Quark Cluster Model of Baryon-Baryon Interaction

Abstract

The quark cluster model of the baryon-baryon interaction is reviewed. The emphasis is on the foundation of the approach and the main features of the model. The origins of the short-range repulsion in the nuclear force and other baryonic interactions are discussed. The origin of the nuclear force is a central problem of nuclear physics. It has a long history since Yukawa 1) proposed the static one-pion exchange potential (OPEP) of the range of the pion Compton wave length. The discovery of the pion boosted both the experimental and theoretical investigation of the nuclear force. It was realized in the early stage that the short range part of the nuclear force requires further ingredients, including the two- and multi-pion exchange interactions. In order to study the shorter-range part, Taketani proposed to consider three regions of the nuclear force separately. 2) (I) The long-range part (R ≥ 2 fm) is described by OPEP. (II) The medium-range part (1 ≤ R ≤ 2 fm) is attributed to nonstatic part of the pion exchange, multipion exchanges and heavy meson exchanges. Finally, (III) the shortrange part (R ≤ 1 fm) is left for phenomenology as it is most “complicated”. The OPEP was firmly established since then and the region (II) was studied in various approaches that treat nonstatic contribution and heavy mesons. It is believed to give a strong attraction due mostly to exchange of two pions correlated in the S-wave, which is often represented by the exchange of a scalar sigma meson. It turned out that this strong attraction of the second region is crucial for the nuclear binding. The shortest range region (III) was found to have a strong repulsion as suggested from the medium-energy nucleon-nucleon ( NN ) scattering data. Thus the nuclear binding is on the balance between the attraction in the regions (I) and (II) and the repulsion in (III). Meanwhile, many phenomenological models have been constructed. Main source of information is the NN scattering observables as well as properties of the deuteron. The proposed models include the Hamada-Johnston potential, 3) the Reid soft core potential, 4) the Tamagaki potential, 5) all of which can explain the low energy observables fairly well. The real development in the study of region (II) was achieved in 1970’s resulting in two popular models of nuclear force, Bonn 6) and Paris 7) po