Strong Running Coupling atτandZ0Mass Scales from Lattice QCD

Abstract

This letter reports on the first computation, from data obtained in lattice QCD with u, d, s and c quarks in the sea, of the running strong coupling via the ghost-gluon coupling renormalized in the MOM Taylor scheme. We provide with estimates of α MS (m 2 τ ) and α MS (m 2 Z ) in very good agreement with experimental results. Including a dynamical c quark makes safer the needed running of α MS .

Three-gluon Green functions: low-momentum instanton dominance and zero-crossing

“…In the next section, we will focus, in particular, in the first one corresponding to the so-called MOM symmetric 3-gluon coupling. Apart from the previous gauge-field lattice configurations, for the coupling analysis and comparison purpose, we have furthermore exploited the unquenched lattice configurations with two degenerate light dynamical (u and d) and two heavier (s and c) flavors which made possible a successful determination of the MS running coupling at the Z 0 -mass scale [24].…”

Alpha, Lambda and Gluon condensate: Precision sudies with dynamical charm

“…where A a µ is the gauge field and M ab ≡ ∂ µ D ab µ is the Fadeev-Popov operator.The lattice setup is described in [18] and summarized in Tab. 1.…”

“…Finally, one can impose the condensates to be the same for both gluon and ghost propagators, which leads to g 2 A 2 = 4.1 GeV 2 , that appears to be again in a pretty good agreement with the previous results in refs. [17,18]. In the following, we will use the artefacts-free gluon and ghost dressing functions, obtained with this last value for the gluon condensate, shown in Fig.…”

“…As we did in ref. [17,18,30] for the Taylor coupling and the vector quark propagator, the gluon propagator renormalization constant Z Latt 3 in MOM scheme can be written as…”

“…[17,18] for N f =2+1+1 and in refs. [7,19] for N f =0 and N f =2 quark flavours respectively, we calculate the running coupling by equating numerical results and the OPE prediction.…”