$\bar{K}Λ$ molecular explanation to the newly observed $Ξ(1620)^0$

Abstract

The newly observed $Ξ(1620)^0$ by the Belle Collaboration inspires our interest in performing a systematic study on the interaction of an anti-strange meson $(\bar{K}^{(*)})$ with a strange or doubly strange ground octet baryon $\mathcal{B}$ ($Λ$, $Σ$, and $Ξ$), where the spin-orbit force and the recoil correction are considered in the adopted one-boson-exchange model. Our results indicate that $Ξ(1620)^0$ can be explained as a $\bar{K}Λ$ molecular state with $I(J^P)=1/2(1/2^-)$ and the intermediate force from $σ$ exchange plays an important role. Additionally, we also predict several other possible molecular candidates, i.e., the $\bar{K}Σ$ molecular state with $I(J^P)=1/2(1/2^-)$ and the triply strange $\bar{K}Ξ$ molecular state with $I(J^P)=0(1/2^-)$.