Top-quark pair production at next-to-next-to-leading order QCD in electron positron collisions

We set up a formalism, within the antenna subtraction framework, for computing the production of a massive quark-antiquark pair in electron positron collisions at next-to-next-to-leading order in the coupling α s of quantum chromodynamics at the differential level. our formalism applies to the calculation of any infrared-safe observable. we apply this set-up to the production of top-quark top antiquark pairs in the continuum. we compute the production cross section and several distributions. we determine, in particular, the top-quark forward-backward asymmetry at order α 2 . our result agrees with previous computations of this observable.