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

We present searches for light dark matter (DM) with masses 3-9 GeV/c^{2} in the presence of coherent elastic neutrino-nucleus scattering (CEνNS) from ^{8}B solar neutrinos with the LUX-ZEPLIN experiment. This analysis uses a 5.7 tonne-yr 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 CEνNS 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 CEνNS events, corresponding to a 4.5σ statistical significance. This is the most significant evidence of ^{8}B CEνNS interactions and is enabled by robust background modeling and mitigation techniques. This demonstrates LZ's ability to detect rare signals at keV-scale energies.