Observation of $e^{+}{e}^{-}\to {\hat{I}}^{3}X(3872)$ at BESIII

Abstract

With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process $e^{+}{e}^{-}\to {\hat{I}}^{3}X(3872)$ is observed for the first time with a statistical significance of $6.3\ddot{I}ƒ$. The measured mass of the $X(3872)$ is ($3871.9\pm 0.7_{stat.}\pm 0.2_{sys.}$) MeV/$c^2$, in agreement with previous measurements. Measurements of the product of the cross section $\ddot{I}ƒ[e^{+}{e}^{-}\to {\hat{I}}^{3}X(3872)]$ and the branching fraction $\mathcal{B}[X(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ]$ at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process $Y(4260)\to {\hat{I}}^{3}X(3872)$.

Final version published in PRL