Evidence for $X(3872)\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ produced in single-tag two-photon interactions

Abstract

We report the first evidence for $X(3872)$ production in two-photon interactions by tagging either the electron or the position in the final state, exploring the highly virtual photon region. The search is performed in $e^{+}{e}^{-}\to e^{+}{e}^{-}J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^{-}$, using 825 fb${}^{-1}$ of data collected by the Belle detector operated at the KEKB $e^{+}{e}^{-}$ collider. We observe three $X(3872)$ candidates with an expected background of $0.11\pm 0.10$ events, with a significance of 3.2$\ddot{I}ƒ$. We obtain an estimated value for $\tilde{\hat{I}}{“}_{{\hat{I}}^3{\hat{I}}^3}\mathcal{B}(X(3872)\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^{-}$) assuming the $Q^2$ dependence predicted by a $c\bar{c}$ meson model, where $-Q^2$ is the invariant mass-squared of the virtual photon. No $X(3915)\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ candidates are found.

To be published in Physical Review Letters