Effects of instanton induced interactions on pentaquarks

Abstract

Roles of instanton induced interactions (III) in the masses of pentaquark baryons, ${\ensuremath{\Theta}}^{+}$ ($J=1/2$ and $3/2$) and ${\ensuremath{\Xi}}^{--}$, and a dibaryon, $H$, are discussed using the MIT bag model. It is shown that the two-body terms in III give a strong attraction mainly due to the increase of the number of flavor antisymmetric quark pairs in multiquark systems. In contrast, the three-body $u$-$d$-$s$ interaction is repulsive. It is found that III lowers the mass of negative-parity ${\ensuremath{\Theta}}^{+}$ as much as 100 MeV from the mass predicted by the bag model without III. We also consider possible quark model configurations for positive-parity ${\ensuremath{\Theta}}^{+}$ under III.