PythiaEventInterface.h

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/*
 *  CepGen: a central exclusive processes event generator
 *  Copyright (C) 2016-2023  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_EventInterfaces_PythiaEventInterface_h
#define CepGenAddOns_EventInterfaces_PythiaEventInterface_h
 
#include <Pythia8/Pythia.h>
 
#include <unordered_map>
 
namespace cepgen {
  class RunParameters;
  class Event;
  class Particle;
}  // namespace cepgen
 
namespace Pythia8 {
  class CepGenEvent : public LHAup {
  public:
    enum struct Type {
      centralAndPartons,          
      centralAndBeamRemnants,     
      centralAndFullBeamRemnants  
    };
    explicit CepGenEvent();
    void initialise(const cepgen::RunParameters&);
    void feedEvent(const cepgen::Event& ev, const Type& type);
    void setCrossSection(int id, double cross_section, double cross_section_err);
    void setProcess(int id, double cross_section, double q2_scale, double alpha_qed, double alpha_qcd);
 
    void addComments(const std::string& comments);
 
    unsigned short cepgenId(unsigned short py_id) const;
    unsigned short pythiaId(unsigned short cg_id) const;
    void addCepGenParticle(const cepgen::Particle& part,
                           int status = INVALID_ID,
                           const std::pair<int, int>& mothers = {0, 0},
                           const std::pair<int, int>& colours = {0, 0});
    void addCorresp(unsigned short py_id, unsigned short cg_id);
    void dumpCorresp() const;
 
    static constexpr unsigned short INVALID_ID = 999;        
    static constexpr unsigned short MIN_COLOUR_INDEX = 501;  
 
    inline bool setInit() override { return true; }
#if defined(PYTHIA_VERSION_INTEGER) && PYTHIA_VERSION_INTEGER >= 8200
    bool setEvent(int) override { return true; }
#else
    bool setEvent(int, double) override { return true; }
#endif
 
  private:
    std::pair<int, int> findMothers(const cepgen::Event& ev, const cepgen::Particle& p) const;
    const double mp_, mp2_;
    bool inel1_{false}, inel2_{false};
    std::unordered_map<unsigned short, unsigned short> py_cg_corresp_;
    const cepgen::RunParameters* params_{nullptr};  // borrowed
  };
}  // namespace Pythia8
#endif