Barn (unit, $1\mathrm{b}=10^{-28}{\mathrm{m}}^2$)

The barn is a unit of area used in nuclear and particle physics to quantify the cross-sectional area of atomic nuclei and subatomic particles during interactions. It is not a standard unit of measurement in everyday contexts but is specific to the field of physics. One barn is defined as \(10^{-28}\) square meters, or 100 square femtometers (fm²).