The Ξ(1620) and Ξ(1690) molecular states from S = −2 meson-baryon interaction up to next-to-leading order

We have studied the meson-baryon interaction in the neutral $S=-2$ sector using an extended Unitarized Chiral Perturbation Theory, which takes into account not only the leading Weinberg-Tomozawa term (as all the previous studies in $S=-2$ sector), but also the Born terms and next-to-leading order contribution. Based on the SU(3) symmetry of the chiral Lagrangian we took most of the model parameters from the BCN model \cite{Feijoo:2018den}, where these were fitted to a large amount of experimental data in the neutral $S=-1$ sector. We have shown that our approach is able to generate dynamically both $\Xi(1620)$ and $\Xi(1690)$ states in very reasonable agreement with the data, and can natura…