Status of the heavy neutrino search using the BeEST experiment Phase-III data

The Beryllium Electron capture in Superconducting Tunnel junctions (BeEST) experiment searches for the signature of sub-MeV heavy neutrino mass eigenstates in the decay of ⁷Be. In the current Phase-III, we utilized a 36-pixel array of superconducting tunnel junction (STJ) cryogenic sensors to precisely measure the nuclear recoil energy of the ⁷Li daughter nucleus resulting from the ⁷Be electron capture decay. We highlight the refined experimental and analytical techniques implemented in Phase-III, and present the current status of the heavy neutrino search using the Phase-III data.