Pentaquarks and Radially Excited Baryons∗

Although chiral soliton model predictions for the mass of the lightest exotic pentaquark, the Θ with zero isospin and unit strangeness, have been around for some time1, the study of pentaquarks as baryon resonances became popular only recently when experiments2,3 indicated their existence. These experiments were stimulated by a chiral soliton model estimate4 suggesting that such exotic baryons might have a width so small4,5 that it could have escaped earlier detection. Then very quickly the novel observations initiated exhaustive studies on the properties of pentaquarks. Comprehensive lists of such studies are, for example, collected in refs.9,10. In chiral soliton models states with baryon quantum numbers are generated from the soliton by canonically quantizing the collective coordinates associated with (would–be) zero modes such as SU(3) flavor rotations. The lowest states are members of the flavor octet (J = 12 + ) and decuplet representations (J = 32 + ). Due to flavor symmetry breaking the physical states acquire admixtures from higher dimensional representations. For the J = 12 + baryons those admixtures originate dominantly from the antidecuplet, 10, and the 27–plet11. The particle content of these representations is depicted in figure 1. They also contain states with quantum numbers that