Heavy Quarkonium Hybrids

TL;DR

This paper advances the understanding of heavy quarkonium hybrids by incorporating mixing effects with quarkonium states using a comprehensive effective field theory approach, providing detailed spectra and decay insights.

Contribution

It introduces a systematic framework combining NRQCD, lattice QCD, and effective string theories to analyze hybrid and quarkonium mixing beyond the Born-Oppenheimer approximation.

Findings

Spectrum of charmonium and bottomonium hybrids calculated.

Most isospin zero $XYZ$ resonances fit into the hybrid or quarkonium spectrum.

Enhanced spin symmetry violations explain certain decay patterns.

Abstract

We report on a recent investigation on heavy quarkonium hybrids that goes beyond the usual Born-Oppenheimer approximation by including not only the mixing between nearby hybrid states but also the mixing with quarkonium states. We use a systematic effective field theory framework based on NRQCD together with lattice QCD inputs. Short and long distance constraints from weak coupling pNRQCD and the QCD effective string theory are also employed. We calculate the quarkonium and hybrid spectrum for charmonium and bottomonium, and estimate a number of decay widths. Most of the isospin zero $XYZ$ resonances fit in our spectrum either as quarkonia or as hybrid states. The mixing of hybrid states with quarkonia produces enhanced spin symmetry violations, which are instrumental to understand certain decays. We also present new results on the hyperfine splittings.