Isotopic signatures and neutron simulations for LEGEND using Geant4 and MCNP

The ton-scale LEGEND project will search for neutrinoless double-beta decay in ⁷⁶Ge. The first phase of the project, LEGEND-200, is in commissioning at the Laboratori Nazionali del Gran Sasso. To assess the suitability of the candidate host sites for the final LEGEND-1000 phase of the project, an estimate of the background induced by muons is necessary. Simulations of these backgrounds, particularly those via muon-induced neutrons, come with large uncertainties. Benchmarking simulations using Geant4 and MCNP are being executed and analyzed to assess systematic uncertainties. A search for key radioactive isotopes produced by neutron captures will be performed in LEGEND-200, which can be used to estimate the in-situ cosmogenic background in LEGEND phases. This talk discusses the MCNP-Geant4 comparisons, identifies isotopic signatures which might be visible in LEGEND-200, and uses simulations to estimate the rate for these signatures.