Chiral-Soliton Predictions for Exotic Baryons

Abstract

We re-analyze the predictions of chiral-soliton models for the masses and decay widths of baryons in the exotic antidecuplet of flavour SU(3). The calculated ranges of the chiral-soliton moment of inertia and the \pi-nucleon scattering \Sigma term are used together with the observed baryon octet and decuplet mass splittings to estimate 1430 MeV < m_{\Theta^+} < 1660 MeV} and 1790 MeV < m_{\Xi^{--}} < 1970 MeV. These are consistent with the masses reported recently, but more precise predictions rely on ambiguous identifications of non-exotic baryon resonances. The overall decay rates of antidecuplet states are sensitive to the singlet axial-current matrix element in the nucleon. Taking this from polarized deep-inelastic scattering experiments, we find a suppression of the total \Theta^+ and \Xi^{--} decay widths that may not be sufficient by itself to reproduce the narrow widths required by experiments. We calculate SU(3) breaking effects due to representation mixing and find that they tend to suppress the \Theta^+ decay width, while enhancing that of the \Xi^{--}. We predict light masses for some exotic 27 baryons, including the I=1, J^P={3/2}^+ \Theta^+ and I=3/2, J^P={3/2}^+ \Xi multiplets, and calculate their decay widths.