Symanzik Improvement with Dynamical Charm: A 3+1 Scheme for Wilson Quarks

We discuss the problem of lattice artefacts in QCD simulations enhanced by the introduction of dynamical charmed quarks. In particular, we advocate the use of a massive renormalization scheme with a close to realistic charm mass. To maintain O(a) improvement for Wilson type fermions in this case we define a finite size scheme and carry out a nonperturbative estimation of the clover coefficient $c_{\mathrm{s}\mathrm{w}}$. It is summarized in a fit formula $c_{\mathrm{s}\mathrm{w}}(g_0^2)$ that defines an improved action suitable for future dynamical charm simulations.