cross section

cross section

In nuclear physics, a measure of the probability that a given atomic nucleus will exhibit a specific reaction (absorption, scattering, or nuclear fission) in relation to a particular incident particle. Cross section is expressed in terms of area, and its value is chosen so that, if the bombarding particle hits a circular target of this size perpendicular to its path and centred at the nucleus, the given reaction occurs. If it misses the area, the reaction does not occur. The unit of cross section is the barn, which equals 10⁻²⁴ sq cm. Cross-section values for a given nucleus depend on the energy of the bombarding particle and the kind of reaction and are often different from the actual cross-sectional area of the nucleus.

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cross section

1. Maths a plane surface formed by cutting across a solid, esp perpendicular to its longest axis

2. a section cut off in this way

3. Physics a measure of the probability that a collision process will result in a particular reaction. It is expressed by the effective area that one participant presents as a target for the other

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cross section [′krȯs ‚sek·shən]

(geology)

A diagram or drawing that shows the downward projection of surficial geology along a vertical plane, for example, a portion of a stream bed drawn at right angles to the mean direction of the flow of the stream.

An actual exposure or cut which reveals geological features.

(graphic arts)

A diagram or drawing representing a cut at right angles to an axis.

(mapping)

A horizontal grid system that is laid out on the ground for determining contours, quantities of earthwork, and so on, by means of elevations of the grid points.

(mathematics)

The intersection of ann-dimensional geometric figure in some euclidean space with a lower dimensional hyperplane.

A right inverse for the projection of a fiber bundle.

(physics)

An area characteristic of a collision reaction between atomic or nuclear particles or systems, such that the number of reactions which occur equals the product of the number of target particles or systems and the number of incident particles or systems which would pass through this area if their velocities were perpendicular to it. Also known as collision cross section.