Computation of Λˉ\bar{\Lambda} and λ1\lambda_1 with Lattice QCD

We pursue a new method, based on lattice QCD, for determining the quantities $\bar{\Lambda}$, $\lambda_1$, and $\lambda_2$ of heavy-quark effective theory. We combine Monte Carlo data for the meson mass spectrum with perturbative calculations of the short-distance behavior, to extract $\bar{\Lambda}$ and $\lambda_1$ from a formula from HQET. Taking into account uncertainties from fitting the mass dependence and from taking the continuum limit, we find $\bar{\Lambda} = 0.68{+0.02}_{-0.12} \text{GeV}$ and $\lambda_1 = -(0.45 \pm 0.12) \text{GeV}^2$ in the quenched approximation.Comment: 7 pp, 4 figs (in v2 Fig. 4 now shows Ref. 13, as advertised); in v3 error in BLM scale is correcte

The decay constants fDs and fD+ form lattice QCD

Recent calculations of the decay constants in lattice QCD are reviewed and compared to experiment. The decay constants are tabulated in Table 2 and plotted in Figure 2. The most precise f{sub Ds} value is from HPQCD. It is about 2{sigma} higher than their previous result. The change is due to a more precise determination of the lattice spacing and better tuning of the quark masses. They have updated f{sub D+} using the new f{sub Ds} and their older f{sub Ds}/f{sub D+} ratio which is expected to be less sensitive to mistuning of the lattice spacing and masses. The preliminary FNAL/MILC f{sub Ds} value is about 1.4{sigma} higher than the HPQCD result but with a larger error. The f{sub D+} values, however, are in better agreement. FNAL/MILC expect to finalize their results once the charm quark mass tuning is complete. The two flavor ETM f{sub D+} value is about 1.6{sigma} lower than the HPQCD value while f{sub Ds} is in better agreement. It is not clear how much of the difference is from neglecting the strange sea quark, given the errors. Lattice and experiment differ most significantly for f{sub Ds}. Figure 3 shows Kronfeld's (updated) history of f{sub Ds}. The yellow bands depict the evolution of the experimental average while the three-flavor lattice average is shown in grey. The right-hand scale and green lines show the differences in sigmas. The 3.8{sigma} discrepancy around t {approx} 2 provoked the 'f{sub Ds} puzzle'. That discrepancy has now shrunk to 1.6{sigma}. Future lattice and experiment will be decisive