Can Elastic Neutrino Scattering Account for the LZ230616 Event?

Abstract

Recently, the LUX-ZEPLIN (LZ) Collaboration reported an isolated nuclear-recoil event at $248\pm 23_\mathrm{stat}\pm 23_\mathrm{syst}~\mathrm{keV_{nr}}$, in a region where the expected background is very small and conventional elastic dark matter (DM)-nucleus scattering cannot readily account for such a localized feature. We investigate whether LZ230616 could instead originate from coherent elastic neutrino-nucleus scattering (CE$ν$NS). We consider neutrino-nucleus interactions within and beyond the Standard Model, together with exotic neutrino fluxes from DM annihilation ($χχ\to ν\barν$) or decay ($χ\to ν\barν$) into neutrino pairs and from primordial black hole (PBH) evaporation. We show that kinematic considerations, the accompanying low energy recoil spectrum, and existing constraints exclude a viable interpretation of LZ230616 in terms of elastic neutrino-nucleus scattering for all scenarios considered.