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

MURMUR是一种新的穿墙中子实验，旨在限制在braneworld情景或镜像物质模型的情况下允许的中子隐性中子跃迁。核反应堆可以充当隐藏中子的来源，这样中子就可以穿越隐藏的世界或扇区。隐藏的中子可以传播到核芯之外，并且远远超出生物屏障的范围。但是，隐藏的中子与普通物质之间的相互作用较弱，因此可以在低噪声测量的情况下对其进行检测。在目前的工作中，新颖性在于更好的背景辨别力以及使用大量物质（此处为铅）能够增强隐藏中子再生为可见中子的能力，从而提高探测效率。使用建模和实验研究了这种新设置的输入，\（\ cdot \） CEN，比利时莫尔）。由于在BR2周期02 / 2019A期间进行的测量，已经得出了对中子交换概率p的新限制：\（p <4.0 \乘以10 ^ {-10} \; \ text {at 95} \％\ text {CL} \）。尽管BR2产生隐蔽中子的效率降低了7.4倍，但该限制条件比ILL在2015年ILL上一次通过壁中子实验的界限要好，因此提高了使用再生材料进行此类实验的兴趣。