New Limits on Mirror Neutron Oscillations*

It was proposed that the oscillation of neutrons into mirror neutrons, a theoretical dark, sterile counterpart to neutrons, could account for the anomalous discrepancy in beam and bottle measurements of the neutron lifetime. The oscillation is amplified when resonance occurs from the compensation of the magnetic field with the mass difference between neutrons and mirror neutrons resulting in a Landau-Zener transition. A new search at the Oak Ridge National Laboratory was performed to indirectly detect mirror neutrons via the disappearance and regeneration of neutrons in a cold neutron beam with a large, spatially varying magnetic field. Simulations were performed to determine the probability of detecting regenerated neutrons for a wide parameter space of interest and were compared with experimentally determined neutron detection rates. We will present the results of the recent experiment with new detection limits and parameter exclusions and implications for neutron lifetime measurements.