Spin Structure of heavy-quark hybrids

TL;DR

This paper reviews recent theoretical advances in understanding the spin structure of heavy-quark hybrid mesons, combining effective field theories and lattice QCD data to analyze their spectrum and transitions.

Contribution

It introduces a nonrelativistic EFT framework for heavy hybrids, incorporating spin-dependent effects up to 1/m_Q^2, and fits nonperturbative coefficients to lattice data, extending predictions to bottomonium hybrids.

Findings

Determined nonperturbative matching coefficients from lattice QCD.

Predicted heavy hybrid spectra including spin effects.

Proposed a new approach to quarkonium transitions using hybrid states.

Abstract

Exotic quarkonia are candidates to new types of hadrons including four quarks or gluonic degrees of freedom as constituents, the latter being a unique feature of QCD. We review recent developments in nonrelativistic EFTs to describe exotic quarkonia and in particular recent results on the spectrum of heavy hybrids including spin-dependent contributions up to $1/m_Q^2$-terms in the heavy-quark-mass expansion. We determine the nonperturbative contributions to the matching coefficients of the EFT by fitting our results to lattice-QCD determinations of the charmonium hybrid spectrum and extrapolate the results to the bottomonium hybrid sector where lattice-QCD determinations are still challenging. We also report on a recent new approach to quarkonium hadronic transitions that does not use the twist expansion and uses the hybrid spectrum as the intermediate octet states.