Observation of a structure in $e^{+}{e}^{-}\to \varphi {\eta }^{\prime }$ at $\sqrt{s}$ from 2.05 to 3.08 GeV

The process $e^{+}{e}^{-}\to \varphi {\eta }^{\prime }$ has been studied for the first time in detail using data sample collected with the BESIII detector at the BEPCII collider at center of mass energies from 2.05 to 3.08 GeV. A resonance with quantum numbers $J^{PC}=1^{--}$ is observed with mass $M=(2177.5\pm 4.8(\mathrm{stat})\pm 19.5(\mathrm{syst}))\mathrm{MeV}/c^2$ and width $\mathrm{\Gamma }=(149.0\pm 15.6(\mathrm{stat})\pm 8.9(\mathrm{syst}))\mathrm{MeV}$ with a statistical significance larger than $10\sigma$, including systematic uncertainties. If the observed structure is identified with the $\varphi (2170)$, then the ratio of partial width between the $\varphi {\eta }^{\prime }$ by BESIII and $\varphi \eta$ by BABAR is (${\mathcal{B}}_{\varphi \eta }^R{\mathrm{\Gamma }}_{ee}^R)/({\mathcal{B}}_{\varphi {\eta }^{\prime }}^R{\mathrm{\Gamma }}_{ee}^R)=0.23\pm 0.10(\mathrm{stat})\pm 0.18(\mathrm{syst})$, which is smaller than the prediction of the $s\overline{s}g$ hybrid models by several orders of magnitude.

Figure 1

Fit to the $M({\pi }^{+}{\pi }^{-}\gamma )$ mass spectrum at $\sqrt{s}=2.1250\mathrm{GeV}$. The black dots with error bars are data, the solid (red) curve is the total fit result and the dashed (blue) curve is the background shape.

Figure 2

Born cross sections of the $e^{+}{e}^{-}\to \varphi {\eta }^{\prime }$ process. The solid curve (red) shows the fit to the line shape of the Born cross sections. The dots (black) with error bars show data.

Figure 3

The parameters of the $\varphi (2170)$ state obtained from different processes and the resonance in the $e^{+}{e}^{-}\to \varphi {\eta }^{\prime }$ process.