Determination of the Spin and Parity of the Z_c (3900)


The spin and parity of the Z_{c}(3900)^{±} state are determined to be J^{P} =1⁺ with a statistical significance larger than 7σ over other quantum numbers in a partial wave analysis of the process e⁺e⁻ → π⁺π⁻J/ψ. We use a data sample of 1.92 fb⁻¹ accumulated at √s̅=4.23 and 4.26 GeV with the BESIII experiment. When parametrizing the Z_{c}(3900)^{±} with a Flatté-like formula, we determine its pole mass M_{pole} = (3881.2 ± 4.2_{stat} ± 52.7_{syst}) MeV/c² and pole width Γ_{pole} = (51.8 ± 4.6_{stat} ± 36.0_{syst}) MeV. We also measure cross sections for the process e⁺e⁻→ Z_{c}(3900)^{±}π⁻ + c.c.→ J/ψπ⁺π⁻ and determine an upper limit at the 90% confidence level for the process e⁺e⁻→ Z_{c}(4020)^{±}π⁻ + c.c.→J/ψπ⁺π⁻



Observed confidence levels (Statistics), Quantum theory, Electron-positron interactions, Mesons, Nuclear spin, Particles (Nuclear physics)

This work is supported in part by the Ministry of Science and Technology of China under Contract No. 2009CB825200; Joint Funds of the National Natural Science Foundation of China under Contracts Nos. U1332201; National Natural Science Foundation of China (NSFC) under Contracts No. 11175188, No. 11375205, No. 11235011, No. 11375221, No. 11565006, and No. 10825524; German Research Foundation DFG under Collaborative Research Center Contract No. CRC-1044, 627240; Ministry of Development of Turkey under Contract No. DPT2006K-120470; U.S. Department of Energy under Contracts No. DE-SC-0012069, No. DE-SC-0010504, No. DE-SC-0010118, and No. DE-FG02-05ER41374; University of Groningen (RuG) under Contract No. 530-4CDP03, and the Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt; and WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.


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