QCD corrections to t r arrow W sup + + b

The {ital O}({alpha}{sub {ital s}}) QCD corrections to the process {ital t}{r arrow}{ital W}{sup +}{ital b} are calculated in the standard model for a heavy top quark. For {ital m}{sub {ital W}}/{ital M}{sub {ital t}}{lt}0.8, the corrections reduce the partial width by 10% relative to the tree-level result. This reduction of the top-quark width enhances the signal for {ital t{bar t}} bound-state resonances near threshold in {ital e}{sup +}{ital e{minus}} collisions, studied recently by Strassler and Peskin.