Hyperon

As hyperons baryons are referred to, the at least one strange quark (s- quark ), but no heavy quark (ie charm or bottom quark ) as the valence quark. Hyperons were first detected in the 1950s. They are unstable and unlike nucleons not involved in the establishment of normal matter, but belong to the Strange particles. Atomic nuclei that contain hyperons, hot hypernuclei.

Nomenclature and properties

The nomenclature of the hyperons depends on their number of s- quarks, ie according to their strangeness:

Hyperon decay mostly under the influence of the weak nuclear force. In this case, a mid-heavy s- quark into a light quark (u or d) is converted, as evidenced by the exchange of a W - mediated or a Z0 boson. These bosons couple turn mostly to quarks, eg pions arise ( hadronic decay), but may also pass into leptons ( semileptonischer decay). Since some hyperon decay parity- violating (eg Λ → pπ - ), they played an important role in the development of a theory for the weak nuclear force.

Conceptual history

The term hyperon was before the discovery of quarks. A first definition was: A hyperon is a particle, which is heavier than the neutron, but lighter than the deuteron. With the introduction of quarks as fundamental particles, the definition was amended in baryons containing s- quarks. With the discovery of heavy quarks charm and bottom and this definition was inaccurate, but not further specified. Instead, a classification scheme for baryons was designed. The name hyperon is still being widely used as a generic term in the above definition.