O(G ²_μ m ⁴ _t ) electroweak radiative corrections to theZb $\bar b$ vertex

Abstract

The leading heavy-top two-loop corrections to theZb $\bar b$ vertex are determined from a direct evaluation of the corresponding Feynman diagrams in the largem _t limit. The leading one-loop top-mass effect is enhanced by$[{{1 + G_\mu m_t^2 ({{9 - \pi ^2 } \mathord{\left/ {\vphantom {{9 - \pi ^2 } 3}} \right. \kern-\nulldelimiterspace} 3})} \mathord{\left/ {\vphantom {{1 + G_\mu m_t^2 ({{9 - \pi ^2 } \mathord{\left/ {\vphantom {{9 - \pi ^2 } 3}} \right. \kern-\nulldelimiterspace} 3})} {(8\pi ^2 \sqrt 2 )}}} \right. \kern-\nulldelimiterspace} {(8\pi ^2 \sqrt 2 )}}]$. Our calculation confirms a recent result of Barbieri et al..