Conservation of Energy in Annihilation and Pair Production

This page delves deeper into the processes of annihilation and pair production, focusing on the conservation of energy and the practical applications of these phenomena.

The conservation of energy principle is emphasized in the context of particle-antiparticle interactions:

Quote: "Energy cannot be created nor destroyed."

In annihilation, the total energy of the particle and antiparticle is converted into electromagnetic energy in the form of gamma-ray photons. The minimum energy of each photon produced is equal to the rest energy of the particle or antiparticle.

Example: In electron-positron annihilation (β⁻ + β⁺ → 2γ), two gamma-ray photons are produced, each with an energy of at least 0.511 MeV (the rest energy of an electron or positron).

The page explains pair production in detail, noting that it only occurs when there is sufficient energy to produce the masses of the particles. It emphasizes that pair production must always produce a particle and its corresponding antiparticle due to conservation laws.

Highlight: Pair production conserves various quantities including energy, momentum, baryon number, lepton number, charge, and strangeness.

The practical application of annihilation is illustrated through the example of PET (Positron Emission Tomography) scans:

Example: PET scans use positron-emitting isotopes in the blood. The annihilation of positrons with electrons produces gamma rays that are detected to form medical images.

The page concludes by reiterating the conservation of energy in these processes and provides equations for calculating the minimum energy required for pair production and the energy released in annihilation. This information is crucial for understanding the fundamental principles governing the behavior of matter and antimatter in the universe.