Electroweak radiative corrections to the top quark decay

The top quark, once produced, should be an important window to the electroweak symmetry breaking sector. We compute electroweak radiative corrections to the decay processt→b+W ⁺ in order to extract information on the Higgs sector and to fix the background in searches for a possible new physics contribution. The large Yukawa coupling of the top quark induces a new form factor through vertex corrections and causes discrepancy from the tree-level longitudinalW-boson production fraction, but the effect is of order 1% or less form _H<1 TeV.