ONE-LOOP N-POINT GAUGE-THEORY AMPLITUDES, UNITARITY AND COLLINEAR LIMITS

We present a technique which utilizes unitarity and collinear limits to construct ansatze for one-loop amplitudes in gauge theory. As an example, we obtain the one-loop contribution to amplitudes for n-gluon scattering in N = 4 supersymmetric Yang-Mills theory with the helicity configuration of the Parke-Taylor tree amplitudes. . We prove that our N = 4 ansatz is correct using general properties of the relevant one-loop n-point integrals. We also give the ''splitting amplitudes'' which govern the collinear behavior of one-loop helicity amplitudes in gauge theories.