Determination of ${\Lambda }_{\overline{MS}}$ from quenched and $N_f=2$ dynamical QCD

Abstract

The scale parameter ${\Lambda }_{\overline{MS}}$ is computed on the lattice in the quenched approximation and for $N_f=2$ flavors of light dynamical quarks. The dynamical calculation is done with non-perturbatively $O(a)$ improved Wilson fermions. In the continuum limit we obtain ${\Lambda }_{\overline{MS}}^{N_f=0}=243(1)(10)$ MeV and ${\Lambda }_{\overline{MS}}^{N_f=2}=217(16)(11)$ MeV, respectively.

Comments: 16 pages, 6 figures. Minor changes. Final version to be published in Phys. Lett. B