Instanton induced quark dynamics and the pentaquark

Abstract

We analyze the existence of the exotic ${\Theta }^{+}$ from the perspective of instanton induced quark dynamics. The 't Hooft interaction gives strong attraction in specific channels of the triquark $ud\bar{s}$ and diquark $ud$ configurations. In particular it leads to a light $ud\bar{s}$ triquark cluster, with the mass around $750\mathrm{MeV}$, in the I=0, $S=1/2$ and color 3 configuration, and a light $ud$-diquark configuration, with mass $440\mathrm{MeV}$, in the I=0, S=0 and color {$\bar{3}$} configuration. If we consider the pentaquark as a bound state of such triquark and diquark configurations in a relative L=1 state we obtain good agreement with the data. The small width of ${\Theta }^{+}$ has a natural explanation in this model.

Comments: 14 pages, 2 figures; added references, corrected typos