Open Access

Improved search for $ψ (3770) \to γ η_{c} (1 S, 2 S)$ radiative transitions

M. Ablikim ¹, M. N. Achasov ^4,d, P. Adlarson ⁸⁵, X. C. Ai ⁹¹, C. S. Akondi ^32a,32b, R. Aliberti ⁴⁰, A. Amoroso ^84a,84c, Q. An^80,67,a, M. S. Anderson ⁴⁰ et al. (BESIII Collaboration)

M. S. Anderson ⁴⁰, Y. Bai ⁶⁵, O. Bakina ⁴¹, H. R. Bao ⁷³, X. L. Bao ⁵¹, M. Barbagiovanni ^84c, V. Batozskaya ^1,50, K. Begzsuren³⁶, N. Berger ⁴⁰, M. Berlowski ⁵⁰, M. B. Bertani ^31a, D. Bettoni ^32a, F. Bianchi ^84a,84c, E. Bianco^84a,84c, A. Bortone ^84a,84c, I. Boyko ⁴¹, R. A. Briere ⁵, A. Brueggemann ⁷⁷, D. Cabiati ^84a,84c, H. Cai ⁸⁶, M. H. Cai ^43,l,m, X. Cai ^1,67, A. Calcaterra ^31a, G. F. Cao ^1,73, N. Cao ^1,73, S. A. Cetin ^71a, X. Y. Chai ^52,i, J. F. Chang ^1,67, T. T. Chang ⁴⁹, G. R. Che ⁴⁹, Y. Z. Che ^1,67,73, C. H. Chen ¹⁰, Chao Chen ¹, G. Chen ¹, H. S. Chen ^1,73, H. Y. Chen ²¹, M. L. Chen ^1,67,73, S. J. Chen ⁴⁸, S. M. Chen ⁷⁰, T. Chen ^1,73, W. Chen ⁵¹, X. R. Chen ^35,73, X. T. Chen ^1,73, X. Y. Chen ^13,h, Y. B. Chen ^1,67, Y. Q. Chen ¹⁷, Z. K. Chen ⁶⁸, J. Cheng ⁵¹, L. N. Cheng ⁴⁹, S. K. Choi ¹¹, X. Chu ^13,h, G. Cibinetto ^32a, F. Cossio ^84c, J. Cottee-Meldrum ⁷², H. L. Dai ^1,67, J. P. Dai ⁸⁹, X. C. Dai ⁷⁰, A. Dbeyssi²⁰, R. E. de Boer ³, D. Dedovich ⁴¹, Z. Y. Deng ¹, A. Denig ⁴⁰, I. Denisenko ⁴¹, M. Destefanis ^84a,84c, F. De Mori ^84a,84c, E. Di Fiore ^32a,32b, X. X. Ding ^52,i, Y. Ding ⁴⁵, Y. X. Ding ³³, J. Dong ^1,67, L. Y. Dong ^1,73, M. Y. Dong ^1,67,73, X. Dong ⁸⁶, Z. J. Dong ⁶⁸, M. C. Du ¹, S. X. Du ⁹¹, Shaoxu Du ^13,h, X. L. Du ^13,h, Y. Q. Du ⁸⁶, Y. Y. Duan ⁶³, Z. H. Duan ⁴⁸, P. Egorov ^41,b, G. F. Fan ⁴⁸, J. J. Fan ²¹, K. X. Fan ⁶⁸, Y. H. Fan ⁵¹, J. Fang ^1,67, Jin Fang ⁶⁸, S. S. Fang ^1,73, W. X. Fang ¹, Y. Q. Fang ^1,67,a, L. Fava ^84b,84c, F. Feldbauer ³, G. Felici ^31a, C. Q. Feng ^80,67, J. H. Feng ¹⁷, Q. X. Feng ^43,l,m, Y. T. Feng ^80,67, M. Fritsch ³, C. D. Fu ¹, J. L. Fu ⁷³, Y. W. Fu ^1,73, H. Gao ⁷³, Xu Gao ³⁹, Y. Gao ^80,67, Y. N. Gao ^52,i, Y. Y. Gao ³³, Yunong Gao ²¹, Z. Gao ⁴⁹, S. Garbolino ^84c, I. Garzia ^32a,32b, L. Ge ⁶⁵, P. T. Ge ²¹, Z. W. Ge ⁴⁸, C. Geng ⁶⁸, A. Gilman ⁷⁸, K. Goetzen ¹⁴, J. Gollub ³, J. B. Gong ^1,73, J. D. Gong ³⁹, L. Gong ⁴⁵, W. X. Gong ^1,67, W. Gradl ⁴⁰, M. Greco ^84a,84c, M. D. Gu ⁵⁸, M. H. Gu ^1,67, C. Y. Guan ^1,73, A. Q. Guo ³⁵, H. Guo ⁵⁷, J. N. Guo ^13,h, L. B. Guo ⁴⁷, M. J. Guo ⁵⁷, R. P. Guo ⁵⁶, X. Guo ⁵⁷, Y. P. Guo ^13,h, Z. Guo ^80,67, A. Guskov ^41,b, J. Gutierrez ³⁰, J. Y. Han ^80,67, T. T. Han ⁵⁵, X. Han ^80,67, F. Hanisch ³, J. Y. Hao ²¹, K. D. Hao ^80,67, X. Q. Hao ²¹, F. A. Harris ⁷⁴, C. Z. He ^52,i, K. K. He ^48,18, K. L. He ^1,73, F. H. Heinsius ³, C. H. Heinz ⁴⁰, Y. K. Heng ^1,67,73, C. Herold ⁶⁹, N. D. Hoffman ¹², P. C. Hong ³⁹, G. Y. Hou ^1,73, X. T. Hou ^1,73, Y. R. Hou ⁷³, Z. L. Hou ¹, H. M. Hu ^1,73, J. F. Hu ^64,k, Q. P. Hu ^80,67, S. L. Hu ^13,h, T. Hu ^1,67,73, Y. Hu ¹, Y. X. Hu ⁸⁶, Z. M. Hu ⁶⁸, G. S. Huang ^80,67, K. X. Huang ⁶⁸, L. Q. Huang ^35,73, P. Huang ⁴⁸, X. T. Huang ⁵⁷, Y. P. Huang ¹, Y. S. Huang ⁶⁸, T. Hussain ⁸³, N. Hüsken ⁴⁰, N. in der Wiesche ⁷⁷, Q. Ji ¹, Q. P. Ji ²¹, W. Ji ^1,73, X. B. Ji ^1,73, X. L. Ji ^1,67, Y. Y. Ji ¹, L. K. Jia ⁷³, X. Q. Jia ⁵⁷, D. Jiang ^1,73, S. J. Jiang ¹⁰, X. S. Jiang ^1,67,73, Y. Jiang ⁷³, J. B. Jiao ⁵⁷, J. K. Jiao ³⁹, Z. Jiao ²⁶, L. C. L. Jin ¹, S. Jin ⁴⁸, Y. Jin ⁷⁵, M. Q. Jing ⁵⁸, X. M. Jing ⁷³, T. Johansson ⁸⁵, S. Kabana ³⁷, X. L. Kang ¹⁰, X. S. Kang ⁴⁵, B. C. Ke ⁹¹, V. Khachatryan ³⁰, A. Khoukaz ⁷⁷, O. B. Kolcu ^71a, B. Kopf ³, L. Kröger ⁷⁷, L. Krümmel³, Y. Y. Kuang ⁸², M. Kuessner ¹², X. Kui ^1,73, N. Kumar ²⁹, A. Kupsc ^50,85, W. Kühn ⁴², Q. Lan ⁸², T. T. Lei ^80,67, M. Lellmann ⁴⁰, T. Lenz ⁴⁰, C. Li ⁵³, C. H. Li ⁴⁷, C. K. Li ⁴⁹, Chunkai Li ²², Cong Li ⁴⁹, D. M. Li ⁹¹, F. Li ^1,67, G. Li ¹, H. B. Li ^1,73, H. J. Li ²¹, H. L. Li ⁹¹, H. N. Li ^64,k, H. P. Li ⁴⁹, Hui Li ⁴⁹, J. N. Li ³³, J. S. Li ⁶⁸, J. W. Li ⁵⁷, K. Li ¹, K. L. Li ^43,l,m, L. J. Li ^1,73, L. K. Li ²⁷, Lei Li ⁵⁴, M. H. Li ⁴⁹, M. R. Li ^1,73, M. T. Li ⁵⁷, P. L. Li ⁷³, P. R. Li ^43,l,m, Q. M. Li ^1,73, Q. X. Li ⁵⁷, R. Li ^19,35, S. Li ⁹¹, S. X. Li ⁹¹, S. Y. Li ⁹¹, Shanshan Li ^28,j, T. Li ⁵⁷, T. Y. Li ⁴⁹, W. D. Li ^1,73, W. G. Li ^1,a, X. Li ^1,73, X. H. Li ^80,67, X. K. Li ^52,i, X. L. Li ⁵⁷, X. Y. Li ^80,67, X. Z. Li ⁶⁸, Y. H. Li ⁴⁹, Y. B. Li ⁸⁷, Y. C. Li ⁶⁸, Y. G. Li ⁷³, Y. P. Li ³⁹, Yi Li ²¹, Z. H. Li ⁴³, Z. J. Li ⁶⁸, Z. L. Li ⁹¹, Z. X. Li ⁴⁹, Z. Y. Li ⁸⁹, Zaiyi Li ^1,73, C. Liang ⁴⁸, H. Liang ^80,67, Y. F. Liang ⁶², Y. T. Liang ^35,73, Z. Z. Liang ⁶⁸, G. R. Liao ¹⁵, L. B. Liao ⁶⁸, M. H. Liao ⁶⁸, Y. P. Liao ^1,73, J. Libby ²⁹, A. Limphirat ⁶⁹, C. C. Lin ⁶³, C. X. Lin ³⁵, D. X. Lin ^35,73, T. Lin ¹, B. J. Liu ¹, B. X. Liu ⁸⁶, C. Liu ³⁹, C. X. Liu ¹, F. Liu ¹, F. H. Liu ⁶¹, Feng Liu ⁶, G. M. Liu ^64,k, H. Liu ^43,l,m, H. B. Liu ¹⁶, H. M. Liu ^1,73, Huihui Liu ²³, J. B. Liu ^80,67, J. J. Liu ²², K. Liu ^43,l,m, K. Y. Liu ⁴⁵, Ke Liu ²⁴, Kun Liu ⁸², L. Liu ⁴³, L. C. Liu ⁴⁹, Lu Liu ⁴⁹, M. H. Liu ³⁹, P. L. Liu ⁵⁷, Q. Liu ⁷³, S. B. Liu ^80,67, T. Liu ¹, W. T. Liu ⁴⁴, X. Liu ^43,l,m, X. K. Liu ^43,l,m, X. L. Liu ^13,h, X. P. Liu ^13,h, X. T. Liu ²², X. Y. Liu ⁸⁶, Y. Liu ^43,l,m, Y. B. Liu ⁴⁹, Yi Liu ⁹¹, Z. A. Liu ^1,67,73, Z. D. Liu ⁸⁷, Z. Q. Liu ⁵⁷, Z. X. Liu ¹, Z. Y. Liu ⁴³, X. C. Lou ^1,67,73, H. J. Lu ²⁶, J. G. Lu ^1,67, X. L. Lu ¹⁷, Y. Lu ⁷, Y. H. Lu ^1,73, Y. P. Lu ^1,67, Z. H. Lu ^1,73, C. L. Luo ⁴⁷, J. R. Luo ⁶⁸, J. S. Luo ^1,73, M. X. Luo⁹⁰, T. Luo ^13,h, X. L. Luo ^1,67, Z. Y. Lv ²⁴, X. R. Lyu ^73,p, Y. F. Lyu ⁴⁹, Y. H. Lyu ⁹¹, C. L. Ma ^1,73, F. C. Ma ⁴⁵, H. L. Ma ¹, Heng Ma ^28,j, J. L. Ma ^1,73, L. L. Ma ⁵⁷, L. R. Ma ⁷⁵, Q. M. Ma ¹, R. Q. Ma ^1,73, R. Y. Ma ²¹, T. Ma ^80,67, X. T. Ma ^1,73, X. Y. Ma ^1,67, F. E. Maas ²⁰, I. MacKay ⁷⁸, M. Maggiora ^84a,84c, S. Maity ³⁵, S. Malde ⁷⁸, Q. A. Malik ⁸³, L. M. Mansur ⁴⁰, Y. J. Mao ^52,i, Z. P. Mao ¹, S. Marcello ^84a,84c, A. Marshall ⁷², F. M. Melendi ^32a,32b, Y. H. Meng ⁷³, Z. X. Meng ⁷⁵, G. Mezzadri ^32a, H. Miao ^1,73, T. J. Min ⁴⁸, R. E. Mitchell ³⁰, X. H. Mo ^1,67,73, A. F. Mohammad ⁴⁸, B. Moses ³⁰, N. Yu. Muchnoi ^4,d, J. Muskalla ⁴⁰, Y. Nefedov ⁴¹, F. Nerling ^20,f, H. Neuwirth ⁷⁷, Z. Ning ^1,67, S. Nisar ³⁴, Q. L. Niu ^43,l,m, W. D. Niu ^13,h, Y. Niu ⁵⁷, C. Normand ⁷², S. L. Olsen ^11,73, Q. Ouyang ^1,67,73, I. V. Ovtin ⁴, S. Pacetti ^31b,31c, Y. Pan ⁶⁵, C. Y. Pang ¹⁵, A. Pathak ¹¹, Y. P. Pei ^80,67, M. Pelizaeus ³, G. L. Peng ^80,67, H. P. Peng ^80,67, X. J. Peng ^43,l,m, Y. Y. Peng ^43,l,m, K. Peters ^14,f, K. Petridis ⁷², J. L. Ping ⁴⁷, R. G. Ping ^1,73, S. Plura ⁴⁰, V. Prasad ³⁹, L. Pöpping ³, F. Z. Qi ¹, H. R. Qi ⁷⁰, L. Y. Qian ^1,73, S. Qian ^1,67, W. B. Qian ⁷³, C. F. Qiao ⁷³, J. H. Qiao ²¹, J. J. Qin ⁸², J. L. Qin ⁶³, L. Q. Qin ¹⁵, L. Y. Qin ^80,67, P. B. Qin ⁸², X. P. Qin ⁴⁴, X. S. Qin ⁵⁷, Z. H. Qin ^1,67, J. F. Qiu ¹, Z. H. Qu ⁸², J. Rademacker ⁷², K. Ravindran ⁷⁶, C. F. Redmer ⁴⁰, A. Rivetti ^84c, M. Rolo ^84c, G. Rong ^1,73, S. S. Rong ^1,73, F. Rosini ^31b,31c, Ch. Rosner ²⁰, M. Q. Ruan ^1,67, W. R. Ruangyoo ⁶⁹, N. Salone ⁸¹, A. Sarantsev ^41,e, Y. Schelhaas ⁴⁰, M. Schernau ³⁷, K. Schoenning ⁸⁵, M. Scodeggio ^32a, W. Shan ²⁷, X. Y. Shan ^80,67, Z. J. Shang ^43,l,m, J. F. Shangguan ¹⁸, L. G. Shao ^1,73, M. Shao ^80,67, C. P. Shen ^13,h, H. F. Shen ³⁰, W. H. Shen ⁷³, X. Y. Shen ^1,73, B. A. Shi ⁷³, Ch. Y. Shi ^89,c, H. Shi ^80,67, J. L. Shi ^8,q, J. Y. Shi ¹, M. H. Shi ⁹¹, S. Shi ^1,73, S. Y. Shi ⁸², X. Shi ^1,67, X. D. Shi ¹, H. L. Song ^80,67, J. J. Song ²¹, M. H. Song ⁴³, T. Z. Song ⁶⁸, W. M. Song ³⁹, Y. X. Song ^52,i,n, Zirong Song ^28,j, S. Sosio ^84a,84c, S. Spataro ^84a,84c, S. Stansilaus ⁷⁸, F. Stieler ⁴⁰, M. Stolte ³, S. S Su ⁴⁵, G. B. Sun ⁸⁶, G. X. Sun ¹, H. Sun ⁷³, H. K. Sun ¹, J. F. Sun ²¹, K. Sun ⁷⁰, L. Sun ⁸⁶, R. Sun ⁸⁰, S. S. Sun ^1,73, W. Y. Sun ⁵⁸, Y. C. Sun ⁸⁶, Y. H. Sun ³³, Y. J. Sun ^80,67, Y. Z. Sun ¹, Z. Q. Sun ^1,73, Z. T. Sun ⁵⁷, H. Tabaharizato ¹, N. T. Tagsinsit ⁶⁹, C. J. Tang⁶², G. Y. Tang ¹, J. Tang ⁶⁸, J. J. Tang ^80,67, L. F. Tang ⁴⁴, Y. A. Tang ⁸⁶, Z. H. Tang ^1,73, L. Y. Tao ⁸², M. Tat ⁷⁸, J. X. Teng ^80,67, J. Y. Tian ^80,67, W. H. Tian ⁶⁸, Y. Tian ³⁵, Z. F. Tian ⁸⁶, K. Yu. Todyshev ⁴, I. Uman ^71b, E. van der Smagt ³, B. Wang ⁶⁸, Bin Wang ¹, Bo Wang ^80,67, C. Wang ^43,l,m, Chao Wang ²¹, Cong Wang ²⁴, D. Y. Wang ^52,i, F. K. Wang ⁶⁸, H. J. Wang ^43,l,m, H. R. Wang ⁸⁸, J. Wang ¹⁰, J. H. Wang ¹, J. J. Wang ⁸⁶, J. P. Wang ³⁸, K. Wang ^1,67, L. L. Wang ¹, L. W. Wang ³⁹, M. Wang ⁵⁷, Mi Wang ^80,67, N. Y. Wang ⁷³, P. Wang ²², S. Wang ^43,l,m, Shun Wang ⁶⁶, T. Wang ^13,h, W. Wang ⁶⁸, W. P. Wang ⁴⁰, X. F. Wang ^43,l,m, X. L. Wang ^13,h, X. N. Wang ^1,73, Xin Wang ^28,j, Y. Wang ¹, Y. D. Wang ⁵¹, Y. F. Wang ^1,9,73, Y. H. Wang ^43,l,m, Y. J. Wang ^80,67, Y. L. Wang ²¹, Y. N. Wang ⁵¹, Yanning Wang ⁸⁶, Yaqian Wang ¹⁹, Yi Wang ⁷⁰, Yuan Wang ^19,35, Z. Wang ^1,67, Z. L. Wang ², Z. Q. Wang ^13,h, Z. Y. Wang ^1,73, Zhi Wang ⁴⁹, Ziyi Wang ⁷³, D. Wei ⁴⁹, D. H. Wei ¹⁵, D. J. Wei ⁷⁵, H. R. Wei ⁴⁹, F. Weidner ⁷⁷, H. R. Wen ³⁵, S. P. Wen ¹, U. Wiedner ³, G. Wilkinson ⁷⁸, J. F. Wu ^1,9, L. H. Wu ¹, L. J. Wu ²¹, S. G. Wu ^1,73, S. M. Wu ⁷³, X. W. Wu ⁸², Z. Wu ^1,67, H. L. Xia ^80,67, L. Xia ^80,67, B. H. Xiang ^1,73, D. Xiao ^43,l,m, G. Y. Xiao ⁴⁸, H. Xiao ⁸², Y. L. Xiao ^13,h, Z. J. Xiao ⁴⁷, C. Xie ⁴⁸, K. J. Xie ^1,73, Y. Xie ⁵⁷, Y. G. Xie ^1,67, Y. H. Xie ⁶, Z. P. Xie ^80,67, T. Y. Xing ^1,73, D. B. Xiong ¹, G. F. Xu ¹, H. Y. Xu ², Q. J. Xu ¹⁸, Q. N. Xu ³³, T. D. Xu ⁸², X. P. Xu ⁶³, Y. Xu ^13,h, Y. C. Xu ⁸⁸, Z. S. Xu ⁷³, F. Yan ²⁵, L. Yan ^13,h, W. B. Yan ^80,67, W. C. Yan ⁹¹, W. H. Yan ⁶, X. Q. Yan ^13,h, Y. Y. Yan ⁶⁹, H. J. Yang ^59,g, H. L. Yang ³⁹, H. X. Yang ¹, J. H. Yang ⁴⁸, L. Y. Yang ^1,73, N. Yang ²¹, R. J. Yang ²¹, X. Y. Yang ⁷⁵, Y. Yang ^13,h, Y. G. Yang ⁵⁸, Y. H. Yang ⁴⁹, Y. M. Yang ⁹¹, Y. Q. Yang ¹⁰, Y. Z. Yang ²¹, Youhua Yang ⁴⁸, Z. Y. Yang ⁸², W. J. Yao ⁶, Z. P. Yao ⁵⁷, M. Ye ^1,67, M. H. Ye ^9,a, Z. J. Ye ^64,k, K. Yi ⁴⁷, Junhao Yin ⁴⁹, Qiqin Yin ⁴⁸, Z. Y. You ⁶⁸, B. X. Yu ^1,67,73, C. X. Yu ⁴⁹, G. Yu ¹⁴, J. S. Yu ^28,j, L. W. Yu ^13,h, T. Yu ⁸², X. D. Yu ^52,i, Y. C. Yu ⁹¹, Yongchao Yu ⁴³, C. Z. Yuan ^1,73, H. Yuan ^1,73, J. Yuan ³⁹, Jie Yuan ⁵¹, L. Yuan ², M. K. Yuan ^13,h, S. H. Yuan ⁸², Y. Yuan ^1,73, Z. Y. Yuan ⁷³, C. X. Yue ⁴⁴, Ying Yue ²¹, A. A. Zafar ⁸³, F. R. Zeng ⁵⁷, S. H. Zeng ⁷², X. Zeng ^13,h, Y. J. Zeng ^1,73, Yujie Zeng ⁶⁸, Y. C. Zhai ⁵⁷, Y. H. Zhan ⁶⁸, B. L. Zhang ^1,73, B. R. Zhang ²¹, B. X. Zhang ^1,a, D. H. Zhang ⁴⁹, G. Y. Zhang ²¹, Gengyuan Zhang ^1,73, H. Zhang ^80,67, H. C. Zhang ^1,67,73, H. H. Zhang ⁶⁸, H. L. Zhang ⁴⁹, H. Q. Zhang ^1,67,73, H. R. Zhang ^80,67, H. Y. Zhang ^1,67, Han Zhang ⁹¹, J. Zhang ⁶⁸, J. J. Zhang ⁶⁰, J. L. Zhang ²², J. Q. Zhang ⁴⁷, J. S. Zhang ^13,h, J. W. Zhang ^1,67,73, J. X. Zhang ^43,l,m, J. Y. Zhang ¹, J. Z. Zhang ^1,73, Jianyu Zhang ⁵⁰, Jin Zhang ⁵⁴, Jiyuan Zhang ^13,h, L. M. Zhang ⁷⁰, Lei Zhang ⁴⁸, N. Zhang ³⁹, P. Zhang ^1,9, Q. Y. Zhang ³⁹, Q. Z. Zhang ⁷³, R. Y. Zhang ^43,l,m, S. H. Zhang ^1,73, S. N. Zhang ⁷⁸, Shulei Zhang ^28,j, X. M. Zhang ¹, X. Y. Zhang ⁵⁷, Y. T. Zhang ⁹¹, Y. H. Zhang ^1,67, Y. P. Zhang ^80,67, Yao Zhang ¹, Yu Zhang ⁸², Yu Zhang ⁶⁸, Z. Zhang ³⁵, Z. D. Zhang ¹, Z. H. Zhang ¹, Z. L. Zhang ³⁹, Z. R. Zhang ¹, Z. X. Zhang ²¹, Z. Y. Zhang ⁸⁶, Zh. Zh. Zhang ²¹, Zhaoke Zhang ^1,73, Zhilong Zhang ⁶³, Ziyang Zhang ⁵¹, Ziyu Zhang ⁴⁹, G. Zhao ¹, J.-P. Zhao ⁷³, J. Y. Zhao ^1,73, J. Z. Zhao ^1,67, L. Zhao ¹, Lei Zhao ^80,67, M. G. Zhao ⁴⁹, R. P. Zhao ⁷³, Y. B. Zhao ^1,67, Y. L. Zhao ⁶³, Y. P. Zhao ⁵¹, Y. X. Zhao ^35,73, Z. G. Zhao ^80,67, A. Zhemchugov ^41,b, B. Zheng ⁸², B. M. Zheng ³⁹, J. P. Zheng ^1,67, W. J. Zheng ^1,73, W. Q. Zheng ¹⁰, X. R. Zheng ²¹, Y. H. Zheng ^73,p, B. Zhong ⁴⁷, C. Zhong ²¹, X. Zhong ⁴⁶, H. Zhou ^40,57,o, J. Q. Zhou ³⁹, S. Zhou ⁶, X. Zhou ⁸⁶, X. K. Zhou ⁶, X. R. Zhou ^80,67, X. Y. Zhou ⁴⁴, Y. X. Zhou ⁸⁸, Y. Z. Zhou ²¹, A. N. Zhu ⁷³, J. Zhu ⁴⁹, K. Zhu ¹, K. J. Zhu ^1,67,73, K. S. Zhu ^13,h, L. X. Zhu ⁷³, Lin Zhu ²¹, S. H. Zhu ⁷⁹, T. J. Zhu ^13,h, W. D. Zhu ^13,h, W. J. Zhu ¹, W. Z. Zhu ²¹, Y. C. Zhu ^80,67, Z. A. Zhu ^1,73, X. Y. Zhuang ⁴⁹, M. Zhuge ⁵⁷, J. H. Zou ¹, and J. Zu ³⁵ (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
¹²College of William and Mary, Williamsburg, Virginia 23185, USA
¹³Fudan University, Shanghai 200433, People’s Republic of China
¹⁴GSI Helmholtzcentre for Heavy Ion Research GmbH, D-64291 Darmstadt, Germany
¹⁵Guangxi Normal University, Guilin 541004, People’s Republic of China
¹⁶Guangxi University, Nanning 530004, People’s Republic of China
¹⁷Guangxi University of Science and Technology, Liuzhou 545006, People’s Republic of China
¹⁸Hangzhou Normal University, Hangzhou 310036, People’s Republic of China
¹⁹Hebei University, Baoding 071002, People’s Republic of China
²⁰Helmholtz Institute Mainz, Staudinger Weg 18, D-55099 Mainz, Germany
²¹Henan Normal University, Xinxiang 453007, People’s Republic of China
²²Henan University, Kaifeng 475004, People’s Republic of China
²³Henan University of Science and Technology, Luoyang 471003, People’s Republic of China
²⁴Henan University of Technology, Zhengzhou 450001, People’s Republic of China
²⁵Hengyang Normal University, Hengyang 421002, People’s Republic of China
²⁶Huangshan College, Huangshan 245000, People’s Republic of China
²⁷Hunan Normal University, Changsha 410081, People’s Republic of China
²⁸Hunan University, Changsha 410082, People’s Republic of China
²⁹Indian Institute of Technology Madras, Chennai 600036, India
³⁰Indiana University, Bloomington, Indiana 47405, USA
^31aINFN Laboratori Nazionali di Frascati, I-00044, Frascati, Italy
^31bINFN Sezione di Perugia, I-06100, Perugia, Italy
^31cUniversity of Perugia, I-06100, Perugia, Italy
^32aINFN Sezione di Ferrara, I-44122, Ferrara, Italy
^32bUniversity of Ferrara, I-44122, Ferrara, Italy
³³Inner Mongolia University, Hohhot 010021, People’s Republic of China
³⁴Institute of Business Administration, University Road, Karachi, 75270 Pakistan
³⁵Institute of Modern Physics, Lanzhou 730000, People’s Republic of China
³⁶Institute of Physics and Technology, Mongolian Academy of Sciences, Peace Avenue 54B, Ulaanbaatar 13330, Mongolia
³⁷Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica 1000000, Chile
³⁸Jiangsu Ocean University, Lianyungang 222005, People’s Republic of China
³⁹Jilin University, Changchun 130012, People’s Republic of China
⁴⁰Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany
⁴¹Joint Institute for Nuclear Research, 141980 Dubna, Moscow region, Russia
⁴²Justus-Liebig-Universitaet Giessen, II. Physikalisches Institut, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
⁴³Lanzhou University, Lanzhou 730000, People’s Republic of China
⁴⁴Liaoning Normal University, Dalian 116029, People’s Republic of China
⁴⁵Liaoning University, Shenyang 110036, People’s Republic of China
⁴⁶Longyan University, Longyan 364000, People’s Republic of China
⁴⁷Nanjing Normal University, Nanjing 210023, People’s Republic of China
⁴⁸Nanjing University, Nanjing 210093, People’s Republic of China
⁴⁹Nankai University, Tianjin 300071, People’s Republic of China
⁵⁰National Centre for Nuclear Research, Warsaw 02-093, Poland
⁵¹North China Electric Power University, Beijing 102206, People’s Republic of China
⁵²Peking University, Beijing 100871, People’s Republic of China
⁵³Qufu Normal University, Qufu 273165, People’s Republic of China
⁵⁴Renmin University of China, Beijing 100872, People’s Republic of China
⁵⁵Shandong Management University, No. 3500, Dingxiang Road, Changqing District, Jinan City, Shandong Province
⁵⁶Shandong Normal University, Jinan 250014, People’s Republic of China
⁵⁷Shandong University, Jinan 250100, People’s Republic of China
⁵⁸Shandong University of Technology, Zibo 255000, People’s Republic of China
⁵⁹Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China
⁶⁰Shanxi Normal University, Linfen 041004, People’s Republic of China
⁶¹Shanxi University, Taiyuan 030006, People’s Republic of China
⁶²Sichuan University, Chengdu 610064, People’s Republic of China
⁶³Soochow University, Suzhou 215006, People’s Republic of China
⁶⁴South China Normal University, Guangzhou 510006, People’s Republic of China
⁶⁵Southeast University, Nanjing 211100, People’s Republic of China
⁶⁶Southwest University of Science and Technology, Mianyang 621010, People’s Republic of China
⁶⁷State Key Laboratory of Particle Detection and Electronics, Beijing 100049, Hefei 230026, People’s Republic of China
⁶⁸Sun Yat-Sen University, Guangzhou 510275, People’s Republic of China
⁶⁹Suranaree University of Technology, University Avenue 111, Nakhon Ratchasima 30000, Thailand
⁷⁰Tsinghua University, Beijing 100084, People’s Republic of China
^71aTurkish Accelerator Center Particle Factory Group, Istinye University, 34010, Istanbul, Turkey
^71bNear East University, Nicosia, North Cyprus, 99138, Mersin 10, Turkey
⁷²University of Bristol, H H Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL, United Kingdom
⁷³University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
⁷⁴University of Hawaii, Honolulu, Hawaii 96822, USA
⁷⁵University of Jinan, Jinan 250022, People’s Republic of China
⁷⁶University of La Serena, Av. Raúl Bitrán 1305, La Serena, Chile
⁷⁷University of Muenster, Wilhelm-Klemm-Strasse 9, 48149 Muenster, Germany
⁷⁸University of Oxford, Keble Road, Oxford OX13RH, United Kingdom
⁷⁹University of Science and Technology Liaoning, Anshan 114051, People’s Republic of China
⁸⁰University of Science and Technology of China, Hefei 230026, People’s Republic of China
⁸¹University of Silesia in Katowice, Institute of Physics, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland
⁸²University of South China, Hengyang 421001, People’s Republic of China
⁸³University of the Punjab, Lahore-54590, Pakistan
^84aUniversity of Turin, I-10125, Turin, Italy
^84bUniversity of Eastern Piedmont, I-15121, Alessandria, Italy
^84cINFN, I-10125, Turin, Italy
⁸⁵Uppsala University, Box 516, SE-75120 Uppsala, Sweden
⁸⁶Wuhan University, Wuhan 430072, People’s Republic of China
⁸⁷Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an, Shaanxi 710049, People’s Republic of China
⁸⁸Yantai University, Yantai 264005, People’s Republic of China
⁸⁹Yunnan University, Kunming 650500, People’s Republic of China
⁹⁰Zhejiang University, Hangzhou 310027, People’s Republic of China
⁹¹Zhengzhou University, Zhengzhou 450001, People’s Republic of China

^*Full author list given at the end of the article.
^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.

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Phys. Rev. D 114, 092001 – Published 3 November, 2026

DOI: https://doi.org/10.1103/ml3k-2pss

Abstract

Based on an integrated luminosity of $20.3 {fb}^{- 1}$ of $e^{+} e^{-}$ annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector operating at the BEPCII collider, an improved search for the radiative transitions $ψ (3770) \to γ η_{c} (1 S, 2 S)$ is performed using the hadronic decays $η_{c} (1 S, 2 S) \to K_{S}^{0} K^{\pm} π^{\mp}$ . No significant signal is observed. The corresponding 90% confidence level upper limits on the product branching fractions are set to be $5.0 \times 10^{- 6}$ for the $η_{c} (1 S)$ transition and $3.7 \times 10^{- 6}$ for the $η_{c} (2 S)$ transition. The 90% confidence level upper limits on the partial decay widths are also reported to be $Γ (ψ (3770) \to γ η_{c} (1 S)) < 5.5 keV$ and $Γ (ψ (3770) \to γ η_{c} (2 S)) < 29.4 keV$ . With about seven times larger integrated luminosity than used previously, these results lower the upper limits by approximately a factor of three and two for the $η_{c} (1 S)$ and $η_{c} (2 S)$ transitions, respectively.

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Phys. Rev. D 114, 092001– Published 3 November, 2026

Vol. 114, Iss. 9 — 1 November 2026

Received 29 September 2026
Accepted 9 October 2026

DOI: https://doi.org/10.1103/ml3k-2pss

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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Improved search for $ψ (3770) \to γ η_{c} (1 S, 2 S)$ radiative transitions

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Improved search for ψ(3770)→γηc(1S,2S) radiative transitions

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Improved search for $ψ (3770) \to γ η_{c} (1 S, 2 S)$ radiative transitions