PhysicalConstants.h

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// -*- C++ -*-
// ----------------------------------------------------------------------
// HEP coherent Physical Constants
//
// This file has been provided by Geant4 (simulation toolkit for HEP).
//
// The basic units are :
//          millimeter
//      nanosecond
//      Mega electron Volt
//      positon charge
//      degree Kelvin
//              amount of substance (mole)
//              luminous intensity (candela)
//      radian
//              steradian
//
// Below is a non exhaustive list of Physical CONSTANTS,
// computed in the Internal HEP System Of Units.
//
// Most of them are extracted from the Particle Data Book :
//        Phys. Rev. D  volume 50 3-1 (1994) page 1233
//
//        ...with a meaningful (?) name ...
//
// You can add your own constants.
//
// Author: M.Maire
//
// History:
//
// 23.02.96 Created
// 26.03.96 Added constants for standard conditions of temperature
//          and pressure; also added Gas threshold.
// 28.04.06 Imported from CLHEP into GaudiKernel -- HD

#ifndef GAUDI_PHYSICAL_CONSTANTS_H
#define GAUDI_PHYSICAL_CONSTANTS_H

#include "GaudiKernel/SystemOfUnits.h"

namespace Gaudi {
  namespace Units {

    constexpr double     pi  = 3.14159265358979323846;
    constexpr double  twopi  = 2*pi;
    constexpr double halfpi  = pi/2;
    constexpr double     pi2 = pi*pi;

    constexpr double Avogadro = 6.0221367e+23/mole;

    //
    // c   = 299.792458 mm/ns
    // c^2 = 898.7404 (mm/ns)^2
    //
    constexpr double c_light   = 2.99792458e+8 * m/s;
    constexpr 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
    //
    constexpr double h_Planck      = 6.6260755e-34 * joule*s;
    constexpr double hbar_Planck   = h_Planck/twopi;
    constexpr double hbarc         = hbar_Planck * c_light;
    constexpr double hbarc_squared = hbarc * hbarc;

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

    //
    // amu_c2 - atomic equivalent mass unit
    // amu    - atomic mass unit
    //
    constexpr double electron_mass_c2 = 0.51099906 * MeV;
    constexpr double   proton_mass_c2 = 938.27231 * MeV;
    constexpr double  neutron_mass_c2 = 939.56563 * MeV;
    constexpr double           amu_c2 = 931.49432 * MeV;
    constexpr 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)
    //
    constexpr double mu0      = 4*pi*1.e-7 * henry/m;
    constexpr double epsilon0 = 1./(c_squared*mu0);

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

    constexpr double alpha_rcl2 = fine_structure_const
      *classic_electr_radius
      *classic_electr_radius;

    constexpr double twopi_mc2_rcl2 = twopi*electron_mass_c2
      *classic_electr_radius
      *classic_electr_radius;

    constexpr double k_Boltzmann = 8.617385e-11 * MeV/kelvin;

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

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

  }  // namespace Units
} // namespace Gaudi


#endif /* GAUDI_PHYSICAL_CONSTANTS_H */