Low-energyK−p→Ληreaction and the negative parityΛresonances

Abstract

The reaction $K^-p\rightarrow\Lambda\eta$ at low energies is studied with a chiral quark model approach. Good descriptions of the existing experimental data are obtained. It is found that $\Lambda(1670)$ dominates the reaction around threshold. Furthermore, $u$- and $t$-channel backgrounds play crucial roles in this reaction as well. The contributions from the $D$-wave state $\Lambda(1690)$ are negligibly small for its tiny coupling to $\eta\Lambda$. To understand the strong coupling properties of the low-lying negative parity $\Lambda$ resonances extracted from the $\bar{K}N$ scattering, we further study their strong decays. It is found that these resonances are most likely mixed states between different configurations. Considering these low-lying negative parity $\Lambda$ resonances as mixed three-quark states, we can reasonably understand both their strong decay properties from Particle Data Group and their strong coupling properties extracted from the $\bar{K}N$ scattering. As a byproduct, we also predict the strong decay properties of the missing $D$-wave state $|\Lambda\frac{3}{2}^-\ >_3$ with a mass of $\sim1.8$ GeV. We suggest our experimental colleagues search it in the $\Sigma(1385)\pi$ and $\Sigma\pi$ channels.