  We develop a unitarity method to compute one-loop amplitudes with massless
propagators in d=4-2*epsilon dimensions. We compute double cuts of the loop
amplitudes via a decomposition into a four-dimensional and a
-2*epsilon-dimensional integration. The four-dimensional integration is
performed using spinor integration or other efficient techniques. The remaining
integral in -2*epsilon dimensions is cast in terms of bubble, triangle, box,
and pentagon master integrals using dimensional shift identities. The method
yields results valid for arbitrary values of epsilon.
