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Merge pull request #29153 from pasmuss/from-CMSSW_9_3_17
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Changing handling of color indexes and anti particle creation for pythia8 EGun (9_3_X backport)
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cmsbuild committed Mar 10, 2020
2 parents fcdb6e2 + fb25bc0 commit af645ac
Showing 1 changed file with 103 additions and 98 deletions.
201 changes: 103 additions & 98 deletions GeneratorInterface/Pythia8Interface/plugins/Py8EGun.cc
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Expand Up @@ -6,115 +6,120 @@

namespace gen {

class Py8EGun : public Py8GunBase {

public:

Py8EGun( edm::ParameterSet const& );
~Py8EGun() {}

bool generatePartonsAndHadronize() override;
const char* classname() const override;

private:

// EGun particle(s) characteristics
double fMinEta;
double fMaxEta;
double fMinE ;
double fMaxE ;
bool fAddAntiParticle;

};

// implementation
//
Py8EGun::Py8EGun( edm::ParameterSet const& ps )
: Py8GunBase(ps)
{

// ParameterSet defpset ;
edm::ParameterSet pgun_params =
ps.getParameter<edm::ParameterSet>("PGunParameters"); // , defpset ) ;
fMinEta = pgun_params.getParameter<double>("MinEta"); // ,-2.2);
fMaxEta = pgun_params.getParameter<double>("MaxEta"); // , 2.2);
fMinE = pgun_params.getParameter<double>("MinE"); // , 0.);
fMaxE = pgun_params.getParameter<double>("MaxE"); // , 0.);
fAddAntiParticle = pgun_params.getParameter<bool>("AddAntiParticle"); //, false) ;

}

bool Py8EGun::generatePartonsAndHadronize()
{

fMasterGen->event.reset();

for ( size_t i=0; i<fPartIDs.size(); i++ )
{

int particleID = fPartIDs[i]; // this is PDG - need to convert to Py8 ???

double phi = (fMaxPhi-fMinPhi) * randomEngine().flat() + fMinPhi;
double ee = (fMaxE-fMinE) * randomEngine().flat() + fMinE;
double eta = (fMaxEta-fMinEta) * randomEngine().flat() + fMinEta;
double the = 2.*atan(exp(-eta));

double mass = (fMasterGen->particleData).m0( particleID );

double pp = sqrt( ee*ee - mass*mass );
class Py8EGun : public Py8GunBase {
public:
Py8EGun(edm::ParameterSet const&);
~Py8EGun() override {}

bool generatePartonsAndHadronize() override;
const char* classname() const override;

private:
// EGun particle(s) characteristics
double fMinEta;
double fMaxEta;
double fMinE;
double fMaxE;
bool fAddAntiParticle;
};

// implementation
//
Py8EGun::Py8EGun(edm::ParameterSet const& ps) : Py8GunBase(ps) {
// ParameterSet defpset ;
edm::ParameterSet pgun_params = ps.getParameter<edm::ParameterSet>("PGunParameters"); // , defpset ) ;
fMinEta = pgun_params.getParameter<double>("MinEta"); // ,-2.2);
fMaxEta = pgun_params.getParameter<double>("MaxEta"); // , 2.2);
fMinE = pgun_params.getParameter<double>("MinE"); // , 0.);
fMaxE = pgun_params.getParameter<double>("MaxE"); // , 0.);
fAddAntiParticle = pgun_params.getParameter<bool>("AddAntiParticle"); //, false) ;
}

bool Py8EGun::generatePartonsAndHadronize() {
fMasterGen->event.reset();

int colorindex = 101;

for (size_t i = 0; i < fPartIDs.size(); i++) {
int particleID = fPartIDs[i]; // this is PDG - need to convert to Py8 ???
if ((std::abs(particleID) <= 6 || particleID == 21) && !(fAddAntiParticle)) {
throw cms::Exception("PythiaError") << "Attempting to generate quarks or gluons without setting "
"AddAntiParticle to true. This will not handle color properly."
<< std::endl;
}

double phi = (fMaxPhi - fMinPhi) * randomEngine().flat() + fMinPhi;
double ee = (fMaxE - fMinE) * randomEngine().flat() + fMinE;
double eta = (fMaxEta - fMinEta) * randomEngine().flat() + fMinEta;
double the = 2. * atan(exp(-eta));

double mass = (fMasterGen->particleData).m0(particleID);

double pp = sqrt(ee * ee - mass * mass);
double px = pp * sin(the) * cos(phi);
double py = pp * sin(the) * sin(phi);
double pz = pp * cos(the);

if ( !((fMasterGen->particleData).isParticle( particleID )) )
{
particleID = std::fabs(particleID) ;
if (!((fMasterGen->particleData).isParticle(particleID))) {
particleID = std::fabs(particleID);
}
(fMasterGen->event).append( particleID, 1, 0, 0, px, py, pz, ee, mass );
int eventSize = (fMasterGen->event).size()-1;
// -log(flat) = exponential distribution
double tauTmp = -(fMasterGen->event)[eventSize].tau0() * log(randomEngine().flat());
(fMasterGen->event)[eventSize].tau( tauTmp );


// Here also need to add anti-particle (if any)
// otherwise just add a 2nd particle of the same type
// (for example, gamma)
//
if ( fAddAntiParticle )
{
if ( (fMasterGen->particleData).isParticle( -particleID ) )
{
(fMasterGen->event).append( -particleID, 1, 0, 0, -px, -py, -pz, ee, mass );
}
else
{
(fMasterGen->event).append( particleID, 1, 0, 0, -px, -py, -pz, ee, mass );
}
eventSize = (fMasterGen->event).size()-1;
// -log(flat) = exponential distribution
tauTmp = -(fMasterGen->event)[eventSize].tau0() * log(randomEngine().flat());
(fMasterGen->event)[eventSize].tau( tauTmp );
if (1 <= std::abs(particleID) && std::abs(particleID) <= 6) { // quarks
(fMasterGen->event).append(particleID, 23, colorindex, 0, px, py, pz, ee, mass);
if (!fAddAntiParticle)
colorindex += 1;
} else if (std::abs(particleID) == 21) { // gluons
(fMasterGen->event).append(21, 23, colorindex, colorindex + 1, px, py, pz, ee, mass);
if (!fAddAntiParticle) {
colorindex += 2;
}
}
// other
else {
(fMasterGen->event).append(particleID, 1, 0, 0, px, py, pz, ee, mass);
int eventSize = (fMasterGen->event).size() - 1;
// -log(flat) = exponential distribution
double tauTmp = -(fMasterGen->event)[eventSize].tau0() * log(randomEngine().flat());
(fMasterGen->event)[eventSize].tau(tauTmp);
}

// Here also need to add anti-particle (if any)
// otherwise just add a 2nd particle of the same type
// (for example, gamma)
//
if (fAddAntiParticle) {
if (1 <= std::abs(particleID) && std::abs(particleID) <= 6) { // quarks
(fMasterGen->event).append(-particleID, 23, 0, colorindex, -px, -py, -pz, ee, mass);
colorindex += 1;
} else if (std::abs(particleID) == 21) { // gluons
(fMasterGen->event).append(21, 23, colorindex + 1, colorindex, -px, -py, -pz, ee, mass);
colorindex += 2;
} else {
if ((fMasterGen->particleData).isParticle(-particleID)) {
(fMasterGen->event).append(-particleID, 1, 0, 0, -px, -py, -pz, ee, mass);
} else {
(fMasterGen->event).append(particleID, 1, 0, 0, -px, -py, -pz, ee, mass);
}
int eventSize = (fMasterGen->event).size() - 1;
// -log(flat) = exponential distribution
double tauTmp = -(fMasterGen->event)[eventSize].tau0() * log(randomEngine().flat());
(fMasterGen->event)[eventSize].tau(tauTmp);
}
}
}

}

if ( !fMasterGen->next() ) return false;
evtGenDecay();
if (!fMasterGen->next())
return false;
evtGenDecay();

event().reset(new HepMC::GenEvent);
return toHepMC.fill_next_event( fMasterGen->event, event().get() );

}
event().reset(new HepMC::GenEvent);
return toHepMC.fill_next_event(fMasterGen->event, event().get());
}

const char* Py8EGun::classname() const
{
return "Py8EGun";
}
const char* Py8EGun::classname() const { return "Py8EGun"; }

typedef edm::GeneratorFilter<gen::Py8EGun, gen::ExternalDecayDriver> Pythia8EGun;
typedef edm::GeneratorFilter<gen::Py8EGun, gen::ExternalDecayDriver> Pythia8EGun;

} // end namespace
} // namespace gen

using gen::Pythia8EGun;
DEFINE_FWK_MODULE(Pythia8EGun);

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