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arXiv 0811.1364hep-ph
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对sin^2 theta_{eff} ^{b anti-b}的双圈电弱费米子修正

Two-loop electroweak fermionic corrections to sin^2 theta_{eff}^{b anti-b}

M. Awramik, M. Czakon, A. Freitas, B. A. Kniehl

摘要:

我们首次计算了底夸克的味相关有效弱混合角sin ^2 theta_{eff} ^{b anti-b}的双圈电弱费米子修正。对于缺失的双圈顶点图的评估,采用两种方法,一种基于半数值Bernstein-Tkachov算法,第二种基于大顶夸克质量的渐近展开。基于色散关系的第三种方法用于检查基本回路积分。我们发现,对于小的Higgs玻色子质量值,M_H ~ 100 GeV,修正是相当大的,量级为O(10^{-4})。

英文摘要:

We present the first calculation of the two-loop electroweak fermionic correction to the flavour-dependent effective weak-mixing angle for bottom quarks, sin^2 theta_{eff}^{b anti-b}. For the evaluation of the missing two-loop vertex diagrams, two methods are employed, one based on a semi-numerical Bernstein-Tkachov algorithm and the second on asymptotic expansions in the large top-quark mass. A third method based on dispersion relations is used for checking the basic loop integrals. We find that for small Higgs-boson mass values, M_H ~ 100 GeV, the correction is sizable, of order O(10^{-4}).

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