Current status of multilayer neutron interferometry with gaseous samples at J-PARC

Several few-body nuclear models, such as the Argonne v ₁₈ potential including three-nucleon forces and chiral effective field theories, predict the coherent scattering length (b _c) for light nuclei. Reliable measurements of b _c therefore provide important tests of these models. We have developed a measurement system for determining b _c of gaseous samples using a multilayer-type neutron interferometer at J-PARC, and successfully observed the phase shifts of ³He and ⁴He gases. From the observed phase shifts, we obtained for ³He b _c = 3.99 ± 0.23 (stat.) ± 0.66 (sys.) fm and for ⁴He b _c = 2.95 ± 0.11 (stat.) ± 0.67 (sys.) fm (stat. and sys. denote statistical uncertainty and systematic uncertainty, respectively). To achieve higher precision, we are currently upgrading the experimental setup.