QCD and the Strange Baryon Spectrum

Abstract

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 have 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.

arXiv comment64 pages, 21 figures, to appear in Prog. Part. Nucl. Phys

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Cited by in corpus (23)

• Towards a theory of hadron resonances
• First study of the two-body scattering involving charm hadrons
• Constraining the $\overline{\mathrm{K}}\mathrm{N}$ coupled channel dynamics using femtoscopic correlations at the LHC
• Cross-channel constraints on resonant antikaon-nucleon scattering
• Two-pole nature of the $\Lambda (1405)$ from lattice QCD
• Lattice QCD study of $\pi \Sigma -\bar{K}N$ scattering and the $\Lambda (1405)$ resonance
• Analysis of the $\mathbf{\gamma \gamma }\to \mathbf{D}\bar{\mathbf{D}}$ reaction and the $D\bar{D}$ bound state
• Interpretation of the ${\Omega }_c\to {\pi }^{+}\Omega (2012)\to {\pi }^{+}(\bar{K}\Xi )$ relative to ${\Omega }_c\to {\pi }^{+}\bar{K}\Xi$ from the $\Omega (2012)$ molecular perspective
• SPring-8 LEPS2 beamline: A facility to produce a multi-GeV photon beam via laser Compton scattering
• New insights into the nature of the $\Lambda (1380)$ and $\Lambda (1405)$ resonances away from the SU(3) limit
• Pole position of $\Lambda (1405)$ measured in $d(K^{-},n)\pi \Sigma$ reactions
• Particle-dimer approach for the Roper resonance in a finite volume
• Understanding the nature of $\Omega (2012)$ in a coupled-channel approach
• First Observation of the Semileptonic Decay ${\Lambda }_c^{+}\to p{K}^{-}{e}^{+}{\nu }_e$
• Charm-baryon semileptonic decays and the strange ${\Lambda }^{\ast }$ resonances: New insights from lattice QCD
• Structure of the $\mathbf{\Lambda }(1670)$ resonance
• Compositeness of hadrons, nuclei, and atomic systems
• Identifying triple-strangeness $\Omega$ hyperons in light of recent experimental results
• Structure of the ${\Omega }^{-}(2012)$ with Hamiltonian Effective Field Theory
• Double-strangeness exchange reactions in a hybrid Regge-plus-resonance approach
• Nature of excited $\Xi$ baryons with threshold effects
• Emergence of the $\pi (1300)$ Resonance from Lattice QCD
• Compositness and wave function of shallow bound states in relation to scattering observables