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Geant4/externals/clhep/include/CLHEP/Units/PhysicalConstants.h

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  1 // -*- C++ -*-
  2 // ----------------------------------------------------------------------
  3 // HEP coherent Physical Constants
  4 //
  5 // This file has been provided by Geant4 (simulation toolkit for HEP).
  6 //
  7 // The basic units are :
  8 //      millimeter  
  9 //    nanosecond  
 10 //    Mega electron Volt  
 11 //    positon charge 
 12 //    degree Kelvin
 13 //              amount of substance (mole)
 14 //              luminous intensity (candela)
 15 //    radian  
 16 //              steradian 
 17 //
 18 // Below is a non exhaustive list of Physical CONSTANTS,
 19 // computed in the Internal HEP System Of Units.
 20 //
 21 // Most of them are extracted from the Particle Data Book :
 22 //        Phys. Rev. D  volume 50 3-1 (1994) page 1233
 23 // 
 24 //        ...with a meaningful (?) name ...
 25 //
 26 // You can add your own constants.
 27 //
 28 // Author: M.Maire
 29 //
 30 // History:
 31 //
 32 // 23.02.96 Created
 33 // 26.03.96 Added constants for standard conditions of temperature
 34 //          and pressure; also added Gas threshold.
 35 // 29.04.08 Use PDG 2006 values
 36 // 03.11.08 Use PDG 2008 values
 37 // 17.07.20 Use PDG 2019 values
 38 // 06.05.21 Added Bohr_magneton and nuclear_magneton constants
 39 
 40 #ifndef HEP_PHYSICAL_CONSTANTS_H
 41 #define HEP_PHYSICAL_CONSTANTS_H
 42 
 43 #include "CLHEP/Units/SystemOfUnits.h"
 44 
 45 namespace CLHEP {
 46 
 47 //
 48 // 
 49 //
 50 static constexpr double Avogadro = 6.02214076e+23/mole;
 51 
 52 //
 53 // c   = 299.792458 mm/ns
 54 // c^2 = 898.7404 (mm/ns)^2 
 55 //
 56 static constexpr double c_light   = 2.99792458e+8 * m/s;
 57 static constexpr double c_squared = c_light * c_light;
 58 
 59 //
 60 // h     = 4.13566e-12 MeV*ns
 61 // hbar  = 6.58212e-13 MeV*ns
 62 // hbarc = 197.32705e-12 MeV*mm
 63 //
 64 static constexpr double h_Planck      = 6.62607015e-34 * joule*s;
 65 static constexpr double hbar_Planck   = h_Planck/twopi;
 66 static constexpr double hbarc         = hbar_Planck * c_light;
 67 static constexpr double hbarc_squared = hbarc * hbarc;
 68 
 69 //
 70 //
 71 //
 72 static constexpr double electron_charge = - eplus; // see SystemOfUnits.h
 73 static constexpr double e_squared = eplus * eplus;
 74 
 75 //
 76 // amu_c2 - atomic equivalent mass unit
 77 //        - AKA, unified atomic mass unit (u)
 78 // amu    - atomic mass unit
 79 //
 80 static constexpr double electron_mass_c2 = 0.510998910 * MeV;
 81 static constexpr double   proton_mass_c2 = 938.272013 * MeV;
 82 static constexpr double  neutron_mass_c2 = 939.56536 * MeV;
 83 static constexpr double           amu_c2 = 931.494028 * MeV;
 84 static constexpr double              amu = amu_c2/c_squared;
 85 
 86 //
 87 // permeability of free space mu0    = 2.01334e-16 Mev*(ns*eplus)^2/mm
 88 // permittivity of free space epsil0 = 5.52636e+10 eplus^2/(MeV*mm)
 89 //
 90 static constexpr double mu0      = 4*pi*1.e-7 * henry/m;
 91 static constexpr double epsilon0 = 1./(c_squared*mu0);
 92 
 93 //
 94 // electromagnetic coupling = 1.43996e-12 MeV*mm/(eplus^2)
 95 //
 96 static constexpr double elm_coupling           = e_squared/(4*pi*epsilon0);
 97 static constexpr double fine_structure_const   = elm_coupling/hbarc;
 98 static constexpr double classic_electr_radius  = elm_coupling/electron_mass_c2;
 99 static constexpr double electron_Compton_length = hbarc/electron_mass_c2;
100 static constexpr double Bohr_radius = electron_Compton_length/fine_structure_const;
101 
102 static constexpr double alpha_rcl2 = fine_structure_const
103                                    *classic_electr_radius
104                                    *classic_electr_radius;
105 
106 static constexpr double twopi_mc2_rcl2 = twopi*electron_mass_c2
107                                              *classic_electr_radius
108                                              *classic_electr_radius;
109 
110 static constexpr double Bohr_magneton = (eplus*hbarc*c_light)/(2*electron_mass_c2);
111 static constexpr double nuclear_magneton = (eplus*hbarc*c_light)/(2*proton_mass_c2);
112 
113 //
114 //
115 //
116 static constexpr double k_Boltzmann = 8.617333e-11 * MeV/kelvin;
117 
118 //
119 //
120 //
121 static constexpr double STP_Temperature = 273.15*kelvin;
122 static constexpr double STP_Pressure    = 1.*atmosphere;
123 static constexpr double kGasThreshold   = 10.*mg/cm3;
124 
125 //
126 //
127 //
128 static constexpr double universe_mean_density = 1.e-25*g/cm3;
129 
130 }  // namespace CLHEP
131 
132 #endif /* HEP_PHYSICAL_CONSTANTS_H */
133 
134 
135 
136 
137 
138