X(2239) and η(2225) as hidden-strange molecular states from Λ Λ interaction

In this work,we propose the possible assignment of the newly observed X(2239),as well asη(2225),as a molecular state from the interaction of a baryonΛand an antibaryonΛ.With the help of effective Lagrangians,theΛΛinteraction is described within the one-boson-exchange model withη,η′,ω,ϕ,andσexchanges considered.After inserting the potential kernel into the quasipotential Bethe-Salpeter equation,the bound states from theΛΛinteraction can be studied by searching for the pole of the scattering amplitude.Two loosely bound states with spin parities I^(G)(J^(PC))=0^(+)(0^(−+))and 0^(−)(1^(−−))appear near the threshold with almost the same parameter.The 0^(−)(1^(−−))state can be assigned to X(2239)observed at BESⅢ,which is very close to theΛΛthreshold.The scalar mesonη(2225)can be interpreted as a 0^(+)(0^(−+))state from theΛΛinteraction.The annihilation effect is also discussed through a coupled-channel calculation plus a phenomenological optical potential.It provides large widths to two bound states produced from theΛΛinteraction.The mass of the 1^(−)state is slightly larger than the mass of the 0^(−)state after including the annihilation effect,which is consistent with our assignment of these two states as X(2239)andη(2225),respectively.The results suggest that further investigation is required to understand the structures near theΛΛthreshold,such as X(2239),η(2225),and X(2175).