Units (skhep.units)

Subpackage for the HEP System of Units, (derived) physical units and commonly-used unit prefixes.

The HEP System of Units is the set of basic units originally defined by the CLHEP project.

Module of HEP basic units

In HEP the System of Units consists of the basic units originally defined by the [CLHEP] project:

Quantity Name Unit
Length millimeter mm
Time nanosecond ns
Energy Mega electron Volt MeV
Positron charge eplus  
Temperature kelvin K
Amount of substance mole mol
Luminous intensity candela cd
Plane angle radian rad
Solid angle steradian sr

It is largely based on the international system of units ([SI])

Quantity Name Unit
Length meter m
Time second s
Mass kilogram kg
Electric current ampere A
Temperature kelvin K
Amount of substance mole mol
Luminous intensity candela cd

but augments it with handy definitions, changing the basic length and time units.

This module also defines an extensive set of derived units.

Typical use cases:

>>> # add two quantities with length units and get the result im meters
>>> from skhep import units as u
>>> (1 * u.meter + 5 * u.cm) / u.meter
1.05
>>> from skhep.units import MeV, GeV
>>> massWindow = 100 * MeV    # define a 100 MeV mass window
>>> def energy_resolution():
...    # returns the energy resolution of 100 MeV
...    return 100 * MeV
...
>>> energy_resolution() / GeV # get the energy resolution in GeV
0.1

References

[CLHEP]http://proj-clhep.web.cern.ch/proj-clhep/.
[SI]http://www.physics.nist.gov/cuu/Units/index.html.