Analysis of MAGNETO-ν data and a preliminary limit to keV-sterile neutrino mixing

Sterile neutrino in the keV scale is a potential dark matter candidate. A non-zero mixing of sterile neutrino with the electron-antineutrino can cause a discontinuity in the beta spectrum. Thus, a precise beta spectrum measurement in the keV region is a test of presence of the keV-scale sterile neutrino. The MAGNETO-ν experiment measures the total beta decay spectrum of ²⁴¹Pu, including the daughter nuclear recoils, with high resolution magnetic microcalorimeters (MMCs). The ²⁴¹Pu sources are fully embedded into the detector to achieve total energy absorption with ~100% detection efficiency. This approach has allowed us to achieve O(0.01) sensitivity for the sterile neutrino mixing |U_e4|² in the 10 keV mass region with only 24 hours of measurement and a single detector with a 1 Bq ²⁴¹Pu source. We are presenting the experimental setup, the data processing, and the preliminary analysis for sterile neutrino probing with current dataset taken for 10 days with a 100 Bq source.