Analysis of the $η_1(1855)$ as a $K\bar{K}_1(1400)$ molecular state

Abstract

In this work, we study the radiative and strong decay of S -wave K K1 (1400) molecular state within the effective Lagrangians approach and find the relation between the K K1 (1400) molecular state and the newly observed η 1 (1855) state by comparing with the BESIII observation. The prediction indicates that the decay width depends on the model parameter can reach up to 197.27 +1.64 −1.22 MeV, which can be confronted with the experimental data. If the η 1 (1855) could be S -wave K K1 (1400) molecular state, the K K * π three-body decay provides the dominant contribution, not the ηη ′ channel found in the experiment. In addition, the partial width for η 1 (1855) → γφ can reach up to 10.16 +0.19 −0.35 KeV. Those results can be measured in future experiments and can be used to test the nature of the η 1 (1855).

An updated review of the new hadron states

“…This assignment was supported by Ref. [1061], where the authors studied the radiative and strong decays of the S-wave K K1 (1400) molecular state within the effective Lagrangians approach. See also Ref.…”

Production of the $η_{1}(1855)$ through kaon induced reactions under the assumptions that it is a molecular or a hybrid state

“…Recently, the BESIII Collaboration observed η 1 (1855) in the J/ψ → γηη ′ decay [2]. Since the η 1 (1855) is an isoscalar resonance with exotic J PC = 1 −+ quantum numbers, different explanations of exotic states like hybrid [4][5][6], the K K1 (1400) molecular state [7,8], and tetraquark state [9] were proposed, which shows that this observation attracted theorist's attention in the past months. Besides decoding the nature of the observed η 1 (1855), establishing the η 1 (1855) in experiment is also crucial.…”

“…respectively. Obviously, the observed η 1 (1855) cannot be grouped into the conventional hadron, which is a good candidate of exotic states as indicated by some theoretical groups, where the η 1 (1855) was interpreted as a hybrid state [4][5][6], a molecular state [7,8], and a tetraquark state [9]. At present, the η 1 (1855) was only observed in the radiative decay J/ψ → γηη ′ , confirming this observation by others processes is an interesting experimental topic, which will be helpful to establish this exotic state in experiment and may provide some valuable information to reflect its inner structure.…”

A possible structure of newly found exotic state $η_1(1855)$

“…In fact, the dynamical gluon of the hybrid can easily split into a quark pair, and to discriminate the hybrid from tetraquark one needs to know more fine structures of the observed state. About 1 −+ tetraquark there have been some investigations in the literature [19][20][21][22]. In Ref.…”

“…Narison investigated the 1 −+ tetraquarks in diquark-antidiquark and molecule configurations but with no strange quark component [20]. In Ref [21,22], η 1 (1855) was interpreted as a K K1 (1400) molecular state.…”