  Using the recently introduced STRIPPER approach to double-real radiation, we
evaluate the total cross sections for the main partonic channels of the
next-to-next-to leading order contributions to top quark pair production in
hadronic collisions: gg -> ttgg, gg -> ttqq, qq -> ttgg, qq -> ttq'q', q' != q.
The results are given as Laurent expansions in epsilon, the parameter of
dimensional regularization, at a number of m/ECM values spreading the entire
variation range, with m the mass of the top quark and ECM the center-of-mass
energy. We describe the details of our implementation and demonstrate its main
properties: pointwise convergence and efficiency. We also prove the
cancellation of leading divergences after inclusion of the double-virtual and
real-virtual contributions. On a more technical note, we extended the
double-soft current formulae to the case of massive partons.
