Speaker
Description
An exotic state with $J^{PC}=1^{-+}$, denoted by $\eta_1(1855)$, was observed by BESIII collaboration recently in $J/\psi \to \gamma \eta\eta^\prime$. The fact that its mass is just below the threshold of $K\bar{K}_1(1400)$ stimulates us to investigate whether this exotic state can be interpreted as a $K\bar{K}_1(1400)+ c.c.$ {molecule or not}. Using the one boson exchange model, we show that it is possible for $K\bar{K}_1(1400)$ with $J^{PC}=1^{-+}$ to bind together by taking the momentum cutoff $\Lambda\sim 2~\rm GeV$ and yield the same binding energy as the experimental value when $\Lambda\approx 2.5~\rm GeV$. In this molecular picture, the predicted branch ratio $\mathrm{Br}(\eta_1(1855)\to\eta\eta^\prime) \approx 15\%$ is consistent with the experimental results, which again supports the molecular explanation of $\eta_1(1855)$. Relevant systems, namely $K\bar{K}_1(1400)$ with $J^{PC}=1^{--}$ and $K\bar{K}_1(1270)$ with $J^{PC}=1^{-\pm}$, are also investigated, some of which can be searched for in the future experiments.
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