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arXiv 1309.2153hep-lathep-ph
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强子真空极化对μ子反常磁矩的拟合检验

Tests of hadronic vacuum polarization fits for the muon anomalous magnetic moment

Maarten Golterman, Kim Maltman, Santiago Peris

摘要:

利用OPAL实验的强子τ衰变的实验光谱数据,辅以一个现象学上成功的参数化的高S区的数据不包括,我们构建了一个物理约束模型的同位旋一矢量通道极化函数。有了这样一个作为欧几里得动量Q^2函数的模型,我们就可以探索与强子电磁流极化函数的晶格数据的Q^2依赖性拟合相关的系统误差,这些数据曾被用来计算强子对μ子反常磁矩的首阶贡献a_μ^HLO。与最近文献中的说法相反,我们发现,考虑到目前在低Q^2下真空极化的测定缺乏精确度,用目前的晶格数据,这个量的最终误差不可能达到百分之几的数量级。我们还发现,使用基于矢量介子优势的拟合函数来拟合真空极化是不可靠的,因为a_μ^HLO上的拟合误差通常远小于从拟合获得的值与精确模型值之间的差。已知收敛到真实真空极化的Pade近似序列的使用似乎代表了一种更有前途的方法。

英文摘要:

Using experimental spectral data for hadronic tau decays from the OPAL experiment, supplemented by a phenomenologically successful parameterization for the high-s region not covered by the data, we construct a physically constrained model of the isospin-one vector-channel polarization function. Having such a model as a function of Euclidean momentum Q^2 allows us to explore the systematic error associated with fits to the Q^2 dependence of lattice data for the hadronic electromagnetic current polarization function which have been used in attempts to compute the leading order hadronic contribution, a_μ^HLO, to the muon anomalous magnetic moment. In contrast to recent claims made in the literature, we find that a final error in this quantity of the order of a few percent does not appear possible with current lattice data, given the present lack of precision in the determination of the vacuum polarization at low Q^2. We also find that fits to the vacuum polarization using fit functions based on Vector Meson Dominance are unreliable, in that the fit error on a_μ^HLO is typically much smaller than the difference between the value obtained from the fit and the exact model value. The use of a sequence of Pade approximants known to converge to the true vacuum polarization appears to represent a more promising approach.

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