Threshold Resummation for the Production of Four Top Quarks at the LHC.

We compute the total cross section for tt[over ¯]tt[over ¯] production at next-to-leading logarithmic (NLL^{'}) accuracy. This is the first time resummation is performed for a hadron-collider process with four colored particles in the final state. The calculation is matched to the next-to-leading order strong and electroweak corrections. The NLL^{'} corrections enhance the total production rate by 15%. The size of the theoretical error due to scale variation is reduced by more than a factor of 2, bringing the theoretical error significantly below the current experimental uncertainty of the measurement.