Two-loop QCD corrections to top quark width Original Research Article

We present O(αs2) corrections to the decay t → bW in the limit of a very large top quark mass, mt ⪢ mW. We find that the O(αs2) effects decrease the top quark decay width Γt by about 2%: Γt = Γ0 (1 − 0.8αt (mt) − 1.7αs2). The complete corrections are smaller by about 24% than their estimate based on the BLM effects O(αs2). We explain how to compute a new type of diagrams which contribute to Γ(t → bW) at the O(αs2) level.