EventReweighter.hh

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#pragma once
 
#include <array>
#include <functional>
#include <utility>
#include <vector>
 
#include "HEJ/config.hh"
#include "HEJ/event_types.hh"
#include "HEJ/MatrixElement.hh"
#include "HEJ/PDF.hh"
#include "HEJ/PDG_codes.hh"
#include "HEJ/RNG.hh"
#include "HEJ/ScaleFunction.hh"
 
namespace LHEF {
  class HEPRUP;
}
 
namespace HEJ{
  class Event;
  class Weights;
 
 
  struct Beam{
    double E;                                
    std::array<ParticleID, 2> type;          
  };
 
  class EventReweighter{
    using EventType = event_type::EventType;
  public:
 
    EventReweighter(
        Beam beam,                            
        int pdf_id,                           
        ScaleGenerator scale_gen,             
        EventReweighterConfig conf,           
        HEJ::RNG & ran                       
    );
 
    EventReweighter(
        LHEF::HEPRUP const & heprup,          
        ScaleGenerator scale_gen,             
        EventReweighterConfig conf,           
        HEJ::RNG & ran                       
    );
 
    PDF const & pdf() const;
 
 
 
    std::vector<Event> reweight(
        Event const & ev,
        int num_events
    );
 
  private:
 
    template<typename... T>
    PDF const & pdf(T&& ...);
 
    std::vector<Event> gen_res_events(
        Event const & ev, int num_events
    );
    std::vector<Event> rescale(
        Event const & Born_ev, std::vector<Event> events
    ) const;
 
    bool jets_pass_resummation_cuts(Event const & ev) const;
 
    Weights pdf_factors(Event const & ev) const;
 
    Weights matrix_elements(Event const & ev) const;
 
    Weights fixed_order_scale_ME(Event const & ev) const;
 
    double tree_matrix_element(Event const & ev) const;
 
 
    EventReweighterConfig param_;
 
    double E_beam_;
 
    PDF pdf_;
 
    MatrixElement MEt2_;
    ScaleGenerator scale_gen_;
    std::reference_wrapper<HEJ::RNG> ran_;
  };
 
  template<typename... T>
  PDF const & EventReweighter::pdf(T&&... t){
    return pdf_ = PDF{std::forward<T>(t)...};
  }
 
}