One loop QCD corrections to gg → at

We compute the one-loop corrections to gg → up to order in the dimensional-regularization parameter. We apply the projector method to compute polarized amplitudes, which generalize massless helicity amplitudes to the massive case. We employ a semi-numerical strategy to evaluate the scattering amplitudes. We express the form factors through scalar integrals analytically, and obtain separately integration by parts reduction identities in compact form. We integrate numerically the corresponding master integrals with an enhanced implementation of the Auxiliary Mass Flow algorithm. Using a numerical fit method, we concatenate the analytic and the numeric results to obtain fast and reliable evaluation of the scattering amplitude. This approach improves numerical stability and evaluation time. Our results are implemented in the Mathematica package TTH.