alphaem.h

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//
// ePDF
//
 
#pragma once
 
#include <yaml-cpp/yaml.h>
#include <vector>
#include <string>
#include <math.h>
 
namespace ePDF
{
  class AlphaQED
  {
  public:
    AlphaQED(YAML::Node const& config);
 
    AlphaQED(std::string const& method, std::string const& po,
             double const& aref, double const& Qref,
             int const& NL, int const& NF);
 
    double Evolve(double const& Q) const;
 
    double operator()(double const& Q) const { return 4 * M_PI * Evolve(Q); };
 
    double EvolveAnalytic(double const& Q) const;
 
    double EvolveNumerical(double const& Q) const;
 
    double Beta0QED() const;
    double Beta1QED() const;
 
    bool IsFixed() const;
 
    double FBetaQED(double const& alpha) const;
 
  private:
    std::string const m_method;       
    std::string const m_po;           
    double      const m_aref;         
    double      const m_Qref;         
    int         const m_NL;           
    int         const m_NF;           
 
    int    const m_nstep = 10;
    double const m_sxth  = 0.166666666666666;
 
    std::vector<double> m_sumch2 = { 0.0, 1.0/9.0, 5.0/9.0, 2.0/3.0,
                                     10.0/9.0, 11.0/9.0, 5.0/3.0
                                   };
 
    std::vector<double> m_sumch4 = { 0.0, 1.0/81.0, 17.0/81.0, 18.0/81.0,
                                     34.0/81.0, 35.0/81.0, 51.0/81.0
                                   };
  };
}