Note on invisible decays of light mesons

Abstract

A search for the invisible decays of $ω$ and $ϕ$ mesons in $J/ψ\to ω(ϕ)η$ 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 ${\cal B}(V\to\barνν)$ with $V$ denoting $ρ,\;ω,\;ϕ$, 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 $J/ψ\to η(η^\prime)\barνν$ processes, and estimate their decay rates. Furthermore, the invisible decays of light pseudoscalar mesons $P$ including $π^0$, $η$, and $η^\prime$ 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 $P\to{\rm invisible}$ decays are dominated by $P\to\barνν\barνν$ processes.