Zhong-Hua Zhao, Hui-Yun Cao, Hai-Qing Zhou ∗ School of Physics, Southeast University, NanJing 211189, China (Dated: September 18, 2020) In this work, the two-photon-exchange (TPE) effects in e+e− → π+π− at small √s are discussed within a hadronic model. In the limit me → 0, the TPE contribution to the amplitude can be described by one scalar function c (2γ) 1 . The ratio between this function and the corresponding contribution in one-photon exchange c (1γ) 1 reflects all the information of the TPE corrections. The numerical results on this ratio are presented and an artificial function is used to fit the numerical results. The latter can be used conveniently in the further experimental data analysis. The numerical results show the asymmetry of the differential cross sections in e+e− → π+π− is about −4% at √s ∼ 0.7 GeV.

中文翻译：

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小 s 时 e+e−→π+π− 中的双光子交换效应

赵忠华, 曹慧云, 周海清 ∗ 东南大学物理学院, 南京 211189 (Dated: September 18, 2020) 在这项工作中，电子中的双光子交换 (TPE) 效应+e− → π+π− 在小 √s 处在强子模型中讨论。在极限 me → 0 中，TPE 对振幅的贡献可以用一个标量函数 c (2γ) 1 来描述。该函数与单光子交换 c (1γ) 1 中的相应贡献之间的比率反映了 TPE 校正的所有信息。给出了该比率的数值结果，并使用人工函数来拟合数值结果。后者可以方便地用于进一步的实验数据分析。数值结果表明，在 √s ∼ 0.7 GeV 处，e+e− → π+π− 中微分截面的不对称性约为 -4%。