Scientists propose a new dark matter (DM) interaction model to explain a high-energy nuclear recoil event detected by the LUX-ZEPLIN (LZ) experiment. The hypothesis suggests that an incoming DM particle annihilates a bound neutron within a nucleus, transforming it into an invisible scalar. This process leaves a recoiling daughter nucleus, whose recoil energy, in the zero-velocity limit, generates a line spectrum broadened by halo velocities.

The study identifies parameter regions for DM masses of 5 and 50 GeV that could account for the observed event near 248 keV, without producing events at lower energies. This specificity is crucial for matching LZ observations, which search for direct interactions of dark matter with nuclei. The researchers also examined collider constraints in an illustrative ultraviolet completion and re-evaluated Borexino data to limit accompanying nuclear de-excitation signals.

This "DM-induced neutron disappearance" mechanism offers a novel framework for interpreting localized nuclear recoil excesses in future direct-detection experiments. It could be key to understanding the nature of dark matter if similar events are confirmed and other explanations ruled out. The proposal opens new avenues for DM searches, focusing not only on elastic scattering but also on more complex annihilation processes.