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While our visible Universe could be a 3-brane, some cosmological scenariosconsider that other 3-branes could be hidden in the extra-dimensional bulk.Matter disappearance toward a hidden brane is mainly discussed for neutron -both theoretically and experimentally - but other particles are poorly studied.Recent experimental results offer new constraints on positronium or quarkoniuminvisible decays. In the present work, we show how a two-brane Universe allowsfor such invisible decays. We put this result in the context of the recentexperimental data to constrain the brane energy scale $M_B$ (or effective branethickness $M_B^{-1}$) and the interbrane distance $d$ for a relevant two-braneUniverse in a $SO(3,1)$-broken 5D bulk. Quarkonia present poor bounds comparedto results deduced from previous passing-through-walls-neutron experiments forwhich scenarios with $M_B < 2.5 \times 10^{17}$ GeV and $d > 0.5$ fm areexcluded. By contrast, positronium experiments can compete with neutronexperiments depending on the matter content of each brane. To constrainscenarios up to the Planck scale, positronium experiments in vacuum cavityshould be able to reach $\text{Br}(\text{o-Ps} \rightarrow \text{invisible})\approx 10^{-6}$.

Bounds on ortho-positronium and $J/\psi$-$\Upsilon$ quarkonia invisible decays and constraints on hidden braneworlds in a $SO(3,1)$-broken 5D bulk