QCD and the strange baryon spectrum

The strange quark plays a unique role in QCD, reflecting its intermediate mass between the light and heavy quarks. In recent years, remarkable progress has been made in the spectroscopy of baryons with strangeness. Many new features of the strange baryon spectrum have been revealed by accurate experimental data with novel techniques, as well as systematic developments of theoretical framework to describe hadron resonances. The basic properties of strange baryons, namely, the pole positions, spin and parity, and decay branching ratios, are being determined accurately. As a consequence, the Particle Data Group has added new entries in the particle listings, such as the Lambda(1380) and the Omega(2012). The developments of the spectroscopy stimulate intensive discussion on the exotic internal structure of strange baryons beyond the ordinary three-quark configuration. In this review, we introduce the basics of QCD, the scattering theory, and the exotic internal structure of hadrons, emphasizing the importance of the pole positions of the scattering amplitude for the characterization of hadron resonances. We then summarize the current status of selected strange baryon resonances; Lambda(1405), Lambda(1670), Xi(1620), Xi(1690), and Omega(2012), from theoretical and experimental viewpoints. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The unique role of the strange quark in QCD and the remarkable progress in the spectroscopy of baryons with strangeness have been highlighted. Accurate determination of the basic properties of strange baryons is achieved through experimental data and theoretical developments, leading to additions in the particle listings. Intensive discussions on the exotic internal structure of strange baryons have been stimulated by the developments in spectroscopy.