Rationale for UV-filtered clover fermions

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We study the contributions Sigma₀ and Sigma₁, proportional to a⁰ and a¹, to the fermion self-energy in Wilson's formulation of lattice QCD with UV-filtering in the fermion action. We derive results for mcrit and the renormalization factors Zₛ, Zₚ, Zᵥ, Zₐ to 1-loop order in perturbation theory for several filtering recipes (APE, HYP, EXP, HEX), both with and without a clover term. The perturbative series is much better behaved with filtering, in particular tadpole resummation proves irrelevant. Our non-perturbative data for mcrit and Zₐ/(Zₘ*Zₚ) show that the combination of filtering and clover improvement efficiently reduces the amount of chiral symmetry breaking -- we find residual masses amres=O(10⁻²).