Duality, exchange-degeneracy breaking, and exotic states

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 ($\sim \delta$) and larger exchange-degeneracy breaking of the baryon trajectories in the meson-baryon system ($\sim \epsilon$). The $M_4$ states are coupled weakly to external mesons in proportion to the breaking parameter $\delta$. 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 $\epsilon \sim \sqrt{\delta }$, 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.