A possible interpretation of $\Lambda$ baryon spectrum with pentaquark components

Abstract

The $\Lambda$ baryon spectrum is studied within the SU(3) flavor symmetry in a constituent quark model. We found that it is rather difficult to accommodate some negative-parity $\Lambda$ resonances as single $q^{2}s$ ($q=u,d$ quarks) states in the conventional three-quark picture. The ground $q^{3}s\bar{q}$ pentaquark mass spectrum is evaluated and a possible interpretation is proposed in the work: the observed $\Lambda (1405)1/2^{-}$, $\Lambda (1670)1/2^{-}$ and $\Lambda (1800)1/2^{-}$ are three-state mixtures of two $p$-wave $q^{2}s$ states and one ground $q^{3}s\bar{q}$ pentaquark state, so are the $\Lambda (1520)3/2^{-}$, $\Lambda (1690)3/2^{-}$ and $\Lambda (2050)3/2^{-}$ resonances.

Comments: 6 pages, 5 tables