL || inter==ShowerInteraction::QEDQCD || inter==ShowerInteraction::QCD)
born->pT()[ShowerInteraction::QCD] = pT_;
if(inter==ShowerInteraction::ALL || inter==ShowerInteraction::QEDQCD || inter==ShowerInteraction::QED)
born->pT()[ShowerInteraction::QED] = pT_;
// get ParticleData objects
tcPDPtr b = bProgenitor ->dataPtr();
tcPDPtr e = finalEmitter ->dataPtr();
tcPDPtr s = finalSpectator->dataPtr();
tcPDPtr boson = getParticleData(finalType.interaction==ShowerInteraction::QCD ?
ParticleID::g : ParticleID::gamma);
// create new ShowerParticles
PPtr emitter = e ->produceParticle(momenta[1]);
PPtr spectator = s ->produceParticle(momenta[2]);
PPtr gauge = boson->produceParticle(momenta[3]);
PPtr incoming = b ->produceParticle(bProgenitor->momentum());
// insert the particles
born->incoming().push_back(incoming);
unsigned int iemit(0),ispect(0);
for(unsigned int ix=0;ix<born->bornOutgoing().size();++ix) {
if(born->bornOutgoing()[ix]==finalEmitter) {
born->outgoing().push_back(emitter);
iemit = born->outgoing().size();
}
else if(born->bornOutgoing()[ix]==finalSpectator) {
born->outgoing().push_back(spectator);
ispect = born->outgoing().size();
}
}
born->outgoing().push_back(gauge);
if(!spectator->dataPtr()->coloured() ||
(finalType.type != FFa && finalType.type!=FFc) ) ispect = 0;
born->emitter(iemit);
born->spectator(ispect);
born->emitted(3);
// boost if being use as ME correction
if(inDeadZone) {
if(finalType.type==IFa || finalType.type==IFba) {
LorentzRotation trans(cProgenitor->momentum().findBoostToCM());
trans.boost(spectator->momentum().boostVector());
born->transformation(trans);
}
else if(finalType.type==IFc || finalType.type==IFbc) {
LorentzRotation trans(bProgenitor->momentum().findBoostToCM());
trans.boost(spectator->momentum().boostVector());
born->transformation(trans);
}
}
// set the interaction
born->interaction(finalType.interaction);
// set up colour lines
getColourLines(born);
// return the tree
return born;
}
bool PerturbativeDecayer::identifyDipoles(vector<DipoleType> & dipoles,
PPtr & aProgenitor,
PPtr & bProgenitor,
PPtr & cProgenitor,
ShowerInteraction inter) const {
enhance_ = 1.;
// identify any QCD dipoles
if(inter==ShowerInteraction::QCD ||
inter==ShowerInteraction::ALL || inter==ShowerInteraction::QEDQCD ) {
PDT::Colour bColour = bProgenitor->dataPtr()->iColour();
PDT::Colour cColour = cProgenitor->dataPtr()->iColour();
PDT::Colour aColour = aProgenitor->dataPtr()->iColour();
// decaying colour singlet
if (bColour==PDT::Colour0 ) {
if ((cColour==PDT::Colour3 && aColour==PDT::Colour3bar) ||
(cColour==PDT::Colour3bar && aColour==PDT::Colour3) ||
(cColour==PDT::Colour8 && aColour==PDT::Colour8)){
dipoles.push_back(DipoleType(FFa,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFc,ShowerInteraction::QCD));
if(aProgenitor->id()==ParticleID::g &&
cProgenitor->id()==ParticleID::g ) {
enhance_ = 1.5;
dipoles.push_back(DipoleType(FFg,ShowerInteraction::QCD));
}
}
}
// decaying colour triplet
else if (bColour==PDT::Colour3 ) {
if (cColour==PDT::Colour3 && aColour==PDT::Colour0){
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc ,ShowerInteraction::QCD));
}
else if (cColour==PDT::Colour0 && aColour==PDT::Colour3){
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa ,ShowerInteraction::QCD));
}
else if (cColour==PDT::Colour8 && aColour==PDT::Colour3){
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFa ,ShowerInteraction::QCD));
}
else if (cColour==PDT::Colour3 && aColour==PDT::Colour8){
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFa ,ShowerInteraction::QCD));
}
else if(cColour==PDT::Colour3bar && aColour==PDT::Colour3bar) {
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFa ,ShowerInteraction::QCD));
}
}
// decaying colour anti-triplet
else if (bColour==PDT::Colour3bar) {
if ((cColour==PDT::Colour3bar && aColour==PDT::Colour0)){
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc ,ShowerInteraction::QCD));
}
else if ((cColour==PDT::Colour0 && aColour==PDT::Colour3bar)){
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa ,ShowerInteraction::QCD));
}
else if (cColour==PDT::Colour8 && aColour==PDT::Colour3bar){
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFa ,ShowerInteraction::QCD));
}
else if (cColour==PDT::Colour3bar && aColour==PDT::Colour8){
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFa ,ShowerInteraction::QCD));
}
else if(cColour==PDT::Colour3 && aColour==PDT::Colour3) {
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFc ,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(FFa ,ShowerInteraction::QCD));
}
}
// decaying colour octet
else if (bColour==PDT::Colour8){
if ((cColour==PDT::Colour3 && aColour==PDT::Colour3bar) ||
(cColour==PDT::Colour3bar && aColour==PDT::Colour3)){
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc,ShowerInteraction::QCD));
}
else if (cColour==PDT::Colour8 && aColour==PDT::Colour0){
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc,ShowerInteraction::QCD));
}
else if (cColour==PDT::Colour0 && aColour==PDT::Colour8){
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa,ShowerInteraction::QCD));
}
}
// decaying colour sextet
else if(bColour==PDT::Colour6) {
if (cColour==PDT::Colour3 && aColour==PDT::Colour3) {
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc,ShowerInteraction::QCD));
}
}
// decaying colour antisextet
else if(bColour==PDT::Colour6bar) {
if (cColour==PDT::Colour3bar && aColour==PDT::Colour3bar) {
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFa,ShowerInteraction::QCD));
dipoles.push_back(DipoleType(IFc,ShowerInteraction::QCD));
}
}
}
// QED dipoles
if(inter==ShowerInteraction::ALL || inter==ShowerInteraction::QEDQCD ||
inter==ShowerInteraction::QED) {
const bool & bCharged = bProgenitor->dataPtr()->charged();
const bool & cCharged = cProgenitor->dataPtr()->charged();
const bool & aCharged = aProgenitor->dataPtr()->charged();
// initial-final
if(bCharged && aCharged) {
dipoles.push_back(DipoleType(IFba,ShowerInteraction::QED));
dipoles.push_back(DipoleType(IFa ,ShowerInteraction::QED));
}
if(bCharged && cCharged) {
dipoles.push_back(DipoleType(IFbc,ShowerInteraction::QED));
dipoles.push_back(DipoleType(IFc ,ShowerInteraction::QED));
}
// final-state
if(aCharged && cCharged) {
dipoles.push_back(DipoleType(FFa,ShowerInteraction::QED));
dipoles.push_back(DipoleType(FFc,ShowerInteraction::QED));
}
}
// check colour structure is allowed
return !dipoles.empty();
}
vector<Lorentz5Momentum> PerturbativeDecayer::hardMomenta(PPtr in, PPtr emitter,
PPtr spectator,
const vector<DipoleType> &dipoles,
int i, bool inDeadZone) {
// get masses of the particles
mb_ = in ->momentum().mass();
e_ = emitter ->momentum().mass()/mb_;
s_ = spectator->momentum().mass()/mb_;
e2_ = sqr(e_);
s2_ = sqr(s_);
vector<Lorentz5Momentum> particleMomenta;
Energy2 lambda = sqr(mb_)*sqrt(1.+sqr(s2_)+sqr(e2_)-2.*s2_-2.*e2_-2.*s2_*e2_);
// calculate A
double pre = C_;
// multiply by the colour factor of the dipole
// ISR
if (dipoles[i].type==IFba || dipoles[i].type==IFbc) {
pre *= colourCoeff(in->dataPtr(),emitter->dataPtr(),spectator->dataPtr(),dipoles[i]);
}
// radiation from a/c with initial-final connection
else if (dipoles[i].type==IFa || dipoles[i].type==IFc) {
pre *= colourCoeff(emitter->dataPtr(),in->dataPtr(),spectator->dataPtr(),dipoles[i]);
}
// radiation from a/c with final-final connection
else if (dipoles[i].type==FFa || dipoles[i].type==FFc) {
pre *= colourCoeff(emitter->dataPtr(),spectator->dataPtr(),in->dataPtr(),dipoles[i]);
}
double A = 2.*abs(pre)/Constants::twopi;
// factor due sampling choice
if(phaseOpt_==0) A *= ymax_;
// coupling factor
if(dipoles[i].interaction==ShowerInteraction::QCD)
A *= alphaS() ->overestimateValue();
else
A *= alphaEM()->overestimateValue();
Energy pTmax = 0.5*mb_*(1.-sqr(s_+e_));
// if no possible branching return
if ( pTmax < pTmin_ ) return particleMomenta;
// loop over the two regions
for(unsigned int j=0;j<2;++j) {
Energy pT=pTmax;
vector<Lorentz5Momentum> momenta(4);
while (pT >= pTmin_) {
double ymax;
// overestimate with flat y limit
if(phaseOpt_==0) {
pT *= pow(UseRandom::rnd(),(1./A));
ymax=ymax_;
}
// pT sampling including tighter pT dependent y limit
else {
pT = 2.*pTmax*exp(-sqrt(-2.*log(UseRandom::rnd())/A+sqr(log(2.*pTmax/pT))));
// choice of limit overestimate ln(2*pTmax/pT) (true limit acosh(pTmax/pT))
ymax = log(2.*pTmax/pT);
}
if (pT < pTmin_) break;
double phi = UseRandom::rnd()*Constants::twopi;
double y = ymax*(2.*UseRandom::rnd()-1.);
double xs, xe, xe_z, xg;
// check if the momenta are physical
if (!calcMomenta(j, pT, y, phi, xg, xs, xe,
xe_z, momenta))
continue;
// check if point lies within phase space
if (!psCheck(xg, xs)) continue;
// check if point lies within the dead-zone (if required)
if(inDeadZone && !inTotalDeadZone(xg,xs,dipoles,i)) continue;
// decay products for 3 body decay
PPtr inpart = in ->dataPtr()->produceParticle(momenta[0]);
ParticleVector decay3;
decay3.push_back(emitter ->dataPtr()->produceParticle(momenta[1]));
decay3.push_back(spectator->dataPtr()->produceParticle(momenta[2]));
if(dipoles[i].interaction==ShowerInteraction::QCD)
decay3.push_back(getParticleData(ParticleID::g )->produceParticle(momenta[3]));
else
decay3.push_back(getParticleData(ParticleID::gamma)->produceParticle(momenta[3]));
// decay products for 2 body decay
Lorentz5Momentum p1(ZERO,ZERO, lambda/2./mb_,(mb_/2.)*(1.+e2_-s2_),mb_*e_);
Lorentz5Momentum p2(ZERO,ZERO,-lambda/2./mb_,(mb_/2.)*(1.+s2_-e2_),mb_*s_);
ParticleVector decay2;
decay2.push_back(emitter ->dataPtr()->produceParticle(p1));
decay2.push_back(spectator->dataPtr()->produceParticle(p2));
if (dipoles[i].type==FFa || dipoles[i].type==IFa || dipoles[i].type==IFba) {
swap(decay2[0],decay2[1]);
swap(decay3[0],decay3[1]);
}
// calculate matrix element ratio R/B
double meRatio = matrixElementRatio(*inpart,decay2,decay3,Initialize,dipoles[i].interaction);
// calculate dipole factor
double dipoleSum(0.),numerator(0.);
for (int k=0; k<int(dipoles.size()); ++k) {
// skip dipoles which are not of the interaction being considered
if(dipoles[k].interaction!=dipoles[i].interaction) continue;
pair<double,double> dipole = calculateDipole(dipoles[k],*inpart,decay3);
dipoleSum += abs(dipole.first);
if (k==i) numerator = abs(dipole.second);
}
meRatio *= numerator/dipoleSum;
// calculate jacobian
Energy2 denom = (mb_-momenta[3].e())*momenta[2].vect().mag() -
momenta[2].e()*momenta[3].z();
InvEnergy2 J = (momenta[2].vect().mag2())/(lambda*denom);
// calculate weight
double weight = enhance_*meRatio*fabs(sqr(pT)*J)/pre/Constants::twopi;
if(dipoles[i].interaction==ShowerInteraction::QCD)
weight *= alphaS() ->ratio(pT*pT);
else
weight *= alphaEM()->ratio(pT*pT);
// accept point if weight > R
if (pT > pT_ && weight > UseRandom::rnd()) {
particleMomenta=momenta;
if (weight > 1.) {
generator()->log() << "WEIGHT PROBLEM " << fullName() << " " << weight << "\n";
generator()->log() << xe << " " << xs << " " << xg << "\n";
for(unsigned int ix=0;ix<particleMomenta.size();++ix)
generator()->log() << particleMomenta[ix]/GeV << "\n";
}
pT_ = pT;
break;
}
}
}
return particleMomenta;
}
bool PerturbativeDecayer::calcMomenta(int j, Energy pT, double y, double phi,
double& xg, double& xs, double& xe, double& xe_z,
vector<Lorentz5Momentum>& particleMomenta) {
// calculate xg
xg = 2.*pT*cosh(y) / mb_;
if (xg>(1. - sqr(e_ + s_)) || xg<0.) return false;
// calculate the two values of zs
double xT = 2.*pT / mb_;
double zg = 2.*pT*sinh(y) / mb_;
double A = (sqr(xT) - 4. * xg + 4.);
double B = 2. * zg * (s2_ - e2_ - xg + 1.);
double det = -4. * (-sqr(s2_) + (2. * e2_ + sqr(xT) - 2. * xg + 2.) * s2_ - sqr(e2_ + xg - 1.)) * sqr(xg - 2.);
if (det<0.) return false;
double zs= j==0 ? (-B+sqrt(det))/A : (-B-sqrt(det))/A;
// zs must be negative
if(zs>0.) return false;
xs = sqrt(sqr(zs)+4.*s2_);
// check value of xs is physical
if (xs>(1.+s2_-e2_) || xs<2.*s_) return false;
// calculate xe
xe = 2.-xs-xg;
// check value of xe is physical
if (xe>(1.+e2_-s2_) || xe<2.*e_) return false;
// calculate xe_z
xe_z = -zg-zs;
// calculate 4 momenta
particleMomenta[0].setE ( mb_);
particleMomenta[0].setX ( ZERO);
particleMomenta[0].setY ( ZERO);
particleMomenta[0].setZ ( ZERO);
particleMomenta[0].setMass( mb_);
particleMomenta[1].setE ( mb_*xe/2.);
particleMomenta[1].setX (-pT*cos(phi));
particleMomenta[1].setY (-pT*sin(phi));
particleMomenta[1].setZ ( mb_*xe_z/2.);
particleMomenta[1].setMass( mb_*e_);
particleMomenta[2].setE ( mb_*xs/2.);
particleMomenta[2].setX ( ZERO);
particleMomenta[2].setY ( ZERO);
particleMomenta[2].setZ ( mb_*zs/2.);
particleMomenta[2].setMass( mb_*s_);
particleMomenta[3].setE ( pT*cosh(y));
particleMomenta[3].setX ( pT*cos(phi));
particleMomenta[3].setY ( pT*sin(phi));
particleMomenta[3].setZ ( pT*sinh(y));
particleMomenta[3].setMass( ZERO);
return true;
}
bool PerturbativeDecayer::psCheck(const double xg, const double xs) {
// check is point is in allowed region of phase space
double xe_star = (1.-s2_+e2_-xg)/sqrt(1.-xg);
double xg_star = xg/sqrt(1.-xg);
if ((sqr(xe_star)-4.*e2_) < 1e-10) return false;
double xs_max = (4.+4.*s2_-sqr(xe_star+xg_star)+
sqr(sqrt(sqr(xe_star)-4.*e2_)+xg_star))/ 4.;
double xs_min = (4.+4.*s2_-sqr(xe_star+xg_star)+
sqr(sqrt(sqr(xe_star)-4.*e2_)-xg_star))/ 4.;
if (xs < xs_min || xs > xs_max) return false;
return true;
}
pair<double,double> PerturbativeDecayer::calculateDipole(const DipoleType & dipoleId,
const Particle & inpart,
const ParticleVector & decay3) {
// calculate dipole for decay b->ac
pair<double,double> dipole = make_pair(0.,0.);
double x1 = 2.*decay3[0]->momentum().e()/mb_;
double x2 = 2.*decay3[1]->momentum().e()/mb_;
double xg = 2.*decay3[2]->momentum().e()/mb_;
double mu12 = sqr(decay3[0]->mass()/mb_);
double mu22 = sqr(decay3[1]->mass()/mb_);
tcPDPtr part[3] = {inpart.dataPtr(),decay3[0]->dataPtr(),decay3[1]->dataPtr()};
if(dipoleId.type==FFa || dipoleId.type == IFa || dipoleId.type == IFba) {
swap(part[1],part[2]);
swap(x1,x2);
swap(mu12,mu22);
}
// radiation from b with initial-final connection
if (dipoleId.type==IFba || dipoleId.type==IFbc) {
dipole.first = -2./sqr(xg);
dipole.first *= colourCoeff(part[0],part[1],part[2],dipoleId);
}
// radiation from a/c with initial-final connection
else if (dipoleId.type==IFa || dipoleId.type==IFc) {
double z = 1. - xg/(1.-mu22+mu12);
dipole.first = (-2.*mu12/sqr(1.-x2+mu22-mu12) + (1./(1.-x2+mu22-mu12))*
(2./(1.-z)-dipoleSpinFactor(part[1],z)));
dipole.first *= colourCoeff(part[1],part[0],part[2],dipoleId);
}
// radiation from a/c with final-final connection
else if (dipoleId.type==FFa || dipoleId.type==FFc) {
double z = 1. + ((x1-1.+mu22-mu12)/(x2-2.*mu22));
double y = (1.-x2-mu12+mu22)/(1.-mu12-mu22);
double vt = sqrt((1.-sqr(e_+s_))*(1.-sqr(e_-s_)))/(1.-mu12-mu22);
double v = sqrt(sqr(2.*mu22+(1.-mu12-mu22)*(1.-y))-4.*mu22)
/(1.-y)/(1.-mu12-mu22);
if(part[1]->iSpin()!=PDT::Spin1) {
dipole.first = (1./(1.-x2+mu22-mu12))*
((2./(1.-z*(1.-y)))-vt/v*(dipoleSpinFactor(part[1],z)+(2.*mu12/(1.+mu22-mu12-x2))));
}
else {
dipole.first = (1./(1.-x2+mu22-mu12))*
(1./(1.-z*(1.-y))+1./(1.-(1.-z)*(1.-y))+(z*(1.-z)-2.)/v-vt/v*(2.*mu12/(1.+mu22-mu12-x2)));
dipole.second = (1./(1.-x2+mu22-mu12))*
(2./(1.-z*(1.-y))+(z*(1.-z)-2.)/v-vt/v*(2.*mu12/(1.+mu22-mu12-x2)));
dipole.second *= colourCoeff(part[1],part[2],part[0],dipoleId);
}
dipole.first *= colourCoeff(part[1],part[2],part[0],dipoleId);
}
// special for the case that all particles are gluons
else if(dipoleId.type==FFg) {
double z = (1.-x2)/xg;
double y = 1.-xg;
dipole.first = 1./(1.-xg)*(1./(1.-z*(1.-y))+1./(1.-(1.-z)*(1.-y))+(z*(1.-z)-2.));
dipole.first *= colourCoeff(part[1],part[2],part[0],dipoleId);
}
else
assert(false);
// coupling prefactors
if(dipole.second==0.) dipole.second=dipole.first;
dipole.first *= 8.*Constants::pi;
dipole.second *= 8.*Constants::pi;
// return the answer
return dipole;
}
double PerturbativeDecayer::dipoleSpinFactor(tcPDPtr part, double z){
// calculate the spin dependent component of the dipole
if (part->iSpin()==PDT::Spin0)
return 2.;
else if (part->iSpin()==PDT::Spin1Half)
return (1. + z);
else if (part->iSpin()==PDT::Spin1)
return -(z*(1.-z) - 1./(1.-z) + 1./z -2.);
return 0.;
}
namespace {
double colourCharge(PDT::Colour icol) {
switch(icol) {
case PDT::Colour0 :
return 0.;
case PDT::Colour3 : case PDT::Colour3bar :
return 4./3.;
case PDT::Colour8:
return 3.;
case PDT::Colour6 : case PDT::Colour6bar :
return 10./3.;
default :
assert(false);
return 0.;
}
}
}
double PerturbativeDecayer::colourCoeff(tcPDPtr emitter,
tcPDPtr spectator,
tcPDPtr other,
DipoleType dipole) {
if(dipole.interaction==ShowerInteraction::QCD) {
double emitterColour = colourCharge(emitter ->iColour());
double spectatorColour = colourCharge(spectator->iColour());
double otherColour = colourCharge(other ->iColour());
double val = 0.5*(sqr(emitterColour)+sqr(spectatorColour)-sqr(otherColour))/emitterColour;
return val;
}
else {
double val = double(emitter->iCharge()*spectator->iCharge())/9.;
// FF dipoles
if(dipole.type==FFa || dipole.type == FFc) return -val;
// IF dipoles
else return val;
}
}
void PerturbativeDecayer::getColourLines(RealEmissionProcessPtr real) {
// extract the particles
vector<tPPtr> branchingPart;
branchingPart.push_back(real->incoming()[0]);
for(unsigned int ix=0;ix<real->outgoing().size();++ix) {
branchingPart.push_back(real->outgoing()[ix]);
}
vector<unsigned int> sing,trip,atrip,oct,sex,asex;
for (size_t ib=0;ib<branchingPart.size()-1;++ib) {
if (branchingPart[ib]->dataPtr()->iColour()==PDT::Colour0 ) sing. push_back(ib);
else if(branchingPart[ib]->dataPtr()->iColour()==PDT::Colour3 ) trip. push_back(ib);
else if(branchingPart[ib]->dataPtr()->iColour()==PDT::Colour3bar) atrip.push_back(ib);
else if(branchingPart[ib]->dataPtr()->iColour()==PDT::Colour8 ) oct. push_back(ib);
else if(branchingPart[ib]->dataPtr()->iColour()==PDT::Colour6 ) sex. push_back(ib);
else if(branchingPart[ib]->dataPtr()->iColour()==PDT::Colour6bar) asex. push_back(ib);
}
// decaying colour singlet
if (branchingPart[0]->dataPtr()->iColour()==PDT::Colour0) {
// 0 -> 3 3bar
if (trip.size()==1 && atrip.size()==1) {
if(real->interaction()==ShowerInteraction::QCD) {
branchingPart[atrip[0]]->colourConnect(branchingPart[ 3 ]);
branchingPart[ 3 ]->colourConnect(branchingPart[trip[0]]);
}
else {
branchingPart[atrip[0]]->colourConnect(branchingPart[trip[0]]);
}
}
// 0 -> 8 8
else if (oct.size()==2 ) {
if(real->interaction()==ShowerInteraction::QCD) {
bool col = UseRandom::rndbool();
branchingPart[oct[0]]->colourConnect(branchingPart[ 3 ],col);
branchingPart[ 3 ]->colourConnect(branchingPart[oct[1]],col);
branchingPart[oct[1]]->colourConnect(branchingPart[oct[0]],col);
}
else {
branchingPart[oct[0]]->colourConnect(branchingPart[oct[1]]);
branchingPart[oct[1]]->colourConnect(branchingPart[oct[0]]);
}
}
else
assert(real->interaction()==ShowerInteraction::QED);
}
// decaying colour triplet
else if (branchingPart[0]->dataPtr()->iColour()==PDT::Colour3 ) {
// 3 -> 3 0
if (trip.size()==2 && sing.size()==1) {
if(real->interaction()==ShowerInteraction::QCD) {
branchingPart[3]->incomingColour(branchingPart[trip[0]]);
branchingPart[3]-> colourConnect(branchingPart[trip[1]]);
}
else {
branchingPart[trip[1]]->incomingColour(branchingPart[trip[0]]);
}
}
// 3 -> 3 8
else if (trip.size()==2 && oct.size()==1) {
if(real->interaction()==ShowerInteraction::QCD) {
// 8 emit incoming partner
if(real->emitter()==oct[0]&&real->spectator()==0) {
branchingPart[ 3 ]->incomingColour(branchingPart[trip[0]]);
branchingPart[ 3 ]-> colourConnect(branchingPart[oct[0] ]);
branchingPart[oct[0]]-> colourConnect(branchingPart[trip[1]]);
}
// 8 emit final spectator or vice veras
else {
branchingPart[oct[0]]->incomingColour(branchingPart[trip[0]]);
branchingPart[oct[0]]-> colourConnect(branchingPart[ 3 ]);
branchingPart[ 3 ]-> colourConnect(branchingPart[trip[1]]);
}
}
else {
branchingPart[oct[0]]->incomingColour(branchingPart[trip[0]]);
branchingPart[oct[0]]-> colourConnect(branchingPart[trip[1]]);
}
}
// 3 -> 3bar 3bar
else if(trip.size() ==1 && atrip.size()==2) {
if(real->interaction()==ShowerInteraction::QCD) {
if(real->emitter()==atrip[0]) {
branchingPart[3]->colourConnect(branchingPart[atrip[0]],true);
tColinePtr col[3] = {ColourLine::create(branchingPart[ trip[0]],false),
ColourLine::create(branchingPart[ 3],true ),
ColourLine::create(branchingPart[atrip[1]],true)};
col[0]->setSinkNeighbours(col[1],col[2]);
}
else {
branchingPart[3]->colourConnect(branchingPart[atrip[1]],true);
tColinePtr col[3] = {ColourLine::create(branchingPart[ trip[0]],false),
ColourLine::create(branchingPart[atrip[0]],true ),
ColourLine::create(branchingPart[ 3],true)};
col[0]->setSinkNeighbours(col[1],col[2]);
}
}
else {
tColinePtr col[3] = {ColourLine::create(branchingPart[ trip[0]],false),
ColourLine::create(branchingPart[atrip[0]],true ),
ColourLine::create(branchingPart[atrip[1]],true)};
col[0]->setSinkNeighbours(col[1],col[2]);
}
}
else
assert(false);
}
// decaying colour anti-triplet
else if (branchingPart[0]->dataPtr()->iColour()==PDT::Colour3bar) {
// 3bar -> 3bar 0
if (atrip.size()==2 && sing.size()==1) {
if(real->interaction()==ShowerInteraction::QCD) {
branchingPart[3]->incomingColour(branchingPart[atrip[0]],true);
branchingPart[3]-> colourConnect(branchingPart[atrip[1]],true);
}
else {
branchingPart[atrip[1]]->incomingColour(branchingPart[atrip[0]],true);
}
}
// 3 -> 3 8
else if (atrip.size()==2 && oct.size()==1){
if(real->interaction()==ShowerInteraction::QCD) {
// 8 emit incoming partner
if(real->emitter()==oct[0]&&real->spectator()==0) {
branchingPart[ 3 ]->incomingColour(branchingPart[atrip[0]],true);
branchingPart[ 3 ]-> colourConnect(branchingPart[oct[0] ],true);
branchingPart[oct[0]]-> colourConnect(branchingPart[atrip[1]],true);
}
// 8 emit final spectator or vice veras
else {
if(real->interaction()==ShowerInteraction::QCD) {
branchingPart[oct[0]]->incomingColour(branchingPart[atrip[0]],true);
branchingPart[oct[0]]-> colourConnect(branchingPart[ 3 ],true);
branchingPart[3]-> colourConnect(branchingPart[atrip[1]] ,true);
}
}
}
else {
branchingPart[oct[0]]->incomingColour(branchingPart[atrip[0]],true);
branchingPart[oct[0]]-> colourConnect(branchingPart[atrip[1]],true);
}
}
// 3bar -> 3 3
else if(atrip.size() ==1 && trip.size()==2) {
if(real->interaction()==ShowerInteraction::QCD) {
if(real->emitter()==trip[0]) {
branchingPart[3]->colourConnect(branchingPart[trip[0]],false);
tColinePtr col[3] = {ColourLine::create(branchingPart[atrip[0]],true ),
ColourLine::create(branchingPart[ 3],false),
ColourLine::create(branchingPart[ trip[1]],false)};
col[0]->setSourceNeighbours(col[1],col[2]);
}
else {
branchingPart[3]->colourConnect(branchingPart[trip[1]],false);
tColinePtr col[3] = {ColourLine::create(branchingPart[atrip[0]],true ),
ColourLine::create(branchingPart[ trip[0]],false),
ColourLine::create(branchingPart[ 3],false)};
col[0]->setSourceNeighbours(col[1],col[2]);
}
}
else {
tColinePtr col[3] = {ColourLine::create(branchingPart[atrip[0]],true ),
ColourLine::create(branchingPart[ trip[0]],false),
ColourLine::create(branchingPart[ trip[1]],false)};
col[0]->setSourceNeighbours(col[1],col[2]);
}
}
else
assert(false);
}
// decaying colour octet
else if(branchingPart[0]->dataPtr()->iColour()==PDT::Colour8 ) {
// 8 -> 3 3bar
if (trip.size()==1 && atrip.size()==1) {
if(real->interaction()==ShowerInteraction::QCD) {
// 3 emits
if(trip[0]==real->emitter()) {
branchingPart[3] ->incomingColour(branchingPart[oct[0]] );
branchingPart[3] -> colourConnect(branchingPart[trip[0]]);
branchingPart[atrip[0]]->incomingColour(branchingPart[oct[0]],true);
}
// 3bar emits
else {
branchingPart[3] ->incomingColour(branchingPart[oct[0]] ,true);
branchingPart[3] -> colourConnect(branchingPart[atrip[0]],true);
branchingPart[trip[0]]->incomingColour(branchingPart[oct[0]] );
}
}
else {
branchingPart[trip[0]]->incomingColour(branchingPart[oct[0]] );
branchingPart[atrip[0]]->incomingColour(branchingPart[oct[0]],true);
}
}
// 8 -> 8 0
else if (sing.size()==1 && oct.size()==2) {
if(real->interaction()==ShowerInteraction::QCD) {
bool col = UseRandom::rndbool();
branchingPart[ 3 ]->colourConnect (branchingPart[oct[1]], col);
branchingPart[ 3 ]->incomingColour(branchingPart[oct[0]], col);
branchingPart[oct[1]]->incomingColour(branchingPart[oct[0]],!col);
}
else {
branchingPart[oct[1]]->incomingColour(branchingPart[oct[0]]);
branchingPart[oct[1]]->incomingColour(branchingPart[oct[0]],true);
}
}
else
assert(false);
}
// sextet
else if(branchingPart[0]->dataPtr()->iColour() == PDT::Colour6) {
if(trip.size()==2) {
if(real->interaction()==ShowerInteraction::QCD) {
Ptr<MultiColour>::pointer parentColour =
dynamic_ptr_cast<Ptr<MultiColour>::pointer>
(branchingPart[0]->colourInfo());
if(trip[0]==real->emitter()) {
ColinePtr cline = new_ptr(ColourLine());
parentColour->colourLine(cline);
cline->addColoured(branchingPart[3]);
branchingPart[3] -> colourConnect(branchingPart[trip[0]]);
cline = new_ptr(ColourLine());
parentColour->colourLine(cline);
cline->addColoured(branchingPart[trip[1]]);
}
else {
ColinePtr cline = new_ptr(ColourLine());
parentColour->colourLine(cline);
cline->addColoured(branchingPart[3]);
branchingPart[3] -> colourConnect(branchingPart[trip[1]]);
cline = new_ptr(ColourLine());
parentColour->colourLine(cline);
cline->addColoured(branchingPart[trip[0]]);
}
}
else {
Ptr<MultiColour>::pointer parentColour =
dynamic_ptr_cast<Ptr<MultiColour>::pointer>
(branchingPart[0]->colourInfo());
for(unsigned int ix=0;ix<2;++ix) {
ColinePtr cline = new_ptr(ColourLine());
parentColour->colourLine(cline);
cline->addColoured(branchingPart[trip[ix]]);
}
}
}
else
assert(false);
}
// antisextet
else if(branchingPart[0]->dataPtr()->iColour() == PDT::Colour6bar) {
if(atrip.size()==2) {
if(real->interaction()==ShowerInteraction::QCD) {
Ptr<MultiColour>::pointer parentColour =
dynamic_ptr_cast<Ptr<MultiColour>::pointer>
(branchingPart[0]->colourInfo());
if(atrip[0]==real->emitter()) {
ColinePtr cline = new_ptr(ColourLine());
parentColour->antiColourLine(cline);
cline->addAntiColoured(branchingPart[3]);
branchingPart[3]->antiColourConnect(branchingPart[atrip[0]]);
cline = new_ptr(ColourLine());
parentColour->antiColourLine(cline);
cline->addAntiColoured(branchingPart[atrip[1]]);
}
else {
ColinePtr cline = new_ptr(ColourLine());
parentColour->antiColourLine(cline);
cline->addAntiColoured(branchingPart[3]);
branchingPart[3]->antiColourConnect(branchingPart[atrip[1]]);
cline = new_ptr(ColourLine());
parentColour->antiColourLine(cline);
cline->addAntiColoured(branchingPart[trip[0]]);
}
}
else {
Ptr<MultiColour>::pointer parentColour =
dynamic_ptr_cast<Ptr<MultiColour>::pointer>
(branchingPart[0]->colourInfo());
for(unsigned int ix=0;ix<2;++ix) {
ColinePtr cline = new_ptr(ColourLine());
parentColour->antiColourLine(cline);
cline->addColoured(branchingPart[atrip[ix]],true);
}
}
}
else
assert(false);
}
else
assert(false);
}
PerturbativeDecayer::phaseSpaceRegion
PerturbativeDecayer::inInitialFinalDeadZone(double xg, double xa,
double a, double c) const {
double lam = sqrt(1.+a*a+c*c-2.*a-2.*c-2.*a*c);
double kappab = 1.+0.5*(1.-a+c+lam);
double kappac = kappab-1.+c;
double kappa(0.);
// check whether or not in the region for emission from c
double r = 0.5;
if(c!=0.) r += 0.5*c/(1.+a-xa);
double pa = sqrt(sqr(xa)-4.*a);
double z = ((2.-xa)*(1.-r)+r*pa-xg)/pa;
if(z<1. && z>0.) {
kappa = (1.+a-c-xa)/(z*(1.-z));
if(kappa<kappac)
return emissionFromC;
}
// check in region for emission from b (T1)
double cq = sqr(1.+a-c)-4*a;
double bq = -2.*kappab*(1.-a-c);
double aq = sqr(kappab)-4.*a*(kappab-1);
double dis = sqr(bq)-4.*aq*cq;
z=1.-(-bq-sqrt(dis))/2./aq;
double w = 1.-(1.-z)*(kappab-1.);
double xgmax = (1.-z)*kappab;
// possibly in T1 region
if(xg<xgmax) {
z = 1.-xg/kappab;
kappa=kappab;
}
// possibly in T2 region
else {
aq = 4.*a;
bq = -4.*a*(2.-xg);
cq = sqr(1.+a-c-xg);
dis = sqr(bq)-4.*aq*cq;
z = (-bq-sqrt(dis))/2./aq;
kappa = xg/(1.-z);
}
// compute limit on xa
double u = 1.+a-c-(1.-z)*kappa;
w = 1.-(1.-z)*(kappa-1.);
double v = sqr(u)-4.*z*a*w;
if(v<0. && v>-1e-10) v= 0.;
v = sqrt(v);
if(xa<0.5*((u+v)/w+(u-v)/z)) {
if(xg<xgmax)
return emissionFromA1;
else if(useMEforT2_)
return deadZone;
else
return emissionFromA2;
}
else
return deadZone;
}
PerturbativeDecayer::phaseSpaceRegion
PerturbativeDecayer::inFinalFinalDeadZone(double xb, double xc,
double b, double c) const {
// basic kinematics
double lam = sqrt(1.+b*b+c*c-2.*b-2.*c-2.*b*c);
// check whether or not in the region for emission from b
double r = 0.5;
if(b!=0.) r+=0.5*b/(1.+c-xc);
double pc = sqrt(sqr(xc)-4.*c);
double z = -((2.-xc)*r-r*pc-xb)/pc;
if(z<1. and z>0.) {
if((1.-b+c-xc)/(z*(1.-z))<0.5*(1.+b-c+lam)) return emissionFromB;
}
// check whether or not in the region for emission from c
r = 0.5;
if(c!=0.) r+=0.5*c/(1.+b-xb);
double pb = sqrt(sqr(xb)-4.*b);
z = -((2.-xb)*r-r*pb-xc)/pb;
if(z<1. and z>0.) {
if((1.-c+b-xb)/(z*(1.-z))<0.5*(1.-b+c+lam)) return emissionFromC;
}
return deadZone;
}
bool PerturbativeDecayer::inTotalDeadZone(double xg, double xs,
const vector<DipoleType> & dipoles,
int i) {
double xb,xc,b,c;
if(dipoles[i].type==FFa || dipoles[i].type == IFa || dipoles[i].type == IFba) {
xc = xs;
xb = 2.-xg-xs;
b = e2_;
c = s2_;
}
else {
xb = xs;
xc = 2.-xg-xs;
b = s2_;
c = e2_;
}
for(unsigned int ix=0;ix<dipoles.size();++ix) {
if(dipoles[ix].interaction!=dipoles[i].interaction)
continue;
// should also remove negative QED dipoles but shouldn't be an issue unless we
// support QED ME corrections
switch (dipoles[ix].type) {
case FFa :
if(inFinalFinalDeadZone(xb,xc,b,c)!=deadZone) return false;
break;
case FFc :
if(inFinalFinalDeadZone(xc,xb,c,b)!=deadZone) return false;
break;
case IFa : case IFba:
if(inInitialFinalDeadZone(xg,xc,c,b)!=deadZone) return false;
break;
case IFc : case IFbc:
if(inInitialFinalDeadZone(xg,xb,b,c)!=deadZone) return false;
break;
case FFg:
break;
}
}
return true;
}

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