Open Access

Medina Ablikim, Mikhail N. Achasov, Samer Ahmed, Malte Albrecht, Antonio Amoroso, Fenfen An, Qi An, Y. Bai, Olga Bakina, Rinaldo Baldini Ferroli, Yong Ban, D.W. Bennett, Jake V. Bennett, Niklaus Berger, Monica Bertani, Diego Bettoni, J.M. Bian, Fabrizio Bianchi, E. Boger, Igor R. Boyko, Roy A. Briere, H. Cai, Xiao Cai, O. Cakir, Alessandro Calcaterra, G.F. Cao, Serkant Ali Çetin, J. Chai, Jinfan Chang, Gueorgui A. Chelkov, G. Chen, Hesheng Chen, J.C. Chen, M.L. Chen, P.L. Chen, S.J. Chen, X.R. Chen, Yuanbo Chen, X.K. Chu, Gianluigi Cibinetto, Hongliang Dai, J.P. Dai, Alaa Dbeyssi, Dmitri V. Dedovich, Ziyan Deng, Achim Denig, Igor Denysenko, Marco Giovanni Maria Destefanis, Francesca De Mori, Y. Ding, C. Dong, J. Dong, Liaoyuan Dong, Mingyi Dong, Z.L. Dou, Shuxian Du, P.F. Duan, J. Fang, Shuangshi Fang, X. Fang, Y. Fang, Riccardo Farinelli, Luciano Fava, S. Fegan, Florian Feldbauer, Giulietto Felici, C.Q. Feng, Elisa Fioravanti, Miriam Fritsch, Chengdong Fu, Q. Gao, X.L. Gao, Y. Gao, Y.G. Gao, Z. Gao, I. Garzia, Klaus Goetzen, L. Gong, Wenxuan Gong, Wolfgang Gradl, M. Greco, Minhao Gu, S. Gu, Y.T. Gu, Aiqiang Guo, L.B. Guo, R.P. Guo, Yuping Guo, Z. Haddadi, S. Han, Xiqing Hao, F.A. Harris, K.L. He, Fritz-Herbert Heinsius, T. Held, Yuekun Heng, Tobias Holtmann, Zhilong Hou, C. Hu, Haiming Hu, T. Hu, Y. Hu, G.S. Huang, J.S. Huang, X.T. Huang, X.Z. Huang, Z.L. Huang, Tahir Hussain, Walter Ikegami Andersson, Quan Ji, Qingping Ji, X.B. Ji, X.L. Ji, Xiaoshan Jiang, X.Y. Jiang, J.B. Jiao, Z. Jiao, D.P. Jin, Shan Jin, Y. Jin, Tord Johansson, A. Julin, Nasser Kalantar-Nayestanaki, Xiaolin Kang, X.S. Kang, Myroslav O. Kavatsyuk, Bai-Cian Ke, T. Khan, Alfons Khoukaz, P. Kiese, Ralf Kliemt, Leonard Koch, Onur Bugra Kolcu, Bertram Kopf, M. Kornicer, M. Kuemmel, Meike Küßner, M. Kuhlmann, Andrzej Kupsc, Wolfgang Kühn, Jens Sören Lange, M. Lara, Paul Larin, Lia Lavezzi, S. Leiber, H. Leithoff, C. Leng, C. Li, Cheng Li, D.M. Li, F. Li, F.Y. Li, G. Li, Haibo Li, H.J. Li, J.C. Li, K.J. Li, Kang Li, Ke Li, Lei Li, P.L. Li, P.R. Li, Q.Y. Li, T. Li, Weidong Li, Weiguo Li, X.L. Li, X.N. Li, X.Q. Li, Z.B. Li, H. Liang, Y.F. Liang, Y.T. Liang, G.R. Liao, D.X. Lin, B. Liu, B.J. Liu, C.X. Liu, D. Liu, Fu-Hu Liu, Fang Liu, Feng Liu, H.B. Liu, H.M. Liu, Huanhuan Liu, Huihui Liu, J.B. Liu, J.P. Liu, J.Y. Liu, K. Liu, K.Y. Liu, Ke Liu, L.D. Liu, P.L. Liu, Q. Liu, S.B. Liu, X. Liu, Y.B. Liu, Zhen-An Liu, Zhiqing Liu, Y.F. Long, Xinchou Lou, H.J. Lu, Junguang Lu, Y. Lu, Yunpeng Lu, Chenglin Luo, M.X. Luo, X.L. Luo, Xiao-Rui Lyu, Fengcai Ma, H.L. Ma, Lianliang Ma, M.M. Ma, Qiumei Ma, T. Ma, X.N. Ma, Xiaoyan Ma, Y.M. Ma, Frank E. Maas, Marco Maggiora, Q.A. Malik, Yajun Mao, Zepu Mao, Simonetta Marcello, Z.X. Meng, Johannes Gerhardus Messchendorp, Giulio Mezzadri, J. Min, T.J. Min, Ryan Edward Mitchell, Xiaohu Mo, Y.J. Mo, C. Morales Morales, G. Morello, Nikolai Yu. Muchnoi, H. Muramatsu, A. Mustafa, Yury Nefedov, Frank Nerling, Ivan Borisovich Nikolaev, Z. Ning, Shabana Nisar, S.L. Niu, X.Y. Niu, Stephen L. Olsen, Qun Ouyang, Simone Pacetti, Y. Pan, M. Papenbrock, P. Patteri, Marc Pelizäus, J. Pellegrino, H.P. Peng, Klaus Peters, J. Pettersson, J.L. Ping, R.G. Ping, A. Pitka, Ronald Poling, Vindhyawasini Prasad, H.R. Qi, Ming Qi, S. Qian, Congfeng Qiao, N. Qin, X.S. Qin, Zhonghua Qin, Jinfa Qiu, K.H. Rashid, Christoph Florian Redmer, M. Richter, M. Ripka, Manuel Dionisio Da Rocha Rolo, Gang Rong, Christoph Rosner, X.D. Ruan, Andrei V. Sarantsev, M. Savrié, Claudius Schnier, Karin Schönning, Wei Shan, M. Shao, C.P. Shen, P.X. Shen, X.Y. Shen, H.Y. Sheng, J.J. Song, W.M. Song, X.Y. Song, Stefano Sosio, C. Sowa, Stefano Spataro, Gongxing Sun, J.F. Sun, L. Sun, S.S. Sun, X.H. Sun, Y.J. Sun, Y.K. Sun, Y.Z. Sun, Z.J. Sun, Z.T. Sun, C.J. Tang, G.Y. Tang, X. Tang, I. Tapan, M. Tiemens, B. Tsednee, Ismail Uman, G.S. Varner, B. Wang, B.L. Wang, D. Wang, D.Y. Wang, Dan Wang, K. Wang, L.L. Wang, L.S. Wang, M. Wang, Meng Wang, P. Wang, P.L. Wang, W.P. Wang, X.F. Wang, Y. Wang, Y.D. Wang, Y.F. Wang, Y.Q. Wang, Z. Wang, Z.G. Wang, Z.H. Wang, Z.Y. Wang, Zongyuan Wang, T. Weber, D.H. Wei, P. Weidenkaff, Shuopin Wen, Ulrich Wiedner, Magnus Wolke, Linghui Wu, L.J. Wu, Z. Wu, L. Xia, X. Xia, Y. Xia, D. Xiao, H. Xiao, Y.J. Xiao, Zhenjun Xiao, Y.G. Xie, Y.H. Xie, X.A. Xiong, Q.L. Xiu, Guofa Xu, J.J. Xu, L. Xu, Q.J. Xu, Q.N. Xu, Xinping Xu, L. Yan, W.B. Yan, W.C. Yan, W.C. Yan, Y.H. Yan, H.J. Yang, Hongxun Yang, L. Yang, Y.H. Yang, Yongxu Yang, Yifan Yang, M. Ye, Minghan Ye, J.H. Yin, Z.Y. You, Boxiang Yu, C.X. Yu, J.S. Yu, Chang-Zheng Yuan, Y. Yuan, A. Yuncu, A.A. Zafar, A. Zallo, Y. Zeng, Z. Zeng, B.X. Zhang, B.Y. Zhang, C.C. Zhang, D.H. Zhang, H.H. Zhang, Hongyu Zhang, J. Zhang, J.L. Zhang, J.Q. Zhang, J.W. Zhang, Jianyong Zhang, J.Z. Zhang, K. Zhang, L. Zhang, S.Q. Zhang, X.Y. Zhang, Y.H. Zhang, Y.T. Zhang, Yang Zhang, Yao Zhang, Yu Zhang, Z.H. Zhang, Z.P. Zhang, Z.Y. Zhang, G. Zhao, J.W. Zhao, J.Y. Zhao, J.Z. Zhao, Lei Zhao, Ling Zhao, Ming-Gang Zhao, Q. Zhao, Shujun Zhao, T.C. Zhao, Yubin Zhao, Zhengguo Zhao, Alexey Zhemchugov, B. Zheng, Jianping Zheng, W.J. Zheng, Y.H. Zheng, B. Zhong, L. Zhou, X. Zhou, X.K. Zhou, X.R. Zhou, X.Y. Zhou, Y.X. Zhou, J. Zhu, J. Zhu, K. Zhu, Kejun Zhu, S. Zhu, S.H. Zhu, X.L. Zhu, Y.C. Zhu, Y.S. Zhu, Zian Zhu, J. Zhuang, B.S. Zou, Jiaheng Zou

• Using 16 energy points of e+e− annihilation data collected in the vicinity of the J/ψ resonance with the BESIII detector and with a total integrated luminosity of around 100 pb−1, we study the relative phase between the strong and electromagnetic amplitudes of J/ψ decays. The relative phase between J/ψ electromagnetic decay and the continuum process (e+e− annihilation without the J/ψ resonance) is confirmed to be zero by studying the cross section lineshape of μ+μ− production. The relative phase between J/ψ strong and electromagnetic decays is then measured to be (84.9 ± 3.6)◦ or (−84.7 ± 3.1)◦ for the 2(π+π−)π0 final state by investigating the interference pattern between the J/ψ decay and the continuum process. This is the first measurement of the relative phase between J/ψ strong and electromagnetic decays into a multihadron final state using the lineshape of the production cross section. We also study the production lineshape of the multihadron final state ηπ+π− with η → π+π−π0, which provides additional information about the phase between the J/ψ electromagnetic decay amplitude and the continuum process. Additionally, the branching fraction of J/ψ → 2(π+π−)π0 is measured to be (4.73 ± 0.44)% or (4.85 ± 0.45)%, and the branching fraction of J/ψ → ηπ+π− is measured to be (3.78 ± 0.68) × 10−4. Both of them are consistent with the world average values. The quoted uncertainties include both statistical and systematic uncertainties, which are mainly caused by the low statistics.