QCD sum rule studies of ss(s)over-bar(s)over-bar tetraquark states with JPC=1+-

We apply the method of QCD sum rules to study the structure X newly observed by the BESIII Collaboration in the f. mass spectrum in 2.0-2.1 GeV region in the J/.. f.. decay. We construct all the ss s s tetraquark currents with J PC = 1 +-, and use them to perform QCD sum rule analyses. One current leads to reliable QCD sum rule results and the mass is extracted to be 2.00 + 0.10 -0.09 GeV, suggesting that the structure X can be interpreted as an ss s s tetraquark state with J PC = 1 +-. The Y (2175) can be interpreted as its ss s s partner having J PC = 1 --, and we propose to search for the other two partners, the ss s s tetraquark states with J PC = 1 ++ and 1 -+, in the. f0(980),. K K, and. K K * mass spectra.