  We develop a method for computing Mellin moments of single inclusive cross
sections such as Drell-Yan production directly from forward scattering
diagrams, by invoking unitarity in the form of cutting equations. We provide a
diagram-independent prescription for eliminating contributions from unwanted
cuts at the level of an expansion in the reciprocal omega=1/z variable. The
modified sum over powers of omega produces the result from physical cuts only,
with the nth coefficient precisely equal to the nth Mellin moment of the cross
section. We demonstrate and validate our method for representative one- and
two-loop diagrams.
