Pythia6JetGun.cc

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#include <iostream>

#include "Pythia6JetGun.h"

#include "FWCore/Utilities/interface/Exception.h"

#include "FWCore/Framework/interface/EventSetup.h"

#include "SimDataFormats/GeneratorProducts/interface/HepMCProduct.h"

#include "FWCore/Framework/interface/MakerMacros.h"

using namespace edm;
using namespace gen;

Pythia6JetGun::Pythia6JetGun(const ParameterSet& pset)
    : Pythia6ParticleGun(pset), fMinEta(0.), fMaxEta(0.), fMinE(0.), fMaxE(0.), fMinP(0.), fMaxP(0.) {
  ParameterSet pgun_params = pset.getParameter<ParameterSet>("PGunParameters");
  fMinEta = pgun_params.getParameter<double>("MinEta");
  fMaxEta = pgun_params.getParameter<double>("MaxEta");
  fMinE = pgun_params.getParameter<double>("MinE");
  fMaxE = pgun_params.getParameter<double>("MaxE");
  fMinP = pgun_params.getParameter<double>("MinP");
  fMaxP = pgun_params.getParameter<double>("MaxP");
}

Pythia6JetGun::~Pythia6JetGun() {}

void Pythia6JetGun::generateEvent(CLHEP::HepRandomEngine*) {
  Pythia6Service::InstanceWrapper guard(fPy6Service);  // grab Py6 instance

  // now actualy, start cooking up the event gun
  //

  // 1st, primary vertex
  //
  HepMC::GenVertex* Vtx = new HepMC::GenVertex(HepMC::FourVector(0., 0., 0.));

  // here re-create fEvt (memory)
  //
  fEvt = new HepMC::GenEvent();

  int ip = 1;
  double totPx = 0.;
  double totPy = 0.;
  double totPz = 0.;
  double totE = 0.;
  double totM = 0.;
  double phi, eta, the, ee, pp;
  int dum = 0;
  for (size_t i = 0; i < fPartIDs.size(); i++) {
    int particleID = fPartIDs[i];  // this is PDG - need to convert to Py6 !!!
    int py6PID = HepPID::translatePDTtoPythia(particleID);

    // internal numbers
    //
    phi = 2. * M_PI * pyr_(&dum);
    the = std::acos(-1. + 2. * pyr_(&dum));

    // from input
    //
    ee = (fMaxE - fMinE) * pyr_(&dum) + fMinE;

    // fill p(ip,5) (in PYJETS) with mass value right now,
    // because the (hardcoded) mstu(10)=1 will make py1ent
    // pick the mass from there
    double mass = pymass_(py6PID);
    pyjets.p[4][ip - 1] = mass;

    // add entry to py6
    //
    py1ent_(ip, py6PID, ee, the, phi);

    // values for computing total mass
    //
    totPx += pyjets.p[0][ip - 1];
    totPy += pyjets.p[1][ip - 1];
    totPz += pyjets.p[2][ip - 1];
    totE += pyjets.p[3][ip - 1];

    ip++;

  }  // end forming up py6 record of the jet

  // compute total mass
  //
  totM = std::sqrt(totE * totE - (totPx * totPx + totPy * totPy + totPz * totPz));

  //now the boost (from input params)
  //
  pp = (fMaxP - fMinP) * pyr_(&dum) + fMinP;
  ee = std::sqrt(totM * totM + pp * pp);

  //the boost direction (from input params)
  //
  phi = (fMaxPhi - fMinPhi) * pyr_(&dum) + fMinPhi;
  eta = (fMaxEta - fMinEta) * pyr_(&dum) + 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
  // the first 2 params (-1) tell to boost all (fisrt-to-last),
  // and the next 2 params (0.) tell no rotation
  //
  int first = -1, last = -1;
  double rothe = 0, rophi = 0.;

  pyrobo_(first, last, rothe, rophi, betaX, betaY, betaZ);

  // event should be formed from boosted record !!!
  // that's why additional loop
  //
  for (int i = 0; i < pyjets.n; i++) {
    HepMC::FourVector p(pyjets.p[0][i], pyjets.p[1][i], pyjets.p[2][i], pyjets.p[3][i]);
    HepMC::GenParticle* Part = new HepMC::GenParticle(p, HepPID::translatePythiatoPDT(pyjets.k[1][i]), 1);
    Part->suggest_barcode(i + 1);
    Vtx->add_particle_out(Part);
  }
  fEvt->add_vertex(Vtx);

  // run pythia
  pyexec_();

  return;
}

DEFINE_FWK_MODULE(Pythia6JetGun);