The high energy limit of QCD at two loops

By taking the high-energy limit of the two-loop amplitudes for parton-parton scattering, we have tested the validity of the loop expansion of the high-energy amplitude, arising from a reggeized gluon passed in the crossed channel. As expected, we have found that it holds at LL and NLL accuracy, and hence we have independently re-evaluated the two-loop Regge trajectory, finding full agreement with the previous results by Fadin and collaborators. We have found, though, that the universality implied by the exchange of a single reggeized gluon in the crossed channel is violated at the next-to-next-to-leading logarithmic level.