Lattice measurement of s with a realistic charm quark

Abstract

We report on an estimate of s, renormalised in the MS scheme at the and Z0 mass scales, by means of lattice QCD. Our major improvement compared to previous lattice calculations is that, for the first time, no perturbative treatment at the charm threshold has been required since we have used statistical samples of gluon fields built by incorporating the vacuum polarisation effects of u/d, s and c sea quarks. Extracting s in the Taylor scheme from the lattice measurement of the ghost-ghost-gluon vertex, we obtain MS s (m2 Z) = 0.1200(14) and MS s (m2 ) = 0.339(13).