On-shell improved lattice QCD with staggered fermions

By using Symanzik's improvement program, we study the on-shell improved lattice QCD with staggered fermions. We find that there are, in total, 5 independent lattice operators of dimension of six (including both gauge and fermion operators) which must be added to the unimproved action to form an $O(a^2)$ improved action. The tree-level and tadpole-improved tree-level coefficients are given