  The masses and dispersions of light hadrons are calculated in lattice QCD
using an O(a^2) tadpole-improved gluon action and an O(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 mass ratios reproduce state-of-the-art results using unimproved
actions. Good dispersion and rotational invariance up to momenta of pa ~ 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.
