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Triangle mechanism in the decay processJ/ψ→K−K+a1(1260)
Physical Review D  (IF5.296),  Pub Date : 2021-10-19, DOI: 10.1103/physrevd.104.074016
Xuan Luo, Dazhuang He, Yiling Xie, Hao Sun

The role of the triangle mechanism in the decay process $J/\psi \to {K}^{-}{K}^{+}{a}_{1}\left(1260\right)$ is probed. In this mechanism, a close-up resonance with mass 1823 MeV and width 122 MeV decays into ${K}^{*}\varphi ,{K}^{*}\to K\pi$ and then ${K}^{*}\overline{K}$ fuses into the ${a}_{1}\left(1260\right)$ resonance. We find that this mechanism leads to a triangle singularity around ${M}_{\mathrm{inv}}\left({K}^{-}{a}_{1}\left(1260\right)\right)\approx 1920\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{MeV}$, where the axial-vector meson ${a}_{1}\left(1260\right)$ is considered as a dynamically generated resonance. With the help of the triangle mechanism we find sizable branching ratios $\mathrm{Br}\left(J/\psi \to {K}^{-}{K}^{+}{a}_{1}\left(1260\right),{a}_{1}\to \pi \rho \right)=1.210×{10}^{-5}$ and $\mathrm{Br}\left(J/\psi \to {K}^{-}{K}^{+}{a}_{1}\left(1260\right)\right)=3.501×{10}^{-5}$. Such an effect from the triangle mechanism of the decay process could be investigated by such as BESIII, LHCb and Belle-II experiments. This potential investigation can help us obtain the information of the axial-vector meson ${a}_{1}\left(1260\right)$.