Five-particle scattering at three loops confirms a key symmetry prediction

Using a six-dimensional unitarity-cut technique to generate masses and then reducing back to four dimensions, the authors computed the three-loop five-point scattering amplitude on the Coulomb branch of N=4 super-Yang-Mills. The result confirms that both infrared divergences and finite terms exponentiate as expected, with the leading double logarithm controlled by the octagon anomalous dimension. A surprise emerges at this loop order: each of the three independent kinematic structures in the amplitude carries its own distinct function of the 't Hooft coupling, a feature invisible at two loops.