Light quark masses and pseudoscalar decay constants from Nf=2 lattice QCD with twisted mass fermions

Abstract

We present the results of a lattice QCD calculation of the average up-down and strange quark masses and of the light meson pseudoscalar decay constants with Nf=2 dynamical fermions. The simulation is carried out at a single value of the lattice spacing with the twisted mass fermionic action at maximal twist, which guarantees automatic O(a)-improvement of the physical quantities. Quark masses are renormalized by implementing the non perturbative RI-MOM renormalization procedure. Our results for the light quark masses are mud(MSbar,2 GeV) = 3.85 ± 0.12 ± 0.40 MeV, ms(MSbar,2 GeV) = 105 ± 3 ± 9 MeV and ms/mud = 27.3 ± 0.3 ± 1.2. We also obtain fK = 161.7 ± 1.2 ± 3.1 MeV and the ratio fK/fπ = 1.227 ± 0.009 ± 0.024. From this ratio, by using the experimental determination of Γ(K → μbar nuμ(γ))/Γ(π → μbar nuμ(γ)) and the average value of |Vud| from nuclear beta decays, we obtain |Vus| = 0.2192(5)(45), in agreement with the determination from Kl3 decays and the unitarity constraint.