摘要：

The nucleon constitutes most of the visible matter in the universe, however its fundament structure has not been completely understood yet. Precise measurements of nucleon electromagnetic form factors are of crucial importance to reveal its complicated structure. So far, experimental data for the neutron is rare in the time-like regime. In this talk we present new results for the Born cross section and the effective form factor of the neutron at the center-of-mass energies between 2.0 and 3.08 GeV, using 18 data sets corresponding to an integrated luminosity of 647.9 pb-1 from electron-positron annihilation reactions collected at the BESIII experiment. Our results improve the statistics on the neutron form factor by more than a factor of 60 over previous measurements, distinctly clarifying the photon-nucleon interaction puzzle persistent for over 20 years. In addition, the electromagnetic form factor of the neutron shows an oscillating behavior similar to that of the proton.

报告人介绍：

胡继峰：2011年从中国科学院大学获理学博士学位，随后分别在德国Giessen大学、意大利都灵大学、上海交通大学从事博士后研究工作。自2020年在华南师范大学量子物质研究院任特聘研究员。2016年以来依托BESIII实验研究核子电磁结构，作为主要贡献者之一精确测量了中子类时电磁形状因子。该工作取得了目前为止最精确的实验结果，澄清了存在二十余年的光子-中子耦合强于光子-质子耦合之谜，并揭示了中子电磁形状因子随偶极定律振荡的现象。

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