$ \bar K^0 d $ Bound State and Correlation Function

Abstract

We study the $\bar{K}^0d$ system using a new formulation of the fixed-center approximation that preserves elastic unitarity. The resulting scattering amplitude predicts a bound state below threshold, which can be interpreted as a $\Lambda(1380)N$ configuration complementary to the $K^-pp$ state associated with the higher $\Lambda(1405)$ pole. The interaction is attractive, with scattering parameters of the same order as recent $K^-d$ determinations. We further calculate the $\bar{K}^0d$ correlation function, which exhibits a characteristic structure associated with the bound state and provides a Coulomb-free observable that can be tested in future ALICE measurements. Results obtained with two different $\bar{K}N$ models are very similar, indicating the robustness of the predictions against the choice of the underlying interaction.