Probing neutron-hidden neutron transitions with the MURMUR experiment

• Published in: The European physical journal. C, Particles and fields Vol. 81; no. 1; pp. 1 - 14
• Main Authors: Stasser, Coraline, Terwagne, Guy, Lamblin, Jacob, Méplan, Olivier, Pignol, Guillaume, Coupé, Bernard, Kalcheva, Silva, Van Dyck, Steven, Sarrazin, Michaël
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2021; Springer; Springer Nature B.V; Springer Verlag (Germany); SpringerOpen
• Subjects: Astronomy; Astrophysics and Cosmology; Context; Elementary Particles; Experiments; Hadrons; Heavy Ions; Instrumentation and Detectors; Investigations; Measurement Science and Instrumentation; Neutrons; Nuclear Energy; Nuclear Experiment; Nuclear facilities; Nuclear Physics; Nuclear reactors; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regeneration; Regular Article – Experimental Physics; Shielding; String Theory; weak interaction; experimental results; membrane model; regeneration; matter: mirror; background; noise: low; shielding; nucleus; nucleon: transition; constraint; nuclear reactor
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-021-08829-y

MURMUR is a new passing-through-walls neutron experiment designed to constrain neutron-hidden neutron transitions allowed in the context of braneworld scenarios or mirror matter models. A nuclear reactor can act as a source of hidden neutrons, such that neutrons travel through a hidden world or sector. Hidden neutrons can propagate out of the nuclear core and far beyond the biological shielding. However, hidden neutrons can weakly interact with usual matter, making possible for their detection in the context of low-noise measurements. In the present work, the novelty rests on a better background discrimination and the use of a mass of a material – here lead – able to enhance regeneration of hidden neutrons into visible ones to improve detection. The input of this new setup is studied using both modelizations and experiments, thanks to tests currently performed with the experiment at the BR2 research nuclear reactor (SCK
·
CEN, Mol, Belgium). A new limit on the neutron swapping probability
p
has been derived thanks to the measurements taken during the BR2 Cycle 02/2019A:
p
<
4.0
×
10
-
10
at 95
%
CL
. This constraint is better than the bound from the previous passing-through-wall neutron experiment made at ILL in 2015, despite BR2 is less efficient to generate hidden neutrons by a factor of 7.4, thus raising the interest of such experiment using regenerating materials.