Finite-width effects in top quark production at hadron colliders

Production cross sections for tt̄ and tt̄j events at hadron colliders are calculated, including finite-width effects and off resonance contributions for the entire decay chain, t→bW→blν, for both top quarks. The resulting background rates to a Higgs boson search at the CERN large hadron collider are updated for inclusive H→WW studies and for H→ττ and H→WW decays in weak boson fusion events. The finite-width effects are large, increasing tt̄(j) rates by 20% or more, after typical cuts which are employed for top-background rejection.