Understanding Hadron Structure from Lattice QCD in the SciDAC Era

John W. Negele, MIT

The structure of neutrons, protons, and other strongly interacting particles in terms of their quark and gluon constituents can be calculated from first principles by solving QCD on a discrete space time lattice. With the advent of SciDAC software and prototype clusters and of DOE supported dedicated lattice QCD computers, it is now possible for the first time to calculate physical observables using full QCD in the regime of large lattice volumes and light quark masses that can be compared with experiment. This talk will explain how hadron structure is calculated on the lattice, and show results for nucleon electromagnetic form factors characterizing the distribution of charge and current in the nucleon, the longitudinal momentum distribution of quarks in the nucleon, the transverse structure of the nucleon, the origin of the nucleon spin, and baryon shapes, It will also show how lattice QCD provides insight into questions of hadron structure, such as the nature of the pentaquark states that have been explored in recent experiments.