Resummation of Cactus Diagrams in the Clover Improved Lattice   Formulation of QCD
  We extend to the clover improved lattice formulation of QCD the resummation of cactus diagrams, i.e. a certain class of tadpole-like gauge invariant diagrams. Cactus resummation yields an improved perturbative expansion. We apply it to the lattice renormalization of some two-fermion operators improving their one-loop perturbative estimates. 
H. Panagopoulos (1), E. Vicari (2) ((1) Univ. of Cyprus (2) Univ. of   Pisa)