Baryon Structure and the Chiral Symmetry of QCD

Abstract

I begin with the key problem of light and strange baryon spectroscopy which suggests a clue for our understanding of underlying dynamics. Then I discuss spontaneous breaking of chiral symmetry in QCD, which implies that at low momenta there must be quasiparticles - constituent quarks with dynamical mass, which should be coupled to other quasiparticles - Goldstone bosons. Hence in the low-energy regime the underlying dynamics in baryons is due to Goldstone boson exchange (GBE) between constituent quarks. Using as a prototype of the microscopical quark-gluon degrees of freedom the instantoninduced ’t Hooft interaction I show why the GBE is so important. When the ’t Hooft interaction is iterated in the qq t-channel it inevitably leads to a pole which corresponds to GBE. I show how the explicitly flavour-dependent shortrange part of the GBE interaction between quarks, perhaps in combination with the vector-meson exchange interaction, solves the key problem of baryon spectroscopy and present spectra obtained in a simple analytical calculation as well as in exact semirelativistic three-body approach.