Baryons as solitons in Effective Chiral Quark - Meson Theory

Abstract

The Nambu - Jona-Lasinio model in its SU(2) and SU(3) versions with scalar and pseudoscalar coupling are applied to baryons. The parameters of the model are fixed in the meson sector. The baryons arise as a soliton of three valence quarks coupled to the Dirac sea (quark-antiquarks pairs). Within the SU(2) version the nucleon static properties as well as some form factors, namely, the electric and axial ones are described quite successfully. The nucleon-delta splitting comes out reasonable. In medium the nucleonic soliton gets less stable -- the mass is reduced whereas the radius increases. At some critical medium density there is a clear delocalization of the soliton: The nucleon does not exsist anymore as a soliton. In SU(3) version the strangness carrying baryons are described as SU(3)-rotational excitations of the SU(2)-soliton embedded in the SU(3)-sector. The mass splittings between the octet and decuplet as well as within the multiplets are peproduced not only in a correct oder but also in a good agreement with the experimantal values.