• Nuclear, Particle, Astroparticle and Cosmology (NUPAC) Seminars

March 10, 2026 2:00 PM
PAIS 3205

Host:

Douglas Fields

Presenter:

Geogia McDowell (UNM)

In the Standard Model, the issues of why neutrinos have mass is one of the few lingering questions that have not yet been answered. One possible answer to this question is that they are Majorana fermions, which can be confirmed by observing neutrinoless double beta decay (0νββ). This would allow neutrinos to have a Majorana mass, which does not originate from the Higgs Mechanism like the Dirac mass does for other fermions. The LEGEND-200 experiment is currently using enriched Ge-76 detectors in conjunction with a liquid argon veto and a Cherenkov veto to search for 0νββ. Due to the rarity of this process, with current limits of τ^0ν_1/2 ≥ 1.9 ∗ 10²⁶ yr at 90% CL, the background level in the region of interest needs to be < 1 counts/(keV kg yr). To aid in the search for 0νββ by way of improving the liquid argon veto to improve background discrimination, the BACoN experiment (and BTB) is developing a more accurate model for liquid argon scintillation de-excitation. This model will include absorption and light diffusion to contaminant excimers that are present in commercial argon. Specifically, the BTB experiment is looking into the effects of 0.01 − 10.0 ppm xenon and nitrogen in liquid argon. The results from BACoN in 2022 showed that it may be possible to increase total light yield by a factor of ≈ 1.92 ± 0.12 and hasten light collection time by increasing the xenon dopant level to 10.0 ppm. If this is confirmed in BTB, the liquid argon veto in the upcoming LEGEND-1000 could be doped with xenon to help reach unprecedented levels of sensitivity.