Probing neutron-hidden neutron transitions with the MURMUR experiment

Coraline Stasser; Guy Terwagne; Jacob Lamblin; Olivier Méplan; Guillaume Pignol; Bernard Coupé; Silva Kalcheva; Steven Van Dyck; Michaël Sarrazin

doi:10.1140/epjc/s10052-021-08829-y

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2021) 81: 17
https://doi.org/10.1140/epjc/s10052-021-08829-y

Regular Article – Experimental Physics

Probing neutron-hidden neutron transitions with the MURMUR experiment

Coraline Stasser¹^a, Guy Terwagne¹, Jacob Lamblin², Olivier Méplan², Guillaume Pignol², Bernard Coupé³, Silva Kalcheva³, Steven Van Dyck³ and Michaël Sarrazin¹^,4

¹ LARN, University of Namur, 61 Rue de Bruxelles, 5000, Namur, Belgium
² LPSC, University of Grenoble-Alpes, CNRS/IN2P3, 53 Avenue des Martyrs, 38026, Grenoble, France
³ SCK.CEN, 2400, Boeretang 200, Mol, Belgium
⁴ Institut UTINAM, CNRS/INSU, UMR 6213, University of Bourgogne-Franche-Comté, 16 Route de Gray, 25030, Besançon Cedex, France

^a coraline.stasser@unamur.be

Received: 17 July 2020
Accepted: 1 January 2021
Published online: 12 January 2021

Abstract

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 $\cdot$ $\cdot$ 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: $p < 4.0 \times 10^{- 10} at 95 % CL$ $p<4.0\times 10^{-10} \; \text {at 95}\%\text { CL}$ . 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.

© The Author(s) 2021

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