Electroweak non-resonant corrections to top pair production close to threshold

The production of W⁺W⁻bb^¯ from e⁺e⁻ collisions at energies close to the tt¯ threshold is dominated by the resonant process with a nearly on-shell tt¯ intermediate state. The Wb pairs in the final state can also be reached through the decay of off-shell tops or through background processes containing no or only single top quarks. This non-resonant production starts to contribute at NLO to the W⁺W⁻bb^¯ total cross section in the non-relativistic power-counting v ∼ α_s ∼ √α_EW. The NLO non-resonant corrections presented in this talk represent the non-trivial NLO electroweak corrections to the e⁺e⁻ →W⁺W⁻bb^¯ cross section in the top anti-top resonance region. In contrast to the QCD corrections which have been calculated (almost) up to NNNLO, the parametrically larger NLO electroweak contributions have not been completely known so far, but are mandatory for the required accuracy at a future linear collider. We consider the total cross section of the e⁺e⁻ →W⁺W⁻bb^¯ process and additionally implement cuts on the invariant masses of the W⁺b and W⁻b^¯ pairs.