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

TL;DR

This paper explores how hidden extra dimensions and brane-world scenarios could lead to invisible decays of particles like positronium and quarkonia, providing new constraints on the parameters of such models based on recent experimental data.

Contribution

It introduces a model of a two-brane universe in a 5D bulk that predicts invisible decays of particles and derives experimental bounds on brane parameters from current and future experiments.

Findings

Quarkonia provide weaker bounds compared to neutron experiments.

Positronium experiments can compete with neutron experiments depending on brane matter content.

Future positronium experiments could reach sensitivities to test Planck-scale scenarios.

Abstract

While our visible Universe could be a 3-brane, some cosmological scenarios consider 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 quarkonium invisible decays. In the present work, we show how a two-brane Universe allows for such invisible decays. We put this result in the context of the recent experimental data to constrain the brane energy scale $M_B$ (or effective brane thickness $M_B^{-1}$) and the interbrane distance $d$ for a relevant two-brane Universe in a $SO(3,1)$-broken 5D bulk. Quarkonia present poor bounds compared to results deduced from previous passing-through-walls-neutron experiments for which scenarios with $M_B < 2.5 \times 10^{17}$ GeV and $d > 0.5$ fm are excluded. By contrast, positronium experiments can compete with neutron experiments depending on the matter content of each brane. To constrain scenarios up to the Planck scale, positronium experiments in vacuum cavity should be able to reach $\text{Br}(\text{o-Ps} \rightarrow \text{invisible}) \approx 10^{-6}$.