Theta++ from QCD sum rule

Abstract

We study the pentaquark $uudd\bar s$ with $J=3/2$ and I=1 ($\Theta^{++}$) in the QCD sum rule approach. We derive the QCD sum rules for positive and negative parity states of the pentaquark. The QCD sum rule predicts that there exists $\Theta^{++}$ with negative parity and its mass is $1.5\sim1.6$ GeV. The negative parity $\Theta^{++}$ can be extremely narrow, since it lies much below the $\Delta K$ threshold and the decay into $KN$ state is strongly suppressed due to the $D$-wave centrifugal barrier. Also, the possibility of the existence of the $\Theta^{++}$ with positive parity is not excluded. Although it nearly degenerates with the negative parity state, it may be broader than the negative parity state.