Barn (unit)

Barn
Unit systemparticle physics
Unit ofarea
Symbolb
Named afterthe broad side of a barn
Conversions
1 b in ...... is equal to ...
   SI base units   10−28 m2
   equivalent   100 fm2

A barn (symbol: b) is a metric unit of area equal to 10−28 m2 (100 fm2). 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 While the barn never was an SI unit, the SI standards body acknowledged it in the 8th SI Brochure (superseded in 2019) due to its use in particle physics.[1]

  1. ^ "Non-SI units accepted for use with the SI, and units based on fundamental constants". SI brochure (8th edition). BIPM. May 2006. Retrieved 2009-03-13.

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