Key facts
- Unit of
- area
- Symbol
- b
- Named after
- the broad side of a barn
- Si base units
- 10 m
- Square fm
- 100 fm
via Wikipedia infobox
Wikidata facts
Show 3 more facts
- conversion to SI unit
- 0.0000000000000000000000000001
- unit symbol
- бн
- Wikidata SPARQL query equivalent
- wd:Q209351 p:P2370/psn:P2370 [wikibase:quantityAmount ?source; wikibase:quantityUnit ?base]. ?item p:P2370/psn:P2370 [wikibase:quantityAmount ?target; wikibase:quantityUnit ?base]. BIND(?source / ?target as ?value)
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Article
A barn (symbol: b) is a non-SI metric unit of area equal to 10 m (100 fm). This corresponds to the area of a square with side 10 m (10 fm) or a circle of diameter approximately 1.128×10 m (11.28 fm).
Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is also 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 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 While the barn never was an SI unit, the SI standards body acknowledged it in the 8th SI Brochure (superseded in 2019) due to its use in particle physics.