Non-resonant and electroweak NNLO correction to the $e^{+}{e}^{-}$ top anti-top threshold

We determine the NNLO electroweak correction to the $e^{+}{e}^{-}\to b\overline{b}{W}^{+}{W}^{-}X$ production cross section near the top-pair production threshold. The calculation includes non-resonant production of the final state as well as electroweak effects in resonant top anti-top pair production with non-relativistic resummation, and elevates the theoretical prediction to NNNLO QCD plus NNLO electroweak accuracy. We then study the impact of the new contributions on the top-pair threshold scan at a future lepton collider.