⚛️ high-energy experiments

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

Unter Verwendung einer Stichprobe von 10 Milliarden $J/\psi$ -Ereignissen aus dem BESIII-Detektor berichtet diese Studie über die erste experimentelle Beobachtung des Dalitz-Zerfalls $\Sigma^0 \rightarrow \Lambda e^+e^-$ , wobei den Verzweigungsverhältnis als $(6,34 \pm 0,25_{\rm stat.} \pm 0,23_{\rm syst.}) \times 10^{-3}$ gemessen und das Übergangsmagnetmoment auf $(1,74 \pm 0,03_{\rm stat.} \pm 0,09_{\rm syst.})\,\mu_N$ bestimmt wurde, wobei das Ergebnis des Verzweigungsverhältnisses eine $2\sigma$ -Diskrepanz zu bisherigen theoretischen Vorhersagen aufweist.

Ursprüngliche Autoren: 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)

Veröffentlicht 2026-08-18

📖 4 Min. Lesezeit🧠 Tiefgang

CC BY 4.0

Ursprüngliche Autoren: 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. 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Originalarbeit lizenziert unter CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ Dies ist eine KI-generierte Erklärung des untenstehenden Papers. Sie wurde nicht von den Autoren verfasst oder gebilligt. Für technische Genauigkeit konsultieren Sie das Originalpaper. Vollständigen Haftungsausschluss lesen

In der subatomaren Welt besteht Materie aus einer kleinen Familie von Teilchen, den Hyperons. Dies sind schwere Cousins der Protonen und Neutronen, aus denen unsere eigenen Körper bestehen, aber sie sind instabil und verschwinden fast augenblicklich nach ihrer Entstehung. Unter ihnen nimmt das neutrale Sigma-Hyperon einen besonderen Platz ein, und zwar aufgrund der Art und Weise, wie es verschwindet. Während die meisten Teilchen dieser Art zerfallen, indem sie in andere schwere Teilchen zerbrechen, ist das neutrale Sigma-Hyperon einzigartig: Es transformiert sich fast immer in ein leichteres Hyperon, das Lambda, indem es ein einzelnes Lichtteilchen, bekannt als Photon, aussendet. Dieser Prozess wird durch die elektromagnetische Kraft gesteuert, dieselbe unsichtbare Wechselwirkung, die Atome zusammenhält und es Magneten ermöglicht, an Kühlschränken zu haften. Da dieser Zerfall so sauber abläuft und durch Licht angetrieben wird, bietet er Wissenschaftlern ein seltenes und klares Fenster, um zu sehen, wie die interne Struktur dieser seltsamen Teilchen mit dem elektromagnetischen Feld interagiert. Durch das Studium genau dessen, wie diese Transformation stattfindet, können Forscher die grundlegenden Regeln der Physik testen, die die Bausteine des Universums beschreiben.

Ein Team von Physikern, das mit dem BESIII-Detektor am Beijing Electron Positron Collider arbeitet, hat nun den ersten experimentellen Schritt unternommen, um eine sehr spezifische und bisher ungesehene Variation dieses Zerfalls zu beobachten. Anstatt einfach ein einzelnes Photon auszusenden, wurde beobachtet, dass das neutrale Sigma-Hyperon während seiner Transformation ein Paar aus Elektronen und Positronen (ein Lichtteilchen, das sich in Materie und Antimaterie aufgespalten hat) aussendet. Dieses seltene Ereignis, bekannt als Dalitz-Zerfall, wurde vor Jahrzehnten theoretisch vorhergesagt, aber noch nie direkt gemessen. Um diesen flüchtigen Moment einzufangen, analysierten die Forscher eine massive Datensammlung, die zehn Milliarden Kollisionen von Elektronen und Positronen enthielt. In diesen Kollisionen wurde die Energie in Paare aus neutralen Sigma-Hyperons und deren Antimaterie-Gegenstücken umgewandelt. Das Team wandte eine clevere Methode an, um das Signal zu identifizieren: Zuerst rekonstruierten sie den Zerfall eines der Hyperons auf eine Standardmethode, was als „Tag“ diente, um zu bestätigen, dass das Ereignis stattgefunden hatte, und suchten dann in den verbleibenden Trümmern nach dem seltenen Elektron-Positron-Paar des anderen Hyperons.

Das Ergebnis dieser mühsamen Suche ist eine präzise Messung der Häufigkeit, mit der dieser seltene Zerfall stattfindet. Die Forscher fanden heraus, dass für je tausend neutrale Sigma-Hyperons, die zerfallen, etwa sechs diese spezifische Transformation in ein Lambda-Hyperon und ein Elektron-Positron-Paar durchlaufen. Dies entspricht einer Wahrscheinlichkeit, oder einem Verzweigungsverhältnis, von etwa 0,00634. Diese Zahl ist etwas höher als der Wert, der durch Standard-Theorieberechnungen vorhergesagt wurde, welche eine Wahrscheinlichkeit von 0,0055 geschätzt hatten. Obwohl der Unterschied gering ist, ist er statistisch signifikant genug, um darauf hinzudeuten, dass die aktuellen theoretischen Modelle möglicherweise eine leichte Anpassung benötigen, um das Verhalten dieser Teilchen vollständig zu erklären. Neben dieser Messung berechnete das Team eine Schlüsselgröße der Physik, das sogenannte Übergangsmagnetmoment, welches die Stärke der magnetischen Wechselwirkung zwischen den beiden Arten von Hyperons während des Zerfalls beschreibt. Sie ermittelten diesen Wert zu 1,74 Mal dem magnetischen Moment eines Protons. Diese Messung liefert einen neuen, direkten Blick auf die interne magnetische Struktur des Hyperons und schließt eine Lücke in unserem Verständnis darüber, wie sich diese Teilchen auf niedrigen Energieniveaus verhalten.

Diese Arbeit stellt das erste Mal dar, dass dieser spezifische Zerfall in einem Labor beobachtet und gemessen wurde. Durch die Bestätigung der Existenz dieses Prozesses und die Bereitstellung einer präzisen Zahl für seine Häufigkeit validiert die Studie die experimentellen Techniken, die notwendig sind, um die elektromagnetische Struktur von Hyperons zu untersuchen. Die geringfügige Diskrepanz zwischen dem gemessenen Wert und der theoretischen Vorhersage lädt zu weiteren Untersuchungen ein, was potenziell zu einem tieferen Verständnis der Kräfte führen kann, die die subatomare Welt regieren. Die Ergebnisse stürzen die bestehende Physik nicht um, sondern verfeinern sie, indem sie eine detailliertere Karte davon liefern, wie Materie und Licht auf der fundamentalsten Ebene interagieren. Mit diesen neuen Daten haben Wissenschaftler nun einen konkreten Referenzwert, um ihre Theorien daran zu testen, und kommen damit einem Schritt näher an ein vollständiges Bild des Universums und seiner kleinsten Bausteine.

Technische Zusammenfassung: Messung der Verzweigungsverhältnis und des Übergangs-Magnetischen Moments des Hyperon-Dalitz-Zerfalls $\Sigma^0 \to \Lambda e^+e^-$

Problem und Motivation
Das $\Sigma^0$ -Hyperon ist unter den Grundzustands-SU(3)-Hyperonen einzigartig, da es dominant über die elektromagnetische Wechselwirkung zerfällt. Obwohl der elektromagnetische Dalitz-Zerfall $\Sigma^0 \to \Lambda e^+e^-$ bereits 1958 vorhergesagt wurde, wurde er bis zu dieser Arbeit experimentell nicht im Detail untersucht. Theoretische Berechnungen auf Basis der Quantenelektrodynamik (QED) sagen ein Verzweigungsverhältnis (BF) von $5,5 \times 10^{-3}$ voraus. Jedoch fehlten experimentelle Daten im Bereich des niedrigen Impulsübertrags ( $q^2$ ) im Zeitähnlichkeitsbereich (time-like region), da frühere Messungen auf die 1980er Jahre durch Streuung hochenergetischer $\Lambda$ -Strahlen (Raumähnlichkeitsbereich bzw. space-like region) oder Messungen bei hohem $q^2$ im Zeitähnlichkeitsbereich beschränkt waren. Diese Lücke verhindert ein umfassendes Verständnis des Übergangsformfaktors (FF) über den gesamten kinematischen Bereich und begrenzt die Erkenntnisse über die intrinsische Quark-Gluon-Struktur von Hyperonen. Darüber hinaus erfordert das Übergangs-Magnetische Moment ( $\mu$ ), ein kritischer Parameter, der den $\Sigma^0-\Lambda$ -Übergangsknoten beschreibt, eine präzise Bestimmung im niedrigen $q^2$ -Bereich, um theoretische Modelle zu testen.

Methodik
Die Studie nutzt einen Datensatz von $(10087 \pm 44) \times 10^6$ $J/\psi$ -Ereignissen, die mit dem BESIII-Detektor am BEPCII-Collider gesammelt wurden. Die Analyse verwendet eine Double-Tag (DT)-Technik, um das absolute Verzweigungsverhältnis zu messen und das Signal-zu-Hintergrund-Verhältnis zu verbessern:

Single Tag (ST): $\Sigma^0$ -Kandidaten werden über den dominanten Zerfallmodus $\bar{\Sigma}^0 \to \bar{\Lambda}\gamma$ (mit $\bar{\Lambda} \to \bar{p}\pi^+$ ) rekonstruiert. Die Rückstoßmasse gegen das rekonstruierte $\bar{\Sigma}^0$ wird verwendet, um die $J/\psi \to \Sigma^0 \bar{\Sigma}^0$ Signalereignisse zu identifizieren.
Double Tag (DT): Der Signalzerfall $\Sigma^0 \to \Lambda e^+e^-$ wird aus den Spuren rekonstruiert, die gegen das ST $\bar{\Sigma}^0$ zurückstoßen. Das $\Lambda$ wird über $\Lambda \to p\pi^-$ rekonstruiert.
Ereignisauswahl: Strenge kinematische und Teilchenidentifikations-Kriterien (PID) werden angewendet. Geladene Spuren müssen die Impuls- und Vertex-Beschränkungen erfüllen. Elektronen werden mittels spezifischer Energieverlust-Messungen ($dE/dx$) und Time-of-Flight (TOF)-Informationen identifiziert. Ein Kinematik-Fit (4C-Fit), der Energie- und Impulserhaltung erzwingt, wird unter der Hypothese $J/\psi \to p\bar{p}\pi^+\pi^- \gamma e^+e^-$ durchgeführt.
Hintergrundunterdrückung: Ein primärer Hintergrund entsteht durch Photonenkonversionen ( $\gamma \to e^+e^-$ ) in der Strahlröhre oder der Driftkammer. Dieser wird durch ein Veto unterdrückt, das auf dem radialen Abstand des $e^+e^-$ -Vertex und der invarianten Masse des Paares basiert.
Auswertung der Ausbeute (Yield Extraction): Maximum-Likelihood-Fits werden auf die Rückstoßmassenverteilung für ST-Ausbeuten und die $e^+e^-$ -Invariante-Masse-Verteilung ( $M_{e^+e^-}$ ) für DT-Ausbeuten durchgeführt. Signalformen werden aus Monte-Carlo-Simulationen (MC) abgeleitet, während Hintergründe mit Polynomfunktionen modelliert werden.

Wesentliche Beiträge und Ergebnisse
Diese Arbeit präsentiert die erste experimentelle Untersuchung des $\Sigma^0 \to \Lambda e^+e^-$ Dalitz-Zerfalls. Das absolute Verzweigungsverhältnis wird mit der Formel berechnet:
$\mathcal{B}(\Sigma^0 \to \Lambda e^+e^-) = \frac{N_{DT}}{N_{ST}} \times \frac{\epsilon_{ST}}{\epsilon_{DT}} \times \frac{1}{\mathcal{B}(\Lambda \to p\pi^-)}$
wobei $N$ die Ausbeuten und $\epsilon$ die Detektionseffizienzen darstellt.

Verzweigungsverhältnis: Das gemessene absolute Verzweigungsverhältnis ist:
$\mathcal{B}(\Sigma^0 \to \Lambda e^+e^-) = (6,34 \pm 0,25_{\text{stat}} \pm 0,23_{\text{syst}}) \times 10^{-3}$
Dieses Ergebnis zeigt eine Diskrepanz von etwa $2\sigma$ zur theoretischen QED-Vorhersage von $5,5 \times 10^{-3}$ , wie sie in der Particle Data Group (PDG) angegeben ist.
Übergangs-Magnetisches Moment: Unter Verwendung des gemessenen Verzweigungsverhältnisses und der Beziehung zum magnetischen Formfaktor bei $q^2=0$ wird das Übergangs-Magnetische Moment bestimmt zu:
$\mu = (1,74 \pm 0,03_{\text{stat}} \pm 0,09_{\text{syst}}) \mu_N$
wobei $\mu_N$ das magnetische Moment des Nukleons ist. Dieser Wert liegt innerhalb von $2\sigma$ konsistent mit dem PDG-Durchschnitt.
Systematische Unsicherheiten: Systematische Unsicherheiten werden für das Tracking, die PID, den Vertex-Fit, den Kinematik-Fit und die Extraktion der Ausbeuten bewertet. Die Double-Tag-Methode stellt sicher, dass die mit der ST-Seite verbundenen systematischen Unsicherheiten weitgehend herausfallen.

Bedeutung
Die Autoren behaupten, dass diese Analyse die präziseste bisherige Messung des Verzweigungsverhältnisses und des Übergangs-Magnetischen Moments für den $\Sigma^0 \to \Lambda e^+e^-$ Zerfall liefert. Durch das Schließen der experimentellen Lücke im niedrigen $q^2$ -Zeitähnlichkeitsbereich bieten die Ergebnisse wertvolle Einblicke in die intrinsische Struktur des $\Sigma^0$ -Hyperons und die Natur des $\Sigma^0-\Lambda$ elektromagnetischen Übergangs. Die beobachtete Abweichung des Verzweigungsverhältnisses von der Standard-QED-Vorhersage rechtfertigt weitere theoretische Untersuchungen, während die präzise Bestimmung des Übergangs-Magnetischen Moments Modelle der Hyperonstruktur einschränkt.

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