Observation and spin-parity determination of the X (1835) in J/ψ →γKS0KS0η

Abstract

We report an observation of the process J/ψ→γX(1835)→γKS0KS0η at low KS0KS0 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 KS0KS0 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)-25+16(syst) MeV/c2 and 192-17+20(stat)-43+62(syst) MeV, respectively, which are consistent with the results obtained by BESIII in the channel J/ψ→γπ+π-η′.