High-order corrections and subleading logarithms for top quark   production
  We derive high-order threshold corrections for top quark production in hadronic collisions from resummation calculations. We present analytical expressions for the cross section through next-to-next-to-next-to-next-to-leading order (N^4LO) and next-to-next-to-leading logarithmic accuracy. Special attention is paid to the role of subleading logarithms and how they relate to the convergence of the perturbation series and differences between various resummation prescriptions. It is shown that care must be taken to avoid unphysical terms in the expansions. Numerical results are presented for top quark production at the Tevatron. We find sizeable increases to the total cross section and differential distributions and a dramatic reduction of the factorization scale dependence relative to next-to-leading order. 
Nikolaos Kidonakis