Searching for keV-mass Sterile Neutrinos with HUNTER*

The HUNTER experiment (Heavy Unseen Neutrinos from Total Energy-momentum Reconstruction) uses missing-mass reconstruction to search for sterile neutrinos with masses in the 20-280 keV range. Radioactive 131-Cs contained in a magneto-optical trap undergoes electron capture decay, giving only low-energy products- a recoil 131-Xe ion, an x-ray, Auger electron(s), and the neutrino. All the charged decay products are detected with high solid angle efficiency and high resolution using Reaction-Ion Microscope spectrometers, and x-rays are detected with position-sensitive thin scintillator arrays. Currently, an experiment to trap the first ever Cs-131 MOT and measure its hyperfine structure is taking place. I will present on the progress of the experiment and future plans of completing a neutrino asymmetry experiment where we will measure the directional asymmetry of the recoil nuclei produced in K-capture on polarized Cs-131 nuclei.