We calculate the next-to-next-to-leading-order (NNLO) QCD radiative correction to the pion electromagnetic form factor with large momentum transfer. We explicitly verify the validity of the collinear factorization to two-loop order for this observable and obtain the respective IR-finite two-loop hard-scattering kernel in the closed form. The NNLO QCD correction turns out to be positive and significant. Incorporating this new ingredient of correction, we then make a comprehensive comparison between the finest theoretical predictions and numerous data for both space- and timelike pion form factors. Our phenomenological analysis provides a strong constraint on the second Gegenbauer moment of the pion light-cone distribution amplitude obtained from recent lattice QCD studies.

中文翻译：

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对π介子电磁形状因子的次次次前导 QCD 校正

我们计算了对具有大动量传递的π介子电磁形状因子的次次次次前导阶（NNLO）QCD辐射校正。我们明确验证了该可观测量的共线分解到二环阶的有效性，并获得了相应的封闭形式的红外有限二环硬散射核。 NNLO QCD 校正结果是积极且显着的。结合这种新的校正成分，我们对类空间和类时间π介子形状因子的最佳理论预测和大量数据进行了全面比较。我们的现象学分析对从最近的晶格 QCD 研究中获得的 π 介子光锥分布振幅的第二个 Gegenbauer 矩提供了强有力的约束。