Cross sections of the process e+e-→π0π0J/ψ at center-of-mass energies between 3.808 and 4.600 GeV are measured with high precision by using 12.4 fb-1 of data samples collected with the BESIII detector operating at the BEPCII collider facility. A fit to the measured energy-dependent cross sections confirms the existence of the charmoniumlike state Y(4220). The mass and width of the Y(4220) are determined to be (4220.4±2.4±2.3) MeV/c2 and (46.2±4.7±2.1) MeV, respectively, where the first uncertainties are statistical and the second systematic. The mass and width are consistent with those measured in the process e+e-→π+π-J/ψ. The neutral charmonium-like state Zc(3900)0 is observed prominently in the π0J/ψ invariant-mass spectrum, and, for the first time, an amplitude analysis is performed to study its properties. The spin-parity of Zc(3900)0 is determined to be JP=1+, and the pole position is (3893.1±2.2±3.0)-i(22.2±2.6±7.0) MeV/c2, which is consistent with previous studies of electrically charged Zc(3900)±. In addition, cross sections of e+e-→π0Zc(3900)0→π0π0J/ψ are extracted, and the corresponding line shape is found to agree with that of the Y(4220).
Bibliographical noteFunding Information:
The BESIII collaboration thanks the staff of BEPCII and the IHEP computing center and the supercomputing center of USTC for their strong support. This work is supported in part by National Key Basic Research Program of China under Contract No. 2015CB856700; National Natural Science Foundation of China (NSFC) under Contracts No. 11335008, No. 11375170, No. 11475164, No. 11475169, No. 11625523, No. 11605196, No. 11605198, No. 11705192; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. U1532102, No. U1732263, No. U1832103; CAS under Contracts No. QYZDJSSW-SLH003, No. QYZDJ-SSW-SLH040; 100 Talents Program of CAS; INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology; ERC under Contract No. 758462; German Research Foundation DFG under Contract Nos. Collaborative Research Center CRC-1044, ROF 2359; Istituto Nazionale di Fisica Nucleare, Italy; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Science and Technology fund; STFC (United Kingdom); The Knut and Alice Wallenberg Foundation (Sweden) under Contracts No. DH140054, No. DH1600214; The Swedish Research Council; U.S. Department of Energy under Contracts No. DE-FG02-05ER41374, No. DE-SC-0010118, No. DE-SC-0012069; University of Groningen (RuG) and the Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt.
© 2020 authors. Published by the American Physical Society.