Matrix Element Corrections to Parton Shower Simulations of Heavy Quark   Decay
  Parton showers are accurate for soft and/or collinear emission, but for a good description of the whole of phase space they need to be supplemented by matrix element corrections. In this paper, we discuss matrix element corrections to the decay t->Wb and apply our results to the HERWIG Monte Carlo event generator. The phenomenological results show marked improvement relative to previous versions and agree well with the exact first-order matrix-element calculation. 
Gennaro Corcella (Milano) and Michael H. Seymour (RAL)