Development of a Characterization Facility and Analysis Process for LEGEND-200 HPGe Detectors

Neutrinos are tiny, neutral particles with masses much smaller than other particles in the Standard Model. This mass difference could be explained if the neutrino is a Majorana particle, meaning that it is its own antiparticle. We can search for the Majorana nature of the neutrino by searching for a theorized rare decay: neutrinoless double-beta decay (0vBB). Discovering 0vBB would demonstrate that lepton number is not a conserved quantity in a nuclear reaction and could provide us a window into the seconds after the Big Bang which resulted in a matter-dominated universe.

The Large Enriched Germanium Experiment for Neutrinoless double-beta Decay (LEGEND) is an experiment searching for 0vBB in ⁷⁶Ge. The first phase, LEGEND-200 is currently taking commissioning data in Gran Sasso, Italy, and has set a half-life limit goal of 10²⁷ years, two powers of ten longer than current limits. It builds on the success of two previous 0vBB experiments, the MAJORANA DEMONSTRATOR and the GERDA experiment, which achieved the best energy resolution and lowest backgrounds of any 0vBB experiment: two parameters that are extremely important in setting 0vBB half-life limits. LEGEND-200 consists of a 200-kg array of germanium detectors enriched to ~90% in ⁷⁶Ge inside a liquid argon cryostat almost a mile underground. The array is composed of detectors inherited from the MAJORANA DEMONSTRATOR and GERDA as well as 140 kg of new detectors manufactured in a novel geometry developed specifically for LEGEND: the inverted coaxial point contact detector (ICPC). This ICPC geometry allows for an increase in the mass of the detectors without sacrificing their excellent pulse shape discrimination capabilities or energy resolution. Understanding the performance of individual detectors is vital to the success of LEGEND, which requires each detector to go through a rigorous characterization before being installed.

I will give an overview of LEGEND, discuss the process of characterizing these detectors, and talk about what we have learned during the LEGEND-200 detector characterization that will inform the next phase of the experiment.

Topic: Morgan Clark’s Defense

Time: Aug 2, 2023 09:00 AM Eastern Time (US and Canada)

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