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

October 20, 2026 2:00 PM

Host:

Dinesh Loomba

Presenter:

Ralph Massarczyk (LANL)

Searches for neutrinoless double beta decay and dark matter operate deep underground, where the sensitivity of next-generation experiments depends on background rates of order one count per ton and year. While the detector sits underground, cosmic rays no longer produce new background. Its materials, however, are refined, processed and shipped on the surface, often across continents, and during that time cosmic-ray neutrons produce long-lived radioisotopes within them. The resulting background depends on the exposure history, on reaction cross sections that are poorly constrained above 100 MeV, and on transport choices such as shielded ocean freight versus air.

Current practice relies on logged histories and model calculations, so the exposure is never actually measured. This talk discusses whether it can be measured: how a material's own activation can serve as a record of where it has been, what is needed to make that record quantitative, and how well it holds up outside the laboratory. The discussion follows a combined beam and field study, from the neutron beam at LANSCE to low-background counting at SURF.