Leading electroweak radiative corrections tot→W++b

By using the Goldstone-boson equivalence theorem, the leading electroweak radiative corrections to the tree-level process $t\to W^{+}b$ are obtained in three different limits: (i) $m_H>m_t>M_W$, (ii) $m_H=m_t>M_W$, and (iii) $m_t>m_H>M_W$. Recently, several groups have done the same calculation without using the equivalence theorem approach and obtained slightly different results. We compare our results with these previous works.