The LUX-ZEPLIN (LZ) experiment reported one event that looks like a 248 keV recoil of a xenon nucleus. Instead of dark matter, this paper explores whether neutrinos could be responsible. The authors propose a two-step process: atmospheric neutrinos first produce a nearly monoenergetic neutral particle called N1, and that particle then upscatters inside LZ into a heavier state N2. That second step can give the observed 248 keV signal in xenon.

The paper first shows why a simple neutrino upscattering explanation runs into trouble. Atmospheric neutrinos have a broad energy range, and upscattering directly from neutrinos to heavy neutral states would also produce many events in large neutrino detectors. Detectors such as JUNO, Super‑Kamiokande, IceCube, KamLAND, SNO+ and Borexino have much larger exposures than LZ and use lighter nuclear targets (oxygen, carbon, hydrogen). Scattering on lighter targets generally gives larger nuclear recoils, so the same neutrino-driven process would be easier to see there. The authors estimate that JUNO’s exposure alone is roughly 10^5 times larger than LZ’s, so a conventional neutrino explanation would predict many more events than have been seen.

To avoid that problem, the authors propose a narrow, nearly monoenergetic flux of N1 particles. They show a physical way to get such a narrow flux: a parametric resonance driven by a dark matter background. In simple terms, an oscillating dark matter field can boost the conversion of atmospheric neutrinos into N1 at a specific energy. If that energy sits above the threshold for scattering on xenon but below the thresholds for lighter nuclei, then LZ can see N2-producing events while JUNO and other neutrino experiments remain kinematically blind.

The second step, where N1 upscatters to N2 inside LZ, is modeled as being mediated by a new force carrier. The authors implement this in a model with a gauged U(1)_B symmetry — a force that couples to baryon number (roughly, to protons and neutrons). That interaction can be stronger than the ordinary weak force, which the paper argues is necessary to “lift the neutrino floor” (the background of neutrino events that normally hides very rare processes) and produce about one event in LZ.