Investigation of $\Lambda(1405)$ as a molecular pentaquark state

Abstract

$\Lambda(1405)$ is one of the interesting particles with its unclear structure and distinct properties. It has a light mass compared to its non-strange counterpart, despite the strange quark it carries. This situation puts the investigation of this resonance among the hot topics in hadron physics and collects attention to clarify its properties. In this study, we focus on the calculation of the mass and residue of the $\Lambda(1405)$ resonance within the framework of QCD sum rules. We assign a structure in the form of a molecular pentaquark composed from admixture of $K^-$ meson-proton and $\bar{K}^0$ meson-neutron. Using an interpolating current in this form, the masses and the current coupling constant are attained as $m=1406\pm 128~\mathrm{MeV}$ and $\lambda=(3.35\pm 0.35)\times10^{-5}~\mathrm{GeV}^6$ for $\slashed{q}$ and $m=1402\pm 141~\mathrm{MeV}$ and $\lambda=(4.08\pm 1.08)\times10^{-5}~\mathrm{GeV}^6$ for $I$ Lorentz structures entering the calculations, respectively. The obtained mass values agree well with the experimental data supporting the plausibility of the considered structure.