Annihilaatioreaktiona

Annihilaatioreaktiona refers to the annihilation reaction, the process in which a particle collides with its antiparticle and both are destroyed, converting their rest mass into energy and other particles. In the standard model, annihilation is described by quantum field theory and is constrained by conservation laws for energy, momentum, electric charge, and, where applicable, lepton or baryon numbers.

The simplest and best known example is electron–positron annihilation. At low to moderate energies this interaction predominantly yields photons, most commonly two gamma rays with equal energy, whose total energy equals the sum of the rest masses and kinetic energies of the initial particles. At higher energies or with different particle–antiparticle pairs, a variety of final states can appear, including mesons, muons, neutrinos, or other particles produced by available energy and interaction channels.

In practice, annihilation processes are studied in particle accelerators and astrophysical observations. They provide a clean source of photons and other particles that help determine properties of fundamental interactions. A notable application is positron emission tomography (PET) imaging in medicine, where electron–positron annihilation produces detectable gamma photons that form diagnostic images. In cosmology and astrophysics, annihilation events influence the evolution of the early universe and the gamma-ray backgrounds observed today.