EventUtils.h

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2023  Laurent Forthomme
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef CepGenAddOns_Common_EventUtils_h
#define CepGenAddOns_Common_EventUtils_h
 
#include "CepGen/Event/Event.h"
#include "CepGen/Physics/PDG.h"
 
using namespace std;
 
namespace cepgen {
  namespace utils {
    Event generateLPAIREvent() {
      auto evt = cepgen::Event::minimal(2);  // one event with two outgoing particles (leptons)
 
      // generate positive-z incoming beam kinematics
      auto& ib1 = evt.oneWithRole(cepgen::Particle::IncomingBeam1);
      ib1.setPdgId(cepgen::PDG::proton);
      ib1.setMomentum(cepgen::Momentum::fromPxPyPzE(0., 0., 6.5e3, -1.), false);
 
      // generate negative-z incoming beam kinematics
      auto& ib2 = evt.oneWithRole(cepgen::Particle::IncomingBeam2);
      ib2.setPdgId(cepgen::PDG::proton);
      ib2.setMomentum(cepgen::Momentum::fromPxPyPzE(0., 0., -6.5e3, -1.), false);
 
      // generate positive-z outgoing beam kinematics
      auto& ob1 = evt.oneWithRole(cepgen::Particle::OutgoingBeam1);
      ob1.setPdgId(cepgen::PDG::proton);
      ob1.setMomentum(cepgen::Momentum::fromPxPyPzE(-7.875321, 8.186351, 6.403512e3, 6.403704e3), true);
 
      // generate negative-z outgoing beam kinematics
      auto& ob2 = evt.oneWithRole(cepgen::Particle::OutgoingBeam2);
      ob2.setPdgId(cepgen::PDG::proton);
      ob2.setMomentum(cepgen::Momentum::fromPxPyPzE(-2.725610e-2, 7.565269e-3, -6.425336e3, 6.425336e3), false);
 
      // generate positive-z incoming photon kinematics
      auto& parton1 = evt.oneWithRole(cepgen::Particle::Parton1);
      parton1.setPdgId(cepgen::PDG::photon);
      parton1.setMomentum(cepgen::Momentum::fromPxPyPzE(7.875321, -8.186351, 9.648800e1, 9.629600e1), true);
 
      // generate negative-z incoming photon kinematics
      auto& parton2 = evt.oneWithRole(cepgen::Particle::Parton2);
      parton2.setPdgId(cepgen::PDG::photon);
      parton2.setMomentum(cepgen::Momentum::fromPxPyPzE(2.725610e-2, -7.565269e-3, -7.466409e1, 7.466409e1), true);
      evt.oneWithRole(cepgen::Particle::Intermediate).setMomentum(parton1.momentum() + parton2.momentum(), true);
 
      // generate dilepton system kinematics
      auto oc = evt[cepgen::Particle::CentralSystem];
      oc[0].get().setPdgId(cepgen::PDG::muon, -1);
      oc[0].get().setMomentum(cepgen::Momentum::fromPxPyPzE(2.193109e1, -6.725967e1, -4.248568e1, 8.252200e1), false);
      oc[1].get().setPdgId(cepgen::PDG::muon, +1);
      oc[1].get().setMomentum(cepgen::Momentum::fromPxPyPzE(-1.402852e1, 5.906575e1, 6.430959e1, 8.843809e1), false);
      return evt;
    }
  }  // namespace utils
}  // namespace cepgen
 
#endif