Barn (unit)
A barn (symbol b) is a unit of area. Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is used in all fields of high energy physics to express the cross sections of any scattering process, and is best understood as a measure of the probability of interaction between small particles. A barn is defined as 10−28 m2 (100 fm2) and is approximately the cross sectional area of a uranium nucleus. The barn is also the unit of area used in nuclear quadrupole resonance and nuclear magnetic resonance to quantify the interaction of a nucleus with an electric field gradient. While the barn is not an SI unit, it is accepted for use with the SI due to its continued use in particle physics. It is one of the very few units that is accepted for use with SI units, and one of the most recent units to have been established (cf. the knot and the bar, other non-SI units acceptable in limited circumstances).
Two related units are the outhouse (1 μb, or 10−34 m2) and the shed (10−24 b (1 yb), or 10−52 m2), although these are rarely used in practice.
Read more about Barn (unit): Etymology, Commonly Used Prefixed Versions, Conversions, Inverse Femtobarn
Famous quotes containing the word barn:
“There was a deserted log camp here, apparently used the previous winter, with its “hovel” or barn for cattle.... It was a simple and strong fort erected against the cold, and suggested what valiant trencher work had been done there.”
—Henry David Thoreau (1817–1862)