hiukkasjakautuman

hiukkasjakautuma, literally particle decay in Finnish, refers to the spontaneous transformation of an unstable particle into other particles. It is a fundamental process described by quantum field theory and occurs even in the absence of external influences. The decay rate, or lifetime, of a particle is inversely related to its decay constant; unstable particles such as muons, neutrons, and many mesons exhibit characteristic lifetimes ranging from fractions of a second to astronomically long periods for meta‑stable nuclei.

Three main categories of decay are commonly distinguished: beta decay, alpha decay, and gamma decay. Beta decay involves the conversion of a neutron into a proton (or vice versa) with the emission of an electron or positron and a neutrino, governed by the weak nuclear force. Alpha decay ejects a helium nucleus from a heavy nucleus, propelled by quantum tunneling through the nuclear barrier. Gamma decay is the release of excess energy in the form of high‑energy photons, typically following other decay processes to bring the nucleus to a lower energy state.

Theoretical models of particle decay rely on conservation laws—energy, momentum, charge, baryon and lepton numbers—and the symmetries of the Standard Model. Experimental studies of decay rates and branching ratios provide stringent tests of these models and help constrain possible new physics beyond the Standard Model. The observation of rare or forbidden decays, for example, can hint at phenomena such as neutrino mass, CP violation, or the existence of dark sector particles.