Neutron-Nucleus Scattering Length Measurements using the new Etalon-Based Multilayer Mirror Neutron Interferometer at JPARC*

Precision measurements of neutron-nucleus coherent scattering lengths can provide important information for nuclear few-body physics, nuclear models, and for the quantitative interpretation of neutron scattering experiments. This talk will describe initial applications of a novel etalon-based neutron interferometer recently developed in Japan and successfully tested at the MLF spallation neutron source at JPARC [1]. This neutron interferometer utilizes neutron beam splitting etalons, which are flat glass plates separated by a fixed distance of D=189 μm, parallel to high precision, and coated with neutron multilayer mirrors.  The experiment used the interferometer along with a pulsed neutron beam at J-PARC to measure phase shifts with comparable sensitivity to the well-known Si crystal method. We will describe our measurement in progress of the 131-Xe coherent scattering length, which can determine the two s-wave n-131-Xe scattering lengths in combination with the recently-measured 131-Xe incoherent scattering length [2]

[1] T. Fujiie et al, Phys. Rev. Lett. 132, 023402 (2024).

[2] H. Lu et. al., Phys. Rev. C 109, L011001 (2024).