Excited and exotic charmonium, $D_s$ and $D$ meson spectra for two light quark masses from lattice QCD

TL;DR

This study uses lattice QCD to compute highly-excited charmonium, $D_s$, and $D$ meson spectra at two light quark masses, identifying hybrid mesons and observing minimal dependence on light-quark mass.

Contribution

It provides the first detailed lattice QCD spectra of excited and hybrid mesons with two different light-quark masses, including exotic states.

Findings

Spectra show only mild dependence on light-quark mass.

Identification of exotic and hybrid mesons with gluonic excitations.

Consistent pattern of states across different light-quark masses.

Abstract

We present highly-excited charmonium, $D_s$ and $D$ meson spectra from dynamical lattice QCD calculations with light quarks corresponding to $M_{\pi} \sim 240$ MeV and compare these to previous results with $M_{\pi} \sim 400$ MeV. Utilising the distillation framework, large bases of carefully constructed interpolating operators and a variational procedure, we extract and reliably identify the continuum spin of an extensive set of excited mesons. These include states with exotic quantum numbers which, along with a number with non-exotic quantum numbers, we identify as having excited gluonic degrees of freedom and interpret as hybrid mesons. Comparing the spectra at the two different $M_\pi$, we find only a mild light-quark mass dependence and no change in the overall pattern of states.