Session Y2: Solving QCD on the Lattice

Lattice Calculations of Hadron Structure

I describe recent lattice calculations in full QCD of nucleon spectrum. New theoretical techniques allow the extraction of several excited states of the nucleon. Also presented are nucleon electromagnetic form-factors and transition form-factors, moments of structure functions as well as moments of generalized parton distributions (GPD's) along with their comparison to experiments. Lattice calculations have excluded some proposed models of GPDs.   

Lattice Regularized QCD and the Quark-Gluon Plasma

Numerical calculations in the framework of lattice regularized QCD are of particular importance for our understanding of the phase structure of strongly interacting elementary particles at high temperature and non-vanishing baryon number density. The genuine non-perturbative processes and long range correlations that trigger the occurrence of phase transitions and dominate the thermodynamic properties in the vicinity of such transitions require the application of non-perturbative techniques. We will discuss the current understanding of the phase diagram of QCD as it emerges from lattice calculations at vanishing as well as non-vanishing baryon chemical potential. We will present recent results on the QCD equation of state, the transition temperature at vanishing baryon number density and the search for a genuine phase transition point at non-zero values of the baryon number density. We, furthermore, will comment on implications of these results for experimental studies of hot and dense matter in heavy ion collisions and their modeling in hydrodynamic simulations.   

Lattice Calculations of Hadronic Scattering

While lattice QCD is able to compute single-hadron properties to few-percent accuracy, only very recently has it become possible to extract precise information about the interactions between hadrons. I will review the methodology for extracting phase shifts from lattice correlation functions in a finite volume, and I will discuss recent progress in computing a variety of hadron-hadron scattering amplitudes using lattice QCD, including recent efforts to learn about the simplest nuclear systems.