EWConstants.hh

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#pragma once
 
#include <cmath>
#include <memory>
 
#include "HEJ/PDG_codes.hh"
#include "HEJ/exceptions.hh"
 
namespace HEJ {
  struct ParticleProperties {
    double mass;  
    double width; 
  };
 
  class EWConstants {
  public:
    EWConstants() = default;
    constexpr EWConstants(
      double vev, 
      ParticleProperties Wprop, 
      ParticleProperties Zprop, 
      ParticleProperties Hprop  
    ): set_{true}, vev_{vev}, Wprop_{std::move(Wprop)},
        Zprop_{std::move(Zprop)}, Hprop_{std::move(Hprop)}
    {}
    void set_vevWZH(
      double vev, 
      ParticleProperties Wprop, 
      ParticleProperties Zprop, 
      ParticleProperties Hprop  
    ){
      set_ = true; vev_= vev; Wprop_= std::move(Wprop);
      Zprop_= std::move(Zprop); Hprop_= std::move(Hprop);
    }
    double vev()     const {check_set(); return vev_;}
    ParticleProperties const & Wprop() const {check_set(); return Wprop_;}
    ParticleProperties const & Zprop() const {check_set(); return Zprop_;}
    ParticleProperties const & Hprop() const {check_set(); return Hprop_;}
    ParticleProperties const & prop(ParticleID const id) const {
      using namespace pid;
      switch(id){
      case Wp:
      case Wm:
        return Wprop();
      case Z:
        return Zprop();
      case h:
        return Hprop();
      default:
        throw std::invalid_argument("No properties available for particle "+name(id));
      }
    }
    double cos_tw()   const {return Wprop().mass/Zprop().mass;}
    double cos2_tw()  const {return cos_tw()*cos_tw();}
    double sin_tw()   const {return std::sqrt(sin2_tw());}
    double sin2_tw()  const {return 1. - cos2_tw();}
    double alpha_em() const {return e2()/4./M_PI;}
    double alpha_w()  const {return gw2()/2.;}
 
  private:
    double gw2() const {return 4*Wprop().mass/vev()*Wprop().mass/vev();}
    double e2()  const {return gw2()*sin2_tw();}
    void check_set() const {
      if(!set_) throw std::invalid_argument("EW constants not specified");
    }
    bool set_{false};
    double vev_{};
    ParticleProperties Wprop_{};
    ParticleProperties Zprop_{};
    ParticleProperties Hprop_{};
  };
} // namespace HEJ