Duality, exchange-degeneracy breaking, and exotic states

Abstract

We study the connection between exchange-degeneracy breaking and multiquark states within the framework of a highly constrained dual approach. We show that ${M}_{4}$ (baryonium) states emerge at the daughter trajectory level as a consequence of small exchange-degeneracy breaking in the meson-meson system ($\ensuremath{\sim}\ensuremath{\delta}$) and larger exchange-degeneracy breaking of the baryon trajectories in the meson-baryon system ($\ensuremath{\sim}\ensuremath{\epsilon}$). The ${M}_{4}$ states are coupled weakly to external mesons in proportion to the breaking parameter $\ensuremath{\delta}$. Assuming ${M}_{4}$ couplings to $\overline{B}B$ channels are strong, as determined by duality with normal mesons in the $\overline{B}B$ system, consistency requires $\ensuremath{\epsilon}\ensuremath{\sim}\sqrt{\ensuremath{\delta}}$, thereby relating the larger breaking of baryon trajectories to the violation of the Okubo-Zweig-Iizuka-type rule for ${M}_{4}$. It is shown that exotic baryon states, ${B}_{5}$, also emerge from this scheme at the daughter level and that dibaryons will appear at the second daughter level.