Measurement of the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$ cross section in the vicinity of 3.872 GeV

Abstract

We report a measurement of the cross section for the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$ around the $X(3872)$ mass in search for the direct formation of $e^{+}{e}^{-}\to X(3872)$ through the two-photon fusion process. No enhancement of the cross section is observed at the $X(3872)$ peak and an upper limit on the product of electronic width and branching fraction of $X(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$ is determined to be $\hat{I}{“}_{ee}\times \mathcal{B}(X(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ)<7.5\times 10^{-3}\text{eV}$ at $90\%$ confidence level under an assumption of total width of $1.19\pm 0.21$ MeV. This is an improvement of a factor of about $17$ compared to the previous limit. Furthermore, using the latest result of $\mathcal{B}(X(3872)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ)$, an upper limit on the electronic width $\hat{I}{“}_{ee}$ of $X(3872)$ is obtained to be $<0.32\text{eV}$ at the $90\%$ confidence level.