S=+1 pentaquarks in QCD sum rules

The QCD sum rule technique is employed to investigate pentaquark states with strangeness $S = +1$ and $IJ^{\pi} = 0\frac{1}{2}^{\pm},1\frac{1}{2}^{\pm},0\frac{3}{2}^ {\pm},1\frac{3}{2}^{\pm}$. Throughout the calculation, we emphasize the importance of the establishment of a valid Borel window, which corresponds to a region of the Borel mass, where the operator product expansion (OPE) converges and the presumed ground state pole dominates the sum rules. Such a Borel window is achieved by constructing the sum rules from the differenece of two carefully chosen independent correlators and by calculating the OPE up to dimension 14. As a result, we conclude that the state with qauntum numbers $0\frac{3}{2}^{+}$ state appears to be the most probable candidate for the experimantally observed $\Theta^ {+}(1540)$, while we also obtain states with $0\frac{1}{2}^{-},1\frac{1}{2}^{-},1\frac{3}{2}^{+}$ at somewhat higher mass regions. We furthermore discuss the contribution of the $KN$ scattering states to the sum rules, and the possible influence of these states on our results.