Quark Propagator from LQCD and Its Physical Implications

Abstract

The quark propagator lies at the core of lattice hadron spectrum calculations as well as studies in other nonperturbative schemes. It manifestly displays dynamical chiral symmetry breaking and can be used to connect nonperturbative methods with perturbation theory. The quark propagator can also provide direct information on lattice simulations and act as a test-bed for improvement. We investigate the lattice quark propagator with standard (Kogut-Susskind) and improved (Asqtad) Staggered actions and with the Overlap action. These actions are seen to have excellent ultraviolet behaviour as well as being useful for studying infrared properties. By using a variety of actions as well as varying the lattice parameters we are able to obtain good control over systematic errors in the quenched case. Gauge dependent quantities from lattice simulations may be affected by Gribov copies. We explore this by studying the quark propagator in both Landau and Laplacian gauges. Laplacian gauges are unambiguous, i.e. free of Gribov copies. Landau and Laplacian gauges are found to produce very similar results for the quark propagator. From the quark propagator we are able to compute the chiral condensate and running quark mass. Results from Staggered and Overlap actions are in excellent agreement. The data is also used to construct ansatze suitable for model hadron calculations as well as adding to our intuitive understanding of QCD.