constants.hpp

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#pragma once
#include <cmath>

namespace QQbar_threshold{

  constexpr double alpha_s_mZ = 0.1184;
  constexpr double alpha_mZ = 1/128.944;
  constexpr double alpha_Y = 1/132.274;
  constexpr double mu_alpha_Y = 10.2;
  constexpr double mZ = 91.1876;
  constexpr double mW = 80.385;
  constexpr double me = 0.0005109989461;

  constexpr double G_F = 0.000011663787;

  constexpr double m_Higgs = 125.;

  constexpr double alpha_QED = 1/137.035999074;

  constexpr double e_u = 2./3.;
  constexpr double e_d = -1./3.;
  constexpr double e = -1;
  constexpr double cw2 = mW*mW/(mZ*mZ);
  constexpr double sw2 = 1 - cw2;

  constexpr double T3_nu = 1./2.;
  constexpr double T3_e = -1./2.;
  constexpr double T3_u = 1./2.;
  constexpr double T3_d = -1./2.;

  constexpr double mb_SI = 4.203;
  constexpr double mu_thr = 2*mb_SI;

  constexpr int nl_bottom = 4;
  constexpr int nl_top = 5;

  constexpr double mu_f_bottom = 2.;

  constexpr double mu_f_top = 20.;

  constexpr double invGeV2_to_pb = 389379300.;


  inline double axial_Z_coupling(double T3, double){
    return T3/(2*sqrt(sw2*cw2));
  }


  inline double vector_Z_coupling(double T3, double e){
    return (T3 - 2*e*sw2)/(2*sqrt(sw2*cw2));
  }

  namespace detail{
    enum coupling{
      axial, vector,
      last_coupling = vector
    };

    //TODO: make constexpr (requires constexpr sqrt)
    template<coupling c>
    double c_e();

    template<>
    inline double c_e<axial>(){
      static const double a_e = axial_Z_coupling(T3_e, e);
      return a_e;
    }

    template<>
    inline double c_e<vector>(){
      static const double v_e = vector_Z_coupling(T3_e, e);
      return v_e;
    }

    //TODO: make constexpr (requires constexpr sqrt)
    template<coupling c>
    double c_nu();

    template<>
    inline double c_nu<axial>(){
      static const double a_nu = axial_Z_coupling(T3_nu, 0);
      return a_nu;
    }

    template<>
    inline double c_nu<vector>(){
      static const double v_nu = vector_Z_coupling(T3_nu, 0);
      return v_nu;
    }
  }

}