Investigation of $qqqs\bar{q}$ pentaquarks in a chiral quark model

Abstract

We investigate the pentaquark system $qqqs\bar{q}$ in a framework of chiral quark model. Two structures, $(qqq)(s\bar{q})$ and $(qqs)(q\bar{q})$, with all possible color, spin, flavor configurations are considered. The calculations show that there are several possible resonance states, $Sigma\pi$ and $N\bar{K}$ state with $I{J}^P=0{\frac{1}{2}}^{-}$, ${\Sigma }^{\ast }\pi$ with $I{J}^P=0{\frac{3}{2}}^{-}$, ${\Sigma }^{\ast }\rho$ with $I{J}^P=0{\frac{5}{2}}^{-}$, $\Delta \bar{K}$ with $I{J}^P=1{\frac{3}{2}}^{-}$ and $\Delta {\bar{K}}^{\ast }$ with $I{J}^P=1{\frac{5}{2}}^{-}$. Where the $N\bar{K}$ state with $I{J}^P=0{\frac{1}{2}}^{-}$ can be used to explain the $\Lambda (1405)$, and together with another state $\Sigma \pi$ is related to the two-pole structure of the scattering amplitude proposed before. The decay properties of $\Lambda (1520)$ prevent the assignment of ${\Sigma }^{\ast }\pi$ with $I{J}^P=0{\frac{3}{2}}^{-}$ to $\Lambda (1520)$, although the energy $\sim$ 1518 MeV of ${\Sigma }^{\ast }\pi$ is close to experimental value of $\Lambda (1520)$. Other resonance states generally have a large width.

Comments: 9 pages