Observation of structures in the processes $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{c1}$ and $\ddot{I}‰\ddot{I}{‡}_{c2}$

Abstract

We present measurements of the Born cross sections for the processes $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{c1}$ and $\ddot{I}‰\ddot{I}{‡}_{c2}$ 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 BEPCII storage ring. Assuming the $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{c2}$ signals come from a single resonance, the mass and width are determined to be $M=(4413.6\pm 9.0\pm 0.8)$ MeV/$c^2$ and $\hat{I}“=(110.5\pm 15.0\pm 2.9)$ MeV, respectively, which is consistent with the parameters of the well-established resonance $\ddot{I}ˆ(4415)$. In addition, we also use one single resonance to describe the $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{c1}$ lineshape, and determine the mass and width to be $M=(4544.2\pm 18.7\pm 1.7)$ MeV/$c^2$ and $\hat{I}“=(116.1\pm 33.5\pm 1.7)$ MeV, respectively. The structure of this lineshape, observed for the first time, requires further understanding.

11 pages, 8 figures, with Supplemental Material