## 26.04.12 17:15

# The excited-state spectrum of QCD through lattice gauge theory calculations

## David Richards (JLAB)

There has been a resurgence in interest in the spectroscopy of QCD, with the observation of new and unexpected states in charmonium, the search for the so-called missing baryon resonances, and major new spectroscopy efforts planned at PANDA, at Jefferson Lab, at BES and at other experimental facilities.

The calculation of the bound-state spectrum encapsulates our ability to describe the strong interactions, and high-precision calculations that can confront experiment are therefore vital. In this talk, I describe recent progress at describing the bound-state spectrum of QCD though first-principles lattice gauge calculations. I begin by outlining some of the theoretical, algorithmic and computational advances that are enabling these calculations. I then present recent results for the excited-state spectrum both of baryons and of mesons. I focus on the emergence of apparent collective degrees of freedom that describe our calculations, and the manifestation of gluonic degrees of freedom through the appearance of "hybrid" states. I conclude by outlining some of the remaining challenges, and the prospect for future calculations that can predict upcoming experiment.