Letter
Open Access

Amplitude analysis of the isospin-violating decay $J / ψ \to γ η π^{0}$

M. Ablikim ¹, M. N. Achasov ^4,d, P. Adlarson ⁸¹, X. C. Ai ⁸⁷, C. S. Akondi ^31a,31b, R. Aliberti ³⁹, A. Amoroso ^80a,80c, Q. An^77,64,a, Y. H. An ⁸⁷ et al. (BESIII Collaboration)

Y. H. An ⁸⁷, Y. Bai ⁶², O. Bakina ⁴⁰, H.-R. Bao ⁷⁰, X. L. Bao ⁴⁹, M. Barbagiovanni ^80c, V. Batozskaya ^1,48, K. Begzsuren³⁵, N. Berger ³⁹, M. Berlowski ⁴⁸, M. B. Bertani ^30a, D. Bettoni ^31a, F. Bianchi ^80a,80c, E. Bianco^80a,80c, A. Bortone ^80a,80c, I. Boyko ⁴⁰, R. A. Briere ⁵, A. Brueggemann ⁷⁴, D. Cabiati ^80a,80c, H. Cai ⁸², M. H. Cai ^42,l,m, X. Cai ^1,64, A. Calcaterra ^30a, G. F. Cao ^1,70, N. Cao ^1,70, S. A. Cetin ^68a, X. Y. Chai ^50,i, J. F. Chang ^1,64, T. T. Chang ⁴⁷, G. R. Che ⁴⁷, Y. Z. Che ^1,64,70, C. H. Chen ¹⁰, Chao Chen ¹, G. Chen ¹, H. S. Chen ^1,70, H. Y. Chen ²⁰, M. L. Chen ^1,64,70, S. J. Chen ⁴⁶, S. M. Chen ⁶⁷, T. Chen ^1,70, W. Chen ⁴⁹, X. R. Chen ^34,70, X. T. Chen ^1,70, X. Y. Chen ^12,h, Y. B. Chen ^1,64, Y. Q. Chen ¹⁶, Z. K. Chen ⁶⁵, J. Cheng ⁴⁹, L. N. Cheng ⁴⁷, S. K. Choi ¹¹, X. Chu ^12,h, G. Cibinetto ^31a, F. Cossio ^80c, J. Cottee-Meldrum ⁶⁹, H. L. Dai ^1,64, J. P. Dai ⁸⁵, X. C. Dai ⁶⁷, A. Dbeyssi¹⁹, R. E. de Boer ³, D. Dedovich ⁴⁰, C. Q. Deng ⁷⁸, Z. Y. Deng ¹, A. Denig ³⁹, I. Denisenko ⁴⁰, M. Destefanis ^80a,80c, F. De Mori ^80a,80c, E. Di Fiore ^31a,31b, X. X. Ding ^50,i, Y. Ding ⁴⁴, Y. X. Ding ³², Yi. Ding ³⁸, J. Dong ^1,64, L. Y. Dong ^1,70, M. Y. Dong ^1,64,70, X. Dong ⁸², M. C. Du ¹, S. X. Du ⁸⁷, Shaoxu Du ^12,h, X. L. Du ^12,h, Y. Q. Du ⁸², Y. Y. Duan ⁶⁰, Z. H. Duan ⁴⁶, P. Egorov ^40,b, G. F. Fan ⁴⁶, J. J. Fan ²⁰, Y. H. Fan ⁴⁹, J. Fang ^1,64, Jin Fang ⁶⁵, S. S. Fang ^1,70, W. X. Fang ¹, Y. Q. Fang ^1,64,a, L. Fava ^80b,80c, F. Feldbauer ³, G. Felici ^30a, C. Q. Feng ^77,64, J. H. Feng ¹⁶, L. Feng ^42,l,m, Q. X. Feng ^42,l,m, Y. T. Feng ^77,64, M. Fritsch ³, C. D. Fu ¹, J. L. Fu ⁷⁰, Y. W. Fu ^1,70, H. Gao ⁷⁰, Y. Gao ^77,64, Y. N. Gao ^50,i, Y. Y. Gao ³², Yunong Gao ²⁰, Z. Gao ⁴⁷, S. Garbolino ^80c, I. Garzia ^31a,31b, L. Ge ⁶², P. T. Ge ²⁰, Z. W. Ge ⁴⁶, C. Geng ⁶⁵, E. M. Gersabeck ⁷³, A. Gilman ⁷⁵, K. Goetzen ¹³, J. Gollub ³, J. B. Gong ^1,70, J. D. Gong ³⁸, L. Gong ⁴⁴, W. X. Gong ^1,64, W. Gradl ³⁹, S. Gramigna ^31a,31b, M. Greco ^80a,80c, M. D. Gu ⁵⁵, M. H. Gu ^1,64, C. Y. Guan ^1,70, A. Q. Guo ³⁴, H. Guo ⁵⁴, J. N. Guo ^12,h, L. B. Guo ⁴⁵, M. J. Guo ⁵⁴, R. P. Guo ⁵³, X. Guo ⁵⁴, Y. P. Guo ^12,h, Z. Guo ^77,64, A. Guskov ^40,b, J. Gutierrez ²⁹, J. Y. Han ^77,64, T. T. Han ¹, X. Han ^77,64, F. Hanisch ³, K. D. Hao ^77,64, X. Q. Hao ²⁰, F. A. Harris ⁷¹, C. Z. He ^50,i, K. K. He ^17,46, K. L. He ^1,70, F. H. Heinsius ³, C. H. Heinz ³⁹, Y. K. Heng ^1,64,70, C. Herold ⁶⁶, P. C. Hong ³⁸, G. Y. Hou ^1,70, X. T. Hou ^1,70, Y. R. Hou ⁷⁰, Z. L. Hou ¹, H. M. Hu ^1,70, J. F. Hu ^61,k, Q. P. Hu ^77,64, S. L. Hu ^12,h, T. Hu ^1,64,70, Y. Hu ¹, Y. X. Hu ⁸², Z. M. Hu ⁶⁵, G. S. Huang ^77,64, K. X. Huang ⁶⁵, L. Q. Huang ^34,70, P. Huang ⁴⁶, X. T. Huang ⁵⁴, Y. P. Huang ¹, Y. S. Huang ⁶⁵, T. Hussain ⁷⁹, N. Hüsken ³⁹, N. in der Wiesche ⁷⁴, J. Jackson ²⁹, Q. Ji ¹, Q. P. Ji ²⁰, W. Ji ^1,70, X. B. Ji ^1,70, X. L. Ji ^1,64, Y. Y. Ji ¹, L. K. Jia ⁷⁰, X. Q. Jia ⁵⁴, Z. K. Jia ^77,64, D. Jiang ^1,70, H. B. Jiang ⁸², S. J. Jiang ¹⁰, X. S. Jiang ^1,64,70, Y. Jiang ⁷⁰, J. B. Jiao ⁵⁴, J. K. Jiao ³⁸, Z. Jiao ²⁵, L. C. L. Jin ¹, S. Jin ⁴⁶, Y. Jin ⁷², M. Q. Jing ^1,70, X. M. Jing ⁷⁰, T. Johansson ⁸¹, S. Kabana ³⁶, X. L. Kang ¹⁰, X. S. Kang ⁴⁴, B. C. Ke ⁸⁷, V. Khachatryan ²⁹, A. Khoukaz ⁷⁴, O. B. Kolcu ^68a, B. Kopf ³, L. Kröger ⁷⁴, L. Krümmel³, Y. Y. Kuang ⁷⁸, M. Kuessner ³, X. Kui ^1,70, N. Kumar ²⁸, A. Kupsc ^48,81, W. Kühn ⁴¹, Q. Lan ⁷⁸, W. N. Lan ²⁰, T. T. Lei ^77,64, M. Lellmann ³⁹, T. Lenz ³⁹, C. Li ⁵¹, C. H. Li ⁴⁵, C. K. Li ⁴⁷, Chunkai Li ²¹, Cong Li ⁴⁷, D. M. Li ⁸⁷, F. Li ^1,64, G. Li ¹, H. B. Li ^1,70, H. J. Li ²⁰, H. L. Li ⁸⁷, H. N. Li ^61,k, H. P. Li ⁴⁷, Hui Li ⁴⁷, J. N. Li ³², J. S. Li ⁶⁵, J. W. Li ⁵⁴, K. Li ¹, K. L. Li ^42,l,m, L. J. Li ^1,70, Lei Li ⁵², M. H. Li ⁴⁷, M. R. Li ^1,70, M. T. Li ⁵⁴, P. L. Li ⁷⁰, P. R. Li ^42,l,m, Q. M. Li ^1,70, Q. X. Li ⁵⁴, R. Li ^18,34, S. Li ⁸⁷, S. X. Li ⁸⁷, S. Y. Li ⁸⁷, Shanshan Li ^27,j, T. Li ⁵⁴, T. Y. Li ⁴⁷, W. D. Li ^1,70, W. G. Li ^1,a, X. Li ^1,70, X. H. Li ^77,64, X. K. Li ^50,i, X. L. Li ⁵⁴, X. Y. Li ^1,9, X. Z. Li ⁶⁵, Y. Li ²⁰, Y. G. Li ⁷⁰, Y. P. Li ³⁸, Z. H. Li ⁴², Z. J. Li ⁶⁵, Z. L. Li ⁸⁷, Z. X. Li ⁴⁷, Z. Y. Li ⁸⁵, C. Liang ⁴⁶, H. Liang ^77,64, Y. F. Liang ⁵⁹, Y. T. Liang ^34,70, G. R. Liao ¹⁴, L. B. Liao ⁶⁵, M. H. Liao ⁶⁵, Y. P. Liao ^1,70, J. Libby ²⁸, A. Limphirat ⁶⁶, C. C. Lin ⁶⁰, C. X. Lin ³⁴, D. X. Lin ^34,70, T. Lin ¹, B. J. Liu ¹, B. X. Liu ⁸², C. Liu ³⁸, C. X. Liu ¹, F. Liu ¹, F. H. Liu ⁵⁸, Feng Liu ⁶, G. M. Liu ^61,k, H. Liu ^42,l,m, H. B. Liu ¹⁵, H. M. Liu ^1,70, Huihui Liu ²², J. B. Liu ^77,64, J. J. Liu ²¹, K. Liu ^42,l,m, K. Y. Liu ⁴⁴, Ke Liu ²³, Kun Liu ⁷⁸, L. Liu ⁴², L. C. Liu ⁴⁷, Lu Liu ⁴⁷, M. H. Liu ³⁸, P. L. Liu ⁵⁴, Q. Liu ⁷⁰, S. B. Liu ^77,64, T. Liu ¹, W. M. Liu ^77,64, W. T. Liu ⁴³, X. Liu ^42,l,m, X. K. Liu ^42,l,m, X. L. Liu ^12,h, X. P. Liu ^12,h, X. Y. Liu ⁸², Y. Liu ^42,l,m, Y. B. Liu ⁴⁷, Yi Liu ⁸⁷, Z. A. Liu ^1,64,70, Z. D. Liu ⁸³, Z. L. Liu ⁷⁸, Z. Q. Liu ⁵⁴, Z. X. Liu ¹, Z. Y. Liu ⁴², X. C. Lou ^1,64,70, H. J. Lu ²⁵, J. G. Lu ^1,64, X. L. Lu ¹⁶, Y. Lu ⁷, Y. H. Lu ^1,70, Y. P. Lu ^1,64, Z. H. Lu ^1,70, C. L. Luo ⁴⁵, J. R. Luo ⁶⁵, J. S. Luo ^1,70, M. X. Luo⁸⁶, T. Luo ^12,h, X. L. Luo ^1,64, Z. Y. Lv ²³, X. R. Lyu ^70,p, Y. F. Lyu ⁴⁷, Y. H. Lyu ⁸⁷, F. C. Ma ⁴⁴, H. L. Ma ¹, Heng Ma ^27,j, J. L. Ma ^1,70, L. L. Ma ⁵⁴, L. R. Ma ⁷², Q. M. Ma ¹, R. Q. Ma ^1,70, R. Y. Ma ²⁰, T. Ma ^77,64, X. T. Ma ^1,70, X. Y. Ma ^1,64, Y. M. Ma ³⁴, F. E. Maas ¹⁹, I. MacKay ⁷⁵, M. Maggiora ^80a,80c, S. Maity ³⁴, S. Malde ⁷⁵, Q. A. Malik ⁷⁹, H. X. Mao ^42,l,m, Y. J. Mao ^50,i, Z. P. Mao ¹, S. Marcello ^80a,80c, A. Marshall ⁶⁹, F. M. Melendi ^31a,31b, Y. H. Meng ⁷⁰, Z. X. Meng ⁷², G. Mezzadri ^31a, H. Miao ^1,70, T. J. Min ⁴⁶, R. E. Mitchell ²⁹, X. H. Mo ^1,64,70, B. Moses ²⁹, N. Yu. Muchnoi ^4,d, J. Muskalla ³⁹, Y. Nefedov ⁴⁰, F. Nerling ^19,f, H. Neuwirth ⁷⁴, Z. Ning ^1,64, S. Nisar ³³, Q. L. Niu ^42,l,m, W. D. Niu ^12,h, Y. Niu ⁵⁴, C. Normand ⁶⁹, S. L. Olsen ^11,70, Q. Ouyang ^1,64,70, S. Pacetti ^30b,30c, X. Pan ⁶⁰, Y. Pan ⁶², A. Pathak ¹¹, Y. P. Pei ^77,64, M. Pelizaeus ³, G. L. Peng ^77,64, H. P. Peng ^77,64, X. J. Peng ^42,l,m, Y. Y. Peng ^42,l,m, K. Peters ^13,f, K. Petridis ⁶⁹, J. L. Ping ⁴⁵, R. G. Ping ^1,70, S. Plura ³⁹, V. Prasad ³⁸, L. Pöpping ³, F. Z. Qi ¹, H. R. Qi ⁶⁷, M. Qi ⁴⁶, S. Qian ^1,64, W. B. Qian ⁷⁰, C. F. Qiao ⁷⁰, J. H. Qiao ²⁰, J. J. Qin ⁷⁸, J. L. Qin ⁶⁰, L. Q. Qin ¹⁴, L. Y. Qin ^77,64, P. B. Qin ⁷⁸, X. P. Qin ⁴³, X. S. Qin ⁵⁴, Z. H. Qin ^1,64, J. F. Qiu ¹, Z. H. Qu ⁷⁸, J. Rademacker ⁶⁹, C. F. Redmer ³⁹, A. Rivetti ^80c, M. Rolo ^80c, G. Rong ^1,70, S. S. Rong ^1,70, F. Rosini ^30b,30c, Ch. Rosner ¹⁹, M. Q. Ruan ^1,64, N. Salone ^48,r, A. Sarantsev ^40,e, Y. Schelhaas ³⁹, M. Schernau ³⁶, K. Schoenning ⁸¹, M. Scodeggio ^31a, W. Shan ²⁶, X. Y. Shan ^77,64, Z. J. Shang ^42,l,m, J. F. Shangguan ¹⁷, L. G. Shao ^1,70, M. Shao ^77,64, C. P. Shen ^12,h, H. F. Shen ^1,9, W. H. Shen ⁷⁰, X. Y. Shen ^1,70, B. A. Shi ⁷⁰, Ch. Y. Shi ^85,c, H. Shi ^77,64, J. L. Shi ^8,q, J. Y. Shi ¹, M. H. Shi ⁸⁷, S. Y. Shi ⁷⁸, X. Shi ^1,64, H. L. Song ^77,64, J. J. Song ²⁰, M. H. Song ⁴², T. Z. Song ⁶⁵, W. M. Song ³⁸, Y. X. Song ^50,i,n, Zirong Song ^27,j, S. Sosio ^80a,80c, S. Spataro ^80a,80c, S. Stansilaus ⁷⁵, F. Stieler ³⁹, M. Stolte ³, S. S. Su⁴⁴, G. B. Sun ⁸², G. X. Sun ¹, H. Sun ⁷⁰, H. K. Sun ¹, J. F. Sun ²⁰, K. Sun ⁶⁷, L. Sun ⁸², R. Sun ⁷⁷, S. S. Sun ^1,70, T. Sun ^56,g, W. Y. Sun ⁵⁵, Y. C. Sun ⁸², Y. H. Sun ³², Y. J. Sun ^77,64, Y. Z. Sun ¹, Z. Q. Sun ^1,70, Z. T. Sun ⁵⁴, H. Tabaharizato ¹, C. J. Tang⁵⁹, G. Y. Tang ¹, J. Tang ⁶⁵, J. J. Tang ^77,64, L. F. Tang ⁴³, Y. A. Tang ⁸², Z. H. Tang ^1,70, L. Y. Tao ⁷⁸, M. Tat ⁷⁵, J. X. Teng ^77,64, J. Y. Tian ^77,64, W. H. Tian ⁶⁵, Y. Tian ³⁴, Z. F. Tian ⁸², I. Uman ^68b, E. van der Smagt ³, B. Wang ⁶⁵, Bin Wang ¹, Bo Wang ^77,64, C. Wang ^42,l,m, Chao Wang ²⁰, Cong Wang ²³, D. Y. Wang ^50,i, H. J. Wang ^42,l,m, H. R. Wang ⁸⁴, J. Wang ¹⁰, J. J. Wang ⁸², J. P. Wang ³⁷, K. Wang ^1,64, L. L. Wang ¹, L. W. Wang ³⁸, M. Wang ⁵⁴, Mi Wang ^77,64, N. Y. Wang ⁷⁰, S. Wang ^42,l,m, Shun Wang ⁶³, T. Wang ^12,h, T. J. Wang ⁴⁷, W. Wang ⁶⁵, W. P. Wang ³⁹, X. F. Wang ^42,l,m, X. L. Wang ^12,h, X. N. Wang ^1,70, Xin Wang ^27,j, Y. Wang ¹, Y. D. Wang ⁴⁹, Y. F. Wang ^1,9,70, Y. H. Wang ^42,l,m, Y. J. Wang ^77,64, Y. L. Wang ²⁰, Y. N. Wang ⁴⁹, Yanning Wang ⁸², Yaqian Wang ¹⁸, Yi Wang ⁶⁷, Yuan Wang ^18,34, Z. Wang ^1,64, Z. L. Wang ², Z. Q. Wang ^12,h, Z. Y. Wang ^1,70, Zhi Wang ⁴⁷, Ziyi Wang ⁷⁰, D. Wei ⁴⁷, D. H. Wei ¹⁴, D. J. Wei ⁷², H. R. Wei ⁴⁷, F. Weidner ⁷⁴, H. R. Wen ³⁴, S. P. Wen ¹, U. Wiedner ³, G. Wilkinson ⁷⁵, M. Wolke⁸¹, J. F. Wu ^1,9, L. H. Wu ¹, L. J. Wu ²⁰, Lianjie Wu ²⁰, S. G. Wu ^1,70, S. M. Wu ⁷⁰, X. W. Wu ⁷⁸, Z. Wu ^1,64, H. L. Xia ^77,64, L. Xia ^77,64, B. H. Xiang ^1,70, D. Xiao ^42,l,m, G. Y. Xiao ⁴⁶, H. Xiao ⁷⁸, Y. L. Xiao ^12,h, Z. J. Xiao ⁴⁵, C. Xie ⁴⁶, K. J. Xie ^1,70, Y. Xie ⁵⁴, Y. G. Xie ^1,64, Y. H. Xie ⁶, Z. P. Xie ^77,64, T. Y. Xing ^1,70, D. B. Xiong ¹, C. J. Xu ⁶⁵, G. F. Xu ¹, H. Y. Xu ², Q. J. Xu ¹⁷, Q. N. Xu ³², T. D. Xu ⁷⁸, X. P. Xu ⁶⁰, Y. Xu ^12,h, Y. C. Xu ⁸⁴, Z. S. Xu ⁷⁰, F. Yan ²⁴, L. Yan ^12,h, W. B. Yan ^77,64, W. C. Yan ⁸⁷, W. H. Yan ⁶, W. P. Yan ²⁰, X. Q. Yan ^12,h, Y. Y. Yan ⁶⁶, H. J. Yang ^56,g, H. L. Yang ³⁸, H. X. Yang ¹, J. H. Yang ⁴⁶, R. J. Yang ²⁰, X. Y. Yang ⁷², Y. Yang ^12,h, Y. H. Yang ⁴⁷, Y. M. Yang ⁸⁷, Y. Q. Yang ¹⁰, Y. Z. Yang ²⁰, Youhua Yang ⁴⁶, Z. Y. Yang ⁷⁸, Z. P. Yao ⁵⁴, M. Ye ^1,64, M. H. Ye ^9,a, Z. J. Ye ^61,k, Junhao Yin ⁴⁷, Z. Y. You ⁶⁵, B. X. Yu ^1,64,70, C. X. Yu ⁴⁷, G. Yu ¹³, J. S. Yu ^27,j, L. W. Yu ^12,h, T. Yu ⁷⁸, X. D. Yu ^50,i, Y. C. Yu ⁸⁷, Yongchao Yu ⁴², C. Z. Yuan ^1,70, H. Yuan ^1,70, J. Yuan ³⁸, Jie Yuan ⁴⁹, L. Yuan ², M. K. Yuan ^12,h, S. H. Yuan ⁷⁸, Y. Yuan ^1,70, C. X. Yue ⁴³, Ying Yue ²⁰, A. A. Zafar ⁷⁹, F. R. Zeng ⁵⁴, S. H. Zeng ⁶⁹, X. Zeng ^12,h, Y. J. Zeng ^1,70, Yujie Zeng ⁶⁵, Y. C. Zhai ⁵⁴, Y. H. Zhan ⁶⁵, B. L. Zhang ^1,70, B. X. Zhang ^1,a, D. H. Zhang ⁴⁷, G. Y. Zhang ²⁰, Gengyuan Zhang ^1,70, H. Zhang ^77,64, H. C. Zhang ^1,64,70, H. H. Zhang ⁶⁵, H. Q. Zhang ^1,64,70, H. R. Zhang ^77,64, H. Y. Zhang ^1,64, Han Zhang ⁸⁷, J. Zhang ⁶⁵, J. J. Zhang ⁵⁷, J. L. Zhang ²¹, J. Q. Zhang ⁴⁵, J. S. Zhang ^12,h, J. W. Zhang ^1,64,70, J. X. Zhang ^42,l,m, J. Y. Zhang ¹, J. Z. Zhang ^1,70, Jianyu Zhang ⁷⁰, Jin Zhang ⁵², Jiyuan Zhang ^12,h, L. M. Zhang ⁶⁷, Lei Zhang ⁴⁶, N. Zhang ³⁸, P. Zhang ^1,9, Q. Zhang ²⁰, Q. Y. Zhang ³⁸, Q. Z. Zhang ⁷⁰, R. Y. Zhang ^42,l,m, S. H. Zhang ^1,70, S. N. Zhang ⁷⁵, Shulei Zhang ^27,j, X. M. Zhang ¹, X. Y. Zhang ⁵⁴, Y. Zhang ¹, Y. T. Zhang ⁸⁷, Y. H. Zhang ^1,64, Y. P. Zhang ^77,64, Yu Zhang ⁷⁸, Z. Zhang ³⁴, Z. D. Zhang ¹, Z. H. Zhang ¹, Z. L. Zhang ³⁸, Z. X. Zhang ²⁰, Z. Y. Zhang ⁸², Zh. Zh. Zhang ²⁰, Zhilong Zhang ⁶⁰, Ziyang Zhang ⁴⁹, Ziyu Zhang ⁴⁷, G. Zhao ¹, J.-P. Zhao ⁷⁰, J. Y. Zhao ^1,70, J. Z. Zhao ^1,64, L. Zhao ¹, Lei Zhao ^77,64, M. G. Zhao ⁴⁷, R. P. Zhao ⁷⁰, S. J. Zhao ⁸⁷, Y. B. Zhao ^1,64, Y. L. Zhao ⁶⁰, Y. P. Zhao ⁴⁹, Y. X. Zhao ^34,70, Z. G. Zhao ^77,64, A. Zhemchugov ^40,b, B. Zheng ⁷⁸, B. M. Zheng ³⁸, J. P. Zheng ^1,64, W. J. Zheng ^1,70, W. Q. Zheng ¹⁰, X. R. Zheng ²⁰, Y. H. Zheng ^70,p, B. Zhong ⁴⁵, C. Zhong ²⁰, H. Zhou ^39,54,o, J. Q. Zhou ³⁸, S. Zhou ⁶, X. Zhou ⁸², X. K. Zhou ⁶, X. R. Zhou ^77,64, X. Y. Zhou ⁴³, Y. X. Zhou ⁸⁴, Y. Z. Zhou ²⁰, A. N. Zhu ⁷⁰, J. Zhu ⁴⁷, K. Zhu ¹, K. J. Zhu ^1,64,70, K. S. Zhu ^12,h, L. X. Zhu ⁷⁰, Lin Zhu ²⁰, S. H. Zhu ⁷⁶, T. J. Zhu ^12,h, W. D. Zhu ^12,h, W. J. Zhu ¹, W. Z. Zhu ²⁰, Y. C. Zhu ^77,64, Z. A. Zhu ^1,70, X. Y. Zhuang ⁴⁷, M. Zhuge ⁵⁴, J. H. Zou ¹, and J. Zu ³⁴ (BESIII Collaboration)

¹Institute of High Energy Physics, Beijing 100049, People’s Republic of China
²Beihang University, Beijing 100191, People’s Republic of China
³Bochum Ruhr-University, D-44780 Bochum, Germany
⁴Budker Institute of Nuclear Physics SB RAS (BINP), Novosibirsk 630090, Russia
⁵Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
⁶Central China Normal University, Wuhan 430079, People’s Republic of China
⁷Central South University, Changsha 410083, People’s Republic of China
⁸Chengdu University of Technology, Chengdu 610059, People’s Republic of China
⁹China Center of Advanced Science and Technology, Beijing 100190, People’s Republic of China
¹⁰China University of Geosciences, Wuhan 430074, People’s Republic of China
¹¹Chung-Ang University, Seoul, 06974, Republic of Korea
¹²Fudan University, Shanghai 200433, People’s Republic of China
¹³GSI Helmholtzcentre for Heavy Ion Research GmbH, D-64291 Darmstadt, Germany
¹⁴Guangxi Normal University, Guilin 541004, People’s Republic of China
¹⁵Guangxi University, Nanning 530004, People’s Republic of China
¹⁶Guangxi University of Science and Technology, Liuzhou 545006, People’s Republic of China
¹⁷Hangzhou Normal University, Hangzhou 310036, People’s Republic of China
¹⁸Hebei University, Baoding 071002, People’s Republic of China
¹⁹Helmholtz Institute Mainz, Staudinger Weg 18, D-55099 Mainz, Germany
²⁰Henan Normal University, Xinxiang 453007, People’s Republic of China
²¹Henan University, Kaifeng 475004, People’s Republic of China
²²Henan University of Science and Technology, Luoyang 471003, People’s Republic of China
²³Henan University of Technology, Zhengzhou 450001, People’s Republic of China
²⁴Hengyang Normal University, Hengyang 421001, People’s Republic of China
²⁵Huangshan College, Huangshan 245000, People’s Republic of China
²⁶Hunan Normal University, Changsha 410081, People’s Republic of China
²⁷Hunan University, Changsha 410082, People’s Republic of China
²⁸Indian Institute of Technology Madras, Chennai 600036, India
²⁹Indiana University, Bloomington, Indiana 47405, USA
^30aINFN Laboratori Nazionali di Frascati, I-00044, Frascati, Italy
^30bINFN Sezione di Perugia, I-06100, Perugia, Italy
^30cUniversity of Perugia, I-06100, Perugia, Italy
^31aINFN Sezione di Ferrara, I-44122, Ferrara, Italy
^31bUniversity of Ferrara, I-44122, Ferrara, Italy
³²Inner Mongolia University, Hohhot 010021, People’s Republic of China
³³Institute of Business Administration, University Road, Karachi 75270 Pakistan
³⁴Institute of Modern Physics, Lanzhou 730000, People’s Republic of China
³⁵Institute of Physics and Technology, Mongolian Academy of Sciences, Peace Avenue 54B, Ulaanbaatar 13330, Mongolia
³⁶Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica 1000000, Chile
³⁷Jiangsu Ocean University, Lianyungang 222000, People’s Republic of China
³⁸Jilin University, Changchun 130012, People’s Republic of China
³⁹Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany
⁴⁰Joint Institute for Nuclear Research, 141980 Dubna, Moscow region, Russia
⁴¹Justus-Liebig-Universitaet Giessen, II. Physikalisches Institut, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
⁴²Lanzhou University, Lanzhou 730000, People’s Republic of China
⁴³Liaoning Normal University, Dalian 116029, People’s Republic of China
⁴⁴Liaoning University, Shenyang 110036, People’s Republic of China
⁴⁵Nanjing Normal University, Nanjing 210023, People’s Republic of China
⁴⁶Nanjing University, Nanjing 210093, People’s Republic of China
⁴⁷Nankai University, Tianjin 300071, People’s Republic of China
⁴⁸National Centre for Nuclear Research, Warsaw 02-093, Poland
⁴⁹North China Electric Power University, Beijing 102206, People’s Republic of China
⁵⁰Peking University, Beijing 100871, People’s Republic of China
⁵¹Qufu Normal University, Qufu 273165, People’s Republic of China
⁵²Renmin University of China, Beijing 100872, People’s Republic of China
⁵³Shandong Normal University, Jinan 250014, People’s Republic of China
⁵⁴Shandong University, Jinan 250100, People’s Republic of China
⁵⁵Shandong University of Technology, Zibo 255000, People’s Republic of China
⁵⁶Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China
⁵⁷Shanxi Normal University, Linfen 041004, People’s Republic of China
⁵⁸Shanxi University, Taiyuan 030006, People’s Republic of China
⁵⁹Sichuan University, Chengdu 610064, People’s Republic of China
⁶⁰Soochow University, Suzhou 215006, People’s Republic of China
⁶¹South China Normal University, Guangzhou 510006, People’s Republic of China
⁶²Southeast University, Nanjing 211100, People’s Republic of China
⁶³Southwest University of Science and Technology, Mianyang 621010, People’s Republic of China
⁶⁴State Key Laboratory of Particle Detection and Electronics, Beijing 100049, Hefei 230026, People’s Republic of China
⁶⁵Sun Yat-Sen University, Guangzhou 510275, People’s Republic of China
⁶⁶Suranaree University of Technology, University Avenue 111, Nakhon Ratchasima 30000, Thailand
⁶⁷Tsinghua University, Beijing 100084, People’s Republic of China
^68aTurkish Accelerator Center Particle Factory Group, Istinye University, 34010, Istanbul, Turkey
^68bNear East University, Nicosia, North Cyprus, 99138, Mersin 10, Turkey
⁶⁹University of Bristol, H H Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL, United Kingdom
⁷⁰University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
⁷¹University of Hawaii, Honolulu, Hawaii 96822, USA
⁷²University of Jinan, Jinan 250022, People’s Republic of China
⁷³University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
⁷⁴University of Muenster, Wilhelm-Klemm-Strasse 9, 48149 Muenster, Germany
⁷⁵University of Oxford, Keble Road, Oxford OX13RH, United Kingdom
⁷⁶University of Science and Technology Liaoning, Anshan 114051, People’s Republic of China
⁷⁷University of Science and Technology of China, Hefei 230026, People’s Republic of China
⁷⁸University of South China, Hengyang 421001, People’s Republic of China
⁷⁹University of the Punjab, Lahore 54590, Pakistan
^80aUniversity of Turin and INFN, University of Turin, I-10125, Turin, Italy
^80bUniversity of Eastern Piedmont, I-15121, Alessandria, Italy
^80cINFN, I-10125, Turin, Italy
⁸¹Uppsala University, Box 516, SE-75120 Uppsala, Sweden
⁸²Wuhan University, Wuhan 430072, People’s Republic of China
⁸³Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an, Shaanxi 710049, People’s Republic of China
⁸⁴Yantai University, Yantai 264005, People’s Republic of China
⁸⁵Yunnan University, Kunming 650500, People’s Republic of China
⁸⁶Zhejiang University, Hangzhou 310027, People’s Republic of China
⁸⁷Zhengzhou University, Zhengzhou 450001, People’s Republic of China

^*Full author list given at the end of the letter.
^aDeceased.
^bAlso at the Moscow Institute of Physics and Technology, Moscow 141700, Russia.
^cAlso at the Functional Electronics Laboratory, Tomsk State University, Tomsk, 634050, Russia.
^dAlso at the Novosibirsk State University, Novosibirsk, 630090, Russia.
^eAlso at the NRC “Kurchatov Institute”, PNPI, 188300, Gatchina, Russia.
^fAlso at Goethe University Frankfurt, 60323 Frankfurt am Main, Germany.
^gAlso at Key Laboratory for Particle Physics, Astrophysics and Cosmology, Ministry of Education; Shanghai Key Laboratory for Particle Physics and Cosmology; Institute of Nuclear and Particle Physics, Shanghai 200240, People’s Republic of China.
^hAlso at Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443, People’s Republic of China.
ⁱAlso at State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, People’s Republic of China.
^jAlso at School of Physics and Electronics, Hunan University, Changsha 410082, China.
^kAlso at Guangdong Provincial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China Normal University, Guangzhou 510006, China.
^lAlso at MOE Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, People’s Republic of China.
^mAlso at Lanzhou Center for Theoretical Physics, Lanzhou University, Lanzhou 730000, People’s Republic of China.
ⁿAlso at Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
^oAlso at Helmholtz Institute Mainz, Staudinger Weg 18, D-55099 Mainz, Germany.
^pAlso at Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China.
^qAlso at Applied Nuclear Technology in Geosciences Key Laboratory of Sichuan Province, Chengdu University of Technology, Chengdu 610059, People’s Republic of China.
^rCurrently at University of Silesia in Katowice, Institute of Physics, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.

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Phys. Rev. D 113, L091102 – Published 26 May, 2026

DOI: https://doi.org/10.1103/8wdg-kwqj

Abstract

Using $(10087 \pm 44) \times 10^{6} J / ψ$ events collected with the BESIII detector, we perform the first amplitude analysis of the process $J / ψ \to γ η π^{0}$ . The decay is dominated by the intermediate processes $J / ψ \to π^{0} b_{1} (1235)^{0} \to γ η π^{0}$ , $J / ψ \to π^{0} ρ (1450)^{0} \to γ η π^{0}$ and $J / ψ \to η h_{1} (1170) \to γ η π^{0}$ . Contributions from $J / ψ \to γ a_{0} (980)^{0} \to γ η π^{0}$ , $J / ψ \to γ a_{2} (1320)^{0} \to γ η π^{0}$ and $J / ψ \to γ a_{2} (1700)^{0} \to γ η π^{0}$ are observed with a statistical significance exceeding $5 σ$ , constituting the first observation of radiative transitions of $J / ψ$ to isospin-triplet scalar mesons. The total branching fraction of $J / ψ \to γ η π^{0}$ is measured to be $(25.7 \pm 0.3 \pm 1.5) \times 10^{- 6}$ , where the first uncertainty is statistical and the second systematic. This result is consistent with the previous measurement, with the precision improved by more than a factor of two.

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References (57)

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Phys. Rev. D 113, L091102– Published 26 May, 2026

Vol. 113, Iss. 9 — 1 May 2026

Received 25 March 2026
Accepted 29 April 2026

DOI: https://doi.org/10.1103/8wdg-kwqj

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Amplitude analysis of the isospin-violating decay $J / ψ \to γ η π^{0}$

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Amplitude analysis of the isospin-violating decay J/ψ→γηπ0

Abstract

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Amplitude analysis of the isospin-violating decay $J / ψ \to γ η π^{0}$