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Next-to-Next-to-Leading-Order QCD Prediction for the Photon-Pion Form Factor
Jing Gao1, Tobias Huber2, Yao Ji2
1School of Physics, Nankai University, Weijin Road 94, 300071 Tianjin, China; Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Strasse 3, 57068 Siegen, Germany; Institute of High Energy Physics, CAS, P.O. Box 918(4), Beijing 100049, China; and School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China.
Abstract:
We accomplish the complete two-loop computation of the leading-twist contribution to the photon-pion transition form factor γγ^{*}→π^{0} by applying the hard-collinear factorization theorem together with modern multiloop techniques. The resulting predictions for the form factor indicate that the two-loop perturbative correction is numerically important. We also demonstrate that our results will play a key role in disentangling various models of the twist-two pion distribution amplitude thanks to the envisaged precision at Belle II.
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