include/root/TGeoPhysicalConstants.h

0001 /*************************************************************************
0002  * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
0003  * All rights reserved.                                                  *
0004  *                                                                       *
0005  * For the licensing terms see $ROOTSYS/LICENSE.                         *
0006  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
0007  *************************************************************************/
0008
0009 // ----------------------------------------------------------------------
0010 // HEP coherent Physical Constants
0011 // Adapted for ROOT by Marko Petric
0012 //
0013 // This file has been provided by Geant4 (simulation toolkit for HEP).
0014 //
0015 // Below is a non exhaustive list of Physical CONSTANTS,
0016 // computed in the Internal HEP System Of Units.
0017 //
0018 // Most of them are extracted from the Particle Data Book :
0019 //        Phys. Rev. D  volume 50 3-1 (1994) page 1233
0020 //
0021 //
0022 // Author: M.Maire
0023 //
0024 // History:
0025 //
0026 // 23.02.96 Created
0027 // 26.03.96 Added constants for standard conditions of temperature
0028 //          and pressure; also added Gas threshold.
0029 // 29.04.08   use PDG 2006 values
0030 // 03.11.08   use PDG 2008 values
0031 // 02.10.17   addopted constant from CLHEP 2.3.4.3
0032
0033 #ifndef TGEO_PHYSICAL_CONSTANTS_H
0034 #define TGEO_PHYSICAL_CONSTANTS_H
0035
0036 #include "TGeoSystemOfUnits.h"
0037
0038 namespace TGeoUnit {
0039
0040 //
0041 //
0042 //
0043 static constexpr double Avogadro = 6.02214179e+23 / mole;
0044
0045 //
0046 // c   = 299.792458 mm/ns
0047 // c^2 = 898.7404 (mm/ns)^2
0048 //
0049 static constexpr double c_light = 2.99792458e+8 * m / s;
0050 static constexpr double c_squared = c_light * c_light;
0051
0052 //
0053 // h     = 4.13566e-12 MeV*ns
0054 // hbar  = 6.58212e-13 MeV*ns
0055 // hbarc = 197.32705e-12 MeV*mm
0056 //
0057 static constexpr double h_Planck = 6.62606896e-34 * joule * s;
0058 static constexpr double hbar_Planck = h_Planck / twopi;
0059 static constexpr double hbarc = hbar_Planck * c_light;
0060 static constexpr double hbarc_squared = hbarc * hbarc;
0061
0062 //
0063 //
0064 //
0065 static constexpr double electron_charge = -eplus; // see SystemOfUnits.h
0066 static constexpr double e_squared = eplus * eplus;
0067
0068 //
0069 // amu_c2 - atomic equivalent mass unit
0070 //        - AKA, unified atomic mass unit (u)
0071 // amu    - atomic mass unit
0072 //
0073 static constexpr double electron_mass_c2 = 0.510998910 * MeV;
0074 static constexpr double proton_mass_c2 = 938.272013 * MeV;
0075 static constexpr double neutron_mass_c2 = 939.56536 * MeV;
0076 static constexpr double amu_c2 = 931.494028 * MeV;
0077 static constexpr double amu = amu_c2 / c_squared;
0078
0079 //
0080 // permeability of free space mu0    = 2.01334e-16 Mev*(ns*eplus)^2/mm
0081 // permittivity of free space epsil0 = 5.52636e+10 eplus^2/(MeV*mm)
0082 //
0083 static constexpr double mu0 = 4 * pi * 1.e-7 * henry / m;
0084 static constexpr double epsilon0 = 1. / (c_squared * mu0);
0085
0086 //
0087 // electromagnetic coupling = 1.43996e-12 MeV*mm/(eplus^2)
0088 //
0089 static constexpr double elm_coupling = e_squared / (4 * pi * epsilon0);
0090 static constexpr double fine_structure_const = elm_coupling / hbarc;
0091 static constexpr double classic_electr_radius = elm_coupling / electron_mass_c2;
0092 static constexpr double electron_Compton_length = hbarc / electron_mass_c2;
0093 static constexpr double Bohr_radius = electron_Compton_length / fine_structure_const;
0094
0095 static constexpr double alpha_rcl2 = fine_structure_const * classic_electr_radius * classic_electr_radius;
0096
0097 static constexpr double twopi_mc2_rcl2 = twopi * electron_mass_c2 * classic_electr_radius * classic_electr_radius;
0098 //
0099 //
0100 //
0101 static constexpr double k_Boltzmann = 8.617343e-11 * MeV / kelvin;
0102
0103 //
0104 //
0105 //
0106 static constexpr double STP_Temperature = 273.15 * kelvin;
0107 static constexpr double STP_Pressure = 1. * atmosphere;
0108 static constexpr double kGasThreshold = 10. * mg / cm3;
0109
0110 //
0111 //
0112 //
0113 static constexpr double universe_mean_density = 1.e-25 * g / cm3;
0114
0115 } // namespace TGeoUnit
0116
0117 #endif /* TGEO_PHYSICAL_CONSTANTS_H */