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$_{sw}$. It is summarized in a fit formula c$_{sw}$(g$_{0}^{2}$ ) that defines an improved action suitable for future dynamical charm simulations.