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A local formulation of lattice QCD without unphysical fermion zero modes

The problem of unphysical zero modes in lattice QCD with Wilson fermions can be solved in a clean way by including a mass term proportional to $i \psibar γ_5 τ^3 ψ$ in the standard lattice theory with Nf=2 mass degenerate Wilson quarks. We argue that up to cutoff effects, this lattice theory is equivalent to standard lattice QCD, for suitable choices of the mass parameters and with a natural re-interpretation of observables. On-shell O(a) improvement can be implemented in a straightforward way.