Pentaquark decay is suppressed by chirality conservation

It is shown, that if the pentaquark $\Theta^+ = uudd\bar{s}$ baryon can be represented by the local quark current $\eta_{\Theta}$, its decay $\Theta^+ \to n K^+ (p K^0)$ is forbidden in the limit of chirality conservation. The $\Theta^+$decay width $\Gamma$ is proportional to $\alpha^2_s \langle 0 \vert \bar{q} q \vert 0 \rangle^2$, where $\langle 0 \vert \bar{q} q \vert 0 \rangle$, $q = u,d,s$ is quark condensate, and, therefore, is strongly suppressed. The polarization operator of the pentaquark current is calculated using the operator product expansion. The $\Theta^+$ mass found by the QCD sum rules method is in a reasonable agreement with experiment.