Open Access

Medina Ablikim, Mikhail N. Achasov, Patrik Adlarson, Samer Ahmed, Malte Albrecht, Antonio Amoroso, Qi An, Anita, Yu Bai, Olga Bakina, Rinaldo Baldini Ferroli, Ilaria Balossino, Yong Ban, Khurelbaatar Begzsuren, Jake V. Bennett, Niklaus Berger, Monica Bertani, Diego Bettoni, Fabrizio Bianchi, Jacek Biernat, Johannes Bloms, Alberto Bortone, Igor R. Boyko, Roy A. Briere, Hao Cai, Xiao Cai, Alessandro Calcaterra, G. F. Cao, Ning Cao, Serkant Ali Çetin, Jinfan Chang, W. L. Chang, Gueorgui A. Chelkov, D. Y. Chen, G. Chen, Hesheng Chen, M. L. Chen, S. J. Chen, X. R. Chen, Yuanbo Chen, W. Cheng, Gianluigi Cibinetto, Fabio Cossio, X. F. Cui, Hongliang Dai, J. P. Dai, Xinchen Dai, Alaa Dbeyssi, Remco E. de Boer, Dmitri V. Dedovich, Ziyan Deng, Achim Denig, Igor Denysenko, Marco Giovanni Maria Destefanis, Francesca De Mori, Yanchun Ding, C. Dong, J. Dong, Liaoyuan Dong, Mingyi Dong, Shuxian Du, J. Fang, Shuangshi Fang, Y. Fang, Riccardo Farinelli, Luciano Fava, Florian Feldbauer, Giulietto Felici, C. Q. Feng, Miriam Fritsch, Chengdong Fu, Ying Fu, X. L. Gao, Y. Gao, Y. Gao, Y. G. Gao, Isabella Garzia, Evelina Gersabeck, Alexander Gilman, Klaus Götzen, L. Gong, Wenxuan Gong, Wolfgang Gradl, M. Greco, L. M. Gu, Minhao Gu, S. Gu, Y. T. Gu, C. Y. Guan, Aiqiang Guo, L. B. Guo, Rupan Guo, Yuping Guo, Yuping Guo, Alexey Guskov, S. Han, T. T. Han, T. Z. Han, Xiqing Hao, Frederick Allan Harris, K. L. He, Fritz-Herbert Heinsius, T. Held, Yuekun Heng, Mathilde Himmelreich, Tobias Holtmann, Y. R. Hou, Zhilong Hou, Haiming Hu, J. F. Hu, T. Hu, Y. Hu, G. S. Huang, L. Q. Huang, Xingtao Huang, Z. Huang, Nils Huesken, Tahir Hussain, Walter Ikegami Andersson, William Imoehl, Muzaffar Irshad, S. Jaeger, S. Janchiv, Quan Ji, Qingping Ji, X. B. Ji, X. L. Ji, H. B. Jiang, Xiaoshan Jiang, X. Y. Jiang, J. B. Jiao, Zheng Jiao, Shan Jin, Y. Jin, Tord Johansson, Nasser Kalantar-Nayestanaki, Xiaolin Kang, Rosa Kappert, Myroslav O. Kavatsyuk, Bai-Cian Ke, Iman Keshk, Alfons Khoukaz, P. Kiese, Ryuta Kiuchi, Ralf Kliemt, Leonard Koch, Onur Bugra Kolcu, Bertram Kopf, Miriam Kümmel, Meike Küßner, Andrzej Kupsc, M. G. Kurth, Wolfgang Kühn, John Jake Lane, Jens Sören Lange, Paul Larin, Lia Lavezzi, Hans Heinrich Leithoff, Max Lellmann, Thomas Lenz, C. Li, Chunhua Li, Cheng Li, D. M. Li, F. Li, G. Li, Haibo Li, Huijing Li, J. L. Li, J. Q. Li, Ke Li, L. K. Li, Lei Li, P. L. Li, Peirong Li, Shuaiying Li, Weidong Li, Weiguo Li, X. H. Li, Xing Long Li, Z. B. Li, Z. Y. Li, H. Liang, H. Liang, Y. F. Liang, Y. T. Liang, L. Z. Liao, James Libby, C. X. Lin, B. Liu, B. J. Liu, C. X. Liu, D. Liu, D. Y. Liu, Fu-Hu Liu, Fang Liu, Feng Liu, H. B. Liu, H. M. Liu, Huanhuan Liu, Huihui Liu, J. B. Liu, J. Y. Liu, K. Liu, K. Y. Liu, Ke Liu, L. Liu, L. Y. Liu, Q. Liu, S. B. Liu, Tong Liu, X. Liu, Y. B. Liu, Zhen-An Liu, Zhiqing Liu, Y. F. Long, Xinchou Lou, H. J. Lu, J. D. Lu, Junguang Lu, X. L. Lu, Y. Lu, Yunpeng Lu, Chenglin Luo, M. X. Luo, P. W. Luo, Tao Luo, X. L. Luo, Stefano Lusso, Xiao-Rui Lyu, Fengcai Ma, Hailong Ma, Lianliang Ma, M. M. Ma, Qiumei Ma, Runqiu Ma, R. T. Ma, X. N. Ma, X. X. Ma, Xiaoyan Ma, Y. M. Ma, Frank E. Maas, Marco Maggiora, Stephan Maldaner, Sneha Malde, Qadeer Afzal Malik, Alessio Mangoni, Yajun Mao, Zepu Mao, Simonetta Marcello, Z. X. Meng, Johannes Gerhardus Messchendorp, Giulio Mezzadri, T. J. Min, Ryan Edward Mitchell, Xiaohu Mo, Y. J. Mo, Nikolai Yu. Muchnoi, Hajime Muramatsu, Simon Nakhoul, Yury Nefedov, Frank Nerling, Ivan Borisovich Nikolaev, Z. Ning, Shabana Nisar, Stephen L. Olsen, Qun Ouyang, Simone Pacetti, Y. Pan, Michael Papenbrock, A. Pathak, Piero Patteri, Marc Pelizäus, H. P. Peng, Klaus Peters, J. Pettersson, J. L. Ping, R. G. Ping, A. Pitka, Ronald Poling, Vindhyawasini Prasad, H. Qi, Hongrong Qi, Ming Qi, Tianyu Qi, S. Qian, W.-B. Qian, Congfeng Qiao, L. Q. Qin, Xiaoping Qin, X. S. Qin, Zhonghua Qin, Jinfa Qiu, S. Q. Qu, K. H. Rashid, Krishnakumar Ravindran, Christoph Florian Redmer, Angelo Rivetti, Viktor Rodin, Manuel Dionisio Da Rocha Rolo, Gang Rong, Christoph Rosner, Marcel Andre Rump, Andrei V. Sarantsev, Mauro Savrié, Yasemin Schelhaas, Claudius Schnier, Karin Schönning, Wei Shan, Xinyu Shan, M. Shao, Chengping Shen, P. X. Shen, X. Y. Shen, Huangchao Shi, Rongsheng Shi, X. Shi, Xiaodong Shi, J. J. Song, Q. Q. Song, Yunxuan Song, Stefano Sosio, Stefano Spataro, F. F. Sui, Gongxing Sun, J. F. Sun, Liang Sun, S. S. Sun, T. Sun, Wenyu Sun, Y. J. Sun, Y. K. Sun, Y. Z. Sun, Z. T. Sun, Yaxing Tan, C. J. Tang, G. Y. Tang, J. Tang, Viktor Thoren, B. Tsednee, Ismail Uman, B. Wang, B. L. Wang, Chengwei Wang, D. Y. Wang, H. P. Wang, K. Wang, Liangliang Wang, M. Wang, M. Z. Wang, Meng Wang, Weiping Wang, X. Wang, Xiongfei Wang, X. L. Wang, Y. Wang, Y. Wang, Y. D. Wang, Y. F. Wang, Y. Q. Wang, Z. Wang, Zongyuan Wang, Ziyi Wang, Zongyuan Wang, T. Weber, D. H. Wei, Peter Weidenkaff, Frederik Weidner, H. W. Wen, Shuopin Wen, D. J. White, Ulrich Wiedner, Guy Wilkinson, Magnus Wolke, Leonard Wollenberg, Jinfei Wu, Linghui Wu, Lianjin Wu, Xiao Wu, Z. Wu, Lei Xia, Hao Xiao, S. Y. Xiao, Y. J. Xiao, Zhenjun Xiao, X. H. Xie, Y. G. Xie, Y. H. Xie, T. Y. Xing, X. A. Xiong, Guofa Xu, J. J. Xu, Q. J. Xu, Wei Xu, Xinping Xu, Liang Yan, Liang Yan, W. B. Yan, Wencheng Yan, H. J. Yang, Hongxun Yang, L. Yang, R. X. Yang, S. L. Yang, Y. H. Yang, Yongxu Yang, Yifan Yang, Zhi Yang, M. Ye, Minghan Ye, J. H. Yin, Z. Y. You, Boxiang Yu, Chunxu Yu, G. Yu, J. S. Yu, T. Yu, Chang-Zheng Yuan, W. Yuan, X. Q. Yuan, Ye Yuan, C. X. Yue, Alperen Yüncü, A. A. Zafar, Y. Zeng, B. X. Zhang, Guangyi Zhang, H. H. Zhang, Hongyu Zhang, Jielei Zhang, Jingqing Zhang, Jiawei Zhang, Jianyong Zhang, J. Z. Zhang, Jianyu Zhang, Jiawei Zhang, L. Zhang, Lei Zhang, S. Zhang, Sifan Zhang, T. J. Zhang, X. Y. Zhang, Y. Zhang, Y. H. Zhang, Yateng Zhang, Yan Zhang, Yao Zhang, Yi Zhang, Z. H. Zhang, Z. Y. Zhang, G. Zhao, J. Zhao, Jingyi Zhao, J. Z. Zhao, Lei Zhao, Ling Zhao, Ming-Gang Zhao, Q. Zhao, Shujun Zhao, Yubin Zhao, Y. X. Zhao Zhao, Zhengguo Zhao, Alexey Zhemchugov, Bo Zheng, Jianping Zheng, Y. Zheng, Y. H. Zheng, B. Zhong, C. Zhong, L. P. Zhou, Q. Zhou, X. Zhou, X. K. Zhou, X. R. Zhou, A. N. Zhu, Jianhui Zhu, K. Zhu, Kejun Zhu, S. H. Zhu, W. J. Zhu, X. L. Zhu, Y. C. Zhu, Zian Zhu, B. S. Zou, Jiaheng Zou

• We report a measurement of the observed cross sections of e+ e− → J/ψX based on 3.21 fb − 1 of data accumulated at energies from 3.645 to 3.891 GeV with the BESIII detector operated at the BEPCII collider. In analysis of the cross sections, we measured the decay branching fractions of B(ψ(3686) → J/ψX) = (64.4 ± 0.6 ± 1.6)% and B(ψ(3770) → J/ψX) = (0.5 ± 0.2 ± 0.1)% for the first time. The energy-dependent line shape of these cross sections cannot be well described by two Breit-Wigner (BW) amplitudes of the expected decays ψ (3686) → J/ψX and ψ(3770) → J/ψX. Instead, it can be better described with one more BW amplitude of the decay R(3760)→ J/ψX. Under this assumption, we extracted the R (3760) mass M R (3760 ) = 3766.2 ± 3.8 ± 0.4 MeV/c2, total width Γ tot R ( 3760 ) = 22.2 ± 5.9 ± 1.4 MeV, and product of leptonic width and decay branching fraction ΓeeR(3760) B[R(3760) → J/ψX] = (79.4 ± 85.5 ± 11.7) eV. The significance of the R(3760) is 5.3σ. The first uncertainties of these measured quantities are from fits to the cross sections and second systematic.