PhysicalConstants.py

Go to the documentation of this file.

# File: AthenaCommon/share/PhysicalConstants.py
# Author: Wim Lavrijsen (LBNL, WLavrijsen@lbl.gov)
# Created: 01/21/04
# Last: 10/15/04

# This script is a direct adaptation of CLHEP/Units/PhysicalConstants.h
# and the following is the originial CLHEP comment:
#
# -----
# 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.
# -----

from GaudiKernel.SystemOfUnits import *

#
#
#
pi     = 3.14159265358979323846
twopi  = 2*pi
halfpi = pi/2
pi2    = pi*pi

#
# 
#
Avogadro = 6.0221367e+23/mole

#
# c   = 299.792458 mm/ns
# c^2 = 898.7404 (mm/ns)^2 
#
c_light   = 2.99792458e+8 * m/s
c_squared = c_light * c_light

#
# h     = 4.13566e-12 MeV*ns
# hbar  = 6.58212e-13 MeV*ns
# hbarc = 197.32705e-12 MeV*mm
#
h_Planck      = 6.6260755e-34 * joule*s
hbar_Planck   = h_Planck/twopi
hbarc         = hbar_Planck * c_light
hbarc_squared = hbarc * hbarc

#
#
#
electron_charge = - eplus # see SystemOfUnits.h
e_squared = eplus * eplus

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

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

alpha_rcl2 = fine_structure_const*classic_electr_radius*classic_electr_radius

twopi_mc2_rcl2 = twopi*electron_mass_c2*classic_electr_radius*classic_electr_radius
#
#
#
k_Boltzmann = 8.617385e-11 * MeV/kelvin

#
#
#
STP_Temperature = 273.15*kelvin
STP_Pressure    = 1.*atmosphere
kGasThreshold   = 10.*mg/cm3

#
#
#
universe_mean_density = 1.e-25*g/cm3