Infrared Corrections to the Top Quark Width
  We present a nonperturbative analysis of the top quark propagator using the Schwinger Dyson equation in the ladder approximation including both the electroweak as well as the infrared QCD effects.   We find that the infrared effects are negligible only for top mass larger than about 250 GeV. 
Pankaj Jain, Douglas W. McKay and Herman J. Munczek