O(a) improvement of lattice QCD with two flavors of Wilson quarks

Abstract

We consider O(a) improvement for two flavor lattice QCD. The improvement term in the action is computed non-perturbatively for a large range of the bare coupling. The position of the critical line and higher order lattice artifacts remaining after improvement are estimated. We also discuss the behavior of the HMC algorithm in our simulations.

Figures (9)

• Figure 1: Mass dependence of the lattice artifact $\Delta M$ at $\beta=6/g_0^2=5.4,c_{\rm sw}=1.7275$.
• Figure 2: Non-perturbatively determined improvement coefficient $c_{\rm sw}$ for $N_{\rm f}=2$. The dotted line shows first order perturbation theory impr:Wohlertimpr:pap2 and the dashed curve is the result for $N_{\rm f}=0$impr:pap3.
• Figure 3: The critical line in the improved theory. The dashed curve gives the polynomial approximation to the non-perturbative result and the dotted line indicates first order perturbation theory.
• Figure 4: $M$ and $M'$ for $\beta=5.4,c_{\rm sw}=1.7275$ (bottom part of the figure) and $\beta=5.2$, $c_{\rm sw}$ as given by eq. (\ref{['pade']}) (middle). The very top section is for $\beta=6.0, c_{\rm sw}=1.8659, N_{\rm f}=0$. The time extent of the lattice is $T = 16a$.
• Figure 5: The expectation value of the condition number, eq.(\ref{['condition_number']}). When more than one value is plotted at a given value of $g_0^2$ they correspond to different values of $c_{\rm sw}$. The tree-level value is shown at $g_0^2=0$.