Observation of $e^{+}{e}^{-}\to \ddot{I}{€}^0\ddot{I}{€}^0\ddot{I}{ˆ}_2(3823)$

Abstract

Using a data sample corresponding to an integrated luminosity of 11.3 $\mathrm{f}{\mathrm{b}}^{-1}$ collected at center-of-mass energies from $4.23$ to $4.70$~GeV with the BESIII detector, we observe the process $e^{+}{e}^{-}\to \ddot{I}{€}^0\ddot{I}{€}^0\ddot{I}{ˆ}_2(3823)$ for the first time with a statistical significance of $6.0\ddot{I}ƒ$. The ratio of average cross sections for $e^{+}{e}^{-}\to \ddot{I}{€}^0\ddot{I}{€}^0\ddot{I}{ˆ}_2(3823)$ over $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{ˆ}_2(3823)$ is determined to be $\mathcal{R}=\frac{\ddot{I}ƒ[e^{+}{e}^{-}\to \ddot{I}{€}^0\ddot{I}{€}^0\ddot{I}{ˆ}_2(3823)]}{\ddot{I}ƒ[e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{ˆ}_2(3823)]}=0.57\pm 0.14\pm 0.05$, which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the $\ddot{I}{ˆ}_2(3823)$ is measured to be $M[\ddot{I}{ˆ}_2(3823)]=3824.5\pm 2.4\pm 1.0$~MeV/$c^2$. Due to the limited statistics, the intrinsic width of the $\ddot{I}{ˆ}_2(3823)$ is measured as an upper limit of $18.8$~MeV at $90\%$ confidence level.

16 pages, 1 figure