QCD sum rule studies of sss¯ s¯ tetraquark states with J PC = 1 + -

Abstract

We apply the method of QCD sum rules to study the structure X newly observed by the BESIII Collaboration in the ϕη ′ mass spectrum in 2.0–2.1 GeV region in the J/ ψ→ ϕηη ′ decay. We construct all the sss¯ 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 2.00-0.09+0.10 GeV, suggesting that the structure X can be interpreted as an sss¯ s¯ tetraquark state with J PC = 1 + - . The Y(2175) can be interpreted as its sss¯ s¯ partner having J PC = 1 - - , and we propose to search for the other two partners, the sss¯ s¯ tetraquark states with J PC = 1 + + and 1 - + , in the η ′ f(980) , η ′ KK¯ , and η ′ KK¯ ∗ mass spectra.