Note on invisible decays of light mesons

Abstract

A search for the invisible decays of $\omega$ and $\varphi$ mesons in $J/\psi \to \omega (\varphi )\eta$ transitions has been performed by the BESIII Collaboration very recently. Inspired by this experimental study, we compute the lowest order contribution to branching ratios of $\mathcal{B}(V\to \bar{\nu }\nu )$ with $V$ denoting $\rho ,\omega ,\varphi$, as the standard model background to these invisible decays. Our predictions are far below the upper bounds given by the BESIII experiment. We also analyze the $J/\psi \to \eta ({\eta }^{\prime })\bar{\nu }\nu$ processes, and estimate their decay rates. Furthermore, the invisible decays of light pseudoscalar mesons $P$ including ${\pi }^0$, $\eta$, and ${\eta }^{\prime }$ are reexamined in the present note. It is shown that, due to the helicity suppression of the two-neutrino final state, the standard model contributions to $P\to \mathrm{invisible}$ decays are dominated by $P\to \bar{\nu }\nu \bar{\nu }\nu$ processes.

Comments: 8 pages, 4 figures, minor changes and references added. To appear in PRD