On final-state effects in tt̄ production at threshold

We apply the relativistic Bethe-Salpeter formalism to the calculation of final-state effects in the production of a tt̄ pair at threshold. We find that final-state rescattering does not affect the momentum distribution of the tt̄ pair to lowest order in the strong coupling constant. This result correctly extends earlier results based on the non-relativistic Lippmann-Schwinger equation.