Observation of Structures in the Processes $e^{+}{e}^{-}\to \omega {\chi }_{c1}$ and $\omega {\chi }_{c2}$

We present measurements of the Born cross sections for the processes $e^{+}{e}^{-}\to \omega {\chi }_{c1}$ and $\omega {\chi }_{c2}$ at center-of-mass energies $\sqrt{s}$ from 4.308 to 4.951 GeV. The measurements are performed with data samples corresponding to an integrated luminosity of $11.0{\mathrm{fb}}^{-1}$ collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring. Assuming the $e^{+}{e}^{-}\to \omega {\chi }_{c2}$ signals come from a single resonance, the mass and width are determined to be $M=(4413.6\pm 9.0\pm 0.8)\mathrm{MeV}/c^2$ and $\mathrm{\Gamma }=(110.5\pm 15.0\pm 2.9)\mathrm{MeV}$, respectively, which is consistent with the parameters of the well-established resonance $\psi (4415)$. In addition, we also use one single resonance to describe the $e^{+}{e}^{-}\to \omega {\chi }_{c1}$ line shape and determine the mass and width to be $M=(4544.2\pm 18.7\pm 1.7)\mathrm{MeV}/c^2$ and $\mathrm{\Gamma }=(116.1\pm 33.5\pm 1.7)\mathrm{MeV}$, respectively. The structure of this line shape, observed for the first time, requires further understanding.

Figure 1

Distributions of $M({\pi }^{+}{\pi }^{-}{\pi }^0)$ versus $M({\ell }^{+}{\ell }^{-})$ for data at $\sqrt{s}=4.436$ (a) and 4.600 GeV (b) and distributions of $M({\pi }^{+}{\pi }^{-}{\pi }^0)$ versus $M(\gamma J/\psi )$ for data at $\sqrt{s}=4.436$ (c) and 4.600 GeV (d). The blue dashed lines mark the signal regions of $\omega$ and $J/\psi$, and the red dashed lines mark the nominal masses of ${\chi }_{c1,2}$.

Figure 2

Fits to the $M(\gamma J/\psi )$ distributions at $\sqrt{s}=4.436$ (left) and 4.600 GeV (right), respectively.

Figure 3

Fits to the cross sections of $e^{+}{e}^{-}\to \omega {\chi }_{c1}$ (left) and $e^{+}{e}^{-}\to \omega {\chi }_{c2}$ (right) with one single resonance.