arXiv 0812.03232008-12-01hep-ph

基于局部对偶QCD求和规则的π介子形状因子

Pion form factor from local-duality QCD sum rule

Wolfgang Lucha, Dmitri Melikhov

备注：: Talk given at the 8-th Conference "Quark Confinement and the Hadron Spectrum", Mainz, Germany, 1-6 September 2008
发表信息：: PoS Confinement8:072,2008

摘要：

本文给出了在局部对偶三点求和规则（无限Borel参数极限下的Borel求和规则）下得到的π介子弹性形状因子的最新结果。我们的分析包括了O（1）和O（α s）的贡献，因此适用于广泛的类空动量转移。我们的结果以基本上与模型无关的方式表明，在渐近大动量转移时提供次超前1/Q^4幂修正的O（1）项在Q^2 \le 20 GeV^2区域贡献了超过一半的π形状因子。为了探讨形状因子的局部对偶求和规则的准确性，我们应用完全相同的程序来提取量子力学势模型中的形状因子。将该模型中已知的精确形状因子与求和规则计算的结果进行比较，探讨了该方法的系统误差。在我们的示例中，发现该误差在10- 20%的水平。我们期望在QCD中由局域对偶求和规则得到的形状因子也有类似的系统误差。

英文摘要：

We present our recent results for the pion elastic form factor [1] obtained within a local-duality three-point sum rule (a Borel sum rule in the limit of an infinite Borel parameter). Our analysis includes the O(1) and O(α_s) contributions and is therefore applicable in a broad range of spacelike momentum transfers. Our results demonstrate in essentially model-independent way that the O(1) term, which provides the subleading 1/Q^4 power correction at asymptotically large momentum transfers, contributes more than half of the pion form factor in the region Q^2 \le 20 GeV^2. To probe the accuracy of local-duality sum rules for form factors, we apply precisely the same procedures to extract the form factor in a quantum-mechanical potential model. Comparison of the exact form factor known in this model with the result of the sum-rule calculation gives a probe of the systematic error of the method. In our example this error is found to be at the level of 10-20%. We expect similar systematic errors for form factors obtained from local-duality sum rules in QCD.

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英文摘要：

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