Light-quarkonium spectra and orbital-angular-momentum decomposition in a Bethe-Salpeter-equation approach

TL;DR

This paper uses a covariant Dyson-Schwinger-Bethe-Salpeter approach to analyze light quarkonium spectra, orbital angular momentum properties, and mass splittings, providing predictions and comparisons with lattice QCD results.

Contribution

It offers a detailed covariant analysis of light quarkonium states, predicts exotic meson masses, and investigates orbital angular momentum content and pion-mass dependence, addressing discrepancies with lattice QCD.

Findings

Predicted mass of sbars exotic 1-+ states.

Identified orbital angular momentum content in rho meson excitations.

Found a pion-mass dependent crossing in orbital angular momentum assignments.

Abstract

We investigate the light quarkonium spectrum using a covariant Dyson-Schwinger-Bethe-Salpeter-equation approach to QCD. We discuss splittings among as well as orbital angular momentum properties of various states in detail and analyze common features of mass splittings with regard to properties of the effective interaction. In particular, we predict the mass of sbars exotic 1-+ states, and identify orbital angular momentum content in the excitations of the rho meson. Comparing our covariant model results, the rho and its second excitation being predominantly S-wave, the first excitation being predominantly D-wave, to corresponding conflicting lattice-QCD studies, we investigate the pion-mass dependence of the orbital-angular-momentum assignment and find a crossing at a scale of $m_\pi$ ~ 1.4 GeV. If this crossing turns out to be a feature of the spectrum generated by lattice-QCD studies as well, it may reconcile the different results, since they have been obtained at different values of $m_\pi$.