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    Cross section (physics) - Wikipedia

    • When a cross section is specified as the differential limit of a function of some final-state variable, such as particle angle or energy, it is called a differential cross section (see detailed discussion below). 展开

    Overview

    In physics, the cross section is a measure of the probability that a specific process will take place in a collision of two p… 展开

    Collision among gas particles

    In a gas of finite-sized particles there are collisions among particles that depend on their cross-sectional size. The average distance that a particle travels between collisions depends on the density of gas particles. These … 展开

    Attenuation of a beam of particles

    If a beam of particles enters a thin layer of material of thickness dz, the flux Φ of the beam will decrease by dΦ according to
    where σ is the total cross section of all events, including scattering, absorption, or transformation t… 展开

    Differential cross section

    Consider a classical measurement where a single particle is scattered off a single stationary target particle. Conventionally, a spherical coordinate system is used, with the target placed at the origin and the z axis of this coordinat… 展开

    Quantum scattering

    In the time-independent formalism of quantum scattering, the initial wave function (before scattering) is taken to be a plane wave with definite momentum k:
    where z and r are the relative coordinates between the proj… 展开

    Units

    Although the SI unit of total cross sections is m , a smaller unit is usually used in practice.
    In nuclear and particle physics, the conventional unit is the barn b, where 1 b = 10 m = 100 fm . Smaller prefixed units such as … 展开

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