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PhysicalConstants.h
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1 // -*- C++ -*-
2 // $Id: PhysicalConstants.h,v 1.1 2006/05/02 13:03:03 hmd Exp $
3 // ----------------------------------------------------------------------
4 // HEP coherent Physical Constants
5 //
6 // This file has been provided by Geant4 (simulation toolkit for HEP).
7 //
8 // The basic units are :
9 // millimeter
10 // nanosecond
11 // Mega electron Volt
12 // positon charge
13 // degree Kelvin
14 // amount of substance (mole)
15 // luminous intensity (candela)
16 // radian
17 // steradian
18 //
19 // Below is a non exhaustive list of Physical CONSTANTS,
20 // computed in the Internal HEP System Of Units.
21 //
22 // Most of them are extracted from the Particle Data Book :
23 // Phys. Rev. D volume 50 3-1 (1994) page 1233
24 //
25 // ...with a meaningful (?) name ...
26 //
27 // You can add your own constants.
28 //
29 // Author: M.Maire
30 //
31 // History:
32 //
33 // 23.02.96 Created
34 // 26.03.96 Added constants for standard conditions of temperature
35 // and pressure; also added Gas threshold.
36 // 28.04.06 Imported from CLHEP into GaudiKernel -- HD
37
38 #ifndef GAUDI_PHYSICAL_CONSTANTS_H
39 #define GAUDI_PHYSICAL_CONSTANTS_H
40
41 #include "GaudiKernel/SystemOfUnits.h"
42
43 namespace Gaudi {
44 namespace Units {
45
46 static const double pi = 3.14159265358979323846;
47 static const double twopi = 2*pi;
48 static const double halfpi = pi/2;
49 static const double pi2 = pi*pi;
50
51 static const double Avogadro = 6.0221367e+23/mole;
52
53 //
54 // c = 299.792458 mm/ns
55 // c^2 = 898.7404 (mm/ns)^2
56 //
57 static const double c_light = 2.99792458e+8 * m/s;
58 static const double c_squared = c_light * c_light;
59
60 //
61 // h = 4.13566e-12 MeV*ns
62 // hbar = 6.58212e-13 MeV*ns
63 // hbarc = 197.32705e-12 MeV*mm
64 //
65 static const double h_Planck = 6.6260755e-34 * joule*s;
66 static const double hbar_Planck = h_Planck/twopi;
67 static const double hbarc = hbar_Planck * c_light;
68 static const double hbarc_squared = hbarc * hbarc;
69
70 static const double electron_charge = - eplus; // see SystemOfUnits.h
71 static const double e_squared = eplus * eplus;
72
73 //
74 // amu_c2 - atomic equivalent mass unit
75 // amu - atomic mass unit
76 //
77 static const double electron_mass_c2 = 0.51099906 * MeV;
78 static const double proton_mass_c2 = 938.27231 * MeV;
79 static const double neutron_mass_c2 = 939.56563 * MeV;
80 static const double amu_c2 = 931.49432 * MeV;
81 static const double amu = amu_c2/c_squared;
82
83 //
84 // permeability of free space mu0 = 2.01334e-16 Mev*(ns*eplus)^2/mm
85 // permittivity of free space epsil0 = 5.52636e+10 eplus^2/(MeV*mm)
86 //
87 static const double mu0 = 4*pi*1.e-7 * henry/m;
88 static const double epsilon0 = 1./(c_squared*mu0);
89
90 //
91 // electromagnetic coupling = 1.43996e-12 MeV*mm/(eplus^2)
92 //
93 static const double elm_coupling = e_squared/(4*pi*epsilon0);
94 static const double fine_structure_const = elm_coupling/hbarc;
95 static const double classic_electr_radius = elm_coupling/electron_mass_c2;
96 static const double electron_Compton_length = hbarc/electron_mass_c2;
97 static const double Bohr_radius = electron_Compton_length/fine_structure_const;
98
99 static const double alpha_rcl2 = fine_structure_const
100 *classic_electr_radius
101 *classic_electr_radius;
102
103 static const double twopi_mc2_rcl2 = twopi*electron_mass_c2
104 *classic_electr_radius
105 *classic_electr_radius;
106
107 static const double k_Boltzmann = 8.617385e-11 * MeV/kelvin;
108
109 static const double STP_Temperature = 273.15*kelvin;
110 static const double STP_Pressure = 1.*atmosphere;
111 static const double kGasThreshold = 10.*mg/cm3;
112
113 static const double universe_mean_density = 1.e-25*g/cm3;
114
115 } // namespace Units
116 } // namespace Gaudi
117
118
119 #endif /* GAUDI_PHYSICAL_CONSTANTS_H */
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