Baryons, their interactions and the chiral symmetry of QCD

Abstract

An implication of the spontaneous chiral symmetry breaking in QCD is that at low energy and resolution there appear quasiparticles — constituent quarks and Goldstone bosons. Thus, light and strange baryons should be considered as systems of three constitutent quarks with confining interaction and a chiral interaction that is mediated by Goldstone bosons between the constituent quarks. We show how the flavor-spin structure and sign of the short-range part of the Goldstone boson exchange interaction reduces the SU(6) FS symmetry down to SU(3) F × SU(2) S , induces hyperfine splittings and provides correct ordering of the lowest states with positive and negative parity. We present a unified description of light and strange baryon spectra calculated in a semirelativistic framework. It is demonstrated that the same short-range part of Goldstone boson exchange also induces strong short-range repulsion in N N system when the latter is treated as 6 Q system. Thus, all main ingredients of N N interaction are implied by the chiral constituent quark model since the long- and intermediate-range attraction appears in the present framework due to pion and correlated two-pion exchanges between quarks belonging to different nucleons. We also find a very strong short-range repulsion in ΛΛ system with J P = 0 +. It then suggests that the compact H-particle should not exist.