$Λ_{QCD}$ from gluon and ghost propagators

Abstract

Fundamental quantities of QCD, such as the strong coupling and $Λ_{QCD}$, are studied in the framework of lattice QCD with $N_f=2$ twisted mass fermions. In particular, the contact between lattice and continuous calculations is made by comparing the renormalized ghost-gluon vertex in MOM scheme with 4-loop perturbative results. A power correction is needed in order to have agreement between the two descriptions. This suggests the presence of a dimension-two $\VEV{A^2}$ gluon condensate whose value is found to be higher than in the quanched case.

8 pages. Presented at the XXVII International Symposium on Lattice Field Theory, July 26-31, 2009, Peking University, Beijing, China