Generalised Unitarity at One-loop with Massive Fermions

We describe an application of generalised unitarity to the computation of one-loop amplitudes with massive external fermions. We present complete results for the leading colour contributions to the all-plus helicity configuration of the t (t) over bar gg amplitude. Using a special choice for the helicity basis for the massive fermions we are able to obtain extremely compact analytic expressions. In particular we describe how one can fix the divergent contributions from tadpole and wave-function renormalisation using universal UV and IR behaviour.