Improved Lattice QCD Actions for Hadron Phenomenology
  The masses and dispersions of light hadrons are calculated in lattice QCD using an order a^2 tadpole-improved gluon action and the Dchi34 action, an order a^2 tadpole-improved next-nearest-neighbor fermion action originally proposed by Hamber and Wu. Two lattices of constant volume with lattice spacings of approximately 0.40 fm and 0.24 fm are considered. The results reveal some scaling violations at the coarser lattice spacing on the order of 5%. At the finer lattice spacing, the calculated N/rho mass ratio reproduces state-of-the-art results using unimproved actions. Good dispersion and rotational invariance up to momenta p*a the order of 1 are also found. The relative merit of alternative choices for improvement operators is assessed through close comparisons with other plaquette-based tadpole-improved actions. 
Derek B. Leinweber and Frank X. Lee