$\mathcal{O}(\alpha \text{as}\ln m_t^2)$ Non-Universal Corrections to the Decay Rate $\Gamma (Z\to b\bar{b})$

Abstract

The partial decay rate $\Gamma (Z\to b\bar{b})$ is significantly influenced by the mass of the top quark due to electroweak radiative corrections. The leading $\sim m_t^2$ and the next-to-leading contribution $\sim \ln m_t^2$ are known to be numerically of similar size. In this work we calculate the QCD corrections to the logarithmic correction using the heavy top mass expansion. The $\mathcal{O}(\alpha \text{as}\ln m_t^2)$ corrections are of the same order as the QCD corrections to the quadratic top mass term, but of different sign.

Comments: 10 pages, Latex [ uses epsfig.sty, 3 figures not included ] A complete postscript file, including figures, is available via anonymous ftp at ttpux2.physik.uni-karlsruhe.de (129.13.102.139) as /ttp94-14/ttp94-14.ps, Local preprint# TTP94-14