Searches for Light Dark Matter and Evidence of Coherent Elastic Neutrino-Nucleus Scattering of Solar Neutrinos with the LUX-ZEPLIN (LZ) Experiment

TL;DR

This paper reports on searches for light dark matter and provides the most significant evidence to date for coherent elastic neutrino-nucleus scattering of solar neutrinos using the LUX-ZEPLIN experiment, setting new limits and demonstrating detection capabilities.

Contribution

It presents the first evidence of $^{8}$B CE$ u$NS interactions and sets world-leading limits on light dark matter interactions with the LZ detector.

Findings

No dark matter signal detected in the 1-6 keV range.

Most significant evidence ($4.5\sigma$) for $^{8}$B CE$ u$NS interactions.

LZ demonstrates capability to detect rare keV-scale signals.

Abstract

We present searches for light dark matter (DM) with masses 3-9 GeV/$c^2$ in the presence of coherent elastic neutrino-nucleus scattering (CE$\nu$NS) from $^{8}$B solar neutrinos with the LUX-ZEPLIN experiment. This analysis uses a 5.7 tonne-year exposure with data collected between March 2023 and April 2025. In an energy range spanning 1-6 keV, we report no significant excess of events attributable to dark matter nuclear recoils, but we observe a significant signal from $^{8}$B CE$\nu$NS interactions that is consistent with expectation. We set world-leading limits on spin-independent and spin-dependent-neutron DM-nucleon interactions for masses down to 5 GeV/$c^2$. In the no-dark-matter scenario, we observe a signal consistent with $^{8}$B CE$\nu$NS events, corresponding to a $4.5\sigma$ statistical significance. This is the most significant evidence of $^{8}$B CE$\nu$NS interactions and is enabled by robust background modeling and mitigation techniques. This demonstrates LZ's ability to detect rare signals at keV-scale energies.