Search for invisible decays of η and η′ in J/ψ→φη and φη′

Using a data sample of 58x10(6) J/psi decays collected with the Beijing Spectrometer II detector at the Beijing Electron Positron Collider, searches for invisible decays of eta and eta(') in J/psi to phi eta and phi eta(') are performed. The phi signals, which are reconstructed in K+K- final states, are used to tag the eta and eta(') decays. No signals are found for the invisible decays of either eta or eta('), and upper limits at the 90% confidence level are determined to be 1.65x10(-3) for the ratio B(eta'-> invisible/B(eta ->gamma gamma) and 6.69x10(-2) for B(eta(')-> invisible)/B(eta(')->gamma gamma). These are the first searches for eta and eta(') decays into invisible final states.