Spectrum of Hadrons with Strangeness

Abstract

We describe a calculation of the spectrum of strange and nonstrange hadrons that simultaneously correlates the dressed-quark-core masses of meson and baryon ground-and excited-states within a single framework. The foundation for this analysis is a symmetry-preserving Dyson-Schwinger equation treatment of a vector×vector contact interaction. Our results exemplify and highlight the deep impact of dynamical chiral symmetry breaking on the hadron spectrum: an accurate description of the meson spectrum entails a similarly successful prediction of the spectrum of baryons, including those with strangeness. The analysis also provides numerous insights into baryon structure. For example, that baryon structure is largely flavour-blind, the first radial excitation of ground-state baryons is constituted almost entirely from axial-vector diquark correlations, and DCSB is the foundation for the ordering of low-lying baryon levels; viz., (1/2) + , (1/2) + , (1/2) − .

Baryons as relativistic three-quark bound states

“…These features are clearly visible in the contact interaction model of Refs. [333,344] and also persist in rainbow-ladder calculations as we will see in Sec. 3.6.…”

“…This is clearly visible, for instance, in the NJL calculation of Ref. [333] and we will return to this point in Sec. 3.5.…”

“…For reviews on the physics of the NJL model see e.g. [337,338]; applications for ground states of baryons are discussed in [339][340][341][342][343] and recent applications also to excited states and baryons with strangeness can be found in [333,344]. We discuss some of these results below in Sec.…”

“…[333], results on the excitation spectrum in the strange baryon sector are not yet available in the functional framework. On the lattice, there are only a couple of studies [35,36,416], agreeing with each other in the identification of the Λ(1405) with a dominant flavour singlet component in the operator basis.…”

Features and flaws of a contact interaction treatment of the kaon

“…(19) in Ref. [20] shows that, naturally, the transverse part of the rainbow-ladder vector vertex exhibits a pole at Q 2 = −m 2 K * ; i.e., at the mass of the lightest us-vector excitation.…”