We complete the non-perturbative calculations of the strange quark mass and the Lambda parameter in two flavor QCD by the ALPHA collaboration. The missing lattice scale is determined via the kaon decay constant, for whose chiral extrapolation complementary strategies are compared. We also give a value for the scale r_0 in physical units as well as an improved determination of the renormalization constant Z_A.Comment: 46 pages, 11 figures, v2: minor corrections, results unchange

, where a is the lattice spacing. In unquenched simulations with O(a) improved Wilson fermions we do not obtain a scaling law but find results compatible with the behavior that we find in the pure gauge theory. The discussion is supported by a large set of ensembles both in pure gauge and in the theory with two degenerate sea quarks. We have moreover investigated the effect of slow algorithmic modes in the error analysis of the expectation value of typical lattice QCD observables (hadronic matrix elements and masses). In the context of simulations affected by slow modes we propose and test a method to obtain reliable estimates of statistical errors. The method is supposed to help in the typical algorithmic setup of lattice QCD, namely when the total statistics collected is of O(10)τ exp . This is the typical case when simulating close to the continuum limit where the computational costs for producing two independent data points can be extremely large. We finally discuss the scale setting in N f = 2 simulations using the Kaon decay constant f K as physical input. The method is explained together with a thorough discussion of the error analysis employed. A description of the publicly available code used for the error analysis is included.ii ZusammenfassungIn dieser Arbeit untersuchen wir das Critical Slowing down der Gitter-QCD Simulationen. Wir führen eine Vorstudie in der quenched Approximation durch, in der wir feststellen, dass unsere Schätzung der exponentiellen Autokorrelation wie iii

Simulations of QCD are known to suffer from serious critical slowing down towards the continuum limit. This is particularly prominent in the topological charge. We investigate the severeness of the problem in the range of lattice spacings used in contemporary simulations and propose a method to give more reliable error estimates.

We present a computation of the charm quark's mass and the leptonic D-meson decay constants f D and f D s in two-flavour lattice QCD with non-perturbatively O(a) improved Wilson quarks. Our analysis is based on the CLS configurations at two lattice spacings (a = 0.065 and 0.048 fm, where the lattice scale is set by f K ) and pion masses ranging down to ∼ 190 MeV at Lm π 4, in order to perform controlled continuum and chiral extrapolations with small systematic uncertainties. PoS(LATTICE 2013)475Charm quark mass and D-meson decay constants from Table 1: Parameters of the ensembles used: ensemble label, spatial extent of the lattice in lattice units, bare coupling β = 6/g 2 0 , lattice spacing a, hopping parameters of the sea and (valence) strange quarks, the mass of the sea pion and the number of configurations employed. All lattices have dimensions T ×L 3 with T = 2L.

We present a computation of the charm quark's mass and the leptonic D-meson decay constants f D and f D s in two-flavour lattice QCD with non-perturbatively O(a) improved Wilson quarks. Our analysis is based on the CLS configurations at two lattice spacings (a = 0.065 and 0.048 fm, where the lattice scale is set by f K ) and pion masses ranging down to ∼ 190 MeV at Lm π 4, in order to perform controlled continuum and chiral extrapolations with small systematic uncertainties.