On June 5, the team led by Prof. Yu-Ming Wang from the School of Physics of Nankai University made a breakthrough in the research field of perturbation field theory and hadron structure. Their findings were published in Physical Review Letters, a top academic journal in the field of physics, under the title of “Next-to-Next-to-Leading-Order QCD Prediction for the Pion Form Factor”.

Yu-Ming Wang together with the two doctoral students Bo-Xuan and Hui-Xin Yu in his group, colloborated closely with Prof. Yao Ji from the Chinese University of Hong Kong (Shenzhen), Prof. Jian Wang from Shandong University, and an associate researcher Ye-Fan Wang from Nanjing Normal University. This research work innovatively combined effective quantum field theory methods with modern multi-loop computational‌ techniques, and achieved for the first time a rigorous computation‌ of the pion electromagnetic form factor at two loops. This resolved the long-standing dilemma of slow progress in theoretical research since the one-loop results were obtained in 1981 [Richard Field, Rajan Gupta, Steve Otto, Lee Chang (Prof. Li Zhang from Tsinghua University), Nucl. Phys. B 186 (1981) 429]. In addition, this study further indicates that the comparison between the newly obtained two-loop results and the future EIC experimental data will significantly improve the extraction accuracy of the shape parameters for the pion light-cone distribution amplitude (LCDA)‌, which has profound scientific significance for an in-depth exploration of the intrinsic structure of hadron bound state systems as well as strong interaction dynamics.

Typical double-loop Feynman diagram

Shape parameter a4 of the pion distribution amplitude

Read the paper at https://link.aps.org/doi/10.1103/yx51-lc3q

（Edited and translated by Nankai News Team.)