Hadronic Spectroscopy from the Lattice: Glueballs and Hybrid Mesons

Lattice QCD determinations appropriate to hadron spectroscopy are reviewed with emphasis on the glueball and hybrid meson states in the quenched approximation. Hybrids are discussed for heavy and for light quarks. The effects of sea quarks (unquenching) are explored. Heavy-light systems are presented - particularly excited B mesons.

Lattice QCD predicts a rich spectroscopy of glueballs and $q\bar{q}-$glue h ybrids. I compare these with data and assess the emerging empirical situation. Questions for the lattice are proposed.

Our current knowledge about glueballs and hybrid mesons from lattice QCD simulations is briefly reviewed.

We discuss states in the meson spectrum which have explicit gluonic components. Glueballs (with no valence quarks) and hybrid mesons (with valence quarks) are both reviewed. We present in some detail lattice simulation results. ( to appear in proceedings of QCD-20 years, Aachen Workshop)

Topics covered in this review are the lattice gauge theory approach to the evaluation of non-perturbative hadronic interactions from first principles, particularly applications to glueballs, inter-quark potentials, the running coupling constant and hybrid mesons. Also discussed are the limitations of the quenched approximation.

The spectroscopy of light and heavy mesons is reviewed with emphasis on glueballs, hybrids, and tetraquarks.

The status of non-perturbative QCD calculations for mesons with gluonic excitation is presented. Lattice results for the glueball spectrum are reviewed. For hybrid mesons, the heavy quark results are summarised and new results are presented for light quarks. Preliminary results for the spectrum of light-quark hybrid mesons indicate substantial mixing with quark model states for non-exotic $J^{PC}$. For the exotic $J^{PC}$ hybrid mesons, the $J^{PC}=1^{-+}$, $0^{+-}$ and $2^{+...

A review of new results from lattice simulations of glueballs and heavy-quark hybrid mesons is presented.

I review the present status of lattice calculations of properties of gluon-rich hadrons and comment on future prospects, in view of planned experiments.

I present recent developments in the lattice QCD calculations of the light hadron spectrum. Emphasis is placed on the limitation of the quenched approximation in reproducing the observed spectrum and indications that the discrepancy is reduced by introducing two flavors of light dynamical quarks.