Observation and Spin-Parity Determination of the X(1835) in J/ψ → γ$K_S^0K_S^0η$

摘要: We report an observation of the process J/ψ→γX(1835)→γK0SK0Sη at low K0SK0S mass with a statistical significance larger than 12.9σ using a data sample of 1.31×109 J/ψ events collected with the BESIII detector. In this region of phase space the K0SK0S system is dominantly produced through the f0(980). By performing a partial wave analysis, we determine the spin-parity of the X(1835) to be JPC=0−+. The mass and width of the observed X(1835) are 1844±9(stat)+16−25(syst)~\MeV~and 192+20−17(stat)+62−43(syst)~MeV, respectively, which are consistent with the results obtained by BESIII in the channel J/ψ→γπ+π−η′.