Session G1: Lattice QCD and the Hadron Spectrum

The Meson Spectrum from Lattice QCD

I will report on recent progress in extracting the spectrum of excited mesons from lattice QCD computations. Spectra of mesons across all $J^{PC}$ with $J \le 4$ are now accessible with multiple excited states in each channel. Exotic hybrid meson results of unprecedented statistical precision suggest that these enigmatic states should indeed be within the energy reach of the GlueX experiment at JLab 12 GeV. I will also discuss current attempts being made to study the decay of resonances within QCD and how lattice QCD results can be used to build phenomenological models constrained by non- perturbative QCD.   

The baryon spectrum from lattice QCD

The spectrum of hadronic excitations observed in nature is believed to be described by the theory of the strong interaction known as Quantum Chromodynamics (QCD). Monte Carlo studies, based on the lattice regularization of QCD, provide a means of computing hadron properties from first principles. However, the reliable determination of excited-state energies from lattice QCD involves a number of significant technical challenges. I will report on recent progress in extracting the excited baryon spectrum from numerical studies which incorporate the effects of light and strange sea quarks, with light quark masses approaching the physical point. Crucially, these studies attempt to account for threshold effects in a systematic fashion. They will ultimately lead to reliable estimates for baryon masses, resonance energies and widths across a range of flavor sectors, which can justifiably be compared with experiment. Moreover, by varying the quark mass in these simulations and using a large and varied set of hadronic interpolators, one hopes to gain some insight into the degrees of freedom relevant to states of particular theoretical interest, such as the Roper resonance in the nucleon sector.   

The Experimental Spectrum of Hadrons

A key goal of Lattice QCD is to predict the experimentally-observed spectrum of hadrons. I will review existing experimental data on the hadron spectrum as it relates to recent Lattice QCD calculations. In addition I will discuss future experimental prospects for hadron spectroscopy with a focus on areas where experiment may directly test the predictions of Lattice QCD.