Study of $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{cJ}$ at center-of-mass energies from 4.21 to 4.42 GeV

Abstract

Based on data samples collected with the BESIII detector at the BEPCII collider at 9 center-of-mass energies from 4.21 to 4.42 GeV, we search for the production of $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{cJ}$ ($J$=0, 1, 2). The process $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{c0}$ is observed for the first time, and the Born cross sections at $\sqrt{s}$=4.23 and 4.26 GeV are measured to be $(55.4\pm 6.0\pm 5.9)$ and $(23.7\pm 5.3\pm 3.5)$ pb, respectively, where the first uncertainties are statistical and the second are systematic. The $\ddot{I}‰\ddot{I}{‡}_{c0}$ signals at the other 7 energies and $e^{+}{e}^{-}\to \ddot{I}‰\ddot{I}{‡}_{c1}$ and $\ddot{I}‰\ddot{I}{‡}_{c2}$ signals are not significant, and the upper limits on the cross sections are determined. By examining the $\ddot{I}‰\ddot{I}{‡}_{c0}$ cross section as a function of center-of-mass energy, we find that it is inconsistent with the line shape of the $Y(4260)$ observed in $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$. Assuming the $\ddot{I}‰\ddot{I}{‡}_{c0}$ signals come from a single resonance, we extract mass and width of the resonance to be $(4230\pm 8\pm 6)$ MeV/$c^2$ and $(38\pm 12\pm 2)$ MeV, respectively, and the statistical significance is more than $9\ddot{I}ƒ$.

7 pages, 5 figures