Observation of a Resonant Structure in $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0$

A partial-wave analysis is performed for the process $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0$ at the center-of-mass energies ranging from 2.000 to 2.644 GeV. The data samples of $e^{+}{e}^{-}$ collisions, collected by the BESIII detector at the BEPCII collider with a total integrated luminosity of $300{\mathrm{pb}}^{-1}$, are analyzed. The total Born cross sections for the process $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0$, as well as the Born cross sections for the subprocesses $e^{+}{e}^{-}\to \varphi {\pi }^0{\pi }^0$, $K^{+}(1460)K^{-}$, $K_1^{+}(1400)K^{-}$, $K_1^{+}(1270)K^{-}$, and $K^{*+}(892)K^{*-}(892)$, are measured versus the center-of-mass energy. The corresponding results for $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0$ and $\varphi {\pi }^0{\pi }^0$ are consistent with those of BABAR with better precision. By analyzing the cross sections for the four subprocesses, $K^{+}(1460)K^{-}$, $K_1^{+}(1400)K^{-}$, $K_1^{+}(1270)K^{-}$, and $K^{*+}(892)K^{*-}(892)$, a structure with mass $M=(2126.5\pm 16.8\pm 12.4)\mathrm{MeV}/c^2$ and width $\mathrm{\Gamma }=(106.9\pm 32.1\pm 28.1)\mathrm{MeV}$ is observed with an overall statistical significance of $6.3\sigma$, although with very limited significance in the subprocesses $e^{+}{e}^{-}\to K_1^{+}(1270)K^{-}$ and $K^{*+}(892)K^{*-}(892)$. The resonant parameters of the observed structure suggest it can be identified with the $\varphi (2170)$, thus the results provide valuable input to the internal nature of the $\varphi (2170)$.

Figure 1

The Born cross sections for (a) the process $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0$ and (b) the subprocess $e^{+}{e}^{-}\to \varphi {\pi }^0{\pi }^0$. The red squares are from this analysis; the blue dots are from the BABAR experiment [4]. For our data, the errors reflect both statistical and systematical uncertainties.

Figure 2

Fit to the cross sections for $e^{+}{e}^{-}$ to the final states (a) $K^{+}(1460)K^{-}$, (b) $K_1^{+}(1400)K^{-}$, (c) $K_1^{+}(1270)K^{-}$, and (d) $K^{*+}(892)K^{*-}(892)$, where black dots with errors are data, the black solid curves are the overall fit results, the red long-dashed curves are from the intermediate state, the green short-dashed curves are from the nonresonant component, and the blue dash-dotted curves are the interference contribution for solution 1. Here, the errors reflect both statistical and systematic uncertainties.