Neutron inelastic scattering in natural Cu as a background in neutrinoless double-beta decay experiments

Abstract

Experiments designed to study rare processes, such as neutrinoless double beta decay ($0νββ$), are crucial tests for physics beyond the standard model. These experiments rely on reducing the intrinsic radioactive background to unprecedented levels, while adequately shielding the detectors from external sources of radioactivity. An understanding of the potential for neutron excitation of the shielding and detector materials is important for obtaining this level of sensitivity. Using the broad-spectrum neutron beam at LANSCE, we have measured inelastic neutron scattering on $^{nat}$Cu. The goal of this work is focused on understanding the background rates from neutrons interacting in these materials in regions around the Q-values of many candidate $0νββ$ decay isotopes, as well as providing data for benchmarking Monte Carlo simulations of background events. Results: We extracted the level cross sections from the $γ$ production cross section for 46 energy levels in $^{nat}$Cu . These level cross sections were compared with the available experimental data, as well as the ENDF/B-VII evaluation for discrete levels. We also examined the potential implications of our measurements on $0νββ$ measurements and found that many of the commonly studied $0νββ$ isotopes had Q-values below the cutoff for ENDF/B-VII evaluated discrete levels in either Cu nucleus.