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

Abstract

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 [1], 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 Ξ(1620) and Ξ(1690) states in very reasonable agreement with the data, and can naturally explain the puzzle with the decay branching ratios of Ξ(1690). Our results clearly illustrate the reliability of chiral models implementing unitarization in coupled channels and the importance of considering Born and NLO contributions for precise calculations.

Keywords

• Unitarized chiral perturbation theory
• Meson-baryon interaction
• Next-to-leading order
• Doubly strange baryon