Surface Backgrounds in the Large Enriched Germanium Experiment for Neutrinoless Double beta decay (LEGEND)

LEGEND searches for lepton number violation using high purity germanium detectors enriched in Ge76. These detectors are operated in a large volume of liquid argon (LAr) that provides cryogenic cooling, a low background environment, as well as an active scintillation veto for background rejection. LEGEND will use a variety of existing detectors from the GERDA and Majorana experiments and newly procured larger inverted coaxial p-type detectors.

Past experience shows that, in LAr, surface backgrounds from alpha (Po210) and beta (K42) decays on the p+ and n+ electrodes are considerable backgrounds before analysis cuts. These backgrounds can be strongly reduced with pulse shape discrimination, which is highly dependent on the detector type, the fabrication procedure of the electrodes, as well as the instrumental noise in the final experimental configuration. Some of the detector types have never been extensively operated in LAr, and their response to LAr-borne surface backgrounds needs to be characterized prior to deployment. In this talk, I will discuss the surface backgrounds in LEGEND, including their pulse shape modeling, mitigation, and characterization plans.