Search for passing-through-walls neutrons constrains hidden braneworlds

TL;DR

This study conducted an experiment to detect neutron swapping between our universe and hidden braneworlds, significantly tightening constraints on such phenomena and providing new limits on the separation of parallel branes in higher-dimensional theories.

Contribution

The paper presents the first experimental search for neutron swapping between braneworlds, setting a new upper limit on the probability of such events and constraining the parameters of braneworld models.

Findings

Limit on neutron swapping probability: p < 4.6×10^{-10} at 95% C.L.

Braneworld separation d > 87 in Planck length units.

Experimental method improves previous bounds by four orders of magnitude.

Abstract

In many theoretical frameworks our visible world is a $3$-brane, embedded in a multidimensional bulk, possibly coexisting with hidden braneworlds. Some works have also shown that matter swapping between braneworlds can occur. Here we report the results of an experiment - at the Institut Laue-Langevin (Grenoble, France) - designed to detect thermal neutron swapping to and from another braneworld, thus constraining the probability $p^2$ of such an event. The limit, $p<4.6\times 10^{-10}$ at $95 \%$ C.L., is $4$ orders of magnitude better than the previous bound based on the disappearance of stored ultracold neutrons. In the simplest braneworld scenario, for two parallel Planck-scale branes separated by a distance $d$, we conclude that $d>87$ in Planck length units.