Sub-GeV-scale signatures of hidden braneworlds up to the Planck scale in a $SO(3,1)$-broken bulk

Abstract: Many-brane universes are at the heart of several cosmological scenarios related to physics beyond the Standard Model. It is then a major concern to constrain these approaches. Two-brane Universes involving $SO(3,1)$-broken 5D bulks are among the cosmological models of interest. They also allow considering matter exchange between branes, a possible way to test these scenarios. Neutron disappearance (reappearance) toward (from) the hidden brane is currently tested with high-precision experiments to constrain the coupling constant $g$ between the visible and hidden neutron sectors. When dealing with the sub-GeV-scale quantum dynamics of fermions, any pair of braneworlds can be described by a non-commutative two-sheeted space-time $M_4\times Z_2$ from which $g$ emerges. Nevertheless, the calculation of the formal link between $g$ for a neutron and $SO(3,1)$-broken 5D bulks remains an open problem until now although necessary to constrain these braneworld scenarios. Thanks to a phenomenological model, we derive $g$ - for a neutron - between the two braneworlds endowed with their own copy of the standard model in a $SO(3,1)$-broken 5D bulk. Constraints on interbrane distance and brane energy scale (or brane thickness) are discussed. While brane energy scale below the GUT scale is excluded, energy scale up to the Planck limit allows neutron swapping detection in forthcoming experiments.