Several intermediate states of the reaction channels e+e-→π+π-D0D̄0 and e+e-→π+π-D+D- are studied using the data samples collected with the BESIII detector at center-of-mass energies above 4.08 GeV. For the first time in this final state, a ψ(3770) signal is seen in the DD̄ invariant mass spectrum, with a statistical significance of 5.2σ at s=4.42 GeV. There is also evidence for this resonance at s=4.26 and 4.36 GeV with statistical significance of 3.2σ and 3.3σ, respectively. In addition, the Born cross section of e+e-→π+π-ψ(3770) is measured. The proposed heavy-quark-spin-symmetry partner of the X(3872), the state X2(4013), is also searched for in the DD̄ invariant mass spectra. No obvious signal is found. The upper limit of the Born cross section of the process e+e-→ρ0X2(4013) combined with the branching fraction is measured. Also, the processes e+e-→D1(2420)D̄+c.c. are investigated. The neutral mode with D1(2420)0→D0π+π- is reported with statistical significance of 7.4σ at s=4.42 GeV for the first time, and evidence with statistical significance of 3.2σ and 3.3σ at s=4.36 and 4.60 GeV is seen, respectively. No evident signal for the process e+e-→D1(2420)0D̄0+c.c.,D1(2420)0→D∗+π- is reported. Evidence for e+e-→D1(2420)+D-+c.c.,D1(2420)+→D+π+π- is reported with statistical significance of 3.1σ and 3.0σ at s=4.36 and 4.42 GeV, respectively.
Bibliographical noteFunding Information:
The BESIII collaboration thanks the staff of BEPCII and the IHEP computing center 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. 11625523, No. 11635010, No. 11735014; National Natural Science Foundation of China (NSFC) under Contract No. 11835012; 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. U1532257, No. U1532258, No. U1732263, No. U1832207; CAS Key Research Program of Frontier Sciences under Contracts No. QYZDJ-SSW-SLH003, No. QYZDJ-SSW-SLH040; 100 Talents Program of CAS; The Institute of Nuclear and Particle Physics (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; German Research Foundation DFG under Contract No. Collaborative Research Center CRC 1044; Istituto Nazionale di Fisica Nucleare, Italy; Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) under Contract No. 530-4CDP03; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Science and Technology fund; The Knut and Alice Wallenberg Foundation (Sweden) under Contract No. 2016.0157; 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.
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