Effects of Finite Top Lifetime at the Top-Antitop Threshold
  In this talk electroweak corrections related to the finite top quark lifetime to the total top pair threshold e+e- cross section at NNLL order are discussed. We include the absorptive parts in electroweak matching conditions of the NRQCD operators related to the top decay and use the optical theorem. Gauge invariance is maintained. The corrections lead to ultraviolet phase space divergences and NLL mixing effects. The corrections can amount to several percent and are phenomenologically relevant. 
A. H. Hoang, C. J. Reisser (Munich, Max Planck Inst.)