⚛️ high-energy experiments

Measurement of Branching Fraction and Transition Magnetic Moment of the Hyperon Dalitz Decay $\Sigma^0 \rightarrow \Lambda e^+e^-$

利用来自 BESIII 探测器的 100 亿个 $J/\psi$ 事件样本，本研究报告了首次对 Dalitz 衰变 $\Sigma^0 \rightarrow \Lambda e^+e^-$ 的实验观测，测得其分支比为 $(6.34 \pm 0.25_{\rm stat.} \pm 0.23_{\rm syst.}) \times 10^{-3}$ ，并确定其跃迁磁矩为 $(1.74 \pm 0.03_{\rm stat.} \pm 0.09_{\rm syst.})\,\mu_N$ ，其中分支比结果与之前的理论预测存在 $2\sigma$ 的差异。

原作者： BESIII Collaboration, M. Ablikim (collapse list), M. N. Achasov (collapse list), P. Adlarson (collapse list), X. C. Ai (collapse list), R. Aliberti (collapse list), A. Amoroso (collapse list), Q. An (BESIII Collaboration, M. Ablikim (collapse list), M. N. Achasov (collapse list), P. Adlarson (collapse list), X. C. Ai (collapse list), R. Aliberti (collapse list), A. Amoroso (collapse list), Q. An (collapse list), Y. Bai (collapse list), O. Bakina (collapse list), Y. Ban (collapse list), H. -R. Bao (collapse list), V. Batozskaya (collapse list), K. Begzsuren (collapse list), N. Berger (collapse list), M. Berlowski (collapse list), M. B. Bertani (collapse list), D. Bettoni (collapse list), F. Bianchi (collapse list), E. Bianco (collapse list), A. Bortone (collapse list), I. Boyko (collapse list), R. A. Briere (collapse list), A. Brueggemann (collapse list), H. Cai (collapse list), M. H. Cai (collapse list), X. Cai (collapse list), A. Calcaterra (collapse list), G. F. Cao (collapse list), N. Cao (collapse list), S. A. Cetin (collapse list), X. Y. Chai (collapse list), J. F. Chang (collapse list), T. T. Chang (collapse list), G. R. Che (collapse list), Y. Z. Che (collapse list), C. H. Chen (collapse list), Chao Chen (collapse list), G. Chen (collapse list), H. S. Chen (collapse list), H. Y. Chen (collapse list), M. L. Chen (collapse list), S. J. Chen (collapse list), S. M. Chen (collapse list), T. Chen (collapse list), X. R. Chen (collapse list), X. T. Chen (collapse list), X. Y. Chen (collapse list), Y. B. Chen (collapse list), Y. Q. Chen (collapse list), Z. K. Chen (collapse list), J. C. Cheng (collapse list), L. N. Cheng (collapse list), S. K. Choi (collapse list), X. Chu (collapse list), G. Cibinetto (collapse list), F. Cossio (collapse list), J. Cottee-Meldrum (collapse list), H. L. Dai (collapse list), J. P. Dai (collapse list), X. C. Dai (collapse list), A. Dbeyssi (collapse list), R. E. de Boer (collapse list), D. Dedovich (collapse list), C. Q. Deng (collapse list), Z. Y. Deng (collapse list), A. Denig (collapse list), I. Denisenko (collapse list), M. Destefanis (collapse list), F. De Mori (collapse list), X. X. Ding (collapse list), Y. Ding (collapse list), Y. X. Ding (collapse list), J. Dong (collapse list), L. Y. Dong (collapse list), M. Y. Dong (collapse list), X. Dong (collapse list), M. C. Du (collapse list), S. X. Du (collapse list), S. X. Du (collapse list), X. L. Du (collapse list), Y. Y. Duan (collapse list), Z. H. Duan (collapse list), P. Egorov (collapse list), G. F. Fan (collapse list), J. J. Fan (collapse list), Y. H. Fan (collapse list), J. Fang (collapse list), J. Fang (collapse list), S. S. Fang (collapse list), W. X. Fang (collapse list), Y. Q. Fang (collapse list), L. Fava (collapse list), F. Feldbauer (collapse list), G. Felici (collapse list), C. Q. Feng (collapse list), J. H. Feng (collapse list), L. Feng (collapse list), Q. X. Feng (collapse list), Y. T. Feng (collapse list), M. Fritsch (collapse list), C. D. Fu (collapse list), J. L. Fu (collapse list), Y. W. Fu (collapse list), H. Gao (collapse list), Y. Gao (collapse list), Y. N. Gao (collapse list), Y. N. Gao (collapse list), Y. Y. Gao (collapse list), Z. Gao (collapse list), S. Garbolino (collapse list), I. Garzia (collapse list), L. Ge (collapse list), P. T. Ge (collapse list), Z. W. Ge (collapse list), C. Geng (collapse list), E. M. Gersabeck (collapse list), A. Gilman (collapse list), K. Goetzen (collapse list), J. D. Gong (collapse list), L. Gong (collapse list), W. X. Gong (collapse list), W. Gradl (collapse list), S. Gramigna (collapse list), M. Greco (collapse list), M. D. Gu (collapse list), M. H. Gu (collapse list), C. Y. Guan (collapse list), A. Q. Guo (collapse list), J. N. Guo (collapse list), L. B. Guo (collapse list), M. J. Guo (collapse list), R. P. Guo (collapse list), X. Guo (collapse list), Y. P. Guo (collapse list), A. Guskov (collapse list), J. Gutierrez (collapse list), T. T. Han (collapse list), F. Hanisch (collapse list), K. D. Hao (collapse list), X. Q. Hao (collapse list), F. A. Harris (collapse list), C. Z. He (collapse list), K. L. He (collapse list), F. H. Heinsius (collapse list), C. H. Heinz (collapse list), Y. K. Heng (collapse list), C. Herold (collapse list), P. C. Hong (collapse list), G. Y. Hou (collapse list), X. T. Hou (collapse list), Y. R. Hou (collapse list), Z. L. Hou (collapse list), H. M. Hu (collapse list), J. F. Hu (collapse list), Q. P. Hu (collapse list), S. L. Hu (collapse list), T. Hu (collapse list), Y. Hu (collapse list), Z. M. Hu (collapse list), G. S. Huang (collapse list), K. X. Huang (collapse list), L. Q. Huang (collapse list), P. Huang (collapse list), X. T. Huang (collapse list), Y. P. Huang (collapse list), Y. S. Huang (collapse list), T. Hussain (collapse list), N. Hüsken (collapse list), N. in der Wiesche (collapse list), J. Jackson (collapse list), Q. Ji (collapse list), Q. P. Ji (collapse list), W. Ji (collapse list), X. B. Ji (collapse list), X. L. Ji (collapse list), X. Q. Jia (collapse list), Z. K. Jia (collapse list), D. Jiang (collapse list), H. B. Jiang (collapse list), P. C. Jiang (collapse list), S. J. Jiang (collapse list), X. S. Jiang (collapse list), Y. Jiang (collapse list), J. B. Jiao (collapse list), J. K. Jiao (collapse list), Z. Jiao (collapse list), S. Jin (collapse list), Y. Jin (collapse list), M. Q. Jing (collapse list), X. M. Jing (collapse list), T. Johansson (collapse list), S. Kabana (collapse list), N. Kalantar-Nayestanaki (collapse list), X. L. Kang (collapse list), X. S. Kang (collapse list), M. Kavatsyuk (collapse list), B. C. Ke (collapse list), V. Khachatryan (collapse list), A. Khoukaz (collapse list), O. B. Kolcu (collapse list), B. Kopf (collapse list), L. Kröger (collapse list), M. Kuessner (collapse list), X. Kui (collapse list), N. Kumar (collapse list), A. Kupsc (collapse list), W. Kühn (collapse list), Q. Lan (collapse list), W. N. Lan (collapse list), T. T. Lei (collapse list), M. Lellmann (collapse list), T. Lenz (collapse list), C. Li (collapse list), C. Li (collapse list), C. H. Li (collapse list), C. K. Li (collapse list), D. M. Li (collapse list), F. Li (collapse list), G. Li (collapse list), H. B. Li (collapse list), H. J. Li (collapse list), H. L. Li (collapse list), H. N. Li (collapse list), Hui Li (collapse list), J. R. Li (collapse list), J. S. Li (collapse list), J. W. Li (collapse list), K. Li (collapse list), K. L. Li (collapse list), L. J. Li (collapse list), Lei Li (collapse list), M. H. Li (collapse list), M. R. Li (collapse list), P. L. Li (collapse list), P. R. Li (collapse list), Q. M. Li (collapse list), Q. X. Li (collapse list), R. Li (collapse list), S. X. Li (collapse list), Shanshan Li (collapse list), T. Li (collapse list), T. Y. Li (collapse list), W. D. Li (collapse list), W. G. Li (collapse list), X. Li (collapse list), X. H. Li (collapse list), X. K. Li (collapse list), X. L. Li (collapse list), X. Y. Li (collapse list), X. Z. Li (collapse list), Y. Li (collapse list), Y. G. Li (collapse list), Y. P. Li (collapse list), Z. H. Li (collapse list), Z. J. Li (collapse list), Z. X. Li (collapse list), Z. Y. Li (collapse list), C. Liang (collapse list), H. Liang (collapse list), Y. F. Liang (collapse list), Y. T. Liang (collapse list), G. R. Liao (collapse list), L. B. Liao (collapse list), M. H. Liao (collapse list), Y. P. Liao (collapse list), J. Libby (collapse list), A. Limphirat (collapse list), D. X. Lin (collapse list), L. Q. Lin (collapse list), T. Lin (collapse list), B. J. Liu (collapse list), B. X. Liu (collapse list), C. X. Liu (collapse list), F. Liu (collapse list), F. H. Liu (collapse list), Feng Liu (collapse list), G. M. Liu (collapse list), H. Liu (collapse list), H. B. Liu (collapse list), H. H. Liu (collapse list), H. M. Liu (collapse list), Huihui Liu (collapse list), J. B. Liu (collapse list), J. J. Liu (collapse list), K. Liu (collapse list), K. Liu (collapse list), K. Y. Liu (collapse list), Ke Liu (collapse list), L. Liu (collapse list), L. C. Liu (collapse list), Lu Liu (collapse list), M. H. Liu (collapse list), P. L. Liu (collapse list), Q. Liu (collapse list), S. B. Liu (collapse list), W. M. Liu (collapse list), W. T. Liu (collapse list), X. Liu (collapse list), X. K. Liu (collapse list), X. L. Liu (collapse list), X. Y. Liu (collapse list), Y. Liu (collapse list), Y. Liu (collapse list), Y. B. Liu (collapse list), Z. A. Liu (collapse list), Z. D. Liu (collapse list), Z. Q. Liu (collapse list), Z. Y. Liu (collapse list), X. C. Lou (collapse list), H. J. Lu (collapse list), J. G. Lu (collapse list), X. L. Lu (collapse list), Y. Lu (collapse list), Y. H. Lu (collapse list), Y. P. Lu (collapse list), Z. H. Lu (collapse list), C. L. Luo (collapse list), J. R. Luo (collapse list), J. S. Luo (collapse list), M. X. Luo (collapse list), T. Luo (collapse list), X. L. Luo (collapse list), Z. Y. Lv (collapse list), X. R. Lyu (collapse list), Y. F. Lyu (collapse list), Y. H. Lyu (collapse list), F. C. Ma (collapse list), H. L. Ma (collapse list), Heng Ma (collapse list), J. L. Ma (collapse list), L. L. Ma (collapse list), L. R. Ma (collapse list), Q. M. Ma (collapse list), R. Q. Ma (collapse list), R. Y. Ma (collapse list), T. Ma (collapse list), X. T. Ma (collapse list), X. Y. Ma (collapse list), Y. M. Ma (collapse list), F. E. Maas (collapse list), I. MacKay (collapse list), M. Maggiora (collapse list), S. Malde (collapse list), Q. A. Malik (collapse list), H. X. Mao (collapse list), Y. J. Mao (collapse list), Z. P. Mao (collapse list), S. Marcello (collapse list), A. Marshall (collapse list), F. M. Melendi (collapse list), Y. H. Meng (collapse list), Z. X. Meng (collapse list), G. Mezzadri (collapse list), H. Miao (collapse list), T. J. Min (collapse list), R. E. Mitchell (collapse list), X. H. Mo (collapse list), B. Moses (collapse list), N. Yu. Muchnoi (collapse list), J. Muskalla (collapse list), Y. Nefedov (collapse list), F. Nerling (collapse list), H. Neuwirth (collapse list), Z. Ning (collapse list), S. Nisar (collapse list), Q. L. Niu (collapse list), W. D. Niu (collapse list), Y. Niu (collapse list), C. Normand (collapse list), S. L. Olsen (collapse list), Q. Ouyang (collapse list), S. Pacetti (collapse list), X. Pan (collapse list), Y. Pan (collapse list), A. Pathak (collapse list), Y. P. Pei (collapse list), M. Pelizaeus (collapse list), H. P. Peng (collapse list), X. J. Peng (collapse list), Y. Y. Peng (collapse list), K. Peters (collapse list), K. Petridis (collapse list), J. L. Ping (collapse list), R. G. Ping (collapse list), S. Plura (collapse list), V. Prasad (collapse list), F. Z. Qi (collapse list), H. R. Qi (collapse list), M. Qi (collapse list), S. Qian (collapse list), W. B. Qian (collapse list), C. F. Qiao (collapse list), J. H. Qiao (collapse list), J. J. Qin (collapse list), J. L. Qin (collapse list), L. Q. Qin (collapse list), L. Y. Qin (collapse list), P. B. Qin (collapse list), X. P. Qin (collapse list), X. S. Qin (collapse list), Z. H. Qin (collapse list), J. F. Qiu (collapse list), Z. H. Qu (collapse list), J. Rademacker (collapse list), C. F. Redmer (collapse list), A. Rivetti (collapse list), M. Rolo (collapse list), G. Rong (collapse list), S. S. Rong (collapse list), F. Rosini (collapse list), Ch. Rosner (collapse list), M. Q. Ruan (collapse list), N. Salone (collapse list), A. Sarantsev (collapse list), Y. Schelhaas (collapse list), K. Schoenning (collapse list), M. Scodeggio (collapse list), W. Shan (collapse list), X. Y. Shan (collapse list), Z. J. Shang (collapse list), J. F. Shangguan (collapse list), L. G. Shao (collapse list), M. Shao (collapse list), C. P. Shen (collapse list), H. F. Shen (collapse list), W. H. Shen (collapse list), X. Y. Shen (collapse list), B. A. Shi (collapse list), H. Shi (collapse list), J. L. Shi (collapse list), J. Y. Shi (collapse list), S. Y. Shi (collapse list), X. Shi (collapse list), H. L. Song (collapse list), J. J. Song (collapse list), M. H. Song (collapse list), T. Z. Song (collapse list), W. M. Song (collapse list), Y. X. Song (collapse list), Zirong Song (collapse list), S. Sosio (collapse list), S. Spataro (collapse list), S. Stansilaus (collapse list), F. Stieler (collapse list), S. S Su (collapse list), G. B. Sun (collapse list), G. X. Sun (collapse list), H. Sun (collapse list), H. K. Sun (collapse list), J. F. Sun (collapse list), K. Sun (collapse list), L. Sun (collapse list), R. Sun (collapse list), S. S. Sun (collapse list), T. Sun (collapse list), W. Y. Sun (collapse list), Y. C. Sun (collapse list), Y. H. Sun (collapse list), Y. J. Sun (collapse list), Y. Z. Sun (collapse list), Z. Q. Sun (collapse list), Z. T. Sun (collapse list), C. J. Tang (collapse list), G. Y. Tang (collapse list), J. Tang (collapse list), J. J. Tang (collapse list), L. F. Tang (collapse list), Y. A. Tang (collapse list), L. Y. Tao (collapse list), M. Tat (collapse list), J. X. Teng (collapse list), J. Y. Tian (collapse list), W. H. Tian (collapse list), Y. Tian (collapse list), Z. F. Tian (collapse list), I. Uman (collapse list), B. Wang (collapse list), B. Wang (collapse list), Bo Wang (collapse list), C. Wang (collapse list), C. Wang (collapse list), Cong Wang (collapse list), D. Y. Wang (collapse list), H. J. Wang (collapse list), J. Wang (collapse list), J. J. Wang (collapse list), J. P. Wang (collapse list), K. Wang (collapse list), L. L. Wang (collapse list), L. W. Wang (collapse list), M. Wang (collapse list), M. Wang (collapse list), N. Y. Wang (collapse list), S. Wang (collapse list), Shun Wang (collapse list), T. Wang (collapse list), T. J. Wang (collapse list), W. Wang (collapse list), W. P. Wang (collapse list), X. Wang (collapse list), X. F. Wang (collapse list), X. L. Wang (collapse list), X. N. Wang (collapse list), Xin Wang (collapse list), Y. Wang (collapse list), Y. D. Wang (collapse list), Y. F. Wang (collapse list), Y. H. Wang (collapse list), Y. J. Wang (collapse list), Y. L. Wang (collapse list), Y. N. Wang (collapse list), Y. N. Wang (collapse list), Yaqian Wang (collapse list), Yi Wang (collapse list), Yuan Wang (collapse list), Z. Wang (collapse list), Z. Wang (collapse list), Z. L. Wang (collapse list), Z. Q. Wang (collapse list), Z. Y. Wang (collapse list), Ziyi Wang (collapse list), D. Wei (collapse list), D. H. Wei (collapse list), H. R. Wei (collapse list), F. Weidner (collapse list), S. P. Wen (collapse list), U. Wiedner (collapse list), G. Wilkinson (collapse list), M. Wolke (collapse list), J. F. Wu (collapse list), L. H. Wu (collapse list), L. J. Wu (collapse list), L. J. Wu (collapse list), Lianjie Wu (collapse list), S. G. Wu (collapse list), S. M. Wu (collapse list), X. Wu (collapse list), Y. J. Wu (collapse list), Z. Wu (collapse list), L. Xia (collapse list), B. H. Xiang (collapse list), D. Xiao (collapse list), G. Y. Xiao (collapse list), H. Xiao (collapse list), Y. L. Xiao (collapse list), Z. J. Xiao (collapse list), C. Xie (collapse list), K. J. Xie (collapse list), Y. Xie (collapse list), Y. G. Xie (collapse list), Y. H. Xie (collapse list), Z. P. Xie (collapse list), T. Y. Xing (collapse list), C. J. Xu (collapse list), G. F. Xu (collapse list), H. Y. Xu (collapse list), M. Xu (collapse list), Q. J. Xu (collapse list), Q. N. Xu (collapse list), T. D. Xu (collapse list), X. P. Xu (collapse list), Y. Xu (collapse list), Y. C. Xu (collapse list), Z. S. Xu (collapse list), F. Yan (collapse list), L. Yan (collapse list), W. B. Yan (collapse list), W. C. Yan (collapse list), W. H. Yan (collapse list), W. P. Yan (collapse list), X. Q. Yan (collapse list), H. J. Yang (collapse list), H. L. Yang (collapse list), H. X. Yang (collapse list), J. H. Yang (collapse list), R. J. Yang (collapse list), Y. Yang (collapse list), Y. H. Yang (collapse list), Y. Q. Yang (collapse list), Y. Z. Yang (collapse list), Z. P. Yao (collapse list), M. Ye (collapse list), M. H. Ye (collapse list), Z. J. Ye (collapse list), Junhao Yin (collapse list), Z. Y. You (collapse list), B. X. Yu (collapse list), C. X. Yu (collapse list), G. Yu (collapse list), J. S. Yu (collapse list), L. W. Yu (collapse list), T. Yu (collapse list), X. D. Yu (collapse list), Y. C. Yu (collapse list), Y. C. Yu (collapse list), C. Z. Yuan (collapse list), H. Yuan (collapse list), J. Yuan (collapse list), J. Yuan (collapse list), L. Yuan (collapse list), M. K. Yuan (collapse list), S. H. Yuan (collapse list), Y. Yuan (collapse list), C. X. Yue (collapse list), Ying Yue (collapse list), A. A. Zafar (collapse list), F. R. Zeng (collapse list), S. H. Zeng (collapse list), X. Zeng (collapse list), Yujie Zeng (collapse list), Y. J. Zeng (collapse list), Y. C. Zhai (collapse list), Y. H. Zhan (collapse list), Shunan Zhang (collapse list), B. L. Zhang (collapse list), B. X. Zhang (collapse list), D. H. Zhang (collapse list), G. Y. Zhang (collapse list), G. Y. Zhang (collapse list), H. Zhang (collapse list), H. Zhang (collapse list), H. C. Zhang (collapse list), H. H. Zhang (collapse list), H. Q. Zhang (collapse list), H. R. Zhang (collapse list), H. Y. Zhang (collapse list), J. Zhang (collapse list), J. J. Zhang (collapse list), J. L. Zhang (collapse list), J. Q. Zhang (collapse list), J. S. Zhang (collapse list), J. W. Zhang (collapse list), J. X. Zhang (collapse list), J. Y. Zhang (collapse list), J. Z. Zhang (collapse list), Jianyu Zhang (collapse list), L. M. Zhang (collapse list), Lei Zhang (collapse list), N. Zhang (collapse list), P. Zhang (collapse list), Q. Zhang (collapse list), Q. Y. Zhang (collapse list), R. Y. Zhang (collapse list), S. H. Zhang (collapse list), Shulei Zhang (collapse list), X. M. Zhang (collapse list), X. Y. Zhang (collapse list), Y. Zhang (collapse list), Y. Zhang (collapse list), Y. T. Zhang (collapse list), Y. H. Zhang (collapse list), Y. P. Zhang (collapse list), Z. D. Zhang (collapse list), Z. H. Zhang (collapse list), Z. L. Zhang (collapse list), Z. L. Zhang (collapse list), Z. X. Zhang (collapse list), Z. Y. Zhang (collapse list), Z. Y. Zhang (collapse list), Z. Z. Zhang (collapse list), Zh. Zh. Zhang (collapse list), G. Zhao (collapse list), J. Y. Zhao (collapse list), J. Z. Zhao (collapse list), L. Zhao (collapse list), L. Zhao (collapse list), M. G. Zhao (collapse list), S. J. Zhao (collapse list), Y. B. Zhao (collapse list), Y. L. Zhao (collapse list), Y. X. Zhao (collapse list), Z. G. Zhao (collapse list), A. Zhemchugov (collapse list), B. Zheng (collapse list), B. M. Zheng (collapse list), J. P. Zheng (collapse list), W. J. Zheng (collapse list), X. R. Zheng (collapse list), Y. H. Zheng (collapse list), B. Zhong (collapse list), C. Zhong (collapse list), H. Zhou (collapse list), J. Q. Zhou (collapse list), S. Zhou (collapse list), X. Zhou (collapse list), X. K. Zhou (collapse list), X. R. Zhou (collapse list), X. Y. Zhou (collapse list), Y. X. Zhou (collapse list), Y. Z. Zhou (collapse list), A. N. Zhu (collapse list), J. Zhu (collapse list), K. Zhu (collapse list), K. J. Zhu (collapse list), K. S. Zhu (collapse list), L. Zhu (collapse list), L. X. Zhu (collapse list), S. H. Zhu (collapse list), T. J. Zhu (collapse list), W. D. Zhu (collapse list), W. J. Zhu (collapse list), W. Z. Zhu (collapse list), Y. C. Zhu (collapse list), Z. A. Zhu (collapse list), X. Y. Zhuang (collapse list), J. H. Zou (collapse list), J. Zu (collapse list)

发布于 2026-08-18

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原作者： BESIII Collaboration, M. Ablikim (collapse list), M. N. Achasov (collapse list), P. Adlarson (collapse list), X. C. Ai (collapse list), R. Aliberti (collapse list), A. Amoroso (collapse list), Q. An (collapse list), Y. Bai (collapse list), O. Bakina (collapse list), Y. Ban (collapse list), H. -R. Bao (collapse list), V. Batozskaya (collapse list), K. Begzsuren (collapse list), N. Berger (collapse list), M. Berlowski (collapse list), M. B. Bertani (collapse list), D. Bettoni (collapse list), F. Bianchi (collapse list), E. Bianco (collapse list), A. Bortone (collapse list), I. Boyko (collapse list), R. A. Briere (collapse list), A. Brueggemann (collapse list), H. Cai (collapse list), M. H. Cai (collapse list), X. Cai (collapse list), A. Calcaterra (collapse list), G. F. Cao (collapse list), N. Cao (collapse list), S. A. Cetin (collapse list), X. Y. Chai (collapse list), J. F. Chang (collapse list), T. T. Chang (collapse list), G. R. Che (collapse list), Y. Z. Che (collapse list), C. H. Chen (collapse list), Chao Chen (collapse list), G. Chen (collapse list), H. S. Chen (collapse list), H. Y. Chen (collapse list), M. L. Chen (collapse list), S. J. Chen (collapse list), S. M. Chen (collapse list), T. Chen (collapse list), X. R. Chen (collapse list), X. T. Chen (collapse list), X. Y. Chen (collapse list), Y. B. Chen (collapse list), Y. Q. Chen (collapse list), Z. K. Chen (collapse list), J. C. Cheng (collapse list), L. N. Cheng (collapse list), S. K. Choi (collapse list), X. Chu (collapse list), G. Cibinetto (collapse list), F. Cossio (collapse list), J. Cottee-Meldrum (collapse list), H. L. Dai (collapse list), J. P. Dai (collapse list), X. C. Dai (collapse list), A. Dbeyssi (collapse list), R. E. de Boer (collapse list), D. Dedovich (collapse list), C. Q. Deng (collapse list), Z. Y. Deng (collapse list), A. Denig (collapse list), I. Denisenko (collapse list), M. Destefanis (collapse list), F. De Mori (collapse list), X. X. Ding (collapse list), Y. Ding (collapse list), Y. X. Ding (collapse list), J. Dong (collapse list), L. Y. Dong (collapse list), M. Y. Dong (collapse list), X. Dong (collapse list), M. C. Du (collapse list), S. X. Du (collapse list), S. X. Du (collapse list), X. L. Du (collapse list), Y. Y. Duan (collapse list), Z. H. Duan (collapse list), P. Egorov (collapse list), G. F. Fan (collapse list), J. J. Fan (collapse list), Y. H. Fan (collapse list), J. Fang (collapse list), J. Fang (collapse list), S. S. Fang (collapse list), W. X. Fang (collapse list), Y. Q. Fang (collapse list), L. Fava (collapse list), F. Feldbauer (collapse list), G. Felici (collapse list), C. Q. Feng (collapse list), J. H. Feng (collapse list), L. Feng (collapse list), Q. X. Feng (collapse list), Y. T. Feng (collapse list), M. Fritsch (collapse list), C. D. Fu (collapse list), J. L. Fu (collapse list), Y. W. Fu (collapse list), H. Gao (collapse list), Y. Gao (collapse list), Y. N. Gao (collapse list), Y. N. Gao (collapse list), Y. Y. Gao (collapse list), Z. Gao (collapse list), S. Garbolino (collapse list), I. Garzia (collapse list), L. Ge (collapse list), P. T. Ge (collapse list), Z. W. Ge (collapse list), C. Geng (collapse list), E. M. Gersabeck (collapse list), A. Gilman (collapse list), K. Goetzen (collapse list), J. D. Gong (collapse list), L. Gong (collapse list), W. X. Gong (collapse list), W. Gradl (collapse list), S. Gramigna (collapse list), M. Greco (collapse list), M. D. Gu (collapse list), M. H. Gu (collapse list), C. Y. Guan (collapse list), A. Q. Guo (collapse list), J. N. Guo (collapse list), L. B. Guo (collapse list), M. J. Guo (collapse list), R. P. Guo (collapse list), X. Guo (collapse list), Y. P. Guo (collapse list), A. Guskov (collapse list), J. Gutierrez (collapse list), T. T. Han (collapse list), F. Hanisch (collapse list), K. D. Hao (collapse list), X. Q. Hao (collapse list), F. A. Harris (collapse list), C. Z. He (collapse list), K. L. He (collapse list), F. H. Heinsius (collapse list), C. H. Heinz (collapse list), Y. K. Heng (collapse list), C. Herold (collapse list), P. C. Hong (collapse list), G. Y. Hou (collapse list), X. T. Hou (collapse list), Y. R. Hou (collapse list), Z. L. Hou (collapse list), H. M. Hu (collapse list), J. F. Hu (collapse list), Q. P. Hu (collapse list), S. L. Hu (collapse list), T. Hu (collapse list), Y. Hu (collapse list), Z. M. Hu (collapse list), G. S. Huang (collapse list), K. X. Huang (collapse list), L. Q. Huang (collapse list), P. Huang (collapse list), X. T. Huang (collapse list), Y. P. Huang (collapse list), Y. S. Huang (collapse list), T. Hussain (collapse list), N. Hüsken (collapse list), N. in der Wiesche (collapse list), J. Jackson (collapse list), Q. Ji (collapse list), Q. P. Ji (collapse list), W. Ji (collapse list), X. B. Ji (collapse list), X. L. Ji (collapse list), X. Q. Jia (collapse list), Z. K. Jia (collapse list), D. Jiang (collapse list), H. B. Jiang (collapse list), P. C. Jiang (collapse list), S. J. Jiang (collapse list), X. S. Jiang (collapse list), Y. Jiang (collapse list), J. B. Jiao (collapse list), J. K. Jiao (collapse list), Z. Jiao (collapse list), S. Jin (collapse list), Y. Jin (collapse list), M. Q. Jing (collapse list), X. M. Jing (collapse list), T. Johansson (collapse list), S. Kabana (collapse list), N. Kalantar-Nayestanaki (collapse list), X. L. Kang (collapse list), X. S. Kang (collapse list), M. Kavatsyuk (collapse list), B. C. Ke (collapse list), V. Khachatryan (collapse list), A. Khoukaz (collapse list), O. B. Kolcu (collapse list), B. Kopf (collapse list), L. Kröger (collapse list), M. Kuessner (collapse list), X. Kui (collapse list), N. Kumar (collapse list), A. Kupsc (collapse list), W. Kühn (collapse list), Q. Lan (collapse list), W. N. Lan (collapse list), T. T. Lei (collapse list), M. Lellmann (collapse list), T. Lenz (collapse list), C. Li (collapse list), C. Li (collapse list), C. H. Li (collapse list), C. K. Li (collapse list), D. M. Li (collapse list), F. Li (collapse list), G. Li (collapse list), H. B. Li (collapse list), H. J. Li (collapse list), H. L. Li (collapse list), H. N. Li (collapse list), Hui Li (collapse list), J. R. Li (collapse list), J. S. Li (collapse list), J. W. Li (collapse list), K. Li (collapse list), K. L. Li (collapse list), L. J. Li (collapse list), Lei Li (collapse list), M. H. Li (collapse list), M. R. Li (collapse list), P. L. Li (collapse list), P. R. Li (collapse list), Q. M. Li (collapse list), Q. X. Li (collapse list), R. Li (collapse list), S. X. Li (collapse list), Shanshan Li (collapse list), T. Li (collapse list), T. Y. Li (collapse list), W. D. Li (collapse list), W. G. Li (collapse list), X. Li (collapse list), X. H. Li (collapse list), X. K. Li (collapse list), X. L. Li (collapse list), X. Y. Li (collapse list), X. Z. Li (collapse list), Y. Li (collapse list), Y. G. Li (collapse list), Y. P. Li (collapse list), Z. H. Li (collapse list), Z. J. Li (collapse list), Z. X. Li (collapse list), Z. Y. Li (collapse list), C. Liang (collapse list), H. Liang (collapse list), Y. F. Liang (collapse list), Y. T. Liang (collapse list), G. R. Liao (collapse list), L. B. Liao (collapse list), M. H. Liao (collapse list), Y. P. Liao (collapse list), J. Libby (collapse list), A. Limphirat (collapse list), D. X. Lin (collapse list), L. Q. Lin (collapse list), T. Lin (collapse list), B. J. Liu (collapse list), B. X. Liu (collapse list), C. X. Liu (collapse list), F. Liu (collapse list), F. H. Liu (collapse list), Feng Liu (collapse list), G. M. Liu (collapse list), H. Liu (collapse list), H. B. Liu (collapse list), H. H. Liu (collapse list), H. M. Liu (collapse list), Huihui Liu (collapse list), J. B. Liu (collapse list), J. J. Liu (collapse list), K. Liu (collapse list), K. Liu (collapse list), K. Y. Liu (collapse list), Ke Liu (collapse list), L. Liu (collapse list), L. C. Liu (collapse list), Lu Liu (collapse list), M. H. Liu (collapse list), P. L. Liu (collapse list), Q. Liu (collapse list), S. B. Liu (collapse list), W. M. Liu (collapse list), W. T. Liu (collapse list), X. Liu (collapse list), X. K. Liu (collapse list), X. L. Liu (collapse list), X. Y. Liu (collapse list), Y. Liu (collapse list), Y. Liu (collapse list), Y. B. Liu (collapse list), Z. A. Liu (collapse list), Z. D. Liu (collapse list), Z. Q. Liu (collapse list), Z. Y. Liu (collapse list), X. C. Lou (collapse list), H. J. Lu (collapse list), J. G. Lu (collapse list), X. L. Lu (collapse list), Y. Lu (collapse list), Y. H. Lu (collapse list), Y. P. Lu (collapse list), Z. H. Lu (collapse list), C. L. Luo (collapse list), J. R. Luo (collapse list), J. S. Luo (collapse list), M. X. Luo (collapse list), T. Luo (collapse list), X. L. Luo (collapse list), Z. Y. Lv (collapse list), X. R. Lyu (collapse list), Y. F. Lyu (collapse list), Y. H. Lyu (collapse list), F. C. Ma (collapse list), H. L. Ma (collapse list), Heng Ma (collapse list), J. L. Ma (collapse list), L. L. Ma (collapse list), L. R. Ma (collapse list), Q. M. Ma (collapse list), R. Q. Ma (collapse list), R. Y. Ma (collapse list), T. Ma (collapse list), X. T. Ma (collapse list), X. Y. Ma (collapse list), Y. M. Ma (collapse list), F. E. Maas (collapse list), I. MacKay (collapse list), M. Maggiora (collapse list), S. Malde (collapse list), Q. A. Malik (collapse list), H. X. Mao (collapse list), Y. J. Mao (collapse list), Z. P. Mao (collapse list), S. Marcello (collapse list), A. Marshall (collapse list), F. M. Melendi (collapse list), Y. H. Meng (collapse list), Z. X. Meng (collapse list), G. Mezzadri (collapse list), H. Miao (collapse list), T. J. Min (collapse list), R. E. Mitchell (collapse list), X. H. Mo (collapse list), B. Moses (collapse list), N. Yu. Muchnoi (collapse list), J. Muskalla (collapse list), Y. Nefedov (collapse list), F. Nerling (collapse list), H. Neuwirth (collapse list), Z. Ning (collapse list), S. Nisar (collapse list), Q. L. Niu (collapse list), W. D. Niu (collapse list), Y. Niu (collapse list), C. Normand (collapse list), S. L. Olsen (collapse list), Q. Ouyang (collapse list), S. Pacetti (collapse list), X. Pan (collapse list), Y. Pan (collapse list), A. Pathak (collapse list), Y. P. Pei (collapse list), M. Pelizaeus (collapse list), H. P. Peng (collapse list), X. J. Peng (collapse list), Y. Y. Peng (collapse list), K. Peters (collapse list), K. Petridis (collapse list), J. L. Ping (collapse list), R. G. Ping (collapse list), S. Plura (collapse list), V. Prasad (collapse list), F. Z. Qi (collapse list), H. R. Qi (collapse list), M. Qi (collapse list), S. Qian (collapse list), W. B. Qian (collapse list), C. F. Qiao (collapse list), J. H. Qiao (collapse list), J. J. Qin (collapse list), J. L. Qin (collapse list), L. Q. Qin (collapse list), L. Y. Qin (collapse list), P. B. Qin (collapse list), X. P. Qin (collapse list), X. S. Qin (collapse list), Z. H. Qin (collapse list), J. F. Qiu (collapse list), Z. H. Qu (collapse list), J. Rademacker (collapse list), C. F. Redmer (collapse list), A. Rivetti (collapse list), M. Rolo (collapse list), G. Rong (collapse list), S. S. Rong (collapse list), F. Rosini (collapse list), Ch. Rosner (collapse list), M. Q. Ruan (collapse list), N. Salone (collapse list), A. Sarantsev (collapse list), Y. Schelhaas (collapse list), K. Schoenning (collapse list), M. Scodeggio (collapse list), W. Shan (collapse list), X. Y. Shan (collapse list), Z. J. Shang (collapse list), J. F. Shangguan (collapse list), L. G. Shao (collapse list), M. Shao (collapse list), C. P. Shen (collapse list), H. F. Shen (collapse list), W. H. Shen (collapse list), X. Y. Shen (collapse list), B. A. Shi (collapse list), H. Shi (collapse list), J. L. Shi (collapse list), J. Y. Shi (collapse list), S. Y. Shi (collapse list), X. Shi (collapse list), H. L. Song (collapse list), J. J. Song (collapse list), M. H. Song (collapse list), T. Z. Song (collapse list), W. M. Song (collapse list), Y. X. Song (collapse list), Zirong Song (collapse list), S. Sosio (collapse list), S. Spataro (collapse list), S. Stansilaus (collapse list), F. Stieler (collapse list), S. S Su (collapse list), G. B. Sun (collapse list), G. X. Sun (collapse list), H. Sun (collapse list), H. K. Sun (collapse list), J. F. Sun (collapse list), K. Sun (collapse list), L. Sun (collapse list), R. Sun (collapse list), S. S. Sun (collapse list), T. Sun (collapse list), W. Y. Sun (collapse list), Y. C. Sun (collapse list), Y. H. Sun (collapse list), Y. J. Sun (collapse list), Y. Z. Sun (collapse list), Z. Q. Sun (collapse list), Z. T. Sun (collapse list), C. J. Tang (collapse list), G. Y. Tang (collapse list), J. Tang (collapse list), J. J. Tang (collapse list), L. F. Tang (collapse list), Y. A. Tang (collapse list), L. Y. Tao (collapse list), M. Tat (collapse list), J. X. Teng (collapse list), J. Y. Tian (collapse list), W. H. Tian (collapse list), Y. Tian (collapse list), Z. F. Tian (collapse list), I. Uman (collapse list), B. Wang (collapse list), B. Wang (collapse list), Bo Wang (collapse list), C. Wang (collapse list), C. Wang (collapse list), Cong Wang (collapse list), D. Y. Wang (collapse list), H. J. Wang (collapse list), J. Wang (collapse list), J. J. Wang (collapse list), J. P. Wang (collapse list), K. Wang (collapse list), L. L. Wang (collapse list), L. W. Wang (collapse list), M. Wang (collapse list), M. Wang (collapse list), N. Y. Wang (collapse list), S. Wang (collapse list), Shun Wang (collapse list), T. Wang (collapse list), T. J. Wang (collapse list), W. Wang (collapse list), W. P. Wang (collapse list), X. Wang (collapse list), X. F. Wang (collapse list), X. L. Wang (collapse list), X. N. Wang (collapse list), Xin Wang (collapse list), Y. Wang (collapse list), Y. D. Wang (collapse list), Y. F. Wang (collapse list), Y. H. Wang (collapse list), Y. J. Wang (collapse list), Y. L. Wang (collapse list), Y. N. Wang (collapse list), Y. N. Wang (collapse list), Yaqian Wang (collapse list), Yi Wang (collapse list), Yuan Wang (collapse list), Z. Wang (collapse list), Z. Wang (collapse list), Z. L. Wang (collapse list), Z. Q. Wang (collapse list), Z. Y. Wang (collapse list), Ziyi Wang (collapse list), D. Wei (collapse list), D. H. Wei (collapse list), H. R. Wei (collapse list), F. Weidner (collapse list), S. P. Wen (collapse list), U. Wiedner (collapse list), G. Wilkinson (collapse list), M. Wolke (collapse list), J. F. Wu (collapse list), L. H. Wu (collapse list), L. J. Wu (collapse list), L. J. Wu (collapse list), Lianjie Wu (collapse list), S. G. Wu (collapse list), S. M. Wu (collapse list), X. Wu (collapse list), Y. J. Wu (collapse list), Z. Wu (collapse list), L. Xia (collapse list), B. H. Xiang (collapse list), D. Xiao (collapse list), G. Y. Xiao (collapse list), H. Xiao (collapse list), Y. L. Xiao (collapse list), Z. J. Xiao (collapse list), C. Xie (collapse list), K. J. Xie (collapse list), Y. Xie (collapse list), Y. G. Xie (collapse list), Y. H. Xie (collapse list), Z. P. Xie (collapse list), T. Y. Xing (collapse list), C. J. Xu (collapse list), G. F. Xu (collapse list), H. Y. Xu (collapse list), M. Xu (collapse list), Q. J. Xu (collapse list), Q. N. Xu (collapse list), T. D. Xu (collapse list), X. P. Xu (collapse list), Y. Xu (collapse list), Y. C. Xu (collapse list), Z. S. Xu (collapse list), F. Yan (collapse list), L. Yan (collapse list), W. B. Yan (collapse list), W. C. Yan (collapse list), W. H. Yan (collapse list), W. P. Yan (collapse list), X. Q. Yan (collapse list), H. J. Yang (collapse list), H. L. Yang (collapse list), H. X. Yang (collapse list), J. H. Yang (collapse list), R. J. Yang (collapse list), Y. Yang (collapse list), Y. H. Yang (collapse list), Y. Q. Yang (collapse list), Y. Z. Yang (collapse list), Z. P. Yao (collapse list), M. Ye (collapse list), M. H. Ye (collapse list), Z. J. Ye (collapse list), Junhao Yin (collapse list), Z. Y. You (collapse list), B. X. Yu (collapse list), C. X. Yu (collapse list), G. Yu (collapse list), J. S. Yu (collapse list), L. W. Yu (collapse list), T. Yu (collapse list), X. D. Yu (collapse list), Y. C. Yu (collapse list), Y. C. Yu (collapse list), C. Z. Yuan (collapse list), H. Yuan (collapse list), J. Yuan (collapse list), J. Yuan (collapse list), L. Yuan (collapse list), M. K. Yuan (collapse list), S. H. Yuan (collapse list), Y. Yuan (collapse list), C. X. Yue (collapse list), Ying Yue (collapse list), A. A. Zafar (collapse list), F. R. Zeng (collapse list), S. H. Zeng (collapse list), X. Zeng (collapse list), Yujie Zeng (collapse list), Y. J. Zeng (collapse list), Y. C. Zhai (collapse list), Y. H. Zhan (collapse list), Shunan Zhang (collapse list), B. L. Zhang (collapse list), B. X. Zhang (collapse list), D. H. Zhang (collapse list), G. Y. Zhang (collapse list), G. Y. Zhang (collapse list), H. Zhang (collapse list), H. Zhang (collapse list), H. C. Zhang (collapse list), H. H. Zhang (collapse list), H. Q. Zhang (collapse list), H. R. Zhang (collapse list), H. Y. Zhang (collapse list), J. Zhang (collapse list), J. J. Zhang (collapse list), J. L. Zhang (collapse list), J. Q. Zhang (collapse list), J. S. Zhang (collapse list), J. W. Zhang (collapse list), J. X. Zhang (collapse list), J. Y. Zhang (collapse list), J. Z. Zhang (collapse list), Jianyu Zhang (collapse list), L. M. Zhang (collapse list), Lei Zhang (collapse list), N. Zhang (collapse list), P. Zhang (collapse list), Q. Zhang (collapse list), Q. Y. Zhang (collapse list), R. Y. Zhang (collapse list), S. H. Zhang (collapse list), Shulei Zhang (collapse list), X. M. Zhang (collapse list), X. Y. Zhang (collapse list), Y. Zhang (collapse list), Y. Zhang (collapse list), Y. T. Zhang (collapse list), Y. H. Zhang (collapse list), Y. P. Zhang (collapse list), Z. D. Zhang (collapse list), Z. H. Zhang (collapse list), Z. L. Zhang (collapse list), Z. L. Zhang (collapse list), Z. X. Zhang (collapse list), Z. Y. Zhang (collapse list), Z. Y. Zhang (collapse list), Z. Z. Zhang (collapse list), Zh. Zh. Zhang (collapse list), G. Zhao (collapse list), J. Y. Zhao (collapse list), J. Z. Zhao (collapse list), L. Zhao (collapse list), L. Zhao (collapse list), M. G. Zhao (collapse list), S. J. Zhao (collapse list), Y. B. Zhao (collapse list), Y. L. Zhao (collapse list), Y. X. Zhao (collapse list), Z. G. Zhao (collapse list), A. Zhemchugov (collapse list), B. Zheng (collapse list), B. M. Zheng (collapse list), J. P. Zheng (collapse list), W. J. Zheng (collapse list), X. R. Zheng (collapse list), Y. H. Zheng (collapse list), B. Zhong (collapse list), C. Zhong (collapse list), H. Zhou (collapse list), J. Q. Zhou (collapse list), S. Zhou (collapse list), X. Zhou (collapse list), X. K. Zhou (collapse list), X. R. Zhou (collapse list), X. Y. Zhou (collapse list), Y. X. Zhou (collapse list), Y. Z. Zhou (collapse list), A. N. Zhu (collapse list), J. Zhu (collapse list), K. Zhu (collapse list), K. J. Zhu (collapse list), K. S. Zhu (collapse list), L. Zhu (collapse list), L. X. Zhu (collapse list), S. H. Zhu (collapse list), T. J. Zhu (collapse list), W. D. Zhu (collapse list), W. J. Zhu (collapse list), W. Z. Zhu (collapse list), Y. C. Zhu (collapse list), Z. A. Zhu (collapse list), X. Y. Zhuang (collapse list), J. H. Zou (collapse list), J. Zu (collapse list)

原始论文采用 CC BY 4.0 许可（http://creativecommons.org/licenses/by/4.0/）。 ✨ 这是对下方论文的AI生成解释。它不是由作者撰写或认可的。如需技术准确性，请参阅原始论文。阅读完整免责声明

在亚原子世界中，物质是由被称为超子（hyperons）的一小类粒子构成的。它们是构成我们身体的质子和中子的“重量级亲戚”，但它们极不稳定，在产生后几乎瞬间就会消失。在这些粒子中，中性西格玛超子（neutral sigma hyperon）因其消失的方式而占据着特殊的地位。大多数同类粒子是通过分解成其他重粒子来衰变的，但中性西格玛超子非常独特：它几乎总是通过发射一个被称为光子的单粒子，转化为一种更轻的超子——兰达超子（lambda hyperon）。这一过程受电磁力支配，这种看不见的作用力既让原子保持结合，也让磁铁能吸附在冰箱上。由于这种衰变发生得非常纯净且由光驱动，它为科学家提供了一个罕见而清晰的窗口，用以观察这些奇异粒子的内部结构如何与电磁场相互作用。通过研究这种转变究竟是如何发生的，研究人员可以测试描述宇宙基本组成部分的物理学基本规则。

一支使用北京电子正负电子对撞机（BESIII探测器）工作的物理学家团队，现在迈出了观察这种特定且此前从未被观测到的衰变变体的第一步实验。在这种情况下，中性西格码超子不再仅仅发射单个光子，而是被观察到在转化过程中发射了一对电子和正电子（即光子分裂成了物质与反物质）。这种被称为“达利茨衰变”（Dalitz decay）的罕见事件在几十年前就已被理论预言，但从未被直接测量过。为了捕捉这一稍纵即逝的时刻，研究人员分析了包含一百亿次电子与正电子碰撞的海量数据。在这些碰撞中，能量被转化为一对中性西格玛超子及其反物质对应物。团队使用了一种巧妙的方法来识别信号：他们首先以标准方式重建其中一个超子的衰变，将其作为确认事件发生的“标签”，然后观察剩余的碎片，以寻找另一个超子产生的罕见电子-正电子对。

这项艰苦搜寻的结果是对这种罕见衰变发生频率的一次精确测量。研究人员发现，在每千个中性西格玛超子衰变的过程中，大约有六个会经历这种特定的向兰达超子和一对电子-正电子对的转化。这对应于一个约为 0.00634 的概率，即分支比（branching fraction）。这个数值略高于标准理论计算的预测值，此前的估算概率为 0.0055。虽然差异很小，但在统计学上已足够显著，足以表明当前的理论模型可能需要进行微调，以完全解释这些粒子的行为。除了这一测量结果外，团队还计算了一个关键的物理属性——跃迁磁矩（transition magnetic moment），它描述了在衰变过程中两种超子之间磁相互作用的强度。他们测得该值为质子磁矩的 1.74 倍。这一测量结果提供了直接观察超子内部磁结构的全新视角，填补了我们对这些粒子在低能级水平下行为理解的空白。

这项工作代表了实验室环境下首次观察并测量到这种特定的衰变。通过证实这一过程的存在并提供其发生频率的精确数值，该研究验证了探测超子电磁结构所需的实验技术。测量值与理论预测之间的轻微差异引发了进一步调查的兴趣，这可能导致对支配亚原子世界的力有更深入的理解。这些发现并未推翻现有的物理学，而是对其进行了完善，为物质与光如何在最基本层面上相互作用提供了一张更详细的地图。有了这些新数据，科学家现在拥有了一个可以用来测试其理论的具体基准，朝着构建宇宙最小基本组成部分的完整图景又迈进了一步。

技术摘要：超晕衰变 $\Sigma^0 \to \Lambda e^+e^-$ 的分支比与跃迁磁矩测量

问题与动机
$\Sigma^0$ 超晕是基态 SU(3) 超晕中非常独特的一个，其主要通过电磁相互作用进行衰变。尽管早在 1958 年就有人预测了电磁 Dalitz 衰变 $\Sigma^0 \to \Lambda e^+e^-$ ，但直到这项工作为止，该过程尚未得到详细的实验研究。基于量子电动力学 (QED) 的理论计算预测其分支比 (BF) 为 $5.5 \times 10^{-3}$ 。然而，在低动量传递 ( $q^2$ ) 的类时区域（time-like region）一直缺乏实验数据，此前的测量仅限于 20 世纪 80 年代通过高能 $\Lambda$ 束流散射（类空区域/space-like region）或高 $q^2$ 类时区域的测量。这一空白阻碍了对全运动学范围内跃迁形状因子 (FF) 的全面理解，并限制了对超晕内在夸克-胶子结构的深入了解。此外，过渡磁矩 ( $\mu$ ) 是描述 $\Sigma^0-\Lambda$ 跃迁顶点的关键参数，需要通过在低 $q^2$ 区域的精确测定来检验理论模型。

方法论
本研究利用了由 BESIII 探测器在 BEPCII 对撞机上收集的 $(10087 \pm 44) \times 10^6$ 个 $J/\psi$ 事件样本。分析采用了双标记 (Double Tag, DT) 技术来测量绝对分支比并提高信噪比：

单标记 (Single Tag, ST)： 通过主衰变模式 $\bar{\Sigma}^0 \to \bar{\Lambda}\gamma$ （其中 $\bar{\Lambda} \to \bar{p}\pi^+$ ）重建 $\Sigma^0$ 候选事件。利用重建出的 $\bar{\Sigma}^0$ 对向的反冲质量来识别 $J/\psi \to \Sigma^0 \bar{\Sigma}^0$ 信号事件。
双标记 (DT)： 从相对于 ST $\bar{\Sigma}^0$ 的反向轨迹中重建信号衰变 $\Sigma^0 \to \Lambda e^+e^-$ 。 $\Lambda$ 通过 $\Lambda \to p\pi^-$ 进行重建。
事件选择： 应用严格的运动学和粒子识别 (PID) 标准。要求带电径迹满足动量和顶点约束。通过特定的电离能损失 ($dE/dx$) 和飞行时间 (TOF) 信息来识别电子。执行在 $J/\psi \to p\bar{p}\pi^+\pi^- \gamma e^+e^-$ 仮定下的运动学拟合 (4C fit)，以满足能量和动量守恒。
背景抑制： 主要背景源于束管或漂移室中的光子转换 ( $\gamma \to e^+e^-$ )。这通过基于 $e^+e^-$ 顶点的径向距离和成对不变质量的甄别（veto）来进行抑制。
产额提取： 对 ST 产额的剩余质量分布和 DT 产额的 $e^+e^-$ 不变量质量 ( $M_{e^+e^-}$ ) 分布进行极大似然拟合。信号形状由蒙特卡洛 (MC) 模拟得出，而背景则用多项式函数进行建模。

主要贡献与结果
本文呈现了 $\Sigma^0 \to \Lambda e^+e^-$ Dalitz 衰变的首次实验研究。绝对分支比通过以下公式计算：
$\mathcal{B}(\Sigma^0 \to \Lambda e^+e^-) = \frac{N_{DT}}{N_{ST}} \times \frac{\epsilon_{ST}}{\epsilon_{DT}} \times \frac{1}{\mathcal{B}(\Lambda \to p\pi^-)}$
其中 $N$ 代表产额， $\epsilon$ 代表探测效率。

分支比： 测得的绝对分支比为：
$\mathcal{B}(\Sigma^0 \to \Lambda e^+e^-) = (6.34 \pm 0.25_{\text{stat}} \pm 0.23_{\text{syst}}) \times 10^{-3}$
该结果与粒子数据组 (PDG) 引用的 $5.5 \times 10^{-3}$ 的理论 QED 预测值存在约 $2\sigma$ 的偏差。
跃迁磁矩： 利用测得的分支比以及它与 $q^2=0$ 时处磁形式因子的关系，确定跃迁磁矩为：
$\mu = (1.74 \pm 0.03_{\text{stat}} \pm 0.09_{\text{syst}}) \mu_N$
其中 $\mu_N$ 是核子磁矩。该值在 $2\sigma$ 范围内与 PDG 平均值一致。
系统误差： 系统误差针对径迹重建、PID、顶点拟合、运动学拟合以及产额提取进行了评估。双标记方法确保了与 ST 端相关的系统误差在很大程度上得到了抵消。

意义
作者声称，本分析提供了迄今为止对 $\Sigma^0 \to \Lambda e^+e^-$ 衰变分支比和跃迁磁矩最精确的测量。通过填补低 $q^2$ 类时区域的实验空白，研究结果为理解 $\Sigma^0$ 超晕的内在结构以及 $\Sigma^0-\Lambda$ 电磁跃迁的性质提供了宝贵的见解。观察到的分支比与标准 QED 预测之间的偏差值得进一步的理论研究，而跃迁磁矩的精确测定则为超晕结构模型提供了约束。

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