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 — preprints:1995:ttp95-13 [2016/03/17 11:03] (current) Line 1: Line 1: + ====== TTP95-13 QCD Corrections from Top Quark to Relations ​ between Electroweak Parameters to Order $\as^2$ ====== + + + <​hidden TTP95-13 ​ QCD Corrections from Top Quark to Relations ​ between Electroweak Parameters to Order $\as^2$ > The vacuum polarization functions $\Pi(q^2)$ of charged and neutral + gauge bosons which arise from top and bottom quark loops lead to + ​important shifts in relations between electroweak parameters + which can be measured with ever-increasing precision. The large + mass of the top quark allows approximation of these functions through + the first two terms of an expansion in $M_Z^2/​M_t^2$. + The first three terms of the Taylor series of $\Pi(q^2)$ are + ​evaluated analytically up to order $\as^2$. + The first two are required to derive the approximation,​ the + third can be used to demonstrate the smallness of the neglected terms. + The paper + ​improves earlier results + based on the leading term $\propto G_F M_t^2 \as^2$. + ​Results for the subleading + ​contributions to $\dr$ and the effective mixing angle $\sineff$ are presented. + ​ + |**K.G. Chetyrkin, J.H. Kuehn, M. Steinhauser** ​ | + |** Phys. Rev. Lett. 75 3394-3397 1995  **  | + | {{preprints:​1995:​ttp95-13.pdf|PDF}} {{preprints:​1995:​ttp95-13.ps|PostScript}} [[http://​arxiv.org/​abs/​hep-ph/​9504413|arXiv]] ​  | + | |