Lambda(1405) as a multiquark state

Abstract

In the QCD sum rule approach we predict the $\Lambda$ (1405) mass by choosing the $\pi^0\Sigma^0$ multiquark interpolating field. It is found that the mass is about 1.419 GeV from $\Pi_1 (q^2)$ sum rule which is more reliable than $\Pi_q (q^2)$ sum rule, where $\Pi_q (q^2)$ and $\Pi_1 (q^2)$ are two invariant functions of the correlator $\Pi (q^2)$. We also present the sum rules for the $K^+ p$ and the $\pi^+\Sigma^+$ multiquark states, and compare to those for the $\pi^0\Sigma^0$ multiquark state. The mass of the $\Lambda$ (1600) can be also reproduced in our approach.