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.