Contribution of Instanton Induced Interaction for Penta-quarks in MIT   Bag Model
  Roles of instanton induced interactions (III) in the masses of pentaquark baryons, Theta^+ (J=1/2 and 3/2) and 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 pairs in multi-quark systems. In contrast, the three-body $u$-$d$-$s$ interaction is repulsive. It is found that III lowers the mass of negative-parity Theta^+ as much as 100 MeV from the mass predicted by the bag model without III. 
Tetsuya Shinozaki, Makoto Oka and Sachiko Takeuchi