Partial-wave analysis of $J/\psi \to K^{+}{K}^{-}{\pi }^0$

A partial-wave analysis of the decay $J/\psi \to K^{+}{K}^{-}{\pi }^0$ has been made using $(223.7\pm 1.4)\times {10}^{6}J/\psi$ events collected with the BESIII detector in 2009. The analysis, which is performed within the isobar-model approach, reveals contributions from $K_2^{*}(1430{)}^{\pm }$, $K_2^{*}(1980{)}^{\pm }$ and $K_4^{*}(2045{)}^{\pm }$ decaying to $K^{\pm }{\pi }^0$. The two latter states are observed in $J/\psi$ decays for the first time. Two resonance signals decaying to $K^{+}{K}^{-}$ are also observed. These contributions cannot be reliably identified and their possible interpretations are discussed. The measured branching fraction $B(J/\psi \to K^{+}{K}^{-}{\pi }^0)$ of $(2.88\pm 0.01\pm 0.12)\times {10}^{-3}$ is more precise than previous results. Branching fractions for the reported contributions are presented as well. The results of the partial-wave analysis differ significantly from those previously obtained by BESII and BABAR.

Figure 1

Dalitz plots for the selected data (a), the PWA solution I (b) and the PWA solution II (c).

Figure 2

Kinematical distributions for the data (dots), the PWA solution I (shaded histograms) and the PWA solution II (solid line). The notation $K$ without any specified charge indicates the sum of the $K^{+}$ and $K^{-}$ distributions. (a),(b) Invariant mass of the $K^{+}{K}^{-}$ and $K^{\pm }{\pi }^0$ systems. (c),(d) Distributions of the final-state particles’ polar angle (${\theta }_{{\pi }^0}$, ${\theta }_K$) with respect to the beam axis in the $J/\psi$ rest frame. (e),(f) Polar angle distributions (${\theta }_{KK}$, ${\theta }_{\pi K}$) for $K^{+}$ in the $K^{+}{K}^{-}$ helicity frame (e) and for ${\pi }^0$ in the $K{\pi }^0$ helicity frame (f). The uncertainties are statistical and are within the size of the dots.

Figure 3

Kinematical distributions for the data (dots), PWA solution I (shaded histograms) and PWA solution II (solid line) in the inner region of the Dalitz plot [$M(K^{\pm }{\pi }^0)>1.05\mathrm{GeV}/c^2$]. The notation $K$ without any specified charge indicates the sum of the $K^{+}$ and $K^{-}$ distributions. (a),(b) Invariant mass of the $K^{+}{K}^{-}$ and $K^{\pm }{\pi }^0$ systems. (c),(d) Distributions of the final-state particles’ polar angle (${\theta }_{{\pi }^0}$, ${\theta }_K$) with respect to the beam axis in the $J/\psi$ rest frame. (e),(f) Polar angle distributions (${\theta }_{KK}$, ${\theta }_{\pi K}$) for $K^{+}$ in the $K^{+}{K}^{-}$ helicity frame (e) and for the ${\pi }^0$ in the $K{\pi }^0$ helicity frame (f). The error bars represent the statistical uncertainties.

Figure 4

Mass and width scans for the $K_2^{*}(1430)$, $K_2^{*}(1980)$, $K_4^{*}(2045)$ and $1^{--}$ structures at 1650 and $2050\mathrm{MeV}/c^2$ for solution II.