Constants.hh

#ifndef RIVET_MATH_CONSTANTS
#define RIVET_MATH_CONSTANTS

#include "Rivet/Math/MathHeader.hh"
#include "Rivet/Math/Units.hh"

namespace Rivet {

  //
  //
  //
  static const double     pi  = 3.14159265358979323846;
  static const double  twopi  = 2*pi;
  static const double halfpi  = pi/2;
  static const double     pi2 = pi*pi;

  //
  //
  //
  static const double Avogadro = 6.0221367e+23/mole;

  //
  // c   = 299.792458 mm/ns
  // c^2 = 898.7404 (mm/ns)^2
  //
  static const double c_light   = 2.99792458e+8 * m/s;
  static const double c_squared = c_light * c_light;

  //
  // h     = 4.13566e-12 MeV*ns
  // hbar  = 6.58212e-13 MeV*ns
  // hbarc = 197.32705e-12 MeV*mm
  //
  static const double h_Planck      = 6.6260755e-34 * joule*s;
  static const double hbar_Planck   = h_Planck/twopi;
  static const double hbarc         = hbar_Planck * c_light;
  static const double hbarc_squared = hbarc * hbarc;

  //
  //
  //
  static const double electron_charge = - eplus; // see SystemOfUnits.h
  static const double e_squared = eplus * eplus;

  //
  // amu_c2 - atomic equivalent mass unit
  // amu    - atomic mass unit
  //
  static const double electron_mass_c2 = 0.51099906 * MeV;
  static const double   proton_mass_c2 = 938.27231 * MeV;
  static const double  neutron_mass_c2 = 939.56563 * MeV;
  static const double           amu_c2 = 931.49432 * MeV;
  static const double              amu = amu_c2/c_squared;

  //
  // permeability of free space mu0    = 2.01334e-16 Mev*(ns*eplus)^2/mm
  // permittivity of free space epsil0 = 5.52636e+10 eplus^2/(MeV*mm)
  //
  static const double mu0      = 4*pi*1.e-7 * henry/m;
  static const double epsilon0 = 1./(c_squared*mu0);

  //
  // electromagnetic coupling = 1.43996e-12 MeV*mm/(eplus^2)
  //
  static const double elm_coupling           = e_squared/(4*pi*epsilon0);
  static const double fine_structure_const   = elm_coupling/hbarc;
  static const double classic_electr_radius  = elm_coupling/electron_mass_c2;
  static const double electron_Compton_length = hbarc/electron_mass_c2;
  static const double Bohr_radius = electron_Compton_length/fine_structure_const;

  static const double alpha_rcl2 = fine_structure_const
                                     *classic_electr_radius
                                     *classic_electr_radius;

  static const double twopi_mc2_rcl2 = twopi*electron_mass_c2
                                               *classic_electr_radius
                                               *classic_electr_radius;
  //
  //
  //
  static const double k_Boltzmann = 8.617385e-11 * MeV/kelvin;

  //
  //
  //
  static const double STP_Temperature = 273.15*kelvin;
  static const double STP_Pressure    = 1.*atmosphere;
  static const double kGasThreshold   = 10.*mg/cm3;

  //
  //
  //
  static const double universe_mean_density = 1.e-25*g/cm3;

}

#endif