Identification and analysis of two-pixel correlated events in BeEST Phase-III Data

The Beryllium Electron Capture in Superconducting Tunnel Junctions (BeEST) experiment measures Lithium-7 atomic recoils from the electron capture decay of Beryllium-7 as a precision search for neutrino-coupled BSM physics. Following the single-pixel demonstration in Phase-II, Phase-III uses a 6x6 grid of superconducting tunnel junction (STJ) detectors, allowing us to analyze spatial correlations and simultaneity between devices. Due to the sensitivity of the detector, there are external events that must be identified and filtered out for the creation of the final Phase-III limit. In this talk, we present a systematic analysis of two-pixel correlated events for their location, time, energy and pulse shape to identify anomalous events and hypothesize their origins. By examining the shape and occurrence of these events, we can understand and reduce systematic uncertainty in our data and contribute to the design of the Phase-IV detector array.