Search for invisible decays of $\ddot{I}‰$ and $\ddot{I}•$ with $J/\ddot{I}ˆ$ data at BESIII

Abstract

Using a data sample of $(1310.6\pm 7.0)\times 10^6$ $J/\ddot{I}ˆ$ events collected with the BESIII detector operating at the BEPCII collider, we perform the first experimental search for invisible decays of a light vector meson ($V=\ddot{I}‰,\ddot{I}•$) via $J/\ddot{I}ˆ\to V\hat{I}\cdot$ decays. The decay of $\hat{I}\cdot \to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ is utilized to tag the $V$ meson decaying into the invisible final state. No evidence for a significant invisible signal is observed, and the upper limits on the ratio of branching fractions at the 90\% confidence level are determined to be $\frac{\mathcal{B}(\ddot{I}‰\to \mathrm{invisible})}{\mathcal{B}(\ddot{I}‰\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)}<8.1\times 10^{-5}$ and $\frac{\mathcal{B}(\ddot{I}•\to \mathrm{invisible})}{\mathcal{B}(\ddot{I}•\to K^{+}{K}^{-})}<3.4\times 10^{-4}$. By using the world average values of $\mathcal{B}(\ddot{I}‰\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)$ and $\mathcal{B}(\ddot{I}•\to K^{+}{K}^{-})$, the upper limits on the decay branching fractions at the $90\%$ confidence level are set as $\mathcal{B}(\ddot{I}‰\to \mathrm{invisible})<7.3\times 10^{-5}$ and $\mathcal{B}(\ddot{I}•\to \mathrm{invisible})<1.7\times 10^{-4}$, respectively.

10 pages, 6 figures