Description:

Abstract: Neutrinoless double-beta (0𝜈ββ) decay is a hypothetical nuclear decay that, if observed, would show that the neutrino mass term violates conservation of lepton number, as well as B-L. The LEGEND collaboration is searching for 0𝜈ββ decay in 76Ge by deploying an array of enriched germanium detectors inside of a liquid argon detector. In order to maximize its discovery sensitivity, LEGEND uses pulse shape discrimination and liquid argon scintillation light to reduce the external background in the experiment. I will highlight the performance of these techniques, as well as the limit on 0𝜈ββ decay in 76Ge, from the first physics run of the LEGEND-200 experiment. Using the frequentist profile likelihood ratio statistical treatment implemented in a Python package we developed at UW, we place a limit of T_1/2> 5.3e+25 years at a 90% confidence level. I will also cover ongoing R&D for background suppression in the proposed ton-scale LEGEND-1000, which targets a half-life discovery sensitivity >1.0e+28 years. This includes efforts to improve light collection in its liquid argon detector, driven by our recent findings that some silicon photomultipliers exhibit a decreased sensitivity to light at cryogenic temperatures.

Speaker: Sam Borden, University of Washington

Host: Andrew Geraci

Keywords: CFP, physics