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# PhysicalConstants.py

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    00001 # File: AthenaCommon/share/PhysicalConstants.py
    00002 # Author: Wim Lavrijsen (LBNL, WLavrijsen@lbl.gov)
    00003 # Created: 01/21/04
    00004 # Last: 10/15/04
    00005
    00006 # This script is a direct adaptation of CLHEP/Units/PhysicalConstants.h
    00007 # and the following is the originial CLHEP comment:
    00008 #
    00009 # -----
    00010 # This file has been provided by Geant4 (simulation toolkit for HEP).
    00011 #
    00012 # The basic units are :
    00013 #               millimeter
    00014 #               nanosecond
    00015 #               Mega electron Volt
    00016 #               positon charge
    00017 #               degree Kelvin
    00018 #               amount of substance (mole)
    00019 #               luminous intensity (candela)
    00020 #               radian
    00021 #               steradian
    00022 #
    00023 # Below is a non exhaustive list of Physical CONSTANTS,
    00024 # computed in the Internal HEP System Of Units.
    00025 #
    00026 # Most of them are extracted from the Particle Data Book :
    00027 #        Phys. Rev. D  volume 50 3-1 (1994) page 1233
    00028 #
    00029 #        ...with a meaningful (?) name ...
    00030 #
    00031 # You can add your own constants.
    00032 #
    00033 # Author: M.Maire
    00034 #
    00035 # History:
    00036 #
    00037 # 23.02.96 Created
    00038 # 26.03.96 Added constants for standard conditions of temperature
    00039 #          and pressure; also added Gas threshold.
    00040 # -----
    00041
    00042 from GaudiKernel.SystemOfUnits import *
    00043
    00044 #
    00045 #
    00046 #
    00047 pi     = 3.14159265358979323846
    00048 twopi  = 2*pi
    00049 halfpi = pi/2
    00050 pi2    = pi*pi
    00051
    00052 #
    00053 #
    00054 #
    00055 Avogadro = 6.0221367e+23/mole
    00056
    00057 #
    00058 # c   = 299.792458 mm/ns
    00059 # c^2 = 898.7404 (mm/ns)^2
    00060 #
    00061 c_light   = 2.99792458e+8 * m/s
    00062 c_squared = c_light * c_light
    00063
    00064 #
    00065 # h     = 4.13566e-12 MeV*ns
    00066 # hbar  = 6.58212e-13 MeV*ns
    00067 # hbarc = 197.32705e-12 MeV*mm
    00068 #
    00069 h_Planck      = 6.6260755e-34 * joule*s
    00070 hbar_Planck   = h_Planck/twopi
    00071 hbarc         = hbar_Planck * c_light
    00072 hbarc_squared = hbarc * hbarc
    00073
    00074 #
    00075 #
    00076 #
    00077 electron_charge = - eplus # see SystemOfUnits.h
    00078 e_squared = eplus * eplus
    00079
    00080 #
    00081 # amu_c2 - atomic equivalent mass unit
    00082 # amu    - atomic mass unit
    00083 #
    00084 electron_mass_c2 = 0.51099906 * MeV
    00085 proton_mass_c2   = 938.27231 * MeV
    00086 neutron_mass_c2  = 939.56563 * MeV
    00087 amu_c2           = 931.49432 * MeV
    00088 amu              = amu_c2/c_squared
    00089
    00090 #
    00091 # permeability of free space mu0    = 2.01334e-16 Mev*(ns*eplus)^2/mm
    00092 # permittivity of free space epsil0 = 5.52636e+10 eplus^2/(MeV*mm)
    00093 #
    00094 mu0      = 4*pi*1.e-7 * henry/m
    00095 epsilon0 = 1./(c_squared*mu0)
    00096
    00097 #
    00098 # electromagnetic coupling = 1.43996e-12 MeV*mm/(eplus^2)
    00099 #
    00100 elm_coupling           = e_squared/(4*pi*epsilon0)
    00101 fine_structure_const   = elm_coupling/hbarc
    00102 classic_electr_radius  = elm_coupling/electron_mass_c2
    00103 electron_Compton_length = hbarc/electron_mass_c2
    00104 Bohr_radius = electron_Compton_length/fine_structure_const
    00105
    00106 alpha_rcl2 = fine_structure_const*classic_electr_radius*classic_electr_radius
    00107
    00108 twopi_mc2_rcl2 = twopi*electron_mass_c2*classic_electr_radius*classic_electr_radius
    00109 #
    00110 #
    00111 #
    00112 k_Boltzmann = 8.617385e-11 * MeV/kelvin
    00113
    00114 #
    00115 #
    00116 #
    00117 STP_Temperature = 273.15*kelvin
    00118 STP_Pressure    = 1.*atmosphere
    00119 kGasThreshold   = 10.*mg/cm3
    00120
    00121 #
    00122 #
    00123 #
    00124 universe_mean_density = 1.e-25*g/cm3