The HUNTER Sterile Neutrino Search Experiment

The HUNTER experiment (Heavy Unseen Neutrinos from Total Energy-momentum Reconstruction) is a search for sterile neutrinos with masses in the keV range. The neutrino missing mass will be reconstructed from 131-Cs electron capture decays occurring in a magneto-optically trapped sample.
Reaction-microscope spectrometers will be used to detect all charged decay products with high solid angle efficiency and LYSO scintillators read out by silicon photomultiplier arrays detect x-rays, each with sufficient resolution to reconstruct the neutrino missing mass. The overall design of this W. M. Keck Foundation-funded experiment will be discussed and simulations shown. Upgrades which would improve the mixing angle sensitivity by orders of magnitude will be described.