Interpretation of theη_(1)(1855)as a KK_(1)(1400)+c.c.molecule

An exotic state with J^(PC)=1^(−+),denoted byη1(1855),was observed by BESIII Collaboration recently in J/ψ→γηη′.The fact that its mass is just below the threshold of KK_(1)(1400)stimulates us to investigate whether this exotic state can be interpreted as a KK_(1)(1400)+c.c.molecule or not.Using the one boson exchange model,we show that it is possible for KK_(1)(1400)with J^(PC)=1^(−+)to bind together by taking the momentum cutoffΛ&2 GeV and yield the same binding energy as the experimental value whenΛ≈2.5 GeV.In this molecular picture,the predicted branch ratio Br(η1(1855)→ηη′)≈15%is consistent with the experimental results,which again supports the molecular explanation ofη1(1855).Relevant systems,namely KK_(1)(1400)with JPC=1−−and KK_(1)(1270)with J^(PC)=1^(−±),are also investigated,some of which can be searched for in the future experiments.