Internal structure of Ω(2012) baryon in a coupled-channel approach

Recently, KEK/Belle has discovered the negative-party lowest excited state of the Omega baryon, Ω(2012), which contains three strange quarks. The standard quark model suggests that this is the first orbital P-wave excited state of a single strange quark. On the other hand, since the mass of Ω(2012) is close to the Ξ^*K^bar threshold, it can also be interpreted as a meson-baryon molecule of Ξ^*K^bar . Thus, despite being the lowest energy excited state, the internal structure of Ω(2012) is still poorly understood.

Either one of the two structures, quark models like or molecule like, is realized only in the ideal limit, and they must coexist and mix to form the physical states. Therefore, the question is how they mix for the real state and what is the important basis state for explaining the physical properties of Ω(2012) baryon, such as mass spectra and its decays.

To understand the internal structure of Ω(2012) baryon, we perform a systematic analysis in a coupled-channel approach including the three-quark state and the Ξ^*K^bar molecular state. For the latter, we also include possible effective Ξ^*K^bar interactions by considering other possible coupled channels for a dynamically generated state. Our results suggest that both three-quark core and Ξ^*K^bar channel are essential for the description of the Ω(2012) resonance. The spectroscopy of multiple strangeness baryons provides a good bridge for understanding the properties of hadrons from the light quark region to the heavy quark region.