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#include <memory>
#include "GeneratorInterface/Core/interface/GeneratorFilter.h"
#include "GeneratorInterface/ExternalDecays/interface/ExternalDecayDriver.h"
#include "GeneratorInterface/Pythia8Interface/interface/Py8GunBase.h"
namespace gen {
class Py8JetGun : public Py8GunBase {
public:
Py8JetGun(edm::ParameterSet const&);
~Py8JetGun() override {}
bool generatePartonsAndHadronize() override;
const char* classname() const override;
private:
// PtGun particle(s) characteristics
double fMinEta;
double fMaxEta;
double fMinP;
double fMaxP;
double fMinE;
double fMaxE;
};
// implementation
//
Py8JetGun::Py8JetGun(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);
fMinP = pgun_params.getParameter<double>("MinP"); // , 0.);
fMaxP = pgun_params.getParameter<double>("MaxP"); // , 0.);
fMinE = pgun_params.getParameter<double>("MinE"); // , 0.);
fMaxE = pgun_params.getParameter<double>("MaxE"); // , 0.);
}
bool Py8JetGun::generatePartonsAndHadronize() {
fMasterGen->event.reset();
int NTotParticles = fPartIDs.size();
// energy below is dummy, it is not used
(fMasterGen->event).append(990, -11, 0, 0, 2, 1 + NTotParticles, 0, 0, 0., 0., 0., 15000., 15000.);
double totPx = 0.;
double totPy = 0.;
double totPz = 0.;
double totE = 0.;
double totM = 0.;
double phi, eta, the, ee, pp;
for (size_t i = 0; i < fPartIDs.size(); i++) {
int particleID = fPartIDs[i]; // this is PDG
phi = 2. * M_PI * randomEngine().flat();
the = acos(-1. + 2. * randomEngine().flat());
// from input
//
ee = (fMaxE - fMinE) * randomEngine().flat() + fMinE;
double mass = (fMasterGen->particleData).m0(particleID);
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);
}
(fMasterGen->event).append(particleID, 1, 1, 0, 0, 0, 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);
// values for computing total mass
//
totPx += px;
totPy += py;
totPz += pz;
totE += ee;
}
totM = sqrt(totE * totE - (totPx * totPx + totPy * totPy + totPz * totPz));
//now the boost (from input params)
//
pp = (fMaxP - fMinP) * randomEngine().flat() + fMinP;
ee = sqrt(totM * totM + pp * pp);
//the boost direction (from input params)
//
phi = (fMaxPhi - fMinPhi) * randomEngine().flat() + fMinPhi;
eta = (fMaxEta - fMinEta) * randomEngine().flat() + fMinEta;
the = 2. * atan(exp(-eta));
double betaX = pp / ee * std::sin(the) * std::cos(phi);
double betaY = pp / ee * std::sin(the) * std::sin(phi);
double betaZ = pp / ee * std::cos(the);
// boost all particles
//
(fMasterGen->event).bst(betaX, betaY, betaZ);
if (!fMasterGen->next())
return false;
event() = std::make_unique<HepMC::GenEvent>();
return toHepMC.fill_next_event(fMasterGen->event, event().get());
}
const char* Py8JetGun::classname() const { return "Py8JetGun"; }
typedef edm::GeneratorFilter<gen::Py8JetGun, gen::ExternalDecayDriver> Pythia8JetGun;
} // namespace gen
using gen::Pythia8JetGun;
DEFINE_FWK_MODULE(Pythia8JetGun);
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