Parity of ${\Theta }^{+}$(1540) from QCD sum rules

Abstract

The QCD sum rule for the pentaquark ${\Theta }^{+}$, first analyzed by Sugiyama, Doi and Oka, is reanalyzed with a phenomenological side that explicitly includes the contribution from the two-particle reducible kaon-nucleon intermediate state. The magnitude for the overlap of the ${\Theta }^{+}$ interpolating current with the kaon-nucleon state is obtained by using soft-kaon theorem and a separate sum rule for the ground state nucleon with the pentaquark nucleon interpolating current. It is found that the K-N intermediate state constitutes only 10% of the sum rule so that the original claim that the parity of ${\Theta }^{+}$ is negative remains valid.

Comments: slightly revised, version to appear in PLB