O(a) improvement of the axial current in lattice QCD to one-loop order   of perturbation theory
  The conservation of the isovector axial current in lattice QCD with massless Wilson quarks is studied to one-loop order of perturbation theory. Following a strategy described in a previous publication, the O($a$) counterterm required for on-shell improvement of the current is computed. We also confirm an earlier result of Wohlert for the coefficient in front of the SW term in the improved action. 
M. L\"uscher (DESY) and P. Weisz (Max-Planck-Institut fuer Physik)