Cutoff effects in maximally twisted LQCD
  The Symanzik analysis of correlators in lattice QCD with maximally twisted Wilson fermions reveals that there exist cutoff artifacts which tend to become large as the quark mass gets small. We show that these effects can be reduced to a negligible level by either introducing the clover term in the action or, as already suggested in the literature, by a suitable choice of the critical mass. Recent simulation data support these conclusions. 
Giancarlo Rossi, Roberto Frezzotti, Guido Martinelli and Mauro   Papinutto