Infrared Features of Lattice Landau Gauge QCD and the Gribov Copy Problem

Infrared features of gluon propagator, ghost propagator, QCD running coupling and the Kugo-Ojima parameter in lattice Landau gauge QCD are presented. The framework of PMS analysis suggests that there appear infrared, intermediate and ultraviolet regions specified by $\Lambda_{\bar{MS}}$, $\beta_0$ and $\beta_1$. The propagators and the running coupling of $q>1GeV$ are fitted by the $\widetilde{MOM}$ scheme using the factorization scale as the scale parameter. The running coupling data of $q<14GeV$ are fitted by the contour improved perturbation method. The Gribov copy problem is studied in SU(2), $\beta= 2.2$ samples by comparing the data gauge fixed by the parallel tempering method and the data gauge fixed by the straightforward gauge fixing. The Gribov noise effect turned out to be about 2%.