Abstract :
The semileptonic decay of the top quark t → bW+ → bl+νl is analyzed in the rest system of the W. The forward-backward asymmetry of the lepton l+ with respect to the heavy quark direction is defined and computed. It is argued that this observable will be an ideal tool to study top quark properties at Tevatron and LHC. Higher order QCD corrections are calculated and their structure is elucidated in some detail.
