Search for $K^0_S$ invisible decays

TL;DR

This study searches for invisible decays of the $K^0_S$ meson using a large dataset of $J/\psi$ events, setting the first experimental upper limit on such decays and finding no significant signal.

Contribution

First experimental search for $K^0_S$ invisible decays, establishing an upper limit on the branching fraction using $J/\psi$ decay data.

Findings

No significant $K^0_S$ invisible decay signal observed.

Upper limit on branching fraction set at 8.4×10^{-4} at 90% confidence level.

First experimental constraint on $K^0_S$ invisible decays.

Abstract

Based on $(1.0087\pm0.0044)\times10^{10}$ $J/\psi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ storage ring, we search for $K_{S}^{0}$ invisible decays via the $J/\psi \to \phi K_{S}^{0} K_{S}^{0}$ process. No significant signal is observed, and the upper limit of the branching fraction of these invisible decays is set at 8.4 $\times$ $10^{-4}$ at the 90\% confidence level. This is the first experimental search for $K^0_S$ invisible decays.