Maximal Unitarity at Two Loops

Abstract

We discuss the extension of the maximal-unitarity method to two loops, focusing on the example of the planar double box. Maximal cuts are reinterpreted as contour integrals, with the choice of contour fixed by the requirement that integrals of total derivatives vanish on it. The resulting formulæ, like their one-loop counterparts, can be applied either analytically or numerically.