Cross section (physics)
Also known as: reaction cross-section · cross-section of interaction · cross-section
- 1The cross section is denoted by the symbol σ (sigma).
- 2It is measured in units of area, such as square meters or barns.
- 3The Rutherford cross section measures the probability of alpha particle deflection.
- 4It acts as a parameter for describing the likelihood of a stochastic process.
- 5It represents the effective target size for a particle collision.
In physics, the cross section is a measure related to the probability that a specific process will take place in a collision of two particles.
Connections1
energy-dependent interaction probability
The probability of a neutron interacting with a nucleus is highly dependent on its kinetic energy, making neutron temperature a key variable in calculating reaction rates.
In physics, the cross section is a quantitative measure representing the probability that a specific process will occur during a collision between two particles. It is typically denoted by the Greek letter sigma (σ) and possesses the physical dimension of area. While it can be intuitively visualized as the effective size of a target, it is more precisely defined as a parameter of a stochastic process.
Figure 1. In a gas of particles of individual diameter 2 r, the cross section σ, for collisions is related to the particle number density n, and mean free path between collisions λ.Wikimedia Commons: File:CrossSectionFig1.svg A classic example is the Rutherford cross section, which calculates the probability of an alpha particle being deflected by a specific angle when interacting with an atomic nucleus. Because cross sections represent area, they are commonly measured in square meters or the specialized unit known as the barn.