D-dimensional unitarity cut method

Abstract We develop a unitarity method to compute one-loop amplitudes with massless propagators in d = 4 − 2 ϵ dimensions. We compute double cuts of the loop amplitudes via a decomposition into a four-dimensional and a − 2 ϵ -dimensional integration. The four-dimensional integration is performed using spinor integration or other efficient techniques. The remaining integral in − 2 ϵ 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 ϵ.