A Fully Numerical Approach to One-Loop Amplitudes
  We suggest a new approach for the automatic and fully numerical evaluation of one-loop scattering amplitudes in perturbative quantum field theory. We use suitably formulated dispersion relations to perform the calculation as a convolution of tree-level amplitudes. This allows to take advantage of the iterative numerical algorithms for the evaluation of leading order matrix elements. 
M. Moretti, F. Piccinini, A.D. Polosa