Normalization of QCD corrections in top quark decay

Abstract

We discuss the effects of QCD corrections to the on-shell decay $t\to bW$. We resolve the scale ambiguity using the Brodsky-Lepage-Mackenzie scheme, and find that the appropriate coupling constant is ${\alpha }_s^{\overline{MS}}(0.122m_t)$. The largest long distance contribution comes from the definition of the on-shell mass of the top quark. We note that QCD corrections to the electroweak $\rho$ parameter are extremely small when the $\rho$ parameter is expressed in terms of the top quark width.

Comments: 7 pages (LaTeX), TPI-MINN-94/16-T, UMN-TH-1252/94