Neutron-Induced Background for Double-Beta Decay Experiments

Measurements of neutron excitation in lead, copper, and germanium at TUNL and LANSCE in search of specific excited state decays are important in understanding neutron-induced background in some double-beta decay experiments. The nucleus, in a highly excited state, decays via a $\gamma$ cascade to the ground state and produces background that may contribute to the next generation of double-beta decay experiments designed to reach the sensitivity of the atmospheric neutrino mass scale (45 meV). Measuring and understanding the high-energy neutron excitations of the shielding and detector materials for neutrinoless double-beta decay experiments are crucial for interpreting results and establishing shielding requirements. Determination of partial $\gamma$-ray cross sections provides useful data for benchmarking Monte Carlo simulation of background events. Some specific excited state transitions, such as the $\frac{5}{2}^+$ to $\frac{5}{2}^-$ decay in $^{207}$Pb and the 1$^-$ to 1$^+$ decay in $^{206}$Pb, are potentially troublesome for Ge-based double-beta decay experiments.