Models of Confinement

Abstract

In all the history of science it was assumed that properties of the fundamental particles must be rather simple and all complications of nature are a consequence of the collective interaction (many body problem). In the fifties the consideration of the proton, neutron and Λ hyperon as fundamental particles interacting via pion or kaon exchanges became a popular model [1]. But already in the sixties, after the discovery of other hyperons, Gell-Mann [2] and Zweig [3] realized that hadrons can be classified on the basis of a triplet of hypothetical particles (called quarks) carrying fractional electric charges. The quark model not only explained the existing spectra of baryons and mesons but also predicted a new particle: the Ω hyperon, which was later discovered successfully. Many experiments were designed to find quarks, both using accelerators and in cosmic rays; but all failed to detect such particles. Very soon it was realized that, instead of being simple ”bricks of nature”, it is astonishing that these fundamental constitutents cannot be observed directly in experiments, but are confined inside mesons and baryons.